Improvements in Rheostats or Electric Resistance Switches.
Year: 1899

page_text: Date of Application, 15th Apr., 189
Complete Specification Left. 19th Feb., 1990-Accepted, 19th June, 1900
PROVISIONAL SPECIFICATION.
Improvements in Rheostats or Electric Resistance Switches.
We, JAMES MARR, Managing Director, WILLIAM CRANSWICK LAIDLER,
Electrician, and THE SUNDERLAND FORGE AND ENGINEERING CO. LIMITED, all of
Pallion, Sunderland, in the County of Durham, do hereby declare the nature of
this invention to be as follows:-
This invention relates to rheostats or adjustable resistances or'
switches, such as are used in starting boxes for electric motors.
resistance
In the ordinary construction of these devices the rotatory contact-arm or lever
for closing the circuit through all the resistance and for cutting out the resistance
is actuated manually; but this plan sometimes leads to injury to the motor owing
to the arm or lever not being in the proper position for starting when the current.
is switched-in by the main switch. The object of this invention is to obviate
such liability by adapting the contact-arm or lever to be automatically returned
from the point of the decreased or no resistance to the maximum point of resist-
ance on the current being switched-out or the circuit broken by a defect.
To this end, we fix the contact-arm or lever upon a spindle operatable in one
direction by suitable mechanism in opposition to appropriately applied force, to
remove or cut out the resistance, and in the other direction, to replace the
resistance, by the re-action of the opposing force permitted by the displacement
of all or a part of the said mechanism, which displacement is effected by the
inertness of a magnetic attracting contrivance energized, and holding the mech-
anism or part thereof in the operative position, when the circuit is closed.
According to one way of carrying our invention into practice, we form
the contact-arm or lever integral with, or we fix it upon, a revoluble spindle
suitably supported and encircled at a convenient place--for example, contiguous
to the contact-arm-by a spiral spring arranged and attached at its opposite
ends say one end to the spindle and the other to the frame or slab supporting
the contacts as usual-in such manner that when the spindle is turned in the
direction necessary to cause the contact-arm to cut out the resistance, the spring
is compressed but on the removal of the restraint upon the spindle, the spring
re-ants and thereby returns the spindle and arm or lever to reinsert the resist-
arce. For accomplishing the former operation, we mount on the spindle a
worm-wheel which is driven by a worm on an adjacently disposed spindle rotat-
able by a hand-wheel. This spindle is made in two or more sections united by
an universal joint so as to enable the worm being swung or thrown out of, and
into, gear with the worm-wheel; the bearings being arranged to meet these
motions. The displacement and replacement of the worm from and to its work-
ing position is performed by a shunt electro-magnet or magnets whose armature
is connected by a link or lug to the portion of the shaft carrying the worm,
and also to a spiral spring normally opposing the attraction of the magnet or
magnets, which. when energized, attracts or attract the armature and so puts
and maintains the worm in gear but when inert, the armature is withdrawn by
the connecting spring and the worm is disengaged from the worm-wheel.
The customary connections and conjunctive contrivances are, of course, made.
and fitted to procure the proper working of the arrangement and construction
just described, whose operation is briefly as follows:

page_text: Assuming the motor has to start from rest, and the contact-arm or lever is at
the end of its path giving the greatest resistance to the current, then when the
main switch is operated to close the circuit, the shunt magnet or magnets is or
are energized, thereby attracting the armature, and consequently putting the
worm in gear with the worm-wheel on the contact-arm spindle, so that the
worm-wheel can be revolved by the worm and hand-wheel to actuate the contact-
arm or lever to cut out the resistance, and so permit the motor to attain its
speed. Now, supposing the circuit is opened or broken by the main switch or
by a constructive defect, then the shunt magnet or magnets becomes or become
inert, whereupon the armature is displaced therefrom by its spring and the worm
is simultaneously removed from its operative position, and immediately this
occurs, the spindle of the contact-arm is free to be, and is revolved by its return-
ing spring, thereby placing the contact-arm or lever at the point of greatest
resistance; thus the motor stops and the contact-arm or lever is in the required
position for a re-start.
As will be obvious, the details for carrying our invention into practice may be
variously modified to meet particular applications; for example, the worm and
worm-wheel may be replaced by equivalent means and the motion opposed by a
weight or weights instead of a spring. Also the magnet armature may be
weighted instead of being withdrawn by a spring, while the magnet or magnets
may be separately excited or replaced by a like device or devices.
Improvements in Rheostats or Electric Resistance Switches.
We, JAMES MARR, Managing Director, (WILLIAM CRANSWICK LAIDLER,
Electrician, and THE SUNDERLAND FORGE AND ENGINEERING CO. LIMITED, all of
Pallion, Sunderland, in the County of Durham, 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:—
This invention relates to rheostats or adjustable resistances
switches, such as are used in starting boxes for electric motors.
or resistance
In the ordinary construction of these devices the rotatory contact-arm or lever
for closing the circuit through all the resistance and for cutting out the resistance
is actuated manually; but this plan sometimes leads to injury to the motor owing
to the arm or lever not being in the proper position for starting when the current
is switched-in by the main switch. The object of this invention is to obviate
such liability by adapting the contact-arm or lever to be automatically returned
from the point of the decreased or no resistance to the maximum point of resist-
ance on the current being switched-out or the circuit broken by a defect.
To this end, we fix the contact-arm or lever upon a spindle operatable in one
direction by suitable mechanism in opposition to appropriately applied force, to
remove or cut out the resistance, and in the other direction, to replace the
resistance, by the re-action of the opposing force permitted by the displacement
of all or a part of the said mechanism, which displacement is effected by the
inertness of a magnetic attracting contrivance energized, and holding the mech-
anism or part thereof in the operative position, when the circuit is closed.
In carrying our invention into practice, we form the contact-arm

page_text: or lever integral with, or we fix it upon, a revoluble spindle suit-
ably supported and encircled at a convenient place-for example, contiguous
to the contact-arm-by a spiral spring arranged and attached at its opposite
ends--say one end to the spindle and the other to the frame or slab supporting
the contacts as usual-in such manner that when the spindle is turned in the
direction necessary to cause the contact-arm to cut out the resistance, the spring
is compressed but on the removal of the restraint upon the spindle, the spring
re-acts and thereby returns the spindle and arm or lever to. reinsert the resist-
ance. For accomplishing ne former operation, we mount on the spindle a
worm-wheel which is driven by a worm on an adjacently disposed spindle rotat-
able by a hand-wheel. This spindle is made in two or more sections united by
an universal joint so as to enable the worm being swung or thrown out of, and into,
gear with the worm-wheel; the bearings being arranged to meet these motions if re-
quired. The displacement and replacement of the worm from and to its work-
ing position is performed by a shunt electro-magnet or magnets whose armature
is connected by a link or lug to the portion of the shaft carrying the worm,
and also to a spiral spring normally opposing the attraction of the magnet or
magnets, which, when energized, attracts or attract the armature and so puts
and maintains the worm in gear but when inert, the armature is withdrawn by
the connecting spring and the worm is disengaged from the worm-wheel.
A switch embodying our invention is represented in the accompanying draw-
ings, to which we will now refer, and in which Fig. 1 is a plan, partly in section,
showing the switch, the box, and the main switch; Fig. 2 is a central vertical
section thereof, looking to the left; and Fig. 3 is a side elevation of the worm
shaft and its adjuncts.
A is the contact-arm or lever, and B is the revoluble spindle, these two parts
being made in one piece.
The spindle B is supported at one end in a boss on the cover of the starting
box C, and at its other by the slab or frame D that carries the contacts E, E.
which are arranged in the ordinary way.
Fis the spring encircling the spindle B; as shown in Fig. 2, for the sake of
compactness it is enclosed in a recess or cavity at the underside of the lever A,
and its ends are secured as and for the purpose aforesaid.
G is the worm-wheel fixed on the spindle B. As illustrated, the spindle Bis
made in two pieces, and the wheel G is formed integral with the upper portion
to which the other is united by bolts b, b.
H is the worm gearing with the wheel G, and it is arranged on the spindle I
revoluble by the hand-wheel i. The arrangement of this spindle I will be clearly
understood from Figs. 1 and 3, which show it as composed of three sections ¹, 12,
the section being connected to the sections,, by universal joints, it of any
appropriate type, such as that exemplified. The section carries the hand-
wheel, and it is supported in a boss on the box C, while the section ', whereon
the worm H is disposed, is carried by links 6,6 keyed on a revoluble shaft J
journalled in bearings at the opposite sides of the box C.
K, K are the electro-magnets, and is the armature thereof, the core ends,
with the object of obtaining great attractive force, adjoining the armature being
made of a cuniform shape and the armature correspondingly fashioned. The
armature k is keyed on the shaft J, and hence its connection with the section
of the spindle I carrying the worm H is established by the links, .
L is the spring uniting with the armature k for opposing its attraction, and
it may be fastened to a projection on the armature and the cover of the box C.
or to the back of the armature and the side of the box, as represented respectively
by the full and dotted lines in Fig. 2, a suitably disposed stop being provided if
necessary to determine the pull of the spring.
M denotes the main switch which is connected to the improved switch in the
usual way and as indicated by the dot-and-dash lines in Figs. 1 and 2: and
the customary connections and conjunctive contrivances are, of course, made and

page_text: fitted to procure the proper working of the arrangement and construction just
described, whose operation is briefly as follows:
Assuming the motor has to start from rest, and the contact-arm or lever A is
at the end of its path giving the greatest resistance to the current, then when
the main switch M is operated to close the circuit, the shunt magnet or mag-
nets K, K is or are energized, thereby attracting the armature k, and consequently
putting the worm H in gear with the worm-wheel G on the contact-arm spindle B
SO that the worm-wheel G can be revolved by the worm H and
hand-wheel i to actuate the contact-arm or lever A to cut out the
resistance, and so permit the motor to attain its speed. Now, supposing the
circuit is opened or broken by the main switch M or by a constructive defect,
then the shunt magnet or magnets K, K becomes or become inert, whereupon the
armature is displaced therefrom by its spring L and the worm H is simul-
taneously removed from its operative position, and immediately this occurs, the
spindle B of the contact-arm A is free to be, and is revolved by its returning
spring F, thereby placing the confact-arm or lever A at the point of greatest
resistance; thus the motor stops and the contact-arm or lever is in the required
position for a re-start.
As will be obvious, the details for carrying our invention into practice may be
variously modified to meet particular applications; for example, the worm and
worm-wheel may be replaced by equivalent means and the motion opposed by
ȧ weight or weights instead of a spring. Also the magnet armature may be
weighted instead of being withdrawn by a spring.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is.
1. A rheostat or electric resistance switch, having the contact-arm or lever
fixed upon a spindle operatable in one direction, by suitable mechanism in
opposition to appropriately applied force, to remove or cut out the resistance,
and in the other direction, to replace the resistance by the re-action of the
opposing force permitted by the displacement of all or a part of the said mechanism
which displacement is effected by the inertness of a magnetic attracting con-
trivance energized, and holding the mechanism or part thereof in the operative
position, when the circuit is closed, substantially as set forth.
2. In a rheostat or electric resistance switch, the combination with the contact-
arm or lever, of a revoluble spindle where to the arm or lever is fixed, a spring
encircling the spindle, a worm-wheel on the spindle, a worm on an adjacently
disposed revoluble flexible spindle, a magnet or magnets whose armature is con-
nected to the spindle carrying the worm, and a spring uniting with the armature
for opposing the attraction of the magnet or magnets, all adapted for use sub-
stantially as herein before described in reference to the accompanying drawings.
3. In a rheostat or electric resistance switch, the combination with the con-
tact-arm or lever, of mechanism, substantially of the kind set forth, for cutting
out the resistance by hand, and re-inserting it automatically on the current being
switched-out or the circuit broken.
4. A rheostat or electric resistance switch constructed, arranged and operating
substantially as herein before described, and shown in the accompanying drawings.
Dated this 17th day of February 1900.