Keyboard Switch Assembly With Multi-sectional Key Actuator

Abstract

A keyboard array including a board having a conductive pattern thereon, a resilient conductive layer, a first or external plunger supported in a housing and slidable therein, a second or internal plunger supported in the external plunger and first resilient biasing means urging the first plunger towards the housing and away from the conductive layer and a second resilient biasing means urging the second plunger away from the first plunger and towards the conductive layer.

Description

STATEMENT OF INVENTION

This invention is directed to a new and improved keyboard key or switch construction and is more particularly directed to a new and improved switch or key actuator for causing a conductive layer to engage an electrically conductive pathway upon depression thereof.

The actuating means of this invention is useable in place of the switch actuating means disclosed in copending U.S. Pat. applications, Ser. No. 145,212 filed May 20, 1971 by Richard E. Seeger,Jr. and George T. Hodgson,Jr. now U.S. Pat. No. 3,705,276 and Ser. No. 154,752 filed June 12, 1971 by Richard E. Seeger,Jr. and William J. Lynn now U.S. Pat. No. 3,721,778. The entire disclosure of these patent applications being incorporated herein by reference hereto.

The actuating means of the present invention permits the construction of a simple and highly reliable keyboard at low cost. The actuating means is adapted to be constructed of primarily molded parts which when placed together form a modular unit. The modular units may then be individually mounted on a circuit board construction,as shown in the foregoing mentioned applications, in any number required by the application intended.

BRIEF DESCRIPTION OF THE INVENTION

The keyboard array of this invention includes a printed circuit board having circuit pathways or contacts thereon, a mask having a window therethrough in alignment with a portion of one or more of the circuit pathways, a conductive layer positioned over the mask and adapted to extend through the hole into engagement with at least one of the electrical pathways upon the application of a force thereto and also adapted to spring back from the electrical pathways out of electrical contact upon removal of the force and at least one actuator modular unit adapted to be coupled to the board and having an internal plunger member slidably housed with exterior plunger member and adapted to apply a force against the conductive layer, the exterior plunger member supported in a housing coupled to the board, first resilient biasing means urging the external plunger away from the conductive layer and second resilient biasing means urging the internal plunger towards the conductive layer and allowing the internal plunger to retract into the external plunger to prevent the application of an excess force against the conductive layer. In addition, there is provided snap means forming part of the external plunger for retaining part of the internal plunger within a bore of the external plunger and an insulator layer positioned on the conductive layer and having a window therethrough to permit the internal plunger to contact the conductive layer, the housing and first resilient biasing means resting upon this insulator layer in the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a keyboard with parts cutaway showing the invention;

FIG. 2 is a sectional view taken along line 2--2 in FIG. 1;

FIG. 3 is a sectional view similar to FIG. 2 with the switch in the actuated position;

FIG. 4 is a sectional view taken along line 4--4 in FIG. 2;

FIG. 5 is a sectional view taken along line 5--5 in FIG. 2; and

FIG. 6 is a side view of a portion of the internal plunger.

BRIEF DESCRIPTION OF THE INVENTION

Reference should now be had to FIGS. 1-5 for the detailed description of the invention. At 9 there is shown a keyboard which includes an outer decorative frame 10 in which there is positioned the operating parts of the keyboard. See U.S. Pat. No. 3,705,276 for an illustration of suitable frame mounting. The operating parts include an insulator board 11 (e.g., Bakelite, Formica) of the conventional type used in printed circuit applications and having a plurality of mounting holes 11a formed therethrough.

At 12 there is provided electrical contact means or electrical pathways formed on the board using conventional printed circuit etching techniques wherein copper is etched away or the contact means may be formed by other conventional screening techniques wherein an electrically conductive coating is laid down to form a circuit pattern. Various circuit patterns are shown in the aforementioned patent applications which are incorporated herein.

At 13 there is shown an insulator layer, for example of plastic such as sold under the trademark Mylar and having a window 13a extending therethrough in line with at least a portion of the electrical contact means 12.

A resilient electrically conductive layer or sheet is shown at 14 and is of a type of a material which may be forced through the window 13a into contact with the contact means 12 with the application of a force thereto (see FIG. 3) and then spring back to the position shown in FIG. 2 when the force applied thereto is removed. Various materials may be used as the conductive layer as set forth in the aforementioned referred to applications with the preferred material being a conductive plastic preferably formed of silicone rubber (rubber is defined as a plastic in the context used herein) filled with silver flakes, i.e., between 10 to 80 percent by volume.

At 15 in the drawing there is provided a mounting pad or layer 15 of insulating material i.e., of plastic such as sold under the trademark Mylar. The pad 15 is provided with a window 15a therethrough in alignment with at least a portion of the window 13a.

Each of the layers 13, 14 and 15 are also provided with mounting holes 13b, 14b and 15b respectively, positioned in alignment with hole 11a formed in the board 11. At 20 there is shown a plurality of modular key units or actuating units adapted to be individually mounted on the board 11. Each of the units 20 comprises a key portion 21 upon which indicia e.g., numbers or letters (see FIG. 1) may be applied.

The key portion 21 is mounted on a first or external plunger or actuating member 22 which includes a bore 22a having resilient snap members 22b at the bore 22a opening. The plunger 22 is positioned for slidable movement within a housing 25 and is preferably prevented from rotating by guide means such as tongues 22e positioned in channels 25d. The upper limit of movement of the plunger 22 within the housing 25 is determined by a shoulder 25a formed within the housing.

The housing 25 is provided with mounting members 25b which extend through layer 11,13,14 and 15 holes 11b, 13b, 14b and 15b respectively, and are provided with retaining heads 25c.

In the preferred construction of the housing 22, it is constructed of plastic with the members 25b being initially rods. The plastic used for housing is selected of a plastic material e.g., polypropylene, nylon, which may be softened and shaped to form the retaining heads after the assembly is formed.

Nuts may also be used to mount the units 20 on the board 11 by forming threads at the end of the members 25b. At 26 there is shown a second or internal plunger or actuating member which includes portion 26a slidably movable within the bore 22a and retained therein by the snap members 22b.

The snap members 22b are bendable backward to permit entry of the portion 26a, and the portion 26a is provided with tapered slots 26aa to facilitate entry of the member 26a into the bore 22a (see FIG. 6). In order to permit slidable movement of the portion 26a within the bore 22a without excessive force there is provided air vents or exit channels 25d in the bore.

Extending from the plunger portion 26a is a shaft member 26b which supports a pusher portion 26c. The pusher portion 26c is provided with a tip which is adapted to push the conductive layer 14 through the window 13a to make contact with the contact 12 (see FIG. 3).

In order to effect control of the plungers 22 and 26 there are provided resilient biasing means or springs 27 and 28. The spring 27 biases the first plunger 22 against the housing shoulder 25a and away from the conductive layer and is positioned at one end on the pad 15 and is located by the interior of the member 22.

Spring 28 is positioned between the first plunger 22 bottom and the pusher portion 26c and urges the plunger 26 towards the conductive layer and is located at its ends about a cylindrical tier 22d formed on the plunger 22 and a cylindrical tier 26d.

The spring 28 acts as an overload spring to permit the member 26 to move rearwardly if an overload force is applied to the key 21. This is accomplished by selecting the spring 28 so that after member 26 has bottomed additional force applied to the key and the first plunger causes the plunger 26 to overcome the force applied by the spring 28.

In addition, the bore is made longer than the member 26a so that rearward motion is possible. In operation the key 21 is pressed to cause the first plunger 22 to move the second plunger 26 therewith to cause the conductive layer to make contact with the contact 12. If the conductive layer is grounded as disclosed in the aforementioned U.S. Pat. No. 3,721,778 and the contact is high (+) then a circuit will be completed and the current will flow.

Alternatively the electrical contact 12 may be segmented as shown in the aforementioned U.S. Pat. Nos. 3,705,276 and 3,721,778 and electrical contact may then be made between the segments to complete a circuit.

In order to make electrical contact with the segments or conductive layer from external circuitry, pins or connectors are employed as shown in the aforementioned patent applications.

Claims

We claim:

1. In a keyboard array including an insulator board supporting a circuit having at least one electrically conductive contact provided on one surface of said board, a resilient conductive layer means positioned to make contact with said contact upon application of a force thereto, and means separating said conductive layer means from said contact and having a window therethrough which said conductive layer may extend to make contact with said electrical contact, the improvement comprising an external plunger having a bore, an internal plunger slidably movable within a bore formed in an external plunger, a housing slidably supporting said external plunger, means coupling said housing to said board, first resilient biasing means biasing said external plunger away from said conductive layer means, second resilient biasing means biasing said internal plunger towards said conductive layer, said internal plunger positioned to apply a force against said conductive layer means to make electrical contact with said contact upon the application of a force applied to said external plunger, a key mounted on said external plunger and snap members provided on said external plunger to confine a portion of said internal plunger within said bore thereof.

2. In a keyboard array according to claim 1 in which said plunger portion positioned in said bore has tapered slots to permit easy entry into said bore.

3. In a keyboard array according to claim 2 in which vent channels are provided to facilitate movement of said internal plunger in said bore.

4. In a keyboard array according to claim 3 in which means are provided on both of said plungers for locating said second biasing means and wherein means are provided on said housing and external plunger for locating said first biasing means.

5. In a keyboard array including an insulator board supporting a circuit having at least one electrically conductive contact provided on one surface of said board, a resilient conductive layer means positioned to make contact with said contact upon application of a force thereto, and means separating said conductive layer means from said contact and having a window therethrough which said conductive layer may extend to make contact with said electrical contact, the improvement comprising an external plunger, an internal plunger slidably movable within a bore formed in an external plunger, a housing slidably supporting said external plunger, means coupling said housing to said board, first resilient biasing means biasing said external plunger away from said conductive layer means, second resilient biasing means biasing said internal plunger towards said conductive layer, said internal plunger positioned to apply a force against said conductive layer means to make electrical contact with said contact upon application of a force applied to said external plunger, a key mounted on said external plunger, and said array comprises a sandwich of said board, said circuit having said conductive contact on said board, said insulator layer having a window therethrough in alignment with at least a portion of said contact,said resilient conductive plastic layer means positioned on said insulator layer and said housing mounted with said plunger mounted on top of said conductive layer means.

6. In a keyboard array according to claim 5 in which an insulator pad having a window therethrough in alignment with at least a portion of said window of said insulator layer and in which said housing has mounting portions which extend through holes formed in said pad, conductive layer, insulator layer means and board for joining said sandwich together.

7. In a keyboard array according to claim 2 in which said external plunger and said housing are provided with guide means for preventing rotation of said external plunger.

8. A key construction comprising a housing, a first plunger having at least a portion slidably movable within said housing and having a key attached thereto, a second plunger having a portion slidably movable within a portion of said first plunger, first resilient biasing means positioned between said plungers to urge them away from each other, said second plunger includes a portion having tapered slots and wherein said first plunger has resilient projections, said slots pushable over said projections to snap said second plunger into said first plunger and retain said second plunger within said first plunger for slidable movement therein.