US3816681A

US3816681A - Snap action switch

Info

Publication number: US3816681A
Application number: US00247011A
Authority: US
Inventors: E Lunenschloss; A Ford
Original assignee: Airpax Electronics Inc
Current assignee: Airpax Electronics Inc
Priority date: 1972-04-24
Filing date: 1972-04-24
Publication date: 1974-06-11
Anticipated expiration: 1991-06-11
Also published as: JPS4921669A; JPS5329824B2

Abstract

A self-restoring snap action switch movable between normal and actuated positions and including an elongated, resilient, conductive leaf strip mounted between seats spaced closer together than the effective length of the strip, thus bowing the strip from the plane between the seats, and provided with an upper abutment member normally in contact with the upper strip surface approximately midway between the seats for imposing oppositely bowed portions on the strip. A downwardly movable actuator abuts the upper surface of the upwardly bowed strip portion, and downward movement of the actuator tends to flatten such portion until the strip snaps to its actuated position, with its lower surface abutting a lower abutment member in general vertical alignment with the upper abutment member. Stop means limit downward movement of the upwardly bowed portion of the strip. When the actuator contacts the strip between the apex of its upwardly bowed portion and the adjacent seat, movement of the strip creates wiping contact between its surfaces and the upper and lower abutment members. One end of the strip may be V-notched to facilitate assembly of the strip to a terminal post or seat received in the V. The strip is electrically connected to external circuitry, desirably through its contact with one or both of the seats, which thus constitute a common terminal of the switch. At least one of the abutment members is conductive and is connectable to external circuitry through a terminal which may be either normally open or normally closed depending on the abutment member chosen.

Description

United States Patent [191 Lunenschloss et al.

[ June 11, 1974 SNAP ACTION SWITCH [75] Inventors: Edward V. Lunenschloss, Arcadia;

Anthony R. Ford, West Covina, both of Calif.

[73] Assignee: Airpax Electronics Incorporated,

South El Monte, Calif.

[22] Filed: Apr. 24, 1972 [21] Appl. No.: 247,011

Primary ExaminerDavid Smith, Jr. Attorney, Agent, or Firm-Miketta, Glenny Poms & Smith [57] ABSTRACT A self-restoring snap action switch movable between normal and actuated positions and including an elongated, resilient, conductive leaf strip mounted between seats spaced closer together than the effective length of the strip, thus bowing the strip from the plane between the seats, and provided with an upper abutment member normally in contact with the upper strip surface approximately midway between the seats for imposing oppositely bowed portions on the strip. A downwardly movable actuator abuts the upper surface of the upwardly bowed strip portion, and downward movement of the actuator tends to flatten such portion until the strip snaps to its actuated position, with its lower surface abutting a lower abutment member in general vertical alignment with the upper abutment member. Stop means limit downward movement of the upwardly bowed portion of the strip. When the actuator contacts the strip between the apex of its upwardly bowed portion and the adjacent seat, movement of the strip creates wiping contact between its surfaces and the upper and lower abutment members. One end of the strip may be V-notched to facilitate assembly of the strip to a terminal post or seat received in the V. The strip is electrically connected to external circuitry, desirably through its contact with one or both of the seats, which thus constitute a common terminal of the switch. At least one of the abutment members is conductive and is connectable to external circuitry through a terminal which may be either normally open or normally closed depending on the abutment member chosen.

4 Claims, 10 Drawing Figures SNAP ACTION SWITCH BACKGROUND AND SUMMARY OF THE INVENTION This invention relates generally to electrical switches, and more particularly to a single pole, double throw switch characterized by very rapid snap action from a normal position to an actuated position, with minimum contact bounce and teasing during the make and break movement in either direction. Physically, the switch includes a blade or leaf in the form of an elongated strip of resilient conductive material such as copper or one of the copper alloys, the strip being mounted between two seats which are spaced more closely together than the unstressed length of the strip. Thus, if not otherwise confined, the strip would assume a bowed or arcuate configuration on one side or the other of the plane joining the two seats.

In accordance with the invention, and assuming for convenience of reference that the two seats are disposed in a common horizontal plane, an upper abutment member is provided, generally midway of the length of the strip, for contacting the upper surface of the strip and thereby imposing on the strip as a whole two oppositely curved bowed portions, extending on opposite sides of the above mentioned plane. A second, or lower, abutment member is provided in general vertical alignment with the first named abutment member, for limiting the downward movement of the central portion of the strip upon actuation. Either or both of the abutment members mentioned may be conductive and, when connected to external circuitry, may thus serve as a contact for the switch. The conductive leaf spring itself is connected to external circuitry by reason of its contact with one or both of the seats above mentioned, between which the leaf strip is maintained in stressed condition.

Means are provided for actuating the switch from its normal position to a second or actuated position. Such means, in accordance with the invention, stress the upwardly curved bowed portion of the strip by forcing such portion downwardly until the strip snaps to its second or actuated position, breaking contact with the upper abutment member and making contact with the lower abutment member. Desirably the actuator may take the form of a plunger or the like which includes a downwardly directed tip contacting the upper surface of the leaf strip, between the apex or zenith of the upwardly curved bowed portion and the adjacent seat. As will be later understood, application of the actuating downward force on the leaf strip in that area causes sliding movement between the upper abutment member and the leaf strip prior to breaking of that contact, and also causes sliding movement between the lower abutment member and the contact strip immediately following the making of that contact. Thus the switch is advantageously provided with a wiping relationship on the portions of the relatively movable contact members which carry current, whereby to minimize the adverse effects of corrosion and dirt in such areas.

Means are provided in accordance with the invention for preventing undue overrun of the upwardly bowed portion of the leaf strip, to prevent any possibility that such portion might be depressed too far downwardly and reverse its configuration. Such means may take the form of an anvil disposed beneath the leaf strip in the upwardly curved bowed portion.

For economy and ease of assembly of the present switch, one end of the leaf strip may be provided with a V notch by which to engage the cylindrical portion of a terminal post, constituting one of the seats between which the strip extends.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a switch in accordance with the present invention showing the oppositely bowed leaf spring in its normal position.

FIG. 2 is a sectional view taken on line II-lI of FIG. 1.

FIG. 3 is a fragmentary sectional view of the upper portion of the switch, taken on line IIIIII of FIG. 1.

FIG. 4 is a fragmentary vertical sectional view, similar to FIG. 1, but showing the parts in their position after the leaf spring has been actuated downwardly from its normal position.

FIG. 5 is a sectional view taken on the broken line V-V of FIG. 4.

FIG. 6 is a fragmentary sectional view of the terminal post or seat at the left side of the switch, showing the engagement with it of the V-shaped notch ofthe leaf strip.

FIGS. 7a, 7b, 7c and 7b show successive steps in the movement of the generally spherical contact member relative to the upper abutment and the lower abutment during actuation of the switch from its normal to its actuated positions, and particularly illustrating the wiping action occurring during such actuation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now in detail to the drawings, there is shown in FIG. 1 a sectional view of the present switch in its normal position, i.e., before it has been actuated to its second or actuated position. The switch includes a body of dielectric material, particularly including a base portion indicated generally at 10 and a cover indicated generally at 12 including downwardly depending sidewalls 14 and 15, by which the cover and base are retained in assembled relation as by heat sealing or other encapsulation method well known in the art. Extending between the walls 14, 15 is a top wall 16 and (see FIG. 2) depending downwardly from top wall 16 are front and

rear walls

17 and 18 respectively, joined to the base 10 in a manner similar to end walls 14, 15.

Within body 10 there are provided three electrical terminals, a common terminal indicated generally at 20, a normally open terminal indicated generally at 22, and a normally closed terminal indicated generally at 24. Each of these terminals is an elongated electrically conductive member imbedded in the base body 10, and each is adapted to be connected to external circuitry through conventional wires or other conductors, not shown. Projecting upwardly from common terminal 20 is a terminal head or connector indicated generally at 30, having formed therein a neck portion 32 of reduced cross section, bounded downwardly and upwardly by frusto

conical portions

33 and 34 respectively. Connec tor 30 is made of electrically conductive material, and is in electrical contact with the common terminal 20 and, as will be later understood, serves both as an electrical connection with the resilient leaf-strip of the present invention, and also as one of the seats between which the leaf strip is supported.

The conductive leaf strip just mentioned is indicated generally at 40, and is made of a resilient material of high conductivity such as copper or a copper alloy. One end of the leaf strip may be provided with a V-shaped notch 42 (see FIG. 6)'which receives and contactingly engages the portion 32 of reduced diameter of connector 30. Notch 42 is defined by

sidewalls

43 and 44, each of which is in electrical contact with reduced portion 32. The other end of leaf strip 40, indicated at 45, may be received in a horizontally extending recess 46 formed in a boss indicated generally at 48, the boss being desirably an integral portion of the base body 10, surrounding the upper portion of normally closed terminal 24. Thus the notch 46 formed in boss 48 serves as one seat for supporting leaf strip 40, while the opposite end of the leaf strip is seated upon connector 30as previously described. It will be noted that the two seats are spaced together more closely than the effective length of leaf strip 40, so that the strip is compressively stressed and, if otherwise unrestrained, would assume an arcuate or bowed configuration.

Approximately midway of the length of leaf spring 40 there is desirably provided a protuberance on either side of the leaf strip, constituting a contact member indicated generally at 50. This member may be made, for example, of coin silver and may be desirably additionally gold plated for enhancing its electric conductivity and minimizing the possibility of corrosion of the surface of member 50, particularly in adverse atmospheric conditions. In the position of the leaf strip 40 seen in FIG. 1, the contact member 50 is in electrically conductive contact, in its upper portion, with a conductive member indicated generally at 52, and projecting inwardly of the body from its connection at 53 with the upper portion of normally closed terminal 24. More specifically, the lower surface 54 of conductor 52 is abuttingly contactable against contact member 50, and the leaf strip 40 as a whole is thus deformed into a sinuous shape, including an upwardly bowed portion 56 and a downwardly bowed portion 58.

Actuating means are provided in accordance with the present invention for causing the leaf strip 40 to snap from its normal position seen in FIG. I to its actuated position seen in FIG. 4. It will be noted that such movement breaks the electrical connection between contact member 50 and normally closed terminal 24, and virtually simultaneously makes the electrical connection between contact member 50 and normally open terminal 22. In the present illustrative embodiment of the invention, such actuating means take the form of an actuating plunger indicated generally at 60 and provided with a downwardly directed tip 62 adapted to abuttingly contact the upper surface of the leaf strip 40, between the apex or zenith of the upwardly bowed portion 56 of that strip and the adjacent seat provided by the portion 32 of connector 30. Thus the major portion of leaf strip 40 is caused to move slightly rightwardly as seen in the drawings, with the upwardly bowed portion 56 being somewhat flattened, while the curvature of the downwardly bowed portion 58 is simultaneously increased. Comparison of FIGS. 1 and 4 will make clear the movement of the parts from one position to the other.

More specifically, and with reference to FIG. 4, actuating plunger 60 is moved downwardly as a result of force imposed upon upper tip 64 of the plunger by an external member indicated generally at 66. This latter member may, of course, be the finger of the operator, or may be a structural member of an external portion of the apparatus with which the present switch is used.

An important feature of the present switch is that it is self-restoring. This capability is provided by insuring that the upwardly bowed portion 56 of the leaf strip is not permitted to be flattened to the extent that it will snap through planar configuration and become downwardly bowed, with the formerly downwardly bowed portion 58 becoming simultaneously upwardly bowed. As will be readily understood from the drawings and the preceding description, this condition of the strip would be stable and the switch would accordingly be inoperative for its intended function.

Stop means are accordingly provided for limiting downward movement of the upwardly bowed portion of the strip, either directly by an abutment beneath that portion of the strip, or indirectly by limiting downward movement of the actuator. Such means may for example take the form of an upwardly protruding anvil 70, desirably formed integrally with body base 10 and disposed generally centrally of and beneath the upwardly bowed portion 56 of the strip, and by preference spaced slightly below the strip when the switch is in its actuated position, in order to permit a certain amount of overtravel of plunger 60 in its downward movement. Alternatively, or in addition to the stop means just described, stop means may be provided by the shape of the actuator itself and its relation to the base 10. Thus the lower portion of the actuating plunger, as best seen in FIG. 2, may include downwardly extending, laterally spaced sidewalls 67, 68, whose

lower edges

73, 74 are limited in their downward movement by abutment against

planar surfaces

75, 76 formed in base body 10.

An important and advantageous characteristic of the present switch is the fact that actuation of the leaf strip from its normal to its actuated position, and the reverse movement of the strip when force is removed from actuating plunger 60, accomplish a sliding or wiping action on the surfaces of the members which are making or breaking electrical contact. This is best illustrated in FIGS. 7a, 7b, 7c and 7d, showing successive positions of the parts making and breaking contact during the process of actuation.

Thus, FIG. 7a shows the position of the parts before any stress has been impressed upon upwardly bowed portion 56 of the leaf strip. In this situation, contact member is firmly in electrical contact with the lower surface 54 of member 52, as previously mentioned. In FIG. 7b, the parts are shown after actuating plunger has partially flattened upwardly bowed portion 56 of the strip, but before the stress has built up to enough to snap the switch. It will be noted, by comparison of FIG. 7a with FIG. 7b, that the actual point of contact of contact member 50, shown at A in FIG. 7a has moved to B in FIG. 7b.

With similar reference to FIGS. 7c and 7d, it will be seen that FIG. 7c represents the parts at the initial moment of contact between contact member 50 and the upper surface 23 of normally open terminal 22. The actual point of contact under these conditions is indicated at C. In FIG. 7d, representing the parts in their rest or fully actuated position, the actual point of contact between contact member 50 and surface 23 has moved rightwardly as seen in the drawing to point D.

As will be readily understood, the reverse of this sequence of events occurs when the leaf strip 40 is permitted to return to its normal position of FIG. 1, by reason of release of force depressing actuating plunger 60 downwardly.

In order to insure the wiping action of the contacting members just described, it is important that the point of application of the downward actuating force on the upwardly bowed portion 56 be disposed below the apex or zenith of that portion, toward the adjacent seat 32. If, for particular applications, the wiping action is not important, then the point of application of downward actuating force may be located at virtually any point along the upwardly bowed portion 56 of leaf strip 40. It will be observed that the application of actuating force to the upwardly bowed portion 56 essentially acts about seat 32 as a fulcrum. When the lever arm about that fulcrum is relatively short, then the longitudinal wiping action between contact member 50 and the

respective surfaces

54 and 23 will be comparatively great, When that lever arm about fulcrum 32 is comparatively long, then the longitudinal wiping action will be comparatively slight.

There is thus provided a self-restoring snap action switch having only two moving parts, the leaf strip and the actuator; and, by reason of its simplicity and ease of assembly, capable of being manufactured very economically. Because of the stresses always existing in the leaf strip 40, contact bounce upon the initial making of contact is minimized and virtually eliminated.

Modifications and changes from the specific illustrative embodiment hereinabove described and shown within the contemplation of the invention, and are intended to be embraced within the scope of the appended claims.

What is claimed is:

1. A self-restoring snap action switch comprising:

a housing body;

an elongated, resilient, conductive leaf strip; spaced seats mounted in the body for contactingly supporting strip end edges, said seats being spaced closer together than the effective length of the strip whereby to impose a bow thereon; an upper abutment member disposed generally midway between said seats and slightly above their plane and normally in abutment with the strip upper surface for imposing on the strip a downward bow in a first strip portion, a second strip portion being upwardly bowed; lower abutment member disposed generally midway between said seats and abuttable against the lower surface of the strip for limiting downward movement of the central portion of the strip, at least one of the abutment members and a seat being conductive, the conductive seat consisting of a terminal head having a neck of reduced section bounded upwardly and downwardly by portions of larger section, the strip end edge contacting the conductive seat including an outwardly open V- shaped notch extending axially of the strip for receiving the neck therein, and the seat opposite said conductive seat consisting of a horizontal recess formed in the body for receiving the end of the strip opposite the notched end;

actuator means for forcing downwardly the upwardly bowed portion;

and stop means limiting downward movement of the upwardly bowed portion in response to downward actuator movement.

2. The invention as defined in claim 1 including a common terminal electrically connected to the conductive seat. I

3. The invention as defined in claim 1 wherein the upper and lower abutment members are conductive.

4. The invention as defined in claim 3 including normally closed and normally open terminals connected to the upper and lower abutment members respectively.

Claims

1. A self-restoring snap action switch comprising: a housing body; an elongated, resilient, conductive leaf strip; spaced seats mounted in the body for contactingly supporting strip end edges, said seats being spaced closer together than the effective length of the strip whereby to impose a bow thereon; an upper abutment member disposed generally midway between said seats and slightly above their plane and normally in abutment with the strip upper surface for imposing on the strip a downward bow in a first strip portion, a second strip portion being upwardly bowed; a lower abutment member disposed generally midway between said seats and abuttable against the lower surface of the strip for limiting downward movement of the central portion of the strip, at least one of the abutment members and a seat being conductive, the conductive seat consisting of a terminal head having a neck of reduced section bounded upwardly and downwardly by portions of larger section, the strip end edge contacting the conductive seat including an outwardly open Vshaped notch extending axially of the strip for receiving the neck therein, and the seat opposite said conductive seat consisting of a horizontal recess formed in the body for receiving the end of the strip opposite the notched end; actuator means for forcing downwardly the upwardly bowed portion; and stop means limiting downward movement of the upwardly bowed portion in response to downward actuator movement.

2. The invention as defined in claim 1 including a common terminal electrically connected to the conductive seat.