US3350522A

US3350522A - Push-pull electric switch

Info

Publication number: US3350522A
Application number: US577028A
Authority: US
Inventors: David A Olson
Original assignee: Stackpole Carbon Co
Current assignee: Stackpole Carbon Co
Priority date: 1966-09-02
Filing date: 1966-09-02
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31

Description

Oct. 31, 1967 D. A. OLSON 3,350,522

PUSH-PULL ELECTRIC SWITCH Filed Sept. 2, 1966 2 Sheets-Sheet 2 /0 3g "2 /6 III I I A 5! {IL J' l I'IIIIIHIB 4 l9 l-l# lag i R P1 .6

2 W l I I [1'3 INVENTOR. DAV/0 ,4. 0450 BY fiwwww wed e, I

Patented Oct. 31, 1967 3,350,522 PUSH-PULL ELECTRIC SWITCH David A. Olson, Ridgway, Pa., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Filed Sept. 2, 1966, Ser. No. 577,023 9 Claims. (Ci. 200-76) This invention relates to push-pull electric switches of the general type shown in Drcssel Patent No. 2,947,832.

It is among the objects of this invention to provide such a switch which has a more positive snap action, which is easy to assemble, in which the contact pressure increases before the switch is snapped open when the switch is cycled from On to Off, and in which there is a wiping action between the contacts as the switch is being opened and closed.

In accordance with this invention, a carrier extending across the inside of a switch housing is connected to the rear end of a longitudinally movable control shaft which moves the carrier back and forth. A switch arm extends across the rear end of the shaft between the carrier and the back wall of the housing and is norm-ally inclined to the shaft. One end of the arm is pivotally connected to one end of the carrier on an axis substantially parallel to the back of the housing to permit the opposite free end of the arm to be swung forward and backward. A coil spring is compressed between the free end portion of the arm and a portion of the carrier that is spaced lengthwise of the carrier from the end to which the arm is pivotally connected. This spring normally is inclined to the arm to hold the free end of the arm in either its front or back position. The free end of the arm extends forward past the carrier into engagement with the front wall of the switch housing when the carrier is in its rear position. When the carrier is in its front position, an electric contact carried by the arm engages a fixed contact in the housing mounted on its back wall. The carrier is movable by the shaft from either of its two positions to the other far enough to move the carrier-engaging ends of the arm and spring past the point where the longitudinal axes of the arm and spring are in alignment, so that the spring thereupon can snap the free end of the arm in the direction opposite to the direction of the movement of the carrier.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a plan view;

FIG. 2 is a mainly longitudinal section taken on the line II-II of FIG. 1 showing the switch closed;

FIG. 3 is an enlarged cross section taken on the line III-III of FIG. 2;

FIG. 4 is a cross section taken on the line IVIV of FIG. 2;

FIG. 5 is an enlarged fragmentary side view with the switch housing shown in section and the switch open;

FIG. 6 is a view from the right-hand side of FIG. 3, with a portion of the switch housing broken away; and

FIGS. 7 and 8 are enlarged perspective views of the carrier and switch arm, respectively.

Referring to the drawings, principally FIG. 2, a control shaft 1 is rotatably and slidably mounted in a bushing 2 secured to the front of a suiable volume control unit 3. The bushing is threaded and adapted to extend through a hole in a mounting panel and to receive a nut for rigidly mounting the bushing in place. The shaft has a non-circular rear portion 4 that is splined in a head 5 of insulating material rotatably mounted in the volume control housing. The head carries the usual spring contact 6 that slidingly engages a resistance element 7 in the volume control unit. The rear end of the shaft extends back through a central opening 8 in the back of the volume control and into a switch housing 9, which may be made of an insulating material. The back of the volume control housing forms the front wall of the switch housing, which is provided with a back wall parallel to the front wall. The switch housing also has an integral side wall. The switch housing may be connected to the volume control housing in various ways, one way being by cars 10 struck out of the control housing and bent into notches 11 in the side of the switch housing.

Inside of the switch housing there is a carrier 13 (FIG. 7) made of insulating material and extending across the housing. This carrier, which is somewhat like a bar, has tongues 14 and 15 on its opposite ends that slide in grooves 16 in the adjoining side wall of the housing so that the carrier can move back and forth in the housing in a straight line only. For producing this movement of the carrier, the front of it is provided centrally with an integral boss 17 having a T-shape slot 18 in it extending from side to side in the carrier. A headed connecting member 19 is rotatably mounted in this slot and joined to the rear end of the shaft, preferably integrally. Consequently, the shaft can be turned in the carrier and can also move the carrier back and forth in the switch housing. The carrier also is provided with a large rearwardly opening recess 20 formed by the rearwardly extending end portions of the carrier that engage the back wall of the switch housing when the carrier is in its rear position shown in FIG. 5. When it is in its front position (FIG. 2) the main front surface of the carrier engages the front wall of the switch housing, with the boss 17 extending through the central opening 8 therein.

A pair of parallel electric terminals 22 in back of the switch housing extend forward through its back wall, from which they project forward a short distance to form electric contacts 23. In order to engage the fixed contacts, one or more movable contacts are provided. A single bridging contact 24 for engaging both fixed contacts simultaneously is shown. This bridging contact is carried by an arm 25 (FIG. 8) that is formed from a plate of insulating material. In either its On (FIG. 2) or its 01f (FIG. 5) position the arm is inclined to the control shaft and extends across it in carrier recess 20. One end of the arm, the outer end, is pivot-ally connected to the carrier on an axis that is substantially parallel to the back wall of the switch housing so that the inner or free end of the arm can be swung back and forth.

The preferred way of making this pivotal connection is to provide the inner surface of the adjoining rearwardly projecting end portion of the carrier with a notch or notches 27 extending transversely thereof, and to round the outer end of the arm so that it can rock in the notches. The arm is wider than the carrier and its outer end is bifurcated in order to straddle the end portion of the carrier as shown in FIG. 3 and thereby prevent the arm from moving transversely of the carrier. For the same reason, the rear portion of the carrier can be provided with a tongue 28 between the notches that projects into a notch 29 in the arm.

The free end of the arm has extensions 31 extending at right angles thereto forward across the opposite sides of the carrier and into engagement with the front wall of the switch housing when the free end of the arm is in its front position shown in FIG. 5. Between these extensions the free end of the arm is spaced from the adjacent end portion of the carrier, and a coil spring 32 is compressed between them. The spring is held in place by tiny

spherical nubs

33 and 34 integral with the arm and carrier, respectively, and projecting into the opposite ends of the spring. As the free end of the arm is swung back and forth, the

ends of the spring can rock on these nubs. To facilitate such rocking and eliminate any tendency for the spring to bind on the nubs, the arm and carrier are formed on opposite sides of the nubs with relatively sharp edges and 36 that engage the end loops of the spring on their diameters. Consequently, as the spring is swung back and forth it rocks on these sharp edges.

It will be seen that when the switch is off, that is, when the carrier is in its rear position shown in FIG. 5, the arm and spring converge toward the front of the housing and the arm extensions 31 are pressed against the front wall. The arm and spring thus are located principally in the front part of the carrier recess. To turn on the switch, the control shaft is pulled, which moves the carrier forward in the housing. However, the free end of the arm cannot move forward because its extensions 31 already engage the front wall. During forward movement of the carrier the outer ends of the arm and spring are moved forward by it and past the point where the longitudinal axes of the arm and spring are in alignment. The spring is compressed as it and the arm are brought into line, but the moment their outer ends pass the alignment point the spring can start to expand and will snap the free end of the arm backward until the contact carried by it strikes the fixed contacts as shown in FIG. 2.

To open the switch, the control shaft is pushed. Since the free end of the switch arm cannot move backward with the carrier because of engagement with the fixed contacts, the outer ends of the arm and spring are moved backward past the point where the longitudinal axes of the arm and spring are aligned, whereupon the compressed spring expands and swings the arm forward again. It will be noted that while the carrier is moving backward and the spring therefore is being compressed, the coil spring causes the bridging contact to exert an increasing pressure against the fixed contacts until the moment the arm is snapped forward. There is no diminishing engagement and no arcing. Also, while the outer end of the arm is moving backward it causes the bridging contact to slide on the fixed contacts and this wiping engagement helps to keep the contacts clean.

As the bridging contact 24 should engage flat against the fixed contacts at all times, the bridging contact is rather loosely mounted on the switch arm. This can be done by making the bridging contact from a metal bar provided with a central projection engaging the back of the arm and also provided with forwardly projecting end portions that extend through notches 38 in the edges of the arm. The front ends of the end portions of the bar are increased in width to hold the bar in place, as shown in FIG. 5.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we 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. A push-pull electric switch comprising a housing having front and back walls connected by a side wall, a fixed electric contact in the housing mounted on the back wall, the front wall having a central opening through it, a bushing rigidly mounted in front of the front wall in line with said opening, a control shaft slidably mounted in the bushing and extending back to said housing, a carrier extending across the inside of the housing, means connecting the rear end of said shaft to the carrier for moving it back and forth when the shaft is pushed and pulled, a switch arm extending across the rear end of the shaft between the carrier and the back wall of the housing and normally inclined to the shaft, one end of the arm being pivotally connected to one end of the carrier on an axis substantially parallel to said back wall to permit the opposite free end of the arm to be swung forward and backward, a coil spring compressed between the free end portion of the arm and a portion of the carrier spaced lengthwise of the carrier from its said one end, the spring normally being inclined to the arm to hold said free end in either its front or back position, the free end of the arm extending forward past the carrier into engagement with said front wall when the carrier is in its rear position, and an electric contact carried by the arm and engaging said fixed contact when the carrier is in its front position, the carrier being movable by the shaft from either of said carrier positions to the other far enough to move the carrier-engaging ends of said arm and spring past the point where the longitudinal axes of the arm and spring are in alignment, whereby the spring can thereupon snap the free end of the arm in the direction opposite to the direction of movement of the carrier.

2. A push-pull electric switch as recited in claim 1, in which the ends of said carrier and the adjoining side wall of said housing are provided with registering tongues and grooves for guiding the carrier forward and backward in the housing, and said shaft-connecting means is rotatably connected to the carrier.

3. A push-pull electric switch as recited in claim 1, in which the carrier has a rearwardly opening recess receiving said arm and spring, and said free end of the switch arm straddles the carrier at one end of said recess when the carrier is in its rear position.

4. A push-pull electric switch as recited in claim 1, in which said carrier is notched for pivotally receiving said one end of the switch arm.

5. A push-pull electric switch as recited in claim 1, in which said carrier is provided with an edge parallel to said pivotal axis and engaging the adjoining end of the coil spring along a diameter thereof, and a spherical nub projects from said edge into the coil spring.

6. A push-pull electric switch as recited in claim 1, in which said portion of the carrier is at the end thereof opposite its said one end and projects rearwardly, and said arm portion is spaced inwardly from said carrier portion, whereby the arm and coil spring converge toward the front wall when the carrier is in its rear position and the arm and spring converge toward the back wall when the carrier is in its front position.

7. A push-pull electric switch as recited in claim 6, in which the electric contact carried by said switch arm is located between the coil spring and the pivoted end of the arm.

8. A push-pull electric switch as recited in claim 6, in which said one end of the carrier projects rearwardly and is provided in its inner surface with a notch pivotally receiving said one end of the switch arm.

9. A push-pull electric switch as recited in claim 6, in which said one end of the carrier projects rearwardly and is straddled by the pivoted end of the switch arm and is notched in its inner surface for receiving the central portion of the pivoted end of the arm to provide the pivotal connection.

References Cited UNITED STATES PATENTS 12/1956 Kommer 200--67 9/1966 Schwartz 200-67

Claims

1. A PUSH-PULL ELECTRIC SWITCH COMPRISING A HOUSING HAVING FRONT AND BACK WALLS CONNECTED BY A SIDE WALL, A FIXED ELECTRIC CONTACT IN THE HOUSING MOUNTED ON THE BACK WALL, THE FRONT WALL HAVING A CENTRAL OPENING THROUGH IT, A BUSHING RIGIDLY MOUNTED IN FRONT OF THE FRONT WALL IN LINE WITH SAID OPENING, A CONTROL SHAFT SLIDABLY MOUNTED IN THE BUSHING AND EXTENDING BACK TO SAID HOUSING, A CARRIER EXTENDING ACROSS THE INSIDE OF THE HOUSING, MEANS CONNECTING THE REAR END OF SAID SHAFT TO THE CARRIER FOR MOVING IT BACK AND FORTH WHEN THE SHAFT IS PUSHED AND PULLED, A SWITCH ARM EXTENDING ACROSS THE REAR END OF THE SHAFT BETWEEN THE CARRIER AND THE BACK WALL OF THE HOUSING AND NORMALLY INCLINED TO THE SHAFT, ONE END OF THE ARM BEING PIVOTALLY CONNECTED TO ONE END OF THE CARRIER ON AN AXIS SUBSTANTIALLY PARALLEL TO SAID BACK WALL TO PERMIT THE OPPOSITE FREE END OF THE ARM TO BE SWUNG FORWARD AND BACKWARD, A COIL SPRING COMPRESSED BETWEEN THE FREE END PORTION OF THE ARM AND A PORTION OF THE CARRIER SPACED LENGTHWISE OF THE CARRIER FROM ITS SAID ONE END, THE SPRING NORMALLY BEING INCLINED TO THE ARM AND TO HOLD SAID FREE END IN EITHER ITS FRONT OR BACK POSITION, THE FREE END OF THE ARM EXTENDING FORWARD PAST THE CARRIER INTO ENGAGEMENT WITH SAID FRONT WALL WHEN THE CARRIER IS IN ITS REAR POSITION, AND AN ELECTRIC CONTACT CARRIED BY AN ARM AND ENGAGING SAID FIXED CONTACT WHEN THE CARRIER IS IN ITS FRONT POSITION, THE CARRIER BEING MOVABLE BY THE SHAFT FROM EITHER OF SAID CARRIER POSITIONS TO THE OTHER FAR ENOUGH TO MOVE THE CARRIER-ENGAGING ENDS OF SAID ARM AND SPRING PAST THE POINT WHERE THE LONGITUDINAL AXES OF THE ARM AND SPRING ARE IN ALIGNMENT, WHEREBY THE SPRING CAN THEREUPON SNAP THE FREE END OF THE ARM IN THE DIRECTION OPPOSITE TO THE DIRECTION OF MOVEMENT OF THE CARRIER.