Improvements in and connected with Resistances and Switches for Electric Circuits.
Year: 1894

page_text: Date of Application, 21st Nov., 1894
Complete Specification Left, 21st Aug., 1895-Accepted. 5th Oct., 1895
PROVISIONAL SPECIFICATION,
Improvements in and connected with Resistances and Switches for
Electric Circuits.
I, MICHAEL HOLROYD SMITH of 161 Trinity Road, Upper Tooting, in the
County of Surrey, Engineer, do hereby declare the nature of this invention to be
as follows:-
My invention relates to certain improvements in liquid resistance cells and in
switches for, electric circuits.
In carrying out my invention I employ one or more cells having at the bottom
a terminal plate consisting of an annular solid or grooved ring or a ring of some
suitable shape or a tapered or corrugated plate, such plate being preferably of
lead. Upon this plate a movable ring or terminal plate of a shape approximating
thereto adapted to rest and make contact, such plate being capable of a rising
and falling movement in the cell (which may be charged with acidulated water or
other suitable liquid) by means of a cord or suitable flexible connection one end of
which is fast to a fixed point and the other end to the movable plate, the operating
device consisting of a. pulley. over which the cord is passed, said pulley being
carried by a pivoted arm suitably balanced, the arrangement enabling a short lift
of the arm to raise the movable plate to a considerable height through and clear of
the liquid, the amount of which between the two plates determines of course the
amount of resistance placed in the circuit. With the construction of plates or
rings above described any dirt or precipitate in the solution will fall through and
around same so that the contact is not spoiled by any accumulation of matter in or
on same. They further present little resistance to the liquid in raising and lowering,
and in leaving the liquid the formation of a large spark is avoided.
For the purpose of operating the pivoted arm I employ a handle or lever fitting
into a socket on the shaft carrying such arm, said handle or socket engaging with
projections on a fixed segment and being pressed into same by a spring, or having
a spring pawl or catch engaging with same, the object being to enable the handle
to be shifted to and fro, and to be held at any desired point, means being also
provided whereby the handle can, only be inserted or removed when the movable
plate is out of the liquid and the circuit is consequently broken.
In cases where two or more electric motors are employed which it is desired
should be driven either is series or in parallel such as motors employed in the
propulsion of tramcars, I employ what I term a setting switch by which such
motors may be set in series or in parallel as the case may be, the motors when in
parallel developing a higher speed than when in series. Such a switch 1 may
combine with the resistance above described, in the following manner :-
I cause the pivoted arm above described, or an extension of same, to operate a
weighted rod capable of a rocking movement, which rod is attached at its other
end to a crank or otherwise operates a shaft carrying a pair of contact plates on
either side of same and insulated therefrom. This shaft with the plates is capable
of a sliding movement in its bearings, a removable pedal or hand lever being
employed for forcing it in one direction, and a spring for directing it in the other.
The contact plates are adapted to make contact when the shaft is in one position
with two pairs of terminals and complete a circuit by which the motors are set in
series, and when the shaft is rocked so as to break contact and is shifted laterally,
the contact plates will be brought into position to make contact with other

page_text: pairs of terminal plates by which the motors will be set in parallel, means being
provided whereby the lateral movement cannot be effected until the moveable-
plate or ring in the resistance cell is entirely clear of the liquid and the circuit
is broken.
Dated the 21st day of November 1894.
PHILIP M. JUSTICE,
Chartered Patent Agent, 55 & 56 Chancery Lane, London,
For the Applicant.
do hereby declare the nature of this mrvention au in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
My invention relates to certain improvements in liquid resistance cell's and in
switches for electric circuits.
I will describe my invention with reference to the accompanying drawings in
which :-
Fig. 1 is a sectional elevation of the resistance.
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Fig. 1 is a similar view of the switch, the two being shown as combined in one
apparatus.
Fig. 2 is a plan of Figs. 1 and 1ª.
Fig. 3 is a side elevation of the switch.
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Fig. 4 is a side elevation partly in section of the handle and lever or socket
for operating the resistance and switch, the parts being on an enlarged scale.
Fig. 5 is a front view of same.
Fig. 6 is a diagram showing the circuits with two electric motors placed therein,
such motors being in series.
Fig. 7 is a similar diagram but with the motors in parallel.
In the above drawings I have shown my arrangements as adapted for use on a
tramcar or vehicle propelled by electricity, and this is particularly the case with the
diagrams referred to, but it will be evident that my invention is not confined to the
exact arrangement of parts shown.
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The resistance consists of a pot or cell for a liquid preferably surrounded by
outer casing 2, and having a suitable terminal 3 on its base insulated from the cell,
such terminal being adapted to receive at one end a wire which may be secured in
an opening therein while the other end is in electrical contact with a terminal
plate 4 consisting of an annular grooved ring (or it may be a ring of some other
suitable shape or a corrugated plate) such ring being preferably of lead. Upon
this plate a movable ring or terminal plate 5 of a shape approximating thereto is
adapted to rest and make contact. The two plates 4 and 5 I prefer to make of the
shape shown in Figs. 1 and 2, one being a duplicate of the other. With this
construction the plate 5 (which is a movable one) presents two rims or rings 6, 6ª
to the surface of the liquid with which the pot 1 is filled, so that when being with-
drawn the small rim 6 is the last to leave the liquid, and the formation of a large
spark is avoided.
The plate 5 is capable of a rising and falling movement in the cell 1 (which may
be charged with a suitable liquid) and for this purpose is provided with webs 7
which prevent it offering much frictional resistance to the liquid, and afford a
means for attaching to it a metallic or other cord capable of conducting electricity
such cord passing over a pulley 8 of insulating material, and being secured to a

page_text: fixed point as 9 on the side of the pot or cell. The point 9 is in electrical connection
with a suitable terminal 10 carried on the cell. The pulley 8 is carried by an arm 11
which is fixed about centrally on a shaft 12, such shaft carrying at one end a
lever 13. connected by means of a weighted rod 14 with a lever 15 carried by.a
shaft 16 which forms part of the switch and which will be hereafter described.
The shafts 12 and 16 are carried in suitable bearings, one of the bearings for
the shaft 12 having attached to it a fixed segment 17 having teeth or pro-
jections 18, the edges of which are slightly rounded, and a tooth or projection 18"
one edge of which is kept square. On the end of the shaft 12 is secured a lever
or socket the parts composing which consist of a boss 19 secured to and operating
the shaft 12, such boss carrying two lugs 20, 20 (Fig. 5) between which is
pivoted the socket portions 21. This socket carries a tooth 22 which normally
engages between the teeth 18 of the fixed segment 17 being pressed in that direction
by spring 23 secured to the shaft 12 by stud 24. To the segment 17 is bolted or
secured a case or front plate 25 provided with a long slot or opening and a recess 26
(Figs. 2 and 4) such recess being nearly opposite the tooth 18". The socket 21 is
adapted to receive an extension 27 of a handle 28, the extension being provided
with a tongue 29 which will pass through the recess 26, an1 when the handle and
socket are shifted to the left will pass under the flange 30 of the front plate 25, so
that the handle cannot be withdrawn except when the tongue is opposite to the
recess 26 in which case the tooth 22 is abutting against the square face of the
tooth 18. It will be understood that the handle may be moved to and fro by first
drawing it forward against the pressure of the spring until the tooth 22 is clear of
the notch and then moving it to the left, and that it may be held in any position as
the spring 23 will force the tooth 22 between the teeth 18 while it yields sufficiently
to allow the tooth 22 to pass over the teeth 18, and that in this way the plate 5 in
the pot or cell may be held at the desired distance from the fixed plate 4 or be
gradually lowered thereon, thus making and breaking contact with the plates
through the resistance of the fluid. The shaft 16 carries. two pairs of contact
arms 31, 31, insulated from the shaft and from each other, while a base plate 32
carries terminals 33, 34, 35 and 33" 34, 35. Each of these terminals consist of a
pair of spring plates as shown in Fig. 3 between which the contact arms 31 pass,
studs 36 being employed to adjust the nip or pressure between the plates so that
the arms 31 shall always make a good contact. The terminals 33, 33* are
electrically connected together, the other terminals not being connected to each
other except when connected by the contact arms as will be hereafter described.
The contact arms are insulated from the shaft by suitable insulating
material 37, 37b, and are bolted to the shaft 16 by the bolt 37, and the shaft is
supported in bearings 38, 38. It is provided at the opposite end to the lever 15
with collars 39 between which engages the forked end of a lever 40 pivoted at 41,
such lever being rocked from a pedal, such pedal being removable from the part 40
in order that the latter may not be shifted except by an authorized person provided
with the pedal. It will be seen that the lever 40 upon being drawn outwardly
will shift the shaft 16 laterally, and to draw back the lever and move the shaft to
its original position a spring 43 is employed connecting said lever with a fixed part
on the frame as for instance the pin 44. The shaft 16 also carries a stud 45 which
when the shaft is in one position abuts against the bearing 38" and when in another
position is in line with a slot 46 in the bearing and will pass through same, thus
allowing the shaft to be shifted laterally when the parts are in the correct
position.
Before proceeding to a description of the operation of the apparatus I would
point out that I find the construction shown of the terminal plates or rings 4, 5 to
be exceedingly effective as allowing of an easy movement and preventing any
accumulation of dirt on the lower plate 4, as dirt falling thereon will pass through
the opening formed by the rim 6, and fall to the bottom of the cell, thus always
allowing the plates to make a good contact with each other. The arrangement of
the terminal 3 in the bottom of the cell is also a convenient one, but instead of the

page_text: pottery jar or cell 1 shown a metal jar could be used in which case the bottom
plate 4 could be attached to the base of the jar the centre opening of same forming
a drain or plug hole which could be secured by a suitable plug. The metal jar
would of course have to stand on an insulating base and be shielded as in the
present case. The terminal now at the base could be attached to the jar any-
where, but the top terminal would have to be insulated. Such a metal jar would
require insulating guides to prevent the movable plate 5 fron swinging against the
side and so short circuiting. The arrangement of the arm 11, pulley 8, and cord
connected to the movable plate 5 is also of advantage in multiplying the distance
moved by the plate when the handle 28 is moved, while should the cord break and
the plate 5 fall to the bottom no serious accident would occur as the breaking of
the cord breaks the circuit.
In the operation of the apparatus which will be understood by reference to the
figures previously described and to the diagrams Figs. 6 and 7, it is desirable
particularly in the case of tramcars and like vehicles starting with heavy loads
and employing two motors as M, M, that the latter should be in series at the
starting of the car and should be capable of being readily set in parallel when
running to develop a higher speed. According to the arrangement I have described
above, the switch (which I term a setting switch) automatically comes to series
whenever the plate 5 is lifted clear of the liquid in the pot 1, this being effected by
means of the spring 43 which forces the shalt 16 into the position shown most
clearly in Figs. 2 and 3. In this way the motors cannot be started in parallel
without a distinct operation on the part of the attendant, such operation consisting
in keeping down the pedal 42 so that the shaft is prevented from being forced
back.
The path of the circuits when the motors are in series and in parallel is clearly
shown in Figs. 6 and 7, in which, referring to Fig. 6 it will be seen that the
current passing through the resistance enters the motor M, passes through same
to some suitable reversing switch R out to the terminal 34 of the setting switch S,
across the terminal 33 by way of contact arm 31, from 33 to 33, across to 34" by
the other contact arm 31, out to the second motor M through another reversing
switch and to earth, while in Fig. 7 the current passing through the resistance 1
enters the motor M, passes through R to terminal 34, across to 35 by way of arm 31,
and to earth, another part of the current from resistance 1 passing to terminal 35"
across to 34 by way of the other contact arm 31, and out to motor M and through R
to earth.
It will be seen that when the plate 5 is out of the liquid the same movement of
the handle has turned the contact arms 31, 31, so that they are above and
below the terminals 35 and 35ª respectively and are clear of same, and in this
position the stud 45 is facing the slot 46 so that the power of the spring 43 will
pull the shaft laterally and set the parts for series working. This stud must pass
through the bearing 38ª and be clear of same before the shaft 16 can be turned by
the handle, thus ensuring that the contact arms 31 are always opposite the terminals
when the shaft is turned. One of the collars 39 on the shaft regulates the lateral
movement in one direction, and a collar 47 regulates it in the other, both abutting
on either side of the bearing 38ª.
]
The pot though shown in the drawings as having straight sides may if desired
have its edges turned over to prevent splashing, and it may also be provided
with a hole to regulate the level of the liquid provided with a suitable tube to
lead it away.
Having now particularly described and ascertained the nature of my said inven
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a liquid resistance for electric circuits the construction and arrangement
of the plates 4, 5, flexible connecting cord and lifting and operating device,
11

page_text: 2. In a liquid resistance for electric circuits the combination and arrangement of
parts substantially as described and illustrated in Fig. 1.
3. A switch consisting of contact arms carried by a shaft, terminals for the
contact arms to engage with, means for sliding the shaft to and fro in front of the
terminals, and means for enabling the shaft to be returned to a normal position
substantially as and for the purpose described.
4. In a switch the combination and arrangement of parts substantially as
described and illustrated in Figs. 14 to 3.
5. In a switch constructed substantially as described in Claims 3 and 4, the
employment of a removable pedal for the purpose set forth.
6. The arrangement and combination of parts forming the combined resistance
and setting switch substantially as and for the purpose described.
7. In a switch a lever for operating same adapted to receive a removable
handle and constructed and operating substantially as and for the purpose.
described.
Dated the 21st day of August 1895.
PHILIP M. JUSTICE,
Chartered Patent Agent, 55 & 56 Chancery Lane, London,
For the Applicant.