U.S. patent number 3,749,859 [Application Number 05/245,577] was granted by the patent office on 1973-07-31 for keyboard switch assembly with improved hermetically sealed diaphragm contact structure.
This patent grant is currently assigned to Colorado Instruments, Inc.. Invention is credited to Tommy N. Tyler, James R. Webb, Richard C. Webb.
United States Patent |
3,749,859 |
Webb , et al. |
July 31, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
KEYBOARD SWITCH ASSEMBLY WITH IMPROVED HERMETICALLY SEALED
DIAPHRAGM CONTACT STRUCTURE
Abstract
A contact key for use in a keyboard arrangement is disclosed
wherein one contact extends through a circuit board and a second
contact comprises a curved plate or dome spring is positioned on
one side of the circuit board and is depressable so that the center
thereof can come in contact with the first contact to complete a
circuit. In one form of the invention the first contact comrpsies a
rivet while in another form it comprises a plated-through hole to
the back of the circuit board. The second contact can include a
dimple at the center thereof which comes in contact with the first
contact when the plate is depressed. A plurality of these first
contact members are placed in a circuit board and the second
contacts can be supported by a conductive support, such as a shim
or plated support having apertures corresponding to the position of
the first contacts. If the contact support is in the form of the
shim, it can comprise a plurality of sections interconnected by
frangible tabs which are broken during assembly to separate the
sections, the tabs being bent through holes in the circuit board
and crimped against the back side to hold the shim in place and to
provide connections for the respective sections to appropriate
circuitry. In an embodiment having a plated contact support, the
support can be provided with one or more raised bosses to support
the contact plate above the first contact.
Inventors: |
Webb; Richard C. (Boulder,
CO), Webb; James R. (Boulder, CO), Tyler; Tommy N.
(Broomfield, CO) |
Assignee: |
Colorado Instruments, Inc.
(Broomfield, CO)
|
Family
ID: |
22927237 |
Appl.
No.: |
05/245,577 |
Filed: |
April 19, 1972 |
Current U.S.
Class: |
200/5R; 200/5A;
200/275; 200/302.2; 200/516 |
Current CPC
Class: |
B41J
5/16 (20130101); B41J 5/12 (20130101); H01H
13/7006 (20130101); H01H 2207/014 (20130101) |
Current International
Class: |
B41J
5/00 (20060101); B41J 5/16 (20060101); B41J
5/12 (20060101); H01H 13/70 (20060101); H01h
005/04 (); H01h 013/52 () |
Field of
Search: |
;200/159R,159B,166BH,167R,168G,5R,5A,16A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Scott; J. R.
Claims
What is claimed is:
1. An electrical normally-open contact switch comprising:
a first electrical contact;
a second contact formed as a curved resilient plate of electrically
conductive material spaced from said first contact in a normally
open position and having a peripheral edge along at least a portion
of which said second contact is supported;
a circuit board in which said first contact is mounted and having
said second contact supported on a first side thereof, said first
contact extending through said circuit board and being electrically
connected to a circuit on a second side of said circuit board
opposite said first side; and
means for connecting said first and second contacts in an
electrical circuit which includes an electrically conductive
support plated on said first side of said circuit board for
supporting said second contact, said switch completing said circuit
upon deflection of the center of said plate from said normally open
position to a closed position against said first contact when
pressure is exerted against said center, said center snapping back
to said normally open position upon removal of said pressure.
2. An electrical normally-open contact switch comprising:
a first electrical contact;
a second contact formed as a curved resilient plate of electrically
conductive material spaced from said first contact in a
normally-open position and having a peripheral edge along at least
a portion of which said second contact is supported;
a circuit board in which said first contact is mounted and having
said second contact supported on a first side thereof, said first
contact extending through said circuit board and being electrically
connected to a circuit on a second side of said circuit board
opposite said first side;
means for connecting said first and second contacts in an
electrical circuit which includes an electrically conductive
support plated on said first side of said circuit board for
supporting said second contact, said switch completing said circuit
upon deflection of the center of said plate from said normally open
position to a closed position against said first contact when
pressure is exerted against said center, said center snapping back
to said normally open position upon removal of said pressure;
and
at least one boss projecting from said plated support, said boss
supporting a portion of said peripheral edge above said plated
support.
3. An electrical normally-open contact switch comprising:
a first electrical contact;
a second contact formed as a curved resilient plate of electrically
conductive material spaced from said first contact in a normally
open position and having a peripheral edge along at least a portion
of which said second contact is supported;
a circuit board in which said first contact is mounted and having
said second contact supported on a first side thereof, said first
contact extending through said circuit board and being electrically
connected to a circuit on a second side of said circuit board
opposite said first side;
means for connecting said first and second contacts in an
electrical circuit which includes an electrically conductive
support plated on said first side of said circuit board for
supporting said second contact, said switch completing said circuit
upon deflection of the center of said plate from said normally open
position to a closed position against said first contact when
pressure is exerted against said center, said center snapping back
to said normally open position upon removal of said pressure;
and
three bosses projecting from said plated support, said bosses
supporting said peripheral edge above said plated support.
4. A keyboard having a plurality of normally open contact switches,
said keyboard comprising:
a circuit board having first and second sides;
a plurality of spaced first electrical contacts, each contact
extending through said circuit board from said first side of said
circuit board to said second side thereof and being electrically
connected to selective circuits on said second side;
a plurality of second contacts, each formed as a curved resilient
plate of electrically conductive material spaced from said first
contact in a normally open position and having a peripheral edge
along at least a portion of which said second contact is
supported;
a contact support on said first side of said circuit board spaced
from each of said first contacts and supporting said second
contacts along at least a portion of their peripheral edges, said
contact support being connectable to a potential, each of said
switches completing a circuit upon deflection of the center of said
plate from said normally open position to a closed position against
a corresponding first contact when pressure is exerted against said
center, said center snapping back to said normally open position
upon removal of said pressure;
an insulative element covering said first side of said circuit
board to hold said second contacts in position with respect to said
first contacts and to keep foreign material out of said contacts,
said element including a layer of thin flexible material completely
covering said second contacts;
a plurality of depressible keys; and
means for positioning said keys with one of said keys adjacent each
of said second contacts with said layer of flexible material
therebetween, each of said keys being selectively depressible to
deflect a respective plate from said normally open position to a
closed position.
5. A keyboard, as claimed in claim 4, wherein said contact support
includes:
electrically conductive material plated to said first side of said
circuit board and surrounding each of said first contacts for
supporting said second contacts.
6. A keyboard, as claimed in claim 4, wherein said contact support
includes:
a conductive shim having perforations corresponding to the
positions of said first contacts so that said shim surrounds each
of said first contacts for supporting said second contacts.
7. A keyboard, as claimed in claim 6, wherein said shim
comprises:
at least two sections interconnected by frangible tabs which can be
fractured during assembly and bent through openings in said circuit
board for connecting said respective sections to selective circuits
on said second side of said circuit board.
8. A keyboard, as claimed in claim 4, wherein:
each of said plates has a projection at said center thereof
extending toward said first contact and adapted to engage said
first contact upon deflection of each of said plates.
9. A keyboard, as claimed in claim 4, wherein:
each of said first contacts is a rivet.
10. A keyboard, as claimed in claim 4, wherein:
each of said first contacts is a plated hole through said circuit
board from said first side of said second side.
11. A keyboard, as claimed in claim 4, wherein said insulative
element further includes:
spacer means positioned about the periphery of said second contacts
to hold said second contacts so that the centers thereof are in
substantial alignment with said first contacts.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electric signal device, and more
particularly to a contact switch for use in a keyboard arrangement,
including alpha-numeric keyboard arrangements, to cause the
generation of binary signals that are suitable for direct entry
into digital data transmission systems, displays and/or
computers.
2. Description of the Prior Art
With the advent of the widespread use of electronic data processing
systems, commonly known as computers, there is a need for a
simpler, smaller, low cost and generally more satisfactory keyboard
data entry system since keyboards form the machine/man interface in
the data processing system. That is, the operator of the machine
depresses keys on the keyboard to form binary or coded binary
signals which are fed into the data processing machine. Currently,
such interface equipment is formed by such devices as teletype
machines, card keypunch units, electric typewriters, adding
machines, and the like. However, these devices are not entirely
satisfactory for various reasons.
The most common prior art apparatus for generating data from an
array of keys is an electric switch that closes when a key is
depressed. This is, each time the key in the keyboard array is
depressed an associated switch closes. Closure of the switch causes
a coded signal to be generated which uniquely defines the key that
was depressed. The data bit pattern thus generated is fed into the
data processing system. While apparatus of this nature is generally
satisfactory, there are several disadvantages, the complexity of
the keys and cost thereof being one significant factor.
It will be appreciated by those who have used them that prior art
keyboards generally have several other undesirable features. For
example, many keyboards are thick and not compact and have a
relatively high profile, thus making them inconvenient and tiresome
to reach. Furthermore, a relatively large keyboard increases the
size of the data processing system beyond what is necessary for
miniaturized circuitry now available. In addition, the action of
the keys is frequently less rapid than desirable. Furthermore,
simultaneous key depressions may not be detectable. Often the keys
are rugged and not sealed so as to be immune from dust and dirt.
Some keyboard systems are adversely subject to changes in
temperature. Furthermore, many systems use more than a minimal
amount of power, making them unuseful in battery operated
environments.
SUMMARY OF THE INVENTION
In accordance with the present invention, an electrical normally
open contact switch is provided which includes a first electrical
contact, and a second contact formed as a resilient curved plate of
electrically conductive material spaced from the first contact in a
normally opened position and having a peripheral edge along at
least a portion of which the second contact is supported and
further includes means for connecting the first and second contacts
in an electrical circuit, the switch completing the circuit upon
deflection of the center of the plate from the normally open
position to the closed position against the first contact when
pressure is exerted against the center, the center snapping back to
the normally open position upon removal of the pressure.
More particularly, the switch may be provided in a keyboard array
and be mounted on a circuit board which has a plurality of spaced
first electrical contacts which extend through the circuit board
from a first side of the circuit board to a second side thereof and
are electrically connected to selective circuits on the second
side. A plurality of second contacts each formed as a curved
resilient plate or dome spring are mounted on a contact support on
the first side of the circuit board which contact support surrounds
each of the first contacts and has an opening corresponding to the
position of the first contact. The contact support is formed, in
one embodiment, in separate sections interconnected by frangible
tabs which are broken during assembly and crimped through
appropriate holes in the circuit board and crimped against the
other side. The selective sections can be connected, as by
soldering to selective circuitry on the other side and each section
is connectable to a separate potential to provide different circuit
capabilities with different keys. It is understood that each switch
completes a circuit upon deflection of the center of the plate from
the normally open position to the closed position against the
corresponding first contact when pressure is exerted against the
center, the center snapping back to the normally open position upon
removal of the pressure. In another embodiment, the contact support
is formed by electroplating the keyboard and includes a layer of
flexible material extending over the side of the circuit board on
which the dome springs are supported, completely covering that side
of the circuit board to keep moisture and foreign material out of
the contacts but permitting deflection of the plate or dome spring
contact. In addition, a plurality of depressable keys are
positioned with one key above each of the second contacts, which
keys are held in position with a grid or frame connected to the
circuit board.
In one form of the invention the first contact is formed by a rivet
extending through the circuit board from the first side to the
second side and connected to selective circuits on the second side
whereas in an alternative embodiment the first contact is formed as
a plated through hole in the circuit board which plated through
hole is also connected to selective circuits on the second side of
the circuit board.
The contact support in one form of the invention is formed as a
shim which is made up of separate sections connected together by
frangible tabs which tabs may be broken during assembly so that
they may be forced through holes in the circuit board and clenched
to the back side to be soldered or otherwise connected into the
circuits on the second side of the circuit board. This arrangement
permits connection of different potentials to different sections of
the contact support so that different keys may be used to perform
different functions.
In an alternative embodiment the contact support is formed, as by
electroplating, as a plated support on the circuit board which has
a plurality of openings corresponding to the position of the
respective first contacts and includes in one embodiment one or
more bosses spaced around each opening for supporting the second
contact or dome spring above the surface of the first contact.
These bosses can be formed by means of an embossing punch which
forms the bosses in the plated contact support after it is formed
on the circuit board.
From the foregoing, it can be seen that a contact switch made in
accordance with this invention is of simple and economic
construction and will be reliable in operation. Additional
advantages will become apparent from the description which follows,
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded, fragmentary, perspective view of a keyboard
which illustrates a key comprising one form of the invention;
FIG. 2 is an enlarged vertical section, taken along line 2--2 of
FIG. 1, showing an assembled key in normally open position;
FIG. 3 is an exploded, perspective view of a circuit board and
contact support showing how the contact support is positioned on
the circuit board and attached thereto;
FIG. 4 is an exploded, perspective view, similar to FIG. 1, but
showing an alternative keyboard for a mini-computer;
FIG. 5 is an enlarged vertical section taken along line 5--5 of
FIG. 4, showing an assembled key in normally open position;
FIG. 6 is a vertical section, similar to FIG. 5, but showing an
alternative plate contact;
FIG. 7 is a fragmentary, perspective view of an alternative contact
support having raised bosses;
FIG. 8 is a fragmentary, vertical section, showing the method of
making the raised bosses of FIG. 7;
FIG. 9 is a fragmentary exploded perspective view showing a plate
contact positioned on a still further alternative contact support
having a single raised boss; and
FIG. 10 is a fragmentary vertical section taken along line 10--10
of FIG. 9 showing the position of the assembled switch of FIG. 9 in
its normally open position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with this invention, the keyboard B of FIG. 1 is of
the type used for desk calculators or computer keyboards wherein
numeric or alpha-numeric function controls are necessary. A series
of keys K are mounted as shown on a conventional glass epoxy
circuit board 2 which has a printed circuit on the lower side
thereof. At the center of each key position a first contact 4
extends through the circuit board from the top side to the lower
side where it is connected, as by soldering, to a circuit (not
shown) as by a lead as shown in FIG. 2. Conveniently, the contact 4
may take the form of a rivet as shown which extends about 0.013
inches above the circuit board.
A shim 7, which has a thickness of about 0.010 inches, extends over
substantially the entire upper surface of the circuit board and is
provided with a series of openings or perforations 8 which are
adapted to be received over the respective contacts 4.
Conveniently, during assembly frangible tabs 9 can be broken by a
tool (not shown) which separates shim 7 into separate segments and
pushes the ends of tabs 9 through holes punched in circuit board 2
and crimps them against the lower side thereof so that the segments
can be soldered or connected to circuitry on the lower side of the
circuit board. Similarly, tabs 9' can be bent through holes in the
circuit board to make connections to the other side thereof.
Each switch K includes a second contact 10 in the form of a plate
or curved dome spring which in FIG. 1 is illustrated as being
generally triangular shaped with depending legs. This dome spring
is more fully described in commonly assigned co-pending U. S.
application Ser. No. 175,941 to Wray C. Hansen, filed Aug. 30,
1971. Spring 10 can be deflected downwardly into contact with
contact 4 by depressing the key K associated therewith. The key
includes a cylinder 12 which is conveniently made of polyurethane
and rests on top of spring 10 and is surrounded by a coil spring
14. The upper end of coil spring 14 is received in an actuator 16
which has a central recess 18 therefore. The actuator includes a
body 20 with an upwardly projecting neck 22, the body having a
plurality of semi-cylindrical legs 24 spaced therearound. The
actuator is received in a generally cubic housing 26 having a body
28 with downwardly projecting legs 30 thereon which are adapted to
be received in openings (not shown) in circuit board 2. The housing
includes a lid 32 which has an open cylindrical collar 34 through
which neck 22 of actuator 16 is adapted to project. The actuator is
slidably mounted within body 28 whereby legs 24 are received in
semi-cylindrical recesses 36 within the body. Conveniently, lid 32
is attached to body 28 by means of pins 38 which are received in
openings 40 on the body of the housing.
Neck 22 of actuator 16 includes an X-shaped element 42 at the upper
end thereof adapted to receive a button of key element 44. In
operation, when button 44 is depressed, it forces actuator 16
downwardly against coil spring 14 and cylinder 12 and when a
sufficient amount of pressure is applied the dome or curved spring
10 rapidly collapses bringing the center thereof into contact with
rivet 4 to complete a circuit connection. Upon release of finger
pressure on button 44, the spring 10 quickly snaps back to its
arched position over rivet 4. Advantageously, this key K is
non-teasable and provides finger touch feedback. Also, the
arrangement provides a relatively low profile and is rugged and
consumes low power and is readily manufactured at low cost.
Advantageously, the dome spring 10 is approximately 0.005 inches in
thickness and is spaced from rivet 4 approximately 0.0025 inches.
It will be further understood that body 28 may be so dimensioned as
to constrain dome 10 from lateral movement. The relative
differences in diameter of the dome and body have been exaggerated
for clarity of illustration.
An alternative keyboard B' is disclosed in FIG. 4 which has
particular application in pocket-size or mini-calculators of the
battery-operated type which can be carried in the pocket or
alternatively can be connected to a conventional power source. This
keyboard includes a circuit board 46 made of conventional materials
which has a plurality of plated-through holes 48, one of which can
be seen in FIG. 5, each of which serves as a first contact for the
switch in key K' and is connected by a lead 50 to suitable portions
of a printed circuit on the bottom side of the circuit board. A
contact support 52 is formed on the top side of circuit board 46 as
shown in FIGS. 4 and 5, as by electroplating, upon which a second
contact such as a dome spring or plate 54 is mounted as in the
previous embodiment the contacts 48 extending through holes or
perforations 53 therein. Advantageously, the plated-through holes
and the contact support can be formed at the same time to a
thickness of say 0.004 inches and a portion of the contact surface
of the plated-through hole can be etched away, such as 0.002 inches
to provide sufficient clearance for the dome spring to "snap
through" when it makes contact. In this embodiment, a spacer or
cage 56 is provided having a plurality of openings 58 corresponding
to the position of dome spring 54 and is adapted to hold the dome
spring in proper orientation with respect to the plated-through
holes 48. To protect the contacts from moisture, dirt and other
foreign matter, a thin plastic sheet 60, such as Mylar, is placed
over the spacer 56 and the dome spring 54 and conveniently has an
adhesive on the contacting side.
Above each dome spring and above sheet 60 is an actuating key, such
as key 62 which has a depending finger 63 for depressing dome
spring 54, the keys being held in position by a frame or grid 64
which extends thereover as shown in FIG. 4 and is attached to the
mini-calculator to hold the same in place.
An alternative embodiment is shown in FIG. 6 wherein a circuit
board 46' has a plated-through hole 48' therein which is connected
to selective circuits (not shown) by means of a lead 50'. A dome
spring 66 is supported on a contact support 52' and is held in
position by a spacer or cage 56', a plastic sheet 60' extending
across the spacer and the dome spring 66 to provide a sealed unit.
In this embodiment, the dome spring 66 is provided with a dimple 68
at the center thereof which provides a downwardly extending
projection to provide point contact the edge of a plated-through
hole 48' when the spring is depressed, as by finger 63' of key 62',
the latter being held in position by a frame 64'.
In the embodiments of FIGS. 5 and 6 the plated-through holes and
the contact supports are formed by electroplating, but then the top
of the plated-through hole must be etched away so that it is spaced
below the contact space a distance on the order of 0.002 inches. In
the alternative embodiments shown in FIGS. 7-10 this additional
etching procedure is not required. To avoid this, a plated support
52" which is formed on circuit board 46" is provided with a
plurality of raised bosses 70, such as three, for supporting a dome
spring 72 above a plated hole contact 48". Conveniently, these
bosses can be approximately 0.002 inches above the surface of
support 52" and thereby support dome spring 72 at a suitable height
to allow sufficient deflection of the center thereof to bring it
into contact with contact 48". The raised bosses may be formed in
the contact support 52" by positioning an embossing die 74 over the
contact support and striking the bottom of the circuit board with
an embossing punch 76, as shown in FIG. 8. Thus, the etching step
can be omitted.
A further alternative embodiment is shown in FIGS. 9 and 10 wherein
a circuit board 46'" has a contact support 52'" plated thereon
which includes a single boss 70' which boss is twice as high as
boss 70 at FIGS. 7 and 8. Thus a dome spring 72' is supported at
one edge by the contact support 52'" and at the other edge by
raised boss 70' to position dome spring 72' a sufficient distance
above plated hole 48'" which is connected to suitable circuitry, as
by welding, by means of lead 50". The dome springs 72' are held in
position by spacer or cage 56" and are covered by flexible layer
60". Each dome spring is deflected by a finger 63" on a key 62" to
make contact with plated-through hole 48'". Conveniently, as in
previous embodiments, the keys are positioned by a frame 64". With
this arrangement, it is necessary only to make one boss, and this
is advantageous because it is some times difficult to find three
equally spaced positions around a contact support which can be
engaged by the embossing punch without disturbing the printed
circuitry on the bottom side of the circuit board.
The dimensions described are exemplary only and may be varied for
particular applications as required. In this regard, a spacing
between the center contact and the dome spring of 0.010 and 0.020
inches has been found to be satisfactory.
From the foregoing, the advantages of this invention are readily
apparent. A keyboard for use with calculators is shown in one
embodiment wherein the printed circuit board has a shim with
openings surrounding contacts in the circuit board which shim is
divided into portions that are connected by frangible tabs that are
broken during assembly to attach the shim to the circuit board and
provide electrical connections thereto. In addition, a dome or
curve spring is provided above each contact which is supported by
the shim and which is depressable to deflect the center thereof
into engagement with its associated contact to complete a circuit.
The first contact is formed as a rivet in one embodiment.
In an alternative embodiment a keyboard is provided for a
mini-calculator wherein the contacts extending through the circuit
board are formed as plated-through holes which are surrounded by a
contact support on the side of the circuit board opposite the
circuit and supports curved or dome spring contacts which are
positioned by means of a spacer, the entire contact assembly being
sealed against moisture and foreign matter by means of a plastic
adhesive layer, such as Mylar, which extends across the spacer and
the dome springs. The dome springs are deflected selectively by
keys positioned thereabove within a frame. The dome spring in a
further alternative embodiment includes a dimple at the center
thereof which is engageable with the plated-through hole. In a
still further alternative embodiment the contact support is formed
with one or more bosses which support the dome spring above the
contact to avoid the necessity of etching the plated-through hole
so that in its position below the contact hole the contact support
a sufficient distance to provide suitable deflection of the dome
springs.
The invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the field and scope of this invention.
* * * * *