US3138689A - Manually operated trigger switch for rotatable electric tools - Google Patents

Description

June 23, 1964 MANUALLY OPERATED TR R. E. LARKIN 3,138,689

IGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed NOV. 2, 1959 3 Sheets-Sheet l J n 23, 9 4 R. E. LARKlN 3,138,689

MANUALLY OPERATED TRIGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed Nov. 2, 1959 3 Sheets-Sheet 2 8 24 Ma 39a Zea June 23, 1964 R. E. LARKlN 3,138,689

MANUALLY OPERATED TRIGGER SWITCH FOR ROTATABLE ELECTRIC TOOLS Filed Nov. 2, 1959 3 Sheets-Sheet 3 United States Patent 3,138,639 MANUALLY OPERATED TRIGGER SWITCH FOR RGTATABLE ELECTRIC TOOLS Robert E. Larkin, Milwaukee, Wis, assignor to Cutler,

Hammer, Inc, Milwaukee, Wis., a corporation of Delaware Filed Nov. 2, i959, Ser. No. 850,225 4 Claims. (Cl. 260-168) This invention relates generally to electric switches. More particularly, the invention relates to manually operated trigger type switches which are adapted for use in portable electric tools, but the invention is not limited thereto.

It is an object of the invention to provide improved switches of the aforesaid character which are readily interchangeable with present types of trigger switches.

Another and more specific object is to provide improved manually operated, normally olf-momentary on, slow-make and slow-break, single pole, single throw, in-line motion trigger switches which are especially adapted for use in portable electric tools.

Still another object is to provide improved switches of the aforesaid character which are characterized by improvements in the means of assembly, namely a snap together feature.

A further object is to provide improved switches of the aforesaid character which are compact, employ a minimum number of parts, are relatively simple in structure and mode of operation, lend themselves readily to mass production techniques, and are reliable in operation.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of the invention which will hereinafter be described, it being understood that the embodiments shown are susceptible of modification with respect to certain details thereof without departing from the scope of the appended claims.

In the drawings:

FIGURE 1 is a side elevational view of a trigger switch incorporating the invention shown mounted within the pistol grip handle of a portable electrical tool;

FIG. 2 is an elevational view of the rear end of the handle-mounted switch shown in FIG. 1;

FIG. 3 is a top plan view of the switch showing portions of its locking mechanism in cross-section;

FIG. 4 is a bottom plan view of the switch;

FIG. 5 is a cross-sectional view of the switch showing it in normally olf position; the upper portion of the cross section being taken along line 5a-5a of FIG. 3 and the lower portion of the cross-section being taken along line 5b5b of FIG. 7;

FIG. 6 is a cross-sectional View of the switch taken along line 6-6 of FIG. 5;

FIG. 7 is a top plan view showing the interior of the base of the switch and the stationary contacts and a bussing connector therewithin;

FIG. 8 is a side elevational view of the switch frame;

FIG. 9 is an isometric view of the bussing connector which is shown removed from the switch base;

FIG. 10 is a bottom plan view of the trigger member of the switch;

FIG. 11 is an enlarged isometric view of the base of the switch with portions cut away to expose structural details therewithin;

FIGS. 12, 13 and 14 are enlarged cross-sectional views, similar to the view in FIG. 6 showing various stages of the connection of the switch frame to the switch base during assembly; and

FIG. 15 is a cross-sectional view of a portion of the trigger of the switch, similar to the view in FIG. 5, showing an alternative form of construction.

It will be understood that in the various figures similar elements are designated by the same reference numerals.

Referring FIGS. 1, 2 and 3, the numeral 20 designates a trigger switch incorporating the invention which is shown mounted in the pistol grip handle 21 of a portable electric tool which, for example, may be assumed to be provided with a motor (not shown). Handle 21, which preferably is formed of cast aluminum, is separable into two sections and is provided with integrally formed projections 21a on the opposite inside walls thereof which entrap switch 20 and with an aperture 21b through which the trigger 23 of the switch extends. Handle 21 is also provided with a hole 21c in the side wall thereof through which the lock button 46 of the switch 20 extends and with a hole 21d in the bottom wall thereof through which the insulated power supply leads L1 and L2 extend. Supply lines L1 and L2, which may be assumed to be connected to a suitable source of A.-C. power supply (not shown), extend into switch 20, and two insulated wire leads M1 and M2, which may be assumed to be connected to the tool motor (not shown), also extend into the switch. As will hereinafter appear, leads L2 and M2 are electrically connected to each other through a bussing connector within switch 20 and leads L1 and M1 are connected to individual stationary contacts within the base, which contacts are adapted to be bridged to complete an energizing circuit for the tool motor (not shown) when the trigger 23 of the switch is depressed.

Referring generally to FIGS. 1 through 10, switch 20 comprises a base member 22 and a trigger member 23 which is slidably movable with respect to the base. Preferably, base 22 and trigger 23 are molded from electrical insulating material such as Bakelite or the like. Trigger 23 is associated with base 22 by a rigid frame member 24, preferably formed by stamping from sheet metal, which is rigidly secured to the base, as will hereinafter be explained.

As FIGS. 4 through 7 show, base 22 rigidly supports the two spaced-apart, electrically conductive, stationary contact members 25 and 26 which are adapted to have leads M1 and L1 (shown in FIGS. 1 and 2), respectively, electrically and mechanically connected thereto as by soldering or other suitable means. Base 22 also rigidly supports the electrically conductive, bussing connector 27, best seen in FIG. 9, which is not electrically connected to any portion of switch 20, but which is adapted to have the leads M2 and L2 electrically and mechanically connected thereto as by soldering or other suitable means as a convenient means for electrically connecting those leads together. Stationary contacts 25 and 26 and bussing connector 27 are preferably formed by stamping from sheet bronze or similar material. Since contacts 25 and 26 are substantially identical in configuration and manner of attachment to base 22 of switch 20, although they are reversely disposed therein, only contact 26 will be described in detail hereinafter.

As FIGS. 4 through 7 and 11 show, base 22 is molded so that the flat upper surface 28 thereof is provided with a shallow substantially rectangular recess 29 in the bottom of which is a deeper, substantially U-shaped recess 30, the legs of which recess 30 communicate by means of the slots 31 and 32, respectively, with the cavities 33 and 34, respectively, in the bottom of the base. The right-hand end of rectangular recess 29 communicates by means of a slot 35 with a cavity 36 in the bottom of the base.

As FIGS. 5, 6 and 7 show, stationary contact 26 initially is a substantially flat member bent over and cambered at the top thereof to provide a contact surface 26a. The bent over portion of contact 26 rests on a projection 32a which is integral with the wall and the floor of the leg of the U- shaped recess 30 in base 22 as FIGS. 6, 7 and 11 show. The middle portion of contact 26 fits snugly within slot 32 in base 22 and the tang of the contact which is provided with a wire attachment hole 26b, depends into cavity 34. Contact 26 is secured to base 22 by staking or outwardly shearing the two tabs 26c after the contact is in place in the base.

As FIGS. 4, 5, 6, 7 and 9 show, bussing connector 27 initially is a substantially U-shaped member having a struck out tongue 27a which engages the top wall of cavity 36. After the connector 27 is in place in the base 22 the top projection 27b thereof is bent over, as FIGS. and 7 show, to rigidly secure the connector to the base.

As FIG. 11 shows, base 22 is adapted to have frame 24 rigidly secured thereto and for this purpose is provided with two elongated slots 38 and 39 which extend from the upper surface 28 thereof and communicate with the cavities 33 and 34, respectively, formed in the bottom of the base. The walls of the slots 38 and 39 are substantially perpendicular but the outermost walls therein are provided with integrally formed projections 38a and 39a, respectively.

Each projection 38a and 3911, which extends only part of the length of its slot so that space exists at either end thereof preferably has a triangular cross-sectional configuration. Thus, the surface thereof slopes downwardly and away from the wall of the slot from which it projects. The bottom surface of each projection is substantially fiat and projects at a right angle from the wall of the slot.

As FIGS. 1 through 6 and 8 show, frame 24 is rigidly secured to base 22 and maintains trigger 23 in proper relationship therewith. Frame 24 comprises a top wall 24a having two indexing holes 2411 and 24i, two rectangular cutouts 24g therein, an end wall 241), and tWo side walls from which the ears 24c and 24d, respectively, depend. The ears 24c and 24d are provided with the apertures 24a and 24 respectively, which are adapted to engage the projection 39a and 38a, respectively, in the slots in base 22. As FIGS. 12, 13 and 14 show, frame 24 fits over trigger 23 and is pressed down so that the ears enter the slots and gradually converge as they slide down the surfaces of the projection. Convergence is possible since the ears are resilient and there is clearance within the slots. When the apertures in the ears register with the projections, the resiliency of the sides of the frame cause the ears to spring back to their normal position and the apertures in the ears engage the projections thereby causing the frame to be secured to the base. It is to be understood that trigger 22, which fits snugly within frame 24, prevents inward springing of the sides and ears of the frame to disengage the ear apertures from the projection and the interlocked assembly cannot be disassembled without damaging the device. Another advantage of this means of assembly is that no tools or fastening devices are needed to secure the frame to the base.

As FIGS. 1 through 6 and show, trigger 23 has a portion which is adapted to be gripped by the operators finger and an elongated portion which extends back therefrom which is adapted to be entrapped by frame 24. The fiat bottom surface 23a of trigger 23 is provided with two integrally formed, parallel guide ribs 23b which extend into shallow recess 29 of base 22 and slide along the inside side walls thereof to aline and guide the trigger as it moves. The top surface of trigger 23 is provided with two integrally formed projections 230 which are adapted to extend through the cutouts 24g in the top wall 24a of frame 24 and cooperate therewith to limit forward and rearward travel of the trigger with respect to the frame and base. Trigger 23 is further provided with a horizontally disposed groove 23d, open at one end, which accommodates a helically shaped compression spring or return spring 40 which bears against the end of the groove and end wall 24b of frame 24 and tends to bias the trigger outwardly of the frame to off position.

As FIGS. 5 and 10 show, the bottom of trigger 23 is provided with a contact cavity 23c which is adapted to accommodate a bridging contact member 41, best seen in FIGS. 5 and 6, which is a substantially U-shaped strip of electrically conductive material such as bronze. An aperture 23 extends from contact cavity 23a through the upper portion of trigger 23 and accommodates a ball detent 42, formed of relatively hard, electrically nonconductive material such as glass, and a helically shaped compression spring or contact loading spring 43 which bears upwardly against ball detent 42 and downwardly against bridging contact 41. It will be understood that ball-detent 42 cooperates with the index holes 2411 and 24i to indicate to the operator by feel the proper location of the trigger 23 and bridging contact 41 with respect to the base 22 and the stationary contacts and 26. The fact that the ball detent 42 is fabricated of insulating material prevents an electrical circuit from existing between bridging contact 41, spring 43, the ball detent, and metal frame 24 which might endanger the operator.

Normally, upon release of finger pressure, trigger 23 is biased to off position by return spring and the various members of the switch assume the position hereinbefore described.

Normally, as FIGS. 1, 2, 3, 4, 5 and 6 show, trigger switch 20 is in off condition. That is to say, return spring 40 biases trigger 23 outwardly of frame 24 and ball detent 42 is biased into forward indexing hole 2411 by contact loading spring 43. Spring 43 also biases bridging contact 41 against the floor of shallow recess 29 in base 22.

FIG. 15 shows an alternative form of switch construction wherein the ball detent is omitted. In the alternative form of construction the top wall 24a of the frame need not be provided with indexing holes and trigger 23 is .not provided with a hole, comparable to hole 23 in the first embodiment of the switch, which extends completely through the trigger. In all other respects, however, the embodiment shown in FIG. 15 operates in the same manner as the first embodiment, except that the feel indication is absent.

FIGS. 1, 2, 3, 4 and 6 show that switch 20 is provided with means for locking the switch in on or closed condition. As FIGS. 3 and 8 show, the side wall of frame 24 is provided with a circular hole 24j whose edge flares outwardly. A substantially cylindrical pin 34, which has a mushroom-like head which is of greater diameter than circular hole 24 extends through hole 24 and the serrated end of the pin is force-fitted in a hole provided in a pushbutton 46 which is preferably formed of electrical insulating material. A compression spring 47, which surrounds pin 45 and is disposed between the side wall of frame 24 and pushbutton 46, normally biases the pushbutton and the pin outwardly of the frame so that the head of the pin fits snugly within the depression formed by the flared edge of circular hole 24j. When the trigger switch 20 is disposed within tool handle 21, pushbutton 46 extends through the hole 21c in the handle and is afforded support by the handle. The side of trigger 23 of the switch 20 is provided with a depression 23h, best seen in FIG. 3, which atfords clearance for the head of pin 45. When the trigger 23 is depressed, pushbutton 46 may be depressed and the pin 45 will extend through a cut-away portion 23i in the wall of the trigger and the head of the pin will interfere with the edge of the wall to prevent outward movement of the trigger even after finger pressure on the trigger is released. To release the lock, trigger 23 is depressed slightly to take the strain off pin 45 and spring 47 causes the pin to bias outwardly to its normal position clear of the trigger. Then, upon release of finger pressure, trigger 23 is free to return to its normal off position. It is to be noted that a rigid sleeve which ordinarily would be attached to frame 24 to afford support for the pushbutton 45, pin and spring is not needed in the type of device described herein since the pushbutton is supported directly by the tool handle.

The switch 20 operates as follows: Assume that the switch is mounted within tool handle 21, is shown in FIGS. 1, 2 and 3, and that the energized supply conductors L1 and L2 are connected to stationary contact 26 and to buss 27, respectively and that the motor leads M1 and M2 are connected to stationary contact 25 and to buss 27 respectively.

Normally, the return spring 40 biases trigger 23 to the off position, as shown in FIGS. 1, 2, 3, 4, 5 and 6, i.e., so that trigger is moved outwardly of frame 24 as far as is permitted by the cooperation of projection 23c of the trigger with the slots 24g of frame 24. In this extreme position the spring 43, which is under compression, acts upon bridging contact 41 to bias it against the floor of shallow recess 29 in base 22 and acts upon ball detent 42 to bias it into forward indexing hole 24h in the top wall 24a of frame 24. In this condition, of course, no electrical contact is established between the stationary contacts.

To effect closure of switch 20, the trigger 23 is pushed inwardly of frame 24 against the bias of return spring 40. Initially, as pressure is applied to trigger 23, ball detent 42 is forced to disengage forward index hole 24h of frame 24 and rides against the under surface of the top wall 24a of the frame. Simultaneously, trigger 23 slides bridging contact 41 across the floor of shallow recess 29 in base 22 and over onto the cambered surfaces of stationary contacts 25 and 26 in base 20 where it is held in good contact by the pressure of spring 43. Rearward travel of trigger 23 is limited by the projection 23c thereof which cooperates with the slots 24;; of frame 24. In rearward position, when bridging contact 41 is in proper position with respect to the stationary contact, the ball detent 42 registers with rear indexing hole 24i in top wall 24a of frame 24. As trigger 23 is moved rearwardly return spring 40 is compressed, thereby loading it to effect return of the trigger when finger pressure on the trigger is released.

Upon release of pressure, return spring 40 effects return of trigger 23 to the normal or off position hereinbefore described.

It is apparent that in the embodiments of the invention disclosed herein the frame 24 attaches movable trigger 23 to base 22 by means of a pair of depending legs which are inserted into separate slots in the base. It is to be understood that a single cavity in a base member having oppositely disposed projections on opposite walls could be employed. Furthermore, the member or element which is attached to a base by a frame need not necessarily be movable as is the trigger 23. It should also be noted that a frame member having only a single depending portion adapted to engage a projection in a slot would serve to attach the frame to a base provided, of course, that some other portion of the frame such as the other side thereof, was rigidly anchored to the base in a suitable manner.

I claim:

1. In an electric switch, in combination, a base, at least one stationary contact supported by said base, spacedapart slots extending into said base from a surface thereof, a projection extending from the outermost Wall of each slot, a movable member slidably positioned on said surface of said base, said movable member having a movable contact cooperating with said stationary contact, and a frame entrapping said movable member to maintam said member slidably positioned with respect to said surface of said base, said frame having resilient portions which extend beyond the surface of said member which is in association with the said surface of said base, each resilient portion being provided with an aperture which is adapted to engage the projection in the cavity into which said resilient portion is inserted to attach said frame to said base.

2. In an electric switch, in combination, a molded insulating base, a pair of spaced-apart contacts supported by said base, slots within said base, a member slidable on said base and having a contact which is moved thereby into and out of bridging engagement with said spacedapart contacts, and a frame having a portion holding said member on said base, said frame also having apertured portions which when inserted into said slots within said molded insulating base spring into self-locking engagement about projections formed on said base within said slots to hold said member in confined slidable operating relation on said base.

3. In an electric switch, in combination, an insulating base, a pair of stationary contacts supported by said base, slots within said base, a trigger member slidable on said base, a bridging contact slidably movable with said trigger member, a frame having a portion straddling said trigger member, said frame also being provided with resilient depending portions which are adapted to extend into said slots within said base to lockingly engage said frame and said base, a spring disposed at one end against said frame and at its other end against said trigger to bias said trigger into given position, a loading spring disposed between said bridging contact, and an insulated indexing member movable with said trigger member and adapted to cooperate with indexing holes in said frame, said loading spring adapted to bias said bridging contact into engagement with said stationary contacts and to bias said indexing member into respective indexing holes in said frame.

4. The combination according to claim 3 including a spring disposed directly between said bridging contact and said trigger member to bias said bridging contact into engagement with said stationary contacts when said trigger member is moved from said given position.

References Cited in the file of this patent UNITED STATES PATENTS 2,502,600 Spender Apr. 4, 1950 2,618,723 Mahaffay Nov. 18, 1952 2,665,353 Popp Jan. 5, 1954 2,744,176 Kaman May 1, 1956 2,789,170 Johnson Apr. 16, 1957 2,881,292 Winter et a1. Apr. 7, 1959 2,922,012 OMara Jan. 19, 1960 2,928,921 Cranmose Mar. 15, 1960 2,936,349 Johnson May 10, 1960

Claims (1)

1. 2. IN AN ELECTRIC SWITCH, IN COMBINATION, A MOLDED INSULATING BASE, A PAIR OF SPACED-APART CONTACTS SUPPORTED BY SAID BASE, SLOTS WITHIN SAID BASE, A MEMBER SLIDABLE ON SAID BASE AND HAVING A CONTACT WHICH IS MOVED THEREBY INTO AND OUT OF BRIDGING ENGAGEMENT WITH SAID SPACEDAPART CONTACTS, AND A FRAME HAVING A PORTION HOLDING SAID MEMBER ON SAID BASE, SAID FRAME ALSO HAVING APERTURED PORTIONS WHICH WHEN INSERTED INTO SAID SLOTS WITHIN SAID MOLDED INSULATING BASE SPRING INTO SELF-LOCKING ENGAGEMENT ABOUT PROJECTIONS FORMED ON SAID BASE WITHIN SAID SLOTS TO HOLD SAID MEMBER IN CONFINED SLIDABLE OPERATING RELATION ON SAID BASE.

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