Abstract:
A cylindrical contact carrier (4) is journaled for rotational movement about an axis extending in the direction of linear movement of a depressible trigger operator (2). Spiral grooves (4d) formed in the carrier (4) cooperably receive cam elements (10g) which are disposed in fixed planes with respect to the axis of rotation and depression of the trigger operator (2) effects relative linear movement of the cam elements (10g) with respect to the spiral grooves (4d) to cause rotation of the carrier (4) for moving contacts (18) positioned on the carrier (4) into and out of engagement with stationary contacts (22) disposed around the periphery of the carrier (4).

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to trigger operated electric switches adapted for use in hand held portable tools. More particularly, the invention relates to a switch of the aforementioned type wherein the trigger is linearly depressible from an extended position and depression thereof effects rotational movement of a contact carrier member. 
     In providing switching contact actions for switches of the aforementioned type, it is often difficult in view of the compactness of the switch design to provide adequate electrical clearance between the movable and stationary contacts when the switch is in the off position. It is also desirable to provide significant wiping action of the movable contacts upon the stationary contacts when making and breaking the electrical connections therebetween. The nature of the application or utilization of such switches in portable electric tools dictates that the operator be a depressible member commonly controlled by the forefinger of the hand which holds the tool. In previous switch designs the operator movement has typically provided linear movement for contact actuation. 
     SUMMARY OF THE INVENTION 
     The invention described herein provides a trigger operated electric switch which is adapted for use in a hand held portable tool and which comprises a housing having stationary contacts disposed therein, a linearly depressible trigger extending from the housing and biased to an extended position, a contact carrier having movable contacts positioned thereon, the carrier being disposed within the housing and mounted for rotation about an axis extending in the direction of linear depression of the trigger, and drive means responsive to depression of the trigger for effecting rotational movement of the contact carrier to move the movable contacts into bridging engagement with the stationary contacts. 
     The invention and its advantages will be more readily understood in the following description and claims when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal cross sectional view of a switch constructed in accordance with this invention; 
     FIG. 2 is a transverse cross sectional view of the switch of this invention taken along the line 2--2 in FIG. 1; and 
     FIG. 3 is an exploded isometric view of the switch of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, the switch of this invention comprises a trigger operator 2 having a contact carrier 4 rotatably mounted thereon which is housed within an insulating housing assembly 6 comprising a molded insulating frame 8, a pair of identical mold insulating base halves 10, and an insulating spacer 12. Trigger 2 is molded of insulating material and has a shaft 2a extending rearwardly thereof, the outermost end of the shaft 2a having a cylindrical recess formed therein. Immediately below the shaft 2a the trigger 2 is provided with a cylindrical recess 2b, the axial direction of the recess 2b being substantially parallel to the axial direction of the shaft 2a. Contact carrier 4 is a cylindrical member having a cylindrical recess 4a extending from the right-hand end thereof as viewed in the drawings and a second, reduced diameter cylindrical recess 4b therein extending from the left-hand end as viewed in the drawings, the recesses 4a and 4b communicating to provide a stepped shouldered surface within the carrier 4. The latter is assembled to trigger 2 by positioning the recess 4b over the shaft 2a of the trigger and turning over the cylindrical outer end portion of shaft 2a upon the internal shouldered surface formed by the juncture of recesses 4a and 4b within the contact carrier 4. Preferably, a bearing member 14 is disposed over shaft 2a between the rear face of the trigger 2 and the left-hand end of contact carrier 4 and a flat cylindrical washer 16 is positioned over the shaft 2a within the recess 4a to be disposed between the shouldered surface of the contact carrier 4 and the turned over end of shaft 2a. 
     The external surface of cylindrical contact carrier 4 is provided with a pair of recesses 4c (only one of which is shown in FIG. 3) for receiving movable contact members 18 therein. A pair of leaf springs 20 are disposed within the recess 4c under the opposite ends of each movable contact 18. The external surface of contact carrier 4 is also provided with a pair of spiral grooves 4d for reasons that will be described hereinafter. 
     The insulating base halves 10 have a substantially half-cylindrical recess 10a formed along their interior surface near the upper edge thereof. The interior surface of each base half is also provided with recessed portions 10b which receive complementally formed stationary contacts 22 therein. Pockets 10c are formed below each of the recesses 10b, the pockets 10c having openings through the bottom wall of the base through which electric wires may be inserted to make electric connection to the switch. To this end, each pocket 10c receives a V-shaped wire terminal clip 24 which is positioned within the pocket to force a wire conductor against the stationary contact 22 when such conductor is inserted as shown in dotted lines in FIG. 2. Each base half is provided with a projection 10d and recess 10e along the upper edge thereof for engagement by the respective opposite projection and recess of the other base halve when assembled to thereby aid in positioning the two base halves together. Each base half is also provided with a pair of projections 10f near the lower edge thereof which project into openings 12a in the insulator 12 to position the insulator with respect to the base halves. A cylindrical projection 10g is formed in each base half within the cylindrical recess area 10a. The projections 10g cooperate with the spiral grooves 4d in the contact carrier 4 when the switch is assembled as will be more fully described hereinafter. 
     The insulating spacer 12 has a cylindrically recessed upper surface 12b which is shaped complementally to the cylindrical shape of contact carrier 4. The left-hand end of insulator 12 is provided with a rectangular flange 12c which in turn is provided with an outwardly projecting cylindrical boss 12d. A helical compression spring 26 is provided to be received within the recess 4a of the contact carrier to bear between the projecting end of shaft 2a of trigger 2 and an interior end wall of housing frame 8 when the switch is assembled to bias the trigger 2 and contact carrier 4 to an extended position with respect to the housing. 
     To assemble the switch, the contact clips 24 and stationary contacts 22 are assembled to the respective base halves 10 as aforedescribed. The assembly comprising trigger 2 and contact carrier 4, having movable contacts 18 and their respective leaf springs 20 assembled thereto, is disposed within the cylindrical recessed area 10a of one of the base halves such that a respective spiral groove 4d is engaged over a projection 10g. The insulating spacer 12 is then positioned along the bottom side of the cylindrical contact carrier 4 such that the latter rests within the dished cylindrical surface 12b of the spacer, and the projections 10f of the base half 10 are received within the recesses 12a of the insulating spacer 12. The opposite base half is then assembled over the contact carrier 4, the projections 10f of the opposite base half engaging the recesses 12a of the insulating spacer and the respective projections 10d being received within the respective recesses 10e along the upper edge of the two base halves. The spring 26 is inserted within the recess 4a open to the right-hand end of the contactor 4. This assembly is then inserted upward through an open bottom of housing 8 to be held together by the housing. Each base half is provided with a projection 10h centrally located along an outer surface near the bottom edge thereof for snap fit engagement with corresponding recesses 8a in the housing frame 8 to securely lock the assembly together. The frame 8 is also provided with a slot 8b along one end thereof open to the bottom edge, the slot receiving the rectangular flange 12c of insulating spacer 12. The projection 12d of insulating spacer 12 extends partly into the recess 2b of trigger 2 to serve as a guide for the trigger to prevent the latter from rotating. 
     In operation, linear depression of the trigger 2 into the housing 6 effects linear translation of the contact carrier 4. Such movement of the carrier 4 causes respective movement between the spiral grooves 4d and the projections 10g formed on the base halves 10, this relative movement causing the projections 10g to rotate the contact carrier 4 about the axis of shaft 2a as the trigger 2 and contact carrier 4 are depressed against the bias of spring 26. The rotational movement of contact carrier 4 carries the movable contact members 18 into engagement with the stationary contact members 22. The operation of trigger 2 and contact carrier 4 cause the movable contacts 18 to engage the stationary contacts 2 with a combined linear and rotary translational wiping action which provides enhanced switching characteristics. 
     While the switch of this invention has been disclosed in a preferred embodiment, it is to be understood that it is susceptible of various modifications without departing from the scope of the appended claims. For example, base halves 10 and insulating spacer assembly 12 may be secured together by other clamping means or by an adhesive or by sonic welding if desired to thereby eliminate the insulating frame member 8. Moreover, the spiral grooves 4d may be formed on an internal surface of the cylindrical contact carrier 4, and the cylindrical contact carrier 4 may be journaled for rotation within the housing 10 without linear translation. In such case, the shaft 2a of trigger 2 could be formed with cooperating cam projections whereby depression of the trigger within the contact carrier would effect rotation of the contact carrier without the aforedescribed linear translation thereof.