Patent Publication Number: US-4149049-A

Title: Switch using resilient annular contactor

Description:
BACKGROUND OF THE INVENTION 
     Snap action switches utilizing stored energy of resilient biasing means is known. Switches utilizing resilient loops to effect switching operations are also known. While these switches have been useful for their intended purposes, the present invention relates to improvements thereover. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved snap action electric switch. 
     Another object is to provide a simple, low cost switch of the aforementioned character with a minimum number of parts. 
     Another object is to provide a switch of the aforementioned character which torsionally shears contact welds. 
     Another object is to provide a switch of the aforementioned character having a closed-loop resilient contactor which acts as both a snap action overcenter blasing means and as a movable contact. 
     Another object is to provide a switch of the aforementioned character wherein the contactor is freely trapped in a cavity in the switch housing whereby the contactor is neither mounted to the switch housing nor to a movable operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-4 show a cross-sectional view of a switch constructed in accordance with the invention, and sequentially illustrate operation thereof. 
     FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     There is shown in FIG. 1 an electric switch having a housing comprising an open-topped insulating base 2 covered by a cover 4 having a threaded bushing 6 extending upwardly therefrom away from base 2. Pivotally mounted in the bushing is a toggle lever 8 which extends into the interior of the housing. 
     Three terminals 10, 12 and 14 extend from below the housing, up through the bottom 2a of the base and then into the interior of the housing. Central terminal 12 is a common terminal and its portion 12a inside the housing is flat and horizontal, lying against the interior bottom of the base. Left and right terminals 10 and 14 have central horizontal portions 10a and 14a extending along the interior bottom of the base and vertical upstanding portions 10b and 14b within the housing. 
     These terminals form a cavity in the switch housing, such cavity having a bottom horizontal wall defined by terminal portion 12a and base bottom 2a, a left vertical wall defined by terminal portion 10b, and a right vertical wall defined by terminal portion 14b. Also defined in the cavity are front and rear walls 2b and 2c, respectively, FIG. 5, of the base. 
     Freely trapped in the cavity is an annular elastic metal contactor 16. The diameter of contactor 16 is less than the distance between terminal portions 10b and 14b. The toggle lever has a lower camming portion 8a which, during pivotal movement of the toggle lever, defines a line of travel which is spaced from terminal portion 12a a distance less than the diameter of contactor 16. 
     Operation of the switch can now be described. Referring to FIG. 1, it is seen that with toggle lever 8 in a fully clockwise pivoted position, camming portion 8a is left of center of contactor 16 which is held in a slightly compressed state so as to afford sufficient bias to ensure firm contact with terminal portions 12a and 14b, thus completing a circuit therebetween. As the toggle lever is pivoted counterclockwise, FIG. 2, cam portion 8a moves rightwardly, cammingly compressing and deforming contactor 16. Deformation of contactor 16 at surfaces 12a and 14b torsionally shears contact welds therebetween. Continued counterclockwise pivoting of the toggle lever causes further deformation of contactor 16 until an overcenter position is reached, FIG. 3, after which the energy stored in the contactor during deformation thereof is released and the contactor snaps leftwardly against terminal portion 10b, FIG. 4, to complete a circuit between terminals 12 and 10. 
     Contact force increases prior to break because of the increasing deformation of the contactor, to thus assure a crisp unfluttering break and prevent teasing of the contacts. Cleaning and wiping of common terminal portion 12a is provided by the effective rolling thereacross of contactor 16. Due to the resilient deformation of contactor 16, there is afforded a torsional shearing effect between the contactor and terminal portions 10b, 12a and 14b to thus break contact welds, frictional attachments, etc., and hence prevent hang-up of the switch. 
     The retention cavity in which the contactor is trapped may have other forms than shown in the preferred embodiment. For example, the left and right vertical side walls 2d and 2e may comprise the left and right cavity walls against which the contactor is snapped, with different dimensioning of the switch, wherein stationary contact means may be mounted at one or both of the walls 2d and 2e. Generally, the means which form the cavity should: (a) provide a distance between the left and right cavity walls which is greater than the diameter of the contactor to afford engagement of only one cavity side wall at a time, to thus permit a switching function to be performed; and (b) provide a distance between the bottom cavity wall and at least a segment of the line of travel of the camming portion of the actuator which is less than the diameter of the contactor to ensure deformation of the contactor upon movement of the actuator through an overcenter condition to afford a change of position of the contactor. The cavity thus permits the contactor to be freely trapped therein without being mounted to the actuator or the base. 
     The contactor is preferably made of a soft metal having good electrical conductivity, such as copper. A closed-loop band, preferably in the shape of an annulus, is formed in order to provide resiliency to the contactor. This elastic configuration allows energy to be stored in the contactor upon deformation, which energy is released upon return of the contactor to its normal configuration, thus enabling the contactor to act both as biasing means and as a movable contact. 
     Though a double throw, single pole switch is shown, other embodiments are possible. For example, front and rear stationary contacts may be disposed at the right side wall of the cavity to be bridged by the contactor in the position shown in FIG. 1, with the remaining stationary contacts being eliminated or unused to thus afford a single throw, single pole switch, with the off condition shown in FIG. 4. As another example, front and rear stationary contacts may be disposed on both the right side wall and on the bottom wall of the cavity to afford a single throw, double pole switch wherein the contactor bridges a bottom contact and a respective right side contact in an on condition shown in FIG. 1; front and rear stationary contacts could also be disposed on the left side wall of the cavity to provide a double throw, double pole switch. 
     The invention is also susceptible of other types of actuators, for example, a left-right linearly reciprocal actuator having a downwardly extending V-shaped cam which engages the contactor. 
     It is recognized that various modifications are possible within the scope of the appended claims.