Improvements in Resistance Switches and Automatic Cut-outs for Starting, Regulating, and Protecting Electric Motors and their Circuits.
Year: 1899

page_text: Date of Application, 27th Dec., 1899
Complete Specification Left, 27th Sept., 1909-Accepted, 17th Nov., 1900
Improvements in Resistance Switches and Automatic Cut-outs for
Starting, Regulating, and Protecting Electric Motors and their
Circuits.
We, VERITYS LIMITED and LOUIS JOHN STEELE, both of Plume Works, Aston.
juxta Birmingham, in the County of Warwick, all Electrical Engineers, do
hereby declare the nature of this invention to be as follows:-
This invention relates to resistance switches and automatic cut-outs for starting,
regulating and protecting electric motors and their circuits, and consists in
the improvements hereinafter described.
66
According to this invention two arms, having different functions, are provided
upon the resistance switch, the one the switch arm proper working over the
contacts of the resistance, and the other a secondary and independent arm for
bringing into operation and controlling the motor's field circuit and an automatic
magnet release and connecting the armature of the motor through the controll-
ing resistance to one of the supply. The arrangement of these two arms is
important; they are mounted preferably on a common joint and the secondary
arm in its "off" position is always enclosed covered or protected by the switch
arm proper, so that only when the switch arm proper is in its off" position
in respect of the resistance contacts can the said secondary arm be conveniently
got at for operation to complete the motor's field circuit and operate the release.
A simple and effective way of covering and protecting the secondary arm is to
construct the switch arm proper hollow and opensided, so that the secondary
arm and the handle for operating it fits nicely within its interior. A stop
however is arranged to separate the two arms when the switch arm proper is in
on
off" position. Both arms are hand operated to the " positions.
The secondary arm is fitted with a strong spring, and has a hammer action
thereby upon the switch arm proper when flying off.
an
ود
An electro magnet, differentially wound with fine and thick wire coils the
latter respectively coupled to the shunt and armature circuits of the motor is
so disposed as to hold the secondary arm to it in order to magnetise the field
circuit of the motor and make connection to the source of supply. The fine
wire coil of the magnet being preferably connected in series with the shunt coil
of the motor. The electro magnet as aforesaid would only hold the secondary
arm when the field of the motor is sufficiently magnetised for a satisfactory
starting of the motor by the operation of the switch arm proper. The electro
magnet as aforesaid will hold the secondary arm until such time as the current
in the thick windings or coils is sufficient to oppose and balance the effect of
the current in the shunt windings or in the event of the shunt current falling
to too low a limit when the said secondary arm will fly off to operate the switch
arm proper.
In order to effect this the thick wire coils are so formed in relation
to the shunt as to only completely balance the strength of the current in the
shunt windings of the current therein exceeds its normal value by about 50%

page_text: or any other amount which may be predetermined. This electro magnet in
combination with the secondary arm forms an overload release and automatic
cut-out.
These
Special adjusting devices to the over-load release are fitted to the electro
magnet in order to determine the amount of air gap between the poles of the said
electro magnet and the contact piece or armature on the secondary arm.
comprise in one form an eccentrically mounted disc and in another form a
quadrant piece, connected to the said electro magnet so that they can be moved
to form a stop against which the secondary arm moves when advancing to the
electro magnet the said devices admitting the armature or contact piece on the
secondary arm to come either hard up to the poles of the magnet or in a position
with predetermined air gaps, in which latter case the necessary over-load to
release the secondary arm will be less. The disc or the quadrant as the case may
be is graduated to set the release of the secondary arm at a predetermined over-
load. This disc or quadrant is preferably of iron or steel.
The electro magnet of the automatic release may be of a horse-shoe construc-
tion fitted with two coils or solenoids the one a shunt or fine wire coil and the
other a series or thick wire coil.
With this horse shoe magnet a moving magnetic piece is used preferably a bar
of iron or steel hinged from an extention of the yoke at the back of the series
coil. This bar extends to the pole piece at the fore part of the said coil and is
fitted at its free end with an adjustable set pin whose end abuts with the said
pole piece the said set pin defining the distance or air gap at the free end of
he hinge piece shall stand clear of the pole piece. By means of this moving
piece which acts as a magnetic shunt the amount of current necessary in the
series coil to neutralize the effect of the current in the shunt is regulated. It is
to be understood that in such a magnet both coils are wound on one magnetic
circuit instead of being separated into two distinct magnets. This design is
compact, and takes very little space on the resistance switch-board.
.
Instead of winding both shunt and main coils on the same magnet as defined,
the shunt can be arranged on the fixed magnet and the series winding on another
magnet attached to the secondary arm.
A device consisting of a pusher rod with a conducting piece at its end, and
spring operated in one direction, is fitted to the electro magnet, before described,
to make contact with two studs which are so coupled with the shunt coil of the
electro magnet as to short circuit the said coil for the purpose of operating the
magnetic release by hand to stop the motor. A spring contact, fixed at the off
stop in the resistance or rheostat and connected with the shunt coil of the electro
magnet, may be provided instead of the pusher device.
*
"
The resistance or rheostat contacts are so arranged that the switch arm proper
when in an
on position is well out of range of the electro-magnet, and a stop
is also provided so that the operation of the said switch arm proper can have no
effect in making a connection between the secondary arm and the magnetic
release. This ensures the secondary arm being first operated to sufficiently
magnetise the shunt of the motor to guarantee a proper condition to complete
the motor's armature circuit.
The shunt circuit of the motor is so coupled to the armature and to the
resistance or rheostat that, when the secondary arm breaks the circuit, it remains
in parelled with the said armature and rheostat and is therefore not endangered.
The switch arm proper may have fitted to it a fly off spring, in which case a
catch or similar device is provided upon the resistance switch to hold the said arm
in its " on position in respect of the resistance contacts, the said catch or device
being operated, to release the switch arm proper, by the secondary arm as it
flies off from the magnetic release.
"
Instead of the switch arm proper covering the secondary arm in the manner
and for the purpose defined, the two arms may have upon them projections
which are adapted to co-operate with a pawl-like arm in such a manner that the

page_text: switch arm proper must be taken back to its dead contact on the rheostat, and its
projection be caused to operate upon the pawl-like arm to lift it, before the
projection on the secondary arm can pass and admit of the secondary arm's
movement. Another method is a pawl and ratchet arrangement so fitted that
the switch arm cannot be moved to cut out the resistance switch until the
secondary arm is put on which latter operation will cause a pawl fixed to
the board to be released from the ratchet by means of a piece fixed to the
secondary arm.
The resistance or rheostat proper is built up of a number of cast iron grids
suitably insulated and wound and arranged between the top and bottom plates
of the resistance switch in piles or tiers the said grids being threaded upon corner
rods or upright connecting bolts between the said plates. The windings on the
grids may be in multiple and the open sides of the resistance or rheostat
between the top and bottom plates can be boxed in or enclosed by perforated
zine coverings.
The grids as before defined may be protected by open work frames which drop
over the said grids and thread on the bolts as aforesaid in which the boxing
would not be needed a frame being applied between each grid.
The protecting frames described in the previous paragraph can be used in the
building up of a resistance other than the one described where grids are used
for the windings as by the use of such frames with the corner bolts a box of an
open or skeleton construction which will give good ventilation can be formed of
any depth by a number of frames used in the pile or tier.
D
02 1 1
с
1000
W. P. THOMPSON & Co.,
11, Burlington -Chambers, New Street, Birmingham,
Patent Agents for the Applicants.
Improvements in Resistance Switches and Automatic Cut-outs for
Starting, Regulating, and Protecting Electric Motors and their
Circuits.
We, VERITYS LIMITED and LOUIS JOHN STEELE, both of Plume Works, Aston,
juxta Birmingham, in the County of Warwick, all 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:
This invention consists of the hereinafter described improvements in resistance
switches and automatic cut-outs for starting, regulating, and protecting electric
motors and their circuits. The said improvements have for their object the
effective accomplishment of the following, viz:-firstly; to ensure the speed of
an electric motor in the starting being gradual to full, secondly; to prevent
the armature taking an excessive and injurious current when starting up the
motor, thirdly; to cause the motor's circuit to be automatically broken or cut-out
from the supply should any accident occur to the motor such as a broken connec-
tion in the shunt circuit, a short circuit in the armature, or a sudden overload,
fourthly; to ensure the resistances of the switch and cut-out being automatically
inserted in the armature circuit should at any time the motor be switched off
or stopped by the operation of an independent switch such as a main switch
(in which case the resistances would always be in the armature circuit at start-

page_text: ing), and fifthly; to admit of a portion of the resistances of the switch board
being left in the armature circuit to effect a regulation of the speed of the
motor.
A regulating resistance switch and cut-out constructed in accordance with
this invention and comprising the improvements herein before referred to is
illustrated in the accompanying sheet of drawings by a plan, Fig. 1, a section,
Fig. 2, detail sectional elevations Figs. 3 and 4 a detail plan Fig. 4, and a
diagram Fig. 5. In Figs. 1 and 2 two arms c and d having different functions
are provided upon the base or slab a of the switch and cut-out, the one c, the
switch arm-proper, working with one of its ends c² over the resistance contacts e
as ordinarily, and the other, a secondary and independent arm for bringing
into operation the motor's field circuit and an automatic magnetic release 9,
and for connecting the armature of the motor through the controlling resistance
to one of the mains. The arrangement of the arms c and d with respect to each
other upon the base a is important; they are mounted, preferably, at on a
common joint pin, d, to move radially across the switch board, and when the
secondary arm d is in its "inactive" position it is so disposed that it becomes
covered, enclosed, or protected by the switch arm-proper immediately any
movement of the said switch arm-proper from its "off" position takes place to
cut out any of the resistance contacts e, see Fig. 5. For example, the switch arm
proper c in its "off" position rests upon the resistance contact e² (Fig. 1) and
the secondary arm d in its "inactive position is away from the magnetic
release against a stop upon the switch board a, in which position the arm d
can be laid hold of by hand for operation to advance it, independently of the
arm, to make contact with the automatic release; it being one of the objects of
the improvements that the shunt circuit of the motor shall be made through the
automatic release g before the motor's armature receives any effective current
and before the arm c is operated to cut out any of the resistances e from the arma-
ture's circuit; it being understood from the drawing, Fig. 1, and from Fig. 5
that if the arm c is moved from its "off" position to cut out any of the re-
sistances e before the shunt circuit is made, as aforesaid, the arm d would be
covered, enclosed, or protected by the arm c moving over it; in this way ensuring
no accidental imperfect starting of the motor. The method shown in the
drawings of covering or enclosing the secondary arm d is to construct the switch
arm-proper hollow and open sided at 3 to form a box into which the handle do,
for operating the said secondary arm, fits, and is concealed by the hand grip 4 of
the switch arm-proper c when the parts are in the positions shown in the diagram
Fig. 5 and in the exaggerated section Fig. 2, the arm d itself lying at the time
coincident underneath the arm c.
"
"
The secondary arm d is spring-controlled to fly off from the magnetic release a,
a spring (shown in Fig. 2) being fitted to it for the purpose, but the switch
arm proper is loosely but stiffly jointed and has no spring, but is actuated from
its " on position to its "off" position by the energy of the spring when
the arm flys from the magnetic release to its "inactive" position. Upon
the arm is provided an armature or contact piece i for making contact with
the magnetic release g to hold the said arm upon a stud h, Fig. 1, coupled with
one of the mains or source of supply.
The resistance contact e³, which is a stop contact cutting out all the resistance
on the switch, is so arranged in respect of the magnetic release g that, assuming
the arms to be coincident as shown by Fig. 5, and that the arm c is operated by
hand in a direction for starting up the motor (the said arm c carrying with it
the arm the arm c will come to a stop against the said resistance contact e³
and prevent the arm & moving up to the magnetic release g without an inde-
pendent movement, it being evident that if the arm c is now released the
spring will cause the said arms to fly back to their positions on and "inactive"
against the contact e and stop d'
It will be understood that both arms c and d are for hand operation to "active"

page_text: "
and " on and that the arm has a hammer action upon the arm c when
flying off:
The magnetic release g, shown particularly by the detail views Figs. 3, 4,
and 4, but also in Fig. 1, is comprehended by an electro-magnet differentially
wound with fine and thick wire coils m, m2, the latter respectively coupled to the.
shunt and armature circuits of the motor. The said magnet, whose fine wire
coil m is preferably connected in series with the said shunt, is so disposed on
the base of the switch and cut-out that the arm d can be held by its poles at
certain times, viz., when the field circuit of the motor is sufficiently magnetized,
to make connection to the source of supply through the stud h; the said magnet
however only holding the arm d upon the said stud at such time as the field of
the motor is sufficiently magnetized for a satisfactory starting up of the motor
by the operation of the switch arm-proper c. A special adjusting device o, here-
inafter more particularly described, is fitted to the electro-magnet in order to
determine the amount of air gap between the poles of the electro magnet (one of
which is marked m³ in Fig. 1) and the contact piece or armature on the
secondary arm, it being understood however that the said adjusting device will
admit of the said contact piece coming dead up to the said poles as shown in
Fig. 1. The release of the arm d from the electro-magnet is effected auto-
matically by a rise of the current in the thick wire coil m² sufficient to oppose
and balance the effect of the current in the shunt coil m, or by the shunt current
falling to too low a limit, and by hand through a short circuiting device s herein-
after described, in either of which cases the said secondary arm will fly off to
its inactive position. To effect the automatic release as aforesaid the thick
wire coil m² is of such a character in relation to the shunt coil m as to only
completely balance the strength of the current in the said shunt when the current
therein exceeds its normal value by about 50% or other predetermined amount.
The electro magnet thus forms an overload release and automatic cut-out.
"
2
The adjusting device o consists of a rotatable disc o connected to the top of
the electro magnet so that a portion of the contact piece i on the arm comes
against it as a stop, the said disc having upon it facets or flats 03
which can be presented to the contact piece i to give varying air gaps. The said
contact piece is however stopped a distance from the poles of the electro magnet
by a circular part of the disc in Fig. 4ª, but the said facets or flaps are clearly
shown in this fig. The disc is a stiffly working one, preferably iron or steel,
and may be graduated, or carry a scale, if desired. The setting of the disc
effects the release of the secondary arm at a predetermined overload.
The short circuiting device s consists of a pusher sa fitted to the electro magnet
to make contact, by means of a spring strips, between two studs 4, 5, which are
coupled with the shunt coii m of the electro magnet, the effect of the contact so
made being to short-circuit the said coil and so release the arm d. The pusher
rod is for hand operation for stopping the motor under ordinary conditions.
The position of jointing of the arms c and d may be varied so long as the one
arm can cover in or enclose the other at times for the purpose defined, and also
so that the said arms have the effect of putting the resistance in the armature's
circuit when the automatic and hand release come into action.
The disc o of the adjusting device o may be a plain circular one eccentrically
mounted, or a quadrant.
The short circuiting devices need not be carried or supported in part on the
electro magnet so long as the studs of it are connected with the shunt coil m in
a suitable way.
In the application of the invention to a starting resistance switch the switch
arm proper c would also have fitted to it a spring to normally hold it on the dead
contact of the resistance, a catch device being provided upon the resistance
contact to hold the said arm on the said contact. In this case the arm c can
make no intermediate contact on the resistance.

page_text: 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: -
First. In a resistance switch and automatic cut-out for electric motors, the
combination with a suitable overload release and automatic cut-out device of
two independent arms (one spring-controlled) so arranged upon the switch's base
or slab in respect of the resistance contacts and the said release and cut-out
device that the one arm at certain times shall enclose or cover the other and at
other times be clear of it, for the purpose substantially as described.
Second. In a resistance switch and automatic cut-out for electric motors, the
combination with a suitable resistance of two independent arms c and d (one
spring-controlled) so arranged upon the base or slab a that at times the one covers
or protects the other and at other times the one is free of the other, stops e², e³,
and on the base a to limit the movement of the arms c and d, and an automatic
release constructed and arranged to work in combination with the arm d and
the contact h, substantially as described and set forth.
Third. In a resistance switch and automatic cut-out for electric motors, the
combination with a resistance e having stop contacts e2, 3, of two independent
armis c and d jointed on a common joint pin, the one arm being hollowed or made
open-sided to receive portions of the other arm when the two arms are coincident
and to cover or protect the said arm, a spring d controlling the arm d, a contact
piece i also on said arm d, a stop and a contact h, and an automatic magnetic
release g, having coils m, m², effecting the said release in the manner described.
Fourth. The devices described and set forth for determining the air gap
between the magnetic release g and the contact piece i of the arm d.
Fifth. A resistance switch and cut-out for electric motors constructed and
having its parts (inclusive of the short circuiting device s) arranged in the manner
specifically described and set forth.
1
W. P. THOMPSON & Co.,
11, Burlington Chambers, New Street, Birmingham,
Also at Liverpool, London & Manchester,
Patent Agents for the Applicants.