GB2191340A - Interchangeable designation for membrane keyboard - Google Patents

Description

GB2191340A 1 SPECIFICATION that the user can not confidently determine

whether the -button- has been actuated. One Membrane keyboard method of overcoming this drawback is the use of an audible feedback signal generated This invention relates to an improved keypad 70 by the circuitry when a button is operated.

and will be described with reference to a key- The autobank system uses such an arrange pad for a telephone though the invention is ment. This arrangement requires circuitry to not limited to such an application. detect the button operation and to generate a In recent years push buttons have replaced signal to be fed to an electro- acoustic trans the rotary dial in most subsets. Push buttons 75 ducer.

are fairly complicated mechanical devices According to a second aspect, the present which usually incorporate a return spring, elec- invention comprises a membrane keypad ac trical contacts and suitable mouting arrange- cording to the first aspect having tactile feed ments. back means adapted to overlay at least one of A recent development has been the mem80 said membranes, comprising a flexible plate brane keypad which basically consists of a having raised areas at positions corresponding pair of membranes one of which has a first to positions of said button locations, said array, e.g. columns and the other of which raised areas adapted to flex downwardly on has a second array, e.g. rows of contact pads the application of pressure thereto.

which can be used to uniquely identify a de- 85 For preference, the tactile feedback plate is sired -button-. The membranes are separated made sufficiently rigid so that an audible by a spacer having holes corresponding to the sound is produced by said flexing of the ---button-locations. When a---button-is raised areas.

pushed the conductive tracks on the upper In a further form of the invention the func- membrane are brought into contact with those 90 tions of the designation and tactile feedback of the lower membrane so there is a change means are combined avoiding the need for in the electrical resistance between the row special -clickers-.

and column involved. The upper membrane According to this further aspect, the present must have some resilience, and while the invention provides a membrane keyboard com lower membrane may also be flexible, it is 95 prising two membranes separated by a spacer preferable that its tracks be rigidly mounted sheet having a plurality of holes therein corre so the lower membrane may be placed on or sponding to button locations for said key replaced by a fairly rigid substrate. board, One feature of the new generation telephone said membranes each having complementary is the use of microprocessors to incorporate a 100 arrays of contact pads such that contact be number of features in the subset. One such tween the two membranes at the position of feature is a memory to store frequently called each of said plurality of holes can be uniquely numbers. Some phones have provision to identified; write the allocated number to be called in a combined identification/tactile feedback proximity to the related button. However the 105 means overlaying one of said membranes numbers and destinations or purpose associ- comprising a flexible sheet having raised areas ated with some of the buttons may change at positions corresponding to said button loca from time to time. To overcome this problem tions, said raised areas adapted to resiliently it is proposed to provide an improved keypad flex downwardly on application of finger pres with removable button designation means. 110 sure thereto.

According to a first aspect, the present in- For preference, said keyboard is overlaid by vention provides a membrane keypad compris- an embossed sheet having raised portions ing at least two membranes separated by a adapted to cover said raised areas of the key spacer sheet having a plurality of holes therein board. Preferably, the embossed sheet is of corresponding to button locations for said 115 clear plastic material.

keypad, Preferred embodiments of the invention will said membranes each having complementary now be described, by way of example only, arrays of contact pads such that contact be- with reference to the accompanying drawings; tween the two membranes at the position of in which:

each of said plurality of holes can be uniquely 120 Figure 1 is a partial exploded view showing identified, a membrane keypad incorporating the repla removable keypad designation means ceable designation card according to the in adapted to overlay at least one of said mem- vention; branes and align designations thereon with as- Figure 2 is a similar view to Figure 1 but sociated button locations. 125 incorporating tactile feedback means; The designation means preferably comprises Figure 3 shows a cross sectional view of a thin card which is sufficiently flexible to be the keyboard according to a further embodi slid under a transparent flexible sheet cover ment, taken on line 3-3 of Figure 4; provided in the membrane keypad. Figure 4 show a partial plan view of the A disadvantage of the membrane keypad is 130 keyboard shown in Figure 3; 2 GB2191340A 2 Figure 5 is a plan view of a membrane ac- sufficiently thick.

cording to the invention having a remote key- Referring to Figures 3 and 4 of the draw- pad arrangement; ings, a plastic base 18 has a first membrane Figure 6 is a plan view of a membrane ac- 9, in this case a flexible printed circuit board cording to the invention adapted to be be 70 attached to its upper surface. This circuit folded to form the upper and lower mem- board has formed on its upper surface, adja branes; cent the push button locations, pairs of con- Figure 7A and 713 are plan views of alter- tacts 17 which are connected together by a nate contact pad arrangements according mating contact 16 on depression of a -push the invention. 75 button---. These contacts 16 are formed on the Referring to Figure 1 the top cover 1 is undersurface of a further flexible printed board flexible and has transparent windows, 2, cor- 6 forming the second membrane which over responding to button positions. This sits on a lays the first membrane and is spaced there spacer 3 which conforms to the perimeter of from by a spacer 7. Spacer 7 has a plurality 1 but is open ended on one side to allow 80 of holes 1' formed therein, at positions corre insertion of the designation card 4. Card 4 is sponding to said--pushbuttons---.

sufficiently rigid to allow it to be pushed into Flexible printed circuit board 6 is further place in the space provided under cover 1 by overlaid by a designation card 4 made of re spacer 3 and has designation indicia 5 printed silient flexible material and having a plurality of thereon. This space is in practice a push-fit 85 raised dimples 14 at locations corresponding with card 4 to ensure sufficient friction to re- to said---pushbuttons---. These dimples 14 tain the card in place during normal operation. provide a collapse action tactile feedback on Card 4 and cover 1 are sufficiently flexible to depression of a push button. Thus the desig allow operation of the membrane contacts be- nation card 4 serves the dual purpose of indi- low. 90 cating the function of each button and provid- Under card 3 is the upper membrane 6 ing tactile feedback to the keyboard user.

which has. an array of columns (or rows) of In order to protect the keyboard from the conductive pads (not shown) on its under sur- ingress of moisture, dust and other unwanted face. A further spacer 8 having spaces which materials as well as protecting the surface of conform to the boundaries of each button lo- 95 the designation card from wear which could cation and substantially enclose the conductive obscure the indicia provided thereon, the de pads for each button on the upper and lower signation card is overlaid by an embossed membranes 6 and 9. Membrane 9 has rows clear plastic sheet 1. This sheet is embossed (or columns) of conductive pads (not shown) to provide raised areas which cover the raised arranged to correspond with associated pads 100 dimples of the designation card while contact of membrane 6. Adhesive tape 10 is provided ing the periphery of each - push button- loca to fix the membrane keyboard in position. tion on the designation card. The embossed In Figure 2 a clicker plate 11 comprises a sheet thus serves to encapsulate the area of thin resilient plate of for example rubber, plas- each -push buttonlocation by means of em- tics or metal, the plate has dimples or domes 105 bossed channels 15 which are attached to the (not shown) corresponding with the locations designation card. In order to allow for depres of the buttons. The purpose of these domes sion of these encapsulated areas small air is to provide tactile feedback to the operation channels 19 are provided to join adjacent en as they collapse when the button is depressed capsulated areas.

so the operator can---feel-the operation of 110 Referring to Figures 5 and 6, a further im the button. If the clicker plate is sufficiently provement is the addition of remote switching stiff it will also produce a---click-as the but- facilities. As the conductive tracks and mem ton is operated giving acoustic as well as tac- brane are flexible it is proposed to use the tile feedback. A spacer 12 is also associated same facilities for switching at a location re- with the clicker plate 11. If the clicker plate 115 mote from the keypad. Indeed it is not neces- 11 and spacer 12 are mounted above the sary for the remote location to be in the same membrane 9 it may be covered by an addi- plane as the keypad. One such application is tional flat flexible membrane 13 to ensure that the use of a membrane switch as a gravity the card 4 does not catch on the domes of switch actuator. A remote pad 21 attached to plate 11 when the card is being pushed into 120 and part of the membranes 20 is located to place. be actuated by the hook switch by a flexible If the clicker plate 11 is mounted under strip of the membrane. As shown in Figure 5 membrane 9 (which must be flexible in such a the additional strip 21 projects from the main case) the additional membrane 13 should not keypad membranes and contains one or more be required. In this case the clicker plate may 125 additional pads. Of course the pads may not provide sufficient rigidity to act as a substrate be capable of carrying telephone line current for membrane 9 but tolerances may become so the gravity switch pads could actuate an critical as the domes could act against the electronic line switch.

pads of membrane 6 to cause contact with In an alternative embodiments, as shown in the pads on membrane 6 if spacer 12 is not 130 Figure 7A and 713, instead of having the row 3 GB2191340A 3 and column layout, one of the membranes 7. A membrane keypad according to anyone may comprise a pair of pads 27 and 28 of the preceding claims wherein one of said which may comprise two sets of fingers 29 arrays of contact pads on one of said mem which are interleaved or two sets of inter- branes includes at each said button position a woven spirals 30 and 31, while the other 70 pair of pads which are connected by an asso membrane may contain a bridging pad to inciated third shorting pad on said other mem terconnect the two pads of the first mem- brane.

brane. The advantage of this is that all the 8. A membrane keypad according to claim active leads can be taken off the keypad at a 7 whirein said pair of pads comprise two sets single connection point 22 and can be con- 75 of interleaved fingers.

tained on one membrane and this simplifies 9. A membrane keypad according to claim connections between the membrane and the 7 wherein said pair of pads comprise two rest of the telephone circuit. sets of interwoven spirals.

A further embodiment, as shown in Figure 10. A membrane keypad according to any- 6, achieves a similar advantage by printing 80 one of claims 1 to 6 wherein the complemen both the upper and lower pad layouts on a tary pads are formed on a single membrane single piece of membrane 23. The pad layouts which is folded to form said two membranes.

are aligned when the membrane is folded over 11. A membrane keypad according claim 1 the spacer. This again allows the connection wherein said designation means includes tac- point 26 to be on one side only. Remote pads 85 tile feedback means formed integrally there- 24 and 25 can also be formed in this manner. with.

It will be apparent to those skilled in the art 12. A membrane keypad according to claim that further embodiments of the invention de- 11 wherein said tactile feedback means com scribed are possible without departing from prises a flexible sheet having raised areas at the spirit or scope of the invention. 90 positions corresponding to said button loca tions, said raised areas adapted to resiliently

Claims (1)

1. CLAIMS flex downwardly on application of finger pres

   1. A membrane keypad comprising at least sure thereto.

   two membranes separated by a spacer sheet 13. A membrane keypad according to claim having a plurality of holes therein correspond- 95 12 wherein said keyboard is overlaid by an ing to button locations for said keypad, embossed transparent sheet having raised por said membranes each having complementary tions adapted to cover said raised areas of arrays of contact pads such that contact be- the keyboard.

   tween the two membranes at the position of 14. A membrane keyboard substantially as each of said plurality of holes can be uniquely 100 hereinbefore described with reference to Fig identified, ure 1, Figure 2 or Figures 3 and 4 of the removable keypad designation means accompanying drawings.

   adapted to overlay at least one of said mem Printed for Her Majesty's Stationery Office branes and align designations thereon with as- by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987.

   sociated button locations. Published at The Patent Office, 25 Southampton Buildings, 2. A membrane keypad according to claim London, WC2A lAY, from which copies may be obtained.

   1 having a transparent flexible cover sheet provided thereon.

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

   4. A membrane keypad according to anyone of the preceding claims having tactile feedback means adapted to overlay at least one of said membranes, 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 ap- plication of pressure thereto.

   5. A membrane keypad according to claim 4 wherein said tactile feedback plate is sufficiently rigid to produce an audible sound during flexing of said raised areas.

   6. A membrane keypad according to claims 4 or 5 wherein said tactile 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.