DE8901047U1 - Membrane keyboard - Google Patents

Description

sÄ]visöN.i& ißüiLow

FAvonSAMSWWflMMaSTJEHNA - D-&bgr;&Ogr;&Ogr;&Ogr; MUNICHS DIPL-PHYS. PATFNTANWAI TiICANTT PI "lELBOM: 088/22 94 61 DRTAMAXELvonBOLOW LAW FIRM mEGFIAMM: SAMPAT D(PL-ING, DfPL-ECONOMICS-ING. TaEX: 8214940 egsad

FAC:089/299465

SNUSON 4 «LOW PAIBiTtHMMJSKMmB ■ WCENMAYBSTR S - CMOCO HJNCHEN 22

Applicant
Wilhelm Ruf KG
Schwanthalerstrasse 18
8000 Munich 2

YOURZBCHBI/YOUSHEF.: UNSB) ZBCHBf/OUR RB-: DATE/DATE

R10-82-B 88 Gm 31.01.1989

vB/13/ma

Membrane keyboard

Description

The innovation relates to a membrane keyboard according to the preamble of claim 1. Such a membrane keyboard is described in US 4,449,023. This consists of two foils lying on top of one another and provided with electrical conductors in the form of conductor tracks. An insulating plastic mass is used as a spacer, which is arranged in certain areas of the foils after the conductor tracks have been applied. The disadvantage of this design lies on the one hand in the great technical effort involved in manufacturing and thus in the relatively high costs and on the other hand in the limited application range of the finished product. Pressure contact between the two conductor tracks is only possible in the conductor track area not covered with the plastic mass.

The DE-GM 76 24 175.3 shows a keyboard consisting of two elements, whereby only one element serves as a carrier of

electrical conductors - This carrier element is a solid base plate, which is provided with partially crossing electrical conductors in the form of conductor tracks with special contact zones. The second element is a flexible mat with key-shaped elevations, which are equipped with conductive contacts on their underside and which, through elastic deformation, are used as contact bridges for the conductor tracks below. This keyboard is complex in terms of the manufacture of the base plate.

EP 0 072 446 describes a keyboard that has conductors in two planes that are aligned in such a way that the electrical conductors cross each other in plan view. Between these planes there is an insulating intermediate layer that has holes at the respective crossing points. The keyboard is covered on both sides with cover foils. By pressing

&Bgr; on the cover foil in the area of the crossing points can

20 <H- ^e crossing conductors are brought into contact with each other. The disadvantage here is the considerable construction effort (two cover foils, two sets of conductors, a

&iacgr; intermediate layer) and the trouble-prone assembly.

25 DE-OS 34 24 060 shows a pressure-sensitive flat

material that has a corrugated mesh made of electrical

< trically conductive wires, which are connected to

coated with an electrically insulating layer.

This corrugated network is thus converted into an electrically

insulating material embedded that the

Wire areas located on the back of the net are

the insulating layer and the insulating material Under the net and from it through a

Part of the insulating material separated runs an electrical

gg trisoh conductive layer. By pressing on the Insulating material can be electrically non-insulated

Sections of the wires of the corrugated net with the

electrically conductive layer in contact

* The disadvantage of this construction is the complicated manufacturing process. The finished product is only obtained after several complex work steps. This wicker material can also be used for keyboards

B, where the location of the activated contact point is decisive for a selective selection of different contacts.

DE-OS 36 19 035 shows two reinforced by base foils

te electrically conductive foils, in whose respective

Metal wires are inserted into the surfaces. These two

electrically insulating foils are placed on top of each other in such a way that the sides with the metal wires There are numerous gaps between the foils electrically insulating spacers are arranged. This design has the disadvantage that between the

Elements still need to be fitted with separate spacers

In addition, the application range of the finished

Products are limited because in the areas that have a spacers, a pressure contact of the two conductor tracks is not possible.

US-PS 3 056 005 shows two layers of an electrically conductive wire mesh with an intermediate "Spacer foil". Since the weft threads are also conductive, they cannot take on a spacer function. A spacer foil is therefore absolutely necessary. In addition, such wire meshes, which are electrically conductive in all coordinate directions, do not

Keyboard can be realized.

The DE-GM 69 32 723 shows two layers of electrical conductors, one layer of which consists of an electrically conductive wire mesh. Therefore, the installation of a spacer foil is also mandatory here. This is not a keyboard either.

The innovation is based on the task of creating an extremely

If· i ■ 4 · ·

7 to realize a flat membrane keyboard.

This problem is solved according to the innovation by the features specified in the characterizing part of claim 1.

Advantageous further developments of the innovation emerge from subclaims 2 to 11.

The innovation has the advantage, among other things, that the alignment of two conductor levels and a spacer is no longer necessary, or that no precise adjustment is required. Another advantage is that the membrane keyboard is particularly easy to use thanks to the innovation. manufacture and easy to assemble.

Advantageously, both the spacer function and the function of a carrier for electrical conductors are performed by a single component, the corrugated insulating material. In addition to the simpler and particularly inexpensive production, the extremely flat design and effortless assembly result in a wide range of possible applications.

The innovation is also suitable for pressure sensors or for the electrical determination of the position of an object in a coordinate system. This determination of position is carried out by applying pressure and can also be triggered by the weight of the object on the surface of the membrane keyboard.

3Q will be.

According to a first variant of the innovation, the corrugated carrier is made of plastic (e.g. Mylar from Du Font), with the corrugation valleys on one side being partially filled with electrically conductive material such as conductive paint. These conductor tracks can be applied using a squeegee known from screen printing technology, for example. In addition, the

Carriers provided with conductor tracks, regardless of type The assembly is particularly efficient, since the corrugated carrier with conductor tracks can be cut, assembled and contacted without any problems. needs.

According to a second variant of the innovation, the corrugated insulating material consists of the weft threads of a fabric, the warp threads of which are electrically conductive. The warp threads can be carbon fibers, for example, while the weft threads consist of polyester fibers, for example. This creates a carrier that is very easy to handle, since both sides of the fabric are the same and therefore swapping the sides is irrelevant for the function of the membrane keyboard. The construction of a switching element is very simple here, since the two fabrics only need to be placed on top of each other in their warp directions, and they can be glued together at certain points. The required element can then simply be punched out. With the appropriate equipment, the operations can also be carried out simultaneously.

In both of the above variants of the innovation, a further development provides that only one of the two supports for insulating materials is corrugated, while the other support is flat, which allows an even flatter design of the membrane keyboard to be achieved.

If the flat insulating material is provided with only one conductor covering the entire surface, the innovation

QQ a large contact area can also be achieved. This can be used, for example, to produce floor mats for triggering switching functions for automatic doors or for switching on escalators. By appropriately dimensioning the wave crests forming the spacer and thus by adjusting the force required to trigger a contact, the membrane keypad of the innovation can be used for alarm systems, e.g. in floor panels. This can be used to create a radial arm caused by smaller animals

can be excluded, as can occur with infrared or ultrasound systems. The membrane keyboard according to the innovation can be incorporated in the form of a strip in the road surface to count vehicles and thus also be used to control traffic lights instead of induction loops.

By tapping several parallel conductors, a redundancy effect can also be achieved with the innovation, as the membrane keyboard is thus less sensitive to possible short circuits or interruptions caused by production.

With any crossing angle of the conductors running one above the other between 20° and 90°, a greater scope for the arrangement of individual switches is possible.
If corrugated insulating materials are used which are translucent due to their material or structure, surface illumination of control panels can be achieved by lighting from behind or by feeding light from the side parallel to the corrugations.

In the following, the innovation is explained in more detail using examples of implementation in conjunction with a drawing. It shows:

Fig.l a section through two superimposed supports made of homogeneous insulating material according to a first variant of the innovation;

Fig.2 a perspective view of the in Fig. 1

insulating material shown in the cross section.

Fig.3 a section through two superimposed, elastic fabrics attached to a base plate

or are attached to a housing, according to a second variant of the innovation;

»ff · ·

t * · I

Fig.4 a section of the tissues shown in Fig. 3

with a spacer film in between.

Fig. 1 shows two insulating materials 1 lying one above the other in the form of flexible, corrugated films made of plastic. The corrugated insulating materials 1 are provided with electrical conductors 2 in the form of strip conductors in their troughs 3 facing the other insulating material, part of their depth. These consist of carbon lacquers, for example, and are applied using a squeegee, for example in a similar way to screen printing. One insulating material 1 is placed on the other insulating material 1 in such a way that the sides with the electrical conductors 2 face each other and these conductors 2 cross at an angle of, for example, 90°. The other insulating material 1 can be a second flexible, corrugated film of the same structure, as shown in Figs. 1 and 2I. The crossing strip conductors 2 of the two insulating materials 1 lying one above the other are at a distance from each other in the rest position which is | formed by the protruding wave crests 4 facing the other insulating material §. If one §

If a pressure is exerted on the insulating material 1 in the region of a wave crest 5 facing away from the _other insulating material, the latter deforms in such a way that the two opposing, crossing conductor tracks 2 come into contact with one another and establish an electrical contact. If the pressure is removed, the insulating material 1 deforms back to its uniform wave structure of the output layer due to its restoring force, whereby the distance between the conductor tracks 2 is restored in the rest position.

3g One of the insulating materials 1 can also be a solid, non-corrugated insulating material. The function of the elastic spacer is then only taken over by a corrugated insulating material 1.

I · I > ■ ·

In addition, the crossing angle of the superimposed conductors 2 can have any value between 20" and 90".

Fig. 2 shows two flexible, corrugated insulating materials 1 lying one on top of the other, in which the conductor track axes of one and the other insulating material 1 intersect at an angle of 90°.

Fig. 3 shows a flexible, corrugated fabric as insulating material 1 in which the weft threads 6 are made of electrically non- conductive material, while the warp threads are conductive and consist of carbon threads, for example. The warp threads take on the function of the electrical see conductor 2. This fabric is placed over a second fabric of the same type in such a way that the electrical conductors 2, i.e. the warp threads of the two fabrics, cross at any angle. These crossing electrical conductors 2 have a distance to each other, which is formed by the insulating weft threads 6 that surround the conductive warp threads. The wavy shape of the weft threads 6 also forms wave crests 4 and wave troughs 3, with the wave crests 4 taking on the function of a spacer. The Fabrics are attached to a base plate 7 or to a housing. If pressure is exerted on one of the fabrics, the two flexible fabrics deform in such a way that the two crossing electrical conductors 2 lying on top of each other, i.e. the warp threads 2, come into contact and establish an electrical contact. When the pressure is stopped, the two fabrics deform back into their uniform wave structure of the starting position, whereby the distance between the electrical conductors 2, i.e. the warp threads, is restored in the resting position.

The contact of the carbon fibers can be achieved by the

Installation of clamps in the fabric or by conductive adhesive. The contact clamps can

II t · · &igr; ItI

12 for example, it can also be injected into the housing.

The production of membrane keyboards can be carried out by automatically unwinding two endless belts. The fabric of the two endless belts differs only in terms of its warp thread direction. The two fabrics can be glued at points and then pressed together. At the same time, the membrane keyboard element can be punched out.

Fig. 4 shows two flexible, corrugated fabrics lying on top of each other, as described in Fig. 3. The difference is that between the two elements there is an additional spacer film 8 which is self-adhesive on both sides. This spacer foil has an opening 9 at the points where the two superimposed crossing electrical conductors 2, i.e. the warp threads, are to come into contact by pressure. By additionally inserting the spacer foil 8, A locket woven fabric can also be used, where without spacer foil 8 an electrical contact between the two superimposed, crossing electrical conductors 2, i.e. the warp threads, would have to be feared even in the resting position.

The membrane keyboard with a spacer between the two fabrics can also be manufactured automatically. This requires two endless fabric tapes and a spacer as a perforated endless tape. The transport of the three tapes can be done automatically. During the infeed, the protective paper of the double-sided adhesive spacer film is unwound. The fabric-spacer-fabric element is then pressed together and possibly punched out at the same time. The production of a membrane keyboard from g two fabrics separated by a spacer film 8 can also be printed on. A fabric tape is stretched over a ball plate. A spacer film is then printed on. The fabric is thereby simultaneously

Base plate fixed, this process can also be carried out using a modified printing machine. The second fabric tape is stretched over it and again fixed using printing technology or glued to a suitable spacer layer using pressure and/or temperature. The membrane keyboard element is then punched out.

Claims (11)

PRIME LAWYERS SAMS(QN ₁ !(&KHgr; JjXjJLjKS YY WIDENMAVERSTR.5 F.R. von SAMSON-HIMMELSTJERNA &udiagr;·8000 MONKS 22 DlPL-PHYS. TtATRNTANw-At TSK&Agr;&Ngr;71 Pt TELEPHONE:089/2294et DR. &Tgr;&Agr;&Mgr; AXEL von BOLOW GODFATHER IAINWALISKAINZ ₁ LtH TELEGRAM SAMPAT DIPL-INQ., 0IPL-WIRTSCK-INq. TELEX: 52149*0 egMd Fax: 089/299465 SAMSON &Lgr; BULOW - PATBiTAN LAW FIRM WIOENMAYERSTR. S 0-&bgr;&Ogr;&Ogr;&Ogr; MUNICH 22 Applicant
Wilhelm Ruf KG
Schwanthalerstrasse 18
Munich 2 YOUR NUMBER/YOUR REF.: OUR NUMBER/OUR REF: DATE/DATE: R10-82-B 88 Gm 31.01.1989 vB/13/ma Membrane keyboard S ection claims 1. Membrane keyboard with electrical conductors arranged one above the other in the rest position in two planes, of which at least the conductors of one plane are attached to insulating material, the insulating material of at least one plane being flexible in such a way that when this insulating material is elastically deformed, conductors of this plane are in contact with conductors of the other plane, characterized in that the flexible insulating material (1) is corrugated in a cross-sectional plane, and that the wave crests (4) of the flexible insulating material (1) facing the conductors (2) of the other plane protrude beyond the conductors (2) arranged in the wave troughs (3). 2. Membrane keyboard according to claim 1, characterized in that the at least one flexible corrugated Insulating material (1) made of a homogeneous, insulating material, preferably plastic, 1st. 3. Membrane keyboard according to claim 1 or 2, characterized in that the conductors (2) are made of conductive Lacquer in the form of conductor tracks. 4. Membrane keyboard according to claim 1, characterized in that the at least one flexible, corrugated insulating material (1) comprises the weft threads of a fabric whose warp threads are the conductors (2). 5. Membrane keyboard according to claim 1 or 4, characterized in that the conductors (2) are made of carbon fibers. 6. Membrane keyboard according to one of claims 1, 4 or 5, characterized in that a spacer film (8) provided with recesses is additionally arranged between the conductors of the two levels. 7. Membrane keyboard according to one of claims 1 to 6, characterized in that only the insulating material (1/ for the conductors of one level is corrugated, while the insulating material for the conductors of the other level is flat. 8. Membrane keyboard according to claim 7, characterized in that the planar insulating material has a 3Q single electrical surface covering conductor. 9. Membrane keyboard according to one of claims 1 to 7, characterized in that in each case several 3g conductors (2) lying next to one another in a plane are electrically connected to one another, i.e. are electrically connected in parallel. 10. Membrane keyboard according to one of claims 7 or 9, characterized in that the electrical conductors (2) of the two planes intersect in plan view at an angle of 20° to 90°. 11. Membrane keyboard according to one of claims 1 to 10, characterized in that the insulating material 1 is transparent.