Thin keyboard switch assembly with hinged actuator mechanism

Disclosed are keyswitches and a keyboard assembly comprising a sheet member having a plurality of key faces fixed thereon in a conventional keyboard arrangement, a plurality of cutouts in the sheet member partially surrounding each key face, and a plurality of living hinges in the sheet member at one side of each key face, whereby the key face may be depressed, causing the key face to pivot about the living hinges to operate a corresponding set of electrical contacts, indicating operation of the key. A conventional rubber spring may transmit the pivot motion of the key face to the electrical contacts.

TECHNICAL FIELD 
This invention relates to keyboards, and more particularly keyboards 
optimized for use with portable data processors. 
BACKGROUND OF THE INVENTION 
The miniaturization of data processing equipment for portability and ease 
of use is becoming increasingly important. The limiting factor for 
reducing the size of portable data processing equipment is generally the 
keyboard which requires sufficient space for the keys and for the 
extensive mechanics to convert keystrokes to electrical connections which 
indicate operation of the keys. The keys are limited in their horizontal 
size and spacing by the size of an average operator's fingers and hands. 
Thus, it is desirable to reduce the vertical dimension, or "thickness", of 
the keyboard as much as possible. A typical portable data processor, or 
"portable personal computer" or "personal digital assistant", has a 
keyboard panel and a display panel, and the data processor is incorporated 
within one of the panels. The two panels are then folded together so that 
the bottom of the keyboard panel and the back of the display panel form an 
outer case for the folded unit. By reducing the thickness of the keyboard, 
the thickness of the overall folded unit may also be reduced, making the 
folded portable data processing unit easier to handle and to carry. 
Prior U.S. Pat. No. 5,457,453, Chiu et al., unassigned, illustrates a 
keyboard having reduced thickness when folded, by moving otherwise 
conventional plunger keys to depressed positions when folding is to occur. 
Prior U.S. Pat. No. 5,280,147, Mochizuki et al., assigned to Brother Kogyo 
Kabushiki Kaisha, reduces the thickness of the keyboard by the use of 
scissors-like pivotally connected support levers with pivot connections at 
one end of each lever to respectively the base and the key, and sliding 
pivot connections at the opposite ends. A conventional nonlinear rubber 
spring or "dome" is used to transmit the keystroke to electrical contacts 
to make the connection, indicating operation of the key. 
It is desirable to reduce the height of the keyboard even further as well 
as to reduce the number of parts and to provide an easily assembled 
keyboard. 
SUMMARY OF THE INVENTION 
Disclosed are keyswitches and a thin keyboard assembly comprising a sheet 
member having a plurality of key faces fixed thereon in a conventional 
keyboard arrangement, a plurality of cutouts in the sheet member partially 
surrounding each key face, and a plurality of living hinges in the sheet 
member at one side of each key face, whereby the key face may be 
depressed, causing the key face to pivot about the living hinges to 
operate a corresponding set of electrical contacts, indicating operation 
of the key. A conventional rubber spring may transmit the pivot motion of 
the key face to the electrical contacts. 
Two embodiments are given, one comprising a planar sheet with a single 
living hinge at one side of each key, whereby depression of the key face 
causes the key face to pivot downward about the living hinge. The other 
embodiment comprises two living hinges at one side of each key, allowing 
the key face to remain level while the pivoting about both hinges, which 
key requires a lower force to be operated. 
The thin keyswitches and thin keyboard assembly of the present invention 
advantageously forms a portable data processing unit, and is applicable to 
other uses, such a a keyboard on the top face of a desk similar to a "desk 
blotter". 
For a fuller understanding of the present invention, reference should be 
made to the following detailed description taken in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Incorporation by Reference 
Keyboards are essential input devices for many applications, including for 
personal computers. As described above, such personal computers are often 
designed to be transportable and have been occupying less cubic volume 
over time. An example of such a portable personal computer is described in 
coassigned U.S. Pat. No. 5,198,991, incorporated by reference herein for 
the purpose of describing the computer per se and the connections between 
the computer and a folding keyboard, and such description will not be 
repeated here. 
Preferred Embodiments 
Referring to FIG. 1, a keyboard assembly 10 of the present invention is 
comprised of a plurality of key faces 11 arranged in rows according to the 
conventional "QWERTY" format. A face plate 12 covers the spaces of the 
keyboard assembly between the key faces. Electrical lines 14 and 15 extend 
from the keyboard assembly for connection to a data processor, as will be 
described. 
FIG. 2 illustrates, in greatly expanded scale, a planar sheet 20 which 
extends under the face plate 12 of the keyboard assembly of FIG. 1. The 
planar sheet preferably comprises a plastic material having both aspects 
of flexibility and of stiffness. The preferred material is Mylar. One of 
the keyfaces 11 is affixed to and supported by the planar sheet 20. A 
cutout 22 extends partially around the keyface 11, on three sides thereof. 
Each end, or terminus, of the cutout 22 may be squared off, or, 
preferably, comprises a rounded terminus 23 and terminus 24. The termini 
of the ends of the cutout are connected by a living hinge 26, forming a 
center section 28 of the planar sheet. Thus, depression of the keyface 11 
causes the keyface and center section 28 to pivot downward, rotating about 
the living hinge 26. The living hinge is a natural consequence of the 
positioning of the termini 23 and 24, but alternatively may be etched or 
cut into the planar sheet 20. 
FIGS. 3 and 4 comprise respectively front and side views, in greatly 
expanded scale, of a keyswitch assembly of one of the keyfaces 11 of 
keyboard assembly 10 of FIG. 1. FIG. 3 illustrates the keyface 11 in the 
quiescent position, and FIG. 4 illustrates the keyface 11 in the 
depressed, operated position. 
Face plate 12 overlays the planar sheet 20 and center section 28 of the 
planar sheet supports keyface 11, which is affixed thereto, preferably by 
cementing. A conventional rubber spring 30, often called a "dome", is 
located between the center section 28 of the planar sheet and a set of 
electrical contact members comprising common sheets 32, 33 and 34. Common 
sheet 32 comprises an uppermost contact member having electrical leads on 
the bottom side thereof, which connect to lines 15 in FIG. 1. Common sheet 
32 is made of an insulating material, preferably also Mylar, and is 
conventionally used in portable data processors. Common sheet 33 comprises 
an insulating member having openings 38 therein corresponding to the 
keyfaces 11. Common sheet 33 is also conventionally used in portable data 
processors and is preferably made of Mylar. Common sheet 34 is similar to 
common sheet 32 and comprises a lowermost contact member having electrical 
leads on the top side thereof, which connect to lines 14 in FIG. 1. An 
electrical lead 80 of common sheet 32 and an electrical lead 81 of common 
sheet 34 overlie one another at the location of opening 38 in common sheet 
33, and are normally separated as shown in FIG. 3. 
Rubber spring 30 is conventionally made of rubber and is positioned under 
keyface 11 and directly over opening 38. The rubber spring may be 
individually provided and positioned on top of common sheet 32. In the 
present invention the rubber springs are preferably positioned on a common 
sheet 40 and preferably affixed thereto by cementing. The common sheet may 
be made of Mylar. Alternatively, the common sheet 40 and all of the rubber 
springs may comprise a single rubber manufacture. 
Rubber spring 30 has a center probe 41 extending downward from the top of 
the spring. The sheet 40 has suitable holes therethrough for the center 
probe 41 to enter upon depression of keyface 11. The probe 41 transmits 
vertical force from the keyface 11 and center section 28 of the planar 
sheet 20 to uppermost common sheet 32 as illustrated in FIG. 4. 
The transmitted force by center probe 41 of rubber spring 30 causes 
uppermost common sheet 32 to be pushed into the hole 38 in insulating 
common sheet 33 into contact with the lowermost common sheet 34. The 
electrical lead 80 on the bottom of uppermost common sheet 32 is thereby 
pressed into contact with the electrical lead 81 on the top of lowermost 
common sheet 34. This contact creates a connection between one of the 
lines 15 and one of the lines 14 in FIG. 1, which signals the operation of 
the depressed keyface 11. 
Still referring to FIGS. 3 and 4, a base plate 45 forms the bottom support 
structure for the keyboard, and a spacer 46 may be provided to support the 
planar sheet 20. Cavity 47 in the spacer 46 allows placement of the rubber 
spring 30 and provides an opening for the depression of keyface 11. 
The resultant sandwich structure of face plate 12, planar sheet 20, spacer 
46, optional sheet 40, electrical contact member common sheets 32, 33, 34, 
and base plate 45 forms a solid, strong keyboard. 
Referring back to FIG. 1, the base plate of the keyboard and face plate 12 
are connected together about the periphery of the keyboard as shown by 
edges 50 and 51. The edges further stiffen the keyboard sandwich, and also 
protect the outer edges of the sheets between the base plate and face 
plate. Alternatively, the face plate 12 and the base plate 45 (FIGS. 3 and 
4) may be made of very stiff material, as may the edges 50 and 51 
surrounding the keyboard 10, allowing spacer 46 to be omitted. In that 
circumstance, the exterior edges and plates provide the structural 
strength of the keyboard 10, and may be provided with spacing struts at 
suitable points to provide additional strength. The planar sheet 20 is 
then supported by being attached, preferably by cementing, to the 
underside of face plate 12. 
Alternative springs may be used in place of rubber springs 30. The rubber 
springs or domes have proven advantageous from the standpoints of 
commercial availability and cost. 
Referring to FIG. 5, keyboard 10 is shown with an alternative (of many 
alternatives) layout of keys 11. The keyboard forms the bottom panel of a 
portable data processor, with a display 60 in a top panel 61. A data 
processor 62 may be provided either in the top panel 61 (the data 
processor is shown therein in phantom), or in an opening in the interior 
of keyboard 10. See the 1991 patent for a detailed description of the 
interconnection. Referring to FIG. 1, the lines 14 and 15 are arranged for 
positioning of the data processor in the top panel. The specific 
arrangement of the electrical connections between the keyboard 10, a data 
processor and a display is described in the '991 patent, incorporated by 
reference. In the alternative, the data processor may be in the bottom 
panel and lines from the electrical contact members would instead be 
connected to the data processor within the keyboard and other lines 
provided to connect the data processor to the display 60. 
FIG. 5 illustrates the portable data processor unfolded with the display 
panel in the generally upright position. The display panel 61 folds over 
keyboard 10 to provide a protected, closed unit with the base plate 45 of 
the keyboard and the back cover of the display panel forming a protective 
case. 
The very thin vertical dimension of the keyboard 11 allows the folded 
portable data processor to comprise a small total thickness as well. 
FIGS. 6, 7 and 8 illustrate, in greatly expanded scale, an alternative 
sheet member and keyswitch arrangement which requires a substantially 
reduced actuation force. The actuation force for the keyswitch arrangement 
of FIGS. 2-4 is approximately 80 grams, whereas the arrangement of FIGS. 
6-8 is approximately 60 grams. The smaller actuation force is the 
preferred embodiment of the invention for a "light touch" keyboard. 
Referring to FIGS. 6-8, the sheet member 70 extends under the spacer 46 of 
the keyboard assembly of FIG. 1. The planar sheet 70 is the same material 
as planar sheet 20, preferably comprising a plastic material having both 
aspects of flexibility and of stiffness, such as Mylar. One of the 
keyfaces 11 is affixed to and supported by the planar sheet 70. A cutout 
72 extends partially around the keyface 11, on three sides thereof, and 
forms a first living hinge 73. The cutout 72 continues inward, towards the 
center of the key 11 to form terminus 75 and terminus 76. The termini of 
the ends of the cutout are connected by a second living hinge 77, under 
keyface 11. The cutout 72 thereby forms a center section 28 of the planar 
sheet and two living hinges 73 and 77. Thus, depression of the keyface 11 
causes the keyface and center section 78 to stay level and pivot about 
living hinges 73 and 77, moving forward slightly, to move from the 
quiescent, unactuated position of FIG. 7 to the depressed, actuated 
position of FIG. 8. 
The living hinges 73 and 77 are a natural consequence of the positioning of 
the cutout 72 and the termini 75 and 76, but alternatively may be etched 
or cut into the planar sheet 70. 
The operation of the keyswitch illustrated in FIG. 8 is identical to the 
operation of the keyswitch illustrated in FIG. 4, described above. 
While the preferred embodiments of the present invention have been 
illustrated in detail, it should be apparent that modifications and 
adaptations to those embodiments may occur to one skilled in the art 
without departing from the scope of the present invention as set forth in 
the following claims.