AU598813B2 - Membrane keyboard - Google Patents

Description

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59 88 13 COMMONWEALTH OF AUSTRALIA FORM PATENTS ACT 1952 COMPLETE SPECIF I C A T 1 ON FOR OFFICE USE: 7 2? Class Int.Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: o f #Priority: r 44 4 Related Art: 9194 94r Name of Applicant: Address of Applicant: **Actual Inventor: Cic-1A Aivl79RA LIIt-l7V) AMLGAGMATED-WIRELESS -(AUSTRALASIA) 'LIMITED -47 -York Streetj, SYDNEY N.S.W.-,--2000 6t JAN WASZCZUK 'Address for Service: -SHELSTON-WATERS1-55-larence-r -eet, Sydney 4 ,omplete Specification for the Invention entitled: 4ac ft I "MEMBRANE KEYBOARD" The following statement is a full description of this invention, including the best method of performing it known to me/us:- Complete of PH5994 Dated 20-5-86 and PH 9331 Dated 4-12-86

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_i File: Fee: $60.00 SF ATTACHED SIXTY DOLLARS 1 s This invention relates to an improved keypad and will be described with reference to a keypad for a telephone though the invention is not limited to such an application.

In recent years push buttons have replaced the rotary dial in most subsets. Push buttons are fairly complicated mechanical devices which usually incorporate a return spring, electrical contacts and suitable mouting arrangements.

A recent development has been the membrane keypad which basically consists of a pair of membranes one of which has a first array, e.g. columns and the other of i which has a second array, e.g. rows of contact pads which I can be used to uniquely identify a desired "button". The membranes are separated by a spacer having holes corresponding to the "button" locations. When a "button" is pushed the conductive tracks on the upper membrane are brought into contact with those of the lower membrane so there is a change in the electrical resistance between the row and column involved. The upper membrane must have some resilience, and while the lower membrane may also be flexible, it is preferable that its tracks be rigidly mounted so the lower membrane may be placed on or replaced by a fairly rigid substrate.

One feature of the new generation telephone is the use of microprocessors to incorporate a number of features in the subset. One such feature is a memory to store frequently called numbers. Some phones have provision to write the allocated number to be called in proximity to -2t' To THE COMMISSIONIK UI- IA I -N I SHELSTON WATERS PATENT ATTORNEYS CLARENCE STREET. SYDNEY

AUSTRALIA

Cables: 'Valid' Sydney Telex: 24422 -3the related button. However the numbers and destinations or purpose associated with some of the buttons may change from time to time. To overcome this problem it Is proposed to provide an improved keypad with removable button designation means.

One disadvantage with known membrane keypads is that tho user can not confidently determine whether the "button" has been actuated. One method of overcoming this drawback Is the use of an audible feedback signal generated by the circuitry when a button is operated. The autobank system uses such an arrangement. This arrangement requires circuitry to detect the button operation and to generate a signal to be fed to an electro-acoustic transducer.

In accordance with the present invention there Is disclosed a membrane keypad comprising at least two membranes separated by a spacer sheet having a plurality of holes therein corresponding to button locations for said keypad, said membranes each having complementary arrays of contact pcds such o that contact between the two membranes at the position of each of said "plurality of holes can be uniquely identified; removable keypad designation means adapted to overlay at least one of said membranes and align designations thereon with associated button Alocations; and tactile feedback means adapted to overlay at least one of said membranes, said tactile feedback means comprising a flexible plate having raised areas at positions corresponding to positions of said button locations, said raised areas adapted to flex downwardly on the application of pressure thereto.

The designation means preferably comprises a thin card which Is sufficiently flexible to be slid under a transparent flexible sheet cover provided in the membrane keypad.

S 30 For preference, the tactile feedback plate is made sufficiently rigid so that an audible sound is produced by said flexing of the raised areas.

In a further form of the invention the functions of the designation and tactile feedback means are combined avoiding the need for special "cI ckers".

IAD/929o 4 According to this further aspect, the present invention provides a membrane keyboard comprising two membranes separated by a spacer sheet having a plurality of holes therein corresponding to button locations for said keyboard, said membranes each having complementary arrays of contact pads such that contact between the two membranes at the position of each of said plurality of holes can be uniquely identified; a combined Identification/tactile feedback means overlaying one of said membranes comprising a flexible sheet having raised areas at positions corresponding to said button locations, said raised areas adapted to resiliently flex downwardly on application of finger e D o IAD/990, AD929o3 I pressure thereto.

For preference, said keyboard is overlaid by an embossed sheet having raised portions adapted to cover said raised areas of the keyboard. Preferably, the embossed sheet is of clear plastic material.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings; in which: Figure 1 is a partial exploded view showing a membrane keypad incorporating the replaceable designation card -according -the; -Figure 2 is a similar view to Figure 1 but *o incorporating tactile feedback means; *Figure 3 shows a cross sectional view of the keyboard according to a further embodiment, taken on line 3-3 of Figure 4; Figure 4 show a partial plan view of the keyboard shown in Figure 3; Figure 5 is a plan view of a membrane co g t ehi en- n- having a remote keypad arrangement; Figure 6 is a plan view of a membrane -eeor4 tt he--iveno adapted to be be folded to form the upper and lower membranes; Figure 7A and 713 are plan views of alternate contact pad arrangements -ao.4ng h-he e-l.enb-en.

Referring to Figure 1 the top cover 1 is flexible and has transparent windows, 2, corresponding to button positions. This sits on a spacer 3 which conforms to the 5 it i perimeter of 1 but is open ended on one side to allow insertion of the designation card 4. Card 4 is sufficiently rigid to allow it to be pushed into place in the space provided under cover 1 by spacer 3 and has designation indicia 5 printed thereon. This space is in practice a push-fit with card 4 to ensure sufficient friction to retain the card in place during normal operation. Card 4 and cover 1 are sufficiently flexible to allow operation of the membrane contacts below.

Under card 3 is the upper membrane 6 which has an array of columns (or rows) of conductive pads (not shown) on its under surface. A further spacer 8 having spaces iwhich conform to the boundaries of each button location and substantially enclose the conductive pads for each button on the upper and lower membranes 6 and 9. Membrane 9 has rows (or columns) of conductive pads (not shown) arranged to correspond with associated pads of membrane 6. Adhesive tape 10 is provided to fix the membrane k eyboard in position.

0 In Figure 2 a clicker plate 11 comprises a thin resilient plate of for example rubber, plastics or metal, 20 the plate has dimples or domes (not shown) corresponding with the locations of the buttons. The purpose of these domes is to provide tactile feedback to the operation as they collapse when the button is depressed so the operator can "feel" the operation of the button. If the clicker plate is sufficiently stiff it will also produce a "click" as the button is operated giving acoustic as well as tactile feedback. A spacer 12 is also associated with the clicker plate 11. If the clicker plate 11 and spacer 12 6 r are mounted above the membrane 9 it may be covered by an additional flat flexible membrane 13 to ensure that the card 4 does not catch on the do)mes of plate 11 when the card is being pushed into place.

If the clicker plate 11 is mounted under membrane 9 (which must be flexible in such a case) the additional membrane 13 should not be required. In this case the click~er plate may provide sufficient rigidity to act as a substrate for membrane 9 but tolerances may become critical as the domes could act against the pads of membrane 6 to cause contact with the pads on membrane 6 if spacer 12 is not sufficiently thick.

Referring to Figures 3 and 4 of the drawings, a 04 0 plastic base 18 has a first membrane 9, in this case a :m j* flexible printed circuit board attached to its upper surfce.This circuit board 'has formed on its upper 0.

surface, adjacent the push button locations, pairs of 1 4 #0 contacts 17 which are connected together by a mating contact 16 on depression of a "push button". These contacts 16 are formed on the undersurface of a further flexible printed board 6 forming the second membrane which overlays the first membrane arid is spaced therefrom by a spacer 7. Spacer 7 has a plurality of holes 1' formued thoreint at positions corresponding to said "push buttons".

'Flexible printed circuit board 6 is: further overlaid by a designation card 4 made of resilient flexible material and having a pl.urality of raised dimple~s 14 at locations corresponding to said "push buttons". Trhese -7 dimples 14 provide a collapse action tactile feedback on depression of a push button. Thus the designation card 4 serves the dual purpose of indicating the function of each button and providing tactile feedback to the keyboard user.

In order to protect the keyboard from the ingress of moisture, dust and other unwanted materials as well s, protecting the surface of the designation card from wear whic.-h could obscure the indicia provided thereon, the designation card is overlaid by an embossed clear plastic sheet 1. This sheet is embossed to provide raised areas which cover the raised dimples of the designation card while contacting the periphery of each "push button" location on the designation card. The embossed sheet thus serves to encapsulate the area of each "push button" location by means of embossed channels 1$ which are attached to the designation card. In order to allow for depression of these encapsulated areas small air channels 19 are provided to join adjacent encapsulated areas.

Referring to r~igures 5 and 6, a further improvement is the addition of remote switching facilities. As the conductive tracks and membrane ate flexible it is proposed to use the same facilities for switching at a location rkimnote from the keypad. Indoeed it is not necessary foc the remote location to be in the same pl3ane an the keypad. One Such application 'in the use of a mmeubrane, switch as a gravity switch aetuator* A remtote pad 21 attached to and part of the membranes 20 is located to be actuated by the hook switch by a flexible strip of the membrane. As shown in Figure 5 the additional strip 21 projects from the main keypad membranes and contains one or more additional pads. Of course the pads may not be capable of carrying telephone line current so the gravity switch pads could actuate an electronic line switch.

In an alternative embodiments, as shown in Figure 7A and 7B, instead of having the row and column layout, one of the membranes may comprise a pair of pads 27 and 28 which may comprise two sets of fingers 29 which are interleaved or two sets of interwoven spirals 30 and 31, while the other membrane may contain a bridging pad to interconnect the two pads of the first membrane. The r: advantage of this is that all the active leads can be taken off the keypad at a single connection point 22 and can be contained on one membrane and this simplifies connections between the membrane and the rest of the telephone circuit.

A further embodiment, as shown in Figure 6, achieves a similar advantage by printing both the upper and lower pad layouts on a single piece of membrane 23. The pad layouts are aligned when the membrane is folded over the spacer. This again allows the connection point 26 to be on one side only. Remote pads 24 and 25 can also be formed in this manner.

Xt will be apparent to those skilled in the art that further embodiments of the invention described are possible without departing from the spirit or scope of the invention.

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Claims (11)

1. A membrane keypad comprising at least two membranes separated by a spacer sheet having a plurality of holes therein corresponding to button locations for said keypad, said membranes each having complementary arrays of contact pads such that contact between the two membranes at the position of each of said plurality of holes can be uniquely identified; removable keypad designation means adapted to overlay at least one of sald membranes and align designations thereon with associated button locations; and tactile feedback means adapted to overlay at least one of said membranes, said tactile feedback means comprising a flexible plate having raised areas at positions corresponding to positions of said button locations, said raised areas adapted to flex downwardly on the application i of pressure thereto,

2. A membrane keypad as claimed in claim I having a transparent flexible cover sheet provided thereon.

3. A membrane keypad as claimed in claim 2 wherein said designation means comprises a thin card adapted to be slid under said transparent flexible cover sheet,

4. A membrane keypad as claimed in any one of the preceding claims wherein said tactile feedback plate is sufficiently rigid to produce an audible sound during flexing of said raised areas.

A membrane keypad as claimed in claim 1 or 4 wherein said tactlle feedback plate Is positioned between said membrane and said designation means and further flexible membrane is positioned between said feedback plate and said designation means.

6. A membrane keypad as claimed in any one of the preceding claims V wherein one of said arrays of contact pads on one of said membranes includes at each said button position a pair of pads which are connected by an associated third shorting pad on said other membrane.,

7. A membrane keypad as clailmed in claim 6 wherein said pair of pads comprise two sets of Interleaved flingers.

8. A membrane keypad as clamed in claim 6 wherein said pair of pads comprise two sets of Interwoven spirals, 1 392 9 s41 11

9. A membrane keypad as claimed in any one of claims 1 to 5 wherein the complementary pads are formed on a single membrane which is folded to form said two membranes.

A membrane keypad as claimed in any one of the preceding claims wherein said designation means Includes said tactile feedback means formed integrally therewith.

11. A membrane keyboard substantially as hereinbefore described with reference to Figure 1, Figure 2 or Figures 3 and 4 of the accompanying drawings. DATED this EIGHTEENTH day of APRIL 1990 Exicom Australia Pty Limited Patent Attorneys for the Applicant SPRUSON FERGUSON *4 4*i 4 $4 I I i i I I IAD/1929o i i I i i