Automatic Device for Removing Resistance in Starting Electric Motors and Replacing same.
Year: 1894

page_text: CUM LEIM
DIECIFICATION.
Automatic Device for Removing Resistance in Starting Electric
Motors and Replacing same.
I, GEORGE HERBERT WHITTINGHAM, of No. 703 Equitable Building,
Baltimore, Maryland, United States of America, Electrical 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 :-
This invention relates to an automatic device for removing resistance in starting
electric motors and replacing same, and has for its object to gradually reduce the
resistance in the armature circuit of the motor automatically when the current is
turned on and the motor starting by cutting out the coils of resistance one after
the other from that of the greatest resistance to that of the least resistance, and
maintaining it in this position during the running of the motor, so that when the
current through the motor is first completed to start the motor the current will meet
with the greatest resistance and when the motor is fully running there will be the
least resistance to the passage of the current; this is done to prevent the burning
out of the armature of the motor when starting. When the current is shut off, this
device operates to automatically replace the resistance in the circuit in readiness
to be started again. By my invention the power for operating the resistance-
controlling device is obtained from the motor itself.
In order to make the improvements clearly understood I have shown in the
accompanying drawings means for carrying the same into practical effect, without,
however, intending to limit my invention to this particular construction, for the
invention as broadly conceived by me and as defined in my claims, may be embodied
in many other forms.
In the drawings,—
Figure 1 shows an end view of a motor provided with my improved automatic
resistance controlling device.
Figure 2 is a horizontal section of the device taken on the line 2-2 of Figure 1.
Figure 3 is a section through the resistance plates taken on line 3-3 of Figure 1.
Figure 4 shows a diagram of the circuits.
The letter, A, designates the field-magnets of the motor and A', the coils
thereof; B, designates the armature and B, the armature-shaft which is journalled
in bearings, C, on the base, C, of the motor. A suitable upwardly-projecting
frame-work, D, is bolted to the outside of the bearing-block, C', and base, C, at
the commutator end of the motor. Mounted on this frame-work, D, is a segment-
shaped ratchet-bar, G; a holding pawl, f, and electro-magnets, H, all hereinafter
referred to. I, designates the commutator brushes.
In the present instance the commutator end of the armature-shaft, B', is extended
beyond the outside of the bearing-block, C', and has mounted thereon an eccentric, E,
fastened by a key, a; around this eccentric is a split eccentric strap comprising two
parts, b, b', held together by suitable bolts 3. The upper half, b, of the eccentric
strap has a threaded socket, 62, to receive one end of an eccentric rod, E', on the
other end of which is mounted a yoke, F, having two arms, c. The ratchet pawl, G'
is pivoted on a pin, d', between the said arms, c, and its free end engages the
teeth, d, of the segment-shaped ratchet-bar, G, connected with a hub which is
pivoted on a stud, e, fixed to the upwardly-extending frame, D. The ratchet-
teeth, d, extend along only a portion of the length of the bar, G, and the remainder
has a smooth surface. The ratchet-pawl previously referred to, has a depending

page_text: arm, d², which engages the free end of a leaf-spring, ³, attached to the yoke, F;
the function of this spring is to keep the pawl in engagement with the teeth of the
ratchet-bar, G.
A holding pawl, f, pivoted on a stud, f', also on the frame, D, has a hook-end, 2,
to also engage the teeth, d, of the segment ratchet-bar, G. This pawl has a
depending arm, f³, to engage the ratchet-pawl, G, for a purpose hereinafter
described. A pair of electro-magnets, H, have position on the frame, D, opposite
the segment ratchet-bar, G, one end of each magnet-core, g, being fastened in a rib
or flange, g', extending across the fixed ends of the magnets, said flange, gl, being
integral with the frame, D. A longitudinally-movable rod, J, passes between the
electro-magnets and one end extends through the flange, g', which forms one
bearing therefor. This extending end of the rod, J, is provided with a head, J²,
having a lateral hole which receives a cross-pin, i.
A pair of link-plates, L, one at each side of the head, J2, have one end pivoted
on the pin, i, and the other end on the pin, d', between the ratchet-pawl, G', and the
arms, c, of the yoke, F.
An additional bearing, 9, on the frame, D, is provided for the other end of the
rod, J. An armature, J, is fixed on the rod, J, between its bearings, g', g², and
extends cross-wise of the same and co-acts with the electro-magnets, H. A spiral-
spring, h, around the rod, J, is interposed between the flange, g', and armature, J',
and serves to keep the armature normally away from the magnets, H.
It will be seen that when the magnets, H, are not energized the armature, J',
will not only be away from the magnets but the ratchet-pawl, G', and holding-
pawl, will be disengaged from the teeth of the ratchet-bar, G, which is thereby
allowed to fall against a suitable stop, D', on the frame, D.
A contact-shoe, M, made up of a series of plates, j, adjacent to one another is
pivoted on an arm, N, attached to the segment-shaped bar, G, but insulated there-
from. A plate, j', of spring material, has one edge fixed to the said pivot-arm, N,
and its other edge slitted to form a series of spring tangs,, each of which bears on
a corresponding plate, j. of the contact-shoe, M.
A series of contact-plates, k, k³, k², etc. insulated from each other are respectively
connected with a resistance coil, O. These contact-plates are mounted on the
frame, D, on an arc described from the pivot stud, e, and are successively engaged
by the contact-shoe, M, which, however, is always in engagement with one of them.
The operation is as follows:-
When the motor is connected with the line, 1, 1, by moving the switch, P, the
current will flow along the line, m, through the shoe, M, resistance coil, O,
armature, B, then along the line, m¹; back to the switch; the current will also flow
from the line, m, along line, n, coil, A', of field-magnet and then return to line, m³,
along line, n; another portion of the current from main line, m, will flow along
line, o, to electro-magnets, H, and then return along line, o, to line, m'.
The current by flowing as just stated will energize the field-magnets and
armature of the motor and at same time the electro-magnets, H, which will
attract and move the armature, J', against the action of the spring, h, whereby the
pawls, G', and, f, are brought into engagement with the teeth of the ratchet-bar, G.
Now as the current has also gone to the field-maguets and armature the latter will
be caused to rotate with its shaft, imparting motion to the eccentric which in turn
reciprocates the eccentric-rod and pawl, G', which latter lifts the ratchet-bar, G,
one tooth at a time until the smooth surface of the ratchet-bar reaches the said
pawl whereupon the upward movement ceases, the holding-pawl, f, co-acting with
and holding the bar elevated as the ratchet-pawl, G', retracts. By this intermittent
upward movement the shoe, M, connected with the ratchet-bar, G, is moved over
the contact plates of the resistance coil beginning with the one of greatest resistance
and gradually diminishing until the last plate is reached where there is practically
no resistance. When the shoe, N, has reached this last plate, k, the pawl, G,
simultaneously reaches the smooth surface on the ratchet bar, G, and consequently
will not lift the bar any higher. When the shoe, M, has reached this last plate, k*,-

page_text: the point of lowest resistance, the said circuit is maintained thereat during the run
of the motor.
It will now be seen that when the current is shut off by the switch, P, the field-
magnets, armature and electro-magnets will become inert, and consequently the
pawls, G', and, f, be disengaged from the ratchet-bar, G, which will then fall and
the shoe, M, again brought into contact with the plate, k, indicating the greatest
resistance of the coil, whereupon the apparatus is in readiness for again starting
the motor.
It is obvious that a second pair of electro-magnets, H', indicated by broken lines
in Figures 1 and 4, could be placed in the circuit with the electro-magnets H, and
energized simultaneously therewith; this second pair of magnets would also be
mounted on a frame, D, and would attract an armature, Q', in broken lines,.rigid
on one arm of the ratchet-bar, G, so that when the pawl, G', has lifted the ratchet-
bar, G, as high as it can and is in engagement with the tooth adjoining the smooth
surface, the magnet, H', will elevate the bar slightly higher to prevent the pawl
hammering up against the said last tooth, but allow it to play freely on the smooth
surface of the ratchet-bar.
It will also be seen that instead of connecting the starting and stopping
mechanism as here shown it could be driven independently, that is, a small motor
could be employel and an independent circuit for this auxiliary motor and the
electro-magnets, H, used, but said circuit made simultaneous with the one through
the main motor, which latter circuit passes only through the shoe, M, and resistance
coil, O, of the starting mechanism. The two are in other respects independent of
one another.
It will be further observed that the two could be connected up mechanically, as,
for instance, by a belt from the motor driving a shaft on which the eccentric is
mounted and the electro-magnets suitably connected in the line circuit as it leaves
the switch.
In the present case the segment-shaped bar, G, is shown to be moved by the
agency of the reciprocating ratchet-pawl, G₁, and this particular mechanism
produces au "intermittent" movement of said bar, G, and the contact shoe which
it carries; it is obvious, however, that a continuous movement may be imparted to
the said bar and the shoe over the contact plates, by simply substituting a revoluble
worm for the said reciprocating pawl, the revoluble worm to engage the teeth of
the segment bar. The revoluble worm here referred to might be driven by the
arinature shaft, or by an independent motor.
It will now be seen that the main object of my invention is to provide an
automatic device for cutting out gradually the resistance to the current flowing to
the motor when the same is turned on, so that when the motor is fully running
there will be practically no resistance to the passage of the current, and when the
current is shut off to again introduce the said resistance automatically in readiness
for again starting.
By this means of controlling the flow of the current, the motor will always be
governed by its load, that is, when the load is heavy the resistance will slowly
and gradually be cut out or diminished until the full speed and power is obtained,
the motor starting up slowly, but when the load is light the motor will start up
fast and the resistance rapidly cut-out or diminished thus allowing the motor to speed
up quickly.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is;
1. In an automatic starting device for electric motors, the combination of a
motor; a resistance in series with the armature when starting the motor; a contact
shoe engaging the resistance; and a direct mechanical connection between the
armature and the contact shoe, whereby each revolution of the armature imparts
to the contact shoe a positive movement and gradually cuts out the resistance from

page_text: the armature circuit and maintains said circuit at the point of lowest resistance
during the run of the motor.
2. The combination of a motor; a resistance coil in electrical connection with
the armature a movable contact device in circuit with said coil; a pawl and
ratchet operated by the motor armature and adapted to impart to the contact
device a limited movement in the direction which reduces the resistance of the
armature cirenit; and means for disengaging the pawl and ratchet when the supply
of electricity is cut off.
3. In an automatic starting device for electric motors, the combination of a
motor; a resistance in series with the armature when starting the motor; a contact
shoe engaging the resistance; a direct mechanical connection between the armature
and the contact shoe which is operative in the direction of cutting out the resistance
from the armature-circuit, whereby said circuit is maintained at the point of lowest
resistance during the run of the motor; and further means whereby the cessation
of the current disengages the said mechanical connection and allows the contact
shoe to return to its normal position where the highest resistance is replaced, for
the purpose set forth.
4. In an automatic starting device for electric motors, the combination of a
motor; a resistance in series with the armature when starting the motor; a contact
shoe engaging the resistance; and mechanism to impart to the contact-shoe a
positive movement in the direction of cutting out the resistance from the armature-
circuit and maintain said circuit at the point of lowest resistance during the run of
the motor.
5. In a resistance controlling device for electric motors, the combination of the
field-magnets; the armature; a resistance coil; a series of contact plates each
connected with the said coil; a movable ratchet-bar; a contact shoe connected
with the said ratchet bar and moving over the contact plates successively; said
field-magnets, armature, resistance coil and contact shoe all being connected with a
line circuit; a reciprocating ratchet-pawl to engage the said ratchet-bar and impart
movement to it and the contact shoe; and means to disengage the pawl from the
ratchet-bar when the motor-circuit is broken to allow the ratchet-bar and contact
shoe to return to their normal position.
6. The combination of a motor; a resistance coil in electrical connection with
the armature; a movable contact device in circuit with the said coil; an eccentric
on the armature-shaft; and a pawl and ratchet operated by the eccentric and
imparting movement to the contact device to reduce the resistance of the
armature-circuit.
7. In a resistance controlling device for electric motors, the combination of the
field-magnets; the armature; a resistance coil; a series of contact plates each
connected with the resistance coil; a contact shoe to engage the said plates and
in circuit with the resistance coil, field-maguets, armature and line circuit; a
movable segment-shaped bar carrying the said contact shoe; and means to impart
a positive movement to said bar and to the contact shoe in the direction which
reduces the resistance of the armature-circuit.
Dated this 27th day of November 1893.
GEORGE HERBERT WHITTINGHAM.