US2905787A - Operating mechanism for an electric switch - Google Patents

Description

L. HEINTZ 2,905,787

OPERATING MECHANISM FOR AN ELECTRIC SWITCH Filed Dec. 26, 1957 Sept. 22, 1959 2 Sheets-Sheet 1 Inventor? Milton 1.. HeinGz,

bg /W zHis ttorneg.

Sept. 22, 1959 M. L. HEINTZ 2,905,787

QPERATING MECHANISM FOR AN ELECTRIC SWITCH Filed Dec. 26, 1957 2 Sheets-Sheet 2 Inverwtor:

Milton L. Heintz, bJ W E35 Attor'n e5 United States Patent OPERATING MECHANISM FOR AN ELECTRIC swrrcn Milton L. Heintz, Broomall, Pa., assignor to General Electric Company, a corporation of New York Application December 26, 1957, Serial No. 705,331

8 Claims. (Cl. 200-92) This invention relates to an operating mechanism for an electric switch and, more particularly, to an operating mechanism which is capable of closing the switch smoothly and effectively against large inrush current, such as, for example, those currents encountered when switching into a momentarily short circuited electrical system.

When the contacts of a switch are driven toward closed positions, any inrush currents which are encountered abruptly establish electromagnetic forces which tend to oppose the final portion of the switch-closing stroke. For high values of inrush current, these retarding forces tend to stall, or even momentarily reverse, the closing motion of the switch, and, as a result, tend to cause unduly prolonged arcing which could seriously damage the switch.

Accordingly, it is an object of my invention to provide a switch operatingmechanism which is capable, ofeffectively overcoming the high retarding forces which might be established near the end of a contact-closing stroke.

My invention is especially applicable to a switch which utilizes energy derived from an overcenter spring for producing closing action, such as, for example, a switch of the type disclosed. and claimed in application S.N. 701,590, Frank, filed December 9, 1957, and assigned to the assignee of the present invention. In this type of switch, a relatively slow-acting motor is arranged to drive the overcenter spring into an overcenter position, whereupon the overcenter spring quickly discharges, producing high-speed closing of the contacts. Since the motor is slow-acting in comparison to the action of the spring, it has been diflicult to utilize the motor output to aid the spring in overcoming any high retarding forces which might be established near the end of the closingstroke. Assuming that the spring is not capable of successfully overcoming these forces, unduly prolonged arcing tends to take place before the slow-acting motor can act to supplement the spring closing forces.

Accordingly, another object of my invention is to supplement the closing forces of a high-speed overcenter closing spring with additional closing forces derived from a relatively slow-acting motor which had been relied upon to drive the spring over-center.

Another object is to provide such force-supplementing action by means which does not interfere with a subsequent switch-opening operation.

In carrying out my invention in one form, I provide a switch which comprises a follower that is movable from a fully-open position to a fully-closed position as the switch is operated through its full closing stroke. For driving the follower from its fully-open positiontoward its fully-closed position, a main cam and an auxiliary cam are provided. Thes two cams are coupled together by spring means which is arranged to becharged by separating motion of the main cam relative to the auxiliary cam. While being driven through an intermediate portion of the closing stroke by the main cam, the follower acts to restrain the auxiliary cam from 2,905,787 Patented Sept. 22, 1959 following the main cam. This results in separation of the cams and charging of the spring. After some addi tional closing action, the follower moves into a position which allows the spring to discharge and drive the auxiliary cam toward a blocking position behind the follower. As the auxiliary cam moves toward its blocking poistion, energy released from the spring is imparted to the follower through a driving cam surface formed on the auxiliary cam. This cam surface is shaped to provide a wedging action which aids in forcing the switch closed.

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

Fig. 1 is a schematic view, partially exploded, showing a switch embodying my invention, the switch being in the open position.

Fig. 2 is a view similar to that of Fig. 1 but with the switch in the closed position.

Fig. 3 illustrates a portion of the switch operating mechanism at a particular instant during a switch-closing operation.

Fig. 4 is a right side elevational view of the components of Fig. 3. These components are depicted in the position that they occupy when the switch is in its open position of Fig. 1.

Referring now to Figs. 1 and 2, the switch shown therein is of the general type described and claimed in the above-noted Frank application. It comprises a pair of spaced terminals 13 connected to a set of spaced-apart stationary. contacts 14. When the switch is in its closed position of Fig. 2, the stationary contacts 14 are electrically interconnected by a conductive bridging member 15 carrying movable contacts 16 at its opposite ends. When the switch is in its open position, as shown in Fig. 1, this bridging member and the contacts 16 are vertically-spaced from the stationary contacts 13. Closing is effected by driving the bridging member 15 vertically upwardly into aposition wherein the movable contacts 16 are in circuit-closing engagement with the stationary contacts 14.

For driving the bridgingmember 15 upwardly to close the switch or downwardly to open the switch, averticallymovable operating rod 20 of insulating material is provided. This operating rod 20 is rigidly secured at its lower end to the bridging member 15 and is pivotally connected at its upper end to an arm 21, which is pivotally mountedon a pin 21a slidably. carried in a slot 21b formed in a stationary bracket 210. A suitable leaf spring 22 biases the pin 21:: toward the right hand end of the slot 21b. The operating rod 20 is guided for substantially straight-line vertical motion by a suitable guide member 23.having an. appropriate guide opening therethrough.

For imparting motion to the operating rod 21, a contact-actuating lever 30 is provided. This lever 30 is pivotally joined at one of its ends to the arm 21 by a pin 31 located intermediate the ends of the arm 21. At its other end, the lever 30 is mounted for angular movement upon a rock shaft 32 and is so mounted that it is free to move angularly relative to the rock shaft 32. The rock shaft 32, it is to be understood, is journaled in suitable stationarily-located bearings (which are not shown). Preferably, the lever 30 is of a U-shaped configuration, with its bight portion 30a located at the right-hand end of the lever, as shown in Figs. 1 and 2.

For operating the lever 30 clockwise from its position of Fig. 1 in order to produce upward closing motion of the contacts 16, a toggle mechanism 35 is provided. This toggle mechanism includes a toggle link 36 keyed, or otherwise secured, to the rock shaft 32 and a pivoted expansible link 37 comprising a heavy compression spring 38 tending to lengthen the link 37. The link 37 further comprises a threaded rod 39 pivotally joined to the toggle link 36 by means of a pin 40 forming a knee for the toggle. The compression spring 38 surrounds the rod 39 and bears at its upper end against a plate 41 which, in turn, bears agains a stop nut 42 threaded and fixed on the rod 39. The lower end of the compression spring 38 is supported on a pivot block 43 having trunnions 44 laterally-projecting therefrom to pivotally support the block 43. These trunnions 4-4 are journaled in suitable stationary supporting plates such as 45 disposed at laterally-spaced locations. For suitably guiding the rod 39, a centrally disposed guide passage 46 is provided in the pivot block 43 to slidably receive the rod 39'.

As shown in Figs. 1 and 2, the toggle link 36 has a recessed portion at its right hand side for receiving the bight portion 30a of the U-shaped lever 30. At opposite edges of this recessed portion are a pair of abutments 50a and 50b for transmitting switch-operating forces to the lever 30, as will soon be described. When the switch is in the open position of Fig. 1, the upper abutment 50a is spaced a considerable distance from the bight portion 30a, and when the switch is in the closed position of Fig. 2, the lower abutment 50b is spaced a considerable distance from the bight portion 30a.

When the rock shaft 32 together with the toggle link 36 are driven clockwise from the position of Fig. l, the spring 38 is compressed until the toggle passes through an in-line, or center, position. When this occurs (i.e., when the toggle knee 40 moves across a reference line interconnecting the axis of pins 44 and rock shaft 32), the spring 38 rapidly discharges and drives the toggle link 36 further in a clockwise direction. The recessed portion of toggle link 36 is preferably so proportioned that the upper abutment 50a does not contact the bight portion 30a of the lever 30 until the toggle link is well past its center position. As a result, when the spring 38 begins discharging immediately after the toggle is driven overcenter, it accelerates the toggle link 36 at a relatively high rate without initially being impeded by the lever 30 and the mechanism 21, 20, 15, 16 connected thereto. After a relatively high velocity is attained, the abutment 50a impacts against the bight portion 30a, driving the lever 30 rapidly clockwise, thus transmitting contactclosing forces through the parts 21, 20 and 15 to the contacts 16. The spring 38 continues to expand, following-up the initial impact and imparting additional contactclosing forces. At the end of the contact-closing stroke, the parts are positioned as shown in Fig. 2.

After the switch has been closed, switch opening can be produced by rotating the rock shaft .32 in an opposite or counter clockwise direction from the position of Fig. 2. This again compresses the spring 38 until the toggle link 36 moves counter clockwise overcenter. The spring then discharges and drives the lower abutment 50b into impacting engagement with the lower side of the bight portion 39a, thus transmitting switch-opening forces to the contacts 16 through the parts 30, 21, 20 and 16. This action, coupled with the spring-discharge which follows, returns the parts of the switch to the open position shown in Fig. 1. The abutment 50b is preferably so located .that during this opening stroke, the toggle 37 was allowed to move considerably past its center position before the abutment 50b impacted the bight portion.

For manually oscillating the rock shaft 32 to produce the above-described switch-opening and switch-closing actions, a handle 55 is provided. This handle 55 is connected to the shaft 32 preferably by a suitable lost-motion connection 56 permitting a limited amount of angular motion of the handle 55 relative to the shaft 32. For opening the switch, the handle 55 is operated in a counterclockwise direction from its position of Fig. 2. This drives the toggle link 36 counterclockwise overcenter, whereupon the overcenter spring 38 discharges and opens the contacts, as previously described. For closing the switch, the handle 55 is simply returned in a clockwise direction to its position of Fig. 2. This drives the toggle link 36 clockwise overcenter, whereupon the overcenter,

spring 38 discharges and closes the contacts, as previously described. The lost-motion connection between the handle 55 and the shaft 32, which preferably comprises a pin 57 fixed to the rock shaft and disposed in a slot in the handle 55, allows the rock shaft 32 to overrun the handle when the spring is discharging, thus assuring that the handle will not interfere with the desired high-speed operation of the switch either during opening or closing.

During a switch-openng operation, it will be apparent that the overcenter spring 38 initially is being compressed by counterclockwise rotation of the toggle link 36 and therefore is then exerting no force on the contacts 16. To assure that the contacts 16 do not fall open or are not otherwise accidentally opened during this short interval, a latch is provided. This latch 90 is pivoted on a stationary fulcrum 91 and is biased in a counterclockwise direction by a suitable biasing spring 92. When the switch is in its closed positon of Fig. 2, a latching surface 94 formed on the latch is disposed in latching relationship beneath a pin 95 fixed to the actuating lever 30. In such position, the latch 90 positively holds the contacts 16 in their closed position.

When the toggle link 36 is moved counterclockwise to open the switch, as previously-described, a projection 96 carried by the link 36 engages a cam surface 97 formed on the latch 90. This forces the latch 98 to the left thus releasing the pin 95 and allowing the contacts 16 to be driven open. The projection 96 on toggle link 36 is so located that release of the latch 90 takes place only after the toggle 35 has been driven past center. Latch release occurs, however, prior to the instant that abutment 50b impacts against the bight portion 39a of the lever 30, thus assuring that the latch 90 does not interfere with the desired high speed contact-opening.

Since the latch 90 positively locks the contacts 16 in closed position when the switch is in its fully closed position of Fig. 3, it will be apparent that the latch serves during such intervals to prevent the contacts from being forced open by any abnormal magnetic forces which might be capable of overcoming the bias of the overcenter spring 38.

Opening and closing of the switch can also be initiated by the action of a suitably-controlled, unidirectional electric motor 60, which is capable of oscillating the rock shaft 32 in generally the same manner as the manuallyoperable handle 55. In this connection, the motor 60, when energized,acts througha suitable speed reducer (not shown) to effect rotary motion of the power shaft 62, as is shown in Fig. l. A cam 63 is keyed or otherwise secured to the power shaft 62 and is thus rotated by operation of the motor 60. Coacting with the cam 63 is a V-shaped crank 65 that is secured to the rock shaft 32. This crank 65 carries a pair of cam followers 66 and 67 at the outer end of each of its angularly-spaced arms. Each of these followers 66 and 67 is preferably a roller which is journaled on a pin 68 secured to the crank. The axis of the rock shaft 32, it will be noted from Fig. 3, is laterally offset from the axis of the power shaft 62. When it is desired to utilize the motor 60 for closing the breaker, the motor is energized to rotate the cam 63 counterclockwise from its solid line position of Fig. 1. This acts to lift the follower 66 thereby driving the rock shaft 32 in a clockwise switch-closing direction. When this action has continued to the point where the rock shaft 32 has driven the spring 38 slightly overcenter, the spring 38 discharges to close the switch, as previously described, and, in so doing, lifts the follower 66 from the outer surface of the cam 63 and into the dotted line position shown in Fig. 3. The motor continues rotating the cam 63 until the cam reaches the position shown in Fig. 2, whereupon motor-operation is terminated.

To open the switch, the motor rotates the cam 63 counterclockwise from its position of Fig. 2. This lifts the lower follower 67, thereby driving the rock shaft 32 in a counterclockwise switch-opening direction. When this action has continued to the point where the overcenter spring 38 begins discharging to open the switch, the spring acts to lift the roller 67 from the outer surface of the cam, ultimately returning the follower to itsposition of Fig. 1. The motor continues rotating the cam 63 until the cam has returned to its position of Fig. 1, whereupon motor operation is terminated.

Forcontrolling the operation of the motor, a suitable electrical-control scheme such as that disclosed in the Frank application may be relied upon. Since the details of this control scheme form no part of the present invention, such control scheme has not been-shown on the drawings of this application. To understand the present invention, it is sufficient to understand merely that the control scheme causes the motor to drive the cam 63 counterclockwise from its position of Fig. 1 to that of Fig. 2 during a closing operation and counterclockwise from its position of Fig. 2 to that of Fig. 1 during an-opening operation.

For supplementing the closing action of the overcenter spring 38 and thereby enabling the switch to close against larger inrush currents than it would be otherwise capable, I provide on-the cam shaft 62 an auxiliary cam 100. This auxiliary cam- 100' is freely rotatable with respect to the cam shaft 62 and is spring coupled to the main cam 63- bya suitable spring, such as the torsion spring 101 of'Fig. 1. This torsion spring 101 urges the auxiliary cam into engagement with a pin 102 projecting laterally from the main cam 63.

Assume now that the switch is to .be closed and that, to this end, the main cam 63 is rotated counterclockwise from-its position of rest shown in Fig. 1 to its position of rest shown in Fig. 2. Such rotation initially causesthe main cam 63 to drive the follower 66 up its outer peripheral surface 63a. After a predetermined amount of such movement, the follower 66 contacts the surface 1000 of the-auxiliary cam 100, which is then projecting above the outerperipheral surface 63a of the main cam. This temporarily prevents the auxiliary cam from following along with the main cam, with the result being that continued counterclockwise movement of the main cam separates the two cams and thereby charges the torsion spring 101.

When the main cam 63 has driven the follower 66 to apoint at-which the overcenterspring 38 has passed overcenter, theovercenter spring quickly discharges to drive the contacts 16 toward closed position. This point is depictedin Fig. 3. In discharging, the overcenter spring drives the follower 66 away from the outer periphery 63a of-the'main cam into the dotted line position of Fig. 3.

'whichsupplements the closing forces provided by the overcenterspring 38. This wedging action is highly elfec- -tivein aiding the switch to close against large inrush currents. For example, by adding the auxiliary cam arrangement 100-102 to a- 14.4 kv. switch of the illustrated type, without in any other way modifying the switch, I have been able to increase the closing capacity of the switch from 6000'amperes to 9000* amperes.

The top surface 100]; of the auxiliary cam has an axis of curvature coinciding with the axis of cam shaft 62 1 and thus acts to block return movement of the follower 66 and,the connected contacts until the motor has driven the auxiliary cam counterclockwise clear of the follower. The forces for driving the auxiliary cam counterclockwise free from the follower 66 are transmitted to the cam 100 through the spring 101, which is sufiiciently rigid to overcome any opposing functional forces. When the cam has moved clear of the follower 66, the latch of Fig. 2 is capable of holding the contacts closed against the magnetic forces produced by any currents which might then be flowing through the switch. The motor 60 ultimately drives the cams 63 and into the position of rest depicted in Fig. 2, at which time motor-operation is terminated, as above-described.

I attribute the effectiveness of my auxiliary cam arrangement, in part, to the fact that it delivers supplementary power to the contacts 16 by a substantially nonyielding power path which bypasses the overcenter spring 38. In this regard, assuming that the contacts 16 are nearing the closed position, this non-yielding power path extends from the follower 66 to contacts 16 through the successive parts 65, 32, 36, 50a, 30, 21 and 20. Since this path is substantially non-yielding and bypasses the overcenter spring 38, the supplementary closing forces are applied quickly and positively to the contacts, rather than being cushioned or absorbed by the overcenter spring. 7

Another factor contributing to the effectiveness of my force-supplementing arrangement is that the spring means 101 is charged directly from the motor 60 rather than by energy supplied through the overcenter spring 38, thus assuring that substantially all of the energy stored by the motor in the overcenter spring is available for direct transmittal to the contacts.

Another important factor contributing to the effectiveness of my force-supplementing arrangement is that the motor acts to charge the auxiliary spring means 101 during an interval when little of its output is needed for charging the overcenter spring. In this regard, the. follower 66 is spaced from the charging surface 100a of the auxiliary cam during initial charging of the overcenter spring 38. The follower contacts the surface 100a only when the overcenter spring is adjacent its dead center position, and thus the auxiliary spring 101 is charged by the motor 60 principally during the time that the overcenter spring is adjacent its dead-center position. A relatively small amount of energy is required to rotate the toggle link 36 during this interval, and, for this reason, I utilize the surplus energy which is then available from the motor to charge the auxiliary spring 101. Thus, my disclosed arrangement enables the motor 60 to perform the added function of charging the auxiliary spring and, of particular advantage, enables the motor to perform this. added function without necessitating any increase in its size.

The auxiliary cam 100 is not needed for a switchopening operation. For this reason, the follower 67, which is used for switch opening, projects laterally from the crank 65 to a lesser extent than the follower 66, as will be apparent from Fig. 4. As a result, when the main cam 63 is rotated from its position of Fig. 2 toits position of Fig. 1 during a switch-opening operation, the auxiliary earn 100 moves past the follower 67 without engaging the follower 67.

It will be apparent that the cams 63 and 100 interfere in no significant way with any manually-initiated opening operation which an operator might desire to perform. In this regard, assume that it is desired to manually open the switch after a motor-initiated switch-closing operation. The cams 63 and 100 of the closed switch would be in the position of Fig. 2, as previously described, and, as a result, the follower 66 would be free to move in a counterclockwise switch-opening direction without interference from either of the cams 63 or 100. The operator. could therefore move the handle 55 counterclockwise from the position of Fig. 2 to perform a switchopening operation without interference from the cams 63 and 100. The fact that the auxiliary cam 100 is coupled to the motor shaft 62 and is driven clear of the follower 66 by the motor is, of course, an important factor contributing to the ability of the switch to open without interference from the auxiliary cam 100.

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

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

1. In an electric switch comprising a follower which is movable from a fully-open position to a fully-closed position as said switch is operated through its full closing stroke, a main cam which is actuatable to drive the follower from said fully-open position toward said fullyclosed position, an auxiliary cam, spring means interconnecting said main cam and said auxiliary cam and arranged to be charged by separating motion of said main cam relative to said auxiliary cam, said follower acting while being driven through an intermediate portion of said closing stroke by said main cam to restrain said auxiliary cam from following said main cam thereby effecting separation of said cams and charging of said spring, said follower permitting said spring to discharge and drive said auxiliary cam toward a blocking position behind said follower near the end of said closing stroke, a driving cam surface on said auxiliary cam through which energy released from said spring is imparted to said follower as said auxiliary cam moves toward its blocking position, said driving cam surface being shaped to provide a wedging action which aids in forcing said switch closed.

2. In an electric switch comprising a follower which is movable from a fully-open position to a fully-closed position as said switch is operated through its full closing stroke, a main cam which is actuatable to drive the follower from said fully-open position toward said fullyclosed position, an auxiliary cam, spring means interconnecting said main cam and said auxiliary cam and arranged to be charged by separating motion of said main cam relative to said auxiliary cam, said follower acting while being driven through an intermediate portion of said closing stroke by said main cam to restrain said auxaliary cam from following said main cam thereby effecting separation of said cams and charging of said spring, said follower permitting said spring to discharge and drive said auxiliary cam toward a blocking position behind said follower near the end of said closing stroke, a driving cam surface on said auxiliary cam through which energy released from said spring is imparted to said follower as said auxiliary cam moves toward its blocking position, said driving cam surface being shaped to provide a wedging action which aids in forcing said switch closed, and means including a switch-operating motor for driving said cams from a first position of rest to a second position of rest during and immediately after a closing operation, said auxiliary cam being so shaped that motor operation adjacent said second position of rest acts to free said auxiliary cam from blocking relationship relative to said follower.

3. In an electric switch, a pair of separable contacts, a drive shaft, a toggle link secured to said shaft, an overcenter spring coacting with said toggle link to form a toggle, said drive shaft being rotatable in one direction to charge said spring and drive said toggle link into an overcenter position relative to said spring whereupon said spring discharges and continues motion of said link, means coupling said toggle link to one of said contacts for transmitting contact-closing force from said spring to said one contact, means for effecting rotation of said rock shaft comprising a follower coupled to said rock shaft and a main cam for actuating said follower, an auxiliary cam, auxiliary spring means coupling said auxiliary cam to said main cam, means for charging said auxiliary spring means in response to that motion of said main cam which drives said toggle link into said overcenter position, discharge of said overcenter spring acting to withdraw said follower from said main cam and permitting said auxiliary spring means to discharge and drive said auxiliary cam into camming engagement with said follower, said camming engagement acting near the end of a contact closing operation to force continued withdrawal of said follower from said main cam whereby to provide supplementary contactclosing forces near the end of said closing operation.

4. The switch of claim 3 in which said supplementary contact-closing forces are transmitted to said one contact by a substantially non-yielding power path which bypasses said overcenter spring.

5. The switch of claim 3 in which said means for charging the auxiliary spring is ineffective during initial charging of said overcenter spring and is effective only when said toggle is in the region adjacent its dead center.

6. The switch of claim 3 in combination with means including a switch-operating motor for driving said cams from a first position of rest to a second position of rest during and immediately after a closing operation, said auxiliary cam having a blocking surface which is driven behind said follower at the end of a closing operation to hold said one contact closed, said blocking surface being so shaped that motor operation immediately after said one contact is closed maintains said contact blocked closed, additional motor-operation acting to drive said blocking surface free of said follower and to position said auxiliary cam in said second position of rest.

7. In an electric switch, a pair of separable contacts, a drive shaft, a toggle link secured to said shaft, an overcenter spring coacting with said toggle link to form a toggle, said drive shaft being rotatable in one direction to charge said spring and drive said toggle link into an overcenter position relative to said spring, whereupon said spring discharges and continues motion of said link, means coupling said toggle link to one of said contacts for transmitting contact-closing force from said spring to said one contact, means for effecting rotation of said rock shaft comprising a follower coupled to said rock shaft and a main cam for actuating said follower, an auxiliary cam, auxiliary spring means coupling said auxiliarycam to said main cam and arranged to be charged by separating motion of said main cam relative to said auxiliary cam, said follower acting while being driven through an intermediate portion of said closing stroke by said main cam to restrain said auxiliary cam from following said main cam, thereby effecting separation of said cams and charging of said auxiliary spring, discharge of said overcenter spring acting to withdraw said follower from said main cam and permitting said auxiliary spring means to discharge and drive said auxiliary cam into camming engagement with said follower, said camming engagement acting near the end of a contact-closing operation to force continued withdrawal of said follower from said main cam whereby to provide supplementary contact-closing forces near the end of said closing operation.

8. The switch of claim 7 in which said follower is ineffective to restrain said auxiliary cam from following said main cam during initial charging of said overcenter spring and is effective to restrain said auxiliary cam only when said toggle is being driven through the region adjacent dead center.

References Cited in the file of this patent UNITED STATES PATENTS 1,741,824 Burnham Dec. 31, 1929 2,009,383 Blume July 30, 1935 2,581,181 Favre Jan. 1, 1952

Images