Means For Charging A Stored Energy Circuit Breaker Closing Device

Abstract

For charging the closing spring of a heavy-duty electric circuit breaker, manually actuated charging means is provided for effecting the desired charging action in response to a single stroke of an input handle. The charging means comprises a pair of spaced cams interconnected by a flexible power-transmitting member that winds about the periphery of one cam while unwinding from the periphery of the other. The cam peripheries are so shaped that the torque on the handle needed to charge the spring remains generally constant during most of the charging operation. BACKGROUND This invention relates to a stored energy operating device for closing an electric circuit breaker and, more particularly, relates to manually actuated means for charging said stored energy operating device. The utilization of stored energy closing mechanisms in relatively large, heavy-duty electric circuit breakers has become increasingly more common among circuit breaker manufacturers. In order to obtain the high speed and positive closing action essential for successful operation of such breakers, while at the same time satisfying predetermined space limitations, powerful closing springs must be used. The relatively great amount of closing energy which is released by such springs each time the breaker is closed must first be accumulated or stored in the springs by the operation of suitable charging means, and it is with such charging means, particularly charging means of the manually actuated type, that the present invention is concerned. Certain prior manual means for charging the powerful closing springs of heavy-duty circuit breakers have required the operator to apply an undue amount of force to the handle that is used for actuating the charging means. Typically, this required handle force is at objectionably high values only during an intermediate portion of the handle stroke. For reducing the required peak handle force, it is proposed in U.S. Pat. No. 3,095,489-Baird, assigned to the assignee of the present invention, to provide improved manually actuated charging means which utilizes a handle that is repetitively oscillated in order to effect the desired charging action. While such mechanism does limit the peak handle forces to an acceptable value, it is subject to the disadvantage that it is relatively expensive and complicated and is not as easy to operate as a single-stroke charging mechanism. SUMMARY Accordingly, an object of our invention is to provide, for charging the powerful closing spring of the circuit breaker, charging means which effects the desired charging action in response to a single stroke of the input handle and yet does not require excessive handle force at any point during the stroke.

Description

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic showing of a circuit breaker shown in the closed position with its stored-energy operator completely charged and ready to perform a closing operation when the circuit breaker opens.

FIG. 2 shows some of the parts of FIG. 1, i.e., the operating mechanism, when the circuit breaker has been tripped to effect opening. The operating mechanism as illustrated in FIG. 2 has not yet been reset to its force-transmitting condition.

FIG. 2a shows the parts of FIG. 2 after the operating mechanism has been reset to its force-transmitting condition. The circuit breaker is still open.

FIG. 3 shows the circuit breaker in closed position and the stored-energy operator in a fully discharged condition.

FIG. 4 shows the circuit breaker in closed position, the stored-energy operator in a fully discharged condition, and the handle for charging in a cocked position prepared to start a charging operation.

FIG. 4a shows a portion of the circuit breaker in an intermediate position during a charging operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT CIRCUIT BREAKER OPERATING MECHANISM

Referring now to FIG. 1, the circuit breaker shown therein comprises separable contacts 11 and 12 connected in a power circuit 13 in order to open and close the circuit. Contact 12 is a movable contact carried by an insulating operating rod 14 between its closed position of FIG. 1 and its open position of FIGS. 2 and 2a. The movable contact rod 14 is connected to the right hand end of an operating lever 15 which is pivotally mounted on a stationary pivot 16. An opening spring 17 biases operating lever 15 in a counterclockwise direction toward the contact-open position of FIG. 2.

For actuating operating lever 15 in a clockwise closing direction from its open position of FIG. 2, a conventional mechanically trip-free operating linkage 20 is provided. Linkage 20 comprises a pair of toggle links 21 and 22 pivotally joined together by a knee 23. One toggle link 21 is pivotally connected to the left hand end of operating lever 15 by a pivot 25, whereas the other toggle link 22 is connected to the upper end of a guide link 26 by a pivot pin 27. Guide link 26 is pivotally supported at its lower end by a fixed fulcrum 28. Pivot pin 27 carries a latch roller 30 which cooperates with a suitable trip latch 31.

So long as trip latch 31 remains in the latched position of FIGS. 1 and 2a, toggle 21, 22 is capable of transmitting thrust to movable switch operating lever 15. Thus, when knee 23 of the toggle is driven to the left from its position of FIG. 2a into its position of FIG. 1, toggle 21, 22 is extended, thereby driving movable switch contact 12 downwardly toward its closed position. For so driving toggle knee 23 to the left through its closing stroke, we provide a rotatable cam 35, which operates on a roller 36 mounted on knee 23. When cam 35 is driven clockwise from its position of FIG. 2a into its position of FIG. 1, it drives roller 36 and toggle knee 23 to the left.

When toggle knee 23 reaches its fully closed position of FIG. 1, a suitable prop 38 is forced by a prop-biasing spring 39 into a position behind roller 36, thereby holding toggle 21, 22 in its extended position. This permits cam 35 to be further rotated without allowing toggle 21, 22 to collapse at its knee 23. The prop is shown mounted for free rotation on the same shaft 40 as the cam 35 is mounted upon. Cam 35 is, however, keyed to cam shaft 40.

Trip latch 31 is pivotally mounted on a fixed pivot 42 that is biased by a spring 43 into its latching position of FIGS. 1 and 2a. Tripping of latch 31 is effected by a solenoid 45, energization of which drives latch 31 counterclockwise, freeing the toggle support pin 27 from restraint by the latch.

Should latch 31 be tripped when the breaker is in its closed position of FIG. 1, or even during a closing operation, toggle 21, 22 will be rendered inoperative to transmit thrust to movable contact operating lever 15. As a result, the opening spring 17 impels movable contact 12 upwardly into its open position of FIG. 2, collapsing toggle 21, 22 into its position of FIG. 2. As long as latch 31 is held tripped, toggle 21, 22 will remain unable to transmit closing thrust to movable contact operating lever 15. Resetting of latch 31 is effected by spring 43 when guide link 26 is reset from its position of FIG. 2 to its position of FIG. 2a by a reset spring 46.

STORED-ENERGY CLOSING DEVICE

In order to rotate closing cam 35 so as to effect circuit breaker closing, a stored-energy closing device 50 is provided. As seen in FIG. 1, this device comprises a heavy tension spring 51 suitably supported at its upper end by a bracket 52 pivotally mounted on a stationary pivot pin 53. The lower end of spring 51 is attached to a spring retaining member 54 which is pivotally mounted on a crank pin 55. Crank pin 55 is carried by a crank 56, which is keyed to the same shaft 40 as cam 35.

In FIG. 1, closing spring 51 is shown in its fully tensioned or charged state. Upon release of spring 51 (in a manner soon to be described), the spring force rapidly drives the spring retaining member 54 upwardly in an arcuate path, thereby rotating crank 56 and shaft 40 at high speed in a clockwise closing direction. This drives cam 35 in a clockwise closing direction, and if the toggle is in its open position of FIG. 2a, extends the toggle to effect circuit breaker closing.

Closing spring 51 is releasably held in its position of FIG. 1 by a closing latch 58 cooperating with a roller 59 on a disk 60 fixed to cam shaft 40. In its position of FIG. 1, latch 58 blocks disk 60 and shaft 40 from rotating clockwise. But when latch 58 is released, disk 60 and shaft 40 are free to rotate in a clockwise direction under the influence of closing spring 51. Latch 58 can be released by a suitable closing-control solenoid 62, which when energized pivots latch 58 clockwise about a stationary pivot 63 to effect latch release.

It is to be understood that disk 60 and main shaft 40 can be rotated only in a clockwise direction. Counterclockwise motion of these parts is blocked by a suitable holding pawl 65 cooperating with ratchet teeth 66 on the periphery of disk 60.

CHARGING MECHANISM FOR STORED-ENERGY CLOSING DEVICE

In order to charge the closing spring 51, a manually actuated charging mechanism 70 is provided. This charging mechanism 70 comprises a driven cam 71 and a driving cam 72 connected together by a flexible power-transmitting member in the form of a chain 73. The opposite ends of chain 73 are respectively connected to cams 71 and 72 by pivot pins 74 and 75.

Driving cam 72 is mounted for free rotation on stationary pivot 76 laterally spaced from the cam shaft 40 on which cam 71 is mounted. Driven cam 71 is rotatable about the axis of cam shaft 40 and is coupled to the cam shaft by means of a one-way driving connection comprising a pawl 77 and two angularly spaced ratchet teeth 78 and 79 on the cam shaft 40. Driven cam 71 is freely rotatable in a counterclockwise direction with respect to cam shaft 40 but when rotated in a clockwise direction, it drives shaft 40 through pawl 77 and one of the ratchet teeth 78 or 79.

The driving cam 72 is adapted to be actuated by a handle 80 mounted for pivotal motion about the axis of a shaft 81. Keyed to shaft 81 is a crank 82 which has a crank pin 83 connected to the upper end of a connecting link 84, the lower end of which is pivotally connected at 86 to driving cam 72.

SETTING THE CHARGING MECHANISM FOR A CHARGING OPERATION

FIG. 1 shows the handle 80 in its normal position, and FIG. 4 shows it in its cocked position. When handle 80 is pivoted in a counterclockwise direction from its normal position of FIG. 1 into its cocked position of FIG. 4, the charging mechanism 70 is prepared for a charging operation. More specifically, this counterclockwise handle motion drives connecting link 84 downwardly into its position of FIG. 4, thereby rotating cam 72 clockwise into its position of FIG. 4.

In response to this clockwise motion of driving cam 72, a reset spring 87 coupled to driven cam 71 through a pin 88 drives driven cam 71 counterclockwise through 180.degree. of travel from its position of FIG. 1 into its position of FIG. 4. Cam 71 is able to freely rotate in a counterclockwise direction with respect to cam shaft 40, and it therefore carries the pawl 77 from its position of FIG. 1 behind ratchet tooth 78 to its position of FIG. 4 behind ratchet tooth 79. Such counterclockwise motion of cam 71 winds chain 73 about the periphery of cam 71 as it unwinds from the periphery of cam 72, thus setting the chain in its position of FIG. 4 in preparation for a charging operation.

It is noted that the reset spring 87 for cam 71 is shown wound about the periphery of a member 89 that is mounted on shaft 40 and is freely rotatable relative to shaft 40.

A CHARGING OPERATION FOLLOWING SETTING OF THE CHARGING MECHANISM

Charging of the closing spring is effected by pivoting handle 80 clockwise from its cocked position of FIG. 4, through its intermediate position of FIG. 4a, into its normal position of FIG. 1. Such handle motion drives operating rod 84 upwardly, rotating driving cam 72 counterclockwise from its position of FIG. 4, through the position of FIG. 4a, into its position of FIG. 1. This applies a tensile force to chain 73, thereby driving the driven cam 71 in a clockwise direction from its position of FIG. 4, through FIG. 4a, into its position of FIG. 1. As the cams 72, 71 rotate in this manner from FIG. 4 to FIG. 1, chain 73 winds about the periphery of driving cam 72 while unwinding from the periphery of driven cam 71. The periphery of cams 72 and 71 are so shaped that the mechanical advantage of the drive 72, 73, 71 changes during movement from FIG. 4 to FIG. 1 in a manner that varies directly with the torque needed on shaft 40 in order to charge the closing spring 51, thus enabling charging to be effected with a substantially constant torque on the driving handle 80.

Initially the torque required on shaft 40 for spring charging is relatively low because (a) tension spring 51 has a low charge level and (b) the spring mechanism 51, 54, 56 is close to a dead center position, as will be apparent from FIG. 4, where it can be seen that the effective lever arm 90 (as measured between the dead center line 91 of the spring mechanism and the axis of crank pin 55) is very small. The torque requirements increase steeply as the crank 56 of the spring mechanism is rotated in a clockwise direction inasmuch as both the lever arm 90 and the charge level of the spring 51 are simultaneously increasing. At an intermediate point in the charging operation, the effective lever arm 90 passes through a maximum value and begins decreasing, and this begins reducing the torque required on shaft 40 for charging. The effective lever arm 90 continues decreasing as the spring mechanism approaches its lower dead center position near the position shown in FIG. 1, and this further reduces the torque required for spring charging. Although the spring tension is increasing during this later movement, the effective lever arm 91 is decreasing more rapidly, and the net result is reduced torque requirements.

The mechanical advantage of the drive mechanism 72, 73, 71 at any given instant is a direct function of (R2)/(R1), where R.sub.2 is the effective radius of driven cam 71 and R1 is the effective radius of driving cam 72. Each of these radii is measured from the axis of the cam to the axis of the straight line portion of chain 73 via a path extending normal to the chain axis. At the start of the charging operation (when the parts are in the position of FIG. 4), R2 is relatively small and R1 is relatively large, thus providing a relatively small mechanical advantage. At the intermediate point depicted in FIG. 4A, R2 has increased to a relatively high value and R1 has decreased to a relatively small value, thus providing a relatively high mechanical advantage at this point. As the cams move from FIG. 4a toward their fully charged position of FIG. 1, R2 decreases and R1 increases thus lowering the mechanical advantage.

It will thus be apparent that the mechanical advantage of the drive 72, 73, 71 is at a relatively low value at the start of the charging operation, increases to a relatively high value at an intermediate point in the charging operation, and then decreases to lower values during the final portion of the charging operation, thus matching, or varying directly, with the torque needed on cam shaft 40 to effect charging of the closing spring 51.

To accentuate the increase in mechanical advantage that occurs during the intermediate portion of the charging operation, the operating rod 84 is arranged to act on cam 72 through an effective lever arm L that increases from a low value to a relatively high value at an intermediate point in the charging operation and then decreases during the final part of the charging operation. This effective lever arm is measured from the axis of pivot 76 to the line of action of operating rod 84 normal to this line of action.

The varying mechanical advantages that are present in the drive 72, 73, 71 and in the rod 84-cam 72 connection, as described hereinabove, and the fact that they vary directly with the torque required on shaft 40 to charge spring 51 enable a workman to charge spring 51 with an approximately constant torque applied to handle 80.

For assuring that the chain 73 will be prevented from slipping laterally off the periphery of cams 71 and 72, cam 72 is provided with spaced teeth 92 that fit into the usual open spaces in the chain 73 between the pins, 93 that connect the chain links together.

After the charging operation has carried the spring mechanism through its lower dead center position, spring 51 is allowed to discharge very slightly, driving cam shaft 40 a small distance clockwise until pin 59 on disk 60 engages closing latch 58. The parts are then in a position of FIG. 1.

CLOSING OF THE CIRCUIT BREAKER AFTER SPRING CHARGING

Closing of the circuit breaker can then be effected by tripping closing latch 58, thus freeing disk 60 for clockwise motion. This allows closing spring 51 to discharge at high speed, thereby driving cam shaft 40 and cam 35 clockwise from their position of FIG. 1 into their closed position of FIG. 3. In so moving, cam 35 extends toggle 21, 22 from its position of FIG. 2a to that of FIG. 3, as previously described, thereby driving the circuit breaker contacts 12, 11 into engagement.

During this closing action, cam shaft 40 rotates in a clockwise direction free of spring charging cam 71. This independent movement is permitted by the pawl and ratchet connection 77, 78.

While we have shown and described a particular embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.

Claims

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

1. In a stored-energy operating device for closing an electric circuit breaker, a closing spring dischargeable to supply closing force for the circuit breaker, and means for charging said spring comprising:

a. first and second cams mounted for angular motion about laterally spaced axes of rotation,

b. unidirectional force-transmitting means for coupling said first cam to said closing spring to effect charging of said spring when said first cam is driven in one angular direction,

c. a handle coupled to said second cam and having a normal position and a cocked position,

d. a flexible power-transmitting member attached at its respective opposite ends to said cams and wound about the periphery of said second cam when said handle is in its normal position,

e. reset biasing means for driving said first cam in a direction to cause said flexible member to wind about the periphery of said first cam in response to movement of said handle from its normal to its cocked position,

f. motion of said handle from its normal to its cocked position moving said second cam in a first direction to allow said flexible member to unwind therefrom,

g. return movement of said handle toward its normal position driving said second cam in a direction opposite to said first direction and transmitting motion through said flexible member to said first cam to drive said first cam in a direction to charge said closing spring,

h. said flexible member winding about the periphery of said second cam and unwinding from the periphery of said first cam during said return movement of said handle,

i. the peripheries of said cams being so shaped that the mechanical advantage of the cam-flexible member drive varies during a charging operation and is near its highest value when the torque needed at said force-transmitting means for charging said spring is highest.

2. The combination of claim 1 in which: the peripheries of said cams are so shaped that the mechanical advantage of said cam-flexible member drive varies directly with the torque needed at said force-transmitting means for charging said spring.

3. The combination of claim 1 in which: the peripheries of said cams are so shaped that the torque on said handle needed to charge said spring remains generally constant during most of the charging operation including that portion of the charging operation requiring maximum torque at said force-transmitting means.

4. The combination of claim 1 in which:

a. said force-transmitting means for coupling said first cam to said closing spring comprises a spring controller that is mounted for overcenter action with respect to said spring,

b. said spring controller occupies a first dead center position with respect to said spring when said spring is discharged,

c. means is provided for transmitting charging force to said spring in response to rotation of said spring controller from said first dead center position toward a second dead center position with respect to said spring,

d. said spring tends to discharge and thereby to further rotate its spring controller in response to rotative movement of said spring controller into a predetermined position past said second dead center position,

e. said spring controller has its longest effective lever arm during a charging operation when passing through a predetermined intermediate position between said first and second dead center position, and

f. said cams are so shaped that the mechanical advantage of the cam-flexible member drive is near its highest value when said spring controller has its longest effective lever arm.

5. The combination of claim 1 in which: said unidirectional force-transmitting means permits said reset biasing means of (e) claim 1 to effect said driving of said first cam in a direction to wind said flexible member about said first cam without transmitting effective force to said closing spring.

6. The combination of claim 1 in which:

a. said handle is coupled to said second cam by means of a linkage that includes a rod pivotally connected to said second cam,

b. the effective lever arm between the line of action of said rod and the axis of rotation of said second cam varies in length during a charging operation to provide a mechanical advantage for the rod-second cam connection which varies directly with the effective length of said lever arm, said effective length being near its maximum value when the torque needed at said force-transmitting means for charging said spring is highest.

7. The combination of claim 1 in which said first cam has an effective radius with respect to said flexible member that varies during said charging operation, said effective radius being greatest at an intermediate point in the charging operation.

8. The combination of claim 7 in which said second cam has an effective radius with respect to said flexible member that varies during said charging operation, the effective radius of said second cam being near its lowest value at said intermediate point in said charging operation.