US2131603A - Operating mechanism - Google Patents

Description

Sept. 27, 1938.

c. THUMl M 3 OPERATING MECHANISM Filed April 30, 1937 .30 Inventor: Cori Thu i'm,'

by v His Attorney.

Patented Sept. 27, 1938' OFFIE OPERATING MECHANISM Carl Thumim, Lansdowne, Pa, assignor to General Electric Company, a corporation of New York Application April 30, 1937, Serial No. 139,903

9 Glaims.

.10 rugged in construction.

In the application of cam-operating mechanisms of the above described character to means such as, for example, a circuit breaker operable between open and closed circuit positions, it is 3 desirable that the cam assume a predetermined angular position at the beginning of the closing operation with respect to the means to be operated. This is particularly important where the circuit breaker mechanism is of the trip-free type wherein a collapsible linkage normally maintained in the thrust-transmitting position by tripping means coacts directly with the motor-driven cam. The operating or Working stroke in this case is the circuit-closing stroke, at the end of which the motor is automatically deenergized.

Since the closing stroke must be positive and fast a comparatively large amount of kinetic en ergy is stored in the rotating mass at the end of the stroke.

High speed braking means has been proposed for stopping the cam but, since in many cases instant dissipation of the large amount of kinetic energy is impractical and may even cause damage to the mechanism, the cam, in accordance with the present invention, is permitted to overtravel and the kinetic energy is gradually dissipated in friction and by other means. Further, in accordance with my invention the cam is automatically centered or restored to the desired predetermined angular position prior to another operating stroke, thereby permitting a high speed operating stroke uniform in time.

My invention will be more fully set forth in r the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing Fig. 1 is a partly diagrammatic view of a cam-operating mechanism embodying the present invention in the open, reset position in readiness for a working stroke; Fig. 2 is a partial View of the mechanism in the closed position, i. e., at the end of a working stroke, and Fig. 3 is a View similar toFig. 1 showing a modified form of my invention.

The operating mechanism illustrated by Fig. 1 comprises an electric motor I operatively connected through suitable gearing 2 and any operat- 5 ing shaft diagrammatically indicated at 3 to a r0- tatable cam t. The cam A is provided with a suitably designed operating face 4 and is secured to the shaft 3 so as to be rotated in a counterclockwise direction as viewed upon energization 10 of the motor I.

' The means to be actuated is generally indicated at 5 and may comprise the operating rod of an electric circuit breaker, for example. The rod 5 is shown in the open position and is operatively ;l related to the cam through a collapsible thrust transmitting linkage indicated at n. The linkage ,is normally held in thrust-transmitting position by a tripping means indicated at I. With the linkage in the open and reset position shown, a 20 revolution of the cam 4 is effective to cause a working stroke, the completion of which is indicated by the linkage and operating rod in the dotted line positions. I

The thrust-transmitting structure can be of 25 7 any suitable design, the one shown by way of example comprising a main toggle 89 including a roller It which coacts with the operating face 4 of the cam. The toggle link 8 is pivotally connected at one end at H to a guide link l2 hav- 3n ing a fixed pivot 13, and the toggle link 9 is pivotally connected at It to a lever l5 which is in turn pivotally connected at IE to the breaker operating rod 5. The pivot ll of the toggle link 8 is normally held fixed by the tripping means I, .35 so that when the toggle 8-9 is straightened at its knee joint ll by the cam, the lever i5 is rotated about its fixed pivot It in a clockwise direction to lower the operating rod 5.

The tripping means 1 specifically comprises a 4n tripping toggle I92t connected respectively to' the main toggle pivot H and to a fixed pivot 2|, and a coacting latch 22. The latch 22 which is rotatably mounted at 23 is adapted to engage a roller 24 carried by an extension 26 of the toggle .45 link 28. An extension IQ of the toggle link [9 coacting with the fixed pivot 2! maintains the toggle in an underset position so that when the latch 22 is moved out of restraining engagement with respect to the roller 24, the toggle |9Zil 50 collapses under the thrust exerted at the pivot I i. t The toggle 8-9 is no longer in thrust-transmitting position and is free to collapse, permitting reverse movement of the operating rod 5 under bias of spring 5' to the solid line position shown. 55

The latch 22 can be controlled in any suitable manner, as by the conventional tripping solenoid 25 or by independent manual means indicated at 26.

Fig. 2 illustrates the thrust-transmitting linkage in the restraining or closed position with respect to the operating rod 5. In this position the knee joint ll of the toggle 89 is overset and engages a stop member 21. The linkage is thereby eifectively locked in this position with respect to opposing thrust tending torotate the lever l5 counterclockwise as long as the toggle pivot H is held fixed by the above-described tripping means. When the tripping means is actuated in the manner above indicated the tripping toggle l9-20 is no longer restrained by the latch 22 and buckles, permitting the toggle pivot l l to move about the fixed pivot l3 in a counterclockwise direction under the influence of the reacting forces tending to cause opening movement of the breaker rod 5. When the toggle 89 has collapsed and the lever 15 rotated counterclockwise to the initial position shown in Fig. 1 wherein the roller l0 again engages the operating face or low point of the cam, the tripping toggle Iii-28 is again stretched and extended so that the roller 24 rides beneath the latch 22. In this position: the mechanism is reset and in readiness for another cam operation.

The motor control system generally indicated at 28 is adapted to deenergize automatically the motor after a working stroke of the cam and to prevent a subsequent operation in the absence of a further positive control operation by the operative. This control system per se forms no part of the present invention and is described and claimed in a co-pending application of Carl Thumim and Thellwell R. Coggeshall, Serial No. 59,080, filed January 14, 1936 for Motor control system.

The control system comprises a control source of power indicated at 29 from which the motor I is energized through a motor contactor 30. The motor contactor operating coil 3| is adapted to be energized thrugh the operatives switch 32 and a limit switch at 33. Accordingly, in order to initiate energization of the motor the operative closes the switch 32 thereby causing closing of the motor contactor 30. This operation seals the circuit of the contactor coil through auxiliary contacts at 34 in so far as the operatives switch is concerned, so that the motor will not be deenergized in the middle of the operating stroke by opening of the switch at 32.

The motor is automatically deenergized at the end of the stroke by means of a member 35 secured to the cam shaft 3. The member 35 is provided with a pin .36 which picks up a loosely pivorted arm 31. At the end of the stroke. the member 37 lifts the pivoted switch member 38 so as to open the motor contactor coil switch at 33, thereby opening the motor contactor. At the same time the auxiliary switch at 39 is closed, thereby energizing the coil 40 in the event that the operatives switch 32 is held closed. The switch member 38 is accordingly held in that position through the coacting armature 43-. It is therefore necessary that the operative open the switch 32 and again close the same before another operation can be initiated. Repeated operations o-r pumping of the mechanism is thereby precluded.

For most efficient operation of a cam, it is clear that the maximum. amount of useful dwell be gainfully employed, i. e., the low region should be limited to a minimum.

Due to inertia of moving parts, a certain amount of over-travel is unavoidable. The amount of over-travel permitted determines the extent of the low region.

Various means have been employed for limiting over-travel such as mechanical and electrical braking means, but these are attended by the hazard of straining working parts and by an indeterminate final cam position that is due to un'- avoidable operation of the control motor on varying voltages. This results in varying amounts of kinetic energy requiring dissipation after deenergization of the motor.

The present invention discloses a new means for causing the cam to come to rest at approximately the same position after motor cut-01f, irrespective of the speed of the motor and momentum of the moving parts, thus permitting the low or ineffective portion of the cam. periphery to be reduced to a working minimum.

The operating movement of the cam 4 is such that the high point of the cam clears the roller l0 when the toggle 89 moves to its over-set position illustrated by Fig. 2. If the cam were instantly stopped at that point roller l0 could en gage the low point of the cam immediately upon tripping so that the tripping means would immediately reset. 7

Assuming, however, that the roller it! drops to an intermediate point on the cam. face, the tripping means cannot be reset until a partial revolution of the cam is effected. However, there is present the practical difficulty of synchronizing the speed of rotation of the cam with the toggle resetting operation so that when the low point of the cam passes under the main toggle roller III, the tripping means at 1 resets without fail.

This might be accomplished safely by designing the cam with a low point dwell period of but such cam design is obviously unsatisfactory as but 180 remain for the working face.

For centering the cam prior to an operating stroke so as to insure resetting of the tripping means at a predetermined point on the cam and for conserving the maximum efiective "dwell duration of the cam, the rotating structure is permitted to over-travel even to the extent of several revolutions, and means are provided for gradually and safely dissipating the kinetic energy and for returning this energy in part to the cam for restoring it to a predetermined position.

To this end the cam shaft 3 is operatively connected to spring structure 4! adapted to be tensioned when the cam 4 passes the predetermined position above referred to. Specifically, a pair of springs 42 are mounted on guide rods 43 between a pair of cross-heads 44 and 45. The cross-head 44 is guided on the rods 43 and is connected through a crank 46 and gears 41 and 48 to the cam shaft 3. The cross-head 45 is pivotally mounted at 49 for permitting oscillatory movement of the opposite end of the spring structure.

It will be noted that the gear 48, which is fixed to the shaft 3, operates through the gear 41 the movable cross-head 44 in piston manner to compress the springs 42 when the cam rotates beyond the position shown. Assuming noW that the cam rotates 45 degrees beyond the position shown before the kinetic energy in the rotating structure is dissipated, the energy stored in the springs 42 acting through the cross-head 44 now rotates the shaft gear 48 in the opposite direction so as to return and center the cam. In order to insure proper positioning of the cam under all conditions the gear 41 is provided with twice as many teeth as the gear 48 so that regardless of whether crank 455 stops at its upper or lower center position the cam 4 always stops at the proper position.

By insuring a predetermined starting position for the cam, a uniform operating time is possible as well as high speed operation of the cam due to the fact that the tripping means is already reset.

Fig. 3 illustrates the same principle of cam resetting, except in this case a tension spring 50 is directly connected to an end of the shaft 3 through an arm 5|. The spring 50, as in the case of the springs 42, opposes movement of the cam 4 beyond the predetermined starting position and tends to restore the cam to its centered position after the kinetic energy is dissipated. However, it will be noted that it is possible for the spring 50 to assume a dead center position when the shaft is 180 degrees from the position shown. For overcoming this, an auxiliary switch 52 controlled by the member 5! is provided for giving the motor momentary energization from the source 29 so as to move the shaft off dead center. A resistance 53 is preferably provided in the auxiliary circuit for insuring slow operation of the motor from this position.

It should be understood that my invention is not limited to specific details or construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Operating mechanism comprising a motor, a rotatable cam driven thereby, means adapted to be actuated from one position to another position by said cam, said cam at the initiation of said operation being in a preferred predetermined position with respect to said actuated means, means for deenergizing said motor upon completion of said cam operation, and centering means for restoring said cam tosaid initial predetermined position upon over-travel thereof.

2. Operating mechanism comprising a motor, a rotatable cam driven thereby, means adapted to be actuated from one position to another position by said cam, said cam being in a predetermined angular position with respect to said actuated means at the initiation of said operation, means for deenergizing said motor upon completion of said cam operation, and means including spring structure for dissipating the kinetic energy in said operating mechanism after said deenergizing operation and for restoring said cam to said initial predetermined position.

3. Operating mechanism comprising a motor, a rotatable cam driven thereby, collapsible thrusttransmitting structure adapted to be actuated through an operating stroke by said cam, tripping means associated with said thrust-transmitting structure, said cam being in a predetermined angular position with respect to said structure at the beginning of said stroke for permitting resetting of said tripping means, means for deenergizing said motor at the end of said stroke, and means for dissipating the kinetic energy stored in said operating mechanism when said motor is deenergized and for restoring said cam to said predetermined angular position prior to a subsequent operating stroke.

4. Operating mechanism comprising a motor, a rotatable cam driven thereby, collapsible thrust-transmitting structure adapted tobe actuated through an operating stroke by said cam, tripping means associated with said thrusttransmitting structure, said cam being in a. .pre-

determined angular position corresponding to' the reset position of said structure at the beginning of said stroke, means for deenergizing said motor at the end of said stroke, and means including a spring adapted to be tensioned in accordance with rotation of said cam beyond said predetermined angular position upon deenergization of said motor for returning said cam to said position.

5. Operating mechanism comprising a motor, a rotatable cam driven thereby, collapsible thrust-transmitting structure adapted to be actuated through an operating stroke by said cam, tripping means associated with said thrusttransmitting structure, said cam being in a predetermined angular position with respect to said structure at the beginning of said stroke, means for deenergizing said motor at the end of said stroke, said tripping means being adapted toreset for holding said structure in thrust-transe mitting position when said cam is in said prede-' termined angular position, and means including a spring tending to center said cam with respect to said position.

6. Operating mechanism comprising a motor, a rotatable cam driven thereby, a thrust-transmitting linkageincluding a roller coacting with said cam, tripping means for holding said linkage in thrust-transmitting position, said tripping means being adapted to reset when said cam is in a predetermined angular position with respect to said roller, rotation of said cam by said motor causing an operating stroke of said linkage, means for deenergizing said motor at the end of said stroke, and means for dissipating the kinetic energy stored in said operating mechanism and centering said cam with respect to said predetermined angular position comprising a spring adapted to be tensioned to an extent corresponding approximately to the over-travel of said cam with respect to said angular position.

'7. Operating mechanism comprising a motor, a rotatable cam driven thereby, means adapted to be actuated through an operating stroke by said cam, said cam at the initiation of said stroke respect to said means, and means including spring structure adapted to be tensioned in ac- I cordance with over-travel of said cam with respect to said angular position upon completion of said operating stroke tending to center said cam with respect to said position, said spring structure being operatively connected to said cam through ratio gearing for insuring centering of said cam at a dead center position between said spring structure and cam.

8. Operating mechanism comprising a motor, a rotatable cam driven thereby, means adapted to be actuated through an operating stroke by said cam, said cam at the initiation of said stroke being in a predetermined angular position with respect to said means, and means for centering said cam with respect to said angular position comprising spring structure, said spring structure being fixed at one end, a crank operatively connected to the other end of said spring structure, a gear connected to said crank and a c0- actingtgear operatively connected to said cam,

the number of teeth of said first-named gear being a multiple of the number of those of said coacting gear for insuring centering of said cam at a dead center position between said spring structure and cam.

9. Operating mechanism comprising a motor, a cam driven thereby, means adapted to be actuated through an operating stroke by said cam, said cam at the initiation of said stroke being in a predetermined angular position with respect to said means, a springv operatively connected to said cam for opposing movement beyond said angular position thereby tending to centersaid cam after. an operating stroke, and an auxiliary

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