Abstract:
A multipurpose electric trigger switch adapted to be mounted in the handle of a portable electric tool for controlling the A. C. power circuit and, to afford a higher rating, the switch is provided with double-pole butt contacts. A movable contactor is pivoted and translated on a resilient terminal into wiping and abutting contact with a stationary terminal in response to linear sliding movement of an operator having a cam which engages inclined camming surfaces on the contactor.

Description:
BACKGROUND OF THE INVENTION 
     Electric switches, including trigger switches for portable electric tools, have been known heretofore. However, these prior switches have been subject to one or more disadvantages that have limited their electrical capabilities, such as sliding contacts subject to excessive wear that limits the life of the switch, contacts that are teasible and contact operating mechanisms that reduce contact pressures prior to opening thereby causing early deterioration, and short trigger movement between contact closed and open positions that causes frequent or false operation and might create dangerous conditions particularly when used in portable electric circular saws and the like. While my prior U.S. Pat. No. 3,869,590, issued Mar. 4, 1975 and my pending application Ser. No. 586,059, filed June 11, 1975, disclose switch structures that overcome these disadvantages, this invention relates to an alternative structure for accomplishing the same. 
     SUMMARY OF THE INVENTION 
     This invention relates to electric switches, including double-pole higher rated tool handle switches of the trigger operated type. 
     An object of the invention is to provide an improved switch. 
     Another object of the invention is to provide an improved higher rated switch. 
     A more specific object of the invention is to provide an improved butt contact switch which will positively shear and break any contact welds. 
     Another specific object of the invention is to provide an improved switch of the aforementioned type having non-teasible contacts. 
     Another specific object of the invention is to provide an improved switch of the aforementioned type having a controllable amount of wipe. 
     Another specific object of the invention is to provide an improved switch of the aforementioned type having low contact bounce. 
     Another specific object of the invention is to provide an improved switch of the aforementioned type having maximum contact pressure at the point of trip open. 
     Another specific object of the invention is to provide an improved switch of the aforementioned type having substantial trigger movement between trip &#34;off&#34; and trip &#34;on&#34; positions to prevent repeated or accidental switch operation. 
     Another specific object of the invention is to provide an economical and reliable higher rating contact mechanism for an electric switch. 
     Other objects and advantages of the invention will hereinafter appear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged partial, vertical cross-sectional view of the switch taken along line 1--1 of FIG. 3 to show one pole of the two pole electric switch. 
     FIG. 2 is a bottom view of the camming insert and the insulating base cover in disassembled condition. 
     FIG. 3 is a horizontal cross-sectional view taken generally along line 3--3 of FIG. 1 to show a top view of the double-pole contacts. 
     FIG. 4 is a vertical cross-sectional view taken along line 4--4 of FIG. 1 to show a rear view of the contactors. 
     FIG. 5 is a partial, horizontal cross-sectional view taken along line 5--5 of FIG. 1 to show the wire retention clips. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, there is shown a double-pole higher rated tool handle switch constructed in accordance with the invention. By higher rated is meant that for an electrical rating of 12 amperes, 125 volts, having an inrush current of 60 amperes on make and current of 12 amperes on break, for example, it will have an operational life rating of 50,000 to 60,000 operations, an increase of 4 to 5 times over prior lower rated switches in the same size of housing. 
     As shown in FIGS. 1 and 3, the switch is provided with an insulating base 2 generally rectangular in shape and open at the top for housing the double-pole switch contacts, the left pole of which is shown in FIG. 1. The top of this base is partly closed by an insulating cover 4, as shown in FIG. 1. As shown in FIG. 2, this cover is provided with a slot 4b rearwardly opening into a wider slot 4a, the purpose of which is described more fully hereinafter. This cover is also provided with elongated narrow locating ears 4c and 4d protruding from the sides thereof to seat the cover in complementally formed notches in the base 2, as shown in FIGS. 2 and 4. The interior of the base is divided into two compartments, left and right, for the respective poles of the double-pole switch, by a longitudinal center dividing wall 2a, FIG. 4, that extends all the way up to cover 4. These left and right compartments are each divided into two subcompartments, front and back, for the movable and stationary contact connector clips, by a lateral wall 2b, FIG. 1, extending across the middle thereof. Each back subcompartment is provided with a stop or boss 5 and 7 extending laterally from center dividing wall 2a of the base to limit the clockwise pivoting of movable contactors 26 and 27, as will be more fully described hereinafter. 
     An insulating trigger 6 has a finger-engaging portion 6a extending forwardly from the base and a slidable portion 6b overlying the base and held thereon by a frame 8 that is secured to the base in a known manner. A trigger return spring provides the switch with momentary action. For this purpose, a helical compression spring 10 is positioned in a groove 6c that extends forwardly partway from the rear end of slidable portion 6b of the trigger. The front end of this spring bears against the vertical wall at the front end of such groove and the rear end of this spring bears against the rear vertical wall of the frame. To limit trigger movement in both directions, the frame is provided with a pair of rectangular apertures 8a and 8b and the top of the slidable portion of the trigger is provided with a pair of projections 6d and 6f extending up through the respective apertures for limited movement therein as shown in FIGS. 1 and 4. 
     Left and right stationary contact terminals 12 and 13 are retained in slots in the rear end of base 2, FIGS. 1 and 3. These rigid terminals extend from their anchored ends up, then down and toward the front, and then down and slightly toward the rear, as shown in FIG. 1. A stationary contact 14 is affixed to terminal 12 and another stationary contact (not shown) is affixed to terminal 13. Left and right flexible cantilever terminals 15 and 16 are retained in slots in the front end of base 2, FIGS. 1 and 3. These flexible terminals extend from their anchored ends up then toward the rear, reduced rear end portions 14a and 16a, FIGS. 1, 3 and 4, passing through rectangular apertures in the shank portions of the respective contactors 26 and 27 to bias the contactors upwardly, as will be more fully described hereinafter. 
     In order to make electrical connections to the two pairs of terminals of the double-pole switch, there are provided a first pair of connector clips 17 and 18 at the rear bottom of the base, and a second pair of connector clips 19 and 20 at the forward bottom of the base, as shown in FIGS. 1 and 5. These clips are formed alike from a ribbon-like metal strip and each is provided with a pair of short wings at the vertical mounted end thereof adjacent lateral wall 2b of the base whereby they are retained in a pair of vertical grooves 2c in the wall as shown in FIG. 5. From the lower end of such vertical retaining portion, each connector clip is bent up about 30° from the horizontal so that the other end thereof rests against the flat inner surface of the retaining portion of the respective terminal. The bottom of the base is provided with two pairs of holes 21, 22 and 23, 24, FIGS. 1 and 3, through which solid or tinned, stranded electric wires may be pushed in between the terminals and the respective connector clips to make connections thereto. 
     Each flexible terminal 15 and 16 carries a movable contactor 26 and 27 respectively. Contactor 26 has: an upper, molded insulating portion 26a having two oppositely inclined camming surfaces meeting at an apex; an enlarged middle, insulating portion 26b having trunnions 26d and 26e formed on the lateral ends thereof; and a depending electrically conductive shank portion 26c having a terminal-receiving rectangular aperture 26f and a contact 28 attached to one surface of its lower end. Contactor 27 is identically formed and has a contact 29 mounted thereon. As aforedescribed, and shown in FIGS. 1, 3 and 4, the reduced end portion 15a of flexible terminal 15 extends through aperture 26f, in electrical connection with shank portion 26c and biases the contactor upwardly. Trunnions 26d and 26e ride up and down in slots 30 and 31, FIGS. 1 and 4, formed in the base side wall and center dividing wall, thereby permitting pivoting of the contactor together with vertical reciprocal motion thereof. Likewise, contactor 27 pivots and reciprocates vertically in the right compartment of the base. 
     As seen in FIG. 1, the trigger is formed with recess 6e for slidably receiving a single cam insert 32. This insert extends across the width of frame 8, as shown in FIG. 4, and has a rear portion 32a extending rearwardly beyond the recess and a lower rear portion 32b extending downwardly therefrom through slot 4a in the cover, FIGS. 1 and 2. Portion 32b is spaced slightly above center dividing wall 2a. A lower front portion 32c, FIGS. 1 and 2, extends downwardly from the center of the insert through slot 4b. The front edge of slot 4b and the rear wall of base 2 act as stops for the forward-rearward sliding of the insert. The insert is further provided with a camming tip 32d formed on its bottom surface by a pair of spaced lateral grooves for engaging the inclined camming surfaces of both contactors 26 and 27. 
     Operation of the switch will now be described. FIG. 1 depicts full trigger release with projections 6d, 6f stopped against the front edge of apertures 8a, 8b and with lower portion 32c stopped against the front edge of slot 4b. Upon depression of the trigger, against the bias of spring 10, the insert will remain stationary until the front vertical wall of recess 6e strikes the front of insert 32, thus resulting in lost motion of the trigger to thereby increase trigger movement between trip &#34;off&#34; and trip &#34;on&#34; positions. Further depression of the trigger will carry the insert with it to cause downward camming of the contactors. When camming tip 32d crosses the apex formed by the two inclined camming surfaces of contactor 26, the contactor will suddenly pivot counterclockwise about trunnions 26d and 26e to close contacts 28 and 14. Contactor 27 likewise pivots to close the contacts in the right compartment. The insert snaps rearwardly, allowing upward movement of the contactor which causes wiping action of the contacts as they engage. Upon trigger release, the insert remains stationary and stopped against the rear wall of base 2 until the rear wall of recess 6e strikes the upper rear part of the insert. Further release of the trigger carries the insert forwardly with it to cause downward movement of the contactor which shears and breaks any welds between the contacts as they disengage when the tip 32d passes over the apex. 
     It is important to provide a forward stop for insert 32 so that camming tip 32d can provide an upward stop for the contactors under the bias of the flexible terminals, thus effecting a clockwise torque on the contactors against stops 5 and 7 respectively. After the camming tip passes the apex, the upward bias of the flexible terminal produces a counterclockwise torque on the contactor because the upward stop (camming tip 32d) is now on the negatively sloped rear camming surface and because the contactor cannot move horizontally. 
     It is also important to provide a rearward stop for insert 32 so that camming tip 32d can remain an upward stop for the contactor when the trigger is fully depressed and the contacts are closed. These stops and the horizontal constrainment provided by slots 30 and 31 in the walls of the base enable the upward bias of the flexible terminal to produce the requisitely directed torque to pivot the contactor. 
     While a trigger switch has been shown, it can easily be appreciated the mechanism disclosed hereby is adaptable for use in other types of switches. For example, sliding portion 6b may be horizontally reciprocated by a toggle lever cooperating therewith from above. 
     The objects of the invention are achieved in the following respects: 
     there is positive shearing and breaking of any welds because of the pivoting and vertically downward motion of the contactor during trigger release; 
     the contacts are non-teasible because the camming tip cannot be held on the apex of the contactor; 
     the amount of wipe is controlled by the flexure of the flexible terminal, the slope of the inclined camming surfaces of the contactor, and the vertical depth of the camming tip; 
     there is low contact bounce because of the continuous counterclockwise torque applied to the contactor by the upward bias of the flexible terminal after the camming tip crosses the apex; 
     there is maximum contact pressure at the point of trip open because the contactor is cammed to its extreme downward position against the bias of the flexible terminal at such point; 
     there is substantial trigger movement between trip &#34;on&#34; and trip &#34;off&#34; positions due to the lost motion of the camming insert within recess 6e and the distance across an inclined surface which the camming tip must traverse before reaching the apex.