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1. * GB780190 (A)
Description: GB780190 (A) ? 1957-07-31
Improvements in or relating to vehicle control systems
Description of GB780190 (A)
We, THE PLESSEY CoxmPA2NY LIMITED. a
British Company, of 56 Vicarage Lane, Ilford, Essex, 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 des-
cribed in and by the following statement:--
This invention relates to control systems of the kind in which an
inductive element on a vehicle is influenced by a magnet system
arranged on the track to effect control of the vehicle passing
thereover.
An object of the present invention is to provide an improved receiver
which responds to the condition of the track magnet system, applying
the brakes and/or giving a visual and audible warning when the vehicle
passes over the track magnet system.
Another object of the invention is to provide a system which avoids
the use of relays and their associated contacts which are not reliable
owing to vibration, dirt and general climatic conditions.
According to this invention the control system of the kind referred to
consists of a unit having a plurality of transductors which are
operated in series from pulses generated by either an induction coil
or a further transductor passing over the magnet system, to control
the energisation of a solenoid such as an electro-pneumatic valve
solenoid controlling the vehicle braking system and/or the
energisation of a solenoid controlling the vehicle traction power
supply and/or audible and/or visual signal on the vehicle.
The invention will now be described as applied to a railway with
reference to the accompanying drawings is which:Fig. 1 is a block
diagram of the circuit arrangement; Fig. 2 shows a horizontal form of
magnet system:
Fig. 3 shows a vertical form of magnet system; and Fig. 4 is a
schematic circuit arrangement; and to the drawing accompanying the

2. Provisional Specification in which:-
Fig. 1 is a block diagram; and Fig. 2 shows a horizontal form of
magnet system.
The tracts system at each signal comprises a permanent magnet 1 or 1A
and an electromagnet 2 or 2A arranged to order such that traffic
passes over them in the direction shown by the arrow. The
electromagnet 2 is arranged parallel to the track 3, in axial
alignment with the permanent magnet 1 and with poles of similar
polarity facing each other, or alternatively as shown in Fig. 3 the
electromagnet 2A and the permanent magnet 1A may be arranged
vertically with the poles of opposite polarity uppermost.
The transductors used in this invention are auto-self-excited bridge
rectifying transductors as defined in para. 5240 B.S.S. 1523:
1954 Section 5, which by the addition of positive feedback are made
inherently unstable and so have two discrete stable operating
conditions. In the case of transductor or flip-flop B in Fig. 4 a bias
winding X has been included to maintain the minimum current condition
and a reset winding W enables the flip-flop to be restored to the
maximum current condition. Flip-flops H and L in Fig. 4 have the
positive feedback windings connected in series with timing capacitors,
thereby converting these transductors into oscillators; bias windings
Y and Z are included to exercise control by ensuring that the
oscillator ceases at the end of the cycle following cessation of the
input signal.
An inductive element A is conveniently 780,190 PATENT SPEC WI'ATON
Inventors: -RONALD GEORGE JOHN MARTIN and ERNEST ATHOLSTAN
ESSEX-CROSBY.
Date of filing Complete Specification: Feb. 16, 1955.
Application Date: Feb. 17, 1954. No. 4618/54.
Complete Specification Published: July 31,1957.
Index at Acceptance:-Classes 40(4), 79(0: J); and 105l A14AS.
International Hl0seifioation:-611. H3fo COMPLETE SPECIFICATION.
Improvements in or relating to Vehiele Uontrol Systems.
fixed to the front of the locomnotive or under the train so that it
can be influenced in a known manner by the magnets 1 and 2 or 1A and
2A on passing them.
Mounted in the locomotive cab or in the driver's compartment is a unit
consisting of transductors and an alarm bell and indicator which are
operated as follows:When the inductive element A is carried over the
uppermost pole of the permanent magnet 1A, a double pulse is
generated. The first pulse occurs as the element enters the magnet's
field, the second as the element leaves the field. These pulses are
fed to a flip-flop transductor B which is known as the
electro-pneumatic valve flip-flop transductor because its output

3. current controls the electro-pneumatic valve solenoid and is
hereinafter referred to as an "E.P.V. flip-flop transductor". At this
stage the E.P.V. flipflop B is conducting.
The first pulse is arranged to drive the E.P.V. flip-flop B into its
conducting state and since it has already reached such state no action
by the pulse results. The second pulse drives the E.P.V. flip-flop B
to minimum current.
The output of the E.P.V. flip-flop B is taken to a time delay device D
consisting of a capacitor C1 Fig. 4 acting as a slug to the
electro-pneumatic valve solenoid E which holds the brake valve in the
"brakes-off" position. Therefore when the E.P.V. flipflop B drops to
minimum current, the supply to solenoid E is cut off. The time delay
device D however holds the solenoid E in for a predetermined time. The
drop in output of the E.P.V. flip-flop B operates the indicator F. If
the inductive element A now passes over the electro-magnet 2A in the
deenergised condition as when the signal is at "stop", no further
pulse is passed to E.P.V. flip-flop B which remains in the minimum
current condition. At the end of the delay provided by the time delay
device D, the current in the solenoid E dies away, allowing the
solenoid E to release and actuate the train braking system. Air
passing into the train braking system on release of the solenoid E
passes through a horn, thereby giving an audible signal.
If the electro-magnet 2A is energised, for example when a signal
indicates "clear" again two pulses of opposite polarity are obtained
from the inductive element A but in the reverse order as those
obtained from magnet 1A since the electromagnet 2A is reversed with
respect to the permanent magnet 1A. The E.P.V. flip-flop B ignores the
first pulse since it is already at a minimum current, but rises to its
maximum current on the second pulse.
The supply to the time delay device D and solenoid E is restored
normally within the time delay period. The current to the indicator F
is restored but as indicator F is polarised it does not return to its
original "yellow" condition but remains at "black".
In order to operate the bell signal on "clear", the output of the
E.P.V. flip-flop B 70 operates into two transductors, H and J. The
first of these transductors H is the bell timing flip-flop which on
receiving a positive pulse from the E.P.V. flip-flop B, derived from
the time delay capacitor C1, rises to 75 its maximum current state,
remains in that state for a given period after which it returns to the
minimum current condition. The duration of this period may be amended
by alteration of the values of capacitor C2 and 80 resistor R5 Fig. 4.
The output of the bell timing flip-flop H is applied to the bell
oscillating transductor L, the twenty cycle per second pulsating
direct current output of which is used to 85 drive the armature of the

4. bell M.
The second of the above-mentioned transductors controlled by the
E.P.V. flip-flop B is the bell locking flip-flop J. This is connected
in the circuit to the brake valve solenoid E and only conducts when
the brakes have been applied. It is used to prevent the bell M ringing
when passing two or more successive "danger" signals such as when two
or more distant signals are used and 95 the driver of the train has
not reset the indicator F after passing one of them.
Resetting of the apparatus is accomplished by operating the reset
handle N which supplies a resetting signal to the E.P.V. flip-flop 100
B and disconnects the "trip" coil of the indicator F.
The resetting contacts are the only contacts in the system and could
if necessary be replaced by variable reactors. 105o To give additional
protection the pulses generated in the inductive element A are fed to
the E.P.V. flip-flop B through a coupling network P, consisting of
resistors R1, R2, R3 and R4, Fig. 4, in such a way that 11i if the
inductive element A becomes disconnected from the E.P.V. flip-flop B,
the latter receives a pulse arranged to drive it to minimum current.
This causes the solenoid E to release and apply the brakes as before.
115 The solenoid E or an additional such solenoid can be arranged to
disconnect the power supply as used on electric and dieselelectric
trains. Alternatively the solenoid E can be arranged to operate the
fuel injector 120 on a deisel engine in order to reduce the power
output. In all these cases the release of solenoid E can be arranged
to apply the train brakes as well as disconnecting or reducin thile
tractive nower. 125 According to tihe arrangement shown in the drawing
acconm:)anying the Provisional Specification, the track system at each
signal comprises a iar, -anent magnet 1 and an electro-magnet 2
arranged in order such that 130 780,190 If the electromagnet 2 is
energised as when the signal is at "clear", a double pulse is
generated as the inductor coil A passes over the poles of
electromagnet 2. This double pulse is in the reverse order to the 70
double pulse received when the inductor coil A moved over the
permanent magnet 1 because electromagnet 2 is reversed with respect to
the permanent magnet 1. The flip-flop B ignores the first pulse since
it is 75 already at minimum current but rises to its maximum current
on the second pulse.
The supply to the brake valve solenoid E is restored normally within a
second and the indicator transductor G returns to a minimum current.
The indicator F is polarised however and does not return to its
original "yellow" condition but remains at "black".
In order to operate the bell on signal "clear" the flp-flop output B
operates into 85 two transductors H and J further to that already
mentioned. The first of these additional transductors H is the bell

5. timing transductor, which on receiving a positive pulse from the
flip-flop B rises to its maxirum current state, remains in that state
for three seconds, after which it returns to the minimum current
condition. The output of the bell timing transductor H is taken to a
bell saturable reactor K which controls the 95 supply to a bell
oscillating transductor L, the twenty cycle per second, pulsing D.C.
output of which is used to drive the bell armature M.
The second of the above-mentioned transductors controlled by the
flip-flop,B is a bell locking flip-flop J. This is connected in the
brake valve solenoid E slugging circuit and only conducts when the
brakes have been applied. This is used to cut out the 105 bell when
passing two successive magnet systems such as on the occasion when two
distant signals are used and in the event of the driver not
resetting.the indicator F between them after a caution on the first.
110 Resetfing of the apparatus is accomplished by a contact on a
"reset handle" which supplies resetting signals to the flip-flop B and
indicator F and a bell blanking signal to the timing transductor H.
This latter 115 signal is necessary since a pulse from the timing
transductor H is obtained whenever the flip-flop B moves from minimum
to maximum output.
The resetting contact is the only contact 120 in the system and could
if necessary be replaced by a movable core reactor.
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