US2246072A - Switching mechanism - Google Patents

Description

June 17, 1941. w. M. SCOTT, JR

swrrcnmcuscxmmsm Filed-Jan. 2a, 1939 4 Sheets-Sheet 1 INVENTOR. BY M M D! ATTORNEY.

June 17, 1941.

4 Sheets-Sheet 2 24 I N V EN TOR. 8 4' BY L' 6 M41 25.

A TTORNE Y.

inns 17, w SCOTT JR SWITCHING MECHANISM 4 Sheets-Sheet 3 Filed Jan. 28, 1939 INVENTOR.

A TTORNEY.

June 1941- w. M. SCOTT, JR SWITCHING MEdHANISM 4 Sheets-Sheet 4 Filed Jan. 28

INVENTOR.

M Q4 (2.79M

- ATTORNEY.

Patented June 17, 1941 2,246,072 SWITCHING MECHANISM William M. Scott, Jr., Br

I-T-E Circuit Breake Pa., a'corporation of yn Mawr, Pa., assignor to r Company, Philadelphia, New Jersey Application January 28, 1939, Serial No. 253,426

23 Claims.

My invention relates to circuit-controlling devices, and particularly to electric switches of the type having an operating member for effecting relative movement of the switch contacts and for actuating means for clamping those contacts to tech other in closed-circuit position.

In accordance with one aspect of my invention, there is provided, between the operating member and the movable contact structure, a latch, or

system of latches, constructed and arranged to insure transition from actuation of the movable Contact structure to actuation of said clamping means by said operating member at a definitely predetermined position of the movable contact structure; more particularly, in some forms of my invention. the latch, or latch system, is adapted, upon release of the operating member from he movable contact structure for actuation of the clamping means, to lock the contact struclures against relative movement until the operating member is relocked to the movable contact structure for moving it away from the fixed contact structure.

Furthermore in some forms of my invention,

there is provided cam structure which positively prevents actuation of the latch for release of the operating member from the movable contact structure except when the contacts are in closedcircuit position.

My invention further resides in the features of construction. combination and arrangement hereinafter described and claimed.

For an understanding of my invention, and for illustration of some of the various forms it may take, reference is to be had to the accompanying drawings, in which:

Fig. 1 is a side elevational closed-circuit position; I Fig. 2 is a front elevational view of the switch of Fig. 1; I

Fig. 3 is a side elevational view, partly in seclion and with parts brokenaway, of the switch of Fig. 1;

Fig. 4. in perspective, and on enlarged scale,

view of a switch in shows latch structure appearing in Figs. 2 and 3;

Fig. 5 is a side'elevational view, in section, showing the relation between parts appearing in Fi 3 for open-circuit position of the switch;

Fig. 6. in perspective, illustrates several switches, of the type shown in Figs. 1 to 5, mechanically connected for simultaneous operation;

Fig. 7 is a side elevational view, partly in section, of a modification of the switch shown in F gs. 1 to 5;

Figs. 8 and 9 are side elevational' views, partly in section, showing parts appearing in Fig. 7 in cl'fierent operative relations;

Fig. 10 is a fragmentary side elevational view, partly in section, of a modification of the switch shown in Figs. 7 to 9;

v Fig. 11 is a side elevational view, partly in section, of a modification of the switch shown in Figs. 7 to 9;

Fig. 12 is a front elevational view of the switch of Fig. 11 with parts omitted or broken away;

Fig. 13 is a side elevational view of a modified form of contact structure, which may be substituted for the movable contact structure of any of the switches of Figs. 1 to 12;

Fig. 14. in perspective, illustrates another modi: fication of the movable contact structure of Figs. 1 to 12; g

Figs. 15 and 16 are sectional views taken on lines l5-l5 and Iii-I6 of Fig. 1;

Fig. 17 is a plan view of an element shown in r Figs. 15 and 16.

Referring to Figs. 1 to 5, the switch S coniprises the fixed contacts or terminals I, 2 suitably mounted upon insulators 3, 4 attached at their bases to the housing or support 5. For connection with bus bars, the contacts I, 2 are provided with extensions 6 to which the bus bars may be clamped by bolts passing through the holes 7'. The movable contact structure for completing connection between the contacts or terminals 'l, 2 comprises the contact members or blades 8L, 8R, slotted at their contacting ends and pivotaljly mounted upon the contact 2 as by the pin 9. The clamping bars IOL, IOR which overlie and extend lengthwise of the movable contact members 8L, 8R threadably receive intermediate their ends, directly or by nuts adjustably clamped thereto, the oppositely threaded ends'of pin II which extends through the contact members 8L, BR and which, between these contact members, passes through the hub 12 of an operating member or arm 13. In the particular construction shown, the central portion of the pin I I is square in cross-section to fit the bore of hub l2 which is of similar cross-section; any other arrangement providing for rotation of the pin II with arm 13 about the axis of pin H as a pivotal axis may beutilized.

The threads at the opposite ends of the pin I I are respectively left and right-hand. threads, so that upon coimterclockwise rotation of'arm l3 about its pivotal axis to the position shown in Figs. 1 and 3, the clamping bars IDL, 'I'OR are drawn towardieach other, to clamp the movable contact blades 8L, 8R against the fixed contacts 2 2,246,072 l, 2. Alternatively, the pin H may be threaded and immediately to swing the hooked end 24 of only at one end, the urlthreaded end having a the latch 20 clear of the rollers la. The remotehead or shpulder bearing against the associated ness from the pivot pin 9 of the point of engageclamping bar. counterclockwise or contactment between the fixed stop or abutment 23 and clamping movement of arm l3 about its pivot ll, 5 the latch element 22, and the relatively reverse that is, with respect to the movabl nt ct directions of movement or the latch and. the

structure, may be limited, as by provision of arms movable contact structure about their respective ll attached to or integral with hub ll, Figs. 1 ots upon en a m t o st p 13 y latch e and 3, and engageable by stop pin is extending ment 22, cumulatively insure'tliat, for successive between the movable contact members L, R, operations 0f the switch, the transition from The clamping and unclamping move t f contact-movement to contact-clamping by arm I3 arm 13 may b eflected by 1m]; 15 ot u occurs always at a definitely predetermined cirt d t th free end of arm t3, as by m n, cult-closing position of the movable contact and extending between t contact, blades structure 8L, 8R, thus to insure always a definite BR, between the insul to 3, 4 and through t 15 area 0! engagement between the switch contacts base or housing member 5. when the switch is closed; the definiteness of the wh arm i3 1 i t position shown in i transition point also insures that for successive 1 and 3 for which t t t are clamped m operations of the switch a predetermined desired closed-circuit position, it is free of the latch 20, act pressure always obtains p n m vement which as hereinafter described, locks the arm to of arm to its extreme and limited position o the movable contact blades for their movement F185- 1 and This transition Point is tertoward and from closed-circuit position. Latch mined with ninety y ad us ment or element 22 n is pjvotally mounted upon m 2| extending with respect to latch 20 which carries it; in the between the movable contact blades on, on, re particular construction shown in Fi 1 to 5, elet from plvet pin 9 25 ment 22 is threadably received by extension 25 of eleekwise dh-eehon latch 20 and is locked in adjusted position by nut about its pivot pin H fro the position shown in I 26. Preferably the latch 20 is biased to its arm- Figs. 1 and 3 to reduce the pressure between the Positmn, 1 as by Spring which fixed and movable contact structures. the rollers may he coiled about Pi Pin 2 with its ends l8 carried by arm l3 finally engagethe surfaces in engagement. p ctiv ly. w th the latch 20 and l9 0! latch 20, and upon continued movement in amresaid Stop bar W on the m vable contact clockwise direction eflects counterclockwise movestructurement (now reversed with respect to the clock- Each of the Switch units 52 of the multiw movement of t t structure 3 pole switch of Fig. 6 is similar to the switch of latch20 about its pivot 2|. Because of ensage- Figs- 1 t0 5; their Operating links 15 extend into ment between the element 11 attached to or part the housings 5 for connection therein, beyond or of the latch 20, and the abutment or nxcd stop behind the plane f upp rt of the contact strucz3 Suitably attached t the stationtures, with arms (not shown) connected to the ary contact structure I, this reverse or counter- W905i ends 01 Shaft 8 o which is suitclockwise 'movernent of the latch about its pivot 40 ably attached an arm 29 Pivotally c nneo ed to a 2| is accompanied by, and in tact eflects movelink a which may be p a d manually, or by ment of the movable contact structure in clockany suitable motor device. to p n or close the wise u about its pivot, pm 9 Bri fly switches. The particular units illustrated in Figs. restated, the continued clockwise movement of 1 6 will serve vy du y outd or service as arm 3 fr m the position of Fig 3 first ffect disconnect switches for bus bars. The thin sheetreduehen releese of the contaehelampmg metal members 3i extending outwardly from each ht with latch oi the upper fixed contacts i serve as weather pressure and then, upon engageme 20, by icontinued movement, coacts with the guards Petticoat shleldslatch m and abutment 23 to move and my the In the modified form of switch shown in Figs. movable contact structure 8L, m rrom the posito 9/0118 latch A. n rally correspondin with tion shown in Figs. 1 and 3. The counterclocklatch in of 8 1 t0 5, has n i ns 32 along wise movement f latch g about its pivot 2|, and whose arcuate faces the rollers I8 on arm l3 ride now moving with blades 8L. 8B. in clockwise dias the arm mOVed and fr m its contactrection about pivot 9, also causes the hooked end clamping Position With latch 20A 24 f the latch Fig. 4, quickly and immediately in the position shown in Fig. '7, the center of the to drop over the roll la eh arm 13 and so leek radii of curvature of the arcuate faces of extenarm l3 to the movable contact structure with the $10115 substantially corresponds with the p result that both the arm and the contact strucotal axis of the arm h the result that am ure move as a unit about the pivot pm 9, upon I3 throughout its actuation of the clamping further movement oi. link ii to the right, as means the latch 20A n p si ion shown in viewed in Figs. 1, 3 and 5, to the full open-circuit Fillwith, during oi g movement or the position. arm, its rollers l8 engage the faces is or the Arm i3 remains latched to the movable contact latch to initiate u -openi g m vement Structure during reverse or ehcmhclesmg oi the movable contacts 8L, 8R. Throughout the movement until just before the movable contact 65 engagement of arm B w th the extension 32 or structure again reaches the closed-circuit posilatch t the Shoulder 33 0f lat-ch 20A 1 t shown in 1 1 and 3 t hi t t ates with the stationary abutment 34 170 100k the abutment 23 is engaged hythe step 11 of the movable contactstructure to the flared contact latch 50 that, for the now slight additional move- Structurement in counterclockwise direction of the mova- '0 p n movement ofv arm l3 in clockwise or unble contact structure to definitely predetermined clamping direction f m p n shown in closed-circuit position, the latch 20 is rotated Fig. '1, the clockwise rotation of e threaded pivot about its pivot 2| in clockwise (reversed with p n ll fi s ff ts un l o n f th contacts. respect to the counter-clockwise movement or and then, upon continued movement or arm l3 the contact structure 8R, 8L) direction quickly in the same direction; it engages the surfaces i9 0! the latch 28A to rock the latch 20A in reverse or counterclockwise direction to release the latch from the stationary abutment 34, thus releasing the movable contact structure from locking engagement with the fixed contact structure, substantially concurrently to effect locking engagement between the latch 20A and the arm I 3, and, by coaction between the abutment 23 and the latch element 22, to initiate movement of the movable contactlstructure from its closed-circuit position even before the arm I3 is fully latched.

Switches of this type are usually either installed with the base 5A vertical, as in Figs. '7 and :8, or with the base 5A horizontal with the supporting insulators 3, 4 and the switch structure depending therefrom. In both cases, the weight of arm I 3A biases it to unclamping position.

To avoid unintentional reduction of the contact pressure and possible subsequent opening of the switch, the arm 3A, an extension of arm I3, is provided with a pivoted latch 35 which, when the arm |3A is in the position shown in Fig. '7, looks the arm I3A' to the stationary contact structure by engagement with the notched element 38. .The latching of the operating arm |3A in this position is particularly desirable in installations where the switch is subjected to continued vibration tending to cause the arm |3A to move in the unclamping direction, so reducing the contact pressure with possible injury to the contacts.

Preferably the latch 35 is extended to comprise one element of the eye E so that when the end of a hook stick is-inserted in the eye for opening the switch, the initial movement 01' the hook stick rocks the latch against the bias of its spring 35A to release the arm |3A from stationary member 36. Further movement of the hook stick first effects unclamping of the contacts by clockwise movement of arm I3 about its pivot II, and then, upon latching of the arm to the movable contact structure, effects movement or the movable contact structure with the arm |3A from the closed-circuit to the open-circuit'position.

To close the switch from the open-circuit position, Fig. 8, the arm |3A is pushed upwardly, by a hook stick, and because the arm, at this time, is locked by latch 20A to the movable contact structure the arm and the contact structure pivot as a unit about the pin 9. Just before the movable contact structure reaches its dual circuit-closing position, the latch element 22 engages, remote from the pivot 9, the fixed abutment 23, so that for continued movement of the contact structure in counterclockwise direction, the latch 20A, because of engagement with abutment 23, swings about its pivot 2| in reverse or clockwise direction to release the arm l3 ior contact-clampingmovement about its pivot 2| with respect to the movabie'contact structure, and substantially concurrently to lock the movable contact structure to the fixed contact structure, thus insuring always a definite closed-circuit position of the movable contact structure whenever it is released from the arm l3 for actuation, by arm I 3, of the contact-clamping means.

In this modification also, the remoteness from the pivot pin 9 of the point of engagement between the abutment 23 and the latch element 22, and the reverse movements of the latch and the movable contact structure about their respective pivots upon engagement of stop 23 and latch element 22, cumulatively insure that for successive operations of the switch the transition from contact movement to contactclamping occurs predetermined position suitable adjustment of always at a definite and which may be varied by element 22 with respect carries it.

With the construction as thus for described, the latch 20A can be released, accidentally or by tampering, when the switch is in the open-circuit position, thus making possible movement of arm |3A with respect to the movable contact structure to change the position of the clamping bars with consequence that if the switch is thereafter closed, the contact pressure may be either insufllcient or excessive.

Positively to lock the latch in engagement with the arm 13A to prevent actuation of the contactclamping means at all timesexcept when the movable contact structure is in closed-circuit position, there is provided a cam 31, which may be adjacent pivot 9, having an arcuate surface 33 whose center of curvature substantially coincides with the axis of 38 engages roller 39 attached to one end of an arm 40 loosely mounted upon pin and whose other end remains in looking engagement with the extension 4| of latch 20A throughout movement of the contact structure toward and from its closed-circuit position. Substantially concurrently with, or immediately before, engagement of abutment 23 by the latch element 22, the roller 39 abruptly rides oil? the arcuate surface 38 of cam 31, Fig. 9, to permit clockwise movement of latch 20A about its pivot 2|.

Substantially concurrently with actuation of latch 20A for release of the movable contact structure for movement from the closed-circuit position, the roller 39 on arm 40 rides up on the cam 31 to its arcuate surface 38; substantially concurrently latch 20A relocks arm l3 to the movable contact structure, the coacting with extension 4| of the latch arm .40 to preclude relative movement between the arm ISA and the movable contact structure until the movable contact structure is closed-circuit position.

In the modification shown in Figs. 7 to 9, it is not necessary to provide any biasing means for the latch 20A because all its movements are positively effected.

In the modification, shown in Fig. 10, similar to that of Figs. 7 to 9, except for omission of cam 3! and arm 40, the latch 20A is biased toward engagement with the rollers 8 on arm |3A by the spring 21A; operation of this modificationis apparent from explanation of the operation of Figs. 7 to 9.

The modification shown in Figs. 11 and 12 is similar to that of preceding figures except for the particular latching arrangement between the operating arm l3 and the movable contact structure 8L, 8R. The latch 20B is similar to latch 20A, Fig. 7, except that the latch element 22, Fig. 7, for engaging the abutment 23 is replaced by a second latch 42, Fig. 11, plvotally mounted upon pin 43 extending between the two side members of' latch 20B and having an extension or roller 22A for engaging abutment 23. To provide for over-center snap action of the latch 42, there is provided the pin 44 slidable in a recess in the latch and biased by spring 45 within the recess against pivot pin 2| of latch 20B. Movement of snap-latch 42 in clockwise direction about its pivot 43 is limited by the adjustable stop 46 01' the main latch 20B. Movement in the reverse direction of the latch 42 about its pivot 43 is again returned to to the, latch 20A which the pivot pin 9. Surfacecamsurface 38 4- 2,246,072 limited by engagement between the tall 41 of member 50 should be equivalent to a ball and the latch and the pivot 2! of the main latch.- socket, or other equivalent term of universal Upon movement of the contact structure and joint or connection. the operating arm toward the position shown in Preferably, the fingers are provided with in- Fig. 11, the fixed abutment 23 first engages the u serts 54 of hardened steel or equivalent for enroller 22A of the snap-latch 42, whereupon for gagement by the pressure-applying ends of the slight further movement of the movable contact plates 53.

structure, the snap-latch 42 quickly moves to the The modified forms of movable contact strucpositionshown in Fig. 11, to release the arm l3, tures shown in Figs. 13 and 14 may be substituted the engagement between latch 42 and the stop for the simpler form of digitate contacts 8L, BR, 46 of the main latch 20B causing the main latch shown in Figs. 1 to 12.

to swing about its pivot 2 l. to bring its abutment In the switches of Figs. 1 to 13, instead of using 33 behind the stationary abutment 34 to lock the hardened inserts, as in Fig. 14, hardened steel movable contact structure to the fixed structure discs 55 may be interposed between the adjustand concurrently to release the arm I3 for its ing screws 50 and the copper contact structure actuation of the clamping means.v Throughout 8R, 8L.

the movement of the arm t3 from the position As shown inFig. l5, the lower end of the clampat which it is initially released from the latches ing bar IUL (bar IDL is identical with bar IDE for actuation of the clamping means, and until it except for reverse threading of the clamping returns to position relocking the arm l3 to the screw hole) is recessed to receive a pair of free movable contact structure, the rollers I8 on the discs 55, each substantially greater in diameter end of arm l3 contact the arcuate surfaces of the than the end of screw 50 which presses it against extensions 32 of the latch 20B to lock the latch one of the fingers oi movable contact 8L. Prefer- ZIIB in the position shown in Fig. 11, for which it ably each disc 55 is prevented from rotation duris efiective to prevent relative movement of the ing adjustment of the associated screw 50, as by fixed and movable contacts of the switch. an extension 55 which fits a corresponding slot In both modifications, Figs. '7 to 9, and 11, 12, or keyway .51 in the underface of the clamping there are preferably provided the spring buffers bar.

48, 48 secured to the lower contact member 2 As shown in Fig. 16, at the other end of the between the movable contact blades 8L, 8B for clamping bar IOL of Fig. 15, a similar arrangeengaging the pins 49, or equivalent, projecting inment is employed; in the keyways 51A in 10L are wardly from the inner faces of the contact blades. disposed the keys 56 to prevent rotation of the Each of the yielding stops or buffers 48 preferably free discs 55 during adj stment of their assocomprises a plurality of spring members, of prociated pressure-adjusting screws 50.

gressively increasing lengths suitably held, as by To maintain proper or desired alignment of the bolt 49, against an inner face of the contact clamping bar IOL with respect to the associated member 2 movable contact 8L, the bar is provided at its Each otthe movable contact blades of Figs. 1 lower end, as viewed in Fig. 1, h a ho e 53 to 14 is slotted, as indicated at S, at their opposite in which loosely fits, Fig. 15. the end 9A, of reends to provide separate fingers between each or duced diameter, of the pivot pin and its upper end,

which and the clamping bar is interposed an as viewed in Fig. 1. is provided with a threaded adjustable element. Referring, for example, to hole 58A into which is screwed an aligning pin Figs. 1 and 2, the upper and lower ends of the 59, Fig. 16, which slidably fits a hole in the upper clamping bar IOL extend over the split or slotted end of the movable contact structure. ends of the contact member 8L; the four pins 50 The various switch constructions herein illuswhich threadably pass through the four exten- Hated d des bed are exemplary of my invenslons 5! of the clamping bar lOL are individually tion whose scope is coextensive with the appended adjustable to provide for the desired substanclaims. I tlally equal distribution of the total pressure ap- What I claimis: v plied by the clamping bar to the four contact 1. A switch comprising fixed contact structure, fingers, and are held in their adjusted position, contact structure movable into ,and; out or enas by lock nuts 52. gagement therewith, an operating arm pivotally In the modification shown in Fig. 13, the movmounted onsaid movable contact structure,'means able contact member 8 is provided at each end operated y e t of Said arm in one direcwith three contact fingers or elements, and the tion about -'p v 't 'c mp said Contact strucclamping bar in is correspondingly modified so tures in closed circuit position. a latch movable that each of the extensions or pressure-appl i with said movable contactstructure and disnelements 5|A overlies one of the fingers; with gea y onnect ng it tosaid arm topreclude aceach of the extensions is associated an adjustabl tuation of saidclamping meanscand an abutment. pin 50 to provide for the desired distribution of 60 for engagingsaid latch to release said arm for its pressure between the individual fingers of this pivota movement in said one direction u digitate contact member. Preferably, the extenmovement of said movable contact structure to sions or elements 5IA have substantially similar predetermined closed circuit position and for coload-defiection characteristics. operating with said latch upon subsequent reverse In the modifi ation of t bl t t movement of said arm toinitiate movement of said structure of Fig. 14, the contact SA has slotsat movable Contact structure from said p d terone or both ends to provide four contact fingers ned c osed circuit position. a

or digits; the clamping bar "3 is th same 2. A switch comprising fixed contact structure, figurati n shown in Figs, 1 t 12; b t ith h contact structure movable into and out of engageof the two individually adjustable pressure disment therewith. an operating arm pivotally trimming members 5o at each end f the bar, mounted on said movable contact struciuremeaus there is associated an equalizing plate or saddle p d y movement of said arm in one dire 53 which bridges the slot between an adjacent tion about its pivot to Clamp d Contact strucpair of fingers The connection between each tures in closed circuit'position, a latch movable equalizing plate 53 and its associated adjustabl 5 with said movable contact structure and disengageably connecting it to said arm to precludd actuation of said clamping means, and an abutmovement thereof in one direction about its pivot, subsequent reverse movement of said arm effecting upon its reengagement with said latch coaction between said latch and said abutment to move said contact structure from said position concurrently with resetting of said latch.

4. A switch comprising fixed contact structure, contact structure movable into and out of engagement with said fixed contact structure, an operating arm pivotally mounted on said movable contact structure, a latch movable with said movable contact structure for preventing said arm from moving about its axis during movement of said movable contact toward and from engagement with said fixed contact structure and for preventing movement of said movable contact structure from engagement with said fixed contact structure while said arm is free for movement about its axis, and an abutment engaged by said latch upon movement of said movable contact structure to closed circuit position for actuating said latch to release said arm for movement about its axis and substantially concurrently to latch said movable contact structure in said closed circuit position.

5. A switch comprising fixed contact'structure, contact structure movable into and out of engage ment with said fixed contact structure, an operating arm pivotally mounted on said movable contact structure, a latch movable with said movable contact structure for preventing said arm from moving about its axis during movement'ot said movable contact toward and from engagement with said fixed contact structure, and an tact structure in said position, said arm upon subsequent reverse movement reengaging said latch to release said movable contact structure, to relatch said arm to said contact structure, and by coaction of said abutment to pry said movable contact structure from said position.

6. A switch comprising fixed contact structure, contact structure movable into and out of engagement therewith, an operating arm, means actuated by said arm during its movement in a range thereof to determine the pressure between said contact structures, and latching means cooperative with said arm to lock said contact struc- ;ures in engagement for movement of said arm n said range and to effect movement of said novable contact structure for another range of novement of said arm.

7. A switch comprising fixed contact structure,

contact structure movable into and out of engagement therewith, an operating arm, means structures in closed clamping means by said arm.

8, A switch comprising movable contact structure, an operating arm, latch structure for holding said arm to said movable contact structure for of its circuit-controlling Position. 9. A switch comprising movable contact structure, an operating arm, latch structure for holdpositions of said contact structure.

11. A switch comprising fixed and movable conclamping said strucclosed circuit position.

12. A switch comprising pivotally mounted contact structure, an operating arm pivotally mounted reverse actuation Of said arm to hold said contact structure in cuit position.

13. A switch comprising movable contact structure, fixed contact structure, an operating arm, a latch on said movable contact structure having an arcuate surface engaging with said arm to hold said contact structures in engagement, and a second latch for locking said arm to said movable contact structure upon release of said first latch.

14. A switch comprising fixed and movable. contact structures, an operating arm, a pair of latches on said movable contact structure, and an abutment for engaging one of said latches to release said arm from said movable .contact structure and substantially concurrently to effect actuation. of the other latch to lock said contact structures in engagement. I

15. A switch comprising fixed and movable contact structures, an operating arm, a latch on said movable contact structure for locking it to said closedcirfixed contact structure, an over-center-snap latch on said first-named latch, and an abutment engaging said snap latch substantially upon completion of circuit-closing movement of said movable contact structure movable contact structure for further movement of said arm and to set said first-named latch, said arm upon reverse movement releasing, said firstnamed latch and resetting the snap latch.

16. A switch comprising fixed contact structure, digitate contact structure movable into, en agement therewith, and means for clamping saidcontact structures to each other in closed circuit position comprising a bar overlying said movable contact structure,and individually adjustable members from said bar to different for transmitting pressure elements of said digitate contact structure.

17. A switch comprising fixed contact structures, movable contact structurev pivotally mounted on one of said fixed contact structures for movement into engagement with the other of said fixed contact structures and slotted at both ends to form contact fingers, a clamping bar extending along said movable contact structure to overlie the slotted ends thereof, means for applying a clamping pressure to said bar intermediate the ends thereof, and means for transmitting and dis tributing the pressure applied to said bar comprising individually adjustable members, at each of the opposite ends of said tween said bar and the different contact fingers;

1 8. A switch comprising fixed contacts, movable contact blades pivotally mounted on one of said fixed contacts, and yielding stop structure mounted on said one of said fixed contacts between the blades for limiting thereof.

19. A switch comprising fixed and movable contact structures one of which is divided to proto release said arm from said bar, interposed bethe circuit opening movement vide elements for engagement with the other contactstructure, and means for clamping said contact structures to each other comprising a member divided to provide elements of substantially similar load-deflection characteristics respectively overlying said first-named elements, and an individually adjustable pressure-transmitting member between each of said first-named elements and its associated second-named element.

20. A switch comprising a fixed contact, a movable contact slotted to provide elements for engagementwith said fixed contact, a clamping bar, rotatably adjustable members carried by said bar for transmission of pressure to said elements, and hard non-rotatable elements interposed between each of said members and one of said elements.

21. A switch comprising fixed contact strut)- ture, pivotally mounted contact members, an operating arm for moving said members into engagement with said fixed contact structure, a threaded member connecting said arm to said contact members and rotatable by said arm to clamp said members to and unclamp them from said fixed contact structure, control means precluding rotation of said threaded member by said arm during movement of said contact members toward and from said fixed contact structure and permitting rotation of said member by said arm when said contact members are in engagement with said fixed contact structure, a stationary latching member, and a coacting latching member movable with said arm engaging said stationary latching member substantially upon completion of the contact-clamping rotation of said threaded member to hold said arm in fixed contact-clamping position. i

. 22. A switch comprising fixed contact structure, movable contact structure, means for clamping said contact structures to each other, an operating' member for eifecting movement of said movable contact structure toward and from engagement with said fixed contact structure, cam structure coacting with said operating member to preclude its actuation of said clamping means during movement of said movable contact structure toward or from said fixed contact structure, and latching means for engaging and holding said cperating member substantially upon completion of its actuation of said clamping means.

23. Aswitch comprising fixed contact structure. movable contact structure for engaging said fixed contact structure comprising independently flexible elements arranged side by side, and means for clamping said contact structures to each other in closed circuit position comprising a bar overlying said elements and determining the pressures between each of said individual elements and said fixed contact structure.

M. SCO'I'I. JR.

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