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1. * GB785468 (A)
Description: GB785468 (A) ? 1957-10-30
Preparation of fluid polyvalent metal phenates
Description of GB785468 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
COMPLETE SPECIFICATION
Preparation of Fluid Polyvalent Metal Phenates
We, THE LUBRIZOL CoRPoRATroN, a corporation organized and existing
under the laws of the State of Ohio, United States of
America of Lakeland Boulevard, Wickliffe, in the State of Ohio, 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 fluid polyvalent metal phenates, and to a
novel process by which these may be prepared. The solubility
characteristics of these compounds render them useful as additives in
lubricating compositions. The additives which are the products of this
novel process are polyvalent metal salts of phenolic organic
compounds, which phenolic compounds contain a total of at least 10
carbon atoms. Preferred are alkyl phenols wherein the substituent
alkyl group or groups on each benzene nucleus contain a total of at
least 10 carbon atoms.
The preparation of zinc and magnesium salts of high molecular weight
alkylated phenolic organic compounds has been accom- plished most
conveniently in the past by means of processes which yielded solutions
of these salts in organic solvents such as; e.g., alcohols. In the

2. case of zinc salts of these compounds, the preparation has generally
been effected by means of a double decomposition reaction involving
the sodium salt of the alkylated phenolic organic compound and a zinc
salt such as zinc chloride. This double decomposition is carried out
conveniently in an organic solvent such as methanol or butanol and
sodium chloride is precipitated, leaving an organic solution of the
zinc salts of the alkylatex phenolic organic compounds, their
preparation has generally been effected by means of reaction of the
alkylated phenolic organic compound with a magnesium alcoholate
dissolved in the same organic solvent. The organic solvent is usually
an alcohol. Again this yields an organic solution of the desired salt.
Isolation of these salts from their organic solutions has been
accomplished by concentration of the solution by distilling the
solvent therefrom. This process is notably inconvenient because of the
extreme viscosity of the residue from said concentration. The residue
is so viscous as to be unfilterable and generally quite unmanageable.
In addition, the residual magnesium or zinc salt frequently is
heterogeneous and tends to agglomerate into lumps. Furthermore, the
salt prepared in this fashion frequently is not permanently soluble,
if at all soluble, in the mineral oil in which it is intended for use
as an additive.
Prior art workers have attempted to solve these problems by
incorporating solubilizing agents and substantial proportions of inert
solvents such as mineral oils. However, such attempts have not been
uniformly successful and have the disadvantage of reducing the
concentration of the product. The process of the present invention
requires neither solubilizers nor inert solvents for its success and
can be carried out in such a manner as to yield a concentrated
product.
It is accordingly a principal object of this invention to provide a
novel process for the preparation of polyvalent metal salts of high
molecular weight phenolic organic compounds. It is another object to
provide such a process whereby the above products are prepared in a
homogeneous relatively nonviscous, and permanently oil-soluble form.
Other objects will be apparent from the details of the ensuing
description.
In accordance with the principles of the invention the process of
isolating polyvalent metal salts of high molecular weight alkylated
phenolic organic compounds from solutions in organic solvents has been
improved such that products of improved fluidity and oil-solubility
are readily available therefrom.
Broadly stated, the invention relates to a method for producing a
fluid, oil-soluble polyvalent metal salt of a phenolic compound, which
phenolic compound contains a total of at least 10 carbon atoms, which

3. process comprises the steps of: -
(a) preparing a solution of a polyvalent
metal salt of the phenolic compound in
a mixture containing a volatile organic
solvent having a boiling point less than
1700 C., in which said salt is stable;
(b) evaporating a major proportion of the
volatile organic solvent from such solu
tion at a temperature below the decom
position temperature of said polyvalent
metal salt; and
(c) reacting with the resulting material
from G.1 to 2.5 moles of water p.r mole
of polyvalent metal salt present.
The polyvalent metal salts referred to above include chiefly the
magnesium and zinc salts.
Other polyvalent metal salts are likewise considered within the scope
of this invention and such salts include the barium, calcium, stron-
tium, manganese, cadmium, aluminium, lead iron and cobalt salts
although the magnesium and zinc salts are preferred.
Phenolic organic compounds may be defined as including all organic
compounds having at least one hydroxyl group attached directly to a
benzenoid carbon which may be part of a single or fused ring, and
which compounds may or may not have other substituents on the
benzenoid nucleus. However, it is preferred to utilize such phenolic
organic compounds which have but one phenolic hydroxyl group; i.e., a
hydroxyl group which is attached directly to a carbon atom of a
benzenoid nucleus. Thus phenolic organic compounds include such
compounds as alkylated phenols and naphthols, and their substitution
products, such as chlorinated phenols, chlorinated naph- thols and
phenol sulfides. Such phenolic organic compounds, as utilized in the
process of this invention, will generally also have pr sent within
their molecular structure at least one aliphatic chain. For reasons of
oil-solubility, such aliphatic chain substituents should preferably
contain a total of at least about 10 carbon atoms, and in the
preferred instance at least about 20 carbon atoms. Usually the total
number of carbon atoms in such aliphatic substituents will not be more
than 3G, although they may contain as high as 60 carbon atoms.
Preferably, the aliphatic chain substituents are hydrocarbon in
nature, and most usually alkyl groups, because of their ready
availability, however, other aliphatic substituents are suitable, for
example, alkoxy groups. In many instances the hydrocarbon chain is
derived from a polyisobutylene, and it is preferred to utilize an
alkylated phenolic compound which contains at least one polyisobutyl

4. radical derived from a polyisobutylene having an average molecular
weight of 250-- 350. Polyisobutylene fractions within the average
molecular weight range are available from the Indoil Chemical Company
under the
trade name "Indopol L-10", stated to have a molecular weight of 300
330. Phenolic compounds containing at least one octadecyl substitusnt
are suitable starting materials.
Broadly speaking, the volatile organic solvent may be any volatile
organic solvent having a boiling point less than 170" C. in which the
polyvalent metal salt of the phenolic organic compound is soluble
without decom-position. Suitable solvents would include, e.g.,
hydrocarbon solvents and oxygen-bearing solvents such as ketones and
aldehydes as are not reacted with phenolic compounds, ethers, esters
and alcohols. By virtue of their cheapness and suitability, alcohols
are preferred for the purposes of this invention.
The nature of the alcohol used in preparing a solution of the
polyvalent metal salt of the phenolic organic compound is of some
importance. In view of the fact that removal of the alcohol from the
reaction mass by evaporation is necessary, low-boiling or low
molecular weight C:C alcohols are preferred. Thus, such alcohols as
methyl, ethyl, 72;propyl, isopropyl n-butyl, sec-butyl, is butyl,
tert-butyl, n-amyl, isoamyl and 2-methyl pentyl-4 are illustrative.
The step of concentrating the process mass comprising alcohol and a
polyvalent metal salt of a phenolic organic compound is accomplished
by evaporation for a period of time sufficient to remove a major
proportion of alcohol. Usually the alcohol will be distilled from the
solution until no more distils.
An additional period of heating at diminished pressure will remove
some more alcohol. The time required for removing this alcohol will be
usually at least ( > .25 hours, and more usually at least 0.5 hours.
At this point the concentrated mass is a viscous, oil-insoluble and
generally unworkable material. It cannot be filtered and it frequently
is of a lumpy consistency. The addition of a small quantity of water
transforms this viscous, oil-insoluble, lumpy mass into a permanently
oil-soluble, homogeneous liquid. Filtration of the material after
water treatment is rapid and convenient.
The manner in which the water-treatment operates to improve the
physical properties of the above-described metal salts is not known.
It is quite possible that a portion of the alcohol is bound in some
way to the polyvalent metal phenate and that the addition of water
releases this bound alcohol. In such a case the high viscosity and
oil-insolubility would appear to be causes by said bound alcohol.
although this phenomenon n is not understood.
The amount of water r which may be used in the process described

5. herein is a significant factor in the optimum operability thereof.
Although the addition even of a trace of water has a ncticeably
beneficial effect upon the physical properties of the polyvalent metal
phenates, it is necessary to add at least an amount which is
equivalent to 6.10 mole per mole of the polyvalent metal present as
the salt. In the usual practice of the invention, one mole of water is
used per mole of polyvalent metal salt. It is necessary not to us an
excessive amount of water in view of the observation that such an
excessive amount appears to decompose the polyvalent metal phenate and
amounts of water in excess of 2.5 moles per mole of polyvalent metal
must be avoided.
The process mass containing alcohol and magnesium salts of phenolic
organic compounds are prepared usually by reaction of a particular
magnesium alcoholate with the phenolic organic compound in the
presence of the corresponding alcohol. The resulting reaction mixture
is then available for utilization as in the second step of the process
described he rein.
Mixtures of alcohol and zinc salts of phenolic organic compounds are
prepared usually by a double decomposition reaction of zinc chloride
with an alcohol solution of an alkali metal salt of the particular
phenolic organic compound. The resulting reaction mixture is filtered
to remove solid alkali metal halide and the filtrate is available for
use in the second step of the process of this invention.
Mixtures of various polyvalent metal salts of alkylated phenolic
organic compounds may be prepared according to the process whereby an
alcoholic solution of a mixture of polyvalent metal salts of alkylated
phenolic organic compounds is concentrated and then treated with
water. The metal salt may be a map nesium and zinc salt.
It has been observed furthermore that the process of water-treatment
is applicable not only to the normal, or neutral polyvalent metal
salts, but also to the basic salts as well.
In some instances, it may be convenient to carry out the process in a
stepwise manner by first preparing the normal metal salt of the
alkylated phenolic orgariic compound, treating it with water, adding
an excess of the desired metal alcoholate thereto, and treating with
water a second time. In other instances, the basic metal salt of the
alkylated phenolic organic compound may be first prepared and then
treated with water.
The following examples serve to illustrate the invention in more
specific detail.
The following process illustrates the result obtained omitting the
water treatment step of this invention. The product is unsatisfactory:
Magnesium methylate was prepared by adding 9.75 grams (0.4 mole) of
magnesium in half gram portions to 180 ml. of refluxing methanol The

6. addition required an hour, after which 283 grams (0.8 mole) of metal
phenol and 438 grams of mineral oil was added and the whole was heated
at reflux temperature for 1.5 hours. Methanol was removed by heating
to a final temperature of 85" G at diminished pressure (water
aspirator). The residue was a very viscous oilinsoluble liquid and
could not be filtered satisfactorily.
The following examples illustrate the proS cess of the invention :
EXAMPLE 1
One mole of magnesium methylate in methanol was prepared as above and
heated at reflux temperature for 1.5 hours with 884 grams (2.0 moles)
of actadecyl phenol and 908 grams of mineral oil. The resulting
mixture was concentrated by heating to a final temperature of 750 C.
at diminished pressure (water aspirator). The residue was quite
viscous A 228-gram sample was heated with 2.0 grams of water at 135"
C. for 35 minutes.
The resulting product was much less viscous.
could be filtered easily and was oil-soluble.
Further experiments with the remainder of the residue obtained above
indicated that while 0.25 mole of water per mole of magnesium
methylate had a slight beneficial effect on the viscosity, 0.5 mole of
water per mole of magnesium methyl ate had a very appreciable effect.
EXAMPLE 2
To one mole of magnesium methylate in methanol prepared as in Example
1, there was added 1084 grams (2.0 moles) of polyiso-
butyl-substituted phenol (containing an average of 32 aliphatic carbon
atoms per molecule) and 1108 grams of mineral oil and the resulting
mixture was heated at reflux temperature for 1.5 hours. The methanol
was removed by heating to 750 C. at diminished pressure (water
aspirator) yielding as a residue a thick, viscous liquid which could
not be filtered conveniently. Treatment of this mass with 10 grams
(0.55 mols) of water resulted in a fluid, easitv filterable,
non-viscous, oil-soluble product.
EXAMPLE 3
To 1.14 moles of magnesium methylate in methanol prepared as in
Example 1, there was added 820 grams (2.28 moles) of dodecyl phenol
and 1267 grams of mineral oil and the whole was stirred at reflux
temperature for 1.5 hours. Thereupon methanol was removed by
distillation at reduced pressure to yield a liquid residue of such
viscosity that the g]ass stirrer was broken. Addition of 10 grams of
water caused a marked reduction in viscosity such that the product
could be filtered with ease. The filtrate was fully oil-soluble.
The "reduced pressure" specified in
Examples 1, 2 and 3 is achieved by means of a water aspirator, so that
pressure is of the order of 15-25 mm. of mercury.

7. EXAMPLE 4
A mole of water-treated magnesium octadecyl phenate was prepared as in
Example 2 and added to a mole of magnesium methylate in 145 ml. of
methanol. This mixture was heated at reflux temperature for 1.5 hours,
then concentrated by heating to 60 C./50 mm. The residue, which
weighed 871 grams, was treated with 4.0 grams (.22 mols) of water to
yield a fluid, clear, oil-soluble product which, upon analysis, was
found to contain twice the amount of magnesium present in the normal
magnesium octadecyl phenate.
EXAMPLE 5
Two moles of sodium methylate was prepared by adding the theoretical
amount of sodium metal to 620 ml. of methanol, and then mixed with 714
grams (2.0 moles) of octadecyl phenol and 1168 grams of mineral oil.
This mixture was heated at reflux temperature for 1.5 hours. To this
mixture was added a solution of 136 grams (1.0 mole) of zinc chloride
in 300 ml. of methanol and the resulting mixture was heated at reflux
temperature for 1.5 hours, and then concentrated to a viscous mass by
heating to a final temperature of I20 C./30 mm. Nine grams (.5 mols)
of water was added and the product again heated to 121)" C./20 mm.
then filtered through "Hyflo" (Registered Trade Mark).
The filtrate was clear, fluid and oil-soluble.
EXAMPLE 6
Sodium methylate was prepared by the portionwise addition of 6.9 grams
(0.3 mole) of sodium to 93 ml. of methanol and then mixed and heated
at reflux temperature for 1.5 hours with 510 grams (0.3 mole) of
polyisobutyl-substituted phenol and 778 grams of mineral oil.
To this mixture was added a solution of 20.5 grams (0.3 equivalent) of
zinc chloride in 300 ml. of methanol and the resulting mixture was
heated at reflux temperature for 1.5 hours.
The product was concentrated to a viscous mass by heating to 1200
C./38 mm. and this residue after treatment with 5.9 grams (.33 mols)
of water, was again heated to 125 C./ 38 mm. The non-viscous material
was filtered through "Hyflo" (Registered Trade
Mark) to yield an oil-soluble, fluid product.
EXAMPLE 7
To sodium methylate prepared hy the portionwise addition of 7.7 grams
(0.33 mole) of sodium to 103 ml. of methanol there was added 561 grams
(1.0 mole) of polyisobutylsubstituted phenol and the mixture was
heated for 1.5 hours at reflux temperature. To this mixture was added
a solution of 22.7 grams (0.33 equivalent) of zinc chloride in 150 ml.
of methanol and the whole was heated at reflux temperature for 1.5
hours. Excess methanol was removed by distillation and final heating
to 1200 C./38 mm. To the viscous residue was added a solution of
magnesium methylate (0.67 equiavlent) in 150 ml. of methanol and this

8. mixture was heated again at reflux temperature for an additional 1.5
hours, then concentrated to a viscous residue by heating to a final
temperature of 1100" C./ 3z mm. Nine grams (.5 mols) of water was
added to this residue and it was again heated to 1200 C./35 mm. The
material was filtered through Hyflo (Registered Trade Mark) to yield a
non-viscous filtrate which was oilsoluble. It contains both the
magnesium and zinc phenates of polyisobutyl-substituted phenol.
The polyisobutyl - substituted phenols employed in Examples 2, 6 and 7
may be prepared by alkylation of phenol with a low molecular weight
polymer of isobutylene. The alkylation step may be carried out at
temperatures within the range of 50100 C. and it requires the presence
of a Friedel-Crafts catalyst such as aluminium chloride or activated
clay.
What we claim is:-
1. A method for producing a fluid, oilsoluble polyvalent metal salt of
a phenolic compound, which phenolic compound contains a total of at
least 10 carbon atoms, which process comprises the steps of: -
(a) preparing a solution of a polyvalent
metal salt of the phenolic compound in
a mixture containing a volatile organic
solvent having a boiling point less than
1700 C., in which said salt is stable;
(b) evaporating a major proportion of the
volatile organic solvent from such solu
tion at a temperature below the decom
position temperature of said polyvalent
metal salt; and
(c) reacting with the resulting material
from 0.1 to 2.5 moles of water per mole
of polyvalent metal salt present.
2. A method in which the volatile organic salvent is an alcohol.
3. A method as claimed in Claim 2 in which the alcohol is one of less
than 8 carbon atoms.
4. A method as claimed in Claim 1, 2 or 3, in which the evaporation is
carried out until a viscous material results.
5. The process of Claim 1, 2, 3 or 4, further characterised in that
said phenolic compounds contain at least ten aliphatic chain carbon
atoms per benzene nucleus.
6. The process of Claim 1, 2, 3 or 4, further characterised in that
said phenolic compounds contain at least one aliphatic substituent
having an average of from 10 to 60 carbon atoms.
7. The process of Claim 1, 2, 3 or 4, further characterised in that
said phenolic compounds contain at least one aliphatic substituent
having an average of 20 to 30 carbon atoms.

9. 8. The process of Claim 1, 2, 3 or 4 further characterized in that
said phenolic compounds contain at least one aliphatic hydrocarbon
substituent having an average of from 10 to 60 carbon atoms.
9. The process of Claim 1, 2, 3 or 4 further characterized in that
said phenolic compounds
* GB785469 (A)
Description: GB785469 (A) ? 1957-10-30
Improvements relating to apparatus for testing electrical components
Description of GB785469 (A)
COMPLETE SPECIFICATION
Improvements relating to apparatus for Testing Electrical Components.
We, STEATIT MAGNESIA AKTIENGESELLSHAFT, a Body Corporate organised
under the laws of Germany of Lauf/Pegnitz, Germany, 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 electrical apparatus for use in the
measurement of the
Q or inductance of a coil or the Q or permeability of a core for a
coil.
There have been previous proposals for the measurement of these
quantities according to which the component in question formed part of
a resonant measuring circuit which also included a variable capacitor
and which was energised with a signal of constant frequency. The
capacitor was varied until the measuring circuit came into resonance
with the constant frequency signal. This required a mechanical tuning
of the capacitor before the measurement could be made. In order to
shorten the time required for the tuning, it has been proposed to
obtain semi-automatic operation by employing special mechanisms to
drive the capacitor. These special mechanisms are then made to be
responsive to the resonant frequency and the test circuit.
Such arrangements, however, are still timeconsuming and rather
expensive.

10. The object of the present invention is to reduce these disadvantages
by providing apparatus which enables tests to be carried out in a very
short period of time and which can therefore be adapted to
mass-production techniques.
According to the invention, the apparatus includes a resonant circuit
adapted to include the inductor to be tested or an inductor containing
the core to be tested, a variable frequency generator the output of
which is applied to the resonant circuit, a comparison circuit
arranged and adapted to compare the resonant frequency of the resonant
circuit with the frequency of the generator output and to provide an
output representing the difference in the two frequencies, and first
and second control means controlled by the comparison circuit output,
one of the control means being adapted to increase and the other to
decrease the frequency of the generator, to bring the latter
substantially into coincidence with the resonant frequency of the said
circuit, the first control means being operative only when the output
of the comparison circuit is above a predetermined value at which the
compared frequencies are substantially equal and the second control
means being operative only when the said output is below the
predetermined value.
In the preferred embodiment oiE the apparatus, two electronic valves
serving as the above-mentioned first and second control means are
arranged to vary the charge on a capacitor connected to a control
electrode of a reactance valve which controls the frequency of the
generator. The test circuit may be either a series resonant circuit or
a parallel resonant circuit. Sorting devices may be arranged to place
the measured inductors or cores in different containers according to
their Q values, inductances, or permeability values
The invention will be explained, by way of example, with the aid of
the accompanying drawings, in which:
Fig. 1 is a circuit diagram of a device embodying the invention; and
Fig. 2 is a more detailed circuit diagram of the device according to
Fig. 1.
The device according to our invention comprises a variable high
frequency gener- ator 1 which, as shown in Fig. 2, may consist
essentially of an oscillatory circuit 14 and three valves 15, 16, 17.
The high frequency voltage generated in the oscillatory circuit 14 and
valve 15 is amplified by the
tao valves 16 and 17, and the amplitude of
t"e output voltage of the generator 1 is
held constant by means (not shown) well
l:nown to those skilled in the art.
The frequency of the variable high fre
quency generator 1 may be adjusted by a

11. reactance valve 2, but the output voltage of
the varible high frequency generator 1 re
mains constant. Valve 2 can affect the varle high frequency generator
1 as either a
capacitance or an inductance. In the em
bodiment illustrated in the figures, valve 2
is used as an inductance. The value of the
reactance presented by the valve 2 is varied
by varying the charge on a capacitor 3 con
nected to a control electrode of this valve.
The output voltage of the variable high
frequency generator 1 is applied to a res
onant test circuit 4 by means of a capaci serve voltage divider as
shown in the draw inns.
The resonant test circuit 4 consists of the
inductance Lx to be measured and a vari
able condenser CK (Fig. 2). The voltage
across the resonant test circuit 4 at reson
ant frequency is a measure of the Q value
of the inductance Lx, if the losses within
the capacitances of the resonant test circuit
4 are low. This method is well known to
those skilled in the art.
The fine tuning of the frequency of the
variable high frequency generator 1 to
bring it into agreement with the resonant
frequency of the test circuit 4 is effected
automatically, for which purpose the high
frequency voltage output of the test cir
cuit 4 is applied to a comparison circuit or
discriminator7. In this discriminator 7
(Fig. 2) the high frequency output voltage
from the test circuit is applied through a
small capacitor 18 to a two-stage amplifier
which comprises the valves 19 and 20 and
which simultaneously operates as a limiter
so that amplitude changes in the ratio of
1:100 are equalised. The frequency of the
signal from the resonant test circuit 4 and
he frequency of the signal from the high
frequency generator 1 are then compared in
a multi-grid valve 21, for example. the non
ode known as the Philips Enneode EQ 80.
As shown in Fig. 2, the signals to be com

12. cared are applied to the third and fifth
grids, the first grid being maintained at a
.ted potential. The valve 21 generates
across its anode load a D.C. voltage which
varies in accordance with the phase differ
ence between the two signals.
The output of the phase discriminator is
applied to the control grid of one of a pair
^se cathode-coupled triodes 22 which act as
a longtailed pair and which provide at
their tiro anodes voltages which vary in
0,W3site senses in a balanced manner in
response to the voltage from the phase disScum nator. The voltages at
the anodes of the double triode 22 are applied to the control grids of
two further triodes 5 and 6 which act as electronic switches. The
cathode resistor 8 of the triode 6 and the anode resistor 9 of the
triode 5 are connected together at their ends remote from the triodes
and their junction is connected to the upper plate of the capacitor 3,
the upper plate of which is normally charged negatively by a source of
negative voltage (not shown).
When the frequency of the generator I is equal to the resonant
frequency of the circuit 4, the voltages at the grids of the two
triodes 5 and 6 have values just below the cut-off values for these
two valves. As a result, neither of these valves is conducting.
If a difference develops between the two fre quencies in such a
direction that the grid voltage of triode 6 is raised above the cutoff
level, the voltage at the upper plate of capacitor 3 will be less
negative than in the case when both triodes 5 and 6 were
nonconducting. As a result of this less negative charge, the reactance
presented by the valve 2 changes in such a direction that the
generator frequency is altered towards the resonant frequency of the
circuit 4. If the difference between the frequencies is of the
opposite sense, the grid voltage of the triode 5 is raised above the
cut-off level, the triode 5 conducts and the charge on the capacitor 3
is more negative than in the case when both triodes 5 and 6 were
nonconducting. The reactance of the valve 2 changes in the opposite
direction, and again the generator frequency is altered (this time in
the opposite direction) towards the resonant frequency of the circuit
4. The voltages are such that at no time are both the triodes 5 and 6
conducting.
The time response of the circuit is governed by the selected values of
the resistors 8 and 9 and the capacitance 3.
The embodiment of the invention illustrated uses a parallel resonant
circuit for the test circuit 4. However, it could equally well have

13. been a series resonant circuit in which case the discriminator 7 would
have been responsive to the current in the series resonant circuit. In
both cases, the discriminator 7 responds to a difference in frequency
between the resonant circuit frequency and the input frequency by
rendering conducting either valve 5 or valve 6, according to the
direction of the frequency difference.
A voltage-measuring device 10. serving as a Q-meter, can be placed in
a circuit to monitor the voltage across the parallel circuit, The
Q-meter 10 is as usual a valve voltmeter, which is calibrated in
values of O. The Q-meter 10 can be connected to a sorting device 11 so
that the latter will be energised in accordance with the peak voltage
appearing at the voltage-measuring de
sice 10 and will place the measured induct
ance Lx into a bin depending upon its
t.Leasuled Q. The voltage on the cathode
resistor 23 of the valve 24 controls the volt
age at the cathodes of the two thyratrons
26 aud 27 by means of a double triode 25,
he voltages at the grids of the thyratrons.
being such that with decreasing cathode
voltage one of the thyratrons fires before
the other. The anode circuits of the thyra
trons 26 and 27 include relays 28 and 29
respectively, by means of which the induc
tor to be measured is dropped into a bin
which is selected according to the Q value
of the inductor. With only one thyratron
conducting the component is dropped into
an "acceptable" bin; with neither or both
conducting it is dropped into another bin or
other bins.
Similarly, a frequency-measuring device
13 can be used to energise a second sorting
device 12 in which the measured induct
ance Lx can be sorted according to its in
diuctance. The signal from the generator 1
is applied to the oscillatory circuits 30 and
31 in the frequency-measuring device 13.
These circuits contain variable capacitors
which enable their resonant frequencies to
be adjusted. The output signals from the
oscillatory circuits 30 and 31 are rectified
and are used to control two thyratrons in
the sorting device 12, the thyratrons con

14. taining relays 33 and 32 in their anode cir
cuits. The sorting device is operative after
the adjustment of the generator frequency
by means of the reactance valve 2. The
resonant frequency circuit 30 is adjusted to
such a value that its rectified output is
sufficient to render the associated thyratron
conducting only when the value of the in
ductance Lx is below a predetermined
value. Relay 33 is then operated to drop
the inductance into a selected bin. Simi
larly, circuit 31 is adjusted so that the as
sociated thyratron is rendered conducting
and relay 32 is - operated only when the
value of the inductance Lx is above a pre
determined value, in which case the induct
ance is dropped into a further bin.
The operation of the circuit is as follows:
the constant-voltage variable-frequency
generator 1 supplies a signal of given fre
quency to the parallel resonant circuit 4.
The instantaneous frequency of the gener ator 1 and the resonant
frequency of par
allel resonant circuit 4 are compared in dis
criminator 7. The difference between these
fre4uencies appears in the relative phase
angles of the two signals. This frequency difference is converted in
the discriminator
7 into a direct voltage, which is used to
cause the energisation of either valve 5 or
valve 6, whereby the condenser 3 is charged
to a more or less negative potential, assum
i ing the operating point of tube 2 to lie in the negative range of
its characteristic curve.
This potential is then applied to the grid of the valve 2 so as to
effect a fine adjustmeut of the frequency of the variable frequency
generator 1. With this change made in the frequency of generator 1,
discriminator 7 again compares the difference between the
instantaneous frequency of generator 1. and the resonant frequency of
resonant circuit 4, and this result is used to effect further fine
tuning of the generator 1.
This process continues until the frequency of generator 1 exactly
matches the resonant frequency of circuit 4, at which time both valves
5 and 6 are cut off. The potential of condenser 3 and the generator

15. frequency remain constant, and no further tuning takes place.
It should be notcd that this fine tuning takes place at a speed which
corresponds to the time constant of the condenser 3 and
the resistors 8 and 9 of tubes 6 and 5 res
pectively. This time constant can be made to be only a few tenths of a
second, for
which value the tuning can be considered to take place substantially
instantaneously,
having regard to the time usually required for tuning in measuring
circuits of this
type.
What we claim is : -
1. In a device for measuring the Q or the
inductance of an inductor or the Q or permeability of a core for an
inductor, appar- atus including a resonant circuit adapted to include
the inductor to be tested or an inductor containing the core to be
tested, a variable frequency generator the output of which is applied
to the resonant circuit, a comparison circuit arranged and adapted to
compare the resonant frequency of the resonant circuit with the
frequency of the generator output and to provide an output
representing the difference in the two frequencies, and first and
second control means controlled by the comparison circuit output, one
of the control means being adapted to increase and the other to
decrease the frequency of the generator to bring the latter
substantially into coincidence with the resonant frequency of the said
circuit, the first control means being operative only when the output
of the comparison circuit is above a predetermined value at which the
compared frequencies are substantially equal and the second control
means being operative only when the said output is below the
predetermined value.
2. Apparatus according to Claim 1, including a reactance valve
arranged to vary the frequency of the generator, the reactance of the
reactance valve being varied in opposite senses by the first and
second control means so that the frequency of the gen
* GB785470 (A)
Description: GB785470 (A) ? 1957-10-30

16. Improvements in or relating to load supporting props
Description of GB785470 (A)
PATENT SPECIFICATION
Inventors:-ERNEST DONALD MERTON GULLICK, WILFRED ALLSOP and FRANK
COWLISHAW.
Date of filing Comvplete Specificationg: Feb 7, 1956.
Application Date: Feb 14, 1955 No 4341/55.
Complete Specifcation Ptblish 7 ed: Oct 30, 1957.
Index at Acceptance:-Class 20,2), E 2 (B: X).
International Classification:-Ewld.
COMPLETE SPECIFICATION.
Improvements in or relating to Load Supporting Props.
We, W E & F DOBSON LIMITED, a British Company, of Arnold Road,
Basford, Nottingham, 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 is concerned with improvements in or relating to load
supporting props and is particularly concerned with load supporting
props for use in underground mines for the support of the roof.
It will be appreciated that as material is mined and removed it is
necessary to support the roof and due to blasting and to removal of
the mined substance the roof is unstable in the sense that parts of it
may be or tend to become disposed at a slightly lower level than other
parts, some.
times accompanied by a lateral or twisting movement of the roof.
Furthermore after a certain section of the roof has been supported by
a column the roof may twist or move such that the prop becomes itself
subjected to twisting or bending moments between the roof engaging
point and the ground engaging point.
It will be appreciated that if the roof surface is parallel to the
floor surface a prop comprising a roof engaging plate and a ground
engaging plate firmly secured normal to a load supporting column is
interposed between the roof and the ground then the whole of the
downward stress from the roof to the ground is transmitted normally
through the two plates and along the central axis of the load
supporting column However, if after insertion of the prop the roof
moves such that its surface is no longer parallel to the ground, but
inclined at an angle thereto the roof supporting plate and / or lPrice
3 s 6 d l the ground engaging plate are obliged to adopt an angle
relative to the column and the column itself may be forced to adopt an

17. angle other than normal to the ground.
Additional stresses are therefore imposed upon the various parts of
the prop which may tend to fracture the column and its associated
parts or alternatively reduce its efficiency as a roof support
Furthermore difficulty is often encountered in endeavouring to remove
props which have been jammed by movement of the roof after insertion
thereof.
It is an object of the present invention to provide improvements in
load supporting props and particularly to provide improvements in load
supporting props for the support of roofs in underground mine
workings.
With the above and other objects in view the invention provides a load
supporting prop comprising a load supporting column having a load
supporting plate located at one end and a base plate at the other end
and wherein at least one of the said plates is located to the column
by a ball and socket joint The provision of a ball and socket joint
enables the plate to have universal movement relative to the column.
Preferably a ball and socket joint is provided at both ends of the
column so that both the load supporting plate and the base or ground
engaging plate is provided with universal movement relative to the
column.
Means are preferably provided for maintaining the Dlate normal to the
column and such means may for example comprise a coil spring secured
to the plate and encircling the column Alternative means may comprise
a resilient member encircling the column at a point spaced from the
ball and ' '' loa 'IS: 2 Price af 785,470 so F'' 785,470 socket
connection and secured to the plate by suitable means such as for
example by the provision of a frame secured to and extending from the
plate and having means for locating the resilient member in column
encircling attitude.
Conveniently the load supporting and/or base plate are releasably
secured relative to the column and preferably the column is extendible
and may for example be extendible by fluid means more particularly and
with reference to the supporting roofs in underground mine workings
the column may be a conventional hydraulically operated support
column.
If desired a plurality of columns may be provided common to one base
plate and to one load supporting plate to provide a greater area of
contact between the load and the ground A roof support according to
the present invention is readily employable with an unstable roof as
aforementioned because of the universal mountings which allow relative
movement between the base plate, the column and the load supporting
plate and therefore avoiding bending or jamming of the extendible
parts of the column.

18. If, when employing a roof support having four columns the roof tends
to incline relative to the base member allowance for the inclination
is taken up by one or other of the columns assuming a leaning attitude
whilst the remaining column or each thereof remains in the vertical
attitude so that the support continues to be stable.
In order that the invention may be more readily understood reference
will now be made to the drawings accompanying the Provisional
Specification in which:-
Figure 1 is a general perspective view of a roof support according to
the invention.
Figure 2 is a diagrammatical part sectional view illustrating the
employment of the support, in exaggerated manner.
Figure 3 is a detail view of mounting and spring means for the
support; and to the drawings accompanying this Specification in which:
Figure 4 is a perspective view of a single column load supporting
prop.
Figure 5 is a cross-section view of Figure 4.
Figure 6 is a cross-sectional view of an a alternative construction of
a part of a load supporting prop according to the present invention.
Figure 7 is a plan view on the line 7-7 of Figure 6.
Figure 8 is a sectional view of part of a load supporting prop of a
further alternative construction.
Figure 9 is an end view in the direction of the arrow 9 of Figure 8.
6 Figure 10 is a sectional view of a load supporting prop having a
still further alternative construction.
Referring now to Figure 1 a roof support for underground mines is
provided comprising a base 1 on which there stands four 70 props 2, 3,
4, and 5 having on the top thereof a top load supporting member 66 The
base 1 and the top member 6 are conveniently square plates with the
four props 2 to 5 being disposed in close group formation 75
registering with the corners of the square.
For locating the props with respect to the base and top member, ball
and socket mountings are provided comprising sockets such as those
shown at 7, 8 and 9 on the So base 1 and those shown at 10, 11 and 12
on the underside of the top member 6, and balls such as those shown at
13, 14 and 15 engaging in the sockets 7, 8 and 9 respectively, and
balls 16, 17, 18 engaging in 85 sockets 10, 11, 12 respectively.
Each prop and at least its associated base are connected together by
spring means such for example as that shown comprising a tapered
spring 19, 20, 21 or 22 coiled 90 round the lower end of the prop with
its wide end lowermost and fixed, by welding, to the top side of the
base 1 and with its narrower upper end closely encircling the prop at
an elevated location from the base 95 Conveniently the wide end of the
spring encircles the adjacent socket on the base.

19. If desired as shown in Figure 1 each prop may have, in addition to or
in lieu of the aforementioned springs 19 to 22, a similar 100 spring
23 at the top end and disposed in inverted manner to connect the prop
and top member together The spring means preferably biases the base
and the top member, on the one hand, and the prop, on 105 the other
hand, into relatively perpendicular attitude.
Also if desired, as shown in Figure 3, each prop may be formed with an
annular flange 24 with which the top end of the spring has 110 a screw
engagement as shown.
In a further alternative (not shown) there is a plurality of springs
for each prop, the springs being anchored to the base, or top member,
at snaced locations around the 115 appropriate end of the prop and the
other ends of the springs being attached to the prop at a convenient
location from the base along its length.
Each prop may be of a kind which is 1210 extendible, by yirtue
of-being formed by a lower part 2 a to 5 a which is hollow and an
upper part 2 b to 5 b which engages in the part 2 a to 5 a in piston
and cylinder-like manner, fluid pressure means being pro 125 vided for
controlling the extending action of the piston parts 2 b to 5 b.
In Figures 4 and 5 a square base plate is comprised of a ground
engaging plate 1 having a peripheral upstanding flange 30 13 o it is
in engagement with the resilient member 52 and then by relative
rotation of the disc 51 and the webs 50 it may be located in position
in slots 54 provided in the webs 50.
Figure 10 illustrates a prop having in combination the load supporting
member illustrated in Figures 8 and 9 and the base support arrangement
illustrated in Figures 6 and 7 and illustrates the movement from the
normal permitted between the part 26 and the part 25 and the load
supporting member.
If desired the foregoing construction for locating the load supporting
plate and/or base plate relative to the load supporting column may be
employed in combination with a plurality of load supporting columns
common to one base plate and one load supporting plate.
If or when the roof resumes the position parallel to the ground, the
relative parts of the columns will be returned to their normal
position.
In use in underground mine workings it is sometimes possible to
predict movement of the roof in a certain direction and where such
predictions are made it is possible to insert a prop in position such
that it is inserted with the load supporting column at an angle so
that after movement of the roof the load supporting column is
substantially normal to the ground and/or the roof.
reinforced by webs 31 A flange 32 having an aperture 33 is located in
one side of the base plate.

20. A load supporting plate 6 is provided at the other end of a load
supporting column comprised of two parts 25 and 26 relatively
extendible along the central axes thereof.
The lower end 37 of the part 26 is hemispherically shaped and engages
with a hemispherical socket provided in a bush 36 located in the
centre of the base plate 1.
A coil spring 27 encircles the part 26 and is secured at its lower end
to the base plate 1 by clamp brackets 29 located on the webs 31.
The upper end (not illustrated) of the part is similarly hemispherical
so that it engages a similar hemispherical socket in the load
supporting plate 6 The coil spring 28 encircles the part 25 and serves
to locate the load supporting plate 6 relative to the part 25 and
normal to the central axis thereof.
It will be appreciated that when the prop illustrated in Figures 4 and
5 is placed in load supporting position the load supporting plate 6 is
able to move relatively to the part 25 and the parts 25 and 26 are
able to move relatively to the base plate 1, due to the universal
movement allowed by the hemispherical end faces of the parts 25 and 26
and their respective sockets.
In Figure 6 the hemispherical end 37 is located in the hemispherical
socket 36 and an annular ring 38 spaced from the part 26 encircles the
socket A square frame comprised of four members 39 is secured to the
base plate 1 extends upwardly therefrom.
An apertured member 41 spaced a distance from the free ends of the
frame member 39 is secured thereto An apertured resilient member in
the form of a corrugated ring 42 encircles the part 26 and is
supported by the member 41 and secured thereto by 4.5 a further
apertured member 40 by bolts 43.
The part 26 therefore is held normal to the base plate 1 by the
resilient member and yet is permitted movement at an inclination
thereto by the corrugated resilient ring 42.
In Figure 8 the part 25 is provided with a hemispherical end face 44
which engages in a hemispherical socket 45 secured to the plate 46
which carries side flanges 47 and supports a load supporting bar 48 A
aa circular sleeve 49 is secured to the underside of the plate 46 and
encircles the socket 45.
A resilient sleeve 52 encircles the part 25 and is located within the
sleeve 49 The resilient sleeve 52 is held in position by an apertured
disc 51 having radially spaced slots 53, at the circumference thereof
which are able to slide down webs 50 secured between the flanges 47
and the sleeve 49 By bringing the slots 53 in to register with the
webs 50 b 5 the plate may be slid along the part 25 until
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* GB785471 (A)
Description: GB785471 (A) ? 1957-10-30
Improvements in or relating to the control of electrically operated switch
frogs in overhead electric traction systems
Description of GB785471 (A)
PATENT SPECIFICATION 7 k
Inventors 8:-ALBERT SEPHTON and ALBERT EDWARD WRIGHT.
Xfe, of tiitg Coinplete Specificalion: Feb 15, 1956.
mppl ca Dialp lat: Feb 15,1955 Yo 4501 /55.
C'om;tlete,Specificatiot Pablished Oct 30 1957.
Index at Acceptance:-Class 104 ( 3), A 2 B 3.
International Classification:-B 6 lm.
COMPLETE SPECIFICATION.
Improvements in or relating to the Control of Electrically Operated
Switch Frogs in Overhead Electric Traction Systems.
We, BRITISH ITNSULATED CALLENDER'S CABLES LIMITED, a British Company,
of Norfolk House, Norfolk Street, London, W.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 overhead electric traction systems of the
kind in which current is supplied to a vehicle from one or more
overhead conductor wires through one or more wheels or slippers which
run along the wires At diverging route junctions of the type generally
known as " turnouts ", to avoid interruption of the supply to the
vehicle, devices known as switch frogs are provided These comprise a
pivotally mounted member or tongue which is movable from a position in
which it provides a path for the collector wheel or slipper from the

22. end of the approach conductor to the neighbouring end of one of the
two departure conductors to a position in which it provides a path for
the collector wheel or slipper from the end of the approach conductor
to the neighbouring end of the other of the two departure conductors
Operation of these switch frogs is usually effected by electromagnetic
means The present invention concerns electromagnetically operated
switch frogs of the kind in which a pair of solenoids are used, one
acting on the tongue to move it in one direction and the other acting
on it to move it in the reverse direction, the operation of these
solenoids being controlled by manually operable switches mounted
alongside the track or roadway or in some other appropriate place It
provides a convenient control circuit incorporating visual indicating
lPrice 3 s 6 d l means for indicating to the driver of an approaching
vehicle the condition of the switch frog or, in the case of trolley
bus systems employing a pair of trolley wires, of the switch frogs.
The control circuit according to the invention comprises a pair of
paths which extend from the same pole of a source of supply to the
other pole of that source.
Each path includes the control winding of a switch controlling one of
the two solenoids of the switch frog, a manually operable switch and
an automatic switch operated by the switch frog, one automatic switch
being in the open position when the other automatic switch is closed
and vice versa At a point between the control winding and the manually
operable switch on the one hand and the automatic switch on the other
hand, each of these paths is connected to the other through a bridging
path including a pair of current-responsive indicating devices and
this bridging path is connected, at a point between the two indicating
devices, to the first said pole of the source of supply.
With the above control circuit, with one automatic switch closed,
current will flow through it and one indicating device but not through
the other With the other automatic switch closed current will flow
through the other indicating device but not through the first device
and this whatever the positions of the two manually operable switches
Closing of one manually operable switch will complete a circuit from
one pole of the supply, through the control winding of one solenoid
control switch and either through the direct path to one automatic
switch and that switch to the other pole of the supply or through the
bridging path and the other automatic switch to the said other Mr'- 27
X 471 785,471 pole of the supply, depending upon which of the two
automatic switches is closed.
This will operate the solenoid control switch complete one solenoid
circuit and, if the switch frog is not already in the position
appertaining to that solenoid, the solenoid will operate and re-set
the switch frog and open the closed automatic switch and close the

23. open one, automatically de-energising one indicating device and
energising the other Closing of the other manually operable switch
will then re-set the frog in its original position and reverse the
indication.
The invention will now be described by way of example with reference
to the accompanying drawing which is a wiring diagram of a circuit for
the control of a switch frog in accordance with the invention.
The control circuit comprises a pair of paths which extend from the
same pole 1 of a source of supply to the other pole 2 of that source
The first path includes the control winding 3 of a switch 4
controlling a solenoid for operation of the switch frog by move 2 '
ment of a plunger S within the solenoid, a manually operable switch 6,
preferably of the push button type, and an automatic switch 7 operated
by the plunger 8 whiclh is mechanically coupled to the switch frog.
The second path includes a control winding 9 of a switch 10
controlling a second solenoid 11 for operation of the switch frog b Y
movement of the plunger 8 within the solenoid in the reverse
direction, a manually operable switch 12, preferably also of the push
button type, and a second automatic switch 13 operated by the plunger
8 The automatic switch 7 is in the open position -when the aotomatic
switch 13 is closed and vice versaand each switch comprises a contact
member adapted to engage a portion of the plunger of enlarged diameter
in the closed position, the plunger being connected to the pole 2 of
the supply In the drawing the full lines show the switch 13 in the
closed position and the switch 7 in the open position.
The broken lines show the switch 7 in the closed position and the
switch 13 in the open position.
The automatic switches may, if desired, comprise pairs of contacts
which are opened or closed by travel of the plunger and may be
operated, for example, by a cam on the plunger.
At a point between the control winding and the manually operated
switch on the one hand and the automnatic switeh on the other hand
each of the paths is connected to the other through a bridging path
including a pair of current responsive indicating devices 14, 15 and
this bridging path is comnected, at a point between the two indicating
devices, to the pole 1 of the source of supply.
The indicating devees may be lamps which may serve to illuminate one
of two arrows pointing in the directions of the two routes.
In this case the bridging path is connected to the source of supply,
from a point between the indicating devices, through a dropper
resistance 16 70 One terminal of the control switch 4 for the solenoid
5 is connected to the pole 1 of the source of supply while the other
terminal is connected to one end of the solenoid 5, the other end
being connected to the pole 2 of 75 the source of supply Similarly one

24. terminal of the control switch 10 for the solenoid 11 is connected to
the pole 1 of the source of supply while the other terninal is
connected to one end of the solenoid 11, the other end 80 of which is
also connected to the pole 2 of the source of supply.
For the solenoid control switches electromagnetically actuated
contactors may be used but we prefer to use hot wxire vacuum S 5
switches which close in one to four seconds after the energisation of
their control winding.
With the control circuit as above described, closing of one manually
operable -:0 switch when the s-wsitehi frog is already in the position
to which it would otherwise be caused to move by the closing of that
switch, will result in current flowing through the coil of the
solenoid whilst the switch is held 95 closed To avoid the risk of
damage to the coil by overheating as a result of a pro.
longed closure of the manually operable switch in such-circumstances,
we prefer to insert in the bridging path a current limiting i O o
device 17 (for example a non-linear resistor) to limit the current
flowing through the control windings of the switches controlling the
solenoids via the bridging path to a value insufficient to operate the
control switch 1 e 5 The control circuit is also applicable to switch
frogs operated by a pair of solenoids which have separate plungers
each mnechanically coupled to one of the two automatic switches and to
the movable tongue (or i t) tongues) of the switch frog.
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* GB785472 (A)
Description: GB785472 (A) ? 1957-10-30
Improvements in or relating to retort stands for the support of apparatus
Description of GB785472 (A)

25. COMPLETE SPECIFICATION.
Improvements in or relating to Retort Stands for the Support of
Apparatus.
I, WILLIAM BARROW, of B Grand Parade,
Portsmouth, Hampshire, a British Subject, do hereby declare the
invention, for which I pray that a patent may be granted to me, and
the method by which it is to be performed, to be particularly
described in and by the following statement
The invention relates to portable stands for tools, instruments and
other devices but is directed to such stands intended more
particularly for the support of scientific apparatus such as retorts,
burrettes, funnels and the like, which stands are commonly referred to
as retort stands. Throughout the remainder of this Specification the
stands will be referred to as retort stands, but this term must be
understood to cover stands for such other purposes as referred to
above.
An object of the invention is to provide a retort stand which can be
staclred in nested form with other similar stands for economy of space
in storage.
According to the invention a retort stand comprises a substantially
flat base and a rod or post extending in a direction generally normal
to said base, and attached thereto, said base being provided with
three feet projecting from an underside thereof and slots or eut-out
portions adjacent to the feet to accommodate the feet of a similar
stand stacked on said first stand. The post preferably is attached to
the base by means of a block carried by the base, a slot or cut-out
portion being provided in said base adjacent to the block to
accommodate a block of a similar stand on which the first named stand
is staeked.
The invention is illustrated by way of example in the accompanying
drawing, in which :-
Figure 1 is a plan of the retort stand;
Figure 2 is an elevation of the stand; and
Figure 3 is a view similar to Figure 2 showing four retort stands
stacked together.
Referring to the drawing, the retort stand shown comprises a generally
rectangular base 1 to which is attached on an upperside, near one end,
a block 2 forming a fixture for an upright rod or post 3. The latter
is for the attachment of any appropriate supporting member such as a
ring. The block 2 is set inwards from the edge by a suitable distance
as shown in the drawing.
On the underside of the base 1 are fixed two feet 4, one at each end
of a short side of the rectangle. At the opposite short side another

26. foot 5 is fixed to the under side of the base 1. Adjacent to the feet
4 in the long sides of the rectangle there are two slots or cut-out
portions 6 each adapted to receive one foot 4 of a supenmposed retort
stand as shown in Figure 3. Similarly a slot 7 is provided to
accommodate, in the superimposed stand, the block 2 of the stand
therebelow.
The arrangements for stacking are clearly shown in Figure 3. Each foot
4 enters the corresponding slot 6 of the retort stand below, and the
block 2 of any stand enters the slot 7 of the retort stand above,
while each foot 5 overhangs the end of the base 1 below. The staggered
arrangement prevents the several posts 3 from interfering with each
other.
It will be seen that by means of the three feet 4 and 5 the retort
stand will be steady on a surface although it may be uneven.
What I claim is
1. A retort stand comprising a substantially flat base and a rod or
post extending in a direction generally normal to said base and
attached thereto, said base being provided with three feet projecting
from an underside thereof and slots or cut-out portions