US3090851A

US3090851A - Flasher switch

Info

Publication number: US3090851A
Application number: US825681A
Authority: US
Inventors: Strauss Leopold; Harold L Loew
Original assignee: Ideal Corp
Current assignee: Parker Hannifin Corp
Priority date: 1959-07-08
Filing date: 1959-07-08
Publication date: 1963-05-21
Anticipated expiration: 1980-05-21

Description

May 1963 L. STRAUSS ETAL 3,090,851

FLASHER SWITCH Filed July 8, 1959 INVENTORS LEOPOLD STRAUSS HAROLD L. LOEW ATTO/iWEYS:

United States atent 3,090,851 FLASHER SWITCH Leopold Strauss, East Rockaway, and Haroid L. Loew, Jackson Heights, N .Y., assignors to Ideal Corporation, Brooklyn, N .Y., a corporation of New York Filed July 8, 1959, Ser. No. 825,631 11 Claims. (Cl. 200-113) This invention relates to new and improved switch devices and more particularly to devices especially suitable for use, for example, as a flasher switch in directional signal systems of motor vehicles.

One of the objects of the invention is to provide a self-operating switch device that is actuated by expansion of one part of a switching member relative to another and which oeprates reliably under widely difierent ambient temperature conditions, so that the device will function properly under diverse climatic conditions without need for adjustment to a particular climate.

Another object of the invention is to provide a new and improved switch device of quite simple and economical construction, which functions with a snap action to open and close an electrical circuit or the like periodically, and which is eminently suitable for use as a flasher switch.

A further object is to provide an electro-therrnally actn ated flasher switch that can be readily set or biased to work with the desired contact pressure against an electrical contact element and to cause repeated movements of a switching member between spaced contact elements at any of a variety of frequencies and velocities, so as to produce desired flashing signals and desired clicking sounds at desired intervals in the operation of the device.

According to one feature of the present invention, a switch device is provided with a switching member comprising a resilient tension portion and a counteracting resilient compression portion that is held continuously in an elastically bowed condition by the pull or tension of the tension portion, and the tension and compression portions are made to have substantially the same coefficient of thermal expansion, such as by composing them of identical electrical resistance material, and are so coordinated that a switching movement of a part of the switching member positioned by the bowing of the compression portion will be induced by a change of the temperature and a resulting change of dimensions of one of said portions relative to the other.

According to another feature of the invention, the tension and compression portions are formed as unitary parts of a single piece of an electrical resistance material having a high coefiicient of thermal expansion, for example, by pressing or stamping the entire switching member out of a thin strip of an electrical resistance alloy such as a nickel-chromium resistance alloy or the like.

A particularly advantageous switch device is provided according to this invention by forming an elongated switching member to comprise a tension or strand portion composed of one or more strips joined at one end to one end of a tongue portion of resilient material, the joined ends of those portions constituting a movable free end of the switching member, and anchoring the re spective other ends of those portions in relatively fixed positions with the tension portion under tension and the tongue portion under compression between the respective fixed ends and the free end. The fixed end of the tongue portion is cantilevered on its anchoring means, and by the tension of the tension portion the cantilevered tongue portion is held elastically in a bent or bowed con dition in which it continuously exerts an unbending moment tending to position the free end of the switching member. Thus the free end is normally biased to a definite switching position from which it is movable to another position in response to a change of the degree of bowing of the tongue. Such a change, which greatly alters the effective unbending moment, is produced by changing the relative positions of the tension and tongue portions. Their relative positions may be changed by changing their relative lengths, such as by the electrothermal action of an electric current passed through the tension portion when it is composed of an electrical resistance material as mention above.

The switching member is made to operate with a periodic snap action, so as to open and close a circuit automatically with a desired frequency and velocity of action, by arranging the tension portion on a line or plane of tension extending to one side of the cantilevered end of the tongue portion and bowing the tongue portion elastically into a reversely elastically curved formation crossing the line of tension, with a first part of the formation curving in one direction only to that line from the cantilevered end, so that this first part continuousiy exerts a moment in unbending direction, i.e., away from the line of tension, and with another part of the tongue portion curving oppositely into and joined with the free end of the switching member from the opposite side of that line. A kind of a toggle action is brought about in this way, in that an imaginary point of zero bending moment is created in an intermediate part of the doubly curved tongue portion, which point lies at one side of the line of tension when the tension portion is in its normal or cold condition and is shifted to the other side of the line of tension to produce a snapping movement of the free end when the tension portion is in an elongated or hot" condition.

Other objects, features and advantages of this invention will be apparent from the following detailed description of a preferred embodiment thereof and from the accompanying illustrative drawing in which:

FIG. 1 is a side elevation, partly in section, of a flasher switch embodying the invention;

FIG. 2 is a front elevation taken from line 2-2 of FIG. 1, the protective housing being shown in section;

FIG. 3 is a plan view taken from line 33 of FIG. I, the housing again being in section;

FIG. 4 is an enlarged plan view of the switching memher used in the device of FIGS. 1 to 3; and

FIG. 5 is an enlarged diagrammatic view of the working elements of the device.

As illustrated in the drawing, a switch device embodying the several new features and advantages of the in vention is provided in a form especially suited for use as a flasher switch in the directional signal system of an automobile or the like. The illustrated form is a two-terminal switch device adapted for a relatively simple directional signal circuit. The working elements of the structure shown may also be used so as to function in the way here set forth in any of many other switch assemblies, including assemblies provided with three electrical terminals with or without a built-in relay of a type commonly used in flasher devices to make or break a circuit to the third terminal.

The functions of the illustrated device are centered in a switching member 10. As seen in FIG. 4, this member is a unitary elongated piece of a thin resilient strip material composed of an electrical resistance alloy having a high coefiicient of thermal expansion, preferably one of at least 7 microinches per inch per F. of temperature change. Any of a variety of well known resistance alloys is suitable for the strip material; for example, various nickel-chromium alloys such as those identified as Nichrome" and certain stainless steels such as austenitic 3 stainless steels of the types designated by AISI numbers in the 300 series.

The switching member is formed with a strand or tension portion composed of

parallel side strips

11 and 12, and with a central tongue or compression portion 14 which is spaced between the side strips and has one of its ends joined or integral with the strips at one end of the latter to constitute a free end of the switching memher as seen at 15. The

strips

11 and 12 are joined together at their other end by a base portion 16 of the piece of strip material, which portion is spaced from the inner end 17 of tongue 14 by a cut-away area 18 that separates the central tongue from other portions of the switching member except at the free end 15.

Member 10 may be formed in a single operation by pressing or stamping it as a unit from a thin strip of the desired resistance material. Since its

tension portion

11, 12 and its tongue or compression portion 14 are composed of identical material, they have the same coefficient of thermal expansion and do not vary substantially in their relative dimensions as a result of exposure to widely different atmospheric temperature conditions.

A working assembly of the switching member 10 is shown in FIGS. 1 to 3 of the drawing and indicated by the enlarged diagram of FIG. 5.

The various parts of the switch device are mounted on a conventional circular base 20 composed of an electrical insulating material such as a molded synthetic resin. The working parts are normally enclosed within a protective housing 21 fitted over the base 20.

Base 20 is formed with an upwardly projecting insulating post 22. The flat top of this post forms a ledge on which is seated and clamped firmly the fiat inner end 17 of the tongue 14 of member 10. The tongue is thus cantilevered to the top of the post. In the assembly of FIG. 1, flat feet 23 and 27 of

brackets

24 and 28, respectively, are placed over the end of the tongue, and a rivet 31 extending vertically through the post and the superposed parts is formed with a head which holds tongue end 17 and the feet 23 and 27 fixed immovab-ly to the top of the post.

The body of tongue 14 thus extends freely away from its cantilevered end to the front of the device. The

strips

11 and 12 flank the post and extend to a fixed location in back of it, where they are anchored by the base portion 16 which rests on a flat ledge 34 and is engaged at its inner side by a tensioning detent 40 fitting in a notch or recess 16a of the strip material. Thus the backward end of the tension portion is anchored at a location spaced somewhat above the cantilevered tongue end 17, and a tension imposed upon the

strips

11 and 12 between the free end 15 and their fixed end will compress the tongue and bend it elastically relative to the cantilever.

The ledge 34 for base portion 16 is formed as the top of a rigid, electrically conductive bar 35 which extends vertically through the insulating base 20- in a fixed position and forms below base 20 a terminal 36 for connection in an electrical circuit.

The tensioning detent 40 is made adjustable so as to place the tension portion of the switching member under any desired degree of tension. For this purpose, detent 40 is integral with a movable bracket 41 which is disposed across the back of conductor bar 35 and has opposite ends 42 extending forwardly to engage loosely over side lugs 37 formed on opposite sides of the bar 35; and a screw 44 is threaded through a bore 43 in bracket 41 to hear at its inner end against a socket portion 38 of the fixed bar 35. Advancement of the screw 44 forces bracket 41 and detent 40 backwardly relative to the fixed bar 35 and the cantilevered tongue, thus increasing the tension of the

strips

11 and 12, while retraction of the screw 44 reduces the tension.

At the front of the assembly, an electrical contact element is located in a fixed position below the free end 15 of member 10, where it normally will be engaged by the free end 15 with a pressure sufiicient to assure a good electrical contact. To enhance the contact efiiciency, a coacting electrical contact element 51 is fixed to the under side of the free end 15. Contact 50 is fixed to the forward end of a resilient tongue 49 which is mounted at its backward end on a conductor bracket 46. Bracket 46 extends across a forward part of base 20 in front of post 22 and has a leg 47 fixed in and extending below the base 20 to form a terminal 48.

When the two

terminals

36 and 48 are connected to opposite sides of an electrical circuit and the switching member 10 is in its normal position with

contacts

50 and 51 in engagement, a flow of electrical current takes place through the

strips

11 and 12 of member 10. This flow heats the strips and elongates them without changing the dimensions of the electrically insulated tongue 14.

Upon reference to FIG. 5, it will be evident that when the switching member 10 is assembled with its tension portion under suitable tension and its tongue elastically bent from the cantilevered end toward the tension portion by the resulting compression, the tongue exerts an unbending moment in a direction tending to move the free end 15 against contact element 50. The tension on the strips, which is a relatively fixed force, may be represented by the vector F. The unbending moment may be represented by the vector M. The magnitude of the unbending moment M is largely governed by the magnitude of the tension force F, but it will be evident that although an elongation of the

strips

11 and 12 relative to the tongue 14, such as effected by an electrical heating of the strips, does not materially change the tension force F, an elongation of the strips will be accompanied by a relatively great reduction of the curvature and the unbending moment of the tongue. The relatively great diflerence between the curvatures and bending moments of the cantilevered tongue when the strips are cold and when they are hot is utilized to cause a change of the position of the free end 15 of member 10, and thus to effect a switching action. Moreover, when the switching action causes the strips to be no longer heated electrically, the strips quickly resume their normal length which will restore the normal curvature of the tongue and thus cause the free end 15 to be returned to its normal position.

As seen in FIG. 5, the tongue 14 when placed under compression displacing it toward the

strips

11 and 12 assumes elastically a reversely or doubly curved formation which crosses the line of tension with one part 14a of the tongue curved toward the strip from the cantilevered end and another part 14b of the tongue curved oppositely into the free end 15 from the other side of the strip. This reverse or double curvature crossing the line of tension causes an imaginary point P of Zero bending moment to exist in the tongue between its oppositely curved parts 14a and 14b.

The tension of the tension portion and the consequent bowing of the tongue are selected so that in the normal or cold condition of the switching member the point of zero bending moment lies at the upper side of the line of tension. The tension force F thus urges the free end 15 in a downward direction, so that its contact element 51 normally bears against fixed contact element 50 with a pressure that can be set at any desired value by appropriate location of element 50 and appropriate selection of the tension force.

On the other hand, when the

tension portion

11, 12 is expanded thermally, as by a flow of electrical current through it between the

terminals

36 and 48, the curvature and bending moment of the tongue are so reduced relative to the force F that the point of zero bending moment is shifted to the lower side of the line of tension.

The tension force then snaps the free end 15 away from contact element 50, by a kind of toggle action. The upward movement of the free end is limited by a fixed stop or contact element 25 which is formed at the forward end of bracket 24 and is located to permit the desired range of movement of the free end of the switching member.

The movement of end 15 away from contact 50 stops the heating of the tension portion by breaking the current flow through the device. The tension portion then cools and shrinks quickly, and the attendant increase of curvature and bending moment in the tongue causes the zero moment point to return above the line of tension and the free end 15 to be snapped back into engagement with contact element 50. The tension portion then becomes hot again, and the switching action is repeated.

For as long as a supply of current is continued at the terminals of the device, the switching action continues to be repeated at short intervals.

For given settings of the contact or stop

elements

50 and 25 and of the tension and bowing of the tension and tongue portions of member 10, the pressure of the free end 15 against element 50 and the sensitivity and speed of the switching action may be controlled and varied by the setting of a screw 29 which is threaded in fixed brack et 28 and extends freely through an opening 26 in bracket 24 to bear against an intermediate part of the bowed tongue 14. An advancement of the screw 29 to lower its point of engagement with the tongue increases the pressure of the free end 15 against element 50. It also displaces the zero moment point of the tongue 14 nearer to the line of tension of the

strips

11 and 12, so that the switching member may act more quickly in response to a flow of electric current through the strips.

While we have described and shown details of an illlustrative embodiment of this invention, it is to be understood that the new features of the invention can be utilized in many other ways and are not restricted to the illustrated embodiment except as required by a fair construction of the appended claims.

We claim:

1. In a switch device, a switching member comprising a tension portion and a tongue portion of resilient material, said portions being united at one end thereof to constitute a movable free end of said member, means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end, the fixed end of said tongue portion being cantilevered on its anchoring means, the tongue portion being held bent elastically between its ends into a reversely elastically curved formation which crosses the line of tension of said tension portion with a first part of said formation curved elastically in one direction only from said cantilevered end to said line of tension, so that said first part continuously exerts a moment urging said free end in the direction opposite to the direction of its bend, and with another part of said formation curved oppositely into and joined with said free end from the other side of said line; said portions normally coacting to bias said free end to one switching position, and being responsive to a change of their relative positions to switch said free end to another position.

2. In a switch device, a switching member comprising a tension portion and a tongue portion, said portions being formed of the same resilient material and united at one end thereof to constitute a movable free end of said member, said material comprising an alloy having a. high coefficient of thermal expansion, means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end, the fixed end of said tongue portion being cantilevered on its anchoring means, said tongue portion being held bent elastically between its ends into a reversely elastically curved formation which crosses the line of tension of said tension portion with a first part of said formation curved elastically in one direction only from said cantilevered end to said line of tension, so that said first part continuously exerts a moment urging said free end in the direction opposite to the direction of its bend, and with another part of said formation curved oppositely into and joined with said free end from the other side of said line; a relatively fixed contact element in the path of said free end; said portions normally coacting to bias said free end against said contact element, and being responsive to a lengthening of said tension portion by a heating thereof to move said free end away from said contact element.

3. In a switch device, a switching member comprising a tension portion and a tongue portion of resilient strip material, said portions being united at one end thereof to constitute a movable free end of said member; means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end; the fixed end of said tongue portion being cantilevered on its anchoring means; the line of tension of said tension portion extending to one side of said cantilevered end in spaced relation thereto; said tongue portion being bowed elastically between its ends into a reversely elastically curved formation crossing said line of tension with a first part of said formation curved elastically in one direction only to said line from said cantilevered end, so that said first part continuously exerts a moment urging said free end in the direction opposite to said one direction, and with another part of said formation curved oppositely into said free end from the other side of said line; said portions normally coacting to bias said free end to one position, and being relatively movable to snap said free end to another position.

4. In a switch device, a switching member comprising a tension portion and a tongue portion of resilient strip material, said portions being united at one end thereof to constitute a movable free end of said member; means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end; the line of tension of said tension portion extending to one side of the fixed end of said tongue portion; said tongue portion being bowed between its ends into a reversely elastically curved formation crossing said line of tension with a part of said formation curved toward said line from said fixed end and another part thereof curved oppositely into said free end from the other side of said line; said portions normally coaeting to bias said free end to one position, and being relatively movable to snap said free end to another position; and a pressure element bearing from said other side of said line against a part of said bowed tongue portion between the aforesaid parts of said curved formation, to control the action of said member.

5. In a switch device, a switching member comprising a tension portion of electrical resistance material having a high coefficient of thermal expansion and a tongue portion of resilient strip material, said portions being united at one end thereof to constitute a movable free end of said member; means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end; the fixed end of said tongue portion being cantilevered on its anchoring means; the line of tension of said tension portion extending to one side of said cantilevered end; said tongue portion being bowed between its ends into a reversely elastically curved formation crossing said line of tension with a part of said formation curved toward said line from said cantilevered end and another part thereof curved oppositely into said free end from the other side of said line; a fixed pressure element bearing from said other side of said line against a part of said bowed tongue portion between the aforesaid parts of said curved formation; relatively fixed contact elements limiting the path of movement of said free end; said portions and said pressure element normally coacting to bias said free end against one of said contact elements, and being responsive to the closing of an electrical circuit through said tension portion to switch said free end periodically to and fro between said contact elements.

6. In a switch device, a switching member comprising a tension portion of material having a high coefiicient of thermal expansion and a tongue portion of resilient strip material, said portions being united at one end thereof to constitute a movable free end of said member; means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end; the

fixed end of said tongue portion being cantilevered on its anchoring means; the line of tension of said tension portion extending to one side of said cantilevered end in spaced relation thereto; said tongue portion being bowed elastically between its ends into a reversely elastically curved formation crossing said line of tension with a first part of said formation curved elastically in one directions to said line from said cantilevered end, so that said first part continuously exerts a moment urging said free end in the direction opposite to said one direction, and with another part of said formation curved oppositely into said free end from the other side of said line; relatively fixed contact elements limiting the path of movement of said free end; said portions normally coacting to bias said free end against one of said contact elements, and being responsive to thermal expansion of said tension portion relative to said tongue portion to snap said free end away from said one contact element into engagement with the other of said contact elements.

7. In a switch device, a switching member comprising a unitary elongated piece of a thin resilient strip material composed of an alloy having a high coefficient of thermal expansion, said piece having portions of its body cut away along its opposite sides and across one of its ends to leave integrated at its other end substantially parallel side strips and a central tongue extending from said other end between said side strip; relatively fixed means separately anchoring said strips and said tongue at said one end of said piece and holding said other end thereof free for movement in a path transverse to the plane of said other end, said strips being anchored in spaced relation to the anchored end of said tongue to one side thereof, said tongue being cantilevered on its anchoring means; said anchoring means holding said strips under tension and said tongue under compression, said tongue being bowed elastically between its ends into a reversely elastically curved formation crossing the plane of tension of said strips with a first part of said formation curved elastically in one direction only from said cantilevered end to said plane, so that said first part continuously exerts a moment urging said free end in the direction opposite to said one direction, and with another part of said formation curved oppositely into said free end from the other side of said plane; relatively fixed contact elements spaced apart at opposite sides of said free end; said strips and said tongue normally coacting to bias said free end against one of said contact elements lying at the same side of said strips as said cantilevered end, and being responsive to a lengthening of said strips by a heating thereof to switch said free end away from said one contact element into engagement with the other of said contact elements.

8. A switch device as claimed in claim 7, and a relatively fixed pressure element bearing from said other side of said plane against a part of said bowed tongue between the aforesaid parts of said curved formation, so as to regulate the pressure of said free end against said one contact element and the speed of the switching action.

9. A switch device as claimed in claim 7, said strips being interconnected at said one end by a base portion of said piece; said anchoring means for said tongue comprising an electrically insulating post; said anchoring means for said strips comprising an electrically conductive detent projecting between said strips beyond the end of said tongue and pivotally engaged by said base portion to tension said strips; and conductors electrically connected respectively with said detent and with said one contact element to pass current therebetween through said strips.

10. In a switch device as claimed in claim 7, said strips being interconnected at said one end by a base portion of said piece; said anchoring means for said tongue comprising an electrically insulating post; said anchoring means for said strips comprising an electrically conductive member engaging and positioning said base portion beyond and on one side of the end of said tongue so as to tension said strips and thereby hold said tongue in said elastically curved formation; and conductors electrically connected respectively with said member and with said one contact element to pass current therebetween through said strips.

11. In a switch device, a switching member comprising a tension portion of electrical resistance material having a high cocificient of thermal expansion and a tongue portion of resilient strip material, said portions being united at one end thereof to constitute a movable free end of said member; means anchoring the respective other ends of said portions in relatively fixed positions with said tension portion under tension and said tongue portion under compression between the respective fixed ends and said free end; the fixed end of said tongue portion being cantilevered on its anchoring means; the line of tension of said tension portion extending to one side of said cantilevered end in spaced relation thereto; said tongue portion being bowed elastically between its ends into a reversely elastically curved formation crossing said line of tension with a. first part of said formation curved elastically in one direction only to said line from said cantilevered end, so that said first part continuously exerts a moment urging said free end in the direction opposite to said one direction, and with another part of said formation curved oppositely into said free end from the other side of said line; reiatively fixed contact elements limiting the path of movement of said free end; said portions normally coacting to bias said free end against one of said contact elements, and being responsive to the closing of an electrical circuit through said tension portion to switch said free end periodically to and fro between said contact elements.

References Cited in the file of this patent UNITED STATES PATENTS 970,169 Birsfield Sept. 13, 1910 1,668,974 Mottlau May 8, 1928 2,225,086 Schramm Dec. 17, 1940 2,528,756 Kaser Nov. 7, 1950 2,568,476 Wierich et a1. Sept. 18, 1951 2,597,759 Starkey May 20, 1952 2,709,732 Davis May 31, 1955 2,761,931 Schmidinger Sept. 4, 1956 2,782,291 Cayet Feb. 19, 1957 2,879,355 Welsh Mar. 24, 1959 FOREIGN PATENTS 783,885 Great Britain Oct. 2, 1957

Claims

1. IN A SWITCH DEVICE, A SWITCHING MEMBER COMPRISING A TENSION PORTION AND A TONGUE PORTION OF RESILIENT MATERIAL, SAID PORTION BEING UNITED AT ONE END THEREOF TO CONSTITUTE A MOVABLE FREE END OF SAID MEMBER, MEANS ANCHORING THE RESPECTIVE OTHER ENDS OF SAID MEMBER, MEANS RELATIVELY FIXED POSITIONS WITH SAID TENSION PORTION UNDER TENSION AND SAID TONGUE PORTION UNDER COMPRESSION BETWEEN THE RESPECTIVE FIXED ENDS AND SAID FREE END, THE FIXED END OF SAID TONGUE PORTION BEING CANTILEVERED ON ITS ANCHORING MEANS, THE TONGUE PORTION BEING HELD BENT ELASTICALLY BETWEEN ITS ENDS INTO A REVERSELY ELASTICALLY CURVED FORMATION WHICH CROSSES THE LINE OF TENSION OF SAID TENSION PORTION WITH A FIRST PART OF SAID FORMATION CURVED ELASTICALLY IN ONE DIRECTION ONLY FROM SAID CANTILEVERED END TO SAID LINE OF TENSION, SO THAT SAID FIRST PART CONTINUOUSLY EXERTS A MOMENT URGING SAID FREE END IN THE DIRECTION OPPOSITE TO THE DIRECTION OF ITS BEND, AND WITH ANOTHER PART OF SAID FORMATION CURVED OPPOSITELY INTO AND JOINED WITH SAID FREE END FROM THE OTHER SIDE OF SAID LINE; SAID PORTIONS NORMALLY COACTING TO BIAS SAID FREE END TO ONE SWITCHING POSITION, AND BEING RESPONSIVE TO A CHANGE OF THEIR RELATIVE POSITIONS TO SWITCH SAID FREE END TO ANOTHER POSITION.