US3518598A - Snap action electric switch - Google Patents

Description

June 30, 19470 H. JAKOBS 3,518,598

SNAP ACTION ELECTRIC SWITCH Filed March ll. 1968 20B l2 22B United States Patent O "ce 3,518,598 SNAP ACTION ELECTRIC SWITCH Hans Jakobs, Schaumburg Township, Cook County, Ill.,

assignor to C. E. Niehot & Co., Chicago, Ill., a corporation of Illinois Continuation-in-part of application Ser. No. 597,045,

Nov. 25, 1966. This application Mar. 11, 1968, Ser.

Int. Cl. H01h 61 06 U.S. Cl. 337-135 6 Claims ABSTRACT F THE DISCLOSURE A snap action electric switch comprising a llexible snap acting metallic contact carrying vane with vane biasing means and longitudinally expansible pull wire means overlying the opposite surfaces of the vane and tensioned to Hex the contact carrying portion of the vane in opp0- site directionsbetween two positions in response to alternate heating and cooling of the pull wire.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of applicants copending application Ser. No. 597,045, led Nov. 25, 1966, and assigned to the assignee of this application.

FIELD OF INVENTION The invention pertains to snap action electric switches operated by the alternate heating and cooling and the resultant expansion and contraction of an element generally called pull means or a pull wire. Most often the switches are used to control the flashing of automotive signal lights, such as turn signals.

DESCRIPTION OF THE PRIOR ART Snap action switches of the character set forth immediately above are well known and of various constructions. Many include a exible vane that is creased and thus biased into one position by inherent or intrinsic stresses in the vane. The device disclosed and claimed in the above referred to copending application utilizes a substantially flat unstressed ilexible vane with separate biasing means and pull wire so arranged that alternate heating and cooling of the pull wire results in snap action movement of the vane and a contact carried by it between two positions. Greater reliability of operation, life expectancy and simplicity of construction are desired.

SUMMARY Greater reliability of operation and life expectancy of the snap switches are obtained by constructing the vane with two sets of ribs or projections that extend in opposite directions from the plane of the Vane. One set of ribs projects in a rst direction toward and cooperates with the central region of the biasing means to limit movement of the vane toward the biasing means in the cold contracted condition of the pull wire, thereby to provide an angular relationship between the two better to insure return operation of the vane by the biasing means when the pull wire is heated and expanded. The second set of ribs extends in the opposite direction from the first toward the pull wire for cooperation with the end portions of the -pull wire to space the latter from the vane so that the pull wire (which is of the indirectly heated type, i.e., with a heater element carried by the pull wire) will not be engaged and undesirably bent by the vane when the vane moves toward the pull wire in the expanded condition of the pull wire. The arrange- 3,518,598 Patented June 30, 1970 ment contributes to the longevity of the pull wire and thus of the device.

Other objects and advantages of the present invention will become apparent from the ensuing description of an yillustrative embodiment thereof, in the course of which reference is had to the accompanying drawing, in which:

FIG. 1 is a perspective view of the snap action switch of the present invention, viewed from the pull wire side;

FIG. 2 is a perspective view of the device of FIG. l, viewed from the opposite or biasing means side;

FIG. 3 is a plan view of a movable vane utilized in thek device, the vane being shown prior to attachment of the associated biasing and pull wire means which are shown in FIGS. l and 2;

FIG. 4 is a sectional view of the vane taken along the line 4-4 of FIG. 3;

FIG. 4A is a fragmentary sectional view of the vane taken along line 4A-4A of FIG. 3;

FIGS. 5 and 6 are sectional views taken along the lines 5-5 and 6-6 of FIGS. 1 and 2 and illustrating the,y position of the vane with respect to the biasing and pull wire means, respectively, when the pull wire means is in its cold unexpanded or contracted position;

FIGS. 5A and 6A are views corresponding to FIGS 5 and 6, but illustrating the position of the vane with respect to ,the biasing and pull wire means, respectively, when the pull wire means is in its heated expanded condition;

FIG. 7 is a plan view of the pull wire means; and

i FIG. 8 is a cross sectional view along the line 8-8 of FIG. 7.

FIGS. 5 and 6 are dimensionally enlarged in order better to illustrate the construction and operation of the vane with relation to its associated biasing and pull wire means.

Referring now to the drawing, the snap action switch device of the present invention is generally designated by the reference character 10. In large measure the device is Alike the one illustrated and claimed in my earlier referred to copending application. It includes, in the main, a flexible and resilient metallic vane 12 of generally octagonal shape, biasing means 14 comprising a pair of straps 14A and 14B overlying one surface of and attached to opposite edges of the vane lat the ends of-the vane, and pull wire means 16 comprising a longitudinally expansible pull wire attached at its ends 16A and 16B to opposite ends of the vane and positioned substantially centrally of the straps 14A and 14B. The vane 12 is substantially at and inherently unstressed and provided with opposite extending transverse slots 12A and 12B as disclosed in my copending application.

As will be described in greater detail hereinafter, the biasing straps are tensioned and ex the vane in one direction away from the straps, as best illustrated in FIGS. 5A and 6A. The length of the pull wire is such that in its cold unexpanded or contracted position it is tensioned and flexes the vane in the opposite direction, i.e., toward the straps, see FIGS. 5 and 6. -The biasing straps and pull wire are effective in response to alternate heating and cooling and resultant expansion and contraction of the pull wire to move the vane between its alternate flexed positions. Movement of the vane is utilized to move one or more contacts mounted on the vane relative to a stationary contact or contacts associated therewith thereby to provide desired circuit controlling functions.

In accordance with the present invention, the vane is provided with rst and second sets of projecting ribs 20 and 22 extending transversely of the pull wire and biasing straps. The ribs cooperate with the pull wire and biasing straps to improve operation and extend the operating life of the device.

The first set of ribs 20, including the individual ribs 20A and 20B, are located substantially centrally of and extend across the vane transversely of the biasing straps and pull wire fairly closely adjacent and parallel to the slots 12A and 12B. They project toward and cooperate with the biasing straps which they engage when the pull wire is cold and contracted, as shown in FIG. 5, with respect to strap 14B, to limit the relative movement of the vane and straps toward each other. This limitation of movement results in a small angle between the halves of the straps at the sides of the ribs and the vanes to space them so as better to insure return of the vane by the biasing straps when the pull wire is heated and expands. This angular relation has been found to facilitate movement of the vane in response to alternate heating and cooling of the pull wire 16 and the resulting movement of the vane between the positions shown in FIGS. and 6 and in FIGS. 5A and 6A.

FIG. 5 illustrates the relative positions of the vane and biasing straps when the pull wire is heatedas well as illustrating the bias initially applied to the vane by the straps. This bias is such as to flex the vane away from the straps, the vane bending in a hingelike manner at a central area 12c between the slots 12a and 12b and the ribs 20a and 20b, thereby to produce considerable movement of the upper end of the vane as shown in FIGS. 1 and 2. The ribs also contribute rigidity to the vane at its central region, thus serving additionally to concentrate the alternate flexing or bending of the vane to the central region 12C.

The pull wire 16 is spaced from the vane 12 by the second set of ribs 22, which includes the two ribs 22A and 22B, located at opposite ends of the vane. These ribs also run transversely of the biasing straps and pull wire and project from the plane of the vane at the pull wire side. The ends of the vane beyond the ribs 22A and 22B have small triangular portions 12D that are bent slightly in the same direction as the projection of the ribs 20 to which the opposite ends 16A and 16B of the pull wire are secured. The ribs 22A and 22B project but slightly, but enough to prevent any substantial contact and undesired bending of the pull wire by the vane.

As illustrated and earlier indicated, the vane 12 is of octagonal shape. It is stamped with the previously referred to opposed slots 12A and 12B extending inwardly from opposite edges of the vane toward the center. The slots have a length about one-third the width of the vane, leaving the central flat vane area 12C between the ribs 20A and 20B and the slots. The ribs 20 are thus located at each side of the slots and disposed parallel to the slots and both the slots and ribs are disposed transversely of the biasing straps and pull wires. The ribs 20A and 20B may be of uniform height, although the central portions thereof which do not engage the tensioning straps 14 may be somewhat higher in order to provide additional stitfening of the vane, thereby better to insure the overcenter snap action of the vane between the positions illustrated in FIGS. 5 and 6.

As is the case with the vane of my copending application, the vane 12 can be formed by a stamping operation or operations in which the vane is initially cut into the slotted octagonal configuration. The ribs and outer triangular portions 12D can be formed on the vane at the same time. The ri-bs, however, do not disturb the substantially flat construction of the vane nory do they provide any inherent or intrinsic stresses in the vane which need to be relieved by heat treatment or otherwise. Y

The biasing straps 1-4 are attached to spaced alternate flats 12E of the vane and extend parallel to one another and overlie one surface of the vane. The straps comprise strips of material, ,preferably metallic, having a length somewhat longer than the distance between points 12E. The ends 14C of each biasing strap are spot welded in place at the region of the flats. The effective lengths of the biasing straps 14 are such as to flex the vane away from the biasing straps and transversely of the direction of the bias, to a position substantially as illustrated in FIGS. 5A and 6A. Thus, when the pull wire is hot and in its expanded condition the biasing straps effect snap movement of the vane to the position of FIGS. 5A and 6A. Adjustment of the magnitude of the bias can be conveniently and easily adjusted by bending the Hats 12E of the vane and such adjustment of the straps may be effected independently of each other, as well as independently of the pull wire.

In the cold condition of the pull Wire the central regions of the straps 14 are engaged by the ribs 20A and 20B with the result that the opposite halves of the straps and Vane are at a slight angle to each other, even though the vane is biased toward the straps by the pull wire. In the heated and expanded condition of the pull wire the vane is flexed away from the bias straps and the ribs may be spaced and generally at least one of the straps is spaced from the ribs. The aforementioned angular spacing between the straps and vane better insures movement of the vane from the position of FIGS. 5 and 6 to the position of FIGS. 5A and 6A.

The pull wire 16 overlies the other surface of the vane and is attached to and extends between opposed points 12D of the vane, which are provided with locating slots 12F receiving flat end portions of the pull wire. The pull wire comprises a strip of material, preferably metallic and heat expansible in a longitudinal direction, having a length slightly in excess between the points 12D. The pull wire is attached at its ends to the vane by means of crimping and welding and the ribs 22A and 22B space the pull wire slightly from the adjacent surface of the vane 12. In the heated condition of the pull Wire the latter approaches the surface of the vane somewhat but has no substantial engagement with it, so that, as earlier noted, there is no substantial engagement or undesired bending of the pull wire by the vane and the pull wire remains substantially straight over its length.

The vane 12 moves with snap action between two positions. In what may be termed a first position in which the pull wire 16 is cold but ready to be heated, a contact 30 at the upper or outer and substantially free end and biasing strap side of the vane is spaced from an associated xed contact 32 mounted upon a conductive bracket 34 of suitable shape. The opposite end portion of the vane is fixedly secured to a bracket type support 36, the mounting being effected by longitudinally spaced spot welds 38 at an ott center portion of the vane, to an intermediate portion 316A of the bracket. The bracket is provided with a somewhat transversely extending end portion '36B which extends toward the vane and against which the vane may abut in the aforesaid normal position. It should be noted that in the illustrated arrangement the contact 30` is also at the bias wire side of the vane.

Referring particularly to FIGS. 1 and 2, it may be noted that the device 10 includes a base 40 preferably formed of non-conductive material, such as molded plastic. The device generally includes a cover (not shown) engageable with the base and associated element. Extending downwardly from the base are a plurality of plug-in type terminal members, of which two, indicated by the reference characters 42 and 44, are illustrated. These terminals are connected to the supports 34 and 36, respectively, by conductive rivets 46.

Alternate heating and cooling of the pull wire 16 to effect alternate expansion and contraction of the pull wire may be accomplished in any desired manner. In the illustrated device the pull wire 16 is heated indirectly by means of a resistance heating wire or element 48` disposed within and in intimate heat transfer relation with a substantial length of the pull wire 16'.

In accordance with a feature of the invention, the pull wire is provided with a tubular central portion 16C formed as a circular tube, as best illustrated in FIGS. 7 and 8. The heating element 48 of insulated resistance wire is formed in -what might be considered a hairpin shape and inserted into the tubular portion whereby the closed end or bight portion of the wire is disposed within the tubular portion. The heating element may take other shapes or be of a straight through type mounted within the tubular portion. The result is a readily made indirectly heated pull wire in which the heating element is protected by and in intimate heat transfer relationship with an enclosing portion of the pull wire.

The projecting ends 48A of the heating wire extend and are electrically connected t the terminals 42 and 44 as by iiexible conductors 48B. The circuit arrangement is such that the heating element is energized in the indicated position of the vane in which contacts 30 and 32 are disengaged, assuming that a source of electricity is connected to the terminals. When the pull wire expands and the vane moves to its other position to effect engagement of contacts 30l and 32 the heating element is short circuited. Signal lights may be in circuit with one of the terminals so that when the heating element is short circuited (and thus cooling) the lights are energized suiciently to be lighted; when the heating element is not short circuited (and being heated) and in series with the lamps, the lamps are not lighted.

In operation, the vane 12 is normally in the condition illustrated in FIGS. 1 and 2 wherein the pull wire 16 is in its contracted or unexpanded condition. In this condition the vane is exed by the pull wire in the direction toward the biasing straps 14 to a position in which the contacts 30 and 32 are out of engagement and the heating element is connected in non-shorted manner across the terminals 42 and 44. At this time the associated signal lights are not lighted. This condition and position of the vane is also shown in FIGS. 5 and 6.

After the pull wire 16 is heated for a period of time, it expands so that the vane 12 is snapped by the biasing straps 14 to its alternate position, as shown in FIGS. 5A and 6A. This movement causes the outer end of the vane abruptly to move with snap action, to effect engagement of contacts '30 and 32 and short crcuiting of the heating element 48. As a result, the pull wire 16 begins to cool, and after a period of time contraction of the pull wire 16 snaps the vane to its original position. 'Ihe foregoing operations are continued resulting in alternating operation of the vane and signal lamps until such time as a circuit controlling switch is opened.

While the present invention has been described in connection with the details of particular illustrated embodiments thereof, it should be understood that the present invention is not limited to these details, except insofar as set forth in the accompanying claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. Apparatus yof the type described comprising a substantially flat and unstressed resilient vane, means supporting the vane, exible vane biasing strap means and heat expansible pull wire means attached to the vane at opposite sides of the latter for effecting snap action of the vane between two positions in response to alternate heating and cooling of the pull wire means, and the improvement comprising a pair of ribs located near the center of the vane and extending transversely of the vane and the biasing strap means, said ribs projecting away from the vane toward and engaging the biasing strap means at spaced regions centrally of the` latter in one position of the vane to space biasing strap means from the vane.

2. Apparatus as claimed in claim 1, additionally comprising spaced ribs on the vane near the points of attachment of the pull wire means to the vane, the ribs projecting away from the vane toward and engaging the pull 'wire near its ends to space the latter from the vane.

3. In apparatus of the type described in claim 2, wherein the vane is a substantially fiat unstressed metallic vane, the vane biasing means comprises a pair of spaced apart generally parallel straps at one side of the vane and each attached to opposite ends of the vane to flex the vane in one direction transversely of and away from the biasing means, the expansible pull means has its ends attached to the opposite ends of the vane between and generally parallel to the biasing straps, said vane has slots extending transversely of the direction of the straps from the edges toward the center of the vane, said slots being located substantially mid-way between said opposite ends of the vane, a conductive mount for the vane, a contact mounted on a free `end of the vane and movable therewith, a stationary contact engageable by the movable contact in one of its positions, a supporting base, a conductive mount for the stationary contact, said mounts being supported on the base, and terminals on said base connected respectively to said mounts, and wherein the rib means comprises spaced ribs extending transversely of the vane near the sides of the slots and parallel thereto and projecting a short distance toward the biasing straps, the vane mount being attached to the vane between one of the latter ribs and the adjacent end of the vane at a region between the pull means and one of the biasing straps, said pull means having a length such that in its unexpanded and contracted condition it ilexes the vane in a direction toward the biasing straps so that the latter engage the ribs to provide a limit angular relation between the vane and the straps.

4. In apparatus 'as claimed in claim 3, wherein the pull means has a tubular portion between its points of attachment to the vane and a reversely bent insulated resistance type heater wire has its closed end portion within said tubular portion.

5. In apparatus as claimed in claim 4, wherein the pull means has fiat end portions and the vane has slots at its ends for receiving and locating the iiat end portions.

l6. Apparatus of the type described including a snap acting resilient vane movable between two positions, means supporting the vane, and heat expansible pull wire means attached at its ends to the vane for effecting snap action of the vane between its two positions in response to alternate heating and cooling of the pull wire means, said pull wire means including a strip of material having a central tubular portion of substantially closed circular cross section between its points of attachment to the vane, said strip having substantially flat single-thickness portions adjacent its ends for attachment tothe vane, and an insulated resistance type heater wire mounted within said tubular portion.

References Cited UNITED STATES PATENTS 2,166,238 7/1939 Davis 337-391 2,299,767 10/ 1942 Schmidinger 337-140 2,706,228 4/1955 Welsh 337-139 2,878,340 3/1959 Uhl 337-141 3,174,013 3/1965 Suberg 337-135 2,738,414 4/ 1957 Cromwell et al. 337-139 3,218,415 1l/1965 Voorman 337-136 BERNARD A. GILH-EANY, Primary Examiner DEWITT M. MORGAN, Assistant Examiner U.'S. C1. X.R. 337-138, 139

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