US3218415A - Thermally actuated snap action device - Google Patents

Description

' Nov. 16, 1965 H. VOORMAN, JR 3,218,415

THERMALLY ACTUATED SNAP ACTION DEVICE Filed March 7, 1963 ATTORNEYS United States Patent 3,218,415 THERMALLY ACTUATED SNAP ACTION DEVICE Henry Voorman, In, Midland Park, N.J., assignor to Tung-Sol Electric Inc., a corporation of Delaware Filed Mar. 7, 1963, Ser. No. 264,479 6 Claims. (Cl. 200-122) This application is a continuation-in-part of application Serial No. 77,155, filed December 20, 1960, now abandoned.

The present invention relates to snap action devices of the general type of that of Schmidinger Patent No. 2,615,106 dated October 21, 1952 and reissue thereof No. 24,023, dated June 14, 1955 and comprises an improved flasher which is readily stabilized for current and voltage fluctuations, lends itself to mass production in that adjustments are not too critical, requires few parts and has improved resistance to shock and vibration.

As in the patented device, which has had wide commercial use for control of automobile turn signals, the new flasher comprises a vane of resilient conductive material having an inherent deformation therein and an expansible pull ribbon or wire secured at its ends under tension to spaced points on the periphery of the vane, the pull ribbon when expanded as a result of current therethrough permitting the vane to snap toward the configuration into which it is constrained by the inherent deformation. In the patented flasher the pull ribbon is disposed generally parallel to the axis about which the vane is deformed, and its length relative to the vane dimensions is such that when fully expanded no extended length thereof contacts the vane surface. In the flasher of the present invention the pull means is disposed at an angle to the deformation and when expanded a substantial length of the pull ribbon engages the surface of the vane and is rapidly cooled thereby. Rapid cooling permits operation at lower temperatures where the cooling rate is ordinarily too low for efficient operation. Operation at lower temperatures minimizes variations in ratio and rate of flashing with change in supply voltage as will be apparent as the description proceeds.

Briefly, the new flasher comprises a vane of resilient conducting material given an inherent curvature about one axis, as by creasing, and a tensioned pull ribbon extending diagonally across the vane on the convex side of the inherent curvature thereof. A fixed contact is disposed in a position to be engaged under pressure, when the pull strip is cold, by a contact mounted at the center of the pull strip. The vane is supported at a location adjacent an edge thereof. Preferably the support means extends beyond the location of attachment to the vane and is shaped to engage the vane when it snaps to contact open position and thereby enhance noise.

For a better understanding of the invention and of various embodiments thereof reference may be had to the accompanying drawings of which:

FIG. 1 is a front view with the cover in section of a flasher embodying the invention;

FIG. 2 is a view of the device of FIG. 1 taken at right angles thereto;

FIG. 3 is a view similar to FIG. 2 but showing the position of the parts when the pull ribon is expanded;

FIG. 4 is a top plan view of the new flasher in the condition of FIG. 3;

FIGS. 5 and 6 are views of alternative constructions of vane suitable for use in the flasher of the invention;

FIG. 7 is a graph explanatory of the operation and of the advantages of the new flasher.

As shown in the drawings the flasher comprises an insulating base 2 which may be of any suitable molded plastic material having terminals 4 and 6 extending thereice through. Terminal 4, above the base 2, extends upwardly to provide the support 8 for the snap vane 10. The vane is of rectangular shape and is longitudinally creased as indicated at 12. A pull strip 14 on the normally convex side of the vane is secured to diagonally opposite corners 16 and 18 of the vane under such tension as to spring the vane against the curvature introduced by the crease 12. The pull strip 14 need not be exactly diagonal but may be connected slightly off from one corner 16. The corners 16 and 18 are preferably bent to provide a fulcrum over which the pull strip exerts a bending force on the vane and also to provide means for adjustment of the tension in the pull strip.

A contact 20 is welded to the center of the pull strip and this contact, in the cold position of the pull strip illustrated in FIGS. 1 and 2, engages under pressure a contact 22 mounted on the upper end of the upwardly extending portion 24 of terminal 6. Support 8, as shown best in FIG. 1, is welded to the vane 10 adjacent the lower edge thereof and slightly further from the corner 16 than from the other lower corner of the vane. Above the point of attachment of the support 8 to the vane 10 the support is bent outwardly and then inwardly to provide a stop 26 for the upper part of the vane 10. The stop 26, which is engaged by the vane when the vane snaps toward its constrained position upon expansion of the pull strip (see FIG. 3), enhances the noise of the operation of the flasher.

The vane of FIG. 5 differs from that of FIGS. 1 and 3 only in that the initial constraint along the central longitudinal section is provided by ribs or bosses 28 which are stamped or otherwise formed in the vane. The rib or ribs could be continuous for the length of the vane as in the case of the crease 12 of the embodiment of FIG. 1, or could be interrupted at the center of the vane, as for example, at an aperture 30 in the central portion of the vane. As will be apparent from the drawing, the ribbon 14 in the embodiment of the invention illustrated in FIGS. 1 and 5 is not exactly diagonally disposed being connected at the lower right hand edge of the vane slightly above the corner of the vane. Also, in these embodiments the ear to which the pull ribbon is attached at the lower right corner is somewhat larger than the ear at the upper left corner of the vane. The reason for the location of the lower right hand end of the ribbon and of the difference in magnitude of the ears will become apparent as the description proceeds.

The vane construction illustrated in FIG. 6 represents the presently preferred embodiment of the invention. In this construction, the ribbon 14 is connected diagonally across the vane, the ears to which the ribbon is attached are substantially of the same size, and diagonal creases 36 and 37 which are convex toward the ribbon are formed in the vane extending from a short edge toward the ribbon. The crease 36 is relatively sharper than the crease 37. In addition to the initial constraint introduced by the crease 12, two ribs or bosses 34 and 35, convex toward the ribbon, are formed in the vane along the diagonal opposite to that over which the pull ribbon is disposed. These embosses or ribs 34 and 35 are so formed as not to introduce any curvature into the vane, but are provided solely to stiffen the blade and raise the resonance frequency for purposes of better quality of the noise generated during operation of the flasher. Also to increase the quality and level of the sound an additional crease 32 convex to the ribbon side of the vane is formed in the upper half of the vane. The crease 32 extends from the upper edge of the vane toward the central hole 30 at an angle of substantially to the diagonal over which extends the pull ribbon. The crease 32 provides a backward bias to increase the stored energy by requiring an 9 increase in ribbon tension. It also stitfens the blade, and raises the resonance frequency.

Irrespective of which of the blades of FIGS. 1, and 6 is incorporated in the flasher, the operation of the device is in general like that of the aforementioned Schmidinger reissure patent in that when a circuit including a source of energy, such as a car carried battery, and a lamp load or other device to be intermittently operated is connected across terminals 4 and 6 current flows through the vane and pull strip and closed contacts 20 and 22. This current heats the pull strip and causes it to expand. Upon expansion of the pull strip the vane snaps into the position shown in FIGS. 3 and 4 in which position the contacts are open. The pull strip thereupon cools and the vane snaps back into the contact closing position of FIGS. 1 and 2. The cycle then repeats.

For flashers for automobile turn signals the industry prefers a ratio of on time to full cycle time of about 50 percent and also requires that the ratio and the rate of flashing remain fairly constant over a range of variation of supply voltage. With series type flashers in general when the battery voltage increases the on period decreases and conversely when the current decreases the on period increases. The off period remains constant. The operate and reset temperatures, and therefore the heating and cooling times, for any given flasher may by adjusted by adjustment of the initial tension of the pull ribbon, and by adjustment of the spacing of the contacts. If a lower operate and reset temperature can be employed, the on period will not vary greatly with change in operating voltag because at such lower temperatures the heating curves for the extremes of current are steeper and closer together. However, with the usual series type flasher at lower operate and reset temperature, the cooling rate is such that the off period is relatively long and hence it is diflicult to maintain the desired 50 percent ratio.

In the flasher of the invention, a faster cooling rate is obtained by so constructing the vane and by so adjusting the vane that during the off period the ribbon contacts the surface of the vane over one quandrant of the vane and therefore cools more rapidly by conduction to the vane. In order to make the ribbon thus contact the vane during the cooling period, the following conditions are required. The relationship of the points on the vane at which the ribbon i attached to the surface of the vane must lie relatively in front of the surface during the on portion of the cycle and behind the surface during the off cycle. This implies a reversal of curvature from concave to convex of a portion of the vane lying under the ribbon. When the ribbon is parallel to the major deformation of the blade, as for example, in the device illustrated in the said Schmidinger patent, or is perpen dicular to the main deformation, such reversal of curvature does not occur. With the ribbon positioned at an angle to the main deformation it becomes possible to adjust the device for proper contact of the ribbon with the vane during the off cycle. In the embodiment of the invention illustrated in FIGS. 1 and 5., the desired contact of ribbon to vane is obtained by positioning the lower end of the ribbon slightly away from the corner of the vane and by bending a larger ear at that corner than at the upper left corner of the vane. With this construction the ribbon tension can be so adjusted as to insure good contact of the ribbon with the vane during the off cycle. In the embodiment of FIG. 6, the same result i obtained by the provision of the diagonal creases 36 and 37. The crease 37 may be omitted but is of use in mass production as an additional means of adjustment. The crease 36 is relatively sharper than the crease 37 and is the prime means of adjustment to insure ribbon and vane contacts in the off period. Because of the ease with which the vane of the construction of FIG. 6 can be adjusted for the desired ribbon and vane contact, it represents the preferred embodiment of the invention and one which is now in wide commercial use.

That the ratio can be maintained substantially constant when the operate temperature of the flasher is relatively low and if the cooling rate during the off cycle is relatively rapid will become apparent from the following description of FIG. 7. In FIG. 7 the curve A represents qualitatively the average cooling rate for flasher devices of the general type of the said Schmidinger patent and reissue. The steeper curve B of FIG. 7 similarly represents the cooling rate of the device of the present invention. Curve C of FIG. 7 represents the heating rate of a pull strip of specific dimensions at an upper limit of applied voltage, say 14 volts, and curve D of FIG. 7 represents the heating rate for the same dimensioned pull strip at the lower limit of the applied voltage, say 11 volts. It will be apparent from the comparison of the curves C and D that the lower the operate temperature the less the difference will be in rate of flashing with change in operating voltage. For example, if the operate temperature is T that is if the device snaps to contact open position at temperature T then when the circuit is first closed if the supply voltage is 11 volts the flasher will snap to contact open position in a period that is longer by an interval At than when the supply voltage is 14 volts.

At a higher operate temperature, T there is a greater difference in time, At required for the flasher to snap to contact open position at 11 volts than at 14 volts. Thus the lower the operate temperature the less efifect variations in supply voltage have upon the operation of the flasher. Without the more rapid cooling of the pull ribbon, provided by applicants construction of flasher, the operate temperature for the desired 50 percent ratio must be that midway between zero and maximum temperature rise. This is because this midway temperature is the only temperature at which the heating and cooling rates of the ribbon are equal. Above this midway temperature the ratio will be over 50 percent, that is the device will be long on and below this midway temperature the ratio will be under 50 percent, or the device short on. When the cooling rate is increased in ac cordance with the invention the desired 50 percent ratio occurs at a temperature lower than the midway temperature and consequently an operate temperature may be selected in the low temperature range where difference in operating voltage has a relatively small effect upon the rate of flashing.

The invention has now been described with reference to several embodiments thereof. Obviously, changes in details of construction could be made without departing from the spirit of the invention or the scope of the accompanying claims.

What is claimed is:

1. A snap action device comprising a rectangular vane of conductive resilient material having a linear deformation therein, a pull strip for alternately snapping the vane position wherein it is buckled about an axis angularly disposed to said deformation and a second position toward which it is biased by said deformation, said alternate snapping in response to the expansion and contraction of the pull strip caused by heating and cooling of the pull strip in repetitive cycles, said pull strip overlying the convex side of the vane at an angle to said deformation and secured at its ends under tension to the vane adjacent diagonally disposed corners thereof, said pull strip in said second position being in heat conductive engagement with the surface of the vane from one point of attachment to the vane to substantially the center of the vane to employ the vane as a heat sink for cooling the pull strip to decrease the length of time necessary for the pull strip to contract and snap the vane into said first position, means for heating said pull strip when the vane is in said first position and means for supporting said vane.

2. The snap action device according to claim 1 including stiffening ribs disposed along the diameter of the vane opposite to that over which the pull strip is disposed for increasing the resonant frequency of the device.

3. The snap action device according to claim 1 wherein said vane is provided with a crease, convex toward the pull strip and extending from a shorter side edge toward the diagonal of the vane over which the pull strip is disposed, said crease tending to maintain the pull strip and vane in contact when the pull strip is expanded.

4. The snap action device according to claim 1 wherein said vane is centrally apertured and is provided with a crease, convex toward the pull strip and extending from a longer side edge toward said aperture and substantially perpendicular to the diagonal over which the pull strip is disposed.

5. In a flasher of the type which has a resilient rectangular vane With a biasing linear deformation therein and has an actuating pull strip attached to the vane adjacent two diametrically opposed corners of the vane so that when the pull strip is cold it holds the vane constrained in a first configuration in which the vane is buckled about an axis which is angularly disposed to the linear deformation and when the pull strip is heated sufficiently with respect to the vane it allows the vane to assume a second configuration towards which the vane is biased by the linear deformation, the improvement which comprises said linear deformation and said axis both being oriented at an angle to said pull strip and the vane being so contoured as to be in heat conducting contact with the pull strip from one end of the pull strip to substantially the middle of the pull strip when the vane is in its second configuration and to be out of contact with the rest of the pull strip in said second configuration.

6. A flasher comprising a resilient vane with a biasing linear deformation therein and an actuating pull strip attached to the vane and operative when it is cold to hold the vane constrained in a first configuration in which the vane is buckled about an axis which is angularly disposed to the linear deformation and when it is heated sufficiently with respect to the vane to allow the vane to assume a second configuration towards which the vane is biased by the linear deformation, said pull strip overlying the vane at an acute angle to said linear deformation and at an acute angle to said axis, and the vane being so contoured in said second configuration as to come in heat conducting contact with the pull strip from one end of the pull strip to substantially the middle of the pull strip and to be out of contact with the rest of the pull strip in said second configuration.

References Cited by the Examiner UNITED STATES PATENTS 2,254,687 9/1941 Koci 200122 2,615,106 10/1952 Schmidinger 200-122 2,712,045 6/1955 Welsh 200122 2,861,149 11/1958 Hollis et al. 200122 3,019,318 1/1962 Welsh 200122 BERNARD A. GILHEANY, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 218 ,415 November 16 1961 Henry Voorman, Jr.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 56, after "vane" insert back and forth between a first Signed and sealed this 27th day of September 1966.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer

Claims (1)

1. A SNAP ACTION DEVICE COMPRISING A RECTANGULAR VANE OF CONDUCTIVE RESILIENT MATERIAL HAVING A LINEAR DEFORMATION THEREIN, A PULL STRIP FOR ALTERNATELY SNAPPING THE VANE POSITION WHEREIN IT IS BUCKLED ABOUT AN AXIS ANGULARLY DISPOSED TO SAID DEFORMATION AND A SECOND POSITION TOWARD WHICH IT IS BIASED BY SAID DEFORMATION, SAID ALTERNATE SNAPPING IN RESPONSE TO THE EXPANSION AND CONTRACTION OF THE PULL STRIP CAUSED BY HEATING AND COOLING OF THE PULL STRIP IN REPETITIVE CYCLES, SAID PULL STRIP OVERLYING THE CONVEX SIDE OF THE VANE AT AN ANGLE TO SAID DEFORMATION AND SECURED AT ITS ENDS UNDER TENSION TO THE VANE ADJACENT DIAGONALLY DISPOSED CORNERS THEREOF, SAID PULL STRIP IN SAID SECOND POSITION BEING IN HEAT CONDUCTIVE ENGAGEMENT WITH THE SURFACE OF THE VANE FROM ONE POINT OF ATTACHMENT TO THE VANE TO SUBSTANTIALLY THE CENTER OF THE VANE OF EMPLOY THE VANE AS A HEAT SINK FOR COOLING THE PULL STRIP TO DECREASE THE LENGTH OF TIME NECESSARY FOR THE PULL STRIP TO CONTRACT AND SNAP THE VANE INTO SAID FIRST POSITION, MEANS FOR HEATING SAID PULL STRIP WHEN THE VANE IS IN SAID FIRST POSITION AND MEANS FOR SUPPORTING SAID VANE.

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