Year: 1897

page_text: Date of Application, 1st June, 1897-Accepted, 10th July, 1897
I, GEORGE AUGUSTUS MOWER, of 75 Queen Victoria Street, in the City of London,
Engineer, 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 :-
My invention relates to starting switches, rheostats or resistance-boxes for electric
motors, of the kind or class in which an automatic electro-magnetic circuit-breaker
or cut-out is employed.
The object of my said invention is to provide an improved apparatus of this kind
or class, whereby the motor-circuit can be closed and the starting resistance then
wholly or partially cut out of the said circuit, as may be desired, and then, upon
the flow of an abnormal current through the electric motor, the starting resistance
will be gradually put into circuit and the circuit opened or broken automatically,
thus protecting the motor and preventing damage thereto; my said invention also
affords the means for automatically cutting the motor out of circuit when the flow
of current ceases, so as to prevent injury to the motor when the current is again
turned on.
In my improved apparatus I employ the usual movable element or contact-arm
adapted to be moved over a series of contacts to first close the motor-circuit through
the starting resistance, and then to cut out the starting resistance step by step.
current is
I combine, with the said movable element or contact-arm, suitable means for
retaining the same in position to close the notor-circuit with either the whole or
a portion of the starting resistance cut out, while the normal
flowing, and for automatically releasing the said arm and moving it back so as to put
in the resistance step by step and then open the circuit, when the current exceeds a
predetermined value, or ceases to flow.
I also
For this purpose I employ a retaining electro-magnet the armature of which is
provided with means whereby, when it is attracted, it will retain the contact-arm in
The
position upon one or other of the contacts of the rheostat as may be desired.
said retaining electro-magnet is preferably provided with two coils wound to oppose
each other, and of equal strength, one of the coils being short-circuited.
provide a releasing electro-magnet which, upon the passage of an abnormal current,
will act to open the short-circuit, thus connecting the oppositely wound coils of the
retaining electro-magnet in circuit, so that the said magnet is de-energized and the
contact-arm released. The said arm is then moved through the agency of a spring or
otherwise to put in the starting resistance step by step, and finally to open the
motor-circuit. It is obvious that the action will take place in the event of a cessation
of the flow of current to the motor.

page_text: In the accompanying drawing, I have shown how my said invention may be
conveniently and advantageously carried into practice.
Figure 1 is a plan of one form of my improved apparatus, some of the parts being
removed, and the contact-arm being shown in position to exclude the whole of the
starting resistance from the motor-circuit.
Figure 2 is a similar view, showing also the circuit connections and illustrating
the application of the controller to a series motor, the contact-arm being shown as
held in position by the retaining electro-magnet, upon the second contact of the
series.
5
The contact-arm a is movable over a series of terminals or contacts 61, 61, between 1
which are connected the.coils c, c of the starting resistance. A dead terminal b is
provided, and, when the contact-arm rests upon the same, the motor-circuit is open.
Stops e, e limit the movement of the contact-arm a. A curved contact-plate d is
provided, with which the under face of the contact-arm a, or a spring mounted
thereon, engages to complete the circuit between the said contact-plate and either of
the contacts b¹ upon which the contact-arm a may rest. The contact-arm a is
provided with a toothed segment a¹, and one end of the armature-lever f¹ of a
retaining electro-magnet f is adapted to engage with the teeth of the said segment
to maintain the contact-arm in any position to which the same may be moved, so as
to keep the motor-circuit closed with the whole or a portion of the starting resistance
cut out. A coiled retracting spring p is provided for moving the contact-arm to the
left when released. The retaining magnet f is provided with two coils f2, f3 which
are oppositely wound, and have equal effect, so that, when both are traversed by the
current, they neutralize each other and the retaining magnet is de-energized. The
opposite ends of the coil f³ are connected by conductors f, f with mercury cups fo, f
within which rest contact-ends g³, g³ of a bridge-piece mounted upon the armature-
lever g of a releasing electro-magnet g, the said lever being pivoted at g² and resting
upon a nut h screwed upon a rod h¹ and locked in position by a lock-nut h². Upon
the armature-lever g¹ is fixed an index k moving over a graduated scale k¹ upon the
magnet. By means of the nut h, the air-gap between the armature and the pole-
piece of the releasing magnet may be adjusted so as to cause the said magnet to
respond to any predetermined maximum current strength.
The current passes from the generator by the conductor to the binding post m,
thence by the conductor 2 through the releasing magnet g to the contact plate d,
thence through the contact-arm a to one or other of the tera inals or contacts 61,
and thence by the contact 3 through the coil f2 of the retaining electro-magnet, to and
through the short-circuit of the coil f³, that is to say, through the conductor f³,
cup f, bridge-piece 94, 95, cup f, and conductor f, thence to the binding post mi
and through the coils o², o², o¹ of the motor back to the generator b. The retaining
electro-magnet is thus energized and maintains the end of the armature-lever f¹ in
engagement with the toothed segment a¹.
When an abnormal current flows through the motor, the releasing magnet g
attracts its armature g¹, thus opening the short-circuit about the coil f₁ of the
retaining magnet, so that the said retaining magnet is de-energized by the combined
effect of the current flowing through its two coils f,f. The spring then draws
the armature-lever f¹ out of engagement with the teeth of the segment a¹, thereby
permitting the spring p to move the contact-arm to the left to put in the starting
resistance and finally open the circuit by bringing the contact-arm a onto the dead
terminal b.
It will, therefore, be seen that, in starting the motor, the contact-arm a can be
moved over the series of contacts b¹ so as to cut out the whole or any desired portion
of the starting resistance, and will then be retained in position by the armature f¹ of
the magnet so long as the value of the current does not exceed the predetermined
limit; but, when this limit is exceeded, the magnet g will cause the magnet f to be
de-energized and the contact-arm a, being thus released, will be moved back by its
spring p so as to first put in all the starting resistance and then open the circuit.
In place of the retaining magnet wound with opposing coils as above described, I

page_text: can, if desired, use a single-coil magnet arranged to be short-circuited by means of
the releasing magnet so as to permit the return movement of the contact arm when
the current exceeds a predetermined value or ceases to flow.
While I have illustrated my invention as applied to a series motor, it is equally
applicable to other types of motors. The term "electro-magnet
" as used in the
description and claims comprehends both electro-magnets in the restricted meaning
of that term, and solenoids.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is:-
1. An apparatus for the purpose above specified, in which there is combined with
the retaining electro-magnet, a suitable device controlled thereby for holding the
movable element or contact-arm in position upon either of the contacts of the series
so as to keep the motor-circuit closed with either the whole or a portion of the
starting resistance cut out, while the normal current is flowing, and a releasing
electro-magnet for automatically releasing the said arm and permitting its return
movement when the current exceeds a predetermined value, or ceases to flow,
substantially as, and for the purposes, hereinbefore described.
2. The combination, with the movable element or contact-arm of a starting switch,
rheostat or resistance-box, of a retaining electro-magnet for locking the same in
position and provided with opposed windings, a releasing electro-magnet for normally
maintaining one of the said windings of the said retaining electro-magnet out of
operative condition, and putting it into operative condition when the current exceeds
a predetermined value, or ceases to flow, and means for moving back the said arm,
when released, to change the condition of the circuit, substantially as, and for the
purposes, above specified.
3. The combination, with the movable element or contact-arm, of a suitable device
controlled by an electro-magnet for retaining the same in position upon either of the
contacts of the series so as to keep the motor-circuit closed with the whole or a
portion of the starting resistance cut out, a releasing electro-magnet adapted to
respond to an abnormal current to de-energize the said retaining magnet, means for
moving back the said arm, when released, to change the condition of the circuit, and
means for adjusting the armature of the said releasing electro-magnet to respond to
any predetermined current strength, substantially as, and for the purposes, above
specified.
4. The combination, with the contact-arm, of a toothed segment mounted thereon,
a retaining electro-magnet and a catch or pawl on the armature-lever thereof for
engaging with the teeth of the said segment to maintain the contact-arm in position
upon either contact of the series, and means for automatically releasing the said
contact-arm and moving it back when released, substantially as, and for the purposes,
above specified.
5. The improved apparatus constructed substantially as described with reference
to the accompanying drawings and operating as, and for the purposes, above specified.
Dated the 1st day of lune 100'7
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.