4626 4630.output

* GB785033 (A)
Description: GB785033 (A) ? 1957-10-23
Improvements in or relating to electric control devices for furnaces
Description of GB785033 (A)
PATENT SPECIFICATION
Date of filing Complete Specification July 18, 1955.
Application Date July 16, 1954.
785,035 No 20805/54.
Complete Specification Published Oct 23, 1957.
Index at Acceptance:-Classes 40 ( 6), R 3 (A 1: Bil); and 75 ( 1), TE,
TG 22, TJ.
International Classification: -F 23 d, f H 03 f.
COMPLETE SPECIFICATION
Improvements in or relating to Electric Control Devices for Furnaces
We, ORMISTON MEIKLE, British Subject, of "High Trees ", 64, Butts
Green Road, Hornchurch, in the County of Essex, LEONARD PERCIVAL
FIANDER, British Subject, of 25, Zealand Avenue, Harmondsworth, West
Drayton, in the County of Middlesex, and DOUGLAS JA Ci K GODFREE
ANDREWS, British Subject, of 56, Biggin 1 ill, Upper Norwood, London,
S E 19, do hereby declare the invention, for which we pray that a
patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement: -
This invention relates to an electric control device for an
oil-burning or gas burning furnace, which can be employed in
conjunction with thermostats or other devices responsive to conditions
in the furnace to control the normal operation of the furnace and also
to provide adequate safeguards in the event of failure of the furnace
to operate satisfactorily.
The invention has for its primary object to provide an improved
electric control device for this purpose of simple and robust
construction which will operate efficiently and reliably to effect the
desired control.
The control device according to the present invention comprises two

electric relays respectively energised from the anode circuits of two
electronic discharge devices each having a control grid, a
capacitance-resistance timing circuit connected to the control grid of
each electronic device, and means whereby each relay controls the
application of potential to the timing circuit associated with the
electronic device energising the other relay, the arrangement being
such that the time delay controlled by the first relay and preceding
operation of the second relay is initiated by the energisation of such
first relay whilst the time delay controlled by the second relay and
preceding operation of the first relay is initiated by the
deenergisation of such second relay.
The device is preferably such that, when it is required (for example
as the result of the lPrice 3 s 6 d l operation of a thermostat) to
bring the furnace burner into operation, the first relay is energised
(provided that the time delay controlled by the second relay has
meanwhile expired) and acts on operation to energise the fuel-supply
means for the burner Preferably, such second relay, on operation after
the time delay initiated by the first relay, acts to deenergise the
first relay unless meanwhile a flame-responsive device operative when
the burner has satisfactorily ignited has completed a holding circuit
for the first relay.
Conveniently, if the said holding circuit has been completed, the two
relays remain energised until the furnace temperature has been raised
by the burner to the desired level, whereupon a thermostat operates to
deenergise both relays The arrangement is preferably such that, after
deenergisation of the first relay by the second relay in the event of
failure of the flame-responsive device to complete its holding
circuit, the second relay remains energised and thereby locks the
control device against further operation until a manually-controlled
switch is operated to deenergise the second relay.
Whilst the burner may be ignited in other ways, it is often
convenient, especially in an oil-burning furnace, to control such
ignition electrically over a circuit which is completed on
energisation of the first relay, such circuit being broken on
energisation of the second relay.
The electronic device may take various forms but in one convenient
arrangement are combined together in a single envelope in the form of
a double triode.
A preferred arrangement of electronic control device according to the
invention is illustrated diagrammatically in the accompanying drawing
and will be described, for convenience with reference to its use in
controlling an oilburning furnace, in which the fuel supply to the
burner and also a fan for providing the necessary draught are
controlled by an electric motor A (hereinafter termed "the burner

motor ") and the fuel-air mixture is ignited by means of an electric
spark controlled through an ignition transformer B, the furnace also
being provided with a flame-responsive device C for determining
whether the burner has satisfactorily ignited Such device may consist,
for example, of a thermostat directly exposed to the heat of the flame
or of a photocell exposed to the light from the flame or of a contact
device responsive to the electrical conductivity of the flame In
addition, there will usually be a number of devices responsive to the
temperature and other conditions in the furnace or in chambers or
vessels or passages directly or indirectly heated by the furnace.
Such devices indicated at D may include, for instance, furnace
thermostats, flue thermostats, hot-water thermostats (in the case of
boilers or water-heaters), steam pressure responsive devices ( in the
case of steam generators), room thermostats (when the furnace is used
for heating a building) and so on, the term " controlling thermostat "
being used in the following description as a collective term
representative of such devices.
The electric control device itself, in this arrangement, comprises a
double triede E, consisting of two triodes F F' F' and G G' G 2 in a
single envelope with a common heater E' for the two cathodes, two
timing circuits H H' and J J', and two electromagnetic relays K and L.
Each timing circuit consists of a capacitance H or J in parallel with
a resistance H' or Jl, the two timing circuits respectively being
series connected in the grid circuits of the two triodes The second
timing circuit J J 1, associated with the second triode G G' G, has
its resistance J' variable so that its time delay can be adjusted, for
example from one to sixty seconds, to suit requirements, whilst the
first timing circuit H H' can have a fixed time delay, of say two
minutes.
The first relay K is series-connected in the anode circuit of the
first triode F F' F 2, and has a smoothing capacitance K' connected
across it, and the second relay L also provided with a smoothing
capacitance L' is similarly energised from the anode circuit of the
second triode G G' G 2.
The first relay K controls five contacts, three of which I KA; K' are
normally open when relay is deenergised, whilst the other two K 2 K'
are each in the form of change-over contacts The terms " normally open
" and " normally closed " are used herein with reference to a relay
contact or contacts to indicate the state of such contact or contacts
when the relay is deenergised, for example when the burner is out of
action.
One of these change-over contacts K 2 controls the application of
potential to the second timing circuit J I', such circuit being
connected when the relay K is deenergised to the positive pole of a

supply source M through a resistance J, and when the relay K is
energised to the negative pole of such source, such negative pole also
being directly connected to the cathodes F G 2 of the two triodes.
The other change-over contact K' in the 70 de-energised position
controls the energising circuit to a lockout lamp N and alarm device
(not shown), and in the energised position controls the energising
circuit to a burner motor A The change-over arm of this contact K' is
75 connected to a positive busbar M' which is energised from the
positive pole of the source M, when the first relay is energised,
through one of the three normally open contacts K'.
Another of the normally-open contacts K' of 80 the first relay K is
connected between the positive pole of the source M and the " cold "
contact C' of the flame-responsive device C, and serves in normal
operating conditions, as will be described later, to provide a
temporary 85 holding circuit for the first relay K under the control
of the second relay L, before a main holding circuit for the relay K
becomes operative.
The remaining normally-open contact K of 90 the first relay K is
connected between the "hot" contact C' of the flame-responsive device
C and the free end of the coil of the first relay K (that is the end
remote from the anode F of the first triode), and serves as a 95
holding contact for completing the main holding circuit for the first
relay K in normal operating conditions.
The supply to the flame-responsive device C for energisation of its
hot and cold contact C' i ? C 2 in accordance with the operation of
such device is taken from the positive pole of the source M through
the controlling thermostat D.
The second relay L has one normally closed 105 contact L' and two
change-over contacts LW La.
The normally-closed contact L controls the energising circuit from the
positive busbar M 1 to the ignition transformer B 110 One of the
change-over contacts L 2 controls the application of potential to the
first timing circuit H H', such circuit being connected when the
second relay L is deenergised to the negative pole of the source M and
when 115 the relay is energised to the positive pole of the source M
through a resistance H The other change-over contact L' connects the
cold contact C 2 of the flame-responsive device C when the second
relay L is deener 120 gised to the free end of the first relay coil K,
and w her the second relay L is energised to the free end of the
second relay L and to the positive busbar M' This contact L' is so
arranged that on energisation of the relay L it 125 does not open its
normally-closed contact until after it has closed its normally-open
contact.
The manner in which the control device controls the normal operation

of the furnace will first be described, starting from the con 130 -2
785,033 the grid G' is at a negative potential below the cut-off value
of the valve G G' G' to an extent determined by the building up of
charge on the capacitor J during the period when grid current was
flowing At the end of the time 70 delay, the capacitance J will have
become sufficiently discharged to increase the grid potential to a
value above the cut-off potential which will permit the second triode
G G' G' to supply sufficient anode current to energise the 75 second
relay L, causing such relay to operate.
This time delay is set in accordance with the furnace characteristics
to provide adequate time for the burner to ignite satisfactorily but
insufficient time for risk of danger in the event 80 of failure to
ignite.
It will first be assumed that the burner does ignite satisfactorily
and that the flame-responsive device C moves over to its hot-contact
C, thus making the main holding circuit through 85 contacts K' for the
first relay K, within the chosen time delay At the end of the time
delay, the second relay L operates and breaks at one contact of the
change-over contact L' the temporary holding circuit for the first
relay 90 K (which however remains energised because its main holding
circuit has meanwhile been completed), the second relay L also making
its own holding circuit through the other contact of the change-over
contact L' The energising 95 circuit to the ignition transformer B is
broken at contact Lo, since there is no further need for ignition,
once the burner flame is properly established At the same time, the
first timing circuit H H' is transferred at contact L' from 100 the
negative pole of the source M to the positive pole and thus at once
charges up the capacitance H and puts a positive potential on the grid
F' sufficient to cause the valve F F' F 2 to pass grid current The
corresponding 105 reduction in anode current however does not cause
decnergisation of the first relay K, although if the first relay had
been deenergised it would prevent the reenergisation thereof owing to
the difference between the holding 110 current and the lifting current
of the relay.
The two relays K L are therefore both energised, and this condition
continues and keeps the burner in operation, thus gradually heating
the furnace up again When the critical maxi 115 mum temperature is
reached, the controlling thermostat D breaks the connection from the
positive pole of the source M to the flameresponsive device C, and
thus breaks the holding circuit for the first relay K which immedi 120
ately moves to its deenergised position This breaks at contact K' the
circuit to the burner motor A and cuts the burner out of action and
also at contact K' deenergises the positive busbar M' and breaks the
circuit to the second 125 relay L, thus deenergising that relay At the

same time, the second timing circuit J pl is transferred at contact K'
from the negative pole to the positive pole of the source, thus
restoring the valve G G' G 2 to the condition 130 dition (shown in the
drawing) in which the burner is out of action and the furnace is
gradually cooling after previous operation of the burner At this stage
both relays K L are deenergised, and the second timing circut J J' is
connected to the positive pole of the source M so that the positive
potential on the grid of the second triode G G' G' ensures that such
valve is not in condition to supply anode current sufficient for the
actuation of the second relay L In these conditions, the capacitor J
becomes charged by the grid current which flows in the timing circuit
J J', the grid side of the condenser J being at a positive potential
somewhat less than that of the side of such condenser J remote from
the grid to an extent determined by the potential difference developed
across the resistance I 1 of the timing circuit J J' The first timing
circuit H H' is, however, connected to the negative pole of the source
M and, provided that it has been so connected long enough to cover the
two minute time delay required for discharge of its condenser H, the
grid F' of the first triode F F' F' is at such a potential that the
valve is in condition to supply sufficient anode current for the
immediate actuation of the first relay K as soon as its energising
circuit is completed.
When the furnace cools to the critical minimum temperature at which
the controlling thermostat D operates, such operation will supply
current from the positive pole of the source M through the
flame-responsive device C to the cold contact C 2 thereof and thence
through the change-over contact L' on the second relay L to the free
end of the first relay K, thus completing the energising circuit of
the first relay K and causing such relay to operate This will prepare
through contact K' the mhain holding circuit for this relay to the hot
contact C' of the flame-responsive device C, and also complete through
contact K' the temporary holding circuit for the relay K so as to keep
the relay energised when the flame-responsive device C breaks the
connection to its cold contact C 2 The positive busbar M' will be
energised through contact K' from the positive pole of the source M 1,
thus preparing the energising circuit to the second relay L and
completing through contacts K' K' the energising circuits to the
burner motor A and through contact K' to the ignition transformer B,
thus supplying fuel to the burner and operating the ignition device
therefor At the same time, the second timing device J I' will be
disconnected at contact K 2 from the positive pole of the source M and
connected to the negative pole, thus immediately bringing the side of
the capacitance J remote from the grid G' of the valve G G' G' to zero
potential and initiating the time delay by allowing the charge on the

capacitance to leak away slowly through the resistance J' It should be
mentioned that at the beginning of such time delay 785,033 785,033 in
which it cannot permit reactuation of the relay L.
The deenergisation of the second relay L prepares at contact L 3 the
energising circuit for the first relay K and also at contact L' the
energising circuit for the ignition transformer B, neither of these
circuits however at this stage being connected to the positive pole of
the source M At the same time, the first timing circuit H H' is
transferred at contact L 2 from the positive pole to the negative pole
of the source M, thus permitting the capacitance H to discharge slowly
and initiating the two-minute time delay This brings the control
device back into condition for restarting when the furnace has cooled
down sufficiently for operation of the controlling thermostat D,
provided that the two-minute time delay has meanwhile elapsed It
should again be mentioned that at the beginning of the two-minute time
delay the grid F' of the triode F F' F 2 is at a negative potential
below the cut-off value to an extent determined by the charge built up
on the capacitance H during the period when grid current was flowing
in the timing circuit H He.
If now after starting or restarting, the burner fails to ignite
satisfactorily, or if the burner does ignite but the flame-responsive
device C fails to move over to its hot contact Cl, the main holding
circuit for the first relay K through contact IK' will not be
completed before expiration of the time delay of the second timing
circuit J J In such case, the second relay L will be energised at the
end of the time delay of the second timing circuit I J' and will
immediately break at contact L' the energising circuit for the first
relay K, thus deenergising that relay This at once breaks the circuit
to the burner motor A and cuts off the fuel supply to the burner,
there-by preventing the accumulation of the dangerous quantity of the
unignited fuel-air mixture in the furnace At the same time the first
relay K breaks the direct connection from the positive pole of the
source M to the positive busbar Ml, but an alternative connection to
this busbar remains completed through the cold contact C 2 of the
flame-responsive device C and through the holding contact L of the
second relay L The second timing device J 1 l is also transferred back
to the positive pole of the source M, the positive potential on the
grid G' of the valve G G' G 2 being such as to allow the valve to
permit sufficient anode current to flow to leave the second relay L
actuated but insufficient to cause re-actuation thereof if such relay
is deenergised The deenergisation of the first relay K also completes
the connection from the positive busbar Ml to the lock-out lamp N and
alarm, so that warning is given that the burner has been locked out
Thus, during the lockout condition the first relay K is deenergised

but the second relay L remains energised, and the control circuit
remains in the condition until some positive action is taken to
deenergise the second relay L.
For this purpose, a manually-operated switch O is provided in the main
lead from the 70 positive pole of the source M to the control device
This switch O is normally held closed by spring action, but can be
operated when required to break the supply circuit momentarily When
this switch is operated, it will 75 cause the second relay L to be
deenergised.
This, as above mentioned, prepares the circuits for restarting, but
also transfers the first timing circuits H HI to the negative pole of
the source, thus permitting the capacitance H to 80 discharge slowly
during the two-minute time delay The control device remains locked out
until this time delay expires, when the control device is ready to be
restarted automatically by the controlling thermostat 85 A safety
relay P is preferably provided to guard against failure of the relay L
to operate its contacts for any reason when energised at the end of
the time delay of the timing circuit J JF Such failure would leave the
relay K con 90 tinuously energised and might create dangerous
conditions in the furnace The relay P has a time delay considerably
longer than that of the timing circuit J Il, and is energised when
contacts KI' and L' are both closed If 95 contact L' fails to open,
the relay P opens the main supply circuit at its contact Pl and
deenergises the relay K.
It will be appreciated that the foregoing arrangement has been
described by way of 100 example only and may be modified in various
ways within the scope of the invention Thus, for instance, if the
furnace is arranged to give automatic ignition (for example by the
provision of a permanently lighted gas pilot jet), 1 5 the control
device would be modified to omit the control circuit for the ignition
transformer B Again, in some instances, as for example in the case of
a gas-burning furnace, the burner motor A would not need to drive a
fuel-supply 110 pump, since the normal pressure of the gas mains would
suffice, and such burner motor could be omitted altogether, if
adequate provision is available for securing a proper draught in the
furnace, the control circuit for the 115 burner motor however still
being retained for the purpose of operating a gas-supply tap Further,
although a double triode will usually be preferred, two separate
triodes may be used or more generally two separate electronic dis 120
charge devices having control grids.
Again the foregoing arrangement is more especially intended for use
with light oils, but can readily be adapted for use with heavy oils by
the addition of further devices, including 125 an oil preheater
provided with a heater thermostat and a safety trip thermostat, as

well as a further controlling thermostat for preventing starting
unless a minimum oil temperature has been attained In such case, it is
usually desir 130 785,033 able to add further circuits to the control
device for energising indicating lamps to indicate whether the oil
heater is in operation or has been tripped out.
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* 5.8.23.4; 93p
* GB785034 (A)
Description: GB785034 (A) ? 1957-10-23
Multiple position beam tube
785,034 d, O Ha SB A Date of Application and filing Complete
Specification July 22, 1954.
No 21442154.
Application made in United States of America on July 24, 1953.
(Patent of Addition to No 759,153 dated May 29, 1953).
Index at Acceptance: -Class 39 ( 1), D 4 (A 1: A 7: D 1: F 6 B: G 1:
'G 3: K 3), D( 10 A 1: 17 A 2 B: 18 C: 34).
International Classification: -HO 1 j.
Multiple Position Beam Tube We, BURROUGHS CORPORATION, a corporation
organised under the laws of the State of Michigan, United States of
America, of Main Offices, 6071, Second Avenue, Detroit, Michigan,
United States of America, do hereby declare the invention, for which
we pray that a patent may be granted to us, and the method by which it
is to be performed, to be particularly described in and by the

following statement:This invention relates to improvements in or
modifications of the electron discharge device which forms the subject
of our Letters Patent No 759,153.
In the aforesaid patent, there is described and claimed an electron
discharge apparatus adapted to form and direct an electron beam in
which electrons follow trochoidal paths through the action of crossed
electrostatic and magnetic fields to cause selective impingement of
the beam on a plurality of collector electrodes, said electron
discharge device comprising a hermetically sealed envelope housing a
source of electrons adapted to emit a beam of electrons, and a first
electrode structure spaced from the electron source and constituted by
a plurality of spaced beam forming or control spade electrodes spaced
from each other to define passageways therebetween into which the
electron beam may be directed and locked, in which there is provided a
second electrode structure spaced from the first electrode structure
and disposed on the side thereof remote from said electron source and
constituted by a plurality of beam collector electrodes arranged with
respect to the control electrodes of the first structure so that each
collector electrode has at least one beam receiving area overlying the
passage way between two adjacent spade electrodes or two or more beam
receiving areas each overlying a different passageway and disposed to
receive the electron beam directed through the associated passageway,
and in which there is also provided a beam switching structure
situated intermediate the spade electrode structure and the beam
collector electrode structure and spaced therefrom, the beam switching
structure and the collector lprice 35 6 d 1 electrodes being so
constructed and arranged as to permit electron flow to the beam
receiving areas of the collector electrodes and to produce an output
from the collector electrodes that indicates the passageway through
which the beam is passing, said beam switching structure including one
or more distinct portions associated with respective juxtaposed spade
electrodes and collector electrodes and serving to effect, when
suitably excited, the switching of the beam from one passageway to
another.
Apparatus according to the aforesaid patent can be used with advantage
in code conversion systems, switching and multiplexing applications
for either modulated or unmodulated signals, counting and computing
devices, and similar applications requiring high speed beam switching
and especially in such applications where external circuitry is
desired to be simplified or equipment should be compact.
In addition to these uses, one particularly suitable application of an
electron discharge device according to the present invention is in
counting and computing devices.
According to the present invention, there is provided an improvement

in or modification of an electron discharge apparatus as claimed in
our Letters Patent No 759,153, which comprises providing one or more
collector electrodes each of which collector electrodes is placed in
front of only one of the passages defined between two adjacent spade
electrodes.
One or more apertures may be provided in the beam switching structure,
all of which are disposed in front of a single passageway between two
adjacent spade electrodes Where a single aperture is provided, it is
preferably in the form of a slot.
In some applications, it is advantageous to provide a plurality of
slots in the beam switching structure, each slot being disposed in
front of a respective passageway between two adjacent spade
electrodes, and in other applications, a slot may be provided for
every passageway formed by the spade electrodes.
The slots may vary in size or they may be substantially identical in
which case they are preferably of approximately the same length
785,034 as the electron emissive portion of thile cathode.
It is preferred to shape each collector electrode similarly to the
shape of the associated slot, the area of the collector electrode
being at least as large as the area of the slot, and to place the
collector electrode in front of its associated slot so as to intercept
substantially all the electrons passing therethrough.
When the slots are varied in area, the lengths of successive slots may
differ by regular increments.
In order to prevent cross coupling between collector electrodes,
suppressor electrodes maintained at the potential of the cathode may
be provided adjacent each of the collector electrodes.
The spade electrodes, beam switching structure and collector
electrodes may be arranged in successive lines, but preferably, they
are concentrically arranged about the cathode, the collector
electrodes being angularly displaced from a position in alignment with
the associated aperture or apertures and the cathode so as to
intercept substantially all the electrons passing through the aperture
or apertures in a curved path.
It is preferred to provide a spade resistance within the tube envelope
adjacent each spade electrode.
Tubes made in accordance with the present invention are especially
useful as counting or switching tubes For example, a decade counter
tube in which an output signal is derived in only one of ten beam
positions, can be provided by slotting the beam switching structure at
only one of ten beam positions of the tube and having a single
collector electrode opposite the slot.
Because variations in output voltage have relatively little effect on
tube operating stability, tubes made in accordance with the present

invention are suitable for use in multiplexing or other switching
operations, for example, where modulation of the electron beam takes
place.
Further, because multiple position beam tubes made in accordance with
the present invention have few critical spacings and are comprised of
parts which may be easily and economically fabricated, the tubes may
be easily assembled and economically produced.
There will now be described by way of example only, a preferred
embodiment of the invention with reference to the accompanying
drawings in which: Fig 1 is a perspective view, partly broken away,
illustrating an electrode structure for use in a multiple-position
beam tube having ten individual output electrodes in accordance with
the present invention; Fig 2 is a top plan view of the tube shown in
Fig 1; Fig 3 is an exploded view of the tube shown in Fig 1; Fig 4 is
a perspective view of a modification of the anode 32 shown in Fig 3;
Fig 5 is a plan view of a modification of the tube shown in Fig 1; Fig
6 is a plan view of a modification of the tube mount assembly shown in
Fig 1; and 70 Fig 7 is an isometric view, partly broken away, of a
mount assembly constructed in accordance with the present invention
and adapted for use as a decade counter tube.
In the mount assembly illustrated in Fig 1 75 and shown in more detail
in Figs 2 and 3, the arrangement of anode slots and collector
electrodes is utilized to provide a multiple position beam tube which
is especially useful as a switching or counting tube 80 Multiple
position beam tubes are described and claimed in our Patent No 759,153
and the construction and mode of operation of electron discharge
apparatus according to the present invention are similar to those
described in the 85 above patent.
Like the coding tube described in Patent No.
759,153, the tube shown in Figs 1, 2 and 3 has an elongated thermionic
cathode 24 which is centrally disposed within a hermetically 90 sealed
envelope 22 and is surrounded by a substantially cylindrical array of
elongated troughshaped spades A sleeve type cylindrical anode 32 ' of
larger diameter than the spade array is disposed coaxially and
concentrically with 95 respect thereto The anode has elongated slots
341, equal in number to the number of beam positions of the tube,
disposed substantially in parallel alignment with the cathode 24 and
so located with respect to the space between o 100 adjoining pairs of
spades that a substantial part of the electron beam locked in on any
one spade will pass through one of the slots 34 '.
In the embodiment shown in Fig 2 the slots are disposed directly in
line with the space 105 between each pair of adjoining spades However,
in view of the fact that the electron beam usually approaches the
slcts in a slightly curved path, it is possible to pass a larger

percentage of the beam through the slots if the latter are 110 offset
circumferentially slightly with respect to the spaces between the
spades In such case the direction in which the slots are offset should
be opposite to the direction of rotation of the electron beam 115 In
order to provide a separate output from every beam position,
individual collector electrodes 36 ' are disposed opposite each slot
34 ' in the anode 321 and the side of the anode which is opposite to
the spades 26 While the 120 collector electrodes 36 ' are aligned with
the space between the adjacent spades as are the slots 34 ' in the
anode 32 ', the collector electrodes 36 ' like the slots 341 may be
circumferentially displaced slightly with respect to the 125 spades
and in the same direction as the slots 341 are displaced in order to
permit a larger portion of the electron beam to impinge thereon Fig 5
shows the offset anode slots and collector electrode arrangement 130
785,034 Leads (not shown) to the individual spades, individual
collector electodes, anodes, and cathode are brought out through the
stem 124 (which may be of glass) to the base pins 46.
The switching time required to move the beam from one position to
another may be made more uniform if the spade resistors 64 are located
within the tube envelope One such arrangement of the spade resistors
64 is shown in Figs 1 and 2, in which each of the resistors 64 is
disposed between the sides of the spade 26 to which the individual
resistor is connected Because the resistors 64 are connected directly
to the spades in this arrangement, lead capacitances are minimised and
have much less effect on the switching time between individual beam
positions than if leads were provided to resistors located outside the
tube.
Other advantages accrue by the use of resistors which are located
inside the tube envelope.
All the resistors operate at the same temperature and are unaffected
by change in humidity.
Because the resistors operate in a vacuum, they may have a larger
wattage rating per unit physical size without burning out and
consequently result in a saving in space which is an important
advantage where equipment is to be miniaturized However, the increase
in switching speed and the uniformity of wave shape achieved through
the use of the internal spade impedance elements 64 is more than
sufficient reason to justify their use In addition to the advantageous
increase in switching speed made possible by the use of internal spade
resistors, the switching time from one beam position to another is
made more uniform Such uniformity becomes important when it is
considered that in many applications a discrete pulse width is
required to switch the position of the beam Variations in spade
impedance would result in changes in the pulse widths required to

switch the beam from position to position Thus, the pulse width
required to switch the beam to an " average " beam position might, for
example, be too short to switch the beam to another position or long
enough to advance the beam two positions if only a very short pulse
width is required for switching from one position to another.
Further, a reduction in the number of leads which must pass through
the tube envelope may be achieved if the switching of the beam is to
be accomplished by means other than pulsing the spade electrodes If
the spades are not used to switch the electron beam from one position
to another, individual spade leads are unnecessary and the internally
mounted spade resistors are connected to a common lead which may be
connected to the source of spade operating potential.
A quantized or stepped output from the tube of Figs 1, 2, or 3 may be
obtained if the anode 32 shown in Fig 4 is substituted for the slotted
anode shown in those figures The slot length is varied to control the
amount of output current available at the collector electrode of each
beam position The quantized or stepped output could, of course, be
achieved by varying either dimension of the slots 3411.
Another variation of the tube shown in Fig 70 1 is shown in Fig 7 In
that structure the anode 32 is slotted at only one beam position,
providing a decade counter tube having an output in only one of the
ten beam positions.
The spade resistors 64 shown in Fig 7 are 75 similar to those in Fig
1.
The anode 32 as shown in each of the embodiments of the present
invention, acts as an electrostatic shield between the collector
electrodes and spades, thus allowing the col 80 lector electrode
output to vary to a greater extent than was formerly possible without
the collector electrode field extending inwardly to such an extent
that it causes the beam to switch The positioning of the collector
elec 85 trodes beyond the spades rather than between them also reduces
the effect of the collector electrode field on beam switching
stability.
Further, this arrangement isolates the collector electrode from
adjoining spades both capa 90 citywise and physically Reduction in
spadeto-spade capacitance (through the collector electrode) results in
improved beam switching characteristics which result in the
unmodulated output wave more nearly resembling a square 95 wave The
physical isolation of spades and collector electrodes permits
collector electrodes having larger areas to be used, thus permitting
larger power outputs "Fringe" electrons near the edge of the electron
beam impinge 100 on the anode 32 and thus are not free to escape to
adjoining electrodes and cause cross talk.
The anode 32 and collector electrodes 36 may advantageously be

composed of materials which are poor secondary electron emitters or
105 the electrodes may be provided with a coating which reduces the
secondary emission capabilities of the material.
Fig 6 shows an electrode configuration which is similar to that shown
in Fig 2, but 110 has suppressor electrodes 126 disposed between
adjacent collector electrodes These suppressor electrodes, which are
illustrated as elongated rods; are normally maintained at or near to
cathode potential and tend to repel 115 stray electrons which do not
impinge on the intended collector electrode or any other electrons
which might, under the influence of the magnetic field or the positive
field, on adjacent collector electrodes, tend to impinge on adja 120
cent collector electrodes and cause cross talk.
The suppressors 126 may be connected to the cathode inside the tube or
they may be provided with a common lead through the tube envelope in
order that they may be biased in 125 any desired manner.
While specific embodiments of the present invention have been
described, it will be apparent that this invention is by no means
limited to the exact forms illustrated or the 130 use indicated, but
that many variations may be made in the particular structure used and
the purpose for which it is employed without departing from the scope
of the invention as set forth in the appended claims For example, the
spade electrodes, beam switching structure and collector electrodes
may be arranged in successive lines instead of concentrically about
the cathode, in a similar manner as described in Patent No 759,153 for
a "straight line" version of a multiple position beam tube.
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* GB785035 (A)
Description: GB785035 (A) ? 1957-10-23
Improvements in closed circuit turbine power plants

Inventors: ALEXANDER VELLAN and JEAN CRISTESCOU 785035 Date of filing
Complete Specification: Jan 6, 1955.
Application Date: Aug 3, 1954.
No 22463/54.
Complete Specification Published: Oct 23, 1957.
Index at acceptance:-Classes 110 ( 3), B 2 M 6; and 122 ( 3), A 7 X.
International Classification:-F Olc F 02 h.
Improvements in Closed Circuit Turbine Power Plants We, C V PRIME
MOVERS LIMITED, a British Company, of Bilbao House, 36/38, New Broad
Street, London, E C 2, do hereby declare the invention, for which we
pray that a patent may be granted to us, and the method by which it is
to be performed, to be particularly described in and by the following
statement: This invention relates to closed circuit turbine power
plants for heat recovery from low temperature heat sources, either
waste heat or natural heat, using a low boiling point working fluid
such as carbon dioxide, sulphur dioxide, or ammonia which is gaseous
at normal pressures and temperatures It is the object of the invention
to provide an improved plant of this character.
Specific examples of natural low grade heat and residual or waste heat
sources are springs and mine water as natural heat sources, and
exhaust steam or other exhaust gases of power or industrial plants,
the temperature level of which is not high enough to produce
mechanical energy by conventional means A further natural source of
heat is solar heat Also waste heat appearing as residual heat in burnt
gases or fluids resulting from chemical reactions or eventually
released from an industrial process (including nuclear plants) may be
utilized.
It is known that certain low boiling point media, if confined, attain
fairly high pressures when heated to temperatures of from 500 C.
to 200 WC The following figures show the pressures attained at
relatively low levels of temperature by suitable low boiling point
media, which are given as examples.
Ammonia (NH,) attains a pressure of 90 atms abs for a temperature
level of + 130 'C.
Sulphur dioxide (SO,) attains a pressure of atms abs for a temperature
level of + 130 WC.
Carbon dioxide (CO,) attains a pressure of 130 atms abs for a
temperature level of + 6 WC _ O ^ The invention consists in a power
plant for heat recovery from low temperature heat sources comprising a

closed circuit containing a low boiling point working fluid which is
gaseous at normal temperature and pressure, means for transferring
heat from a low temperature heat source, the temperature lev of which
does not exceed 200 C G, to, the working fluid, a turbine deriving
mechanical power from expansion of the working fluid, means for
transferring heat from the working fluid exhausted fromn the turbine
to a cooling agent, and a pump for raising the pressure of the working
fluid prior to the transfer of hept thereto from the heat source to' a
pressure substantially greater than the critical pressure of the
fluid, the heat source being a heat exchanger whereby the reception of
heat by the working fluid is substantially evenly distributed over the
working temperature range of the cycle, and the rejection of heat by
the working fluid to the cooling agent taking place substantially at
the minimum temperature of the working cycle.
The invention also consists in a power plant for heat recovery from
low temperature heat sources, comprising a closed circuit containing
carbon dioxide as a working fluid, means for transferring heat from a
low temperature heat source, the temperature level of which does not
exceed 200 C, to the working fluid, a turbine deriving mechanical
power from the expansion of the working fluid, means for transferring
heat from the working fluid exhausted from the turbine to, a cooling
agent, and a pum D for raising the pressure of the working fluid prior
to the transfer of heat thereto from the heat source to a pressure
substantially greater than the critical pressure of the working fluid.
In the accompanying drawing, Figure 1 is a diagrammatic view of one
form of power plant according to, the invention; Figure 2 is a
temperature-entropy diagram.
Referring to Figure 1, the reference numeral 2 785,035 1 generally
indicates a closed circuit in which is confined carbon dioxide, for
example, as the working fluid The circuit comprises piping and
includes an expansion turbine 2, the piping extending from the turbine
exhaust to a part 4 of the piping which extends through a heat
exchanger 5 where it is in direct contact with exhaust steam or waste
gases at a low temperature level, for example at 60 C ( 140 F) The
exhaust steam flows through the heat exchanger 5 contra to the
direction of flow of the working fluid in the part 4 of the piping and
said part 4 may be of coiled or serpentine form or may be replaced by
a bank of tubes The arrow heads show the direction of flow of the
working fluid and of the exhaust steam As an alternative instead of
the employment of exhaust steam a solar heater may be employed
directly to heat said part of the piping, or a solar heater may heat a
fluid which flows through the heat exchanger 5 In operation the
working fluid after being heated in that part 4 of the piping which
extends through the heat exchanger 5 whereby its temperature and

pressure are raised, will flow to the inlet of the expansion turbine 2
to drive the same In its passage through the turbine thle worlng flu'
d expands so that its temperature and pressure are lowered before
exhaust from the turbine A part 11 of the piping leading from the
turbine exhaust extends through a secondary heat exchanger 12 in which
the exhausted gaseous carbon dioxide is partially cooled and its
pressure is reduced The partly cooled exhaust gas then flows in the
piping to a part thereof which extends through another cooler 13
whereby the gaseous carbon dioxide is converted to the liquid phase
and collects in a closed vessel 14 A pump 15 forces liquid from the
vessel through piping, a part 16 of which extends through the
secondary heat exchanger 12 where it is partially heated and from
thence it flows to the part of the piping 4 in the primary heat
exchanger 5 Cooling liquid for the cooler 13 may be fed by a pump 17
from a supply 18 and returned by way of a spray 19.
Performance figures, for prime-movers such as described, may be
estimated by means of the T p diagram (temperature-entropy), for C 02
The results as calculated by N G T E.
(Pyestock, Hants), are tabulated below, for three distinct cases,
namely:
Case 1-Summer running, with a minimum C 02 cycle temperature of 25 C.
( 77 F), corresponding to a minimum pressure of 63 5 atms.
Case 2-Winter running, with a minimum C 02 cycle temperature of 15 C.
( 59 F) corresponding to a minimum pressure of 50 atms.
Case 3-" Refrigerated" (liquid air) running, with a minimum C 02 cycle
temperature of -55 C ( 131 F), corresponding to a minimum pressure of
6 atms.
In all three cases ( 1), ( 2) and ( 3) above, initial conditions of
temperature and pressure are identical, namely 180 C ( 356 F) and
atms.
Figure 2 is the termperature entropy diagram for a plant according to
Figure 1 using carbon dioxide with a maximum cycle tempri'atue' of 180
C and a maximum cycle pressure of 150 atmospheres.
The following table is derived from the relevant Tl, diagrams.
PERFORMANCE DATA TABLE Case 1 Case 2 Case 3 1 Max C 02 cycle
temperature C 180 C 180 C 180 C.
2 Max C 02 cycle pressure atmuns 150 Atms 150 Atms 150 Atms 3 Min C 02
cycle temperature C 25 C 15 ' C -55 C.
4 Mlin C 02 cycle pressure atms 63 4 Atms 50 Atms 6 Atms Yield of
power per pound per second of C 02, KW 19 7 KW 26 5 KW 68 2 KW 6 Cycle
efficiency % 14 1 % 19 1 o 29 3 % 7 Supply-of heat per pound per
second of C 02 circulated CHU 51 8 CHU 63 7 CHU 121 0 CHU 8 Extraction
of heat per pound per second of C 02 circulated, CHU 51 8 CHU 54 CHU
85 6 CHU 785,035 from the C 02, T-0 diagram, as a, practical example,

it follows that in order to produce, say 1000 KW, and assuming that:
Ordinary steam turbines and closed-cycle gas turbines (air), may not
function under conditions as given in the above table.
From the above performance figures derived Max C 02 cycle temperature
T 1 C = + 180 C ( 356 F) Max C 02 cycle pressure Pl atms = 150 ATMS
Min C 02 cycle temperature T 2 C = + 15 C ( 59 F) Min C 02 cycle
pressure P 2 atms = 50 ATMS, the following conditions will arise.
It will be seen that the example ( 1000 KW) is taken for winter
running conditions These conditions have been selected as located
between the two extreme conditions, viz Summer running (+ 25 C) and
"refrigerated" running ( 55 C) (-67 F) A minimum C 02 cycle
temperature of + 15 C ( 590 F) is reasonably correct over a wide range
of territories and for the best part of the year.
Let W =yield of power per pound per second of C 02 in KW W = 1000 KW
(assumed) m = 26 5 KW per pound per second of C 02 (from table above)
01 = 63 7 CHU, supply of heat per pound per second of C 02 circulated
(from above table)
02 = 54 CHU extraction of heat per pound per second of CO 2 circulated
(from above table)
0 A 1 =supply of heat per pound per second of CO, circulated for 1000
KW 0 '2 =extraction of heat per pound per second of CO, circulated for
1000 KW M =lb/sec of CO, for 1000 KW We have:
W 1000 M = = m 26 5 = 37 7 lbs/sec of C 02, for 1000 KW.
011 = 63 7 x 37 7 = 2401 49 CHU per second per pound of C 02
circulated and 0 '2 = 54 x 37 7 = 2035 8 CHU per pound per second of C
02 circulated.
The above value of M= 37 7 does not allow for cooling-cycle losses and
pressure losses, in the C 02 cycle, due to the heat exchanger.
Allowances have been made concerning the expansion in the turbine,
when establishing the figure of 26 5 KW.
In other words, under conditions as assumed, in order to generate 1000
KW it is necessary to circulate 37 7 lbs/sec of C 02 in the closed
circuit of the prime-mover, neglecting losses as indicated above.
In the same way for "Summer" running (+ 250 C) ( + 77 F) we have:
W 1000 M=_=m 19 7 = 50 7 lbs/sec of C 02 for 1000 KW.
and for "refrigerated" (-55 C) running we have:
W 1000 M=-= m 68 2 = + 14 6 lbs/sec of C 02 for 1000 KW.
The same remarks apply regarding losses as above.
As an example, if a pump be used under conditions of Winter running (+
15 C minimum cycle temperature) the work in HP necessary for the
return of the working fluid in a unit intended to, generate 1000 KW
will be given by HO Wp= 8 n Where:
H = 1033 metres of water = 100 auns.
Q= 17 1 Kg/sec = 37 7 lbs/sec for 1000 KW 8 = 0 81 sp wt of liquid C

02 Kg/1 =Conversion factor Substituting we have:
0.81 x 17 1 x 1033 W:
192 5 HP = 142 KW Assuming an efficiency of pump of = 65 % we have
Work done= 218 KW necessary for the return of 37 7 lbs/sec of C 02 in
the closed circuit, producing 1000 KW in the prime-mover.
Net output of prime-mover 1000 218 = 782 KW Also, referring to one
pound of C 02 circulated per second, giving 26 5 KW, the work done to
return, by means of a pump, the working fluid, will be 218 -= 5 8 KW
37.7 Thus, net output per pound of C 02 per sec.
circulated will be: 100 26.5 5 8 = 20 7 KW.
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* GB785036 (A)
Description: GB785036 (A) ? 1957-10-23
Improvements in and relating to speed regulating and current limit motor
control systems
78590363 o Date of Application and filing Complete Specification Aug
17, 1954.
No 23904/54.
Application made in United States of America on Aug 26, 1953.
Index at Acceptance:-Class 38 ( 4), R( 4: 33 D 2: 61: 62: 67: 112 A).
International Classification: -GO 5 c.
Improvements in and relating to Speed Regulating and' Current Limit
Motor Control Systems We, IGRANIC ELECTRIC COMPANY LIMITED, a British

Company of Elstow Road, Bedford, in the County of Bedford, do hereby
declare the invention, for which we pray that a patent may be granted
to us, and the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to speed regulators and current limit motor
control systems.
The present invention provides an improved speed regulating, find
current limit control system characterised by low steady state error,
relatively high system stability and sharp current limit action.
The invention also provides a voltage comparison circuit for the speed
regulating control element of a regulator which automatically limits
the voltage difference which may be developed across such element to
protect the 2 (v same against excessive voltage.
The invention further provides a voltage comparison circuit for the
current limit control element of the aforementioned regulator in which
the motor current signal voltage is supplemented by a portion of the
voltage difference in the voltage comparison circuit for the speed
regulating control element for increasing the sharpness of current
limit action.
Other features and advantages of the invention will hereinafter
appear.
The invention consists broadly of a control system for ian electric
motor, wherein said motor drives a generator and said generator is
included in a circuit with a source of reference voltage and a control
winding of an amplifying Regulator, for subjecting said control
winding to the voltage difference between said source and said
generator, and the voltage supplied to the armature of said motor is
varied according to the output of said amplifying regulator, an
element, rendered conductive upon attainment of a given voltage
difference, being adapted to shunt a greater portion of the current of
said circuit around said control winding.
The accompanying drawings illustrate prelPdce 3 s 6 d l ferred
embodiments of the invention which will now be described by way of
example only.
In the drawings, 50 Figure 1 is a diagrammatic showing of a rectified
alternating current control system for a D C motor incorporating the
invention.
Figure 2 depicts a modification of a part of the control system of
Figure 1, and 55 Figure 3 is a diagrammatic showing of an adjustable
voltage drive incorporating the invention.
Referring to Figure 1 the numeral 5 generally designates la
transformer having a primary 60 winding 6, which may be assumed to be
connected to a suitable source of alternating voltage supply, and
having secondary windings 7, 8, 9 and 10 Secondary winding 7 is

provided with end terminals 7 a and 7 b% centre tap ter 65 minal 7 and
intermediate tap terminals 7 ' and 7 End terminal 7 a is connected in
series with an input winding lla of a current transformer 11 to the
anode 12 b of a gas filled thermionic valve 12, which is also provided
with a cathode 70 12 a and a control electrode 120 End terminal 7 b is
connected in series with another input winding 11 b of current
transformer 11 to the anode 13 b of a valve 13, like valve 12 Tube 13
is also provided with a cathode 13 a and a 75 control electrode 13 The
cathodes 12 a and 13 a of valves 12 and 13 are connected together to
one terminal of armature 14 a of a direct current motor 14 The other
armature terminal of motor 14 is connected to centre tap terminal 80
of secondary winding 7.
The control electrodes 120 and 13 e of valves 12 and 13 are connected
together, in series with a secondary winding 15 b of a transformer 15,
which has a primary winding 15 a Second 85 ary winding 15 b has a
centre tap terminal 150 which is connected to the point common to
cathodes 12 a and 13 a and the first mentioned motor armature terminal
A filter capacitor 16 is connected between the control electrode 120
90 and the cathode 12 a of valve 12, and a similar filter capacitor 17
is connected between the control electrode 130 and cathode 13 a of
valve 13.
785,036 The primary winding 15 i of transformer 15 is connected at one
end terminal to centre tap terminal 7 of secondary winding 7 P and is
connected at its other end terminal in series with A C windings 18 a
and 18 b of a saturable reactor 18 to intermediate tap terminal 7 of
winding 7 The point common between winding 15 a and 181 is connected
in series with a resistor 19 to intermediate tap terminal 7 d of
winding 7 As will be apparent, winding 15 ' of transformer 15,
windings 183 ' and 18 b of saturable reactor 18, and resistor 19
comprise a phase shift network, whereby, in accordance with the
energization of D C winding 15 of reactor 18, the potential applied on
the control electrode of valves 12 and 13 may be shifted in time-phase
with respect to the potentials applied to the anodes The energizaion
of the D C winding 18 ' of reactor 18 will be hereinafter described.
Motor 14 is provided with a shunt field 14 b which is connected to the
D C terminals of a full-wave rectifier bridge 20 The A C terminals of
rectifier bridge 20 are connected to the end terminals of the
aforementioned secondary winding 8 of transformer 5.
Armature 14 A of motor 14 is mechanically connected to a tachometer
generator 21, which is connected at its low potential armature
terminal to the low potential armature terminal of a tachometer
generator 22, which may be assumed to be driven by a machine element
with whose speed motor 14 is to be regulated or matched Tachometer
generator 22 is connected at its high potential armature terminal in

series with a D C control winding 23 a of a self-saturating magnetic
amplifier 23, a halfwave rectifier 24, which preferably has no
appreciable threshold conducting voltage in the forward direction,
such as for example a germanium diode a resistor 25 and the resistance
element of a voltage divider 26 to the high potential armature
terminal of tachometer generator 21 A half-wave rectifier 27 is
connected at its input terminal to the point common between the high
potential armature terminal of tachometer generator 22 and winding 23
% and is connected at its output terminal to the point intermediate,
the resistor 25 and voltage divider 26.
As will be apparent the voltage difference between tachometer 22 and
tachometer 21 is impressed across the winding 23 a of magnetic
amplifier 23, whenever the potential of tachometer 22 is higher than
the potential of tachometer generator 21 Rectifier 24 prevents reverse
flow through winding 23 a in the event there is reduction in the
output voltage of tachometer generator 22 below that of tachometer
generator 21.
Rectifier 27 acts to limit the voltage which will appear across the
series circuit comprising winding 23 a, rectifier 24 and resistor 25,
and rectifier 27 is so chosen that it will commence to conduct only
when the voltage across it exceeds a certain value as determined by
the voltage rating of winding 23 a Thus, any attempt to increase the
voltage across rectifier 27 results in most of the current flowing
through rectifier 27 and appearing as a voltage 70 drop across the
resistance element voltage divider 26 By proper selection of the ohmic
value of resistor 25 it is thus possible to keep the voltage across
winding 23 a to a very low level.
This not only protects winding 23 a during 75 accelerating and
deceleration of motor 14, but also limits the level of ampere turns
which may be developed by winding 23 a in magnetic amplifier 23.
Amplifier 23 is provided with A C main 80 windings 23 Y and 23 ',
which are connected at corresponding ends to one end terminal of the
aforementioned secondary winding 9 of transformer 5 The other end of
winding 23 e is connected to the output terminal of the half 85 wave
rectifier 230, whose input terminal is connected to the output
terminal 23 f Terminal 23 f is connected to the input terminal of a
half-wave rectifier 23 whose output terminal is connected to the other
end terminal of secondary 90 winding 9 The other end of winding 23 d
is connected in series with the input terminal of a half-wave
rectifier 23 h, whose output terminal is connected to the output
terminal 23 Y.
Terminal 23 i is connected to the output ter 95 minal of a half-wave
rectifier 23 k whose input terminal is connected to the last mentioned
end terminal of the secondary winding 9 Output terminals 23 f and 23 i

of amplifier 23 are connected to the end terminals of control 100
winding 18 ' of saturable reactor 18 The control system as thus far
described provides speed regulating control of motor 14 The system is
additionally provided with current limit control which will now be
described 105 Amplifier 23 is provided with another D C.
control winding 23 b, which is connected at one end in series with a
resistor 28 to the high potential D C terminal of a full-wave bridge
rectifier 29, whose output terminal is 110 connected to adjusting
element 26 a of voltage divider resistor 26 Winding 23 b is connected
at its other end in series with a resistor 30 and a half-wave
rectifier 31 to the adjusting element 32 ' of a potentiometer 32,
which has a 115 resistance element 32 " Resistance element 321 of
potentiometer 32 is connected across the D.C terminals of a full wave
bridge rectifier 33 The A C terminals of rectifier 29 are connected to
the end terminals of output wind 120 ing 1 le of current transformer
11 The A C.
terminals of rectifier 33 are connected to the end terminals of the
aforementioned secondary winding 10 of transformer 5 Rectifier 29 has
connected across its D C terminals a 125 smoothing capacitor 34, and
rectifier 33 has a smoothing capacitor 35 connected across its D.C
terminals.
As will be apparent, the voltage across the control winding 23 b of
amplifier 23 is the 130 785,036 difference between, on the one hand,
the D C.
reference voltage between the adjusting element 32 a and the left hand
end of resistance 32 b of potentiometer 32, and, on the other hand, a
variable D C voltage which is the sum of the variable voltage derived
from winding 110 of current transformer 11 and rectifier 29, plus the
variable voltage obtaining between the adjusting element 26 a and the
right hand end of the resistance element of voltage divider 26 Thus,
whenever the magnitude of such variable D C voltage is greater than
the D C reference voltage, current will flow through winding 23 b to
develop ampere turns, which may be assumed to counteract the ampere
turns developed by control winding 230 and thereby decrease the output
of amplifier 23, or even turn the latter off The rectifier 31 prevents
current flow in the reverse direction, thereby preventing winding 23 b
acting cumulatively with winding 23 a.
The operation of the system of Fig 1 as a whole will now be described.
Assume that motor 14 is rotating at the desired speed but with
practically no load.
Now let it be assumed that the armature 14 a of motor 14 is gradually
loaded up This of course results in slow-down of armature speed.
Accordingly, the output voltage of tachometer generator 21 decreases
resulting in a voltage difference across control winding 230 which

increases the output voltage across terminals 231 and 23 ' of
amplifier 23 Thus the voltage across D C winding 18 of saturable
reactor 18 is increased, thereby decreasing the impedance of A C
windings 18 i and 18 b Consequently the alternating voltage applied to
control electrodes 12 and 130 of valves 12 and 13 will be shifted more
in-phase with the anode potentials of such valves and thus the latter
will conduct over a greater portion of their conducting half cycles,
thereby increasing the current supplied to armature 140 of the motor
Motor 14 will consequently increase in speed aiid the output of
tachometer generator 21 will increase, thereby decreasing the voltage
difference across winding 23 a of amplifier 23 to decrease the output
of the latter Ultimately, the system will stabilize with motor 14
running at a speed only slightly less than its aforementioned no load
speed.
During the aforementioned action of the control system, the current
flowing through valves 12 and 13, and hence through windings 11 a and
1 b of current transformer 11, causes a voltage to be developed across
capacitor 34.
As long as the voltage across capacitor 34 is less than the voltage
across the low potential side of the resistance element 32 b of
potentiometer 32 no current will flow in control winding 23 b because
of the blocking action C 9 rectifier 31 If the current flowing through
valves 12 and 13 increases sufficiently so that the voltage across
capacitor 34 exceeds the reference voltage afforded by potentiometer
32, then the current which flows in winding 23 b will tend to reduce
the voltage output of amplifier 23, and hence the voltage output to
armature 14 a of the motor.
Reduction in the applied voltage on the 70 motor armature tends to
decrease the motor speed, and hence the speed and voltage output of
tachometer generator 21 The resultant increase in differential voltage
across winding 230 will tend to increase the voltage output 75 to the
motor armature to maintain the speed, which action is opposed to the
aforementioned action produced by the increasing current flow in tubes
12 and 13.
Since the current limit action is a safety 80 feature it is made to
predominate over the speed regulating action To further limit the
speed regulating action, when excessive values of current are reached
in the motor armature current, rectifier 27 conducts to limit the 85
differential voltage applied across winding 23 a, and a voltage
proportional to the excess differential voltage, appearing across the
resistance element of voltage divider 26 is added to the voltage
appearing across capacitor 34 to aid 90 in current limit action This
summation of voltages during current limit action results in a very
definite current value, above which, the control system is responsive

only to the current limit portion of the control system, and 95 the
output voltage of amplifier 23 is decreased to whatever value is
necessary to maintain the current flowing in the motor armature at the
limiting value Below such limiting value, the control system is
responsive only to the speed 1001 regulating portion thereof.
While in the system of Figure 1 the tachometer generator 22 has been
described as a source of reference voltage in the speed regulating
voltage comparison circuit, it will be 105 apparent that any other
suitable source of D C.
reference voltage, such as for example the series connected battery 37
and adjustable resistor 38 shown in Figure 2 can be used in place
thereof 110 In Figure 3 there is shown a form of the speed regulating
and current limit control system as applied to Ward Leonard drive It
will be noted that elements of the system in Figure 3, which are
identical to those in Figure 115 1 are given corresponding reference
numerals.
The Ward Leonard drive comprises a D C.
motor 40, having an armature 40 a connected in a loop-circuit with the
armature 410 of a D.C generator 41 D C control windings 420 120 and 42
b of a saturable reactor 42 are connected in series in the
loop-circuit, and provide a source of current limit signal.
Motor 40 is provided with a shunt field winding 40 T which is
connected at one end in 125 series with an adjustable resistor 43 to
the input D C terminal of a full-wave rectifier bridge 44 and is
connected at its other end to the output D C terminal of rectifier 44
Rectifier 44 has its A C terminals connected to a 130 785,036
secondary winding 45 of a transformer 46, having a primary winding 47
which may be assumed to be connected to a suitable source of
alternating voltage supply Transformer 46 is provided with other
secondary windings 48, 49 and 50 Generator 41 is provided with a shunt
field winding 41 b which is connected to output terminals 23 f and 23
' of amplifier 23.
Saturable reactor 42 is provided with a pair of series connected A C
winding 420 and 42 d, and one end thereof is connected to one end
terminal of secondary winding 48 while the other end of such series
connected windings is connected to one A C terminal of rectifier 29
The other A C terminal of rectifier 29 is connected to the other end
terminal of secondary winding 48.
Secondary winding 49 provides the source of A C input for amplifier
23, with one end terminal being connected to corresponding ends of
windings 23 c and 23 d, and the other end terminal being connected to
the output and input terminals of rectifiers 23: and 23 k,
respectively The A C terminals of rectifier 33 are connected to the
end terminals of secondary winding 50.

The operation of the speed regulating and current limit portions of
the control system of Figure 3 will be like that of the embodiment of
Figure 1, except that their effect on the motor 40 will be
intermediately through control of armature voltage of generator 41.
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* GB785037 (A)
Description: GB785037 (A) ? 1957-10-23
Improvements in or relating to electromagnetic brakes
785,037 Date of Application and filing Complete Specification: Aug 20,
1954.
No 24287/54.
Application made in United States of America on Nov 27, 1953.
Complete Specification Published: Oct 23, 1957.
Index at acceptancie -Classes 12 ( 3), C 5 B 3 C; 65 ( 2), F( 1 G: 3
E: 3 F); and 103 ( 1), E 2 E, E 2 M 1 (B 3 A:
B 4 G: E 4: E 6: E 7: F 2: K 2).
International Classification:-F 06 d, n.
COMPLETE SPEGIIFI'CATION Improvements in or relating to
Electromagnetic Brakes We, IGRANIC ELECTRIC COMPANY, LIMITED, a
British Company of, 'Elstow Road, Bedford in the County of Bedford, do
hereby declare the invention, for which we pray that a patent may be
granted to us, and the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to electromagnetic brakes and has for one of

its objects the provision of an improved brake having brake shoe
operating parts which can be easily removed to facilitate repair and
replacement of various brake parts Other objects and advantages wilt
appear hereinafter.
According to the invention there is provided an electromagnetically
operated friction brake in which at least one brake shoe, supported
from a base, is moved into and out of engagement with a brake drum by
the pivoting action of a member pivotally mounted on said, base and
actuated by an energisable magnet carried by said base, the pivotal
mounting of said member on said base being effected by means of a
flexible strap attaching said member to said base.
Other features and advantages of the invention will become apparent
from the following description of one particular embodiment given by
way of example only, with reference to the accompanying drawings, in
which:Figure 1 is a side elevational view of an electromagnetic
external shoe drum brake embodying the present invention, several of
the parts thereof being shown in section,.
Figure 2 is an end view of the brake shown in Figure 1 and, Figure 3
is a fragmentary sectional view taken substantially along line 3-3, of
Figure 1.
Like reference characters indicate corresponding parts throughout the
several views of the drawings.
Referring to Figure 1, it illustrates a brake drum 1 to be secured to
a motor or other lPrice 3 s 6 d 1 device to be bralked, opposed brake
shoes 2 and 3 for frictionally engaging said drum on opposite sides
thereof, and upwardly extending levers 4 and 5 to support and operate
said shoes respectively The lower ends of levers 4 and 5 are pivatally
mounted on a base 6, and an electromagnet 7 also mounted on said base
6 is provided for operation of said levers.
Electromagnet 7 is provided with a field element including an
energizing winding 8 and co-operating armature members 9 and 10
arranged on opposite sides thereof Armature is pivotally mounted on
base 6 and is operatively connected to' lever 4 by a link 11.
Said link 11 is attached to armature member by means of pin, 12, and
to lever 4 by means of pairs of nuts 13 and 14 and springs as shown in
Figure 1 'Such connection between link 11 and lever 4 provides
adjustability as is well known in the electromagnetic brake art
Armature member 9 is also pivotally mounted on a base 6 an& is
operatively connected to lever 5 thxough adjustable spacing means to
be hereinafter described Energizing winding 8 is completely, encased
by side plates 1,6, ring member 17, cover strap 118, and support plate
19 Cover strap 18 is fastened to support plate 19 'by means of
threaded studs 20 and nuts 20 a Said studs are welded to strap 18 ' in
any well known manner As shown in Figure 2, support plate 19 is firmly

attached to base 6 by means of bolts 21 extending flange portions of
base 6 and threadingly engaging said support plate 19.
As shown in Figure 1, armature members 9 and 10 are positioned in
elongated shallow recesses formed in base 6 and are pivotally mounted
therein by means of straps 22 formed of resilient material such as
spring steel.
Bolts 23 are provided, for attaching said straps 22 to armature
members 9 and 10 and to base member 6.
Adjustable spring means 24 are provided for effecting separation of
armature members 9 and 10 whenever energizing winding 8 is in an
unenergized state Such spring means is well known in the
electromagnetic brake art and permits adjustment of the compressive
force of the operating spring in a well known manner Also provided in
electromagnet 7 is a spacer 25 and sealing strap 26, each of which
functions in a well known manner.
o 10 The adjustable spacing means between lever and, armature member 9
comprises an Lshaped mounting bracket 27, bolt 28, nut 29, and
wedge-shaped spacer block 30 Member 27 is attached as shown in Figure
1 to lever 5 by any suitable means such as by welding.
It is believedl apparent that bracket 27 need not be a separate
element but could be formed integral with lever 5 Bolt 28 extends
through an opening formed in member 27 and threadedly engages spacer
block 30 A compression spring 31 and sleeve 32 are provided to retain
nut 29, which is welded to bolt 28, in abutting relation with the
L-shaped, bracket 27 By this means the relative position of armature
member 9 and lever 5 can be varied by turning bolt 28 to move spacer
block 30.
Each of the brake shoes 2 and 3 is attached to its respective
operating lever 4 and 5 by means of a pair of bolts 33 the shanks of
which extend through clearance openings in the operating lever and
threadedly engage the brake shoe Such openings in levers 4 and 5 are
elongated vertically to permit adjustment of the brake shoes in a
vertical plane.
The lower end portion of each of said operating levers 4 and 5 is
formed into a segment of a cylinder 34 As shown in Figure 1, base 6 is
formed with a surface complemental to said cylinder segment 34 to thus
co-operate therewith as a roller and socket joint As illustrated in
Figures 1 and 3, said cylinder segments 34 are provided with recesses
for retention of pins 35 Said pins 35 ft into openings 36 a formed in
mounting plates 36 Said 4 plates 36 are mounted on base 6 by means of
bolts 37 as shown in Figures 1 and 3 Thus, operating levers 4 and 5
can be pivotally moved relatively to base 6 while maintaining a high
degree of bearing surface between cylinder segments 34 and said base
6.

The bearing surfaces of segments 34 and base 6 are lubricated by means
of an absorbent material such as felt saturated with a suitable
lubricant and disposed between the respective operating levers 4 and
5, and base 6, as shown in Figure 1 A small bracket 38 and screws,
such as shown at 39 in 'Figure 1, retain the absorbent material in
such position The arrangement is preferably such that upon brake
releasing pivotal movement of the operating levers 4 and, 5 relatively
to base 6 associated therewith acts to compress slightly the absorbent
material associated therewith to thus emit some of the lubricant which
flows into the aforementioned roller and socket joints It is further
seen that the absorbent material acts as a seal to prevent foreign
matter from entering the joint and causing damage to the bearing
surfaces.
It is apparent that each operating lever 4 70 and 5 can be removed by
simply detaching one of the mounting plates 36 from base 6 and sliding
the operating lever outwardly for a distance of approximately one inch
in a direction parallel to the axis of drum 1, and 75 then lifting the
same free of the other brake elements.
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