US681133A - Starting apparatus for electric motors. - Google Patents

Description

No. 6a|,|33. Patented Aug. 20, IBM. T. s. PERKINS.

START-INS APPARATUS FOR ELECTRIC IOTOBS.

(Applicltion flied June 19, 1001.)

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THOMAS S. PERKINS, Oh IDLEXVOOD, PENNSYLVANIA.

STARTING APPARATUS FOR ELECTRIC MOTORS.

SPEGIFIGATIGN forming part of Letters Patent No. 681,133, dated August 20, 1901.

Original application filed September 28, 1898, Serial No 692,065. Divided and this application filed June 19, 1901. Serial No. 65,172. (No modeld To all whom it may concern;

Be it known that I, THOMAS S. PERKINS, a citizen of the United States, residing in Idlewood, in the county of Allegheny and State of Pennsylvania, have invented a new and 'iSQfIll Improvement in Starting Apparatus )1 Electric Motors, of which the following is specification, this application being a divin of application Serial No. 692,065, filed me September 28, 1898. iIy invention relates to rheostatic switch paratus employed in electric circuits for gulating or controlling the operation of the tchines from or to which currents are supied.

One of the objects of my invention is to ,rovide improved starting mechanism for lirect-current electric motors, the structure and operation of the device being such that the movement of the rheostat switch-arm will serve to operate a double-pole switch to either open or close the line-circuit, according to its direction of movement.

A further object of my invention is to provide a means that shall act automatically upon the passage of an overload-current through the armature of a motor to shortcircuit the magnet that holds the rheost-at switch-arm in position during normal opera-' tion.

In the accompanying drawings, Figure 1 is a plan view of the motor-starting device, and Fig. 2 is a sectional View of the same.

The motor-starting device shown in the drawings comprises a slab or plate 1, of slate or marble or other suitable insulating material, on which are mounted the several switching devices to be hereinafter described.

A metal box 2 is provided with a central tube or bushing 22, of porcelain or other suitable insulating material, and contains a resistance-coil 3 and a body of cement 1, in which the coil is embedded. The resistance coil is indicated as having the shape of a spiral formed from a flattened helix of wire and as having a strip 5, of asbestos or other suitable insulating and heat-resisting mate rial, coiled therewith, so as to separate adjacent convolutions. Other forms of resistance may be employed, however, if desired. Leads 6 extend outward through the insulating-bushing 2 from proper points in the length of the resistance-coil and are connected to stationary contact pieces or buttons 7 and 7, arranged in the arc of a circle, the contactpiece 7 being several times the length of each of the buttons 7.

A switch-arm 8,haviug a suitable operatinghandle or projection 9, is pivotally mounted on the plate 1 and at the center of the circle in the arc of which the contact- buttons 7 and 7 are located, and is provided with a spring contact strip or blade 8. \Vhen the apparatus is not in operation, the arm 8 rests against a stop 10, it being moved to and held in this position normally by means of a coiled spring 11. The hub 12, at the inner end of the switch-arm 8, is provided with two gear- teeth 13 and 14, the former of which engages between two similar teeth 15 on a hub 16, pivoted adjacent to the pivot of the switcharm 8, the two pivots or hubs being electrically connected by a strip or plate 16. This hub 16 is provided with two arms 17 and 18, projecting at a considerable angle to each other. The arm 17 is provided with a socket, in which is mounted a contact-blade 19, this blade being insulated from the arm by suitable material 20. A magnet 21 is located adjacent to the last contact-button 7 of the series and serves when energized to hold the switch-arm 8 in contact therewith and the blade 8 in engagement with the last button 7 of the series, provided, of course, that the arm 8 has been first moved by hand to that position. If the switch arm is not itself of: magnetizable material, it must of course be provided with a magnetizable strip or plate to act as as an armature for the magnet.

The motor to be started and controlled is illustrated as having a shunt field-winding 22 only; but it will be understood that it may also have a series winding, if desired. One conductor 23 of the line-circuit is electrically connected to a stationary contact 24: and the other conductor 25 of the line-circuit is connected to a stationary contact 26, this contact and a similar contact 27 being bridged by the blade 19 of the double pole lineswitch when the latter is closed. In order that the magnet 21 may be short-circuited to release the arm 8 in case current passes to the armature that is liable to cause injury, I provide a stationary contact 29 and a movable cooperating contact-arm 30, adjacent to which is located an electromagnet 31. This contact-arm 30 must obviously be of magnet izable material or provided with a plate or block of such material, in order that it may be drawn toward the magnet 31 to engage the stationary cont-act 29 when the current through the magnet-coil exceeds a certain predetermined quantity. In order that the contact-arm 30 may be set for any desired current value, I provide a set-screw 32 and a stop-piece 33, againstwhich the end of the screw impinges.

In the operation of the device above described, assuming that the motor is at rest and it is desired to start the same, the switch-arm 8 is moved by hand in a clockwise direction, the movement serving by reason of the gear-tooth connection with the double-pole line-switch to bring the contactblade 18 into engagement with the line-terminal contact 24: and the blade 19 into engagement with the contacts 26 and 27 before the switch-arm blade 8 leaves the contactpiece 7, thus closing the line-circuit through the contact 24, blade or arm 18, the switchblade 8, the contact-piece 7, the entire resistance-coil 3, the magnet-coil 31, the ar mature 2S, stationary contact 27, blade 19, and stationary contact 26. The current divides at plate 16 and one portion passes through the magnet-coil 21 and the shunt field-winding 22 and joins the armature-current at the negative terminal of, the latter. A further movement of the switch-arm 8 will effect the cutting out of the resistancecoil 3 section by section until the last contact -point is reached, when the current through the magnet-coil 21 will serve to hold the switch-arm 8 in that position and the geartooth 14 will rest against the adjacent tooth 15 on the hub 16 of the line-switch, so as to prevent any accidental opening of the lineci'rcuit. During the operation of the motor the parts will remain in the position last indicated unless the current flowing to the armature should exceed the amount for which the contact-arm 30 of magnet 31 is set. If

this amount is exceeded, the magnet will bring the contact-arm into engagement with the stationary contact 29, and thus short-circuit the magnet 21. The switch-arm 8 being thus released, the spring 11 will throw it to its initial position and the line-switch will open the circuit, thus preventing any injury to the motor by reason of the excessive current. If either the line or main circuit or the motor-field circuit be opened, the switch-arm 8 will be released in the same manner and the spring 11 will return it to the contactpiece 7 as indicated in Fig. 1, a path for the discharge of the shunt field-magnet winding being thus, provided through the armature 28 and theentire resistance-coil 3.

The detailsof construction may be obviously varied in minor particulars without departing from the spirit and scope of my invention, and hence I do not desire to limit my invention except as may be necessitated by the state of the art.

I claim as my invention 1. In a starting device for electric motors, the combination with a subdivided resistance, of a switch-arm, a spring tending to move said arm to and retain it in its initial position, aseries of stationary contact-pieces in position to be engaged bysaid arm for cutting the subdivisions into and out of circuit successively, the first of said series of contact-pieces being of materially-greater length than the others, a double-pole line-switch the movable member of which is geared to said switch-arm so as to close the motor-circuit before said arm leaves thelong contact-piece, and an electromagnet serving, when energized, to hold the switch-arm in its full-on position and the line-switch. closed.

2. The combination with an electric motor having a shunt field-magnet winding, of a starting resistance, a resistance varying switch comprising a long contact-piece, a series of short contact-pieces and a cooperating contact-arm operated by hand to cut the resistance out of circuit progressively and by a spring in the opposite direction, a doublepole line-switch having its movable member geared to said switch-arm whereby the lineswitch is closed by the forward movement of said arm and during its engagement withthe long contact-piece, an electromagnet for holding the line-switch closed and the resistanceswitch arm in the minimum resistance position, and means for automatically short-circuiting said magnet when the armature is subjected to an overload current.

3. The combination with an electric motor having a shunt field-magnet winding, of a starting resistance, a resistance varying switch comprising a series of stationary contacts anda cooperating contact-arm operated by hand to cut the resistance out of circuit progressively and by a spring in the opposite direction, a double-pole line-switch having its movable member geared to the resistance-switch to effect the closing of the motor-circuit by the initial forward movement of theresistance-switch arm, an electromagnet for holding the line-switch closed and the resistance-switch arm in the minimum resistance position, and a circuit-closing device actuated by an excessive flow of current to the armature to short-circuit the holdingmagnet.

In testimony whereof I have hereunto subscribed my name this 17th day of June, 1901.

THOS. S. PERKINS.

Witnesses:

JAMES B. YOUNG,

WESLEY G. CARR.

3 l i l r It is hereby certified that Letters Patent No. 681,133, granted August 20, 1901,

upon the application of Thomas S. Perkins, of ldlewood, Pennsylvania, for an Startin A aratus for Electric Motors were erroneousl r issued whereas said Letters Patent should improvement in to said Perkins as sole owner of the invention have been issued to the Westinghouse Electric (is lllanirfaeturing Company, of Pennsylvania, said XVestinghouse Electric & Manufacturing Company being assignee of the entire the assignments of record in this Otlice and interest in said invention, as shown by that the said Letters Patent should be read With this correction therein that the same may conform to the record of the ease in the Patent Office.

this 3d day of September, A. D., 1901.

F. L. CAMPBELL, Assistant Secretary oft/1e Interior.

Signed, countersigned and sealed [sEAL] Countersigned E. B. MOORE,

Acting Cmmnissioner of Patents.

Correction in Letters Patent N oi iiiilfliifi.

1 It is hereby certified that Letters Patent No. 681,138, granted Augusti20, 1901, upon the application of Thomas S. Perkins, of Idlewood, Pennsylvania, for an improvement in Starting Apparatus for Electric Motors, were erroneously issued to said Perkins as sole owner of the invention; whereas said Letters Patent should have been issued to the Westinghouse Electric (is Manufacturing Company, of Pennsylvania, said Westinghouse Electric & Manufacturing Company being assignee of the entire interest in said invention, as shown by the assignments of record in this Otfice and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed, countersigned, and sealed this 3d day of September, A. D., 1901.

[SEAL] F. L. CAMPBELL, Assistant Secretary of the Interim".

Countersigned E. B. MOORE,

Acting Cornnn'ssioner of Patents.

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