US2753411A - Snap action switch - Google Patents

Description

Jy 9 1956 A. E. BAAK 2,753,411

SNAP ACTION SWITCH Filed Nov. l5. 1952 United States Patent O SNAP ACTEN SWHTCH Albert E. Baak, Pacific Palisades, Calif., assigner to Paul Henry, Los Angeles, Calif.

Application November 13, 1952, Serial No. 320,273

4 Claims. (Cl. zuil-67) This invention relates to snap action switches and, more particularly, toggle switches, and is directed especially to the problems involved in providing such a switch to control current of sutiicient magnitude to tend to weld the switch contacts.

While the invention may be embodied in various specie switch structures for various circuit controlling functions, it has been initially embodied in a double-throw single-pole switch. For the purpose of disclosure and to illustrate the principles involved, this embodiment of the invention will be described in detail herein. Such a description will serve as adequate guidance for those skilled in the art who may have occasion to embody the features of the invention in other structures for other specific purposes.

A double-throw single-pole switch of this type usually comprises a switch member that rocks between two positions, two fixed contacts positioned respectively to cooperate with the switch member at its two positions, respectively, and an actuating means that rocks the switch member between its two positions with a snap action. The switch member and the two fixed contacts are connected to three corresponding switch terminals and when the switch is placed in service the switch member commonly closes a circuit for current ow at each of its two alternate positions.

One problem in such an arrangement is to provide a satisfactory electrical connection between the rocking switch member and the corresponding switch terminal. In some instances, the connection is made through the pivotal support of the switch member but the result in handling current of substantial amperage is usually deterioration of the pivot construction by arcing. In other instances, a wire directly connects the switch terminal with the switch member but such a construction is objectional for a number of reasons, including the weakening of the wire by repeated tiexure.

The invention solves this problem in a double-throw single-pole switch oy using a pair of contacts to cooperate with the switch member at each of its two alternate positions. One contact of each pair is connected to a corresponding switch terminal and the remaining two contacts, one of each pair, are both connected to the third switch terminal. The switch member merely serves as a bridging means across each pair of contacts thus eliminating the necessity of directly connecting the switch member to the third switch terminal.

A second problem arises from the tendency of current of this amperage to weld the switch member to one of the fixed contacts. The actuating means is springloadedto move the switch member with a snap action but the force exerted by the spring is not strong enough to break a weld. Consequently, the usual switch becomes completely inoperative when a weld forms and it becomes necessary to dismantle the switch for access to break the weld. t

The seriousness of this second problem is reduced in the present invention by using the switch member as a "ice bridging means across a pair of contacts, asdescribed above. When a switch member is directly connected to a switch terminal the arcing effect that occurs in breaking a circuit is concentrated at one point between the switch member and the fixed contact. In the present invention, on the other hand, the switch member in serving merely as a bridge between the two contacts provides two arcing points in series and thus reduces the tendency of welding action to occur at either point.

The complete solution for this second problem, however, is provided in the present invention by incorporating in the switch construction means for mechanically breaking a weld whenever necessary. A feature of the preferred form of the invention is that the: actuating member, which is in the form of a lever, normally moves the pivoted switch member by spring pressure but is automatically brought into action as a lever to pry the switch member loose whenever a weld occurs.

The third problem is to insure adequate pressure between the switch member and each of the two spaced fixed contacts that are positioned to be bridged by the switch member. ln the usual switch construction wherein a switch member touches two contacts simultaneously, the pressure exerted by the switch member is more or less concentrated at one of the two contacts. The invention meets this problem by mounting the switch member on a single pivot point to result in a three-point support for the switch member at each of its two alternate positions. The two contacts at each position together with the single pivot point form a triangle of three support points and the spring-loaded actuating means applies pressure within the triangle, which pressure is distributed among the three support points. Thus, the pressure exerted by the switch member against the two spaced contacts is equalized between the two contacts.

The provision of a single pvot point for the switch member introduces the further problem of guiding the switch member adequately between its two positions. Since the switch member is universally movable about its single pivot point, some provision must be made to restrict its freedom of movement but the restriction must not interfere with freedom of the switch member to rock transversely to equalize its pressure between two contacts.

This further problem is solved by providing a track on the switch member for engagement by the actuating means to keep the switch member in the required orientation. In the preferred practice of the invention in which the actuating member is a spring-loaded longitudinally extensible lever, the end of the lever is provided with a rotary means in pressure contact with the switch member and the switch member is formed with a groove to serve as a track for movable engagement by the rotary means. Since the switch member is engaged at one point by the universal pivot means and is engaged at another point by the actuating lever it is maintained in proper orientation for cooperation with the two spaced fixed contacts at the two positions of the switch member, At the same time, freedom for rotation about a longitudinal axis defined by these two points permits the switch member to equalize its pressure between the two fixed contacts at each of its two alternate positions.

The above and other objects and advantages of the invention will be apparent in the following detailed description, together with the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative,

Fig. l is a side elevation of the presently preferred embodiment of the invention with parts broken away to reveal concealed structure;

Fig. 2 is a longitudinal medial sectional View showing the switch member in one of its two positions;

Fig. 3 is a similar view showing how the switch parts cooperate to break a weld;

Fig. 4 is a transverse sectional view taken along the broken line 4-4 of Fig. 2; and

Fig. 5 is a section taken along the line 5-5 of Fig.l l.

The switch shown in the drawings includes a box-like casing 1t) of nonconducting material having a relatively thick bottom wall 11 and an open top closed by a metal cover plate 12 anchored by suitable screws 13. Preferably a suitable sealing gasket 14 is inserted under the cover. The principle parts of the switch include a switch member 16 pivoted to rock between two positions, an actuating means generally designated 17 to rock the switch member between its two positions, and at least one xed contact to cooperate with the switch member at one or both of its two positions.

In the particular construction shown, there are two fixed contacts to cooperate with the switch member at each of its two positions. Thus, as best shown in Fig. 5, there is a pair of contacts 2@ and 21 positioned on the bottom casing wall 11 to be bridged by the switch member 16 at one of the switch member positions and a second pair of fixed contacts 22 and 23 positioned on the bottom casing wall to be bridged by the switch member at the second position of the switch member. Fixed contact 20 is the enlarged inner end of a terminal post 25 that extends through the bottom wall 11 and is anchored by a retaining nut 26. In like manner, fixed Contact 22 is the enlarged inner end of a terminal post 27 that is secured by a retaining nut 28. The other two fixed contacts 21 and 23, one contact of each of the two pairs of contacts, are electrically interconnected by a conductor strip 30. A third terminal post 31 having a flange or head 32 bonded to the conductor strip extends through the conductor strip and is secured by a nut 33.

The switch member 16 may comprise a rectangular metal plate 35 on the underside of which are mounted four metal blocks 36, 37, 38 and 39 to cooperate respectively with the four xed contacts 20, 21, 22 and 23. In the particular construction shown, the metal plate 35 is centrally oiset downward to form a relatively wide longitudinal groove 40 and at the bottom of the groove is mounted a downwardly facing pivot socket member 41 to cooperate with a pivot pin 42 mounted in the bottom casing wall 11. The socket member 41 forms a conical seat to receive the pivot pin 42 and the pivot pin has a relatively sharp point to engage the socket member with substantial freedom for universal movement of the socket member about the point of the pin.

It is contemplated that the switch member 16 will be provided with track means for cooperation with the actuating means 17 and will also be provided with means for cooperation with the actuating means 17 to pry the switch member loose from any weld that may occur at any of the four fixed contacts 2t), 21, 22 and 23. For this purpose, a channel-shaped sheet metal member 43 having a bottom wall 44 and two side walls 45 is mounted on the upper side of the metal plate 35 in an insulated manner. Preferably, the required insulation comprises a relatively thick plate 46 of nonconducting material together with a thin flexible sheet 47 of non-conducting material, these two insulating members being secured to the metal plate by means of rivets 48. The bottom wall 44 of the sheet metal member 43 is anchored to the insulating plate 46 alone by two rivets 50 that are positioned over the groove 40 with the insulating sheet 47 bowed into the groove under the rivets.

The insulating plate 46 is cut away to provide a wide longitudinal slot 53 (Fig. 4) to permit the bottom wall 44 of the sheet metal member 43 to be centrally oiiset downward to form a longitudinal track 54 in the form of a V-shaped groove. The bottom wall 44 of the sheet metal member 43 is slit transversely, as shown at 57 in Fig. 2, to permit the metal to be offset in the desired manner.

The required auxiliary means carried bytheswitch member 16 for cooperation with the actuating means 17 to break any welds that may occur, comprises two spaced means in the path of movement of the actuating means 17. Such auxiliary means may comprise, for example, two spaced crosspins 55 and 56 interconnecting the two side walls 45 of the sheet metal member 43.

The actuating means 17'is preferably in the form of a spring-loaded longitudinally extensible lever that is pivotally mounted on the cover plate 12 to extend through a flanged opening eti in the cover plate. In the construction shown, the actuating lever comprises an upper section 61 with a hollow lower end 62 and a spring-loaded lower section or actuating member 63 with a hollow upper end 64, these two hollow ends being slidingly telescoped together to confine a coil spring 65 that continuously urges the two sections apart.

The upper section 61 of the actuating lever is rotatably mounted on a pivot pin 68 that extends across the tianged opening 6u and is held against the underside of the coverplate 12 by a sheet metal retainer 69. The upper section 61 of the actuating lever may be provided with a suitable knob or handle 70 and preferably is formed with a spherical shoulder 71 so that the actuating lever substantially completely spans the flanged opening 60 in the cover plate 12 at all positions of the lever. Itis also preferable to mount a thin sheet 72 of suitable plastic material across the flanged opening 60 between the sheet metal retainer 69 and the underside of the cover plate 12, this plastic sheet being apertured for relatively close iit with the spherical shoulder 71 of the actuating lever.

The lower end of the actuating lever 17 is provided with suitable rotary means for rolling engagement with the longitudinal track or groove 54 on the upper side of the switch member 16. For this purpose, the lower end of the actuating lever rnay be forked to receive a small Wheel 75 having trunnions 76, which trunnions are engaged by slots 77 in the end of the lever.

The manner in which the described switch operates may be readily understood from the foregoing description and the drawings. In the inclined position of the switch member 16 shown in Figs. 1, 2 and 4, the switch member electrically bridges the xed contacts 20 and 21, thereby providing a conducting path between the terminal post 25 and the terminal post 31. In the alternate position at which the switch member is inclined in the opposite direction, it electrically bridges the two iixed contacts 22 and 23 to form a conducting path between the terminal post 27 and the terminal post 31. Thus, the terminal post 31 is electrically connected to the two fixed contacts 20 and 22, respectively, which are positioned at the two alternate positions of the switch member.

Normally, when the switch member is at the inclined position shown in Fig. 2, the spring-loaded longitudinally extensible actuating lever 17 is at the position shown in Fig. 2 pressing the switch member downward against the two iixed contacts 20 and 21. It will be noted that at this position of the switch member 16 the switch member is supported at three points to resist the downward thrust from the actuating lever 17, one support point being provided bythe pivot pin 42 and the other two support points being provided by the fixed contacts 20 and 21. Since the point of downward pressure by the actuating lever against the switch member is inside the triangle deiined by these three points, the downward pressure of the actuating lever is distributed among the three points. In this instance pressure is equalized between the two fixed contacts 20 and 21 since these two fixed contacts are at equal distances from the pivot pin 42 and are also at equal distances from the point at which the downward pressure is applied by the actuating lever.

If the actuating lever 17 is manually swung from the limit position shown in Fig. 2 to its opposite limit position, the wheel 75 will be moved along the longitudinal track 54 across the vertical axis of the pivotpin 42 to cause the switch member to rock about a horizontal axis to its alternate position against the alternate pair of fixed contacts 22 and 23. Normally the rocking movement of the switch member from one position to another will occur with a snap action. At the second position of the switch member, the downward pressure from the actuating lever 17 will again be opposed by three support points, i. e., at the pivot pin 42 and the two :fixed contacts 22 and 23. As a result, pressure will be equalized between the two fixed contacts 22 and 23.

It will be noted in Fig. 4 that the longitudinal track 54 formed by the V-shaped groove in the bottom wall 44 of the sheet metal member 43 makes effective guiding contact with the wheel 75. Thus, the pivot pin 42 engages the switch member at one point and normally the wheel 75 engages the switch member at a second spaced point, two spaced points of engagement being suflicient to prevent rotation of the switch member about the vertical axis of the pivot pin 42. In this manner the switch member is maintained in the desired orientation with the four contact blocks 46, 47, 48 and 49 of the switch member positioned at all times to cooperate with the corresponding iixed contacts 20, 21, 22 and 23. It is to be noted, however, that at the two alternate positions of the switch member it is free to rotate about a longitudinal axis defined by the point of support by the pivot pin 42 and the point of contact by the wheel 75. The freedom to rotate about this longitudinal axis permits the desired pressure equalization across each of the two pairs of lixed contacts.

The manner in which the actuating lever 17 cooperates with the two auxiliary means or crosspins and 56 to break any welds that may occur at either position of the switch member may be understood by referring to Figs. 2 and 3. In a normal position of the actuating lever 17 where it presses the switch member 16 downward against a pair of xed contacts, the actuating lever is spaced from the adjacent crosspin by a small clearance. Thus, in Fig. 2 the actuating lever 17 does not quite touch the adjacent crosspin 55. When the actuating lever is swung to its opposite position from the position shown in Fig. 2, the switch member 16 normally rocks freely to its alternate position with a snap action as soon as the wheel 75 crosses the vertical axis of the pivot pin 42, the actuating lever reaching its second position without making contact with the second crosspin 56. Each of the two crosspins 55 and 56, however, is so positioned on the switch member 16 that it moves into and out of a position intersecting the path of movement of the actuating lever 17. Each crosspin is in the path when the actuating lever is remote from the crosspin but normally is carried out of the path by the normal rocking movement of the switch member as the actuating lever approaches the crosspin. Thus, the crosspin 56, in Fig. 2, is in the path of movement of the actuating lever 17 from the position of the lever shown in Fig. 2 to the alternate position of the lever but the crosspin normally swings out of the path when the switch member rocks to its second position in response to shifting of pressure by the wheel 75 across the pivot pin 42.

The manner in which the parts cooperate to break a weld may be readily understood. If, for example, the contact block 36 and the fixed contact 2t) should weld together as indicated at Si) in Fig. 3, the shift in the point of pressure contact by the wheel 75 from the position on one side of the pivot pin, shown in Fig. 2, to the position on the other side of the pivot pin, shown in Fig. 3, will not alone result in rocking movement of the switch member to its second position. The force exerted by the coil spring inside the actuating lever is not sufficient to break the weld Sil. In such event, however, the crosspin 56 remains in position across the path of movement of the actuating lever 17 so that the actuating lever moves into abutment against the crosspin 56 before the actuating lever reaches its limit position. It can be seen in Fig. 3 that further movement of the actuating lever 6 to its limit position results in a prying action against the crosspin 56 sufficient to break the weld 80.

It will be noted in Fig. .3 that the prying action has both an upward component of force away from the weld 8d and a longitudinal component away from the Weld. lt will be further noted that the loose engagement of the switch member with the pivot pin 42 is such as to permit the switch member to respond to both of these components. It will also be noted that the crosspin 56 is relatively close to the fulcrum of the actuating lever so that the prying force applied at the outer end of the actuating lever is multiplied at the point of application against the crosspin 56 and it will be further noted that the crosspin 56 is spaced a substantial distance from the weld for even further multiplication of the prying force at the weld itself. Forcing the actuating lever to complete its movement to its second position in opposition to the crosspin 56 breaks the weld 80 to permit the pressure of the spring 65 in the actuating lever to rock the switch member to its second position.

My description in specific detail of a preferred practice of the invention will suggest to those skilled in the art variout changes, substitutions and other departures from my disclosure that properly lie within the scope of the appended claims.

I claim as my invention:

l. In a snap action switch, the combination of: a switch member; means to pivotally support said switch member from one side at one pivot support point for universal movement about said pivot support point; a lever including a spring-loaded actuating member, means spaced from the other side of said switch member to pivotally support said lever with said actuating member in pressure contact with said other side of said switch member, said lever and said actuating member being movable along a predetermined path to shift the point of pressure contact between said actuating member and said switch member along a path between a first posi* tion on one side of said pivot support point and a second position on the other side of said pivot support point thereby to rock the switch member between a first position and a second position; at least one fixed contact to cooperate with the switch member at its rst position, said contact being positioned adjacent said one side of the switch member; and auxiliary means ixedly mounted on and spaced from said other side of said switch member in a position relative to the switch member to intersect said predetermined path when said point of pressure contact is in said lirst position and to swing beyond the end of the path when said point of pressure contact is in said second position, whereby failure of said switch member to rock from its rst position to its second position in response to shift of said point of pressure contact across said pivot point results in engagement of said lever with said auxiliary means for displacement of the auxiliary means, said auxiliary means being located between said other side of said switch member of said means to pivotally support said lever, and being provided with a surface which faces said other side of said switch member and which is engageable by said lever to pry said switch member out of its rst position.

2. A combination as set forth in claim 1 which includes a pair of xed contacts to cooperate with said switch member at its first position, said xed contacts being positioned adjacent said one side of the switch member beyond said point of pressure contact by said actuating member and on opposite sides of said pivot support point to provide three points of support for the switch member in its first position in opposition to pressure from said actuating means, thereby distributing pressure between the two fixed contacts.

3. In a switch, the combination of a supporting structure; a switch member; first pivot means pivotally mounting said switch member on said supporting structure for pivotal movement between first and second positions;

contacts on said supporting structure and said switch member, respectively, and interengaging when said switch member is in said first position; a lever; second pivot means spaced from said switch member and pivotally mounting said lever on said supporting structure in engagement with said switch member and for movement from one side to the other of said rst pivot means so as to pivot said switch member between said rst and second positions; and stop means carried by said switch member and located between said switch member and said second pivot means, said stop means having a surface which faces said switch member and which is engageable by said lever to pry said switch member out of said rst position.

4. A switch as defined in claim 3 wherein said stop means includes a stop having said surface thereon and extending across the path of pivotal movement of said lever, said lever being insertable between said switch member and said stop to pry said switch member out of said first position.

References Cited in the lc of this patent UNiTED STATES PATENTS 1,132,470 Gordon Mar. 16, 1915 1,812,914 Williams et al. July 7, 1931 1,912,623 Douglas June 6, 1933 1,912,624 Douglas June 6, 1933 2,047,950 Douglas et al. July 21, 1936 2,269,171 Benander Jan. 6, 1942 2,469,336 Kohl May 3, 1949 FOREIGN PATENTS 517,846 France Dec. 22, 1920 551,221 Great Britain Feb. 12, 1943 626,139 Great Britain July 11, 1949 974,357 France Sept. 27, 1950

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