Printed Circuit Keyboard

Abstract

A printed circuit keyboard having contacts thereon with leads from the contacts passing through the board and connected to conductors on the underside of the board. A ground plane in the form of a conductive sheet is positioned above the contacts and biased out of contact therefrom. This sheet could be Mylar plated with nickel. The Mylar sheet is positioned over an apertured member aligned with the contacts to provide the biasing. The Mylar is sufficiently taut so that only one contact can be positioned against the depressed Mylar sheet at one time. A cellophane or other member can be placed over the Mylar and aligned with the apertures to provide numeric indicators for the keyboard.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosure relates to a printed circuit keyboard and, more specifically, to a keyboard composed of a printed circuit and flexible conductive members operated by manual depression to provide an electrical impulse corresponding to the character selected.

2. Description of the Prior Art

Keyboards have been well known in the prior art for use in calculating machines, punches and the like. Such keyboards have always been of mechanical construction utilizing keys, springs and electrical contacts and the like and, though providing satisfactory results, have been relatively expensive to produce. Furthermore, the prior art keyboards have been difficult to replace and have required expensive repair operations in many cases when breaking down. The prior art keyboards have also not been easily dismantled from the associated machine and have not been interchangeable with other keyboards.

In accordance with the present invention, there is provided a relatively inexpensive printed circuit keyboard which overcomes the problems inherent in the prior art, which can be easily plugged into and removed from associated equipment and which is of sufficiently inexpensive construction to allow disposal thereof and replacement with a new keyboard in the event of a breakdown. Furthermore, the printed circuit keyboard of the present invention has a minimum of mechanical parts and, therefore, is less likely to fail during operation as compared with prior art mechanical keyboard devices.

SUMMARY OF THE INVENTION

Briefly, the above is provided in two embodiments of a printed circuit keyboard wherein a predetermined number of contact locations is provided on the upper surface of the printed circuit board, the contact locations being connected to conductors, one for each contact location, positioned on the underside of the printed circuit board and plated through the printed circuit board or connected in any other known manner. The contact locations are separated from a flexible conductive member by a separator of predetermined thickness. The separator includes apertures, one aligned with each of the contact locations. Above the flexible conductive member is placed an additional flexible member having characters, or the like, printed thereon and aligned with the contact locations. Positioned thereover, is an additional flexible clear material for protecting the flexible character-bearing surface. Positioned above the clear flexible member is a cover of metal, plastic, or the like, having apertures therein aligned with the apertures of the separator and all of the members are then held together by passing nut and bolt members through each of the layers.

In accordance with the second embodiment of the invention, the flexible conductive layer is replaced by a plurality of flexible conductor strips, one strip aligned with each row of the contact locations. The strips, through flexible, are sufficiently taut whereby, when the strip is depressed to come in contact with one of the contact locations, the strip is of such tautness that it is impossible to depress the strip at other locations of the row. Positioned above the strip, in alignment with each of the contact locations, is a spring member over which is positioned a key bearing a character reference thereon. The entire assembly is then enclosed in a cover member similar to the cover of the first embodiment and the members are all fastened together by means of screws. Each of the embodiments is then available to be plugged into a keyboard-operated device in the same manner in which printed circuit boards are normally connected, as is well known in the prior art.

It is, therefore, an object of this invention to provide a printed circuit keyboard which is relatively inexpensive to manufacture.

It is a further object of this invention to provide a printed circuit keyboard which can be readily plugged in and removed from associated equipment.

It is a still further object of this invention to provide a printed circuit keyboard having substantially no moving mechanical parts and substantially free of failure.

It is a yet further object of this invention to provide a printed circuit keyboard having a built-in interlock without using additional interlock elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and further objects of the invention will immediately become apparent to those skilled in the art after consideration of the following preferred embodiments of the invention which are provided by way of example and not by way of limitation and the accompanying drawings wherein like reference characters represent like or corresponding parts throughout the several views and:

FIG. 1 is an exploded view of the printed circuit keyboard in accordance with the first embodiment of the invention;

FIG. 2 is a perspective view of the assembled keyboard in accordance with the first embodiment of the invention;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is an exploded view of a second embodiment of the printed circuit keyboard in accordance with the present invention;

FIG. 5 is a perspective view of the assembled keyboard in accordance with the second embodiment of the present invention; and

FIG. 6 is a cross-sectional view taken along the line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown an exploded view of a first embodiment of the keyboard of the present invention. The keyboard includes a printed circuit board 1 having contact locations 3 positioned in rows on the upper surface thereof. Each contact location 3 is electrically connected to an associated conductor 5 which is formed on the reverse side of the printed circuit board 1 and is connected to the contact location by plating through holes in the board, or by any other method which is known in the art. The extension 27 of the board 1 extends outwardly for insertion in an associate device and contains an electrically conductive layer on the top surface thereof. The conductors 5 extend to the outer edge thereof along the lower surface of the extension 27. Positioned above the printed circuit board 1 is a separator 7 of thickness greater than that of the contact locations 3 and having a plurality of apertures 9 therein, each of the apertures 9 being aligned with one of the contact locations 3. A flexible sheet 11, either of electrically conductive material or having a conductive layer at its lower surface as, for example, a Myler sheet plated with nickel, is positioned above the separator 7. The layer 11 includes an extension 31 which will be positioned on the top surface of extension 27 to provide an electrical connection between the top surface of the extension 27 and the electrically conductive portion of the sheet 11. A further flexible layer 13, having character numerals thereon, is positioned over the flexible conductive sheet 11, the numerals being aligned with the apertures 9 in the separator 7. A flexible transparent sheet 15 is positioned above the flexible layer 13, this layer being made of any clear flexible material as, for example, cellophane. A cover 17, which can be made of metal, plastic, or other suitable material, is placed over the flexible transparent sheet 15; the cover 17 including apertures 19 therein for alignment with the character numerals of the flexible layer 13, the apertures 19 also being in alignment with the apertures 9 of the separator 7. Each of the sheets or lamina 1, 7, 11, 13, 15 and 17 includes a plurality of bolt receiving apertures 21 which are aligned with each other and through which bolts 23 can be passed for connection with nuts 25 to provide the completed keyboard.

The flexible conductive layer 11 provides a ground plane and is made sufficiently taut so that the passing thereof through one of the apertures 9 and against one of the contact locations 3 will make the layer 11 sufficiently taut so that it is impossible to simultaneously depress the flexible conductive sheet 11 through another one of the apertures 9 and against a contact location. In this way, an interlock is provided without the addition of mechanical or electrical parts. The completed keyboard is shown in FIG. 2 with the alphanumeric characters visible through the apertures 19. The extension 27 of the printed circuit board 1, having an electrically conductive surface on one side, is shown extending beyond the laminated layers, the conductors 5 of the printed circuit board being on the opposite side and extending to the outer edge of the extension 27 for plug-in connection to an associated device.

Referring now more specifically to FIG. 3, the keyboard, in accordance with the first embodiment, is operated by manual depression of the layers through one of the apertures 19 of the cover 17 by means of a finger, or the like, 29. All of the flexible layers 11, 13 and 15 are depressed whereby the electrically conductive flexible layer 11 makes electrical contact with the contact location 3, as shown clearly in FIG. 3. This completes the circuit through the conductive layer 11 and specifically the extension 31 thereof which is electrically coupled to the top surface of the extension 27, through the particular contact location 3 and along the conductor 5 associated therewith to complete the circuit and provide a signal indicative of the particular key depressed when opposite sides of a power source are coupled to the conductors 5 and the sheet 11, respectively. When the manual force is released, the flexible layers are relaxed which causes the conductive sheet 11 to no longer lie in contact with the associated key contact location 3.

It can be seen that the keyboard of FIGS. 1 to 3 is of simple and relatively inexpensive construction, is easily inserted and removed from associated equipment and, therefore, can be easily replaced. The keyboard also includes the advantages built into prior art mechanical keyboards only with great difficulty and yet requires no electronic components.

Referring now to FIGS. 4 to 6, there is shown a second embodiment of the keyboard in accordance with the present invention. In FIG. 4 there is shown an exploded view of the keyboard in accordance with the second embodiment, this keyboard including a printed circuit board of identical construction to that of the first embodiment. The printed circuit board 1 includes contact locations 3 and conductors 5, as well as aligning screw-receiving apertures 21 and an extension 27 under which extend the conductors 5, the extension 27 being utilized for plug-in connection to associated apparatus and having its upper surface coated, or plated, with an electrically conductive layer. Above the printed circuit board 1 is a separator 7 of construction similar to that of the first embodiment, having apertures 9 therein. COnductive strips 33 and 35 are electrically coupled to the top surface of the extension 27 and extend along separator member 7 between apertures 9 thereof and a plurality of flexible conductive strips 37 positioned over the conductive strips 33 and 35, there being one flexible conductive strip for each row of apertures 9 in the separator 7. The flexible conductive strips 37 can be made of the same materials as the flexible conductive sheet 11 of the first embodiment. The flexible conductive strips 37 are made sufficiently taut so that the depression of said strip through the aperture 9 at one location to contact the contact location 3 aligned therewith will make the flexible conductive strip sufficiently taut so that it is impossible to simultaneously depress the strip through another aperture 9 simultaneously, thereby providing an interlock as in the first embodiment. Positioned above the flexible strip 37 and aligned with each of the apertures 9, is a spring 39 which fits around a depending member 43 of a key 41. A cover 45 fits over the entire set of layers, screw members 47 being passed through the apertures 21 and being screwed into a threaded portion in the cover 45 as best shown in FIG. 6. The completed keyboard, in accordance with the second embodiment, is shown in FIG. 5 with the extension 27 from the printed circuit board for connection to associated apparatus, as well as the strips 33 and 35 for providing power from one side of a power source to the conductive strips 37.

The keyboard of the second embodiment is operated in substantially the same manner as the first embodiment, as shown most clearly in FIG. 6. A key 41 will be depressed and the depending member 43 thereof will force the spring 39 downwardly and also force the portion of the flexible conductive strip 37 associated therewith downwardly through the aperture 9 and against the contact location 3, thereby completing the circuit and providing an indication of the particular key depressed. THe interlock is provided, as explained hereinabove, due to the precontrolled tautness of the flexible conductive strip 37. It can be seen that, when the operator's hand is removed from the key 41, the key will be returned to its original position due to the force provided by the spring 39, thereby removing the flexible conductive strip 37 from contact with the contact location 3 and removing the signal provided thereby from the system.

It can be seen that a keyboard is provided which is relatively inexpensive to produce, which is interchangeable with other keyboards and readily inserted and removed from associated apparatus. The keyboard of the present invention also includes features of prior art mechanical keyboards which were provided only by the inclusion of very complex mechanical and/or electronic devices.

Though the invention has been described with respect to specific preferred embodiments thereof, many variations and modifications will immediately become apparent to those skilled in the art. It is, therefore, the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.

Claims

What I claim is:

1. A manually actuatable keyboard assembly comprising:

a base member having a plurality of spaced contact members thereon;

a first grid member positioned adjacent said base member and having a plurality of first apertures, with individual ones of said first apertures aligned with individual ones of said contact members;

a second grid member positioned adjacent said first grid member and having a plurality of second apertures, with individual ones of said second apertures aligned with individual ones of said first apertures;

a resilient conductive sheet member disposed between said first and second grid members for contacting said contact members in response to actuating forces applied through individual ones of said second apertures in the direction of said base member, said conductive sheet member including interlock means preventing contact with more than one of said contact members in the presence of said forces at more than one of said second apertures; and

an indicator sheet disposed above said conductive sheet member and having a plurality of symbols thereon, individual ones of said symbols aligned with individual ones of said first apertures.

2. The keyboard assembly of claim 1 further including a transparent protective sheet disposed above said indicator sheet.

3. The apparatus of claim 1 wherein said first and second apertures have substantially identical dimensions.

4. THe apparatus of claim 1 wherein said second apertures are dimensioned to receive an actuating member.

5. The apparatus of claim 1 wherein said base member further includes a connector portion, a plurality of conductor paths mounted on the underside of said base member, with individual ones of said conductive paths connected at a first end to individual ones of said contact members, the second end of each of said conductor paths terminating at said connector portion, and a common conductive terminal positioned on the upper side of said base member along said connector portion.

6. A manually actuatable keyboard assembly comprising:

a base member having a plurality of spaced contact members thereon;

a grid member positioned adjacent said base member and having a plurality of apertures, with individual ones of said apertures aligned with individual ones of said contact members;

a plurality of manually actuatable key members positioned adjacent said grid member for reciprocable motion in the direction of said base member, with individual ones of said key members aligned with individual ones of said apertures, each of said key members having a projection extending in said direction and adapted to enter its associated aperture in response to an actuating force;

a plurality of spring members associated with said key members, individual ones of said spring members mounted between said grid member and a selected portion of said associated key member to provide an upward force biasing said associated key member in a nonactuated position;

a cover member positioned adjacent said grid member and having a plurality of apertures aligned with said grid apertures, individual ones of said cover apertures adapted to slidably receive individual ones of said key members; and

at least one resilient conductive strip disposed between said grid member and said cover member and across selected ones of said grid apertures for contacting said aligned contact members in response to the actuation of said aligned key members and corresponding motion of said projections in said direction;

said conductive strip including interlock means preventing contact with more than one of said contact members when more than one of said aligned key members has been actuated.

7. The keyboard assembly of claim 6, wherein said grid apertures are arranged in a plurality of rows, and wherein each of said rows is provided with an associated conductive strip.

8. The apparatus of claim 6 wherein said base member further includes a connector portion, a plurality of conductor paths mounted on the underside of said base member, with individual ones of said conductive paths connected at a first end to individual ones of said contact members, the second end of each of said conductor paths terminating at said connector portion, and a common conductive terminal positioned on the upper side of said base member along said connector portion.