Patent Publication Number: US-5525952-A

Title: Switchblade

Description:
BACKGROUND OF THE INVENTION 
     This application relates to the art of switches and, more particularly, to single pole, double throw switches. The invention is particularly applicable to a thermostatic switch having a bi-metal disc that snaps between opposite bowed positions for opening and closing switch contacts. However, it will be appreciated that the invention has broader aspects and can be used in other types of switches. 
     Single pole, double throw thermostatic switches commonly have a plurality of individual resilient switch arms, backup arms and a gap adjusting screw. It would be desirable to simplify such a switch by eliminating many of the individual parts. 
     SUMMARY OF THE INVENTION 
     A single pole, double throw thermostatic switch includes a single switchblade being a resilient mounting arm integral with a resilient switchblade. The mounting arm is both twisted and bent by a fulcrum in the switchcase and this, in turn, bends the switch arm for normally closing one pair of contacts while opening the other contact pair. A plunger operated by a snap disc shifts the fulcrum point to twist the mounting arm in an opposite direction and bend the switchblade in an opposite direction to open the one contact pair while closing the other contact pair. 
     It is a principal object of the present invention to provide an improved single pole, double throw thermostatic switch having a one-piece resilient switchblade that includes a resilient mounting arm integral with a switchblade. 
     It is another object of the invention to provide an improved one-piece switchblade for use in switches. 
     It is a further object of the invention to provide a single pole, double throw thermostatic switch that has a minimum number of parts, and is easy to manufacture and assemble. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a top plan view of a single pole, double throw thermostatic switch constructed in accordance with the present application; 
     FIG. 2 is a cross-sectional elevational view thereof; 
     FIG. 3 is a view similar to FIG. 2 and showing the switchblade in its alternative operating position; and 
     FIG. 4 is a top plan view similar to FIG. 1 and showing an alternative configuration for the switchblade. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawing, wherein the showings are for purposes of illustrating certain preferred embodiments of the invention only and not for purposes of limiting same, FIG. 1 shows a thermostat assembly A having a plastic switchcase B and a metal disc cup C. Terminals 10, 11, and 12 are attached to switchcase B by suitable fasteners such as rivets 14, 15, and 16. 
     Terminals 10 and 12 have fixed contacts 20, 22 located within switchcase B. Switchcase cover plate 24 in FIG. 2 is removed in FIG. 1 for viewing the interior of the switchcase and to show one-piece resilient switchplate D. 
     Switchplate D includes an elongated flat and resilient mounting arm 30 integral with a transversely extending resilient switchblade 32 carrying movable contacts 36, 38 on its opposite end portions. Arm 30 is secured to switchcase B by rivet 15 beneath terminal 11 at a securement location. 
     A fulcrum 40 within switchcase B is positioned for bending mounting arm 30 upwardly and also twisting same counterclockwise in FIG. 2 for bending switch arm 32 into the configuration shown in FIG. 2 with contacts 20, 36 closed and contacts 22, 38 open. 
     A bi-metal disc 44 within disc cup C cooperates with a reciprocating plunger 46. When a predetermined temperature is reached, bi-metal disc 44 snaps from the position shown in FIG. 2 to the reverse configuration shown in FIG. 3 to move plunger 46 upwardly. This changes the fulcrum point because the plunger 46 now becomes the fulcrum rather than fulcrum projection 40 on switchcase B. Shifting of the fulcrum point still bends mounting arm 30 upwardly but imparts a twist thereto in a clockwise direction for imparting a reverse bend to switchblade 32 which then assumes the configuration shown in FIG. 3 with contacts 20, 36 open and contacts 22, 38 closed. 
     FIG. 4 shows another arrangement for the one-piece switchplate. The switchcase cover plate is removed in FIG. 4 to show switchplate E having a flat and resilient mounting arm 50 extending at an acute angle to a flat and resilient switchblade 52 rather than substantially perpendicular thereto as in the arrangement of FIGS. 1-3. Switchcase fulcrum point 40 is indicated in FIG. 4 as is the fulcrum point provided by plunger 46. The arrangement of FIG. 4 works in the same manner as described with respect to the embodiment of FIGS. 1-3. Obviously, many other shapes may be provided for the one-piece switchplate. The important considerations are that the mounting arm be upwardly stressed and twisted in one direction when it is assembled, and that the same upward bending but reverse twist be provided by shifting the fulcrum point to the plunger when the bi-metal disc reverses position. 
     In the arrangement of FIGS. 1-3, mounting arm 30 is integrally connected with switchblade 32 intermediate the opposite ends of switchblade 32. In the preferred arrangement, mounting arm 30 is located substantially closer to one end of switchblade 32 than the other end thereof. The embodiment of FIGS. 1-3 has mounting arm 30 extending substantially perpendicular to switchblade 32 while in the arrangement of FIG. 4 mounting arm 50 extends from switchblade 52 at an angle substantially less than 90°. 
     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such equivalent alterations and modifications, and is limited only by the scope of the claims.