Abstract:
A single-pole single-throw electric switch having a fewer number of simple parts more easily adapted for automatic assembly, and having a low base height due to a leaf spring biased roller contact actuated by a double-incline apex on the operating lever movable overcenter on the roller contact to snap it into or out of bridging engagement with a pair of stationary contacts. A single insulating plate held in vertical grooves in opposite walls of an open-top base retains in place a pair of press-in lead leaf-spring connectors and also supports the stationary contacts in place up against the cover, the terminal portions of which are retained by their opposite edges in spaced vertical grooves in opposite walls of a pair of terminal compartments in the base. The arrangement is such that all the parts can be lowered down into the base in predetermined order thereby affording automatic assembly. The switch is operable by any one of a number of different types of operating levers such as a toggle lever, a trigger, a slide button, a push-push button, or the like, provided the cover is suitably configured to accommodate the desired operating lever, and is adapted for use with any one of a number of different types of connectors such as push-in lead, screw terminal or solder lug.

Description:
BACKGROUND OF THE INVENTION 
     Switches of the type wherein relative motion between a sliding or rolling member and the high point or apex of a double-incline cam is used to attain snap-action contact operation have been known heretofore. But switches of that type have had disadvantages in that they have been rather complicated in construction with a large member of parts that were comparatively difficult to assemble thereby keeping the costs of manufacture rather high. Thus, it has been found desirable to provide a switch that overcomes these disadvantages. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved electric switch. 
     Another object of the invention is to provide an improved electric switch of the snap-action type having a fewer number of parts. 
     Another object of the invention is to provide an improved snap-action electric switch having fewer parts of simpler construction providing a low base height. 
     Another object of the invention is to provide an improved electric switch of simple construction that is adapted for use with any one of a variety of different actuators. 
     Another object of the invention is to provide an improved electric switch of simple construction that is readily adaptable to automated assembly. 
     Other objects and advantages of the invention will hereinafter appear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged side view, partly in section, of a snap-action switch of the roller contact type taken substantially along line 1--1 of FIG. 3 to show the contact arrangement and leaf spring within the base; 
     FIG. 2 is a horizontal cross-sectional view taken substantially along line 2--2 of FIG. 1 to show a top view of the bridging contacts; 
     FIG. 3 is a vertical cross-sectional view taken substantially along line 3--3 of FIG. 1 to show the insulating retainer plate; 
     FIG. 4 is a top view of the cover of the switch of FIG. 1 showing the bushing bore configuration into which the toggle lever is snap-in assembled; 
     FIG. 5 is a fragmentary side elevational view, partly in section, of the switch of FIGS. 1-4 showing an alternative connector means for connecting the stationary contacts through short wires to an external circuit; 
     FIG. 6 is a view like FIG. 5 showing another alternative connector means affording bottom or end screw terminals for connecting the stationary contacts to an external circuit; and 
     FIG. 7 is a view like FIG. 5 showing a further alternative connector means attained by substituting different stationary contacts to afford solder lugs for connecting the stationary contacts to an external circuit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-3, there is shown a snap-action switch of the roller contact type constructed in accordance with the invention. As shown therein, this switch is provided with a housing including an insulating, molded plastic, open-top base 2 and an insulating, molded plastic cover 4 closing the top of the base and having an integral upstanding bushing 6 thereon. An actuator in the form of a toggle lever 8 is snap-in mounted in the bushing for limited pivotal movement to operate the contacts as hereinafter described. 
     Base 2 is provided with a switch compartment including a contact compartment 2a substantially centrally thereof and two connector compartments 2b and 2c at its left-hand end separated by a wall 2d as shown in FIGS. 1 and 2. Two generally T-shaped apertures or holes 2e and 2f in the bottom of the left-hand end of the base, as shown in FIGS. 1 and 2, provide access for inserting electrical conductors into connector compartments 2b and 2c, respectively. As shown in FIG. 1, the bottom of the base is provided with generally rectangular recesses such as 2e&#39; around the largest portion of these holes to provide clearance for the insulation of the conductor that is inserted therethrough. 
     Vertically extending ridges 2g in opposite side walls of connector compartment 2b provide vertical grooves between these ridges and the left end wall of the base for retaining terminal portion 10a of one stationary contact 10 as shown in FIGS. 1 and 2. Similar vertically extending ridges 2h in opposite side walls of connector compartment 2c provide vertical grooves between these ridges and the left end wall of the base for retaining the opposite edges of terminal portion 12a of a second stationary contact 12 as shown in FIGS. 1 and 2. As shown in FIG. 1, each stationary contact is a flat strip element having two bends to provide a vertical terminal portion such as 10a, a horizontal intermediate portion and a downwardly angled contact portion such as 10b. These stationary contacts are also provided with generally oblong holes 10c and 12c at the bend between their terminal and intermediate portions as shown in FIG. 2 for entry of alternative connector means hereinafter described in connection with FIGS. 5 and 6. For this purpose, the base is provided with a pair of rectangular apertures or holes 2j and 2k in registration with the respective holes in the stationary contacts for entry of such connector means. These holes 2j and 2k are in the form of slots extending down from the upper edge of the left end wall of the base. 
     These stationary contacts 10 and 12 extend upwardly along the left end wall of the base as shown in FIG. 1, with their edges held in the aforesaid grooves as shown in broken lines in FIG. 2, up to the top of the base and then toward the right along the lower surface of cover 4 into contact compartment 2a, and then downwardly along the left side of contact compartment 2a with a small rightward angle as shown in FIG. 1 to provide stationary contact portions 10b and 12b within the left side of the contact compartment. 
     Means is provided to retain the contact portions 10b and 12b of these stationary contacts in place within the base. This means comprises a generally inverted U-shaped insulating retainer plate 14 of fibre board or the like held by its side edges in a pair of vertical grooves in the side walls of the base as shown in FIGS. 1, 2 and 3. Legs 14a and 14b of this retainer plate press down on wire clamps 16 and 18, respectively, to hold them in place with their left ends pressed against terminal portions 10a and 12a of the stationary contacts as shown in FIGS. 1 through 3. 
     As shown in FIG. 1, wire clamp 16 is a rectangular piece of steel sheet having one end held in a corner of recess 2m in the bottom of the base below the contact compartment and it inclines or extends leftward at an upward angle therefrom past the end of leg 14a of the retainer plate and has its other end pressed against terminal portion 10a. Wire clamp 18 is similarly trapped at one end in a similar recess 2n, FIG. 3, at the other side of the bottom of the base and extends leftward at an upward angle so that its other end is pressed against terminal portion 12a. In this manner, stiff bare conductors inserted up through the cross portions of T-shaped holes 2e and 2f are slid between each wire clamp and the associated terminal portion to make an electrical connection to an external circuit. The leg portions of these T-shaped holes provide clearance for a probe to release these wire clamps. 
     Retainer plate 14 has a central lug 14c on its upper edge as shown in FIG. 3 that is shorter vertically than the thickness of stationary contacts 10 and 12 so as to retain these contact-terminals suitably spaced apart and up against the lower surface of cover 4. The spring force from wire clamps 16 and 18 upwardly onto legs 14a and 14b resiliently holds the retainer plate pressed up against the stationary contacts. 
     A movable contact 20 is supported in the contact compartment by a leaf spring 22. This movable contact is of the elongated rotary or roller contact type having a cylindrical form and flat ends such as a piece of copper tube extending between and guided by the flat side walls of the base as shown in FIGS. 1 and 2. Spring 22 comprises two stacked rectangular strips of stainless steel or the like supported at its ends in the base. For this purpose, the left and right end walls of the contact compartments are provided with recesses or slots 2p and 2q, recess 2p being in dividing wall 2d. 
     The bottoms of these recesses are provided with round-top ridges 2r and 4s, respectively, inclined toward the bottom of the contact compartment for supporting the opposite ends of spring 22. Also the bottoms of these recesses and the ridges thereon are spaced equally above the bottom of the contact compartment to allow the center of the spring to dip down when the switch is actuated. Recesses 2p and 2q are open to the top of the base to allow dropping of spring 22 into place. 
     In order to secure the cover to the base, the base is provided with two blind holes 2t and 2u extending partway down from the top. As shown in FIG. 2, hole 2t extends down into dividing wall 2d and hole 2u extends down into the solid portion between recess 2q and the right-hand end of the base. The cover is secured to the base by two drive screws inserted through holes in the cover and driven into these holes 2t and 2u in the base. 
     As shown in FIG. 4, cover 4 is provided with two recesses 4a and 4b in its upper surface and holes 4c and 4d extending from the respective recesses through the cover in alignment with blind holes 2t and 2u in the base. Recesses 4a and 4b provide clearance for the drive screw heads so that the cover can be placed flat against a mounting panel when the switch is installed. 
     Bushing 6 which is molded integrally with the cover is provided with an external thread 6a onto which a mounting nut may be threaded after the bushing has been inserted through a hole in a mounting panel to secure the switch to the panel. This bushing is also provided with means for snap-in mounting a toggle lever 8. For this purpose, the bushing is provided with a socket 6b at its upper portion and a flat or oblong hole 6c extending from this socket down through the bushing and cover as shown in FIGS. 3 and 4. As shown in FIG. 3, this socket is partial-spherical and has a constriction 6d adjacent the top of the bushing past which spherical intermediate portion 8a of the toggle lever must be pressed to enter the socket with the round handle portion remaining on the outside above the bushing. The bushing is of plastic material and sufficiently resilient to allow the toggle lever ball to be snapped past this interfering constriction into the socket. A bevel 6e at the mouth of the socket facilitates guiding the toggle lever ball into the socket. 
     A pair of lateral, vertical grooves 6f and 6g extend down along opposite sides of socket 6b as shown in FIGS. 3 and 4 for receiving integrally molded short trunnions 8b on opposite sides of spherical portion 8a of the toggle lever. As shown in FIG. 4, these grooves 6f and 6g are on a line perpendicular to the long dimension of flat hole 6c so that the toggle lever trunnions will be journaled at the lower ends of these grooves to keep the toggle lever from rotating on its longitudinal axis while the flat lower end portion of the toggle lever swings in correspondingly flat hole 6c. The toggle lever pivots in the socket as well as on trunnions 8b shown in dotted lines in FIG. 1. 
     To close the switch, the toggle lever is pivoted counterclockwise from the position shown in FIG. 1. As a result, apex 8c at the lower end of the toggle lever slides over roller contact 20, depressing this roller contact and stressing spring 22. As soon as the apex of the toggle lever has passed over the high point on the upper curvature or convex surface of roller contact 20, the roller contact snaps toward the left under the reactive force of spring 22 into bridging engagement with stationary contacts 10b and 12b. 
     The lower end of the toggle lever is provided with two pairs of angular surfaces. The first pair of these angular surfaces 8d join to form the apex 8c and have small relative angles such as to ease the movement of the toggle lever apex over the movable roller contact. The other angular surfaces 8e on opposite sides of the first pair have steeper relative angles such as to provide the movable contact with the required contact pressure against the stationary contacts when the contacts are closed. As will be apparent, the toggle lever is symmetrical so that it can be inserted in the socket as shown in FIG. 1 or 180 degress turned from that position. 
     It will be apparent that the switch can be adapted to automated assembly. For this purpose, wire clamps 16 and 18 are first dropped down into the switch compartment with their right hand ends in recesses 2m and 2n. Next, probes are inserted through holes 2e and 2f to hold the other ends of these wire clamps out of the way for insertion of the stationary contacts which are not inserted yet. Then, the two stacked strips constituting leaf spring 22 are dropped into the switch compartment with their ends in slots 2p and 2q. Or, of course, these strips can be dropped in before the aforesaid probes are inserted. Then, retainer plate 14 is dropped or inserted into the base with its edges sliding down grooves in the walls of the base shown in FIG. 2. Next, the two stationary contacts are dropped or inserted into the switch compartment with their terminal portions sliding down the pairs of grooves in the walls of the connector compartments. Then, movable contact 20 is dropped into the contact compartment, coming to rest on spring 22. Then, the toggle lever is snapped into the bushing and the cover is placed over the base and the two drive screws are inserted through the holes in the cover and driven into the blind holes in the base to complete assembly of the switch. 
     The alternative connector means shown in FIG. 5 uses short conductors rather than the wire clamps of FIG. 1. A pair of short conductors such as 24 in FIG. 5 have the insulation stripped from both ends and first ends thereof are inserted through holes 10c and 12c in the stationary contacts and secured by soldering or welding to the lower surfaces of the horizontal intermediate portions of the stationary contacts. This is done beforehand so that when the stationary contacts are assembled into the base, slots 2j and 2k provide clearance for these conductors as shown in FIG. 5. Also, wire clamps 16 and 18 may be omitted in FIG. 5. The other ends of these conductors such as 24 may then be connected by speed nuts to an external circuit. 
     FIG. 6 shows another alternative connector means providing screw terminals at the bottom of the base and a variation thereof in broken lines providing the screw terminals alternatively at the end of the base. The switch structure in FIG. 6 is like that in FIGS. 1-4 with the addition that the narrow stems such as 26a of a pair of screw terminals such as 26 are inserted up through bottom holes 2e and 2f of the base to be gripped between the wire clamps and the terminal portions of the stationary contacts. Screws such as 26b may then be used to connect the stationary contacts to an external circuit. These wire clamps will grip these screw terminals in a similar manner as they would grip stripped ends of insulated wires in FIGS. 1-4. 
     If it is desired to have these screw terminals at the end of the base rather than at the bottom due to space limitations adjacent the bottom of the switch within the tool or appliance into which it is mounted, this can be readily done as shown in broken lines in FIG. 6. For this purpose, the stems 26a&#39; of screw terminals 26&#39; are secured to the stationary contacts before assembly in the manner of wires 24 in FIG. 5. 
     FIG. 7 shows a further alternative connector means providing solder lugs at the bottom of the base. For this purpose, modified stationary contacts such as 28 are used. These modified stationary contacts are like those in FIGS. 1-6 except that their terminal portions are provided with integral, narrower, offset extensions 28a having oblong holes 28b therein as indicated in FIG. 4 providing solder lugs. These extensions are long enough to extend out through the bottom holes 2e and 2f of the base and are offset so that they will line up with the holes in the bottom of the base as shown in FIG. 7. The stripped ends of wires may be inserted through holes 28b, bent around these extensions and soldered thereto to connect the stationary contacts to an external circuit. 
     It will be apparent from the foregoing description of the alternative connector means that these can be provided for with minimum addition or substitution of parts and requires no modification of the base. 
     While a toggle lever has been shown as an actuator in FIG. 1, it will be apparent that other actuators such as a slide button, a rocker button or a slidable trigger could also be used in place thereof by substituting a cover suitably modified to provide for mounting and movement thereof. A push-push actuator could also be used such as the actuator shown in A. W. Krieger U.S. Pat. No. 2,295,484, dated Sept. 8, 1942, provided actuating element 19 thereof were given the double-incline apex form used in the present toggle lever. 
     While the apparatus hereinabove described is effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiments of snap-action switch of the roller contact type disclosed, inasmuch as they are susceptible of various modifications without departing from the scope of the appended claims.