US2409472A

US2409472A - Electric switch

Info

Publication number: US2409472A
Application number: US489021A
Authority: US
Inventors: Butler William Lawrence
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1943-05-29
Filing date: 1943-05-29
Publication date: 1946-10-15
Anticipated expiration: 1963-10-15

Description

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ELECTRIC SWITCH Filed May 2.9, 1943 2 Sheets-Sheet l -Y Fig' i "1' /A MMA w Av n.,

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Oct. 15, 1946. w41.. BUTLER 2,409,472

ELECTRIG swITcH Inventor: Wliiam Lawrence Butler;

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Patented Oct. 15, 1946 ELECTRIC SWITCH William Lawrence Butler, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application May 29,A 1943, Serial No. 489,021

8 Claims.

My invention relates to electric switches, more pariicularly to switches especially designed to maintain a desired circuit-opening or circuitclosing position when subjected to severe vibration or the shock of sudden impact. The invention is particularly applicable to control switches of relatively small capacity, such as limit switches, selector switches, and the like.

The principal object of my invention is to Drovide a new and improved simple, dependable and inexpensive electric switch of the shock-proof ype.

It is a further object of my invention to provide a switch contact structure arranged to minimize contact bouncing upon subjection to severe vibration or impact shock.

It is a still further object of my invention to provide a switch contact structure arranged to minimize relative sliding movement of the contacts upon vibration thereof in engaging position.

It is still another object of my invention to provide an electric switch contact structure arranged to minimize local Contact Vibration in response to impact shock.

rline new and novel features of my invention will be pointed out with particularity in the claims appended to this specification. For a more complete understanding of the invention and a further appreciation of its objects and advantages, reference should now he had to the following detailed description taken in conjunction with the accompanying drawings in which Fig. 1 is a plan view oi an electric switch embodying my invention, the cover being partly broken away to illustrate the switch structure; Fig. 2 is a crosssectional view taken along the line 2 2 of Fig. l; Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. l; Fig. 4 is an exploded perspective View of certain parts of the switch operating mechanism; Fig. 5 is an end elevation of the switch contact assembly; and Figs. 6 and 'I are detailed views of certain portions of the switch actuating mechanism.

Referring now to the drawings, I have shown my invention by way of illustration as applied to an electric limit switch mounted in a casing I0 having a cooperating cover II. To render the switch weatherproof, the cover II is preferably bolted to the casing and a gasket I2, of rubbery or the like material, is provided therebetween. In general, the switch comprises a contact as.- scmbly mounted upon a suitable base I3, a switch actuating arm It pivotally mounted upon a pair of upright bosses or pillars I5 and |509 integrally formed interiorly of the casing I0, and an operating shaft IE pivotally mounted in the sides of the casing and carrying interiorly of the casing an actuating cam 22 and exteriorly of the casing an operating lever I8. rIhe contact base I3 is preferably formed of molded plastic insulating material and is bolted inside the casing I0 at the end opposite the operating shaft I6.

Referring first to the switch operating mechanism, the operating shaft I6 is pivotally mounted in a pair of bearing'bosses i9 and 29 formed 'in opposite walls of the casing IE). The shaft I6 extends through one wall of the casing and carries on its outer end the operating lever I8 upon the end of which is mounted a roller 2| for engagement with any movable member whose motion it is desired to limit. Interiorly of the casing ID and between the upright pillars I5 and I5@ the operating shaft I6 has centrally connected thereto the operating cam 22 upon opposite sides of which is positioned a pair of helical springs 23 and 24 surrounding the shaft I6. Adjacent the bearing bosses I 9 and 20 and in spaced relation to the operating cam 22, the shaft I6 has connected thereto a pair of

stop members

25, 26 formed to provide axially extending projections 2l' and 28. respectively, preferably molded or cast integrally therewith, The stop members 25 and 255 are also provided with separate pairs of radially spaced

peripheral bosses

29 and 30, respectively. The

bosses

29 and 30 are arranged for engagement. respectively, with narrow web portions 3l and 32 formed integrally with the casing ID and extending between the bearing bosses I9 and 20 and the pillars I5 and IECL, respectively. The

peripheral bosses

29 and 30 are positioned to engage the webs 3! and 32 to limit rotational movement of the operating shaft I6 and the cam 22. The helical springs 23 and 24 are each nrovided with angularly spaced radially extending end portions embracing the projections 21 and 2S, respectively.

Referring now more particularly to Figs. 2 and 6, it will be observed that the actuating lever I4 is formed of a pair of parallel plates connected in parallel spaced relation having forked end portions and 36 mounted upon a transverse pivot pin 'ell'. The forked end portions of the plates 35 and` 36 carry therebetween a pair of

cam follower rollers

38 and 39 arranged for engagement with angularly spaced peripheral portions of the operating cam 22. A helical com pression spring Ita positioned between the pillars I5 and Ia engages at one end the casing I0 and at the other end the forked end of the actuating lever I4, thereby to bias the roller 38 into continuous following engagement with the surface of the cam 22. The earn 32 is formed with a peripheral depression 2id adjacent the roller 38 when the cam 22 and operating shaft I5 are in their mid-positions normally maintained by the helical springs 23 and 24, In this position a peripheral projection 22D on the cam 22 lies under, but does not normally engage, the roller 39. The projection 22h is not necessary to normal switch operation, but has for its purpose the limitation of movement of the actuating lever I4 due to vibration or impact. The projection 22h is so arranged that, without rotation of the shaft I6, the roller 3B cannot move suiiiciently far out of the depression 22a to open the switch contacts.

The actuating lever I4 is pivotally mounted upon the internal pillars I5 and I5a by means of the transverse pin 3l, the opposite ends of which are seated in transverse slots 48 formed in the upper ends of the pillars. The slots 40 are provided with cover plates 4I and 47. which serve both to hold the transverse pivot pin 31 in operating position in the slots 40 and to provide fixed stops for the helical springs 23 and 24. As may be best observed by reference to Figs. 1 and 2, the cover plates 4| and 42 are each slotted longitudinally to provide a pair of up-turned

spring stops

43 and 44 of unequal length engaging opposite extending ends of the helical springs 23 and 24. The stop plate 4I cooperates with the spring 23 and the stop plate 42 cooperates with the spring 24, the

stps

43 and 44 upon each plate engaging adjacent sides of the angularly spaced extending ends of the associated spring.

The actuating lever I4 has connected to each

plate

35 and 36, opposite the forked roller carrying end thereof, a wedge-shaped cam member 45. As best illustrated at Figs. 2 and 6, the cam members 45 are shown as blocks of molded insulating material bolted to the actuating lever I4 and arranged for reversal in a manner hereinafter to be described, to select either a normally open or a normally closed position of the associated contacts.

Referring now to the contact assembly, it will be observed that the insulating contact base I 3 is of substantially box-like form and is slotted on its upper side at 45 and 41 to provide for the suspension therein of a corresponding number of pairs of contact elements. Each contact assembly comprises a pair of

cantilever spring strips

48, 49. Each contact spring has an outturned ear at its base end bolted to the top side of the base and to an associated terminal block 5B or 5I,as shown at Fig. l. Each pair of spring strips extends through one of the slots 46, 4'I in proximate parallel spaced relation and preferably has positioned between the fixed ends of the strips an insulating spacer 52.

The cooperating

cantilever spring strips

48 and 49 carry at their free ends a pair of cooperating switch contacts 53, and 54, and are formed to provide adjacent the contacts a pair of juxtaposed

carnming portions

55 and 55 for cooperation with the wedge-shaped cam 45. Preferably, the

spring strips

48 and 43 are tapered toward their free ends to reduce the mass and inertia of the free ends thereby to reduce their vibration. The spring strips of each pair are biased toward each other to maintain the cooperating contacts 53 and 54 normally in engagement. The associated

camming portions

55 and 56 are arranged to be slightly spaced apart when the contacts are in engagement. In the illustrative embodiment of the invention, the camming portions 55 and 5S are formed integrally with the

spring strips

49 and 48, respectively, and extend laterally and in parallel spaced relation therefrom in the region of the switch contacts.

By reason of the manner of mounting the

cantilever spring strips

48 and 49 described above, and because of the design of the spring strips themselves, their tendency to bounce open or to slide upon each other when subjected to vibration or shock in engaging position is substantially eliminated. As described above, each pair oi spring strips extends in proximate parallel spaced relation through a relatively narrow slot in the upper side of the base I3. The xed ends of each pair of cantilever springs are therefore mounted upon the base in closely spaced relationwith respect to the length of the spring strips. This brings the theoretical points oi fiexure of the springs very close together. rlhe cantilever springs and the associated switch contacts, being of substantially the same physical proportion, tend to move sideways at substantially the same speed in response to vibration or shock. Since the points of flexure of the springs are very close together, the free ends of the springs swing from substantially the same point so that there is very little, if any, sliding movement between the contacts. It has been found that this tendency of the contacts to move together at substantially the same speed thereby to avoid bouncing of the contacts under vibration or shock is greatly enhanced by spacing apart the theoretical points of flexure at the fixed ends of the springs by substantially the same distance as the centers oi gravity of the springs and connected contacts. With such spacing a shock in any direction will produce a turning in the same direction in both contact springs, thereby to produce following rather than separating movement o f the contacts. If the points of flexure were spaced apart substantially farther than the centers oi gravity, an impact along a line between the centers of gravity would produce opposite turning movements thereby to open the contacts.

To further reduce the tendency of the contacts to bounce apart under shock, the contact closing bias of each spring strip is sufliciently strong to permit it to follow its mate to the limit oi its movement. In this connection, it will be noted that each pair of spring contacts is positioned in recess between the side walls and a central boss 69 of the contact base I3. The boss 6I) and the side walls of the base provide stops 6I and E2 for limiting lateral movement of the spring strips. If, under shock or vibration, either strip of a pair of contact strips is moved against its bias and into engagement with the associated stop, the closing bias of the cooperating spring strip is sufficient to permit it to follow the iirst strip to the limit of its movement, thereby to maintain the contacts closed. The contact stops SI and 62 formed upon the base I3 and the boss 6I) are very close to the center of gravity of the associated contact elements, so that only slight lateral vibrational movement is permitted. By this close spacing of the contact stops, twisting motion of the contact springs under shock is prevented, thereby to eliminate local vibrational forces which may be set up by such twisting.

The use of the

camming extensions

55 and 56 on the free ends of the contact strips for cooperation with the wedge-shaped cams 45 has the advantage that, when the contacts are separated by insertion of the wedge 45, they move apart With a rolling motion, as distinguished from the straight-line motion which would result from insertion of the wedges` directly between the contact suriaces. In the illustrated embodiment or" the invention, this rolling motion results from a twisting of the spring strips 48 and 43 caused by exerting the separating force at only one side o the center lines of the strips. The rolling separating motion has a desirable tendency to discourage arcing upon separation of the contacts.

As previously mentioned, any pair of contacts may be arranged to be normally open or normally closed by merely reversing the position of the associated wedge-shaped cam 45 with respect .to the actuating lever I4. Referring particularly -to Fig. 2, it will be observed that, if the cams 45 are turned around 180 upon a vertical axis as viewed in the drawings, the widest portion of the cam will normally fall between the

camming portions

55 and 56 of the associated spring strips, thereby normally to maintain the contacts in open position. Aotuating movement of the lever I4 in a counterclockwise direction about the pivot pin 31, as viewed at Fig. 2, would then move the narrow portion of the wedge-shaped cams 45 between the

spring extensions

55 and 56 to permit closing of the contacts. As illustrated in the drawings, both pairs of contacts are normally closed. V

It is believed that from the foregoing detailed description of the construction and arrangement of the various parts of my switch, its mode of operation will be easily understood. Brieiiy, it may be noted that separation of the contacts may be effected by either clockwise or counterclockwise movement of theV operating shaft I6, as viewed at Fig. 2. For example, if the shaft I6 is moved in .the clockwise direction, the spring stops 43 hold one end of each of the helical springs 23 and 24 stationary and the

projections

21 and 28 on

ythe stop members

25 and 25, respectively, move the opposite ends of the springs in a clockwise direction against the spring restraining force. Clockwise movement of the operating shaft is limited by engagement of the upper

peripheral bosses

29 and 30 on the stop members 25 and 26 (as viewed at Fig. 2) with the webs 3| and 32, respectively, of the casing HJ. The cam 22, moving in a clockwise direction with the opu era-ting shaft I6, moves the roller 38 on the ac-tuating lever i4 out of the slot 22a thereby to move the actuating lever i4 in a counterclockwise direction, as viewed at Fig. 2, against the bias of the spring 14a. Counterclockwise movement of the actuating lever I4 moves the wide portions of the wedges 45 between the

camming extensions

55 and 56 of the spring strips to separato the contacts. As soon as'the operating lever I2 is released, the helical biasing springs 23 and 24 return the operating shaft I6 to its normal mid position as shown in the drawings.

Upon counterclockwise movement of the opern ating shaft I6, as viewed at Fig. 2, an entirely similar action takes place, except that the spring Stops 44 serve Ito hold stationary theassociated ends of the helical springs 23 and 24, while the

projections

21 and 28 move the other ends of the springs in a counterclockwise direction. Counterclockwise movement of the cam 22 also raises the roller 38 out of Ithe slot 22a and produces counterclockwise movement of the actuating lever Mi to separate the contacts.

While I have shown only one preferred embodiment of myinvention by way of illustration, many other modifications will occur to those skilled in the art and I, therefore, wish to have it under- 6 stood that I intend in the appended claims to cover all such modications as fall within the true spirit and scope of my invention.

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

l. An electric switch comprising a base, a pair of cantilever spring strips mounted at one end upon said base in substantially parallel spaced relation and providing at their free ends cooperating switch contact portions and separate juxtaposed camming portions extending laterally from said spring strips in parallel spaced relation, said spring strips being biased to maintain said contact portions in engagement and said camming portions in proximate spaced relation, and switch actuating means comprising a wedgeshapedA cam movable from a position of disengagement to a position between said camming portions only, thereby to separate said contact portions with a torsional rolling action.

2. An electric switch comprising a base, a pair of cantilever spring strips mounted at one end upon said base in substantially parallel spaced relation, a pair of cooperating switch contacts mounted upon the free ends of said spring strips, said spring strips being biased to maintain said contacts in engagement and being provided at said free ends with juxtaposed camming portions extending laterally from said strips in parallel spaced relation, and switch actuating means com prising a wedge-shaped cam movable from a position of disengagement to a position between said camming portions only, thereby to separate said contacts with a torsional rolling action.

3. An electric switch comprising a base, a pair of tapered cantilever spring strips mounted at their wider ends upon said base at points proximately spaced in relation to the length of said spring strips and extending in substantially parallel spacedV relation, a pair of cooperating switch contacts mounted upon the narrow free ends of said spring strips, said spring strips being provided at said free ends with juxtaposed camming portions and being biased to maintain said contacts in engagement and said camming portions in proximate spaced relation, fixed vstop means adjacent said free ends of said spring strips for limiting contact disengaging lateral movement of each of said spring strips, the spacing between said stop means and the adjacent spring strip being substantially equal to the spacing between said spring strips, and switch actuating means comprising awedge-shaped cam movable from a position of disengagement to a position between saidv camming means to separate said contacts.

4. .An electric switch adapted for subjection to vibration and impact shock comprising a base, a pair of cantilever spring strips mounted at .one end upon said base at points proximately spaced in relation to the length of said spring strips and extending therefrom in substantially parallel spaced relation, a pair of cooperating switch contacts mounted upon the free end of said spring strips, said spring strips being provided at said free ends with juxtaposed camming portion and being biased to maintain said contacts in engagentent and said camming portions in proximate spaced relation, fixed stop means adjacent said .free ends of said spring strips for limiting contact disengaging lateral movement of each of said spring strips, the spacing between said stop means and the adjacent spring strip being substantially equal to the spacing between said spring strips, the contact engaging bias of each of said spring strips `being suflicient to permit it to maintain following engagement with the cooperating spring strip at least until said cooperating spring strip engages its associated stop means when subjected to vibration or impact, and switch actuating means comprising a wedgeshaped cam movable from a position of disengagement to a position between said camming means to separate said contacts.

5. An electric switch comprising a base, a pair of cantilever spring strips mounted at one end upon said base at points proximately spaced in relation to the length of said spring strips and extending in substantially parallel spaced relation, a pair of cooperating switch contacts mounted upon the free ends of said spring strips, said spring strips being provided at said free ends with juxtaposed camming extensions projecting laterally from said strips adjacent said contacts and being biased to maintain said contacts in engagement and said camming extensions in proximate spaced relation, fixed stop means adjacent said free ends of said spring strips for limiting contact disengaging lateral movement of each of said spring strips, the spacing between said stop means and the associated spring strip being substantially equal to the spacing between said spring strips, a switch actuating lever carrying at one end a wedge-shaped cam movable from a position of disengagement to a position between said camming means to separate said contacts, a forked cam follower mounted upon the opposite end of said switch actuating lever, and a rotatable operating cam disposed in operative relation with respect to said forked cam follower for actuating said switch actuating lever, said forked cam follower providing a pair of members disposed adjacent angularly spaced points of said operating cam thereby positively to maintain continuous following relation therebetween.

6. An electric switch comprising a base, a pair of cooperating switch elements each including a cantilever spring strip carrying at its free end a switch contact, said spring strips extending from said base in substantially parallel spaced relation and being mounted at points spaced by substantially the same distance as the centers of gravity of said switch elements, a pair of juxtaposed camming extensions projecting laterally and in parallel spaced relation from said spring strips adjacent said contacts, said spring strips being biased to maintain said contacts normally in engagement and said camming extensions in proximate spaced relation, and switch actuating means comprising a wedge-shaped cam movable from a position of disengagement to a position between said camming extensions only, thereby torsionally to stress said spring strips and to separate said contacts with a rolling action.

7. An electric switch comprising a slotted base, a pair of cooperating switch elements each including a cantilever spring strip carrying at its free end a switch contact, said pair of spring strips extending in substantially parallel spaced relation through a slot in said base and being 'mounted upon said base at points spaced by substantially the same distance as the centers of gravity of said switch elements, a pair of juxtaposed camming extensions projecting laterally from said spring strips adjacent said contacts, said spring strips being biased to main-- tain said contacts in engagement and said camming extensions in proximate spaced relation, fixed stop means adjacent said free ends of said spring strips for limiting contact separating lateral movement of each of said spring strips, the spacing between said stop means and the adjacent spring strip being substantially equal to the spacing between said spring strips, and switch actuating means comprising a Wedge-shaped cam movable from a position of disengagement to a position between said camming extensions to separate said contacts.

8. An electric switch comprising a slotted base, a pair of cooperating switch elements each including a tapered cantilever spring strip carrying at its narrow free end a switch contact, said spring strips extending through a slot in said base in substantially parallel spaced relation and being mounted at their wider ends upon said base at points spaced by substantially the same distance as the spacing between the centers of gravity of said switch elements, a pair of juxtaposed camming extensions projecting laterally from said free ends of said spring strips, said spring strips being biased to maintain said contacts in engagement and said camming extensions in proximate spaced relation, fixed stop means adjacent said free ends of said spring strips for limiting contact separating lateral movement of each of said strips, the spacing between said stop means and the adjacent spring strip being substantially equal to the spacing between said spring strips, the contact engaging bias of each of said spring strips being surficient to permit it to maintain following engagement with the cooperating spring strip at least until said cooperating spring strip engages the associated stop means, and switch actuating means comprising a wedge-shaped cam movable from a position of disengagement to a position between said camming extensions to separate said contacts.

WILLIAM LAWRENCE BUTLER.