Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ERGONOMIC COMPUTER KEYBOARD (AND KEY)
FIELD 4F THE INVENTION
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
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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
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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.
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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
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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
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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
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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
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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
10
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.
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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.
