US2439747A - Electric switch - Google Patents

Description

April 13, E948. R G, NELSQN 2,439,747

ELECTRIC SWITCH Filed Jan. 28, 1944 5 f7 44 45 I @760 g4 l L- l j ji38 38355295646 U47 66065 6 7 Patented Apr. 13, 194s mirarme swrrcn Royal G. Nelson, Freeport, Ill., assigner, by mesne assignments, to First Industrial Corporation, Wilmington, Del., a corporation of Delaware Application January 28,1944, serial No. 519.983

6 Claims. (Cl. 20o-67) .tact mechanism particularly adapted for snap switches of the type having a cantilever mounted over-center snap spring system for operating the switch.

A primary object of the invention is to provide a snap switch of the above character with a greater circuit capacity and an improved contact construction wherein the mobile contacts are selfadjusting and aligning so that good engagement is secured with the stationary contacts in spite of misalignment in the contact driving means.

Another object ofthe invention is the provision of a switch of the type having an overcenter snap spring system for moving the mobile contacts, an'd a plurality of stationary contacts engaged thereby, wherein a novel support for the mobile contacts is provided which functions to correct for angularity of the spring system and misalignment oi' the stationary contacts, and thereby produce substantially uniform contact pressure of the mobile contacts against the stationary contacts.

Other objects and advantages will appear from the following description and the accompanying drawings, in which- Figure 1 is a vertical section taken longitu-b dinally through a switch embodying the invention;

Fig. 2 is a section similar to Figure 1 showing the plunger depressed and the contacts in the opposite position;

Fig. 3 is a top view of the switch mechanism with the cover thereof removed;

Fig. 4 is a section on the line 4-4 of Figure 1;

Fig. 5 is a section on the line 5-5 of Fig. 2, and

Fig. 6 is a fragmentary view showing the mounting for the H member,

The present invention is` concerned primarily with small precision type snap acting switch mechanism of the type adapted to be operated by very small pressure and movement, and adapted to switch relatively heavy electrical loads. The embodiment of the invention herein shown comprises a base I4 of insulating material which is so shaped as to form part of a housing for the switch mechanism. Disposed on the top of the base to complete the housing structure is a cover I5. Attached to the upper face of the cover I5 are uostanding pairs of tabs I6 and I1 for theattachment of wires to connect the switch into suitable v under the plate 3|. Y member 4I is an actuator element 42 which pro- A circuits. In this instance, the tabs I6 and I1 are recessed into the surface of the cover and secured therein by rivets, as indicated at I8, which rivets pass through the top wall of the cover and also act to secure thereto within the housing spaced pairs of contacts I9, I9a, 2l and 2Ia. Likewise, the bottom of the base I4 has spaced pairs of tabs 22 and 23 secured to the base in the same manner as the tabs I6 and I1, as by rivets 24, which rivets likewise retain against the interior of the base spaced pairs of contacts 25, 25a, 28 and 26a. The base I4 has an upstanding portion 21 providing a horizontallydisposed shoulder 28 against which is attached one end of `a leaf Spring 23. The spring is rigidly and xedly attached thereto in cantilever fashion by means of a. plate 3| and screw 32, the plate projecting forwardly into the cavity of the housing and being formed upwardly, as. shown at 33, in spaced relation to the switch spring. The forward end of the plate converges. as shown at 34, and has an opening 35 i'or the passage therethrough of an actuating pin 36 carried in the cover I5 and adapted to engage the spring system, presently to be described, for the Purpose of actuating the switch mechanism.

In this instance, the spring system is made substantially in accordance with the principle disclosed land claimed in a. copending application of Edward Meyer, Serial No, 519,984, filed January 28, 1944, now Patent No. 2,425,159, issued August 5, 194'?. The'switch spring 29 comprises a somewhat rectangular shaped piece of relatively thin spring material, such as berylium copper, having a part of the central portion removed, as by stamping, to provide side members 31 and 38 and end members 39 and 4|, the end 4I being secured Projecting from the end jects youtwardly therefrom into the central space 43 and is of decreasing width terminating in a point, as shown at 44. Also disposed in the central area `of the switch spring is a U-shaped portion having legs 45 and 43 connected by an end portion 41, the opposite ends oi' the legs being connected, as shown at 48 and 49, to the -side members 31 and 38 intermediate the ends of the side members.

Cooperating with the switch springA to provide an over-center spring mechanism is an 'H- shaped driving element, such as shown in Fig. 5, having an upper bar 5I, lower bar 52, and a connecting portion 53, the connecting lportion being'adapted to seat against a point 5I) (Fig.

'6) on the inner edge of the free end 41 and the the reception of the pointed end 44 of the actuating element 42. The expansion member forms a resilient connection between the free end 41 of the switch 'spring and the free end 44 of vthe actuator element -42.

It will be seenthat the switch spring and thc expansion spring together form two interdependent systems, one of these systems comprising a coil spring 55, the end 41, the legs 45 and I6, the H-shaped driving element, the switch driving system, and the 'spring portions 59 and 6I and end 39 forming a resilient driven system. Because of the ilexibility of the switchspring, the driven system is movable with thedriving system and also is movable with lost motion with respect to the driving system. l

In the speciiic embodiment of the switch shown, the position of the parts shown in Figure 1 is the normal position of the switch mechanism,

themobile contacts being disposed in engagement with the lower stationary contacts. When 'f the plunger 36 is depressed, the actuator element 42 is moved from the position of Figure l to the position of Fig. 2, during which movement the point 44 of the actuator element is initially moved downwardtoward the compression center I line of theswitch spring against the compression .of the expansion member 55. When this point is moved through the axis ofrmaximum stress the spring systemreverses its positionrto that shown in Fig. 2 with a snap movement, carrying the resilient driven system with it. The modulus of the actuator element 42 is such that when the plunger is moved downwardly until the downward force exerted by the end thereof slightly exceeds the upward component of the force exerted through the expansion member by legs 45 and 4B, downward motion at an accelerated rate occurs due to the fact that the slope of the force-movement curve of the expansion element is greater than that of the actuator element. During the initial part of the snap movement the bar 5I moves away from the side members 59 and EI and the bar 52 approaches the lower side of the side members, the initial part of the snap movement thus being utilized in lost 'motion as between the spring system and the driven system to permit the spring system to gain velocity before the bar 52 strikes the driven system so as to impart thereto a hammer blow to break loose any minor welding of the contacts which may have occurred and to drive the mobile contacts rapidly to the opposite position.

Attached to the end member 39, as by p in in the form of a rivet 62, is a contact support comprising a strip of insulating material 63 which projects outwardly from the end member 39, as best shown in- Fig. 3 in somewhat exaggerated form for the purpose of illustrating the operation, the insulating strip being conveniently formed to provide legs 64 and 65 for the purpose oi' supporting a pair of contacts GS and 61. vSubstantial clearance is provided between the unit and the opening in the strip of insulation and between the head ofthe rivet and the contact support to permit the entire contact support to move within limits with respect to the end member 39 and to engage both pairs of upper or lower contacts I9, I9'a, and 2|, 2Ia, (or .25, 25a and 26, 26a depending upon the position ot the switch) and to tilt with respect to the end member so as tobring it into a position approaching parallelism with respect to the plane oi' the contacts in spite of the angular position oi' the spring. Stops in the form ot shoulders 60 on the switch spring prevent excessive rotation of the contact holder about the rivet 62.k Each of these contacts comprises pin in the form of a rivet 68 having heads on opposite ends thereof, the rivet passing through a. U-shaped connectingmember or strap 69 which passes around the edge of the insulating material, the rivet passing through the upper and lower legs thereof. The openings in the arms 64 and 65 are of such size that the shank ofthe rivets 68 can slide freely therethrough and are capable of limited tiltingV movement. The arms are so positioned that in the opposed positions of the switch the heads of the rivets engage either the contacts I9, I 9a. and 2|, 2Ia, as shown in Fig. 2, or the contacts 25 and 26, as shown in Figure 1, the rivet heads spanning the space between the spaced contacts to provide a conducting path therebetween. The loose mounting of the rivets permits the contacts to be individually self-aligning between the contacts I9 and 2I or the contacts 25 and 26 through tilting movement of the contacts about an axis transverse to the switch.

It will be seen that in order to establish good and satisfactory engagement at the stationary contacts itis essential that the mobile contacts engage each of the four upper or lower contacts with a substantial contact pressure so as to prevent arcing and spitting at the contacts. Thev dilculty as a practical matter of'uniformly arranging these contacts in accurate coplanar relationship at the correct angles and uniform dimensions will be appreciated. The necessity for this uniformity lis avoided by making the mobile contacts in the manner described so that they can tilt on a lateral axis to accommodate for such irregularities in manufacture. Likewise, this arrangement accommodates for any difference in angularity between the plane of the contact support and the plane of the engaging faces of the stationary contacts. On the other hand', the mounting of the contact support loosely on the rivet 62 with only suicient clearance to permit of. the necessaryrealignment causes each of the spaced mobile contacts 68 to be brought into engagement with their respectiverpairs of contacts I9, |9a and 2i,

2Ia (or 25, 25a and 2625a) in spite of any' variation in the planes of these contacts and in spite of the angularity of the spring with respect tothe plane of the stationary contacts.

While the construction shown in the drawingsv is such that the spring and contacts are seli`- -retuming. these can be made for manual reset by regulating the unstressed shape of the actuator element 42 and by adjusting the positions of the contacts or stops in accordance with the teachings of the art.

I claim:

1. 'I'he combination in a precision switch of a switch spring having a free end movable in an arc between opposed positions, a contact carrier of insulating material mounted on said free end, a plurality of spaced mobile bridging contacts on said carrier, a plurality of spaced pairs of spaced xed contacts, each pair being positioned for engagement by one of said mobile contacts to limit the movement of said free end in one direction and thereby dene one of said opposed positions. means for mounting each of said mobile contacts on said carrier comprising a U-shaped strap having ends spaced a substantially greater ment of said carrier circumferentially of the pin and about an axis transverse with respect to said pin, and means for limiting the circumferential and transverse movement of said carrier.

2. The combination in a precision type switch, of a switch member mounted at one end, means for effecting movement of the opposite end thereof with snap motion between two opposed positions, a plurality of spaced xed contacts arranged in spaced pairs adjacent said opposite end, a contact carrier of insulating material mounted on said opposite end, a plurality of movable bridging members on said carrier positioned to engage the fixed contacts to limit the movement of said opposite end in at least one of said positions and to apply contact pressure thereto, said bridging members each being positioned to bridge between the contacts of one of said pairs of stationary contacts, said bridging members each being mounted for independent universal movement on the carrier to align each of the bridging members with the corresponding pair q ,of ilxed contacts engaged thereby in response to 'engagement of the bridging member therewith for the application of uniform contact pressure between the bridging member and the fixed contacts, and means for mounting said carrier on said opposite end for limited universal movement with respect thereto in response to engagement of the bridging members with the fixed contacts to align the carrier with respect to the pairs of xed contacts and thereby accommodate for variations in the relative positions of said pairs of stationary contacts and for variations in the angularity of said opposite end of the switch member.

3. The combination in a precision switch of a switch member having a free end movable between opposed positions, a. contact carrier of insulating material mounted on said free end, a plurality of spaced mobile bridging members on said carrier, a plurality of spaced pairs vof spaced xed contacts, each pair being positioned for engagement by one of said bridging members to` limit the movement of said free end in one direction and thereby denne one of said opposed positions, means including a pin extending through a larger sized opening for mounting the bridging members on the carrier for limited universal movement kwith respect to the'carrier for independent self alignment of said bridging members with each pair of fixed contacts in response to engagement thereof with the pairs of ixed contacts, and means including a pin extending through a larger sized opening for mounting said carrier for limited universal movement with re- Spect to said free end in response to engagement of the bridging members with the respective pairs of fixed contacts for self alignment of the carrier whereby to effect a relatively uniform contact pressure between the bridging members and the engaged pairs of fixed contacts.

4. The combination ina precision switch of a switch member having a free end movable between opposed positions, and spring means for urging said free end into the opposed positions, a

.contact carrier of insulating material mounted on said free end, a plurality of spaced mobile bridging members on said carrier, a plurality oi pairs of spaced fixed contacts adjacent one side of said tree end, a plurality of pairs oi'spaced nxed contacts adjacent the opposite side of said free end,

said pairs being arranged in opposition for alternate engagement by said bridging members in the opposed positions of said free end to complete a1- ternate circuits therethrough land to limit the movement of said free end in opposite directions, thereby defining said positions, means for mounting said bridging members on said carrier for limited universal movement with respect to the carrier in response to engagement of the bridging members with the respective stationary contacts, and means for mounting said carrier for limited universal movement with respect to said free end for alignment thereof whereby to bring the bridging members into engagement with the pairs of fixed contacts under the force applied by said spring means.

5. In a precision snap switch the combinati-on of, an elongated switch member mounted at one end and having the opposite end shiftable between opposed positions, a plurality of pairs of spaced, fixed contacts on each side of said switch member arranged so that the pairs of contacts are spaced laterally of the switch member and the contacts of each pair are in spaced relationship, a mobile contact carrier, means for mounting said carrier gon said switch member for limited universal movement of the carrier with respect to the switch member, contacts arranged to bridge each respective pair of spaced contacts on either side of said switch member, means including a pin passing through said carrier for mounting said bridging contacts on said carrier for limited universal movement of each bridging contact with respect to the carrier, said mounting means for the carrier 'and the bridging contacts effecting selfalignment of each bridging contact with the respective pair of contacts as the switch member is shifted from one position to the other.

t 6. In a precision snap -switch the combination of, an elongated switch member mounted in a cantilever fashion at one end and having the opposite end shiftable between opposed positions, a plurality of pairs of spaced, fixed contacts on each side of said switch member arranged so that the contacts of each pair are in spaced relationship, a mobile contact carrier, means for mounting said carrier on said switch member for limited univers-a1 movement of the carrier with respect to the switch member, stops for limiting the rotational motion of the carrier around the mounting axis, a contact arranged to bridge each pair of spaced contacts, means for mounting said bridging contacts on said carrier for limited universal movement of each bridging contact with respect to the carrier, said mounting means for the carrier and the bridging contacts effecting self-alignment and -a good wiping contact of each bridging contact with each respective pair of contacts as the switch member is shifted from ROYAL G. NELSON;

REFERENCES CITED The following references are of record in the file of this patent:

UNrrrzD .STATES PATENTS one position to the other.

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