US2231541A

US2231541A - Electric switch

Info

Publication number: US2231541A
Application number: US313735A
Authority: US
Inventors: Edmund G Lodge
Original assignee: Stackpole Carbon Co
Current assignee: Stackpole Carbon Co
Priority date: 1940-01-13
Filing date: 1940-01-13
Publication date: 1941-02-11
Anticipated expiration: 1958-02-11

Description

Feb. 11, 1941. E. e. LODGE ELECTRIC SWITCH Filed Jan. 13, 1940 Insular/'0 [W4 g. mw J G m8 a 525: m. U x

Patented Feb. 11, 1941 UNlTED" STATES PATENT OFFICE ELECTRIC swrron Edmund G. Lodge, St. Marys, Pa., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Application January 13, 1940, Serial No. 313,735

6 Claims.

contact resistance, and in which the arcing between the current-carrying members that occurs when the switch is opened takes place at a point diiferent from the point of engagement of those members when the switch is closed.

In accordance with this invention a terminal member and .a contact member connected to another terminal are mounted on a supporting base in laterally spaced relation. A resilient conductor that is connected with the first terminal member normally engages the contact member and thereby completes the circuit through the switch. The base is also provided with an opening through which an actuating member loosely extends. This actuating memher is adapted when raised to spring the conductor away from the contact to thereby open the circuit. Means, such as a rotatable cam, is provided on the opposite side of the base for raising the actuating member for this purpose.

The conductor is preferably a metal strip integral with the terminal member and having the opposite side edges of its free end overlying the conductor and actuating member. The conduc tor is so formed that when the actuating member is raised it first lifts the side of the conductor overlying it, whereby the opposite edge of the conductor is the last to leave the contact. This causes the electric arc to be drawn between that edge of the conductor and the contact instead of between the normally engaging surfaces of those members. Consequently, those surfaces are not burned and their contact resistance is not increased. By providing the actuating cam with a sharp rise, additional torque must be built up after the cam strikes the actuating member in order to force that member up on the cam. When this additional torque takes effect it practically snaps the switch open.

The invention is illustrated in the accompanying drawing in which Fig. 1 is a plan view of my switch; Fig. 2 is a side view of the switch shown open and with its. supporting structure partly broken away; Fig. 3 is a vertical section taken on the line III,-III of Fig. 2; Fig. iris a horizontal section taken on the line IVIV of Fig. 2; Fig.

5 is a vertical section of the closed switch taken on the line VV of Fig. 1; and Fig. 6 is a. side view, similar to Fig. 2, of a modified embodiment.

Referring to Figs. 1 to 3 of the drawing, a circular insulating member I forms the supporting base of the switch and is provided near its edge with a pair of laterally spaced fixed contacts 2. Each contact has an upwardly projecting integral extension 3 that serves as a terminal to which a wire can be connected. Across the base another pair of terminal members 4 is rigidly mounted. The lower end of each of these terminal members is provided with an integral striplike extension 5 that extends across the base and partly overlies the adjacent contact member 2. These strips normally engage the underlying contacts because the strips are resilient and are therefore pressed against the contacts, whereby they serve as conductors between the

switch terminals

3 and 4.

To permitthe switch to be opened, base iis provided between the two contacts with an opening 5 (Fig. 3) in which an actuating member 1 is loosely mounted. This member is made of in sulating material and its upper end has a flange 8 that prevents it from dropping through the opening. The free end of each conductor 5 only partially overlies the adjacent contact 2, the remaining portion of the free end extending laterally over the actuating member. Consequently, when the actuating member is raised by means to be described presently, it lifts the conductors oil the contacts and thereby opens the switch.

Another feature of this invention is that conductors 5 are so formed that whenthe actuating member lifts their inner edges the conductors twist slightly and those edges rise ahead of their outer edges which are therefore the last to leave the contacts, as shown in an exaggerated'manner in Figs. 2' and 3. As a. result, the electric arc that is formed momentarily as a conductor sep- .arates from its contact member, occurs only at the outer edge of the conductor, and its destructive influence is confined to that point which is only a small part of the surfaces that are in engagement when the switch is closed (Fig. 5) This twisting of the conductors is promoted by providing the free end of each narrow conductor with lateral projections 9' (Fig. 1) to increase its width at that point. By confining the arcin to the outer edges of the conductor strips in this manner, only those points can be burned, whereby the normal contact between the lower surfaces of the conductors and the contact members remains unimpaired and the contact resistance remains low. To insur that the conductors will lie fiaton contacts 2 when the switch is closed, flange 33 of the actuating member is thinner than the contacts, as shown in Fig. 5.

To open the switch the actuating member 1' is raised by a cam (Figs 2, 3 and 4) that engages its convex lower end below base I. According to this invention the cam has a sharply inclined front face i2 (Fig. 2) that tends to stop the cam when it first strikes the actuating memher. The additional torque required to overcome this resistance in order to cause the actuating member to ride up the front face of the cam takes effect suddenly and tends to open the switch much more rapidly than slow break switches usually open.

The cam preferably is moved in a circular path by means of a rotatable shaft H which may be the control shaft of a radio rheostat or volume control, as shown in the drawing. In such a case the switch base I is mounted on one end of the volume control housing I! in the opposite end of which there is a threaded bushing [8 through which the control shaft extends. As'

shown in Fig. 4, the inner end of the shaft inside the housing carries a rectangular insulating member it and a movable contact element [8 that slidably engages a resistance element 19 mounted on the housing base. This contact element is electrically connected by a spiral lead 20 (Fig. 3) to a terminal 21 located between a pair of similar terminals 22 (Fig. 4) connected to the ends of the resistance element. These three terminals are supported by a radial extension 23 of the housing base. The retaining member 24 that holds movable contact element 18 on the control shaft is provided with a lateral projection 28 that limits turning of the shaft by striking against a detent ill on the wall of the housing, as shown in Fig. The opposite side of this retaining member carries cam ii that opens the switch. With this construction the switch is closed as soon as volume control shai't i3 is turned to start the movable contact element moving from the high toward the low resistance end of the resistance element, which would be in a counter-clockwise direction as viewed in Fig. 4, whereby the switch and volume control are actuated by a single shaft.

in the embodiment of the invention shown in Fig. 6 the top of the actuating member 353 that raises the conductor strips is conical. With this form the actuating member engages only the inner edges of the conductor strips when is elevated by the cam. Due to the increased leverage thus obtained on the strips, their twisting "acilitated. Tins embodiment also illus- "es bre dust cap that may likewise be used with the first embodiment. This is pro vided with slots through which terminals on top of base 5 project, and a side wall or flange that spaces the of the cap from base i.

According to the proyi ons of the patent statutes, 2 have explained principle and mode aeration of my invention, and have illustrated and described what It now consider to represent its best embodiment. However, desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An electric switch comprising a base provided with an opening, an electric contact mounted on said base and spaced laterally from said opening, an actuating member extending loosely through said opening, an elongate resilient conductor strip attached at one end to the base at a point removed from said contact and opening, the side edges of the opposite end of the strip overlying the contact and actuating member, and means for raising said member to cause it to lift the strip off said contact, the memberengaging edge of said strip rising first and thereby twisting the strip to confine arcing to its opposite edge.

2. An electric switch comprising a base provided with an opening, an electric contact mounted on said base and spaced laterally from said opening, an actuating member extendin loosely through said opening, an elongate resilient conductor strip attached at one end to the base at a point removed from said contact and opening, the sides of the opposite end of the strip being provided with lateral projections overlying the contact and actuating member, and means for raising said member to cause it to lift the strip off said contact, the member-engaging projection of said strip rising first and thereby twisting the strip to confine arcing to its opposite edge.

3. An electric switch comprising a base provided with an opening, a pair of laterally spaced electric contacts mounted on said base with said opening between them, an actuating member extending loosely through said opening, a pair of elongate resilient conductor strips attached at one end to the base at points removed from said contacts, the side edges of the opposite end of each strip overlying the adjacent contact and actuating member, and means for raising the actuating member to cause it to lift the strips oil the contacts, the inner edges of the strips rising first and thereby twisting the strips to confine arcing to their outer edges.

L. An electric switch comprising a base provided with an opening, a pair of laterally spaced electric contacts mounted on said base with said opening between them, an actuating member extending loosely through said opening, a pair of elongate resilient conductor strips attached at one end to the base at points removed from said contacts, the sides of the opposite end of each strip being provided with lateral projections overlying the adjacent contact and actuating member, and means for raising the actuating member to cause it to lift the strips off the contacts, the inner projections of the strips rising first and thereby twisting the strips to confine arcing to their .outer edges.

5. An electric switch comprising a base provided with an opening, a pair of laterally spaced electric contacts mounted on said base with said opening between them, an actuating member extending loosely through said opening, a pair of elongate resilient conductor strips attached at one end to the base at points removed from said contacts, the side edges of the opposite end of each strip overlying the adjacent contact and actuating member, the upper end of the actuating member being provided with a flange to prevent the member from dropping through said opening, said flange being at least as thin as u said contacts, and means for raising the actuating member to cause it to lift the strips off the contacts, the inner edges of the strips rising first and thereby twisting the strips to confine arcing to their outer edges.

6. An electric switch comprising a base provided with an opening, a pair of laterally spaced electric contacts mounted on said base with said opening between them, an actuating member extending loosely through said opening. a pair of elongate resilient conductor strips attached at one end to the base at points removed from said contacts, the side edges of the opposite end of each strip overlying the adjacent contact and actuating member, the upper end of the actuating member being conical, and means for raisin! the actuating member to cause it to lift the strips off the contacts, the inner edges of the strips rising first and thereby twisting the strips to conflne arcing to their outer edges.

EDMUND G. LODGE.