US3526860A

US3526860A - Automatic circuit interrupter

Info

Publication number: US3526860A
Application number: US720168A
Authority: US
Inventors: Kazuo Henry Date
Original assignee: McGraw Edison Co
Current assignee: Cooper Industries LLC
Priority date: 1968-04-10
Filing date: 1968-04-10
Publication date: 1970-09-01
Anticipated expiration: 1987-09-01
Also published as: GB1222869A

Description

Sept.- 1, 1970 K. H. DATE AUTOMATIC CIRCUIT INTERRUPTER 5 sheets-sheet 1 Filed April 10. 1968 Sept. 1, K DATE v AUTOMATIC CIRCUIT INTERRUPTER I Filed April 10. 1968 5 Sheets-Sheet 2 P 1970 K. H. DATE AUTOMATIC c acurw INTERRUPTER 5 Shets-Sheet 5 mad April 10, 1968 mun u nul 1 5w i/ my 2 I ,B y ac/ 1am! I C;

Sept. 1, 1910 K H. DATE 3,526,860

AUTOMATIC CIRCUIT INTERRUPTER Filed hpril 10, 1968 5 Sheets-Sheet 4.

I l wezuor' 2y mm c Q Sept. 1, 1910 K. H. DATE AUTOMATIC CIRCUIT INTERRUPTER Filed April 10, 1968 5 Sheets-Sheet 6 United States Patent 3,526,860 AUTOMATIC CIRCUIT INTERRUPTER Kazuo Henry Date, South Milwaukee, Wis., assignor to McGraw-Edison Company, Elgin, L, a corporationof Delaware Filed Apr. 10, 1968, Ser. No. 720,168 Int. Cl. H01h 75/04 US. Cl. 335-26 18 Claims ABSTRACT OF THE DISCLOSURE An operating mechanism for opening and closing a contactor. A bell crank is secured to a spring and to the con- This invention generally relates to an operating mechanism for the contactor of an automatic circuit interrupter of the type commonly known as a recloser. More particularly, the invention relates to an operating mechanism for a vacuum contactor of a recloser.

Reclosers are generally installed in electrical distribution systems in a main line or at the origin of a branch line which in turn supplies other subsidiary lines that are protected by fuses. In the event that a fault occurs on the load side of a recloser, the recloser executes one or more fast opening andone or more relatively delayed reclosing operations. The relationship of the fault current to the time required for opening the interrupter during the fast openingoperations is such that the recloser is faster than the melting time-current characteristic of the fuse so the recloser itself is relied upon as a sole means to clear the fault without damage to the fuse. Most faults are cleared without melting the, fuse during the fast opening operations. In instances vwhere the fault is not cleared duringa fast Opening sequence, the delayed reclosing operations will take place. The delayed reclosingoperations are obtained by presetting the recloser to automatically change its time-current characteristic so that further opening operations are retarded to provide sufficient time to melt .the fuse. If the fault clears due to melting of the fuse during any of the successive delayed operations, the recloser closes and maintains power on the line. If the fault is not cleared during the total sequence of opening and closing operations, the recloser will automatically lock it- .self out and disconnect the branch line being protected from its source. In order to properly coordinate a particular' recloser with other reclosers and fuses it is necessary that the recloser. have a predictable time-current characteristic. a

. The above discussion applies equally to reclosers utilizing either .oil type interrupting contactors or vacuum contactors. With the advent of vacuum contactors, it has become desirable to develop a vacuum contactor and contactor operating mechanism which can be interchanged with the older oil type contactors and associated operating mechanisms so that the latter can be readily converted to vacuum contactor type reclosers. One of the requirements of reclosers using vacuum contactors is that the operating mechanism for the vacuum contactor be balanced or compensated for the difference in the operating force due to the difference between the pressure in the vacuum container and the pressure external the container.

A major problem in prior art reclosers is that of assuring optimum precision and uniformity insofar as time current characteristics and positive operation are con- 3,526,860 Patented Sept. 1, 1970 cerned. Precise and uniform operation is diflicult to obtain because of unpredictable dynamics over a widely varying range of currents between minimum trip current and maximum fault current. A further problem related to the conversion of the recloser to a vacuum contactor type is that of matching the operating characteristics of the vacuum contactor operating mechanism to those of the oil contactor operating mechanism.

It is accordingly an object of the invention to provide a contact operating mechanism having precise and predictable dynamics over the full current range of the interrupter rating.

Another object of the invention is to provide a recloser contact operating mechanism that will actuate precisely without being affected by the friction of the moving components.

Another object of the invention is to provide a recloser operating mechanism that is particularly suitable for operation of a vacuum contactor and that has precise and predictable actuating characteristics.

Another object of the invention is to provide a vacuum contactor operating mechanism which is interchangeable with an oil type contactor operating mechanism in a recloser and which has the same time-current characteristic and sequential operating characteristic as the oil type contactor and interrupting mechanism.

A still further object of the invention is to provide a vacuum contactor and snap action operating mechanism for clearing fault with great rapidity and which is simple in form, economical to manufacture and easy to maintain or replace.

The above stated objects are accomplished by providing an insulated bell crank lever attached to a vacuum contactor connected in the circuit to be interrupted and a spring biased overtoggle arrangement acting to hold the bell crank lever and the vacuum contactor in a closed position and, when overtoggled, to open the contactor. A lever arm is attached to the overtoggle arrangement and is moved to actuate the overtoggle arrangement and impact the bell crank lever when a solenoid operated plunger pushes against tre lever arm. When overtoggle occurs and the bell crank lever is impacted, the vacuum contactor and bell crank lever are forced to their open positions. After the circuit is opened by the vacuum contactor, the opening springs will contract to return the plunger back to its original position and simultaneously close the vacuum contactor at the last or unimpeded part of the plunger stroke.

Other objects and advantages of the invention will in part be obvious and will in part appear hereinafter. For a fuller understanding of the nature and objectsof the invention, reference should be had to the following detailed description taken in connection with the following drawings in which:

FIG. 1 is a vertical sectional elevational view, with parts broken away, of a reclosing circuit interrupter assembly embodying the invention;

FIG. 2 is a side sectional view, with parts broken away, showing the contactor operating mechanism and vacuum contactor of the circuit interrupter as they ap pear when in normal or closed circuit condition;

FIG. 3 isa side sectional view, with parts broken away, of the contactor operating mechanism and vacuum contactor of the circuit interrupter as they appear following occurrence of a fault and just prior to actuation of the operating mechanism and opening of the vacuum contactor;

FIG. 4 is a side sectional view, with parts broken away, of the contactor operating mechanism and vacuum contactor of the circuit interrupter as they appear after occurrence of a fault and subsequent to actuation of the operating mechanism and opening of the contacts of the vacuum contactor;

FIG. 5 is another side sectional view, with parts broken away, of the contactor operating mechanism and vacuum contactor of the circuit interrupter showing the position of the operating mechanism and vacuum contactor after both have operated and just after the operating mechanism has acted to return the actuating plunger to its normal position;

FIG. 6 is an end view of the contactor operating mechanism and the vacuum contactor; and

FIG. 7 is a top view, with parts broken away, of the contactor operating mechanism.

Referring to the drawings,.the general construction of the recloser circuit interrupter includes a metal tank 2 filled with dielectric fluid such as oil, a lock-out mechanism 4, a hydraulic timing means 6, an electromagnetic coil 8 having a plunger 10' engaging the hydraulic timing means 6, a vacuum contactor 12 and a contactor operating mechanism 14 attached to the vacuum contactor 12 and actuated by the plunger 10. The metal tank 2 is provided with a cover 16 having a pair of bushings 18, only one of which is shown, for the purpose of serially connecting the recloser in a power line. The current path through the recloser between the two bushings 18 constitutes a series circuit including the electromagnetic coil 8 and the vacuum contactor 12. For the sake of clarity, the lead wires extending through the bushings 18 and connecting the electromagnetic coil 8 and vacuum contactor 12 are omitted. The upper end 20 of the plunger 10 is adapted to be drawn downwardly into coil 8 when a current value above minimum trip passes through the coil. Movement of the plunger 10 downwardly actuates the operating mechanism 14 and causes opening of the vacuum contactor -12 to open the series circuit and de-energize the coil 8.

Following opening of the circuit, the operating mechanism 14 acts to return the plunger 10 to its uppermost position and cause the vacuum contactor 12 to reclose the circuit and again energize the coil 8. The operation and construction of the operating mechanism 14 will be discussed in detail later in this specification.

Each time the plunger 10 descends it pumps a measured quantity of oil which in turn causes a predetermined degree of advancement of the trip piston stem 22. After a predetermined number of such operations, the trip piston stem 22 advances to engage and release the latch finger 24 which comprises part of the lock-out mechanism 4. Releasing of the latch finger 24 results in operation of the lock-out mechanism 4 to cause the plunger 10 to descend and permanently hold the contact operating mechanism 14 in its open position in which the vacuum contactor 12 is held open. The plunger 10 may thereafter be released to allow the contactor 1-2 to close only by a manual reset provision (not shown) comprising part of the lock-out mechanism 4. The features of the lock-out mechanism 4 and hydraulic timing means 6 are well known in the art and, if desired, a detailed description of their construction and operation maybe found in U.S. Pat. No. 2,926,228, issued to K. H. Date et al. on Feb. 23, 1960, and assigned to the instant assignee.

The construction and operation of the vacuum contactor 12 and the contactor operating mechanism 14 will now be discussed in detail. With reference to FIG. 6, a frame assembly 30 comprises part of the recloser and includes side members 32 and two U-shaped members 34 bolted to the side members 32 by bolts 36. The vacuum contactor 12 is positioned at the lower end of the frame assembly 30 and includes a vacuum container 38, a movable contact stem 46 extending from one end of the vacuum container 38 and a stationary contact stem 42 extending from the other end of the vacuum container 38. The stationary contact stem 42 is supported by bracket 44 which is attached to the side members 32 by bolts 46.

The movable contact stem 40 is supported on the frame assembly 30 by the bracket 48 which is attached to the side members 32 by bolts 50. The movable contact stem 40 slides through an insulating sleeve 52 which is positioned between the movable contact stem 40 and the bracket 48. The purpose of the insulating sleeve 52 is to guide the movable contact stem 40- With a minimum of friction'and wear during its reciprocating movement and to prevent parallel current paths and arcing to the bellows 66 which seals the interior of the vacuum container 38 from the outside atmosphere. The stationary contact 54 and movable contact 56 are respectively aflixed to the stationary contact stem 42 and movable contact stem 40 within the vacuum container 38. The vacuum contactor 12 is connected in series with the power line through the

leads

58 and 60 respectively connected to the stationary contact stem 42 and movable contact stem 40. An electrostatic shield 62 surrounds a portion of the bellows 66 and an arc shield 64 is disposed between the

contacts

54 and 56 and the vacuum container 38 for preventing condensation of vaporized contact material on the inner surface of the vacuum container 38.

With reference to FIGS. 2-7, the contactor operating mechanism 14 includes a double member lever arm having a pair of congruent levers and adapted to pivot on a fixed transverse bolt 82 spanning between the side members 32. The lever arm 80 carries a roller 86 which engages and receives force from plunger 10 when plunger '10 is moved downwardly by the electromagnetic coil 8. There is a collapsible linkage 70 having a lower-double arm link 88 and an upper link 90 pivotally attached to the lever arm 80 by pin 92 and positioned between the two levers of lever arm 80 by the spacer sleeves 94. The lower double arm link 88 is pivotally connected to the upper link 90 by the pin 96 and is pivotally supported on the side members 32 of the frame assembly 30 by the pins 98.

A double member bell crank lever is pivotally supported at its fulcrum 112 on the side members 32 by the pins 114. The 'bell crank lever 110 has a lever arm 116 pivotally connected to the movable contact stem 40 of the vacuum contactor 12 by the pin 118. The bell crank lever :110 is held on the machined pin 118 and the movable contact stem 40 is attached to and centered on pin 118 by cotter pins 120. A pair of overcenter contact springs 124 are secured at their ends to pin 96 which also acts as pivot point for the collapsible linkage 70. The springs 124 are held in position by spacer sleeves 126 carried on pin 96. The springs 124 are pivotally attached at their other ends to a grooved transverse pin 130. A pair of link arms 128 are pivotally supported on side members 32 by pins 114 and are pivotally connected to the transverse pin 130 adjacent its ends. The ends of the transverse pin 130* are slidably guided within the arcuate slots 113-2 formed in the members of bell crank lever 110*. As the drawings indicate, sliding motion of the pin 130 requires the contact opening springs 124 and the link arms 128 to move along the length of the arcuate slots 132. The link arms 128 and the bell crank lever 110 are held in a parallel relationship by the washers 136.

A compensating arrangement adapted to counterbalance the operating force difference on the operating mechanism' 14 due to the pressure differential external the vacuum container 38 and the pressure within the vacuum container 38 includes a counterbalancing linkage having a pair of upper link arms and a pair of lower link arms 152 (see FIGS. 2-5 and 7). The lower link arms 152 are pivotally connected at their lower ends by pin :154 to an end of the lever arm 134 of the bell crank lever 110. The pin 154, supported on bell crank lever 110, also carries the roller 156 against which the roller 86 impacts when the lever arm 80 is pushed down by the plunger 10. The spacer sleeves 158 are supported on pin 154 and maintain the link arms 152 and the roller 156 in their proper relationships (see FIG. 7). The upper link arms 150 are pivotally anchored to the side members 32 by pins 160. The upper link arms 150 and lower link arms 152 are pivotally connected by transverse pin 164. The balancing springs 166 are connected between the transverse pin 164 and the pin 82 supported on the side members 32.

The operating sequence positions of the contactor operating mechanism 14 are shown in FIGS. 2-5. In FIG. 2, the plunger is shown in its upward position in which it is held by the force of the contact operating springs 124 acting through

link arms

88 and 90 and the lever arm 80 when fault current is not passing through the electromagnetic coil 8. In the position of the contactor operating mechanism 14 shown in FIG. 2, the contact operating springs 124 are held in a position above the fulcrum 112 of the bell crank lever 1410 by the link arms '88 and 90. In this position the transverse pin 130* is held against the upper ends of the arcuate slots 132 by the contact operating springs 124- to pivot the bell crank lever 110 clockwise about its' fulcrum 112 and hold the movable contact stem 40 in its inward position and the

contacts

54 and 56 in engagement with each other. When the

contacts

54 and 56 are engaged, the electrical circuit in 'which they are connected is closed. In the position of the bell crank lever 110 shown in FIG. 2, counterbalancing linkage 140 acts to pivot the bell crank lever 110 in a counter-clockwise direction to compensate for the relative lack of pressure on the movable contact stem 40 from within the vacuum container 38.

FIG. 3 shows the position of the plunger 10, the lever arm 80 and the collapsible linkage 70 after the plunger 10 has started its downward movement but before the contactor operating mechanism 14 has been actuated to open the

contacts

54 and 56. The electromagnetic coil 8 is now carrying the predetermined amount of overcurrent required to push the plunger 10 downward against the lever arm 80 to the point where it impacts the roller 156 on the bell crank lever 110. Movement of the lever arm 80 downwardly causes the collapisble linkage 70 to collapse to move the pivot point at pin 96 of the contact operating springs 124 below the fulcrum 112 of the bell crank lever 110. When the contact operating springs 124 are below the fulcrum 112, they apply force to the bell crank lever 110 in a direction which tends to pivot the bell crank lever 110 in a counter-clockwise direction. In addition, the direction of the force now applied by the springs 124 is such that downward movement of the pin 130 is no longer impeded due to the arcuate shape of the slots 132. The pin 130 will thus snap to the bottom of the slots 132 and impact the bell crank lever 110 to provide a snap action overtoggle of springs 124. The impacting of bell crank lever 110 further assists in pivoting the bell crank lever 110 counter-clockwise and moving the slots 132 downward to increase the leverage of springs 124 for positive contact opening operation. The contact opening springs 124 are thus snapped to an overtoggled position which causes them to pivotallysnap the bell crank lever 110 in a counter-clockwise direction as assisted by the snap action movement of the transverse pin 130. As is also shown in FIG. 3, the

contacts

54 and 56 continue to be in an engaged position until the lower roller 156 is impacted to effect a forceful separating movement to

contacts

54 and 56. The impacting of the roller 156 takes place at substantially the same instant that the operating springs 124 overtoggle with a snap action so that all contact opening forces occur simultaneously.

In FIG. 4, the contactor operating mechanism 14 is shown after the contact operating springs 124 have overtoggled and snapped the transverse pin 130 down to the bottom of the arcuate slot 132 and pivoted the bell crank lever 110 to its position in which the movable contact stem 40 is moved away from the vacuum container 38 and the

contacts

54 and 56 are opened to interrupt the circuit. It can thus be seen that overtoggle of the contact operating springs 124, the snap of the transverse pin 130 against the bottom of the slots 132 and the impact of the roller 86 on the lever arm against the roller 156 together provide a high speed, forceful pivoting action on the bell crank lever to result in positive bell crank lever movement and opening of the contacts regardless of friction at the pivoting points in the operating mechanism and a possible welding of the contacts from high currents.

In FIG. 5, the

contacts

54 and 56 are shown in their open position in which the power line circuit is opened and the electromagnetic coil 8 is de-energized. Under these conditions the plunger 10 is free to move upward and is returned to its upward position by contraction of the contact operating springs 124. A comparison of FIGS. 4 and 5 will show that when the plunger is in its fully extended downward position the contact operating springs 124 are in an extended, charged position and are held that way as long as the plunger 10 is held downward by the coil 8. When fault current is no longer flowing through the coil 8, the plunger 10 will not hold the contact operating springs 124 in their extended position and the springs will then contract to open the collapsible linkage 70 and force the lever arm 80 and plunger 10 upward. The contact operating mechanism 14 will then be in its position shown in FIG. 5. When the pivot point at pin 96 of the contact operating springs 124 has moved above the fulcrum 112, the bell crank lever 110 will again be pivoted about its fulcrum 112 so that it snaps clockwise to its original position shown in FIG. 2 to close the

contacts

54 and 56. Also, as the operating springs 124 overtoggle, the transverse pin connected to the link arm 128 is snapped upward and the bell crank 110 is pivoted clockwise to close the

contacts

54 and 56. The contact operating mechanism 14 has now completed a contact opening and closing operation including a reclosing time delay between opening and closing and is ready to recycle in the event of further fault current flow through the coil 8. If the fault current flow continues, the hydraulic timing means 6 will, after a preset number of operations, actuate the look-out mechanism 4 to hold the plunger 10 in its downward position and cause the contact operating mechanism 14 to hold the

contacts

54 and 56 open until the look-out mechanism 4 has been manually reset.

Although a preferred embodiment of the invention has been illustrated and described, the disclosure is not to be interpreted as limiting, for the invention may be variously embodied and is to be construed in accord with the claims which follows.

What is claimed is:

1. The combination with a reclosing circuit interrupter connected in an electrical circuit and including a contactor means having an open and closed position for interrupting the electrical circuit, an electromagnetic coil and a plunger having a normal position relative to said coil and being movable from said normal position by the electromagnetic coil when the coil is energized by an overcurrent value in the electrical circuit of:

bell crank means directly secured to the contactor means and being movable transversely relative to the path of movement of said plunger between first and second positions respectively corresponding to the closed and open positions of the contactor means, said bell crank means being actuated and moved to its second position by movement of the plunger when the electromagnetic coil is energized to move the contactor means to its open position; and

resilient means directly secured to the bell crank means for returning the bell crank means to its first position and the contactor means to its closed position sub sequent to actuation of the bell crank means by the plunger.

2. The combination according to claim 1 wherein said resilient means has a first position in which it urges the bell crank means and the contactor means toward their corresponding first and closed positions and a second 7 position in which it urges the bell crank means and the contactor means toward their corresponding second and open positions.,

3. The combination according to claim 2 further comprising linkage means secured to the resilient means and engaged by the plunger when it is moved by the coil for moving the resilient means from its first position to its second position and for returning the plunger to its normal position after the plunger has actuated the bell crank means to move the contactor means to its open position.

4. The combination with a reclosing circuit interrupter connected in an electrical circuit and including an electromagnetic coil and a plunger movable along a path in the direction of its length by the electromagnetic coil when a predetermined current value flows from the electrical circuit through the coil of:

contactor means connected in the electrical circuit and being movable to a first position in which the electrical circuit is closed and to a second position in which the electrical circuit is opened and the electromagnetic coil is deenergized;

bell crank means pivotally secured to the contactor means and being movable between first and second positions respectively corresponding to the first and second positions of the contactor means, said bell crank means being positioned in the path of movement of and actuated by the plunger when the plunger is moved by the electromagnetic coil to move the contactor means from its first to its second position, whereby the electrical circuit is opened and the electromagnetic coil deenergized;

resilient means secured to the bell crank means and having a first position in which it moves the bell crank means and the contactor means to their respective first positions and a second position in which it acts together with the plunger to move the bell crank means and the contactor means to their respective second positions and a second position in which it acts together with the plunger to move the bell crank means and the contactor means to their respective second positions, said resilient means also urging the plunger in a direction away from the bell crank means while the resilient means is in said second position after the electrical circuit is opened and the electromagnetic coil has ceased to move the plunger; and

linkage means secured to the resilient means, said linkage means including a movable lever arm positioned in the path of movement of the plunger and engaged by the plunger when it is moved by the coil to actuate the linkage means for moving the resilient means from its first position to its second position and for engaging and moving the plunger along said direction away from the bell crank means in response to the resilient means subsequent to the movement of the resilient means to its second position and the opening of the electrical circuit.

'5. The combination according to claim 4 wherein:

said contactor means comprises a vacuum contactor having a container defining a vacuum space; and including balancing means secured to the bell crank for counterbalancing the force on the vacuum contactor due to the difference in pressure within said vacuum container and the pressure exterior of the container.

6. The combination according to claim 4 wherein:

said bell crank means includes a fulcrum about which it pivots and a lost motion slot spaced from said fulcrum and having a length substantially transverse to a line extending from said fulcrum; and

said resilient means includes a toggle arm guided within the lost motion slot and being movable between opposite ends of the slot to guide the resilient means between its first and second positions.

7. The combination according to claim 6 wherein said linkage meansincludes a pair of pivotally connected collapsible link arms secured at their connection to the resilient means and collapsing to extend the resilient means and move the resilient means from its first to its second position when the linkage means is actuated by the plunger and being extended to return the resilient means to its first position and move the plunger away from the bell crank means in response to contraction of the resil ient means after the electrical circuit is opened and the electromagnetic coil has ceased to move the plunger.

8. The combination with an automatic circuit interrupter connected in an electrical circuit and including an electromagnetic coil and a plunger movable along a path in the direction of its length by the electromagnetic coil when a predetermined current value flows from the electrical circuit through the coil of:

lever arm means pivotally supported on the interrupter and positioned in the path of movement of the plunger, said lever arm means being engaged and pushed by the plunger when the plunger is moved by the electromagnetic coil;

bell crank means including two lever arms and a fulcrum pivotally supported on the interrupter for moving the contactor means between its first and second positions, said bell crank means being pivotable between first and second positions respectively corresponding to the first and second positions of the contactor means, the first of said lever arms being attached to the contactor means and the second of the lever arms being positioned in the path of movement of said lever arm means whereby the lever arm means impacts and pushes the second lever arm when the plunger engages and pushes the lever arm means to pivot the bell crank means and move the contact means to their respective second positions; and

resilient means secured to the bell crank means and the lever arm means and having a first position in which it urges the bell crank means and the contact means toward their first positions and being movable to a second position by the lever arm means in which the resilient means acts together with the plunger to pivot the bell crank means and move the contact means to their second positions.

9. The combination according to claim 8 wherein said resilient means is charged in its second position relative to its charge when in its first position and acts to discharge itself and return itself, the bell crank means and the contactor means to their associated first positions when the electromagnetic coil is deenergized and the plunger ceases to push the lever arm means.

10. The combination according to claim 8 wherein said resilient means includes a collapsible linkage means having an open position in which the bell crank means is held in its first position and a relatively closed position in which the bell crank means is held in its second position until the plunger ceases to push the lever arm means.

11. The combination according to claim 8 wherein:

said contactor means comprises a vacuum contactor including a container defining a vacuum space; and including resilient balancing means secured to the bell crank means for counter-balancing the force on the vacuum contactor due to the difference between the vacuum pressure within said container and the higher pressure external the container.

12. The combination according to claim 8 wherein:

said bell crank means includes an arcuate shaped lost motion slot spaced from the fulcrum and having a length transverse to a line extending from the fulcrum; and

said resilient means includes a toggle arm having a free end slidably guided within the lost motion slot and being movable between opposite ends of the slot to guide the resilient means between its first and second positions.

13. The combination according to claim 12 wherein said lost motion slot is positioned along the length of the second lever arm of the bell crank means transverse to the length of the second lever arm.

14. The combination according to claim 8 wherein:

said resilient means includes a toggle arm having a free end slidably guided within the lost motion slot and being movable between opposite ends of the slot to guide the resilient means between its first and second positions, a collapsible linkage means having an open position in which the bell crank means is held in its first position and a relatively closed position in which the bell crank means is held in its second position until the plunger ceases to push the lever arm means, and a spring connected between the free end of said toggle arm and the collapsible linkage means, said spring being relatively contracted when the resilient means is in its first position and extended and charged when the resilient means is in its second position.

15. The combination according to claim 14 wherein:

said contactor means comprises a vacuum contactor including a container defining a vacuum space; and including a resilient balancing means secured to the bell crank means for counter-balancing the force on the vacuum contactor due to the difference between the vacuum.

pressure within said container and the higher pressure external the container.

16. The combination according to claim 15 wherein said resilient balancing means includes a pair of pivotally connected link arms connected to the bell crank means and having a spring attached to the link arms at their pivotal connection for applying counter-balancing force to the bell crank means.

17. The combination according to claim 1 wherein:

said bell crank means includes a first lever arm directly secured to said contactor means and a second lever arm, said lever arms each being movable transversely relative to each other, said second lever arm being positioned in the path of movement of and being moved by the plunger when the latter is moved in response to energization of said coil whereby the contactor means is moved to its open position in a direction transverse to that of the plunger movement; and said resilient means has a position in which it simultaneously returns the plunger and the contactor means to their respective normal and closed positions.

18. The combination according to claim 17 wherein said resilient means compress a single spring.

References Cited UNITED STATES PATENTS 3,189,708 6/1965 Heintz 335-26 2,145,741 l/l939 Stablein et a1. 33526 FOREIGN PATENTS 1,282,733 4/1962 France.

BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner