Snap Action Switch

Abstract

An electromechanical switch that includes an electrically conductive sheet having a spring-like pattern of apertures therethrough, a printed circuit electrical conductor and an apertured insulating spacer therebetween for permitting the center portion of the pattern to make electrical contact therewith when the pattern is forced out of the plane of the conductive sheet by an actuatable plunger.

Description

BACKGROUND OF THE INVENTION

Keyswitches associated with the keyboards of electronic data processing systems are available in many designs--see "Keyswitches and Keyboards", EEE, November 1970, pages 64 - 73. Recent developments include printed circuit keyboards having keyswitches that include pressure sensitive materials whose resistivity decreases with applied pressure to make an electrical interconnection as in the K. Nyhus, et al. U.S. Pat. No. 3,503,031 and two electrical conducting layers separated by an apertured electrical insulator wherein under applied pressure one layer is forced through the aperture to make electrical contact with the other layer as in the M. Krakinowski U.S. Pat. No. 3,308,253. The present invention is considered to be an improvement over such known arrangements using fewer components while providing desirable operator feedback.

SUMMARY OF THE INVENTION

The present keyswitch includes a novel electrical conducting planar spring member which under pressure is forced through the aperture in a separating electrical insulator to make electrical contact with a sandwiching electrical conductor. The spring member is preferably chemically machined out of a thin sheet member of electrical conducting material being formed of a plurality of concentric pairs of apertures, each pair being formed along two arcs of a circle. Adjacent concentric pairs of apertures are alternately rotated about the common center for providing the desired physical characteristics. The arrangement requires only the two conducting members and the insulating member with a suitable supporting substrate while providing the desired low tactile resistance and high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the spring member of the present inventions.

FIG. 2 is a cross-section of the spring member of FIG. 1 taken along line 2 - 2.

FIG. 3 is a plan view of a portion of a keyboard incorporating the present invention.

FIG. 4 is a cross-section of a keyswitch of FIG. 3 taken along line 4- 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With particular reference to FIG. 1 there is presented a plan view of the spring member of the present invention. Spring 10 consists of electrically conducting sheet member 12 having a plurality of concentric pairs of apertures 14a, 14b;...26a, 26b preferably chemically machined therethrough--see U.S. Patent No. 3,421,865. The pairs of apertures, e.g., outermost pairs of apertures 14a, 14b, are formed as two arcs of the same circle, preferably of less than 180.degree. but greater than 90.degree., with alternate pairs of apertures, e.g., 14a, 14b and 16a, 16b, being rotated approximately 90.degree. with respect to each other and being separated by lands, e.g., 15a, 15b. Lands, e.g., 19a, 19b between internal pairs of apertures, e.g., 18a, 18b are the means whereby structural and electrical continuity are maintained between the internal center portion 28 of spring 10 and the portion of member 12 that is external to spring 10. In a preferred embodiment of spring 10, sheet member 12 is 0.005 inch thick one-half hard beryllium copper sheet with the apertures being 0.010 inch wide having a 0.040 inch land therebetween on 0.030 inch radial spacings with the inside diameter of outermost apertures 14a, 14b being 0.670 inch, all pairs of apertures 14a, 14b;...26a, 26b being concentric about center portion 28.

With particular reference to FIG. 2 there is presented a cross section of spring member 10 taken along line 2--2 of FIG. 1. FIG. 2 illustrates that spring 10 is a flat, i.e., planar, member in which the center portion 28 is depressed, e.g., 0.030 inch, for receiving the associated keyswitch plunger. This illustrated preferred design provides a uniform and linear deflection along a line that is orthogonal to the plane of member 14 and through the intersection of orthogonal axes 32, 34 over an excursion of 0.090 inch requiring a uniform and linear pressure of only 0.50 ounce.

With particular reference to FIG. 3 there is presented a plan view of a portion of a keyboard in which the present invention is incorporated. The illustrated keyboard includes a keyboard panel 40 through which protrudes a plurality of keyswitches 42 such as illustrated in the above referenced EEE article.

With particular reference to FIG. 4 there is presented a cross section of the keyswitch 42 of the present invention taken along line 4--4 of FIG. 3. Keyswitch 42 includes a key 44 that is secured to plunger 46. Plunger 46 is actuatable secured in plunger bushing 48, which in turn is secured to spacer sheet 50 by push-on nut 52. Keyboard panel 40 is secured to spacer 50, which functions as a supporting chassis for bushing 48, using spacers 54 and suitable attaching hardware. Plunger 46 is restricted in its upward movement by opposing flange members 56. This arrangement is similar to that of the UNIVAC 100 Keyboard except that a plunger boot (not illustrated but see the F. Carpentier patent application Ser. No. 6818 Pat. filed Jan. 29, 1970, now U.S. Pat. No. 3,603,756) is utilized to maintain plunger 46 in its upward normal undepressed condition with the top surfaces of flanges 56 against the bottom surface of bushing 48.

The present invention involves the addition of the switching assembly 60 that is assembled to the above described keyboard by means of spacers 62 and attaching hardware 64. Assembly 60 includes printed circuit board 66 having a plurality of printed circuit conductors 68 formed thereon, electrical insulating, dielectric, spacer 70 having a circular aperture 72 centered about axis 47 of plunger 46 and electrical conducting member 12 having spring 10 centered above aperture 72. In the illustrated preferred embodiment printed circuit board 66 is of laminated fiberglass of 0.062 inch thick with printed circuit conductors 68 being formed by conventional printed circuit techniques of a 2 ounce copper layer. Insulation spacer 70 is an epoxy glass layer of 0.125 inch thick with apertures 72 of 0.690 inch diameter as required by the particular design of spring 10 which is as described with particular reference to FIGS. 1, 2.

In a normal undepressed condition of keyswitch 42 the rounded tip 58 of plunger 46 is centered in the depressed portion 30 of center portion 28 of spring 10 with spacers 62 chosen of such a length to maintain the top surfaces of flanges 56 of plunger 46 against the bottom surface of bushing 48 by the spring pressure of spring 10. Upon depression of key 44 and plunger 46 the center portion 28 of sheet member 12 is brought into electrical contact with printed circuit conductor 68 on printed circuit board 66. With sheet conductor 12 being maintained in a predetermined positive potential as a voltage signal plane the one particular printed circuit conductor 68 associated with the one activated or depressed keyswitch 42 functions as an encoding network emitting a signal that is representative of the function or symbol associated with the associated activated keyswitch 42.

Spring 10 may be utilized to provide both tactile- and audible-feedback to the keyboard operator for providing the desired psychological effects. The movement of, e.g., 0.090 inch of the plunger 46 upon the slight finger pressure of, e.g., 0.50 ounce, to an abrupt stop provides a desirable tactile-feedback while the movement of a center portion 28 out of the plane of sheet member 12 provides an audible click. Accordingly, it is apparent that applicant has provided herein an improved keyswitch and spring therefor.

Claims

What is claimed is:

1. A keyswitch comprising:

a key having a plunger coupled thereto;

chassis means for supporting said plunger in an actuatable manner;

a first conductive planar sheet member having a planar spring-like pattern formed therein, said pattern comprising a plurality of concentric pairs of appertures therethrough with adjacent pairs of apertures having increasing radii from a common center portion, the apertures of each pair being circular arcs of equal radii and less than 180.degree. but greater than 90.degree. wherein alternate pairs of apertures are rotated approximately 90.degree. with respect to each other about said common center portion which is defined by the innermost pair of apertures;

spacer means arranging said common portion in compressive contact with said plunger for maintaining said plunger in an unactuated condition;

a second conductive member oriented below said common center portion;

an electrically insulating member for normally separating said second conductive member and said common center portion but permitting said common center portion to make electrical contact with said second conductive member when said common center portion is forced through the plane of said electrically insulating member by said actuated plunger.