US3349358A

US3349358A - Snap switch

Info

Publication number: US3349358A
Application number: US578190A
Authority: US
Inventors: Jr William F Cassedy
Original assignee: STACKOPLE CARBON Co
Current assignee: STACKOPLE CARBON Co
Priority date: 1966-09-09
Filing date: 1966-09-09
Publication date: 1967-10-24
Anticipated expiration: 1984-10-24

Description

Oct. 24, 1967 w. F. CASSEDY, JR 3,349,358

SNAP SWITCH Filed Sept. 9, 1966 2 Sheets-Sheet 1 INVENTOR. MA .4 MM E CASS'OV, JA

ATTORNEYS.

Oct. 24, 1967 w. F. CASSEDY, JR I 3,349,358

SNAP SWITCH Filed Sept. 9, 1966 2 Sheets-Sheet 2,

k 1 gal If INVENTOR. v Mil/4M E CASSEDKJR.

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United States Patent 3,349,358 SNAP SWITCH William F. Cassedy, Jr., Short Hills, NJ., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Filed Sept. 9, 1966, Ser. No. 578,190

7 Claims. (Cl. 338-172) This invention relates to electric snap switches and has among its objects the provision of a switch which is inexpensive, which is made from a minimum of parts, which is very easy to assemble, which is very thin, in which the movable contact moves in a direction opposite to that in which the control shaft is turned, and in which the movable contact is a resilient metal loop.

In accordance with this invention, an insulating base is provided witha central bos's having a pair of side surfaces converging to a point. Surrounding the boss is a movable contact in the form of a metal spring strip that has been bent into a loop and is disposed on edge close to the base. The loop has a flexible section extending across the point of the boss. This section is provided centrally with an inwardly bent tapered portion forming a cam follower that normally presses against one of the inclined side surfaces of the boss. The rest of the loop is spaced from the boss, but a portion of it opposite to the cam follower is anchored to a terminal that is mounted on the base at the side of the boss opposite the point of the boss. A fixed contact is mounted on the base in a position to be pressed against by the loop at one end of its above-mentioned flexible section while its cam follower presses against the side surface of the boss nearest the fixed contact. Also mounted on the base is a stop that is in a position to be pressed against by the loop at the opposite end of its flexible section while the cam follower presses against the other side surface of the boss. Located between the point of the boss and the terminal there is a rotatable shaft, with which is connected a laterally tapered cam for rotation by the shaft inside the loop into engagement with the side of the cam follower that is engaging a side surface of the boss. As the cam is rotated further, it moves across the point of the cam follower and, since the point of the cam projects beyond the point of the boss, the cam springs the flexible section of the loop outwardly far enough for the cam follower to snap over to the other side of the boss.

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

FIG. 2 is a side view, partly broken away in section;

FIG. 3 is an enlarged fragmentary rear view with the insulating base mostly broken away; and

FIG. 4 is an enlarged fragmentary cross section taken on the line IV-IV of FIG. 1.

Referring to the drawings, a control shaft 1 is rotatably mounted in a bushing 2 formed on a metal mounting plate 3 clamped against the insulating front wall 4 of a housing by bent tabs 5 projecting from the cylindrical metal side wall 6 of the housing. The inner end of the shaft is reduced and rotatably mounted in a central socket 7 (FIG. 4) of the back wall 8 of the housing, which forms the insulating base of the switch. Inside the housing, a head 10 of insulating material is rigidly mounted on the shaft so that it will be turned with it. Secured to the front of the head is the usual spring contact 11 that slides over a resistance element 12 mounted on the front wall of the housing. The head is provided with a lateral projection 13 which, when the switch is turned to its Off position, strikes the side of a stop 14 (FIG. 3) formed by a struck-out portion of the housing side wall. The stop also limits rotation of the head in the opposite direction.

3,349,358 Patented Oct. 24, 1967 Inside the housing, the insulating base 8 is provided centrally with a thin boss 16 that has a pair of side surfaces converging to a point as shown in FIG. 3. Although the angle formed by these two surfaces is not critical, the one shown is about The movable contact of the switch is a spring loop 17 that is formed by bending a metal spring strip, preferably into generally rectangular shape with two substantially parallel sides. The loop surrounds the boss with one edge of the strip close to the insulating base. An end portion of the loop is anchored to an electric terminal 18 located at the side of boss 16 opposite the point of the boss. This terminal extends through the base, in which it is rigidly mounted. The terminal is provided inside the housing with a notch 19 (FIG. 2) on a line extending from the point of the boss through the center of the shaft to the terminal. At the inner or open end of the notch its side walls are provided with nibs 20 projecting toward each other. The opposite ends of the spring strip forming the loop are turned inwardly toward the boss and extend through the terminal notch. These inturned ends are provided with tiny recesses 21 that receive the nibs, and the tendency of the ends to spring away from each other holds them in place.

This manner of connecting the spring loop to the terminal holds the loop in place and permits the free end of the loop to be swung back and forth. The free end of the loop that extends across the point of boss 16 is a flexible section, which is provided centrally with an inwardly bent tapered portion forming a cam follower 22 that engages one side or the other of the boss near its point. Since this engagement distorts the loop laterally, the loop is always under tension and presses tightly against the boss.

When the cam follower 22 of the loop is engaging the left-hand side of the boss, as shown in full lines in FIG. 3, the side of the loop at the left-hand end of its flexible end section engages a stop 24 formed as a projection on the inner surface of the insulating base. Spaced from the opposite side of the loop there is a fixed contact 25, which has a laterally extending portion parallel to terminal 18 and extending outwardly through the base in which it is locked. The exposed portion of the fixed contact forms the other terminal 26 of the switch. The fixed contact is so positioned that while the cam follower of the loop is engaging the side of the boss adjacent that contact, as shown in dotted lines in FIG. 3, the loop will tightly engage the contact and close the circuit.

In order to swing the spring loop back and forth between stop 24 and the fixed contact, there is a laterally tapered cam 28 located inside the loop. This cam is rigidly connected with the control shaft, preferably by being rigidly mounted on head 10 attached to the shaft. When the point of the cam is aligned with the point of boss 16, part of the cam is disposed between the boss and head and the cam point projects slightly beyond the boss. Therefore, when the cam is rotated toward and into engagement with whichever side of the cam follower 22 that happens to be engaging a side surface of the boss, the cam will first spring the flexible end section of the loop outwardly away from the boss and then, as the point of the cam slides across the point of the cam follower, the latter will snap over to the other side surface of the boss. This action is illustrated in FIG. 3, where the switch is shown in its Off position with cam follower 22 engaging the left-hand side of the boss. At this time the head 10 is in its extreme clockwise position with its projection 13 engaging stop 14. The cam 28 is pointing away from the right-hand side of the boss. To close the switch, the shaft is turned to rotate the cam counterclockwise, which causes it to engage the right-hand side of the cam follower. As the movement of the cam continues to the left-hand side of the boss,

the point of the cam follower is forced to slide outwardly toward the point of the cam shown in dotted lines because stop 24 prevents the loop from being moved further toward the left. When the two points meet, the cam follower snaps over to the right-hand sides of the cam and boss and the loop then engages the fixed contact 25 to close the switch. The cam can continue in a counterclockwise direction as the shaft is turned to operate the variable resistor in the housing. To open the switch, the shaft is turned in the opposite direction so that the cam will engage the left-hand Side of the cam follower, force it outwardly and then permit it to snap back to the full line position shown in FIG. 3. It will be seen that the loop always snaps in a direction opposite to the direction of movement of the cam. Another function of stop 24 is that by limiting movement of the loop to the left, the distance that the cam must be turned in order to close the switch is always the same.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I 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 snap switch comprising an insulating base, a central boss on said base provided with a pair of side surfaces converging to a point, a movable contact in the form of a metal spring strip bent into a loop surrounding said boss and disposed on edge close to the base, said loop having a flexible section extending across said point of the boss and provided centrally with an inwardly bent tapered portion forming a cam follower normally pressing against one of said boss side surfaces, the rest of the loop being spaced from the boss, a terminal mounted on said base at the side of the boss opposite its point, a portion of the loop opposite said cam follower being anchored to the terminal, a fixed contact mounted on the base in a position to be pressed against by the loop at one end of said flexible section while said cam follower presses against the side surface of the boss nearest the fixed contact, a stop on said base in a position to be pressed against by the loop at the opposite end of said flexible portion while said cam follower presses against the other side surface of the boss, a rotatable shaft having its axis located between said boss point and terminal, and a laterally tapered cam inside the loop rigidly connected with the shaft for rotation thereby into engagement with the side of said cam follower that is engaging a side surface of the boss and then across the point of the cam follower, the point of said cam projecting beyond the point of the boss so that said cam follower will be sprung outwardly by the cam far enough to snap over to the other side surface of the boss.

2. An electric snap switch as defined in claim 1, in which said movable contact loop has a pair of substantially parallel sides.

3. An electric snap switch as defined in claim 1, in which said movable contact loop is rectangular.

4. An electric snap switch as defined in claim 1, in which the portion of the movable contact loop anchored to said terminal is formed by the opposite ends of said spring strip.

5. An electric snap switch as defined in claim 4, in which said terminal is provided with a notch, and the opposite ends of said spring strip are turned inwardly toward said boss and are anchored in said notch.

6. An electric snap switch as defined in claim 1, including a head rigidly mounted on said shaft close to the loop, a variable resistor contact carried by the side of the head opposite said movable contact loop, and a resistance element engaged by said resistor contact.

7. An electric snap switch as defined in claim 6, in which said cam is rigidly mounted on said head.

References Cited UNITED STATES PATENTS 2,059,712 11/1936 Schellenger 200- 68 X 3,259,709 7/1966 Hemmings 200 3,324,261 6/1967 Burns 200-67 ROBERT K. SCHAEFER, Primary Examiner.

D. J. SMITH, Assistant Examiner.