Abstract:
A lever operated rotary reversing switch wherein a lever is snap-fit attached to the switch housing with a portion of the lever inserted under an overhang on the housing to maintain that portion of the lever against the exterior surface. A detent is provided between the overhang and the end of the lever to direct the forces longitudinally in the plane of the lever. A rotor plate located exteriorly of the housing is connected to the rotor by an axial shaft, and an eccentric received in a slot in the lever for providing a driving coupling between the lever and internal contact mechanism is located on the exterior surface of the rotor plate.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to lever operated electric switches wherein pivotal movement of a lever operates switching contacts within a switch housing. More particularly, this invention relates to an improvement of the lever operator arrangement for a rotary switch of the type used to reverse the polarity of electric power at the output terminals of the switch. Switches of this type are commonly referred to as reversing switches and are used in controls for portable electric tools. 
     Reversing switches may be constructed as an integral part of a portable tool trigger switch or may be a discrete switch unit mounted on the top of a trigger switch. The reversing switch contact mechanism is commonly a rotary mechanism, although the lever operator system of this invention could be employed to operate a reciprocating slide switch. The contact mechanism commonly has an eccentric portion of the movable contact carrier projecting within or through an arcuate slot in the switch housing for engagement by the lever operator. The lever is pivotally mounted to the switch housing, commonly by a rivet that is also used to attach the reversing switch to the trigger switch. Such arrangement significantly complicates the assembly procedure. The portion of the lever that engages the movable contact carrier eccentric may deflect away from the reversing switch housing, reducing the efficiency of the engagement with the movable contact carrier. Moreover, deflection of the lever away from the switch housing uncovers the slot through which connection with the movable contact carrier is effected, increasing the chances for foreign matter to enter the switch. Detent mechanisms for the lever comprising spring loaded balls in the housing or protuberances on the housing or lever cooperating with recesses in the opposite member also tend to deflect the lever away from the switch housing surface, uncovering the slot and rendering the switch more susceptible to the entry of foreign matter through the slot. 
     SUMMARY OF THE INVENTION 
     This invention provides a lever operated electric switch wherein the housing is provided with an overhang and the lever is snapped into pivotable attachment to the housing, a portion of the lever being inserted under the overhang to maintain the lever slidably disposed against the housing. The overhang and a distal end of the lever portion cooperate to provide a detent that generates forces directed in the plane of the lever. A rotary contact mechanism includes an eccentric located externally of the switch housing on a rotor plate that attaches to a projecting axial shaft of the internal rotor. The rotor plate is significantly larger in diameter than is a hole in the housing for the rotor shaft to provide improved sealing against ingress of foreign matter through the hole for the contact mechanism-to-lever connection. 
     The invention, its advantages and features will become more readily apparent when reading the following description and appended claims in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a lever operated electric switch constructed in accordance with this invention; 
     FIG. 2 is a partial top plan view of an alternate embodiment of the lever operated electric switch of this invention. 
     FIG. 3 is a top view of the switch base and stationary contacts with the cover and rotor removed; and 
     FIG. 4 is a cross sectional view taken generally along line 4--4 in FIG. 1 and drawn to an enlarged scale. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A discrete lever operated electric switch 2 is shown as viewed from the top in FIG. 1. Switch 2 is a rotary switch operable to reverse the polarity of current flow at the output terminals relative to the input terminals. With reference also to FIGS. 3 and 4, switch 2 has an insulating housing comprising a molded insulating base 4 and a molded insulating cover 6. Tabs 6a depend from cover 6 at the opposite ends and have rectangular openings 6b therein to resiliently snap over projections 4a on base 4 to secure cover 6 to base 4. Tabs 6a are part of respective end walls of cover 6 that close the open ends of base 4. 
     As seen in FIG. 3, base 4 comprises a cylindrical cavity 4b into which four L-shaped stationary contacts 10, 12, 14 and 16 are inserted from the open ends of the base 4 prior to attachment of cover 6. The stationary contacts are disposed within recesses in the bottom of base 4 and project through slots 4c (FIG. 4) at the bottom of the arcuate wall surrounding cylindrical cavity 4b. Flexible wire retention clips 18 are inserted within narrow slots in base 4 as seen in FIG. 2 and are deflected against the respective upstanding legs of stationary contacts 10-16. Openings 4d are provided at each end of the sidewalls of base 4 through which wires from an electric power source and an electric motor may be inserted. The bared ends of such wires are inserted between retention clips 18 and the respective upstanding legs of the stationary contacts in a well known manner to connect the switch 2 in an electric circuit. 
     A cylindrical rotor 20 molded of insulating material is disposed within cylindrical cavity 4b as seen in FIG. 3. Rotor 20 has a pair of slots 20a (only one shown, FIG. 4) which receive movable U-shaped bridging contacts 22, each biased outwardly of the respective slot toward the bottom of base 4 by a respective helical compression spring 24 disposed within a blind hole 20b. The legs of bridging contacts 22 converge at the outer ends. The sidewalls of slots 20a are angularly offset generally parallel to the legs of contacts 22. The movable bridging contacts 22 are forced over the wider lower end of the rotor and are retained so assembled to the rotor by the convergence of the legs. The lower surface of each bridging contact 22 is dimpled downward near the opposite ends to form bosses 22a which engage the surface of stationary contacts 10-16. 
     Cover 6 has a shallow cylindrical recess 6c in the exterior surface axially aligned with cavity 4b, and an opening 6d through the cover on the axis of recess 6c. A flatted shaft 20c of rotor 20 projects axially upward through opening 6d above the exterior surface of cover 6. A rotor plate 26 having a central opening 26a shaped complementally to shaft 20c is disposed over shaft 20c to be non-rotatably attached to rotor 20. It will be noted that plate 26 is significantly larger in diameter than opening 6d, and therefore the opening 6d is well covered and protected against the passage of foreign material therethrough into the switch. 
     A boss 26c, located eccentrically near the periphery of rotor plate 26, extends upwardly from the upper surface of rotor plate 26 to provide a drive connection for the contact mechanism rotor 20. A post 6f extends upwardly from the exterior surface of cover 6 near the right-hand end of the cover as oriented in the drawings. A hole 6g extends through the post 6f and cover 6 in alignment with a hole 4e in base 4 to provide a mounting hole for the switch. A second mounting hole is provided at the other end of the switch by aligned holes 6h and 4f in the cover and base, respectively. An operating lever 30 is pivotably attached to switch 2 by a hole 30a, located between the ends of the lever, being disposed over post 6f. The post is provided with a raised semicircular rib 6j to provide an interference fit between post 6f and hole 30a. Forcing lever 30 onto the cover 6 forces hole 30a over post 6f with a snap fit to secure the lever 30 the cover 6. It is contemplated that other well known snap-on attachment structures could be employed to attach lever 30 to cover 6, e.g. a resilient catch extending axially on the post. The post also could be located on the lever and the hole located in cover 6. 
     Lever 30 has an elongated opening 30b near its left-hand end portion as oriented in the drawings. Opening 30b is disposed over boss 26c and forms a driving connection between operator lever 30 and rotor 20. As operator lever 30 is pivotally moved clockwise or counterclockwise about post 6f in the direction of arrow 32 (FIG. 1) the lever drives rotor plate 26 and rotor 20 clockwise or counterclockwise to effect switching of movable contacts 22 upon stationary contacts 10-16. A pair of stops 6k are integrally molded on cover 6 to provide limits to the pivotal movement of lever 30. 
     An overhang 6m is provided on cover 6. Overhang 6m is preferably integrally molded on cover 6 and comprises a cross member 6n supported at opposite ends by abutments 6p. The distal end of lever 30 is stepped to provide a projecting lip 30c which is inserted under cross member 6n during attachment of the lever to the cover. The overhang retains lever 30 against the exterior surface of cover 6 in good driving engagement with eccentric boss 26c and tightly covering opening 6d. The end of lever 30 above lip 30c has either a V-shaped groove 30d (FIG. 1) or an arcuate surface 30e (FIG. 2) which cooperates with a resilient projection 6q on cross member 6n to provide a detent for lever 30. The force of detent 6q-30d is directed in the plane of lever 30 parallel to the top surface of the cover 6 and therefore does not tend to deflect lever 30 away from the exterior surface of cover 6. The V-shaped groove 30d provides a center position for lever 30 and the curvature of the end of lever 30 cooperates with outer peaks of the groove 30d to provide left and right detented positions for the lever, maintaining it against the respective stops 6k. The arcuate surface 30e (FIG. 2) cooperates with the same resilient projection 6q to provide a two-position operation. 
     The foregoing has described a preferred embodiment of the improved operating lever arrangement of this invention. However, it is to be understood that the invention is susceptible to various modifications and embodiments without departing from the appended claims. By way of example, the overhang may be a non-resilient member having a slot facing pivot post 6f. The overhang may be a separate member as opposed to being an integral element of the cover, or it may be an inter-engaging structure on the lever and cover that permits sliding movement, but blocks movement of the lever away from the surface of the switch housing. Moreover, the overhang 6m could be arranged to extend over the upper surface of lever 30 as opposed to over the projecting lip 30c at the end of the lever and that the inclusion of the detent is optional.