US3243538A

US3243538A - Latch for arc chute switch

Info

Publication number: US3243538A
Application number: US286661A
Authority: US
Inventors: Sigurd O Rodeseike
Original assignee: ITE Circuit Breaker Co
Current assignee: ABB Inc USA; ITE Circuit Breaker Co
Priority date: 1963-06-10
Filing date: 1963-06-10
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29
Also published as: GB1000201A

Description

s. o. RODESEIKE LATCH FOR ARC GHUTE SWITCH March 29, 1966 4 Sheets-Sheet 1 Filed June 10, 1963 March 1966 s. o. RODESEIKE LATCH FOR ARC CHUTE SWITCH 4 Sheets-Sheet 2 Filed June 10, 1963 5760.90 0. AJJESE/IE March 29, 1966 s. o. RODESEIKE 3,243,538

. LATCH FOR ARC CHUTE SWITCH Filed June 10, 1963' f V p 1 4 Sheets-Sheet 5 March 29, 1966 s. o. RODESEIKE 3,243,538

' LATCH FOR ARC CHUTE'SWITGH Filed June 10, 1963 4 Sheets-Sheet 4 JE 5.5a.

' INVENTOR. 5/6040 a fdazfi/mi aaaasas switch.

An additional object of this invention is to provide such a load break interrupter wherein the auxiliary blade is biased in both directions with respect to its pivotal engagement to the main blade, to thereby provide rapid movement during both switch opening and closing.

' These as Well as other objects of this invention will readily become apparent after reading the following descriptions of the accompanying drawings in which: FIGURE 1 is a side elevational view of an interrupter switch arranged in accordance with the teachings of our invention, showing the contacts in the fully closed position.

FIGURE 2 is a plan view of the load interrupter shown in FIGURE 1.

FIGURES 3 and 4 are side elevation views of the interrupter shown in the tripped and fully opened positions, respectively. I

FIGURE 3 is a cross-sectional view of auxiliary contacts taken along the arrows A--A of FIG. 3.

FIGURE 5 is a side elevation of the interrupter switch shown in an intermediate position during closing.

FIGURES 6 and 6a are plan and side elevation views respectively of a preferred stop means employed in the arc chute chamber of; FIGURES 1 5 which embodies the concepts of the instant invention.

FIGURE 7 is a perspective view showing the preferred auxiliary blade biasing arrangement of our invention.

FIGURES 8 and 8a are side elevation and plan views respectively of the auxiliary blade.

- FIGURES 9 and 9a are side elevation and plan views P ive y of the auxiliary blade biasing spring.

FIGURES 10 and 10a are side elevation and plan views respectively of a spring stop means which may be used in conjunction with the biasing means of FIGURE 9 to appropriately load the'spring during opening and closing operation of the interrupter switch. 7

FIGURE 11 shows an end view of the arc chute of FIGURE 1. I

1 Referring now to the figures wherein like numerals define like elements, FIGURES 1 and 2 illustrate a conventional load interrupter switch 10 modified in accorda'rice withthe teachings of our invention. Switch 10 is comprised of a pair of supporting

insulators

11 and 12, such as porcelain insulators and the like, onto which the load interrupter is mounted. The

insulators

11 and 12 are mounted to a base or support means 13 in any suitable manner. Back connected

insulators

14 and 15 are secured to 13'when required, the

insulators

14 and 15 being provided with contact nuts 16 and 17 respectively for mounting the circuit to be protected. When the back connected mode of FIGURE 1 is not utilized, then the

terminals

22 and 33 are electrically connected to the circuit to be protected. Alternatively,

terminals

22 and 33 may be removed when back

connections

14 and 15 are employed. Base 13 is provided with

apertures

18 and 19 for mounting to a support means in .an appropriate manner.

. Insulator 11 has a unitary molded terminal 20 secured thereon by fasteners 21. The integral terminal portion 22 of terminal member 20, having apertures 23 therethrough, provides the means for connecting the line conductor thereto. Integral hinge tongue 24 of terminal member 20 pivotally' connects the load conductor main switch blade 28 which is secured to an aperture in hinge tongue 24 by.means of fasteners 27. Electrical contact pressure is supplied at the hinge by stop nuts 26 and washers which cooperate with fasteners 27, thereby providing a uniform contact pressure between blade 28 and tongue 24.

As is more clearly shown in FIGURE 2, switch blade 28 is preferably of a split construction including individual space blade sides 29. The individual blade sides 29 are pivotally mounted on the hinge tongue 24 with the sides located on the opposite sides of the hinge tongue respectively.

The insulator 12 located at the disconnect end of the load interrupter is also provided with a unitary terminal member 30 which is supported to terminal 12 by fastener 31. Apertures 33 are provided in the terminal portion 32 of unitary terminal member 30 for connection of a line thereto. The unitary terminal 30 is provided with an inter-gap upstanding break tongue 30, which is slotted at its outer end as shown at 35 to receive a bolt 36, which serves to secure the break ends of main switch blade sides 29. The bolt 36 extends through the blade sides 23 at stop nuts 37 and 38 to maintain the break sides together. A spacing sleeve (not shown) is provided on fastener36 between break sides 29 for preventing undue movement of the .blade sides towards each other. The projections 35 and 40, which form the slot 35 of tongue 34 are arranged so that projection 39 is longer than projection 40, for a purpose to be more fully described. Auxiliary switch blade 41 is pivotally mounted to main switch blade 28 by a fastening means at 43. The fastening means includes a torsion spring 44 and spring stop means 45, which operatively engage end 42 of the auxiliary blade during opening and closing of the switch, to thereby load the auxiliary bladeforrapid movement into and out of engagement with its respective contacts.

' Auxiliary blade 41 is operatively positioned to enter arc chute during operation of the switch. Arc chute 50 includes a narrow passageway 51 between

opposed walls

53, and 54 for the reception of auxiliary blade 41. Passageway 51 is preferably made just slightly larger than the thickness of auxiliary blade 41, allowing only asm-all clearance between the blade and the

insulating members

53 and 54. Arc chute 50 further includes a pair of biased auxiliary contacts 52 electrically connected to main stationary contact 30. (See FIGURES 3 and 3'.) The inner walls facing narrow passageway 51 are lined with a material having high gas evolving extinguishing properties secured to the internal surfaces of

walls

53, 54 in any well known manner. The gases which areinvolved within the arc chute during operation of the switch act to extinguish the arc in a manner well known in the art.

As an alternative to a gas evolving liner, an arc chute 50 may be formed entirely of gas evolving material, thereby avoiding the necessity of providing a separable liner, and also reducing the number of parts requird to form: the arc chute. p 7

In accordance with our invention a stop means is fastened to are chute 5t and maintained in the path of blade 41 during closing of interrupter 1'0. Stop 60 prevents auxiliary blade 41 from entering arc chute passage way 51 until main blade 28 has engaged break tongue 34, as will be subsequently more fully described.

Load interrupter 10 opens in a conventional manner, as follows: i V

Asshown in FIGURE 1, the load interrupter 10 is in its normal closed position with the main switch blade 28 in engagement with its main contact tongue 34 and with the auxiliary switch blade 41 being received between biased contacts 52 in arc chute 50. When it is desired to interruptthe circuit protected by load interrupter 10, switch blade 28 is moved by an appropriate actuating means (not shown) in a direction to move the main blade clockwise-about hinge 24, therebymoving the blade 28 from the position shown in FIGURE 1 to that shown in FIGURE 3. This rotation separates main blade 28 from contact tongue 34. Auxiliary blade 41 is held in its closed position by the biasing effect of contacts 52. Thus, auxiliary blade 41 will be angularly separated from main blade 28 about pivot 43. This angular separation between the blades serves to load torsion spring 44, thereby urging aux- 5 iliary blade 41 out of engagement with bias contacts 52 andin a substantially parallelposition with respect to main blade 28. Disengagement of'the auxiliary blade 41 is effected when main blade 2.8 has been sufficien-tly removed from its associated contact to preyentthetstriking of an arc therebetween'upon the opening of the circuit; During the .trip position shown in FIGURE 3- whereinmain blade 28 is disengaged from its contact tongue 34, a current path is provided between terminals 22 and '33 via auxiliary blade 41 and contact means 52; Whenmain blade 28 has been sufliciently separated from stationary contact tongue 34, auxiliary blade 4,1is rapidly disengaged from contact 52 by virtue of loadedspring member 44. Therapid movement of auxiliaryablade 41' through the arc chute 5! acts to extinguish any are formed due to the separation of auxiliary blade 41 from contacts 52. It will be noted that stop means 60 is disposed in the path of movement of auxiliary blade 41. While stop means 60, which is a flexible member, is preferably biased. in the direction shown by arrow'70, its flexible characteristic offers little resistance to the movement of auxiliary blade 41 during disengagement of the switch,

The operation thus far described is in many respects conventional, whereby an auxiliary blade contact disposed in an arc chute servesto rapidly disconnect the load interrupter from the circuit. My invention, as will be subsequently set forth, is more specifically directed to the manner of closing such a switch, whereby the auxiliary blade 41 is kept out of arc chute 50 until electrical contact has been, made. between main blade 28 and its contact tongue 34. In the heretofore practiced operation of such load break switches, main break blade 28 is moved in a counterclockwise direction from its open position shown in FIGURE 4. Projection 3,9 which preferably includes a ball-shaped tip, makes first contact with main blade 28; Contact 39 is appropriately positioned with respect to auxiliary contacts 52such that, electrical contact is made by the main blade 28, prior to electrical contact being made-by the auxiliary blade 41. However, it will be noted that should the mainandauxiliary blades remain'in their substantially parallel relationship during switch closing, auxiliary blade 41 will be disposed within arc chute passageway 51 prior to engagement of the main blade. It has been found that although the auxiliary blade, contact is not made before the main contact, decreased resistance within the arc chute caused by priorarcing permits a break-down from the auxiliaryblade 41 to its: contacts 52 before the main contacts are made. Once such arcing takes place, the condition of the arcing chamber rapidly d rates a sin ddeteflcu d p it h h ha e n found to reduce the number of successful switch operations from 120 to less than 25 To thereby avoid this deleterious etfect, my invention keeps auxiliary blade 41 completelyout of arc chute pass'ag'eway 51 until contact has been made between main blade 28 and its contact tongue 34. Once themaincontact the torsional loading of spring 44, such that auxiliary blade 41 will be released from stop means.60,u'PQ engagement of mainblade 28and'contact tongue 34. Upon such engagement spring 44 is rapidly unloaded, thereby snapping auxiliary blade 41 rapidly through arc chute pas: sageway 51 and into engagement with auxiliary contacts 52;.

Stop means 60 is preferably biased to act as an impediment in the path of auxiliary blade 41 during closing pe a ion onl As shown in FIGURES 6 and 6 a, stop means (it); is typically shown comprising a, rigid rod 71 connected to a flexible flipper-like strap 72 That is, during the closing ope at l r end 1 o a lia y ade 41-wi11e ga the r t p pin e 71,, t ereby e t ng do n gai t the top surface of the arc chute to maintain the stop in its obstructing position. During the opening' operatio'n of the switch, upper surface 46 forcefully strikes the bottom of obstructing member 71, thereby rapidly moving. it-out st rs rats. afmp mentdu me flex bili y f str pfiz.

Both

sides

53 and 54 forming the arc chute are -pro-' vided with ledges 81 (see FIGURE 1) upon which the strap 72is seated. In addition thereto, each side 53- and 54 is provided, with notches {Band 84 respectively which cooperate to form an opening for receiving the end of strap 72 (see FIGURE '11-). The, stop meansiis held in place by. a cotter pin 85 inserted through aperture 73 in strap 72 which aperture extends beyond the leftv side of the arc chute.

Referenceis now made to FIGURES 7l(),wh'i ch illustrate a preferred embodiment of the pivotal engagement between the auxiliary and main blades to provide biasing of the auxiliary blade as it deflected either upward. or downward with respect to its norm-a1v position parallel to main blade 28. Torsion spring 44 is disposed about R ve m nt and 9P1 T Y Y m Q d o end 42 of the auxiliary blade to provide the aforesaid biasing. Spring stop includes surf-

aces

76 and 7,7 which appropriately interact with spring 44 and blade'end, 4 2-to provide the proper amount of spring biasing. Referring first to the operation operationduring opening, auxiliary blade will be retained. in the position shown FIGURE, 7 by the biasing of contacts 52. Upon movement of main blade 28 surface 42 of auxiliaryib ia e 41 will gage end 44 of spring 44, causing it to be forced up ward. The other end 44'. of spring 44 be held against rotation by the projection 76of-step mern bertei.

ha be t ma e the. b as s iiterccznn e n f h m in and I auxiliary blades at pivot 43 rapidly moves the auxiliary blade through the are chute into firm engagement with qen sfil- The operation during closing may best be understood by referring-to FIGURE 5, which illustrates the switch in anint mediate position during closing. Stop means 60, app pr tely'conuected to are chute 50, is p'ositioned'in thepazthflof auxiliary blade ll-during the" closing operation. Hence, it is seen that as main blade 28 is moved counterclockwise towards engagement with its contact tongue 34, stop means prevents associated movement of a uxil'iary" blade 41, thereby angularly 'Yseparating' the blades. Biased pivot 43 is preferably arranged, as will be more fully set forth in conjunctionwith'FIGUREI6, to urge auxiliary blade 41 towards its contact SZI. As the angular separation between the blades increases, the tor sional loading of spring 44 similarly increases. Auxiliary blade end 45 is approximately shaped in conjunction'with When the proper angular displacement of the maintblade; 28 occurs from its contact tongue 34,hook portion 717, of stop 45, engaged auxiliary blade and 4 2. therelby pre yenting further angular separation of the auxiliary. and main blades' Auxiliary blade 4 1 is then pulled out of engagementwith contacts 52, with spr-ing 44lrapidly, un loading to provide quick disengagement:

During closing of the switch, movement of auxiliary blade 41 is temporarily restrained by stop 60, witlfend 42 engaging spring end 44". Projection 76; of spring, S embe 5 n a nd 44' o a i a 4? (S e'FIG UR he eby ca s n spr g 44 to bel edl As the ng l e a at n a e wirespend o the I gagement of 'main blade and contact .3;4', tl 1e torsional loading of spring member 4 4 correspondingly increases until auxiliary blade 41 fin-al-ly slips from stop 6i); To;r sio'rial spring 44 is rapidly u'n'l oad-ed, thereby "providing a quicksnap action of auxiliary blade 41 througharc chute passageway 51 and into finm engagement with bias contacts 52; i Spring 44, is preferably preloaded corresponding to thenormal position-of the auxiliary and main blades in their substantially parallel relationship to thereby ininirnize rebounding ofthe blade when it is snapped. towards its normal position from either its closed or temporarily restrained position.

It is therefore seen that I have provided an improved load brea'k interrupter switch, wherein the auxiliary blade is prevented from entering the arc chute during the closing operation until engagement has been made by the main contact blade. Such a structure prevents arcing between the auxiliary blade and its contact during the closing operation, and has been found to provide an appreciable increase in the number of operations of the switch.

Although the present invention has been set forth in conjunction with a preferred embodiment, it is naturally understood'that many variations and modifications will now become apparent to those skilled in the art, as for example, the biased pivotal engagement of the main and auxiliary blades may be provided by numerous other arrangements. Likewise, the stop means disposed in the path of the auxiliary blade during closing may take variout other suitable dorms. Accordingly, I prefer not to be limited to the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. In' combinationfir-st and second terminals; main blade means pivotally connected to said first terminal for movement in -a first direction to engage said second terminal, and a second direction to disengage said second terminal; auixiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; stop means comprising a flexible member for restraining the movement of said auxiliary blade means in it first direction during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said. main blade means and said second terminal.

2. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second ter- -r ninal, and a second direction to disengage second terminal; auxiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction. to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; stop means comprisinga flexible member for restraining the movement of said auxiliary blade means in its first direction during movement ort said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade means and said second terminal; first biasing means operatively connected to said main and auxiliary blade means to' urge said auxiliary blade means towards said auxiliary cont-act means during movement of said main blade means in its first direction; said stop means loading said first biasing means; said first biasing means operatively connected to said auxiliary blade means to impart rapid movement of said auxiliary blade means into engagement with said auxiliary contact means upon release from said stop means.

3. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction to disengage said second terminal; auxiliary blade means pivotally mounted to'said iri-airi blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact mean-s operatively positioned to engage said auxiliary blade means; stop means comprising a flexible member for restraining the movement of said auxiliary blade means in its first direction during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade and said second terminal; said flexible member comprising a first rigid portion positioned to obstruct said passageway in the path of said auxiliary blade means.

4. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction to disengage said second terminal; auxiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; stop means comprising a flexible member for restraining the entry of said auxiliary blade means within said passageway during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade means and said second terminal; said flexible member comprising a first rigid portion positioned to obstruct said auxiliary blade means,'and a second flexible portion biasing said first portion towards said obstructing position; said second portion releasably removing said first portion from the path of said auxiliary blade means during movement in its second direction.

5. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction to disengage said second terminal; auxiliary blade means pivotally mounted to said blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; flexible stop means restraining the movement of said auxiliary blade means in its first direction during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade means and said second terminal; means maintaining engagement of said auxiliary blade means and contact means during movement of said main blade means in its second direction, and until a predetermined angular separation is established between saidauxiliary and main blade means; second biasing means operatively connected to said main and auxiliary blade means to urge said auxiliary blade means out of engagement with said auxiliary contact means; said second biasing means operatively connected to said auxiliary blade means to impart rapid disengagement of said contact means. i

6. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction to disengage said second terminal; auxiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage-said auxiliary blade means; flexible stop means restraining the movement of said auxiliary blade means in its first direction during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade means and said second terminal; first biasing means operatively connected to said main and auxiliary blade means to urge said aux-iliary blade means towards said auxiliary contact means during movement of said main blade means in its first direction; said stop means loading said first biasing means; said first biasing means operatively connected to said auxiliary blade means to impart rapid movement of said auxiliary blade means into engagement with said auxiliary means upon release from said stop means; means maintaining engagement of said auxiliary blade means and auxiliary contact means during movement of said main blade means in its second direction, and until a predetermined angular separation is established between said auxiliary and main blade means; second biasing means operatively connected to said main and auxiliary blade means to urge said auxiliary blade means out of engagement with said auxiliary contact means; said second biasing means operatively connected to said auxiliary means to impart rapid disengagement of said contact means; said first and second biasing means comprising a single spring disposed about the pivotal engagement of said main and auxiliary blade means; an end of said spring operatively engaging said auxiliary blade means during relative angular movement of said blade means; spring stop means maintaining the position ofthe opposite spring end, whereby said spring is loaded during said relative angular blade means movement.

7. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction'to disengage said second terminal; auxiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing aux-iliary contact means operatively positioned to engage said auxiliary blade means; flexible stop means restraining the movement of said auxiliary blade means in its first direction during movement of said main blade means into engagement with said second terminal; means ior releasing said auxiliary blade means from said stop means upon engagement of said main blademeans and said second terminal; first biasing means operatively connected to said main and auxiliary blade means to urge said auxiliary blade means towards said auxiliary contact means during movement of said main blade means in its first direction; said stop means loading said first basing means; said first biasing means operatively connected to said auxiliary blade means to impart rapid movement of said auxiliary blade means into engagement with said auxiliary contact means upon release from said stop means; said stop means comprising a first flexible portion connected to said are chute, and a second rigid portion connected to said first portion and positioned to obstruct said passageway in the path of said auxiliary blade means, said first flexible portion releasably removing said second rigid portion from the path of said auxiliary blade means during movement in its second direction.

8. A load-break interrupter switch including: main blade means movable between an open and closed position; an auxiliary switch blade pivoted on said main blade means and movable in a first direction to a closed position and a second direction to an open position, and an arc chute; said are chute comprising first and second arc chute sidewalls defining a passageway for the entry of said auxiliary blade means; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; said are chute including a stop means positioned in the path of said auxiliary blade means; said stop means obstructing the movement of said auxiliary blade means in its first direction while said main blade is moving towards its closed position, said stop means releasing said auxiliary blade means when said main blade has reached its closed position; said stop means comprising a rigid abutment member secured to a flexible flipper; stop biasing means urging said flipper in a direction to present said abutment member in the path of said auxiliary blade means; said stop biasing means operatively connected to said flipper to releasably remove said abutment member from the path of said auxiliary blade means while said main blade means is moving towards its open position.

9. In combination first and second terminals; main blade means pivotally connected to said first terminal for movement in a first direction to engage said second terminal, and a second direction to disengage said second terminal; auxiliary blade means pivotally mounted to said main blade means for movement in a first direction to a closed position and in a second direction to an open position; an arc chute having a passageway for receiving said auxiliary blade means mounted adjacent said second terminal; said passageway containing auxiliary contact means operatively positioned to engage said auxiliary blade means; stop means comprising a flexible member for restraining the movement of said auxiliary blade means in its first direction during movement of said main blade means into engagement with said second terminal; means for releasing said auxiliary blade means from said stop means upon engagement of said main blade means and said second terminal; said stop means comprising a rigid first member; aflexible flipper portion having a first end secured to said rigid first member; said are chute having an aperture for receiving the second end of said flipper portion; pin means extending through said second end of said flipper portion to secure said stop means to said are chute.

References Cited by the Examiner UNITED STATES PATENTS 2,308,026 1/ 1943 'Rawlins 200-62 2,840,671 6/ 1958 Gieifers ZOO-62 X 2,886,663 5/1959 Powell 200-48 3,136,874 6/ 1964 Albright 200-146 X 3,178,543 4/ 1965 Albright et al 20048 ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner. H. B. ODONN-ELL, Assistant Examiner.

Claims

1. IN COMBINATION FIRST AND SECOND TERMINALS; MAIN BLADE MEANS PIVOTALLY CONNECTED TO SAID FIRST TERMINAL FOR MOVEMENT IN A FIRST DIRECTION TO ENGAGE SAID SECOND TERMINAL, AND A SECOND DIRECTION TO DISENGAGE SAID SECOND TERMINAL; AUXILIARY BLADE MEANS PIVOTALLY MOUNTED TO SAID MAIN BLADE MEANS FOR MOVEMENT IN A FIRST DIRECTION TO A CLOSED POSITION AND IN A SECOND DIRECTION TO AN OPEN POSITION; AN ARC CHUTE HAVING A PASSAGEWAY FOR RECEIVING SAID AUXILIARY BLADE MEANS MOUNTED ADJACENT SAID SECOND TERMINAL; SAID PASSAGEWAY CONTAINING AUXILIARY CONTACT MEANS OPERATIVELY POSITIONED TO ENGAGE SAID AUXILIARY BLADE MEANS; STOP MEANS COMPRISING A FLEXIBLE MEMBER FOR RESTRAINING THE MOVEMENT OF SAID AUXILIARY BLADE