US3330924A - Contact mounting structure for electric switches - Google Patents

Description

July 11, 1967 R E. LARKIN CONTACT MOUNTING STRUCTURE FOR ELECTRIC SWITCHES Filed Nov. 24, 1965 4a 24 4 24a 24d b 4c 24 HiZdelH 2 Sheets-Sheet l R. E. LARKIN July 11,1967

CONTACT MOUNTING STRUCTURE FOR ELECTRIC SWITCHES Filed Nov. 24, 1965 2 Sheets-Sheet 2 United States Patent 3,339,924 CONTACT MOUNTING STRUCTURE FOR ELECTRIC SWITCHES Robert E. Larltin, Waukesha, Wis, assignor to Cutler- Harnmer, Inc., Milwaukee, Win, a corporation of Delaware Filed Nov. 24, 1%5, Ser. No. 509,548 1 Claim. (Cl. 200-67) This invention relates to electric snap switches particularly those known as utility switches. Specifically, the invention relates to those switches used in the control of portable electric tools.

Portable electric tool manufacturers have long desired a double pole switch for controlling their products, but previous designs have been rather elaborate and costly. Increased foreign use, the desire to eliminate a possible polarity problem of the single pole switch at the wall plug, and the safety factor of allowing both main lines to be broken has created a demanding need for the double pole switch in portable electric tools.

It is therefore an object of this invention to provide an electrical switch which is readily and easily assembled.

It is a further object of this invention to provide a double pole single throw switch which is inexpensive to manufacture.

It is a further object of this invention to provide a double pole single throw switch of a knife blade construction to afford greater electrical life and hence, improved switch performance.

It is a still further object of this invention to provide a double pole single throw switch, by its design, has enhanced dielectric and insulating qualities.

These and other objects'will become more apparent in the following specification and claim when read in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevational view of a switch structure embodying the design;

FIG. 2 is a longitudinal sectional view of the switch of FIG. 1 taken along a line indicated generally by line 22 of FIG. 7;

FIG. 3 is a top plan view of the switch base with certain of the contacting elements in place;

FIG. 4 is an exploded isometric view of certain of the contacting elements;

FIG. 5 is a sectional View taken along the line 55 of FIG. 7;

FIG. 6 is a sectional view similar to FIG. 5 showing the switch in an operated condition; and

FIG. 7 is a cross sectional view of the switch taken along line 77 of FIG. 6.

The particular embodiment disclosed in the drawings is a linearly operable trigger tool handle switch having a molded trigger member 2 and a molded switch base 4 which are retained in their assembled position by a snap-on metal frame 6. The molded parts of the switch are of a suitable molded insulating material of the thermosetting plastic class such as phenolic resin.

The switch frame 6 is of well known construction wherein an upper portion straddles the trigger and a somewhat enlarged lower portion connects to the switch base. Windows 6a are provided in the lower portion of frame 6 which snap over a pair of tapered ears 4a on base 4 to lock the frame to the base.

This type of frame-to-switch base construction usually is further locked together by clinching tabs formed on the lower four corners of the switch frame over mating depressions formed in the base. In this particular embodiment, however, the tabs have been omitted and the lower edge of the windows 6a are offset into centrally located vertical grooves 4b in the switch base which extend from below the ears 4a to the bottom of the base.

The trigger 2 is biased to its extended position by a spring 8 which seats in a recess formed in the trigger and bears against a rear wall of the frame 6. The frame is also provided with a lock-on mechanism 10 of well known construction wherein a side mounted sleeve houses an outwardly biased button which may be depressed to interfere with the trigger when the latter is in its depressed position to maintain the switch in the on positron.

A phenolic insulator sheet 12 is placed in a recessed portion of the switch base 4 to form a cover for various cavities and pockets in the base which house the switch mechanism. Insulator 12 has an elongated, centrally lo cated slot through which a depending boss 2a of the trigger extends to connect to the switch mechanism. The limits of the trigger travel are dictated by the length of the slot in insulator 12. A pair of openings 6b are also provided in the upper portion of frame 6 through which project a pair of ears 2b of trigger 2. The travel of ears 2b in openings 6b is equal to that of depending boss 2a in the slot of insulator 12 to provide top and bottom stops for the trigger, and thus reduce a tendency of the trigger to cant, or tilt, within the frame.

The switch mechanism is of the overcenter toggle type. A molded U-shaped movable contact carrier 14, which has outwardly extending bearing portions 14a at the end of each leg, is pivotally mounted within the base in journals 40 which are centrally located on the upper portion of the sidewalls of base 4. The bight portion of carrier 1 has a recessed spring seat 14b with a central semi-spherical boss to further position the lower end of a helical drive spring 16. At its upper end spring 16 is provided with a cap 18 having a semi-spherical recess therein to be received by the semi-spherical end of boss 2a of trigger 2. The drive spring 16 is thus held in a compressed state between the two bosses 2a and 140 to provide an effective snap-action to carrier 14 when the boss 2a of trigger 2 is moved past the center of boss 14c of carrier 14.

The bottom surface of contact carrier 14 has an arcuate shape which follows the path of travel of the carrier as it pivots, or swings, from one position to the other. Likewise, a central dividing wall, which divides the main cavity of base 4 into two individual contact chambers, has a corresponding arcuate shape. Only a small clearance is provided between the central wall of base 4 and the arcuate bottom of carrier 14 to effectively insulate one contact chamber from the other.

At its ends the arcuate dividing wall of base 4 terminates in vertical walls 4d. Contact carrier 14 is provided with bumpers 14d which extend from the bight portion to strike against the vertical walls 4d and thus limit the arcuate travel of carrier 14.

Contact carrier 14, in addition to having the aforementioned characteristics, is also provided with contactor receiving faces on the outer sides of its legs. Each face has a rectangular boss portion Me which extends downward from the bearing portion 14a, a vertically reclining grove 14 and a pair of support bosses 14g located one on either side of groove 14] and in horizontal alinement with each other.

A blade contactor 20 is provided for each face of the carrier 14 and is formed complementally to the bosses and groove which comprise each face. The shape of contactor 20 bears resemblance to an open-end wrench, there being provided an enlarged head portion which has an open, rectangular recess, or jaw 20a and a reduced shank portion which has at its end a double-bitted contact blade 211-17. An angularly oifset tongue 200 is formed in the shank.

The contactor 20 is placed loosely upon the face of carrier 14 so that the jaw 20a engages the boss 14a. The

a shank portion of the contactor lies between the bosses 14g of the carrier and the lower edges of the head portion of contactor 20 rest upon the shelf-like upper surfaces of bosses 14g. The tongue 200 of contactor 20 fits into the groove 14 the clearances between these two mating portions being held to close tolerances to insure good vertical alinement between the two contactors 20 on the carrier 14. The contact blade 2312 extends below the arcuately formed bottom surface of the carrier 14.

It may be readily seen that there is thus provided a contact carrier and contactor assembly which allows the contactors to be assembled loosely to the carrier and yet be so designed as to be interlocked to the carrier to function as a rigid unit. The boss 14:: of the carrier holds against movement of contactor 20 in an upward direction as well as preventing the upper end of the contactor from moving to either side. The bosses 14g hold against downward movement of the contactor and the tongue 20c and groove 14 arrangement prevent the bottom end of the contactor from moving sideways. A means to hold the contactor 20 to the face of the carrier 14 must be provided to complete the interlocked arrangement.

A pair of brush contacts 22 have been incorporated into the design which provide both the needed means to hold contactors 20 to the faces of carrier 14 and afford good electrical connection to the contactors. The brush contacts 22 are mirror images of each other to provide right and left-hand contacts.

The brush contacts 22 are stamped metal parts which have a U-shaped channel body with tabs 22a cut from the legs thereof to extend outwardly from the bight portion. The bight portion also has a depending fiat member 22b extending downwardly therefrom and which has tabs 22c extending outwardly thereof and in vertical alinement with tabs 22a. One leg of the U-shaped body has an extension, or arm 22d which terminates in a domed contact surface 22e formed on the inner surface.

Referring specifically to the top plan view of the switch base 4 (FIG. 3) it may be seen that the base is provided with terminal pockets 4e adjacent the ends of each contact chamber but divided from the latter by vertical walls. Vertical grooves are formed in the side walls of each pocket adjacent the dividing wall as is best seen in the lower chamber from which the contact elements have been removed.

The brush contact 22 shown in the isometric view (FIG. 4) is shown in place in the base 4 in FIG. 3. The brush is inserted from the top with the tabs 22a and 22c being inserted in the grooves of the pocket 42 so that the bight portion and extension 22b lie to the pocket side of the dividing wall, while the legs of the U-shaped body lie within an opening in that wall to extend into the contact chamber. The arm 22d extends into the central area of the chamber and it can be seen that this arm is formed with a slight bend toward the center of the base. The other brush would have its arm 22d on the opposite leg of the U-shaped body and it likewise would have a bend toward the center of the base. The contact surfaces 222 of these brushes bear against the contactors 20 throughout the travel of the carrier to hold the contactors against the faces of carrier 14 and thereby also provide a rubbing, or brush electrical contact with the contactors.

The stationary contacts 24 are of spring clip contact design. The body structure is quite similar to brushes 22, there being a U-shaped body portion having tabs 24a and a depending member 24b with tabs 24c. The legs of the U-shaped body have downwardly extending portions 24d which terminate in enlarged contact clips 24:2. The portions 24d are bent toward each other and reversely bent parallel to each other to reduce the gap between the contact clips to provide an effective spring clip contact for the knife blade of contactor 25 The outer ends of the clips 24c are flared outwardly to guide the blade 20b of contactor 20 to move therebetween.

The stationary contacts 24 are inserted into the terminal pockets 42 in the same manner as were brush contacts 22. The extensions 24:! extend downward along the dividing wall to locate the contact clips 24e in the lower corner of the contact chamber.

C-shaped wire clips 26 are also inserted into the pockets 4e with their open side toward the contacts 22 and 24. Wire leads are pressed into the pockets through openings in the bottom of the latter so that they displace the lower legs of the clips 26. That leg thereby holds the wire lead against the members 22b and 24b to electrically connect the switch to an external source and to the device to be controlled. The shape of the clips 26 is such as to also grip the wire leads and prevent them from being pulled out.

The switch is shown in its assembled form in FIG. 5 which is a sectional view taken along one of the contact chambers. The switch is shown in its off position with the brush contact 22 bearing upon the contactor 20 to hold the latter to the carrier 14. By depressing the trigger 2 so that the toggle linkage moves the carrier to the other position, the contactor 20 wipes along the brush 22 and engages the contact clips Me. This position (FIG. 6) is the on position with the circuit completed through the brush 22, the contactor 20 and the contact clip 24 in each pole.

Thus, a switch is provided which is of the double pole design and has all of the desirable features accorded thereto, and through its design, is far less costly to manufacture than previous designs. The wedged contactors and stamped contacts and brushes require no complex production procedures, and modern molding processes allow the contact carrier and its faces to be easily made. Assembly time is reduced because all parts are merely inserted and no securing is necessary. The wiping brush connection and knife blade connection aflt'ord excellent electrical life and contacting qualities.

While the above described switch is disclosed as a trigger tool handle switch, it is to be noted that the advantages of such switch construction could well have equal applicability to other types of switches and that the switch structure is subject to various modifications without departing from the scope of the appended claim.

I claim:

In an electric snap switch of the type wherein an external operator has connection through an overcenter toggle linkage to a movable contact carrier within a switch base, the combination comprising: a switch base; a U-shaped insulating contact carrier pivotally mounted in said switch base for oscillatory movement therein, a face portion formed on the outer surface of each leg of said carrier, each face portion comprising a plurality of outwardiy extending boss portions and a vertically reclining groove portion; a pair of non-flexible contactor members removably placed against said face portions, said contactor members each being shaped complementally to said face portions and having portions thereof mutually engaging said outwardly extending boss portions and said vertically reclining groove portion to interlock said contactor members to said carrier face portions for oscillatory movement with said contact carrier, said contactor members further having contact blade portions depending vertically beyond the legs of said U-shaped carrier; and first and second pairs of stationary contact members sceurely held within said base, said first pair of stationary contact members each having a resilient arm portion extending therefrom and engaging a surface of a respective one of said contactor members to bias said contactor member against said face portion and provide electrical connection therebetween throughout the entire oscillatory movement of said contactor member and carrier, and said second pair of stationary contact members each comprising a pair of resilient spring cli 5 contacts for receiving said blade portion of a respective one of said contactor members therebetween in circuit making engagement upon movement of said carrier in one direction.

References Cited UNITED STATES PATENTS 2,156,989 5/1939 Johnson. 2,632,960 12/1952 Haydon.

Sanda 200-154 Reich et a1. Benander et a1. Woodrufi.

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