US3543208A - Snap action switch - Google Patents

Description

Nov. 24, 1970 K. R. WATSON SNAP ACTION SWITCH 3 Sheets-Sheet 1 Filed July 5. 1968 INVENTOR KENNETH R. WATSON BY ATTORYS Nov. 24, 1970 K. R. WATSON 3,543,208

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0 W 56 d A ATTORNEYS 3 Sheets-Sheet 3 Filed July 5, 1968 INVENTOR R. WATSON E; ii. NNETH ATTORNEYS United States Patent US. Cl. 337136 10 Claims ABSTRACT OF THE DISCLOSURE A snap acting electrical flasher switch for use with a directional turn signal on an automotive vehicle, the switch incorporating a spring vane of trapezoidal shape which in its free state has a central dished deformation thereon. The vane is supported on a switch base at its shorter edge and has a resistance ribbon or wire attached to the opposite ends of its longer edge so as to normally distort the vane into a bowed configuration opposite to the dished deformation. When the resistance ribbon is heated it expands, relieving the tension on the vane so that the vane flexes with a snap action toward its relaxed position and thereby acts as a switch arm to make and break with contacts controlling the turn signal.

This invention relates to snap acting electric switches and more particularly to switches of this type which are used for controlling directional turn signals on an automotive vehicle.

It is an object of the present invention to provide an electric flasher switch of the snap acting type which is reliable in its operation and which is highly efficient in relation to the current employed in the switch, the pressure exerted by the switch contacts and the stroke or travel of the contact on switch arm.

The switch of the present invention is generally of the spring vane type wherein a vane formed of a resilient conductive material is initially deformed and thereafter placed under tension by means of a resistance wire or ribbon to deform the vane in a direction opposite to the initial deformation. As the resistance ribbon is heated by passing a current through it the tension on the vane is relieved and the vane flexes toward the position determined by the initial deformation and, thus, acts as a switch arm and makes and breaks with contacts controlling the turn signal.

In the drawings:

FIG. 1 is an elevational view, partly in section, of a switch according to the present invention.

FIG. 2 is a top plan view, partly in section, of the switch shown in FIG. 1.

FIGS. 3, 4 and 5 are views similar to FIG. 2 and showing modified forms of switches according to the present invention.

FIG. 6 is a view, partly in section, showing the manner in which the vane incorporated in the switch is initially formed.

FIG. 7 shows the vane as formed by the operation illustrated in FIG. 6.

FIGS. 8, 9, 10 and 10a are perspective views of several forms of vanes constructed in accordance with the present invention.

FIG. 11 is a sectional view along the line 11-11 in FIG. 10.

Patented Nov. 24, 1970 FIG. 12 shows diagrammatically the circuitry employed with another form of vane according to the present invention.

FIG. 13 shows diagrammatically the circuity employed with another form of vane according to the present invention.

FIG. 14 shows the configuration of the vane prior to tensioning.

FIGS. 15 and 16 show the manner in which the vane deflects in operation.

Referring to FIGS. 1 and 2, the snap acting switch of the present invention includes a base 10 on which three terminal prongs are mounted on the lower side. Two of the prongs are illustrated in FIG. 1 and are designated 12 and 14. The terminal prongs are adapted for reception by a socket member in the electrical circuitry of an automotive vehicle, the circuitry including the light bulbs of the directional turn signals of the vehicle. A switch mechanism, generally designated 16, is mounted on the top side of base 10 and is enclosed by a removable cover 18. Switch 16 includes a spring bracket 20 mounted on base 10 by a rivet 22 which connects it with prong 14, a first contact bracket 24 connected by a rivet 26 with prong 12 and a second contact bracket 28 connected to the third prong on the bottom side of base (not illustrated) by a rivet 30. Base 10 is molded from an insulating plastic material such as Bakelite and on the top side thereof there is provided a pair of spaced guide ribs 32 against which the various brackets are positioned for alignment purposes. Bracket 20 is generally L-shaped as viewed in FIG. 1 and has a button 34 embossed thereon on which a spring vane 36 is welded as at 38. Bracket 24 has an upright leg 40, the upper portion 42 of which inclines upwardly and toward the center of base 10. The portion 42 has a contact 44 mounted thereon. Bracket 28 likewise has an upright leg 46, the upper portion 48 of which inclines upwardly and toward the center of base 10 and carries a contact 50. Contacts 44 and 50 are spaced apart and aligned in generally the same vertical and horizontal planes on opposite sides of spring 36.

Referring next to FIG. 7, vane 36 is formed of a thin resilient electrically conductive material such as spring steel. Vane 36, in its preferred form, has an upper edge 52, a lower edge 54 and side edges 56 which converge from upper edge 52 to lower edge 54. Vane 36 is, thus, of trapezoidal shape. At generally the central portion thereof vane 36 is formed with an aperture 58. After the central aperture is formed in vane 36, the vane is subjected to the deforming operation illustrated in FIG. 6. The deforming operation is performed by arranging the vane between a punch 60 and a die 62. Punch 60 has a center pilot 64 which extends through the central aperture 58 in the vane and into a central socket 66 in die 62. The lower end of punch 60 includes a comically-tapered outer portion 68 and a flat annular portion 70 around the central pilot 64. Die 62 has a conical upper face 72 which is tapered to correspond with the taper on the face 68 of punch 60. When punch 60 is closed upon die 62 with a vane 36 therebetween, the vane is deformed into generally conical shape as illustrated in FIG. 6 except for the annular portion 74 around the central aperture 58 which is engaged by the fiat surface 70 on the punch. The diameter of punch 60 and die 62 corresponds generally to the height of vane 36. Thus, the metal is worked into conical shape substantially entirely between the upper and lower edges of the vane.

The terms upper" and lower as used herein are by way of description only since in the embodiments illustrated the vane is positioned in the upright position illustrated in FIG. 7 and also in FIG. 1. Thus the designation top" and bottom as used in this description and in the claims are for reference purposes only to indicate the particular portions of the vane referred to regardless of whether or not the vane is located in an upright or other position. As used herein the lower edge indicates the supported edge and the upper edge designates the free edge of the vane.

The angle of inclination resulting from the initial conical deformation of the vane may vary across relatively large limits. However, it is preferred that this angle of inclination, designated a in FIG. 6, be in the range of 10 to Likewise, the flat annular section 74 of the vane may vary in diameter. It is preferred, however, to maintain the outer diameter of the flat section 74 relatively small so as to obtain the maximum flexing in the vane. Aperture 58 is formed in the vane to eliminate a concentration of stresses in the metal at the center of the conical deformation. Likewise, the flat annular section 74 is provided to prevent excessive stress around the edge of the opening 58. The minimizing of such stresses is important from the standpoint of failure due to fatigue.

After the punch and die illustrated in FIG. 6 are separated, the vane 36 no longer assumes the cross sectional shape illustrated in FIG. 6. Its inherent resiliency causes it to flatten out considerably from the conical shape illustrated so that it assumes a generally shallow arcuate dished-shaped configuration having a rather large radius of curvature. The upper edge 52 of the vane as viewed from above has the configuration illustrated in FIG. 14.

In accordance with the present invention the dished vane is then stressed by attaching a resistance wire or ribbon 76 to the upper outer corners 78 of the vane. Conductor 76 is preferably in the form of a ribbon formed of an electrically conductive material adapted to expand when heated. The ends of ribbon 76 are wrapped around the corner edges of the vane as shown in FIG. 15 and spot welded thereto. Thereafter the corners 78 are bent to tension ribbon 76 and thereby impart to the vane the bowed shape in a direction opposite to the curvature resulting from the conical deformation imparted to the vane by the operation illustrated in FIG. 6. Thus, comparing FIGS. 14 and 15 it will be observed that in the unstressed condition (FIG. 14) vane 36 bows or is dished in one direction and in the stressed condition vane 36 is bowed by ribbon 76 in the opposite direction. The bowed configuration of the vane diminishes progressively from the upper to the lower edges of the vane, the lower edge being almost straight.

The vane thus far described is shown in FIG. 8. In this embodiment a contact 80 is secured to the midportion of ribbon 76. A button 82 is also applied to the lower portion of vane to facilitate securing of the vane on the embossed button 34 on bracket by welding.

In the arrangement illustrated in FIG. 9 the configuration of the vane is the same as previously described. However, in this embodiment an electrical conductor 84 of relatively high resistance is wrapped around ribbon 76 for a purpose hereinafter described more fully. In the embodiment illustrated in FIGS. 10 and 11 the vane, designated 86, is fashioned with a pair of ears 88 along its upper edge. Bars 88 are bent as indicated in FIG. 11 to impart greater rigidity to the vane. 'Rigidity may also be imparted to the vane by bending along one of its side edges as indicated at 89 in FIG. 10a.

While each of the vanes illustrated in the drawings are of truly trapezoidal shape, the invention is not limited to a vane having this specific shape. In accordance with this invention it is preferred, although not essential, that the free edge of the vane be substantially longer than the supported edge and that the side edges generally converge toward the supported edge. This shape is preferred because, in cooperation with the circular dished deformation of the vane, the tension in the vane is spread throughout substantially its entire area and thus substantially all of the vane area contributes to its action.

The switch illustrated in FIGS. 1 and 2 is of the three terminal type and is adapted for use on vehicles wherein a single pilot light is employed on the dashboard of the vehicle for indicating when either of the directional turn signals is energized. In most cars manufactured in the US. two pilot lights are provided on the dashboard, each pilot light being connected in parallel with the load of one of the turn signal indicators. In the latter case only two terminals are required on the flasher switch. Such an arrangement is illustrated in FIG. 3 where it will be observed that the second contact bracket 28 shown in FIG. 2 has been eliminated.

FIGS. 4 and 5 show two and three terminal switches, respectively, that are adapted for use in circuits wherein the load on the switch may vary considerably. For example, in some automotive vehicles the turn signals may employ as many as six light bulbs. If one or more of the bulbs should burn out, the current in the circuit would vary considerably and ribbon 76 may operate otherwise than intended. Accordingly, where the load in the turn signal circuit may vary considerably, the resistor 84 (FIG. 9) is employed in conjunction with ribbon 76. Resistor 84 is located in heat conducting relation with ribbon 76, In the two terminal switch illustrated in FIG. 4 the arrangement is substantially the same as shown in FIG. 3 except that the vane 36 is reversed and the contact 90 secured to the vane adjacent its upper edge is normally spaced from the contact 44 on bracket 24. In the three terminal switch illustrated in FIG. 5 for use with a variable load, two contacts 90 are secured along the upper edge of the vane and a second bracket 24a is mounted On base 10 opposite bracket 24. The second bracket 24a is connected by a rivet 26a with the third prong on the underside of the base and each of brackets 24 and 24a are provided with a contact 44.

The circuit employed in conjunction with the switch shown in FIGS. 1 and 2 is shown diagrammatically in FIG. 12. In this arrangement contact on ribbon 76 is connected through its respective terminal (in this case, prong 14) by a conductor 92 with one side of the vehicle battery 94 which is grounded as at 96. Contact 44 is connected through its respective terminal (prong 12) by a conductor 98 to a selector switch 100. Contact 50 is connected through its respective terminal by a conductor 102 with a pilot light 104. Selector switch 100 is adapted to close a circuit through either of the two loads 106, 108 of the two turn signals. The pilot light and the turn signal loads are grounded as at 110. When switch 100 is in the position illustrated in FIG. 12 where it closes with load 106, a circuit is momentarily established from batery 94 through ribbon 76, contacts 80, 44 and load 106 to illuminate the turn signal with which light bulbs forming load 106 are associated. After a short period of time the current flowing through ribbon 76 causes the ribbon to become heated and thus expand. Expansion of ribbon 76 reduces the tension on vane 36 so that the vane flexes with a snap action from the position shown in FIG. 15 to the position shown in FIG. 16 where contact engages contact 50 and thus closes a circuit through the pilot light 104. After another short interval of time ribbon 76 cools, contracts and therefore again places vane 36 under tension which causes the vane and the ribbon to snap back to the position illustrated in FIG. 15 wherein contact 80 engages contact 44. Thus, the turn signal indicator and the pilot light are alternately and intermittently energized. In FIGS. 14-16 the indicia at the left represent thousandths of an inch. In the particular embodiment illustrated it is apparent that the contact gap is approximately .025". Thus contacts 80 and 90 travel about .025" as they make and break with contacts 44 and 50, respectively.

In FIG. 13 there is illustrated a circuit diagram usable with the two terminal, variable load switch illustrated in FIG. 4. In this arrangement the high resistance heater 84 has one end connected to the vane as at 112. The other end of resistor 84 is connected with contact 44 by a conductor 114. The vane itself is connected through its respective terminal to battery 94 and the selector switch 100 is connected to conductor 114. Selector switch is adapted to close a circuit through either of two indicator loads 116a and 116b, each of which has a pilot light 118a and 118b in parallel therewith. When selector switch 100 closes a circuit through load 116a, initially a circuit is established from battery 94 through a heater 84 and through the load 116a. However, since the resistance of heater 84 is very high, the current flowing therethrough is not suflicient to illuminate the light bulbs forming load 116a. After a short interval of time the heat generated by resistor 84 heats ribbon 76 sufliciently to relieve the tension on vane 36, at which time vane 36 snaps from the position illustrated in FIG. 4 to a position where contact 90 engages contact 44. This causes resistor 84 to be shunted from the circuit and the current then rises to a value sutficient to illuminate pilot light 118a and the light bulbs of load 116a.

From the above description it will be apparent that the important features of the flasher switch of this invention reside primarily in the circular dished deformation of the vane in the free state, the mounting of the vane on one side of the center of the dished deformation and the location of the tension ribbon on the opposite side of the center of the dished deformation. These features are important from the standpoint of obtaining a desirable maximum contact pressure. It will be appreciated that as Iibbon 76 is located closer to the center of the dished deformation the contact pressure will increase and the travel of the contact thereon will decrease. The proper location of ribbon 76 will represent a balance of these two factors.

By employing a vane of the preferred form, that is, of generally trapezoidal shape as distinguished from a generally rectangular shape, with the ears 88 at the upper outer corners bent as shown in conjunction with the circular dished deformation, the entire working area of the vane contributes favorably to its deflection and contact pressure characteristics. This shape results in a minimum of excess material around the periphery of the vane which might have an undesirable tendency to stiffen it and render it less flexible. On the other hand, if the vane were triangularly shaped and mounted at one apex of the triangle it would have substantially less rigidity and, while the deflection characteristics might be suitable, it might be more diflicult to obtain the requisite contact pressure. Generally speaking, it is desirable in a flasher switch of this type to have a contact gap of about .015" to .030" and a contact pressure of about 30 to 50 grams. These requisites are readily obtained with the preferred form vane disclosed herein. In this connection it will be observed that the expansible ribbon 76 is relatively long and, therefore, capable of expanding sufliciently under normal current conditions to produce the desired snap action.

Merely by way of example, a vane of trapezoidal shape having the desired operating characteristics has been formed of spring steel having a thickness of about .005" with the upper edge about 1" long, the lower edge about .435 long and the height of the vane about .560". The central aperture 58 has a diameter of about .062" and the flattened area 74 has a diameter of about .154". With the vane so dimensioned a linear expansion of ribbon 76 in the amount of .001" to .003" resulted in a contact travel of approximately .025" and a contact pressure of between 30 and 50 grams. It is to be understood, however, that a satisfactory switch can be produced with differently shaped and dimensioned vanes, the vane specifically described being merely illustrative of one satisfactory form.

I claim:

1. A snap acting electric switch including a base having a contact supported thereon in fixed position, a switch arm comprising a vane formed of electrically conducting resilient material, said vane being of generally trapezoidal shape and having generally straight opposed upper and lower edges connected at each end by generally straight side edges which incline downwardly toward each other so that the lower edge of the vane is substantially shorter than the upper edge, means adjacent said lower edge mounting said vane on said base, said vane having an aperture at the center thereof and having a generally smooth continuous surface throughout its extent except for the hereinafter mentioned bend lines, said vane in its free state having a central circular dished configuration of arcuate cross section which is symmetrical about its central vertical and longitudinal axes and which in vertical section through said central aperture defines a smooth arcuate curve extending to the upper and lower edges of the vane, the outer upper corners of said vane when in the free state being flat, said switch arm also including an expansible electrical conductor secured at each of its opposite ends to said upper outer corners of the vane and extending along a line offset from the center of said dished deformation in a direction opposite from said mounting means, said conductor being secured to said vane under tension and imparting to substantially the entire extent of said vane except for said upper outer corners a bowed configuration opposite to that produced by said dished deformation, said upper outer corners being inclined to the plane of the vane in the direction of the concave side of said dished deformation and being connected with the central portion of the vane by bend lines which extend in a direction transversely of the longitudinal axis of the vane and contact means on said switch arm located between the center of said dished deformation and the upper edge of the vane for engagement with said fixed contact, said conductor, when heated, expanding to an extent relieving the tension on the vane and causing the vane to flex laterally about said mounting means with a snap action toward a relaxed position as determined by said dished deformation such that the contact means on the switch arm make and break with the contact on the base.

2. A switch as called for in claim 1 wherein the side edge portions of the vane are inclined to the plane of the vane in the same direction as said upper outer corners and are connected with the central portion of the vane by bend lines which extend generally parallel to the side edges of the vane.

3. A switch as called for in claim 1 wherein said con ductor and said contact on the switch arm are located adjacent the upper edge of the vane.

4. A switch as called for in claim 1 wherein said upper edge has a length about twice the length of the lower edge.

5. A switch as called for in claim 4 wherein the vane has a vertical dimension substantially less than the length of said upper edge.

6. A switch as called for in claim 4 wherein the vane has a vertical dimension approximately equal to the length of the lower edge.

7. A switch as called for in claim 1 wherein said vane is provided with a generally flat annular section concentric with and immediately adjacent said central aperture.

8. A switch as called for in claim 1 wherein said side edges converge symmetrically about the vertical central line of the vane.

9. A switch as called for in claim 1 including a pair of integral inwardly projecting ears on said upper edge of the vane which are inclined to the plane of the vane.

10. A switch as called for in claim 9 wherein said ears v 7 v are spaced apart symmetrically on opposite sides of the 3,088,012 4/1963 Welsh 337136 vertical central line of the vane. 3,080,464 3/ 1963 Kurz 337136 BERNARD A. GILHEANY, Primary Examiner References Cited 5 D. M. MORGAN, Assistant Examiner UNITED STATES PATENTS 3,349,205 10/1967 Taylor 337-138 U.S. C1.X.R. 3,218,415 11/19'65 Voorman 337-139 337-438

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