US1572929A - Short-circuiting device - Google Patents

Description

Feb. 16 1926.

W. H. HIMES SHORT CIRCUITING DEVICE Filed April 25, 1924 INVENTOR Wa/ter" /7f flimes WITNESSES! ATTORNEY Patented Feb. 16, 1926.

UNITED STATES PATENT. OFFICE.

WALTER n'il iinu'ns, F PITTSBURGH, PENNSYLVANIA, ASSIGNOR To WESTINGHOUSE nLEcTmc & MANU AcTURINe COMPANY, A CORPORATION or PENNSYLVANIA.

SHORT-CIRCUITING DEVICE.

A pplication filed April 25, 1924. seam No. 708,903.

To all whom it may concern; 4

- Be it known that I, \VALTER H. HIMES, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in 'Short- Circuiting Devices, of which the following is a'specification.

-My.r invention relates to centrifugally actuated short circuiting devices for dynamo-electric machines and it has particular relation to single-phase. motors of the com-.

mutator type that are adapted to operate, during the starting period, as repulsion speed, as induction motors.

In Patent No. 1,480,720, granted January 15, 1924,-to G. H. Garcelon, and assigned to the Westinghouse Electric and Manufac- 0 turing Company, there is described a shortcircuiting device for a motor of the above mentioned type, comprising a plurality of spherical contact members held in contact with the end face of the commutator by means of a conical bushing, which is pressed towardthe commutator by a spring around theshaft of the rotor. Upon acceleration, the spherical contact members move outwardly and establish aclosed circuit between'a plurality of the commutator bars and,the conical bushing. It has been found that the sliding friction encountered in devices of the prior art is highly undesirable. It is furthermore necessary to provide a starting device whereby the closed circuit between the commutator segments is effected, at a predetermined speed of rotation, with a quick and positive action. 40 "In short-circuiting devices of the prior art, in which spherical contact members have been used, these members have been wedged between the end-face of the commutator and the inclined surface of a spring-pressed guide member, whereby a rolling movement could only occur on one of said surfaces. The very appreciable friction which occurs at the other surface, as the spherical contact members move either outwardly or inwardly, not only materially increases the wear of the parts, but also greatly decreases the sensitiveness, positiveness and delicacy of operation and aged by long usage.

motors and, upon reaching a predetermined movement of these members to and from the short-circuiting osition.

Furthermore, in evices'of this character and even in improvements thereon, inwhich spherical members havebeen used as the contact elements, it has sometimes been found, particularly in the larger sizes, that the sphericalformation and surface smoothness of the elements would be seriously dam- Also in devices of prior art, it has been found that the'spheres provide substantially but a point contact, which results in defective operation of the device and produces additional irregularity in' the surface of the contact members.

Furthermore, in prior-art constructions employing spherical contact members, it has been found diflicult, if not impossible, to make these members of such pure copper as to give the desired efliciency to the operation of the device; it has also been found that the process of making a spherical member of such perfection as is required for such use, is of almost prohibitive cost; it has also been found that the use of spherical contact members has a definite tendency to divide the coils" of the retaining garter spring and thereby deform it and destroy its uniformity of construction, resiliency, sensitiveness and efficiency; and it has further been found that the use of spherical contact members wears undesirable grooves in the face of thecommutator, y In order to overcome the foregoing and other defects, therefore, I have devised an improved short-circuitingdevice, in which I have eliminated the use of spherical contact members 'and substituted therefor substantially cylindrical roller contact members. A further object ofmy invention is to provide a short-circuiting device that is 90 arranged as a self-contained and simple unit, permitting detailed, assembly and testing, independent of the machine into which it is incorporated and permitting the units to be readily interchanged or replaced.

With the foregoing and other objectsin view, my inventionconsists in the-particular construction, combination, arrangement and organization of parts hereinafter described and more particularly pointed out in the appended claims.

Fig. 1 is a view in vertical section through the upper half of a short-circuiting device embodying my invention, a portion of the associated motor shaft and commutator cylinder being shown. I

Fig. 2 is a view in end elevation of the device shown in Fig. 1, a part of the outer plate being broken away.

Fig. 3 is a detail view in transverse section, on line IIIIII of Fig. 1.

In Fig. 1 is shown a portion of a motor of the class hereinbefore described, comprising a rotatable commutator 1 and a co-operating sh'ort-circu'rting device 2, which is mounted upon the motor shaft 3. The commutator 1 has a plurality of segments 4, of any standard construction, and, is provided with a smooth front end face 5, having an inner portion 6 of insulating material.

The short-circuiting device 2 comprises a hub member 7, two substantially circular guide plates 8 and 9 and a plurality of roll.- ers 11 of any suitable conducting material such ascopper or bronze, the copper, however, being preferable, as will be further explained hereinafter. The rollers 11. are mounted between the guide plates 8 and 9. A substantially annular tension member 12, such as a garter spring, surrounds the rollers 11 and tends to retain them in a central nonconducting position, against radial outward movement resulting from centrifugal action.

The innerguide plate or retainer 8 is secured in position against a flange 13 extending from the hub member 7 adjacent the end face 5 of the commutator 1 and is provided with a plurality of substantially radially disposed slots 14. The outer guide plate 9 is secured in position against a shoulder 15 of the hub 7 by means of a circular or annular spring lock ring 16 wedged between the outer face of the guide plate 9 and an edge of annular groove 17 in the hub 7 The conducting members or rollers 11 are mounted loosely within the slots 14 and are adapted to have a rolling movement, along predetermined paths, upon the end-face 5 of the commutator 1 and to establish, in their outer position 11a, a closed circuit between a plurality of the commutator bars 6 and the outer extremities and sides ofthe slots 14 in the guide 'plate8.

In Fig. 3 is shown the arrangement of a roller 11 within its corresponding slot 14. The roller 11 is provided with centrally disposed axial pins or pivots 21 which extend laterally from the opposite sides of the roller 11 and'prevent the roller from being can pelled' through the slot when the shortcircuiting unit is removed from the motor, or when it is assembled prior to application to the motor. In operative position on the machine, the rollers 11 bear on the end face of the commutator in their movement up and down in the slots 14, when they are actuated in one direction radially outwardly by centrifugal force, or in the opposite' direction radially inwardly by the spring 12.

\Vhen the rollers 11 are in the position shown in full lines in Fig. l, which is their position of rest, no short-circuiting action is taking place. IVhen the rollers 11, by the action of centrifugal force, are thrown radially. outward to the ends of the slots 14,

as shown in dotted lines in Fig. 1 they contact with the commutator bars 4 and effect a short or closed circuit. During the movement of the rollers 11.up and down the slots 14, they are held in contact with the face 5 of the commutator 1 and commutator bars 4 by the tension of the garter spring 12 pressing against them.

The wedging action of the garter spring 12 forces the rollers 11 into proper operative position in engagement with the com- -11 radially outward, under centrifugal action, along the paths determined by the slots 14 in the guide plate 8, the outward movement of the rollers 11 being opposed by the force exerted by the garter spring 12. When the motor speed increases to a predetermined value, the rollers 11 move radially outward to a position where the garter spring 12 is diverted from a direct radial movement to the inclined conical portion 22 ofthe outer guide member 9, whereby the restraining action of the spring 12 is materially reduced and the rollers 11 move with a quick snap action, und'erthe impulse of centrifugal force, to their short-circuiting positions in contact with the ends of the commutator bars 4, as shown in the dotted lines 11a in Fig. 1. It should benoted thatalthough the total tension of the garter spring 12 is increased as the spring 1.2 is distended, the increased angle of application of its pressure upon the rollers 11, as they move radially outward in the slots 14, results in reducing the radial pressure.

When the speed of the machine or motor is reduced, the restraining or contractive force of the tension member or garter spring 12 gradually predominates over the centrifugal force acting upon the rollers 11 and causes them to recede and return to their initial position of rest and to break contact with the bars 4 of the commutator 1.

It will be noted, from the drawing, that the closed or short circuit established by the rollers 11 in their outer position depends upon a well-defined wedging action of the rollers against the outer ends of the slots 14 in the inner guide plate 8 and upon a plurality of line contacts between the peripheral surfaces of the rollers 11 ant? the ends of the commutator bars 4. The inner guide plate 8 carries the armature currents and effectively shunts the garter spring 12, in order to protect the latter from the destructive effect that might result were it permitted to carry current.

By the use of roller contact members, I am enabled to obtaina line contact between a roller and its cooperating member, and to overcome the defects resulting from the use of a spherical contact member, which gives only a point contact. I thereby prevent the wearing of grooves in the commutator face and ensure the short-circuiting of at least two commutator bars by each roller, thus increasing the efficiency of the apparatus.

Likewise, I am enabled, because of its shape, to produce a roller contact member of substantially pure hard drawn copper, which is a most desirable material from which toconstruct such a contact piece; whereas 95% purity is the nearest that can be attained to this requirement in forged spherical copper balls. At the same time, I am enabled to construct the roller at comparatively cheap cost, since the process of drawing a rod and cutting the same into rollers by automatic machinery is much simpler and cheaper than Elie forging process for-making a perfect all. Also, because of the form of roller contact members, I am able to make them with axial pivots or pins. By this means the locking of these members within the retaining cage, composed of the plates 8 and 9, is effected in a manner which is found to be more desirable and positive than when spherically shaped contact members are used.

In addition to the foregoing advantages,

it may be found desirable, when using a short-circuitinp; switch of the roller contact type on high speed machine, to make the rollers as light as possible, thus making possible the construction of a 3400 R. P. M. machine using the same spring as is used on an 1800 R. P. M. machine. can be accomplished by boring or otherwise cutting out the center portion of the roller, an advantage which is not to be obtained when the spherical type of contact member is used. I r

The garter spring 12 operates, in effect, like a flexible idler roller between the roller contact members 11 and the abutment member 9, thus wedging the roller members into contacting engagement with the end face of the commutator and substantially eliminat- :ng all sliding friction.

Such a result.

My short-eircuiting device 2, including the hub 7 the guide members 8 and 9, and the roller contact members ll and the spring 12, may be quickly and cheaply assembled as a separate, self-contained unit, by methods well adapted for quantity production.

The assembled short-circuiting unit may be fastened on the commutator shaft 3 by a spring lock ring 23, shown in Fig. 1 of the drawing, or by any other suitable fastenin means. The plates or guide members 8 and 9, have adjacent flanges or opposite portions 24 and 25 on their respective periphery, so that the spring 12 can not' fly out of operative position, in case ofover-speeding of the motor or breakage of the spring.

The offset portion 24 of the inner guide member 8 also serves to carry the ends of the slots 1% to points on the peripheral surface of'the rollers 11 remote from the commutator, thereby insuring the necessary wedging action of the roller contact members 11 be tween the commutator segments 4 and the ends of the slots 14, in the short-circuiting position as indicated indotted lines Fig. 1. \Vhile I have shown butone embodiment of my invention, I do not wish to be limited thereby, except as the state of the art and the appended claims may require; for it is obvious that certain modifications, changes, reorganization and combinations of parts may be made therein, without departing from the spirit and scope of my invention.

I claim as my invention:

-l. A centrifugal devicecomprising a cvlindrical roller which is movable radiallv outwardly under the action of centrifugal force, means for providing a surface against which said roller rolls, means for providing an idler roller bearing against said firstmentioned roller andfor yieldably restraining said roller against outward movement, and means for providing a surface against -which said idler roller rolls.

2. A centrifugal device comprising a cylindrical roller which is movable radially outwardly under the action of centrifugal force, means for providing a surface against which said roller rolls, means for providing air idler roller bearing against said firstmentioned roller and'for yieldably restraining said roller against outward movement, means for providing a surface againstwhich said idler-roller rolls, and electrical contact devices disposed to be actuated into open or closed position by the movement of said rollers.

3. A centrifugal contact-making device 4. A centrifugal contact-making device" comprising a plurality of annularly disposed cylindrical roller members which are movable outwardly under the action of centrifugal force, a cylindrical commutator memher having a plurality of peripheral segment members and having an endsurface against which said roller members roll, a oil spring closed upon itself for providing, in effect, a plurality of idler rollers bearing against said roller members and for yieldingly restraining the same against outward movement, and an abutment member, pro-' viding a surface against which the coils of said spring roll.

5. A centrifugal short-circuiting device comprising a plurality of annularly disposed cylindrical rolling members which are movable outwardly under the action of centrifugal force, a cylindrical commutator member having a plurality of peripheral segment members and having an end surface against which said rolling members roll, a

coil spring surrounding said rolling members, and an abutment member for said spring.

6. A centrifugal short-circuiting device comprising a plurality of annularly disposed cylindrical rollers which are movable out; wardly under the action of centrifugal force, a cylindrical commutator member having a plurality of peripheral segment members and having an end surface against which said rollers 'roll, a coil spring surrounding said rollers, and an abutment member for said spring, said abutment member having a conical surface.

7. A centrifugal short-circuiting device comprising a plurality of annularly disposed cylindricalrollers which are movable outwardly under the action of centrifugal force, a cylindrical commutator member having a plurality of peripheral segment members and having an end surface against which said rollers roll, a coil spring surrounding said rollers, and an abutmentmember for said spring, said abutment member having an inner surface substantially normal to the axis of rotation, merging into an outwardly inclined surface nearer its peripheral edge,

8. A centrifugal short-circuiting device comprising a plurality of annularly disposed I rollers which are movable radially outward.-

ly under the action of centrifugal force, a cylindrical commutator member having a plurality of peripheral segment members and having an end surface against which said rollers roll, a. coil spring surrounding said rollers, and means for providing an comprising a, cylindrical member which is movable radially outwardly under the action of centrifugal force, means for providing a surface against which said member rolls, an idler roller bearing against said member, means for providing a surface against which said idler-roller rolls, and means for yieldably restraining said member and roller against outward movement.

10. A self-contained speed-responsive attachment comprising a hub, a guide plate secured thereto and having substantially radially disposed slots, an abutment plate se cured to said hub in spaced relation to said guide plate, a plurality V of annularly disposed cylindrical roller members arranged in spaced relation between said plates and having rolling surfaces projecting through said slots, respectively, means for preventing the passage of the entire roller members through said slots, and a coil-spring surrounding said roller members and engaging said abutment plate. i

11. A self-contained speed-responsive attachment comprising a hub, a guide plate secured thereto and having substantially radial slots, an abutment plate secured to said hub in a spaced relation to said guide plate, a plurality of annularly disposed cylindrical' contact members disposed in the space between said plates and projecting partial'ly through said slots, respectively, and a coil spring surrounding said cylindrical contact members and engaging said abutmentstrainingmember, said guide means causmgthe initial outward movement of said cylindrical members to be opposed by substan tially the full action of said restraining member and causing the opposing action subsequently to become less effective whereupon said cylindrical members move with an increased velocity to close-circuit said commutator member.

14. The combination with a rotatable commutator member of-an electric motor, of a plurality of cylindrical close-circuiting members arranged to move outwardly under centrifugal force, a yielding tension member surrounding said cylindrical members for restraining said movement, a guide member for said cylindrical members and a guide member for said tension member whereby, upon the acceleration of said motor, said cylindrical members move outwardly, said guide member causing said cylindrical members, upon reaching predetermined portionsof their paths, to displace said tension member and to close-circuit said commutator with a snap action.

15. A short-circuiting device for the commutator cylinder of a dynamo-electric machine comprising a plurality of cylindrical contact members, means adapted to retain said members in spaced relation for engage ment with the end of the commutator cylinder and to guide the members in substantially radial paths, means for engaging said cylindrical members and placing the same under stress, and means for causing said cylindrical members, upon reaching a prede termined angular speed, to shift the point of engagement with said means and to move quickly to their short-'circuiting position.

16, In combination with a rotatable coml mutator member of an electrical machine,

subscribed my name this 16th day of April, 1924. i

WVALTER: H. HIMES.

Images