Improvements in and connected with Resistance Switches for Electric Circuits.
Year: 1899

page_text: Date of Application, 4th Mar., 1899
Complete Specification Left, 4th Dec., 1899-Accepted, 3rd Mar., 1900
PROVISIONAL SPECIFICATION,
Improvements in and connected with Resistance Switches for Electric
Circuits.
We, JOHN HENRY HOLMES and FRANK BROADBENT, both of Portland Road
Works, in the City and County of Newcastle-on-Tyne, Electrical Engineers, do
hereby declare the nature of our invention to be as follows:-
It is usual to provide in the circuit of an electric motor a resistance which,
as the speed of the motor increases, can be gradually cut out by the operator
to prevent an abnormal flow of current upon closing the said motor circuit.
In the case also of other electricity-consuming devices requiring a large cur-
rent is undesirable to suddenly switch them into circuit on account of the dis-
turbance in the electrical pressure in the supply conductors, and to prevent this
a resistance may be inserted in series with the device to limit the current to a
small amount when the circuit is first closed, which said resistance can then be
gradually cut out until the current has reached the normal.
The object of our invention is to provide an improved apparatus whereby the
motor, or other circuit, can be closed through a resistance, which said resistance
is then gradually cut out of circuit in an automatic manner quite independently
of the operator.
We employ a moveable member or rheostat contact arm, adapted to be worked
over a series of contacts in the are of a circle or a straight line or otherwise in
a direction to cut resistance out of the circuit by a force such as may be exerted
by a spring, or weight, acting upon it and controlled as to rate of movement
which can be effected by a dash pot or other regulating device, such as an escape-
ment or fly, the said rheostat contact arm being moved by the operator in the
direction to insert resistance in the circuit.
In combination with the rheostat contact arm we provide another moveable
arm or member which may be called the switch contact arm, so constructed that
at one extremity of its range of movement it engages with the rheostat arm in
such a manner that when moved by the operator towards the other extremity of
its range it draws the rheostat arm with it inserting the resistance as it proceeds.
On nearing the end of its travel, the switch contact arm causes the electric
circuit through the resistance and motor, or other current consuming device,
to be closed and then the rheostat contact arm is disengaged and is free to travel
slowly backwards over the contacts so as to gradually cut out the resistance in
an automatic manner, quite independently of the operator.
When the switch contact arm is moved in the reverse direction it opens the
switch and breaks the circuit, and the motion being continued to the end of
the stroke, as it ought to be, it again engages with the rheostat contact arm,
the apparatus being then in position for a repetition of the above described
operations.
Although we have described the backward movement of the switch arm to
break the contact as being directly performed by the operator, we prefer that

page_text: it should take place through the agency of an independent force such as that of
a spring, or weight, with the object of preventing it remaining in any inter-
mediate position between the extremities of its travel or of the switch being
improperly actuated.
To accomplish this we prefer to employ a retaining electro-magnet which
when energized holds the switch contact arm in such a position as will keep
the circuit closed in opposition to the force of the spring, or weight, tending to
impel or move it in the backward direction. This retaining electro-magnet
may be energised in any suitable manner such as by inserting its exciting coil
in series with the shunt winding of the magnets of the motor, or in the main
circuit of the electric consuming device, or it may be wound of such a resist-
ance that it may be connected as a shunt directly across the mains. When
thus arranged we open the circuit by mechanical operation or by de-energising
the magnet. This latter will occur automatically in the event of failure of the
electric supply. A push button or switch may be used for effecting the de-
energising of the electro-magnet by short-circuiting the exciting coil when
it forms part of the shunt circuit of the electric consuming device or diverting
the current from it when the exciting coil is in series with the current con-
suming device, or for opening the branch circuit when the exciting coil is con-
nected directly as a shunt across the supply mains.
We may use a liquid resistance or a resistance of any other suitable kind.
To prevent the attendant opening and closing the switch when all the resist-
ance is cut out, thus permitting the excessive current to pass through the motor
or other consuming device, we provide an automatic device which may be
arranged as follows:-
We enclose the whole of the working parts leaving the handle connected to
the switch contact arm projecting through a slot in the casing. When the
handle is moved to its farthest extremity to close the circuit it enters a hood or
cover or may be otherwise protected in such a way as to prevent the attendant
taking hold of it in order to pull it out of the switch contact jaws. To release
the arm he must press a button or the like which may be a moveable part of
the handle or be separate therefrom. In order to prevent him, on releasing the
arm, catching it on its return stroke the handle may be so constructed as to
slide upon, or in, the contact arm and be geared with the push button in such
a way that when the button is pressed the handle moves down until it disap-
pears within the casing above-mentioned and is held there by a guide on its
return stroke to the "off" position where the guide terminates allowing the
handle to again protrude through the slot.
Or we may provide a stop which holds the rheostat contact arm on the last
contact of the resistance whilst the switch contact arm is in the switch jaws.
On the switch contact arm being released and leaving the jaws it at the same
time lifts a catch releasing the rheostat contact arm and allowing it to fall en-
tirely clear of all contacts. In this position it is absolutely necessary for the
attendant to bring the switch contact arm back to the extreme "off" position in
order to engage with the rheostat contact arm. Or the circuit may be similarly
interrupted in other suitable place.
By suitably duplicating the necessary parts the arrangement can be applied
to reversing switches used for running motors for example in both directions.
Dated this 4th day of March 1899.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents,

page_text: COMPLETE SPECIFICATION.
Improvements in and connected with Resistance Switches for Electrico
Circuits.
We, JOHN HENRY HOLMES and FRANK BROADBENT, both of Portland Road
Works, in the City and County of Newcastle-on-Tyne, Electrical Engineers, do
hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement:
-
It is usual to provide, in the circuit of an electric motor, a resistance which,
as the speed of the motor increases, can be gradually cut out by the operator,
to prevent an abnormal flow of current upon closing the said motor circuit.
In the case also of other electricity-consuming devices requiring a large cur-
rent it is undesirable to suddenly switch them into circuit on account of the dis-
turbance in the electrical pressure in the supply conductors, and to prevent this
a resistance may be inserted in series with the device to limit the current to a
small amount when the circuit is first closed, which said resistance can then be
gradually cut out until the current has reached the normal.
The object of our invention is to provide an improved apparatus whereby the
motor or other circuit, can be closed through a resistance which said resistance
is then gradually cut out of circuit in an automatic manner quite independently
of the operator.
We will describe our invention by reference to the accompanying drawings
in which
Fig. 1 is a front elevation of one form of our improved resistance switch
arranged in an electric motor circuit, which latter is shewn diagrammatically.
Fig. 2 is a view of the said resistance switch shewing the casing in vertical
section and the switch mechanism in side elevation.
Fig. 3 is a vertical section of a detached portion of the switch.
Figs. 4 and 5 are front elevations of the same switch with the parts in different
positions, and
Figs. 6 to 11 inclusive are elevations of portions of other forms of our improved
switch.
Like letters of reference indicate corresponding parts throughout all the
figures of the drawings.
In constructing a resistance switch such as shewn in Figs. 1, 2, 3, 4 and 5,
we provide a moveable member or rheostat contact arm A adapted, by a spring
or springs a (or a weight a as in Fig. 10 or other equivalent means) to be worked
over a series of contacts or contact studs b', 62, 63, 64, 6³, be, b, 63, and 610 in the arc
of a circle in the direction indicated by the arrow in Fig. 4 that is to say the
direction for cutting out resistance from the completed circuit, the rate of this
movement being controlled by a dash-pot C* or other regulating device such as
an escapement or fly, the said contact arm A. being moved by the operator, in
the direction indicated by the arrow Fig. 1 to insert resistance in the uncom-
pleted circuit.
The rheostat contact arm A is pivotted on a stud a¹ which is, as are also the
contact studs to 610, rigidly secured to the support C which is formed prefer-
ably of slate.
The rheostat contact arm A is constructed in two main parts riz.-The con-
ducting part or contact proper 2 which is formed of resilient metal and bears
directly both on the above named contact studs 1 to 610 and on a segmental
contact bar 2, and the non-conducting part a³ which is pivotted on the stud a¹

page_text: and to which is secured the conducting part a, suitable non-conducting material
placed inside the metal strap at being employed for electrically insulating the
part from the part 3. Connected to the arm A is a segment to whose
periphery is attached one end of a flexible band a the other end of which is
attached to the before mentioned springs or weight a and dash pot C* these latter
conveniently being combined as shewn in the drawings to form a single fitting
which may be secured to the support C₁ or to the casing D or other suitable
part of the apparatus.
In combination with the rheostat arm A we provide an arm or member E
which may be called the "switch contact arm," and which, like the arm A is
pivotted on the stud a¹, this arm E being so constructed that at one extremity
of its range of movement it is caused by a hook e and projection to engage
either directly as in the arrangements shewn in Figs. 6, 7, 8 and 9, or indirectly
as in Figs. 1 and 2 with the rheostat arm A in such manner that when the said
switch contact arm is moved by the operator in the direction indicated by the
arrow in Fig. 1 the rheostat arm A is drawn by, or moved with it, more and
more resistance being inserted in the then incomplete circuit the further the arm
proceeds.
On nearing the end of its rightward travel the rheostat contact arm A leaves
the last of the resistance contact studs 60 and the switch contact arm E through
the insulated contacts c c thereon electrically connects the respective pairs of
switch terminals f f'.
At this juncture the rheostat arm A is released from the switch contact arm E,
for which purpose, in the arrangement shewn in Figs. 1 to 5 we provide an arm h
pivotted on the stud a and carrying the spring or equivalently controlled
hook e adapted to engage with the catch or projection a on the rheostat arm A,
the said hook having an arm el projecting therefrom to enable it to be released
from the projection a as shewn in Figs. 4 and 5 by the said arm coming in con-
tact with a fixed stud or projection c². The arm his provided with a projection
adapted to engage a projection e on the switch contact arm I when the circuit
is to be broken mechanically which may be effected by the operator moving,
in the direction of the arrow in Fig. 4, the handle H secured on the boss of
the arm h. When the rheostat arm A is released from the switch contact arm E
as last described the said rheostat arm, under the influence of the springs or
weight a, is caused to move (at a regulated speed as previously mentioned)
towards the left, the circuit through the motor or other current-consuming
device=
being completed at the instant that the rheostat arm A makes contact
with the resistance contact stud 610 the maximum resistance being then included
in the circuit. The resistance thereafter is gradually cut out automatically dur-
ing the travel of the rheostat arm A towards the left until the said arm A
reaches the contact stud 1 when all the resistance is removed,the rheostat
arm A being arrested by a stop e when it reaches this position.
When the switch contact arm E is moved in the direction indicated by the
arrow in Fig. 4 it opens the switch and breaks the circuit and the motion being
continued to the end of the stroke as it ought to be the hook e being carried to
its normal position under the influence of the weight on the arm again
engages with the projection of the rheostat contact arm A, the apparatus
being then as shewn in Fig. 1, in position for a repetition of the above described
operations.
Although we have described the backward movement of the switch contact
arm E, to break the circuit, as being directly performed by the operator, we
prefer that it should take place through the agency of an independent force such
as that of a spring e, Figs. 2 and 3 or a weight, with the object of preventing
it remaining in any intermediate position between the extremities of its travel
or of the switch being improperly actuated.
To accomplish this we prefer to employ a retaining electro-magnet which
when energized, holds the switch contact arm E conveniently by an armature e

page_text: carried on the said arm, in such a position as will keep the circuit closed in oppo-
sition to the force of the spring or weight e, which, as aforesaid, tends to move
the arm in the backward direction to its normal position. This retaining electro
magnet may be energized in any suitable manner such as, as shewn in Fig. 1,
by inserting its exciting coil in series with the shunt winding of the magnets
of the motor, or in the main circuit of the electricity-consuming device, or
it may be wound of such a resistance that it may be connected as a shunt directly
across the mains ff. When thus arranged the circuit may be opened either
by mechanical operation through the hand lever H as previously described or by
the de-energisation of the electro-magnet F.
This latter will occur automatically in the event of failure of the electric
supply or it may be effected at any time by means of a push button or switch i
so arranged as when operated either to short-circuit the exciting coil of the
electro magnet F when the said coil, as shewn in Fig. 1, is included in the shunt
circuit of the electricity-consuming device, or to divert the current from the
said electro-magnet when the exciting coil thereof is in series with the electricity-
consuming device, or to open the branch circuit when the exciting coil of the
magnet is connected directly as a shunt across the supply mains.
is an insulated stud or projection on which the end of the part of the
rheostat arm rests when it has been moved past the resistance stud to and before
the circuit through the electricity consuming device is completed, and is a
spring device for imparting the initial impulse to the switch contact arm E
when the circuit is broken through the electro-magnet F.
The apparatus shewn in Figures 1 to 5 is arranged as a double pole switch and
those shewn in Figures 6 to 11 are arranged as single pole switches but it will
be obvious that if desired the apparatus shewn in Figures 1 to 5 may be arranged
as a single pole switch and those shewn in Figures 6 to 11 may be arranged as
double pole switches.
To prevent the attendant from opening and closing the switch when all re-
sistance is cut out and thus prevent an excessive current being passed through
the motor or other electricity consuming device we provide automatic mech-
anism which may be arranged as next described with reference to Fig. 6.
In this arrangement we enclose the whole of the working parts in a casing 1)
(only the upper portion of which is represented in the drawing) leaving only
the handle H, which in this example is formed as an extension of the switch
contact arm E, projecting through a slot in the top of the casing 1). When
the handle H is moved to its farthest extremity to close the circuit it enters a
hood or cover d, or may be otherwise protected in such a way as to prevent the
attendant taking hold of it in order to withdraw the contact plate from the
switch contact jaws f. To release the arm E the attendant must press a button
or the like
which may be arranged either as shewn in Fig. 6 or as a moveable
part of the handle H₁ so as to effect the de-energisation of the electro-magnet F
as previously described with reference to the push button in Figs. 1, 2, 3 & 4.
In order to prevent the attendant, after releasing the arm E, from arresting it
on its return stroke, the handle H is constructed so as to slide upon or in the
switch contact arm E and is arranged to be actuated by the button when the
latter is operated as above mentioned for de-energising the electro-magnet F,
the stem of the said button being for this purpose provided with an arm
adapted to bear on a roller carried on the stem of the sliding handle H¹ so
as to press the handle inwards until it disappears within the casing 1) the said
handle being retained in its depressed position by a guide during its return
stroke to the off position at a part corresponding to which the said guide
terminates, allowing the handle H¹, under the influence of a spring h*, to again
protrude through the slot so as to be ready for a repetition of the switching
operation.
In another arrangement for preventing the switch from being improperly
actuated as shewn in Figs. 7 and 8 we provide a spring or equivalently-controlled

page_text: stop k, which, by engaging with a projection as on the rheostat contact arm A,
retains the latter on the resistance contact stud during the time that the con-
tact plate of the switch contact arm E is in the switch contacts f as shewn in
Fig. 7.
On the switch contact arm E being released either by the de-energisa-
tion of the electro-magnet F or by the attendant pulling over the handle H
in opposition to the influence of the said electro-magnet, and the contact plate c³
thereby withdrawn from the switch contacts f the said switch contact arm E,
by means of a cam et, presses the stop k out of engagement with the projection a³
and thereby allows the rheostat contact arm A, under the influence of the actu-
ating weight or springs (a) to move clear of all the resistance studs as shewn
in Fig. 8 in which position it is arrested by the stop and the end of the part
of the said theostat arm is supported on an insulated or non-conducting stud b.
In this position it is absolutely necessary for the attendant to move the switch
contact arm E back to the extreme off" position in order to admit of the hook e
engaging with the rheostat contact-arm. Instead of effecting the release of the
theostat contact-arm A by mechanical means as last described we may obtain
the same result electrically, as for example by the apparatus shewn in Fig. 9
wherein an electro-magnet L is arranged at the left hand side and connected in
series with the electro-magnet F so that these two electro-magnets are energised
simultaneously. In Fig. 9 the switch is represented in its "
on position
wherein the switch contact arm E is retained in position by the electro-magnet F
and the rheostat contact arm A is retained in contact with the resistance stud t
by the pivotted armature 7 of the electro-magnet L, which armature at that
juncture, is held in the position in which it is shewn in full lines by the energi-
sation of the said electro-magnet L. When the attendant breaks the circuit
by moving the handle H¹ towards the left, both of the electro-magnets F and L
are de-magnetised and the pivotted armature 7 moves into the position in which
it is shewn in dotted lines and thereby allows the rheostat contact arm A to
move clear of all the resistance studs on to the insulated or non-conducting
stud b.
"
In Fig. 10 we show a modification of the switch which admits of it being used
In this arrangement
for regulating the current in a motor-or other circuit.
the starting handle H¹ is adapted to operate at the back of the rheostat contact
arm A and, when this handle is moved towards the "on" position it pushes both
the rheostat contact arm A and the switch contact arm E forward until the
circuit is closed and the switch contact arm E is retained by the electro-magnet F
as explained in reference to the previously described examples. When the
attendant releases the handle H the rheostat contact arm A, under the influ-
ence of its controlling weight or springs and dash-pot is moved slowly back and
pushes the handle before it. A stop not shewn in the drawing may be provided
for arresting the starting handle H and therefore the rheostat contact arm A
at any desired position and consequently control the amount of resistance in-
serted in the circuit and the speed of the motor or the working of the other
electricity consuming apparatus, as the case may be.
Instead of using wire resistances as diagrammatically represented in Figs. 1,
7, 8 and 9 we may use any other suitable resistances for example as shewn in
Fig. 11, a liquid resistance may be used in which arrangement the rheostat
lever is formed in one with or as a dipper m adapted to enter a trough n contain-
ing liquid the resistance being varied according to the extent to which the
dipper is immersed in the liquid. When the operator lifts the starting handle H¹
the hook e engages with the projection on the dipper m so that the latter is
also raised and subsequently withdrawn from the liquid and at the same time the
switch contact lever E is moved over to electrically connect the pair of switch con-
tacts f. The dipper m is then released from the landle H¹ by the arm hook c
striking against the stud or projection and the dipper then enters and descends
deeper and deeper into the liquid n¹ so as to first complete. the circuit with the
maximum amount of resistance inserted therein and afterwards gradually reduce

page_text: the resistance until it is removed entirely from the circuit. To break the circuit
the handle H is moved to the left as in the before described examples when the
projection pushes the switch contact arm E along with it so as to withdraw
the contact plate e from the switch contacts f after which the hook e again
engages with the projection on the dipper m so as to make the switch ready
for a repetition of the switching operation. If desired the liquid resistance
apparatus may be provided with a "holding-on" electro-magnet F in the same
manner as has been previously described in connection with the other examples.
It will be obvious that instead of arranging the resistance contact devices
of our improved switches to operate in curved paths we may if desired arrange
them so as to operate in a straight line or otherwise.
By suitably duplicating the necessary parts the before described arrangements
can be applied to reversing switches used for running motors in both directions.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is:-
-
1. In resistance switches for electric circuits, a moveable member adapted to
work over a series of resistance contacts or the equivalent and means for return-
ing the said member in a direction to cut out resistance, in combination with
another moveable member these two moveable members at one extremity of
their movement being caused to engage so that they shall operate together when
moved in a direction to insert resistance, and a contact through which the second
moveable member at the other end of its movement electrically connects the
switch terminals and means for then releasing the first named member and
means for controlling the backward movement of the said first named member
so that it slowly cuts out resistance: substantially as hereinbefore described.
2. In combination with the subject matter of the preceding claiming-clause
the combination with the second moveable member of a device tending to move
the said member from the position in which it closes the circuit and an electro-
magnetic device to keep the circuit closed against the action of the said device
substantially as herein before described.
3. In resistance switches as claimed by the preceding claiming-clauses the
combination with the handle by which the switch is operated, of means whereby
the handle is protected, or brought into such a position that it cannot be grasped
to improperly actuate it: substantially as herein before described.
4. In combination with resistance switches as claimed by the preceding first
two claiming clauses, of means, substantially as described, whereby the operator
cannot operate the first-named moveable member which puts in, and cuts out,
the resistance until he brings the second named member far enough back to
engage with the first named member substantially as herein before described.
5. The various combinations and arrangements of parts constituting the resist-
ance switches substantially as herein before described and illustrated in the accom-
panying drawings.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.