US3013131A

US3013131A - Snap switch

Info

Publication number: US3013131A
Application number: US689699A
Authority: US
Inventors: Robert N Nanninga
Original assignee: CONTAC CORP
Current assignee: CONTAC Corp
Priority date: 1957-10-11
Filing date: 1957-10-11
Publication date: 1961-12-12
Anticipated expiration: 1978-12-12

Description

Dec. 12, 1961 R. N. NANNINGA 3,013,131

SNAP SWITCH Filed Oct. 11, 1957 INVENT OR. ROBERT N NANN/NGA mahw ATTORNEYS 3,013,131 SNAP SWITCH Robert N. Nanninga, Pasadena, Calif., assignor to Contac Corporation, South Pasadena, Calif, a corporation of California Filed Oct. 11, 1957, Ser. No. 689,699 9 Claims. (Cl. 200-67) This invention relates to switches, and more particularly to snap switches having rapid operating contact members for opening and closing contact elements.

In many instances the operating member of switches, particularly snap switches, takes the form of a contact spring which is stressed internally so as to set up a deformation to provide an area of high sensitivity to actuating forces for producting a rapid movement of another movable section of the spring. A band, staple or other means may be used to retain a deformation in a contact spring creating internal stresses within the spring. The deformed spring may then be mounted in a snap switch casing in operative relationship relative to other contacts. In another arrangement, the snap switch casing retains the cont-act spring in a deformed state setting up internal stresses and an area of high sensitivity to actuating forces for producing a rapid movement of the movable contact end of the contact spring.

Usually the production of snap switches having contact springs which are normally under internal stresses, requires the additional step of connecting portions of the spring together to set up the deformation and internal stresses. Also, the useful life of a contact spring in a snap switch is materially reduced as a result of the constantly present internal stresses inducing material fatigue.

These difiiculties have been overcome in the present invention by providing an improved snap switch arrangement having a preformed contact spring in which internal stresses are set up only during the period of operation of the switch.

In addition to overcoming the foregoing difficulties, the present invention provides a snap switch having the advantage of wider range of switch operation which can be accurately predetermined in the prefonnation of the contact spring. The switch operations being considered include pre-travel, over-travel, and operating dilferential. These advantages permit a wider use of the present type of switch as well as reducing the number of rejects.

In the preferred embodiment, the snap switch includes a base on which one end of an elongated contact spring is secured to provide a cantilever mounting of the spring and at least one other contact opposing the movable contact section of the contact spring. The contact spring has a longitudinal slot, a raised center portion about the center of the slot extending over the base of the snap switch, and a lateral groove extending the width of the contact spring between the raised portion of the spring and the suspended movable contact section. A channel is formed in the base which opens below the longitudinal slot and inner edges of the spring providing shoulders adjacent the vertical sides of the channel which are undercut to project vertically adjacent the lateral outer edges of the contact spring. The space provided by the channel permits the inner edges of the spring to be displaced downwardly while the horizontal surface of the shoulders abut the portion of the spring adjacent the raised portion. The contact spring is actuated in response to an operating pressure on the inner edges of the slot within the raised portion. Movement of the inner edges and adjacent portion of the raised portion downwardly produces a snap operation in the form of an extremely rapid upward movement of the movable contact section of the spring for engaging and disengaging the other Patented Dec. 12, 1961 switch contact. The downward movement of the inner edges is usually accompanied by an upward movement of the outer edges of the spring from the normal preformed position.

The invention is explained with reference to the drawings, in which:

FIG. 1 is a perspective view of the invention;

FIG. 2 is a top view of the invention shown in FIG. 1 with the cover removed; and

FIG. 3 is a view of the invention taken partially in section on the line 3-3 of FIG. 2.

The illustration of FIG. 1 shows a snap switch 10 including a casing 12 having a top opening providing access to the switch elements. The top opening is closed by a cover plate 14 seating in a ridge formed in the inner periphery of the casing wall. An opening 15 in the cover plate 14 permits the snap switch actuator 16 to project outside the enclosure. If desired, the casing and cover plate openings may be fitted with fluid-tight seals whereby the entire snap switch may be disposed in an explosive gas atmosphere or suspended in liquid such as oil without the gases or liquids entering the casing.

In FIG. 3, the positions of the various switch elements are shown wherein a base 18, shown in cross-section, is formed of plastic for embedding the switch elements. The switch elements include a stationary contact assembly 20 having a. conductive strap extending laterally into the top of the switch chamber 1? and a contact element 21 on the end of the strap inside the chamber. Another contact assembly 22. includes a conductive strap projecting into the bottom of the switch chamber 19 disposing a contact element 23 in opposed and spaced relationship to the contact element 21. A conductive strap 24 extends from the bottom of the switch casing to the top of the block portion of the base 18 for connecting the movable contact spring outside the switch casing 12. A con tact spring 26 which can be stamped and preformed from a fiat sheet of Phosphor bronze or the like is electrically and mechanically connected to the strap 24 by welding, brazing, etc., or by other suitable means such as a rivet 28, as shown.

In the preferred embodiment, the contact spring 26 is mounted on the inclined top surface of a block forming a portion of the switch base 18. In the normal or nonactu-ated position of the contact spring 26, the inclined surface projects the movable end, including the contact element 27, into engagement with the contact element 23 in the bottom of the switch chamber 19. The contact spring .26 is mounted over a recess or channel 3t formed in the base 18 below the contact spring 26. The portions of the base adjacent the sides of the channel 3% form shoulders 31 and 3'2 having undercut upper surfacw supporting the spring contact 26 and vertical portions about the outer lateral edges of the contact spring 26 to prevent spreading or lateral displacement of the spring during actuation.

A longitudinal slot 34 is formed in the contact spring 26 extending substantially the length of the spring. The slot may widen as shown to provide an aperture 36 which decreases the longitudinal rigidity of the spring 26. Controlling the size of the aperture 36 varies the amount of actuating or operating force needed at the raised portion 38 in order to actuate the contact spring as.

Internal stresses in the contact spring 26 have been avoided and the spring has been preformed to provide a raised center portion 38 above the channel 30 and about the slot 34. A lateral groove 4% is also preformed in the contact spring 26 and extends across the width of the contact spring between the raised center portion 38 and the movable section of the spring. The lateral groove 40 provides a longitudinal bending or flex line of the contact spring 26.

The snap switch unit may be mounted for use by means of mounting

holes

44 and 46 passing transversely through the bottom of the base. Preferably, one of the holes, e.g., hole 46 is widened or elongated, as shown in cross section, for variable spacing attaching-means such as screws or the like. Both the movable and stationary contacts are connected to other circuitry by terminals 48, 50 and 52 which may include means, such as the lugs or screws as shown, which are threaded in the conductor straps for securing lead wires or the like to the contact assemblies at these terminals.

In operation, the preferred embodiment includes the normally closed

contacts

23 and 27 and normally open

contacts

21 and 27. Downward pressure on plunger or actuator 16 will operate the contact spring 26 to quickly break the circuit through

contact elements

23 and 27 and make a circuit through closure of

contacts

21 and 27. This operation follows the application of operating pressure on the actuator causing it to move downwardly along with the inner area or edges of the contact spring about the slot 34 within the raised portion 38 of the contact spring 26.

Preferably, the outer lateral edges of the contact spring 26 are restrained from spreading sideways or displacement by the vertical portions of

shoulders

31 and 32 defining the undercut portion seating the spring 26 and abutting the outer lateral edges of the contact spring. The movement of the raised portion 38 downwardly, resulting from downward operating pressure being exerted on the actuator 16, produces a lateral bow in the spring in which the outer edges of the contact spring 26 may tend to rise as the inner edges about the slot 34 move downwardly.

At the same time, a longitudinal bow of the contact spring 26 is produced. The longitudinal bow is concaveconvex, as is the lateral bow of the contact spring. The longitudinal movement produces the snap action desired wherein a predetermined operating pressure on the actuator is required to depress the raised portion 38. A ter the predetermined minimum operating pressure is reached, the raised portion is quickly moved downwardly producing a snap action causing the movable section, more particularly the movable contact, to move rapidly from a normal to actuated position. The movable contact 27 must travel a greater distance, i.e., from its normalposition to its operated position, in the same time the raised portion 38 moves from its normal to its depressed position. The movement of the contact 27 therefore, is even more rapid than the raised portion 38.

During the snap action operation of the contact spring 26, the movable contact 27 disengages contact 23 and enga es contact 21. Upon release of the actuator 16, i.e., decreasing the pressure on the actuator below the operating pressure less the operating differential, the resiliency of the spring causes its depressed raised portion to return producing a snap action resulting in the rapid movement of the movable contact 27 from its upper position in the chamber 19 to the lower position in a chamber thereby disengaging contact 21 and engaging contact 23.

Operation of the movable contact provides fast makeand-break operations and permits the associated circuitry to open a circuit connected to terminals 56 and 52 through the stationary contact assembly 22 and movable contact assembly and close a circuit connected to terminals 48 and 52 through the stationary contact assembly 29 and the movable contact assembly, including the contact spring 26.

The snap action or rapid movement of the movable spring contact element produces a fast make-and-break action reducing arcing of the contacts. While reduction in arcing of contacts in turn reduces contact wear and need of replacement, the reduction in fatigue and wear on the movable elements aids in providing a product which is competitive with and capable of being used along with static components. Many advantages are found in a completed unit in which the pro-travel, over-travel, and operating differential are predeterminable and precisely controlled in the preformaticn of the contact spring.

I claim:

1. In a snap switch including a base, an elongated contact spring having a longitudinal slot, said elongated contact spring having a preformed unstressed raised outwardly convex portion forming a sensitive area adjacent to a portion of said slot, means for mounting the contact spring on the base securing the end of the spring adjacent to the sensitive area to the base whereby the opposite end of the contact spring and the sensitive area are suspended for movement and at least a portion of the contact spring section adjacent to the sensitive area abuts the base, said contact spring being responsive to operative actuating forces exerted against the sensitive area to set up internal stresses in the contact spring causing rapid movement of the opposite end of the movable contact spring, said internal stresses being present only during operation of the switch.

'2. In a snap switch including a base, an elongated contact spring having a longitudinal center slot extending a substantial portion of the length of the spring, said elongated contact spring having a preformed unstressed raised outwardly convex portion forming a sensitive area adjacent to a portion of said slot, means for mounting the contact spring on the base securing the end of the spring adjacent to the sensitive area rigidly to the base and suspending the opposite end of the contact spring and the raised sensitive area for movement relative to the base whereby actuating forces exerted downwardly on the sensitive area set up internal stresses in the contact spring causing rapid movement of the opposite end of the movable contact spring, said internal stresses being present only during operation of the switch.

3. In a snap switch including a base, an elongated contact spring having a longitudinal slot extending substantially the length of said spring, said elongatedcontact spring having a preformed unstressed raised outwardly convex portion forming a sensitive area adjacent to a portion of said slot, means for mounting the contact spring on the base securing the end of the spring adjacent to the sensitive area rigidly to the base and suspending the opposite end of the contact spring and the sensitive area for transverse movement, said contact spring being rcsponsive to operative actuating forces exerted against said ensitive area to set up internal stresses present in said spring only during operation thereof to produce a rapid movement of the movable contact section and a rapid return movement upon removal of the operating forces.

4. In a snap switch including a base, a preformed contact spring having a longitudinal slot extending a substantial portion of the length of the spring, said elongated contact spring having a preformed unstressed raised outwardly convex portion forming a sensitive area adjacent to a portion of said slot, means for mounting the contact spring on the base securing the end of the spring adjacent to the sensitive area rigidly to the base and suspending the opposite end of the contact spring and the sensitive area for movement, said contact spring being responsive to an operating force exerted against the sensitive area to how the spring laterally and longitudinally to set up internal stresses present in said spring only during operation thereof to produce a snap movement of the opposite end of the movable contact spring.

5. A snap switch including a base and at least a pair of contacts, an elongated contact spring for one of the contacts having a longitudinal slot extending substantially the length of the spring, a lateral groove formed in said spring dividing the spring into a movable contact section and an actuating section, means for mounting the contact spring on the base securing the end of the spring in the actuating section rigidly to the base suspending the movable contact section and projecting the contact in spaced and opposed relationship with the other contact, said spring having a raised portion about the slot in the actuating section suspended above the base for vertical movement wherein the lateral edges of the actuating section adjacent the raised portion abut the base to prevent lateral movement of the spring in response to operative downward actuating forces exerted on the raised section and a snap action movement of the movable contact section for engaging and disengaging said contacts.

6. A snap switch comprising a base, an elongated contact spring secured at one end to the base to provide a cantilever mounting of the spring, at least one other contact element positioned on the base for engagement with the end of the movable contact section of the contact spring, said contact spring having a longitudinal slot, a raised center portion about a portion of the slot extending over the base, and a lateral groove extending substantially across the width of the spring between the raised section and the suspended movable contact section, a channel in the base opening below the slot and inner edges of the spring which extend over the base, shoulders formed by the vertical sides of the channel abutting the lateral outside edges of the spring preventing displacement of the outer edges abutting the shoulders in response to an operating pressure on the inner edges of the slot within the raised portion to produce a snap operation of the movable contact end portion of the spring for engaging and disengaging the other contact.

7. In a snap switch including a base, an elongated contact spring having a contact element mounted on the movable end of said spring for engaging another contact element of the switch, a block forming a portion of said base, means for rigidly securing the other end of the contact spring on the block to provide a cantilever mounting of the spring, a longitudinal slot in said spring, a preformed unstressed raised center portion sensitive area formed in said spring above said block and about said slot, said contact spring being responsive to a force on at least the inner edges at the raised center portion to set up internal stresses present in said spring only during operation thereof to produce a snap operation for engaging and disengaging the movable contact and said other contact.

8. In a snap switch, a movable contact arrangement comprising elongated contact spring preformed from flat resilient material, a longitudinal slot extending a substantial portion of the length of the spring, a base for securing one end of the contact spring to form a cantilever, a contact element mounted in the opposite movable end, a channel in said base opening below the slot and inner edges of the spring and forming shoulders in the top of the base abutting at least the outer edges of the spring adjacent the channel and suspending the inner edges of the spring section above the channel permitting the inner edges to enter the channel, a center portion of the spring section along said slot and above said channel being preformed to rise above the remainder of the secured end of the spring wherein said raised portion is responsive to pressure forcing an inner edge down to operate the movable section of the contact spring.

9. A snap switch, an elongated snap action contact spring preformed from flat resilient conductive material and having a movable contact end portion for engaging and disengaging at least one other contact, a base for securing one end of said spring providing a cantilever disposing the remainder of the spring for movement, a longitudinal slot formed in said spring producing inner edges, a lateral groove extending substantially across said spring adjacent said base permitting said spring to bend along said groove, a center raised portion above said base extending on both sides of said slot, a channel in said base extending below the inner edges of the spring from said raised center section to a side of said base for receiving the adjacent inner edges of the spring upon pressure being applied to said raised portion forcing the raised portion downwardly, shoulders supporting the spring adjacent the raised portion alongside the channel in the base and abutting the lateral onter edges of the spring adjacent the raised section to prevent lateral displacement whereby the spring is responsive to operating pressures on the raised portion on both sides of the slot to force the inner edges of the raised portion of the spring downwardly causing the movable contact end of the spring to operate for engaging and disengaging the other contact.

References (fired in the tile of this patent UNITED STATES PATENTS 2,266,537 Elmer Dec. 16, 1941 2,275,642 Nordberg Mar. 10, 1942 2,332,883 Abramson Oct. 26, 1943 2,776,347 Allen Jan. 1, 1957 2,806,927 Allen Sept. 17, 1957 FOREIGN PATENTS 272,398 Switzerland Mar. 16, 1951 741,395 Germany Nov. 10, 1943