US3187593A - Operating mechanism for circuit breakers - Google Patents

Description

1965 J. R. M CLOUD OPERATING MECHANISM FOR CIRCUIT BREAKERS 2 Sheets-Sheet 1 Original Filed Oct. 15, 1958 June 8, 1965 J, R. M CLOUD OPERATING MECHANISM FOR CIRCUIT BREAKERS 2 Sheets-Sheet 2 Original Filed Oct. 15, 1958 United States Patent 3,187,593 OPERATING MECHANISM FOR CIRCUIT BREAKERS James R. McCloud, Los Angeies, Calih, assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa, a corporation of Pennsylvania Original application Oct. 15, 1953, Ser. No. 767,383, now Patent No. 3,106,137, dated Oct. 8, 1%3. Divided and this application July 14, 1961, Ser. No. 124,091 1 Claim. (Cl. 74-106) The instant invention relates to circuit breaker operating mechanisms and more particularly to an operating mechanism wherein a direct mechanical connection is provided between the knee of the closing toggle and the closing ram of the actuating mechanism.

The present application is a divisional application of my copending application, Serial Number 767,383, filed October 15, 1958, now Patent No. 3,106,137 entitled Opcrating Mechanism for Circuit Breakers (PC-14) and assigned to assignee of the present invention.

High speed circuit breakers are usually constructed with a toggle type operating mechanism for multiplying and transmitting the closing force of the actuating mechanism to the movable contacts. free operation a latchable link is provided at one end of the toggle. The circuit breaker may be closed only when the trip link is latched in a reset position, by applying the closing force to the knee of the toggle.

During high .speed reclosing of a circuit breaker the toggle mechanism usually is not fully collapsed before the closing'cycle begins. That is, the toggle is collapsing in one direction while the ram of the actuating mechanism is moving in the opposite direction. Thus, the ram and the knee pin of the toggle engage with a tremendous shock.

In prior art devices the knee of the toggle and the operating end of the closing ram are not physically connected except when the ram actually engages the knee pin during the closing operation. The device of the instant invention includes a tie link which mechanically interconnects the knee pin and the operating end of the closing ram.

This arrangement assures that, at no time, will the knee pin and closing ram be moving in opposite directions so that the toggle will not be collapsing toward a collision with the ram moving in a closing direction. Thus, the tie link provides a novel means of obtaining a smooth reversal of movement of the toggle mechanism during a reclosing operation immediately following the initiation of an opening operation.

In order to achieve trip Since the operating mechanism is mechanically tiedto the actuating mechanism, the retrieving spring of the actuating mechanism will aid in bringing about a rapid resetting of a latchable link so that the fast reclosing may be achieved. Means are provided between the resettable link and the controls for the actuating mechanism whereby a reclosing movement, while it may occur before the completion of an opening operation, cannot occur before the resettable link is latched to support the toggle in a movemnt toward its extended position.

In circiut breakers having a low voltage and high current rating, the forces necessary to close the breaker under no load or light load conditions are relatively small. However, closing the circuit breaker under high momentary currents requires considerable force. Thus, the closing force supplied by the actuating mechanism during no load closing is considerably higher than required thereby subjecting the operating mechanism to a severe shock as the circuit breaker reaches its closed position.

The device of the instant invention overcomes this 3,187,593 Patented June 8, 1965 undesirable eiiect by providing an air cushion, when the contacts come into engagement, to absorb all excess closing forces. This is accomplished by providing the cylinder of the actuating mechanism with a series of ports near the end thereof toward which the ram piston moves during the closing stroke. Thus, the piston may move rapidly toward the ports. Once past the ports, the piston traps air in front of it in the cylinder with this trapped air acting as a cushion. The parts are positioned so that the retarding of piston motion does not take place until after the circuit breaker contacts have made their initial engagement. A check valve is provided to rapidly admit air, to the portion of the cylinder in which the cushion was formed, when the piston is moving in a direction opposite to the closing stroke direction.

Accordingly, a primary object of the instant invention is to provide a novel circuit breaker coordinated operating and actuating mechanism which is especially fast opening and which is resettable in a minimum of time to permit rapid reclosing.

Another object is to provide a direct mechanical connection between the knee of the operating mechanism toggle and the closing ram of the actuating mechanism.

Still another object is to provide cushioning means which is effective at the end of the closing stroke of the ram to absorb shocks which would otherwise be resent when closing a circuit breaker under no load conditions.

A further object is to coordinate the operation of the actuating mechanism to the position of the operating mechanism in a manner such that a reclosing operation may not be initiated until the latchable link of the operating mechanism is positioned to support the toggle as it is being extended.

A still further object is to provide novel means for journaling the movemnt of the closing ram so that the longitudinal movement thereof will not cause it to bind in its bearings by exerting a lateral thrust thereon.

These objects as well as other objects of the instant invention shall readily become apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a front elevation with the portions of the housing broken away of a coordinated actuating and operating mechanism constructed in accordance with the instant invention, with the mechanism shown in the closed position.

FIGURE 2 is a side elevation of the mechanism of FIGURE 1 with portions of the housing broken away.

FIGURES 3-5 are side elevations illustrating the mechanism of FEGURE 1 in its various positions. In FIGURE 3 the mechanism is in the closed position, in FIGURE 4 it is tripped open with the closing ram positioned at the top of its closing stroke, and in FIGURE 5 the mechanism is in the reset position.

Now referring to the figures, circuit breaker operating mechanism 10 is adapted to be connected through reciprocative rod 11 thereof to the movable contact of a circuit breaker (not shown) whose opening springs bias rod 11 in the direction of arrow A. Rod 11 is pivotally secured at 12 to arm 13 of crank 14 mounted to fixed pivot 20. The other arm 15 of crank 14 is pivotally securedat 16 to one end of the operating toggle comprising links 17, 10 joined at knee 19. The other end or" toggle 1'7, 18 is connected at pivot 21 to one end of latchable link 22 while the other of link 22 is mounted to a fixed pivot 23.

Latchable link 22 is maintained in the latched position of FIGURE 1 by trip finger 2 of tripping mechanism 25. Trip finger 24- is mounted to fixed pivot 25 and biased thereabout in a clockwise direction with respect to FIG- URE 1 by means of torsion spring 27 also mounted to pivot 26 and bearing against housing formation 29 and leg 28 of trip finger 24. An adjustable stop comprising screw 30, extending through housing formation 29 and locked by nut 31, establishes the latching position for trip finger 24. Leg 32 of latch finger 24 remains in engagement with roller 33, mounted to pivot 21 at one end of latchable link 22, for all positions of link 22.

Trip link 35, pivoted at fixed pivot 36, engages roller 37 pivotally mounted at to leg 28. Since the point at which trip link 35 engages roller 37 falls on the line between the centers of pivots 36, 38 latchable link 22 is maintained in latching position by trip link 35. Torsion spring 39, disposed about pivot 36, bears against housing formation 40 and trip link 35 to bias link 35 clockwise with respect to FIGURE 1, about pivot 36 to the latching position established by adjustable stop 42 threaded into housing formation 40, with lock nut 41 maintaining the position of stop 42.

Trip crank 43 is pivotally mounted to fixed pivot 44 and is biased counterclockwise thereabout, with respect to FIGURE 1, by means of tension spring 45 which is secured at one end to housing formation 47 and at the other end to one leg 46 of crank 43. Leg 46 is normally engaged with adjustable stop 49 which is threaded into housing formation 47 and maintained in position by lock nut 48.

The other leg 50 of crank 43 engages trip link 35 for clockwise rotation thereof when trip coil 51 is energized. Energization of coil 51 causes a fiux to be generated by magnet 52 which attracts leg 46 causing trip crank 43 to rotate clockwise with leg 50 engaging trip link 35 to rotate it counterclockwise thereby disengaging roller 37 carried by trip finger 24. Thus, finger 24 may now be moved counterclockwise under the influence of the circuit breaker opening spring. Stop 49 establishes the air-gap between crank leg 46 and magnet 52.

Latchable link 22 is a two element member having member 55 rigidly secured to both elements and disposed concentrically about fixed pivot 55. Protrusion 56, extending from member 55, engages latch checking switch plunger 57 of reset means 58 when latchable link 22 is latched as in FIGURES 3 and 5. 7

Reset means 58 is part of the control circuit for the valve means 101 actuating mechanism 100, as hereinafter explained.

Connecting link 60 is pivotally secured to knee 19 of toggle 1'7, 18 and is also pivotally secured at 103 to the upper end of reciprocative operating ram 102 of actuating mechanism 100. Thus, operating mechanism 10 is mechanically connected in a positive manner to actuating mechanism without any lost motion connections.

Links 61 and 62 cooperate to form means for guiding the vertical movement of ram 102. Link 61 is mounted to fixed pivot 63 and is pivotally mounted to link 62 at a point 64 intermediate the ends thereof. One end of link 62 is pivotally secured to ram 102 at the point 103 where connecting link 60 is secured to ram 102. The other end of link 62 carries a pivoted roller 65 which is disposed within guide 66 which journals roller 65 for horizontal movement.

Prop latch 67 is pivotally mounted to fixed pivot 60 and is urged clockwise thereabout by tension spring 69 into engagement with stop 70. Spring 69 is secured to housing formation 71 and to prop latch 67. When prop latch 67 resets against stop 70, latch 67 is positioned to engage knee 19 and prevent collapse of toggle 17, 18 while latchable link 22 remains latched even though no force is urging ram 102 upwardly.

Operating ram 102 extends from the top side of piston 104 while guide rod 105 extends from the bottom side of piston 104 and is in axial alignment with ram 102. Rod 105 extends through bottom opening 106 in operating cylinder 107 with ring member 108 providing a seal between cylinder 107 and rod 105. Retrieving compres- 4 sion spring 110 bears against the outer bottom surface 109 of cylinder 107 and the enlarged head 111 of rod 105 thereby biasing piston 104 toward the bottom of cylinder 107 (FIGURE 5).

Studs 112 extend through clearance holes in cylinder flange 113 and are received by threaded formations on the bottom of the operating mechanism housing 99. Rings 114, 115 provide a seal between piston 104 and the inner wall of cylinder 107. Valve means 101 selectively controls the entrance of compressed air to cylinder 107 through opening 116 located near the bottom of cylinder 107.

With toggle 17, 10 collapsed and latchable link 22 latched in the reset position of FIGURE 5, toggle 17, 18 is extended by introducing compressed air to the bottom side of piston 104. This forces ram 102 upward against the forces of spring 110 and the opening spring of the circuit breaker (not shown) driving knee 19 upward. Since link 22 is latched, the right end 21 of toggle 17, 18 is stationary and the left end 16 thereof moves to the left rotating crank 14 counterclockwise carrying rod 11 downward and toggle 17, 18 is now in the extended position of FIGURE 3. Knee 19 in moving to the position of FIGURE 3 engages prop latch 67 forcing it counterclockwise about pivot 68. When knee 19 clears the top end of prop latch 67, spring 69 urges latch 67 clockwise against stop 70 to latching position.

If at any time during the upward movement of ram 102, trip coil 51 is energized thereby releasing trip finger 24, the force of the circuit breaker opening spring urging rod 11 upward will force latchable link 22 clockwise about pivot 23 to the tripped position of FIGURE 4. Knee 19 will pivot clockwise about pivot 103 and the toggle will not be extended as in the tripped position of FIGURE 4 even when ram 102 reaches its topmost position.

Operating mechanism 10 is trip free so that a downward movement of ram 102 is not necessary to permit rapid unlatching of link 22 and rapid movement of toggle 17, 18 to enable rod 11 to move to its up position (FIG- URES 4 and 5). However, ram 102 must downward a partial distance to permit toggle 17, 18 to collapse sufficiently to reset latchable link 22 and prepare the operating mechanism for reclosing. Thus, connecting link 60 provides a mechanical trip free arrangement not limited by the prior art so-called pneumatic trip free arrangement.

When operating mechanism 10 is tripped so that trip link 35 is moved counterclockwise, toggle 17, 18, because it is biased slightly in the upward direction pulls knee 19 off of prop latch 67 so that toggle 17, 18 may collapse entirely, or only partially by moving to the right as when ram 102 is maintained in its up position of FIGURE 4.

On a subsequent starting down of ram 102, toggle 17, 13 is collapsed with knee 19 moving downward. The collapsing toggle 17, 10 carries link 22 counterclockwise about pivot 23 permitting trip finger 24 to return to latching position urged by spring 27. It is to be noted that trip finger 24 is always in engagement with roller 33 so that spring 27 assists in fast relatching of link 22. The constant engagement between trip finger 24 and roller 33 prevents shock which would otherwise occur if these two elements were not always engaged.

As soon as link 22 reaches the latch or reset position of FIGURE 5 protrusion 56 carried thereby engages push rod 57 of control means or switch 58. Switch 58 is in a circuit which controls the operation of valve means 101 in a manner which enables valve means 101 to be operated for admitting compressed air to cylinder 107 whenever link 22 is reset.

Thus, toggle 17, 18 may be extended for reclosing of the circuit breaker even though the circuit breaker, the operating mechanism 10, and the actuating mechanism 100 have not reached their fully open positions. It is only necessary to have latchable link 22 in the reset position in order to initiate the closing stroke of operating ram 102.

When valve 101 is operated to admit compressed air to the underside of piston 104, piston 104 rapidly moves upward forcing air ahead of it out of the upper portion of cylinder 107 through ports 120. When upper piston ring 114 passes ports 120, ports 120 are closed ofi and owing to the pressure on one way flapper valve 121, air is now trapped above piston 104 in the area 122 to provide a cushion. In order not to impede the downward movement of piston 104, flapper valve 121 opens permitting a free flow of air through opening 124 into the top area of cylinder 107 upon the downward movement of piston 104.

Ports 120 are positioned so that they are sealed off by ring 114 during the closing stroke of ram 102 when the circuit breaker contacts initially engage. Thus, ram 102 moves rapidly in bringing the contacts into initial engagement. Thereafter, the cushion formed by the trapped air in cylinder area 122 brakes ram 102 so that the circuit breaker will not be subjected to extreme shocks especially when being closed under light loads.

Thus, I have provided a novel construction for coordinated circuit breaker operating and actuating mechanisms wherein a positive mechanical connection is included between the two mechanisms. Means are also included to absorb closing shocks at the end of the closing stroke. The construction is such that tripping and reclosing may be done more rapidly and is accomplished with decreased shock.

Although I have here described preferred embodiment of my novel invention, many variations and modifications 6 will now be apparent to those skilled in the art, and I therefore prefer to be limited, not by the specific disclosure herein, but only by the appending claim.

I claim:

The combination comprising an operating mechanism and an actuating mechanism operatively connected therewith; said actuating mechanism including a reciprocative operating ram; said operating mechanism including a toggle having a knee; means mechanically connecting said ram to said knee in all positions of said toggle; a first link and a second link for guiding said ram in a path defined by the longitudinal axis thereof; said first link being secured at one end to a stationary pivot and at the other end being pivotally secured to said second link at a 5 point intermediate the ends thereof; said second link being pivotaliy secured at one end to said ram; a guideway in a plane normal to said longitudinal axis; said second link having the other end thereof slidably disposed within said guideway.

References Cited by the Examiner UNITED STATES PATENTS 1,841,712 1/32 Cason 74-103 X 2,534,933 12/50 Van Sickle 74106 X 2,656,430 10/53 Van Sickle 2001520 X 2,684,510 7/54 Muller 74-520 X 2,760,025 8/56 Van Sickle ZOO-82.1 X

BROUGHTON G. DURHAM, Primary Examiner. MILTON KAUFMAN, Examiner.

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