CA2186789C - Ergonomic computer keyboard (and key) - Google Patents

Abstract

A computer keyboard having membrane switches activated by finger touch keys supported by an upper resilient layer of the membrane circuit board. The keys have a rigid projection fixedly secured to the finger touch part of the key. The key is depressable against the resiliency of the upper layer to make circuit contact.
The key is guided during movement and has a short travel distance as well as very light touch for circuit activation. The keyboard addresses the problem of keyboard related repetitive strain injuries (RSI's) and other disabilities requiring a "feather light touch" in a computer keyboard.

Description

ERGONOMIC COMPUTER KEYBOARD (AND KEY) This invention relates to computer fingerboards and more particularly to an improved key construction that reduces the travel distance, provides lighter touch and reduces manufacturing costs. Keys of the present invention are primarily intended far ergonomic keyboards, palmtops and Laptops. The light touch and short travel distance address the problem of keyboard related repetitive strain injuries (RSI's). The travel distance allows for a thinner design of notebooks, palmtops and portable ergonomic keyboards. The invention also has applications regarding adaptive and alternative {AAC) computer input devices for people with disabilities.
DESCRIPTION OF THE PRIOR ART
Keyboard related repetitive strain injuries (RSI's) are among the top causes of Workman's Compensation claims in North America. Consequently, ergonomics is one of the fastest growing aspects of the computer industry. Some feel that, with the advent of voice recognition, the problem of RSI's will soon become a thing of the past. However, many speech pathologists disagree with this vision. There are already reports documenting voice injuries related to voice recognitian data input. In fact, the voice may be a more volatile stress area than the carpal tunnel or elbow.
Therefore the computer industry must continue to provide ergonomic keyboard alternatives to RSI sufferers for perhaps some time to come. Many ergonomic keyboards presently in use deal with the important issue of hand positioning but they fail to address the critical issue of key resistance to travel and/or key distance of travel. For this reason thousands of RSI sufferers cannot use these devices.
The present is directed to this serious failing of curren~k ergonomic keyboards.
In the known membrane technology there are membrane key switches, membrane touch activated switches and key switches. In the conventional membrane key switch there is a resilient biasing member as well as the "spring effect" of the membrane mechanism. This combined resistance requires more force than many RSI suffers can endure. For an example of a membrane key switch, reference may be had to USP 4,515,998 issued to Harper and entitled "Full Travel Keyboard."' Touch activated membrane switches require less force than membrane key switches but the force of the strike is distributed over the entire surface of the finger (contact point) which is about 1.5 cm. This wide distribution of force translates into more resistance than many RSI sufferers can tolerate during long hours of data input. For an example of a known touch membrane switch, reference may be had to USP 5,0~2,07T issued Cfec. 10, 1 891 to Harold Klein entitled "Monolithic Membrane Switch".
A push button of a notebook computer key, as seen in USP 5,145,058 issued Sept. 8, '92 to Sam San Lee entitled "Notebook computer Key", has a plate portion, a hook projection extending downward from the plate portion and having a distal outward hook end, and a conductive member spaced vertically downward from the plate portion The hook projection extends into an upright hollow confining wall of a socket member. The top end of the socket member is provided with an inwardly extending peripheral flange to hinder movement of the distal hook end out of the receiving space to prevent detachment of the push button from the socket member.
A circuit board is provided on a lower end of the socket member. An upright hollow guide projection extends from the circuit board and into the hollow confining wall of the socket member. The conductive member is disposed inside the guide projection. A resilient biasing member has a lower tubular section, an upper tubular section wider than the tower tubular section wider than the lower tubular section and supporting the plate portion of the push button, and a gradually expanding inclined section connecting the lower and upper tubular sections. The biasing member biases the conductive member away from the circuit board.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a key and a keyboard incorporating the same in which each key has minimum resistance to movement and a short travel distance, thereby requiring a shorter distance for the finger to travel, and also a keyboard which is simpler and less expensive to produce.
Another object is to provide a key with reduced height thus allowing for easy transport, a thinner palmtop, laptop (or ergonomic computer keyboard) design while maintaining the present "look and feel°° of conventional keys.

A key of the present invention has "feather fight touch" and, as such, will not be desirable to all keyboardists. However, for many RSI suffers (or potential RSI
sufferers) and disabled persons who must have law resistance and minimal finger movement, a key of the present invention provides an ideal solution.
A key of the present invention is essentially the same as a conventional membrane key switch but differs therefrom by eliminaking the resilient biasing member that returns the finger touch part of the key to it's raised position.
In essence, the key of the present invention comprises a rigid finger touch movable part having a downwardly projecting part that rests on and remains in contact with the protective layer of a membrane switch and a guide for said rigid part. The projection on the rigid key part thus rests on the protective layer while the key is not actuated and when the key is pressed, circuit contact occurs. The insulating material and or protective layer of the membrane switch is the only source of resilience during key activation. This substantially reduces the resistance to movement, reduces the key height and the distance that the key travels downward during key activation. Therefore membrane key switch of the present invention may for example have a resistance of less than 50 gms., which is 1/5th that of conventional key switches. The "look and feel" of a conventional key switch is maintained.
The reason that the key of the present invention has a lighter touch than that of membrane touch switches is that the force during key strike is distributed over the area of the end of the downward projection that engages the upper deformable layer of the membrane. This area of contact atong with the characteristics of the cover and resilient layer can be predetermined to give tt~e desired resistance. The reason the key of the present invention it has a lighter touch than conventional key switches is that it's only source of resilience is from the membrane switching array.
It contains no resilient biasing member. This is of extreme significance to the RSI
sufferer and those requiring a °°feather light touch."
BRIEF DESCRIPTION OF TIME DRAWINGS
The invention is illustrated by way of example with reference to the accompanying drawings, wherein:
FIG. 1 is a sectional view of a prior art finger touch membrane switch activated position;
FIG. 2 is a sectional view of a membrane key switch of the present invention;
FIG. 3 is an exploded part sectional view of a membrane key switch of the present invention;
FIG. 4 is a sectional view of the key membrane switch of the present invention in a switch activated position (key depressed);
FIG. 5 is a sectional view on a larger scale of the membrane section of the switch and a portion of the key projection contact therewith;
FIG. 6 is a bottom view of the key button;
FIG. 7 is a side view of the key button;
FIG. 8 is a top view of the socket; and FIG. 9 is an oblique view of the socket DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Illustrated in FiG. 1 a typical membrane switch and particularly the ane disclosed in the aforementioned USF~ b,0'~2,07~. The keyboard assembly is completed by an array of mechanical key elements associated with and for the purpose of actuating each of the individual key locations in the membrane array.
The key elements deliver actuating farce to the key locations or key sites of the membrane keyboard, and the key elements include apparatus for precise displacement of a key cap prior to the making of electrical contact with the membrane array to provide the operator of the switch and keyboard with the sensation of pretravel. The key elements also include a geometrically defined configuration for compressing the elastomeric material on the upper portion of the membrane array both before and after closing the membrane switch, so that compression of the elastomeric material both contributes to the sense of pretravel and generates the overtravel perceived by the keyboard operator.
Keyboards made in accordance with the present invention have switching life and reliability equivalent to thane found in capacit~ue type arrays, while at the same time having significantly reduced cost for the assembled keyboard and requiring fewer plastic parts and springs than in prior art assemblies of this type.
Also, these advantages of the present invention are accomplished in a configuration in which the human factor variable requirements are met.
The elastomeric layer on the membrane switch array acts as a spring element both to contribute to pretravel and to distribute the closure force from the key stem uniformly over the entire area of the membrane switch (i.e., the area defined at each opening in the spacer or separator layer). The eiastomeric layer also contributes the sensation of overtravel and it can also provide for quiet, "clack" free operation when the actuator/elastomeric interface is properly defined. The membrane key switch itself contributes a spring characteristic in that wt moves from the separated and open circuit configuration to a mechanically and electrically closed state in response to the application and imposition of a specifically defined actuating force, thus accomplishing control of the actuating or "'fire" point.
A protective layer 50 is bonded to the upper face of layer 12. Referring to FIG.
there is illustrated an embodiment of the computer key is shown to comprise of a push button 30, a socket member, 4~, and a circuit board 70. The membrane circuit board may be as illustrated in FIG.1 and/or other known construction.
The push button 30 has a slightly concave plate potion with a dawnwardly extending and outwardly inclining peripheral flange 31 on three sides and a downwardly extending peripheral flange 32 an the fourth side (see FIG. 6). A
tubular projection 33 extends downward from the underside of the plate portion of the plate portion 30. A pair of spaced hook projections 34 extend downward by tubular projection 33. Each hook projection 34 is provided with a distal outward hook end 35.
The socket member 40 is in a plate 60 that overlies the membrane circuit board.
The socket 40 is defined by a wall 61 projecting upwardly from the plate 60 around an opening 62. The wall 61 has an extending peripheral flange 63 that is engageable with hook ends 35 of the projections 34 on the key or push button.
This prevents detachment of the push button from the socket member 40.
When the switch is at an at rest position (not actuated), the tubular projection 33 rests on theprotectivelayer 50 of the monolithic circuit board 18.
A membrane circuit board 70 is shown in an enlarged scale in FIGS. 1 & 5 and includes a bottom stiffener layer 8, a passive membrane switch circuit layer thereon, an insulating spacer or separator 14 on the passive membrane layer 10 and an active membrane layer switch circuit 12 on the other side of the spacer 38.
Both the passive and active membrane layers 10, 12 have electrical conductors thereon (formed by printed circuit techniques] arranged in a geometrical pattern and cooperating with the holes 38 in the separator layer 14 to define an array of unique switch and circuit locations. The application of an appropriate force to push button 30 causes via projection 33 the active layer and its particular switch component to make physical and electrical contact through the appropriate hole 38 in the spacer 14 with the circuit pattern on the fixed or passive layer 10 of the membrane.

A layer of elastomeric material 50 is positioned on and attached to the upper surface of the active layer 12 of the membrane switch array. The elastomeric material can be chosen to provide a suitable compressibility factor or example it can, if desired, provide switch contact with a finger force of less than 50 gms. on the key 30. The elastomeric material 50 andlor layer 12 having the printed circuit on the underside thereof must have sufficient stiffness to support the weight of the unactuated push button 30 so that the switching array would not be activated when the push button is at rest. The contact area of projection 33, the size of hole 38, the thickness of layer 14, the resiliency of layers 50, 12 and/or 14 can be varied and co-related to provide a selected desired soft touch and travel distance for the key.
The hook engagement between the hook projections 35 and the socket member 40 facilitates the assembly and disassembly of the push button 30 from the socket member 40.
There has been described herein an ergonomic membrane key switch that does not have separate resilient biasing member as for example the aforementioned USP

5,145,058 and therefore requires significantly less activating force than a conventional membrane key switch of the type for example illustrated in aforementioned USP 5,072,077 because in the latter activating force is distributed over a wider contact surface. In the present invention the moveable key is rigid and in physical contact with the membrane circuit board. The key is guided in its movement and snap fits into the socket.

Claims (9)

1. A computer keyboard comprising:
(a) a membrane circuit board having a resilient upper switch circuit layer, a stiff lower switch circuit layer and an insulative layer disposed therebetween, holes through said insulative layer aligned with predetermined circuit paths on said upper and lower switch circuit layers for completing predetermined circuits by physical contact of conductive material on one of said layers with conductive material on the other of said upper and lower layers;
(b) a push button key for each of respective ones of said holes, each said push button key having a downwardly extending rigid projection fixed thereto and aligned with the hole associated therewith, each said key, in a key at rest circuit open position being supported by said upper resilient layer, said keys being movable from their at rest position in a direction toward said lower layer thereby to cause physical contact of the conductive material on said respective upper and lower layers; and (c) means, on said key board, resisting movement of said keys, from their at rest position, in a direction away from said upper layer.

2. A computer keyboard as defined in claim 1 including means guiding said keys during movement of the same.

3. A computer keyboard as defined in claim 2 wherein said movement resisting and guide means includes a socket for each of respective ones of said keys.

4. A computer keyboard as defined in claims 1, 2 or 3 wherein each said push button key has a plate portion with said rigid projection extending downwardly from a central portion of an underside portion of said plate portion, a further projection extending downwardly from said plate portion at a position spaced outwardly from said rigid projection, said further projection having an outwardly directed hook for engagement with an abutment means and thereby provide said means resisting movement of said keys in a direction away said upper layer.

5. A keyboard as defined in claim 2 wherein said guide and movement resisting means include a socket member having an annular space surrounding a post means, a flange projecting inwardly into said annular space, said further projection being located in said annular space such that the outwardly directed hook thereon is engagable with said flange and thereby prevent the key from being dislodged from said socket.

6. A computer keyboard comprising:
(a) a lower circuit sheet means comprising a first sheet of insulating material with a first electrically conductive means thereon;
(b) an upper circuit sheet means overlying said lower sheet means and comprising a second resilient sheet of insulating material with a second electrically conductive means on a surface thereof facing said first electrically conductive means;
(c) spacer means disposed between said first and second circuit sheet means;
said spacer means having a plurality of openings therein permitting physically moving preselected portions of said second electrically conductive means into contact with said fast electrically conductive means for selectively completing predetermined circuits;

(d) a push button key for each of respective ones of said plurality of openings, each said push button key having a downwardly extending rigid projection fixed thereto and aligned with the opening associated therewith, each said key having the rigid projection thereof in physical contact with said upper resilient sheet, each said key being supported by said resilient sheet in an at rest open circuit position and being movable from said rest position in a direction toward said lower sheet thereby to cause said physical contact of the conductive material on said respective upper and lower sheets; and (e) means, on said key board, resisting movement of said keys, from their at rest position, in a direction away from said upper sheet.

7. A computer keyboard as defined in claim 1 including a layer of compressible elastomeric material on said upper circuit layer, said elastomeric material having a predetermined compressibility value.

8. A computer keyboard as defined in claim 7 including a thin protective layer disposed between said rigid downward projection on said push button key and the elastomeric material.

9. A computer keyboard as defined in claim 8 wherein the compressibility of said elastomeric material is such that a force of approximately 50 grams on the push button key is required to active a circuit.