U.S. patent number 3,928,736 [Application Number 05/467,667] was granted by the patent office on 1975-12-23 for keyboard switch assembly having discrete helical conductors providing wiping action.
This patent grant is currently assigned to Sumlock Anita Electronics Limited. Invention is credited to James John Drage.
United States Patent |
3,928,736 |
Drage |
December 23, 1975 |
Keyboard switch assembly having discrete helical conductors
providing wiping action
Abstract
There is disclosed a keyboard in which each of the key contacts
consists of a gold-coated wire contact with each end passing
through a printed circuit board and soldered to one part of the
circuit on the underside of the board and of a gold-coated plate
contact with a base part mounted on the printed circuit board by
lugs passing through the printed circuit board and soldered to
another part of the circuit on the underside of the board and with
a part cut in helical form and so deformed in an open spiral to
form a resilient raised part directly above the wire contact. Each
of the push buttons of the keyboard is circular with diametrical
flanges extending outwardly and has a central stem which abuts the
central part of the resilient raised part of the plate contact and
an annular outer depending ring which surrounds the resilient
raised part of the plate contact. On depression, the outer part of
the spiral resilient raised part makes initial contact with the
wire contact and, after further movement, the inner parts of the
spiral resilient raised part make contact with the wire
contact.
Inventors: |
Drage; James John (Uxbridge,
EN) |
Assignee: |
Sumlock Anita Electronics
Limited (Uxbridge, EN)
|
Family
ID: |
10181029 |
Appl.
No.: |
05/467,667 |
Filed: |
May 7, 1974 |
Foreign Application Priority Data
|
|
|
|
|
May 11, 1973 [UK] |
|
|
22538/73 |
|
Current U.S.
Class: |
200/5A; 200/276;
200/275; 200/516 |
Current CPC
Class: |
H01H
13/12 (20130101); H01H 13/7006 (20130101) |
Current International
Class: |
H01H
13/70 (20060101); H01H 13/12 (20060101); H01H
013/52 (); H01H 001/06 () |
Field of
Search: |
;200/5R,5A,159R,159A,159B,276 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; James R.
Attorney, Agent or Firm: Brown; Laurence R.
Claims
What I claim is:
1. A keyboard comprising a cover plate; a plurality of push buttons
movably mounted within the cover plate; an insulating base plate
spaced from the buttons bearing a first set of longitudinally
directed fixed contacts on that side of the base plate facing said
push buttons, each contact of this set located opposite one of the
push buttons; and a plurality of contact plates, each contact plate
affixed to said base plate in a position co-operating with a
corresponding button and a corresponding one of the first set of
contacts; wherein the contact plates each comprises a strip of
electrically conducting material having at least one tag securing
the strip to the base plate and a resilient part with a free end
spaced away from said base plate to engage one said push button at
a position normally extending towards the corresponding contact of
the first set of contacts to make electrical wiping contact
therewith when the push button is moved toward said base plate; and
wherein the resilient part of the contact plate comprises an
integral part of the contact plate cut out of the contact plate
with a helical slot thereby forming a helically shaped conductor
which engages said longitudinally directed fixed contact in a
wiping action in at least two spaced positions on said helically
shaped conductor when said push button is moved toward said base
plate.
2. A keyboard according to claim 1, wherein each button has on its
under surface an annular outer depending ring which surrounds the
resilient part of the corresponding contact plate and a circular
post which is concentric with the depending ring and which is in
contact with the free end of the resilient part of the
corresponding contact plate.
Description
A BRIEF SUMMARY OF THE INVENTION
This invention has reference to keyboards intended more
particularly for use in electronic calculating machines and more
especially for use in hand-held electronic calculating
machines.
It is an object of the present invention to provide an improved
keyboard.
It is another object of the present invention to provide a keyboard
which will be of simple and robust construction yet able to be of a
suitable size for use in a hand-held electronic calculating
machine.
According to the present invention a keyboard comprises: a cover
plate, a plurality of push buttons movably mounted within the cover
plate, a base plate bearing a first set of contacts, each contact
of this set each corresponding to one of the push buttons, and a
plurality of contact plates, each contact plate co-operating with a
corresponding button and a corresponding one of the first set of
contacts; and wherein each one of the contact plates comprises a
strip of electrically conducting material having at least one
integral tag securing the strip to the base plate and a resilient
part with a free end normally extending towards the corresponding
push button but capable of being moved on depression of the push
button towards the corresponding contact of the first set of
contacts to make electrical connection therewith.
Preferably the base plate is a printed circuit board and has
electrical connections extending from each contact of the first set
of contacts and from each one of the contact plates to a connecting
contact at the side of the printed circuit.
Conveniently the resilient part of the contact plate comprises an
integral part of the contact plate cut out of the contact plate
with a helical slot .
BRIEF DESCRIPTION OF THE DRAWINGS
A keyboard in accordance with the present invention will now be
described by way of example with reference to the drawings:
FIG. 1 is a plan view of a calculating machine embodying the
keyboard;
FIG. 2A is a view taken on the line A--A in FIG. 1;
FIG. 2B is an enlarged perspective view of the button contact
assembly shown in FIG. 2A;
FIG. 3 is a view taken of the line B--B in FIG. 2; and
FIG. 4 is a plan view of the printed circuit board in the
calculating machine.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring to FIG. 1 of the drawings, there is shown a calculating
machine of the hand-held type embodying a casing (1) having windows
(2) behind which the displays are mounted. There are also shown
three control switches (3). There is also shown the outer cover
plate (4) of the keyboard. This cover plate includes 20 apertures
and each of these apertures houses a push button (5). These push
buttons are arranged in four banks of five buttons each. The
buttons relate to the numbers 0-9 and additional control buttons
relate to operative functions of the calculating machine.
Each of these buttons consists of a flat top surface on which is
imprinted the number or other designation and on the under surface
is an annular outer depending ring (5a) and a circular post (5b).
Each of the push buttons has on its underside a pair of flanges
which project outwardly in opposite directions along a diameter of
the depending ring (5a) of the button. These flanges co-operate
with complementary recesses in the housing of the cover plate to
prevent the buttons rotating in the cover plate.
The under face of the cover plate bears a plurality of upright
posts (not shown) which are screw threaded internally to receive
screws for mounting the printed circuit board to be hereinafter
described.
Referring to FIG. 2 of the drawings the calculating machine
includes batteries (6) for driving the calculating machine and also
includes an integrated circuit board (7) which includes the
calculating circuitry of the calculating machine.
Beneath the banks of push buttons (5) is arranged a base plate in
the form of a printed circuit board (8) more fully shown in FIG. 4.
This printed circuit board comprises a sheet of electrically
non-conducting material on the upper surface of which are mounted a
first set of contacts in the form of a plurality of strips (9) of
electrically conducting material set into the board. Each end of
each of the strips (9) passes through the printed circuit board and
on the rear side of the board is electrically connected, preferably
by soldering to a connecting path which is joined to a contact (10)
at the side of the board.
Mounted above each one of the contact strips is a resilient contact
plate (11) consisting of a plate of gold plated nickel silver
formed with a base part with a helical cut and so deformed in an
open spiral to form a resilient raised part (11a) that the free end
of the resilient part (11a) is located towards the under side of
the corresponding push button (5). The depending ring (5a)
surrounds the resilient part (11a) and the post 5b) engages the
free end of the resilient part (11a). Each of the contact plates
also bears a pair of lugs (12) each lug passing through the printed
circuit board and serving to locate the contact plate in position
on the printed circuit board. These lugs are electrically connected
on the under side of the printed circuit board, preferably by
soldering to a conducting path.
The method of manufacture of the contact plate on the printed
circuit board is more fully described in our co-pending British
application for patent No. 53001/73. In operation of the
calculating machine the respective push buttons (5) when operated,
cause a depression of the push button towards the printed circuit
board. Downward movement of the button causes the end of the post
(5b) to move downwardly the free end of the resilient part (11a) of
the contact plate (11) and downward movement is transmitted to the
remainder of the resilient part (11a) to cause the outer part of
the resilient part to move downwards about the fixed contact (9) to
make electrical contact therewith. After the initial contact, there
is some lost motion and then inner resilient part (11a )
diametrically opposite to the outer part already in contact with
the fixed contact (9) makes contact with the fixed contact (9)
possibly simultaneously with the free end of the resilient part
(11a) under the post (5b) abutting the fixed contact (9).
Preferably the fixed contact (9) is made of gold-plated phosphor
bronze wire so that the contact between the resilient part (11a)
and the fixed contact (9) is accompanied by a slight `wiping`
action and the gold-to-gold contact mainly maintains the contact
resistance to a consistently low value.
A major advantage of the keyboard is that, because of the
combination of the helical form of contact plate (11) with the
fixed contact (9) particularly in the form of gold-plated wire the
keyboard is of reduced thickness.
Because of the shape of each of the push buttons (5) the button had
a large bearing area so that during its movement the button does
not wobble about and so jam. The anti-rotation flanges assist in
preventing this wobble.
* * * * *