EP1391905B1 - Flat key pad - Google Patents

Abstract

A soft, elastic rubber or plastic layer (5), e.g. made of silicon rubber foam, is associated with the switch component (2). The operational force (4) acts indirectly upon it.

Description

The invention relates to a flat keyboard for operating an electrically controlled device, for example a hand-held laser rangefinder, according to the preamble of claim 1.

The majority of the electrically controlled devices used in various fields of application has to operate the same as a human-machine interface a keyboard with at least one button. Depending on the type and size of the respective device, the dimensions or design variants of the built-in keyboard can decisively influence the design, the shape and in particular the dimensions of the device.

Since typically the dimensions of the front face of the keyboard are dictated by the number of keys, their area and arrangement, the height of the keyboard is often the only degree of freedom for minimizing the size of the keyboard. Especially compact devices, for example for a mobile, especially by hand use, today have flat keyboards, which typically do not exceed a height of a few millimeters.

With the exception of piezo keypads, which are mainly used for applications with extreme demands on robustness, virtually all flat keyboards are designed as membrane keypads. Membrane keyboards consist at least of a front-side tactile film with multiple tactile areas for triggering each a function of the keyboard, which tactile film with a support element insoluble is connected to an integral, ready-to-install control unit, which may be water or even gas-tight. The carrier element in turn can be designed as a carrier board or as a carrier film. The latter embodiment of a membrane keyboard even allows bendable embodiments of flat keyboards. With membrane keyboards even building heights in the order of a millimeter can be realized with a correspondingly low weight.

In addition, membrane keypads are - compared to alternative keyboard designs, for example, rubber body with protruding tower-shaped rubber blocks or patch, rigid key body - by a much cheaper production and a simple attachment to the outer surface of the device housing, which is freely accessible feasible. Membrane keyboards are therefore often used in low-cost products.

From the introduction to the description of the DE 196 50 468 C2 a membrane keyboard is known, which is composed of several flatly bonded individual sheets. In addition to the tactile film and the carrier film with printed conductor tracks, further films, for example a spacer film, a design film or an adhesive film may be provided. The keyboard as a prefabricated unit from above freely accessible on the top of a device housing - for example, polycarbonate - placed and glued via an applied on the back of the keyboard adhesive film by pressing in a simple way with the housing. The connection leads are led down through the housing. The edge area of the keyboard is glued peripherally with the housing to To achieve a tight connection between the self-contained keyboard unit and the housing.

In addition to many advantages, today's membrane keypads have a central weak point. In particular, they have a rather modest operating comfort, in particular in comparison to the alternative non-planar keyboard types.

The ease of use of keyboards - as perceived by the user - depends on a variety of criteria. The detection, the tactile feel and in particular the sensitivity in striking the areas that are provided for triggering the individual functions of the keyboard, in addition to mechanical and / or acoustic feedbacks have a very decisive influence on the perceived ease of use. In particular, by a critical size of the triggering force, by a small spread of the same, by a clearly felt pressure point and by a critical length of the stroke in triggering the functions of the keyboard, this sensitivity is positively influenced. Little defined states or a spongy behavior of the keyboard when triggering the functions, a large dead time between two attacks as well as sudden force peaks are perceived as unpleasant.

Due to the low height of flat keyboards are the possible stroke - for example, compared to a computer desktop keyboard - set narrow limits. This fundamental disadvantage of flat keyboards must be additionally compensated by the other criteria.

The special feature of membrane keypads, which is the front foil trigger surface of the touch areas and top surface of the input unit at the same time, poses additional problems. On the one hand, the front film on the one hand in the Tastbereichen should have slightly flexible elastic areas and on the other hand, the front sheet should, however, be abrasion resistant and hard designed as a top surface. On the other hand, the continuous surface of the front foil makes it difficult to find the areas where the functions of the keyboard can be triggered. Surveys around these or in these areas, which are embossed in the front foil, although helpful in locating the areas, however, inevitably stiffen the front foil precisely in those areas which should actually be elastically flexible when released.

Although some progress has been made in terms of ease of use in membrane keyboards in recent years. For example, in the case of membrane doors, higher critical release forces in combination with a noticeable pressure point could also be achieved through the incorporation of dome-shaped switching elements - so-called crackling frogs. The operation of membrane keyboards is in practice still - in contrast to alternative keyboard types - uncomfortable.

Unpleasant to use keyboards lead to uncertainties in the operation and thus make it difficult to work directly with the device immediately. In devices - such as mobile phones, calculators or remotes - where on the one hand a comfortable and secure triggering keys of central interest and on the other hand, a low overall height would be desirable in principle, therefore, membrane keypads are despite their Exceptional flatness even in the lower price or quality segments only sporadically.

The invention is therefore based on the object to remedy the deficiencies of the prior art. So flat keyboards are to be proposed, which have an improved ease of use.

This object is achieved by a flat keyboard, in which the characterizing features of claim 1 are realized.

Further alternative or advantageous embodiments or developments of the invention are described in the features of the dependent claims.

A flat keyboard according to the invention is formed by a firmly joined structure of substantially flat material layers. The firmly assembled structure forms a ready-to-mount unit with at least one touch area. The flat keyboard has at least one surface-formed carrier material layer, at least one switching element and a substantially flat design, soft elastic rubber or plastic layer. At least one first and at least one second switching contact surface are applied to the carrier material layer. The two switching contact surfaces and the switching element are assigned to the touch area, wherein the switching element by a release force - automatically resetting - deformable. In such a deformation of the switching element creates an electrically conductive connection between the two switch contact surfaces, whereby the function of Keyboard is triggered. The release force is introduced via the front surface of the flat keyboard in the touch area. According to the invention, the soft elastic rubber or plastic layer is assigned to the switching element in such a way that the triggering force acts indirectly on the switching element via the soft elastic rubber or plastic layer.

The release force is usually exerted by a finger by being pressed in the touch area against the front surface in each case. The finger lies on the touch area and the pressure force is increased until the pressure force reaches the critical size of the release force. Now the switching element yields and is deformed. Immediately after this deformation of the finger is accelerated by exerting the pressure force in the direction of the keyboard and stopped a little later. In membrane keyboards according to the prior art, force peaks are exerted on the finger when stopping the membrane keyboard, which are perceived as unpleasant. According to the invention, however, these are now largely absorbed by the soft elastic rubber or plastic layer due to their deformation. The finger is now gently decelerated after the triggering of a function of the keyboard.

Since the rubber or plastic layer is also substantially flat - for example, with a material thickness of less than one millimeter - is formed, it can together with the switching element, the carrier layer and optionally with other layers to a common assembly ready unit - comparable to a membrane keyboard - firmly joined together become.

Particularly pronounced is the advantageous effect of the invention in flat keyboards, the switching elements are designed as domes, since these switching elements on the one hand is relatively large release forces and on the other hand a sudden, bulging buckling deformation own.

Keyboards with a rubber body, which has protruding, tower-shaped rubber blocks, although known from the prior art, but the protruding rubber blocks - which serve as buttons - alone already a height of several millimeters. Also, the rubber body is made of such a hard rubber material that material thicknesses of several millimeters - approximately comparable to the height of the rubber blocks - are required for a noticeable reduction of the force peaks. When installing the present as a separate part rubber body is also usually clamped between the printed circuit board with the meander-shaped switch contact surfaces and the housing wall of an electrically controlled device usually from the inside over fittings and thus the keyboard connected only at the final assembly to a keyboard unit. For this purpose, the rubber body must first be attached to the inside of the housing wall, wherein the rubber blocks must be pushed by recesses of the housing wall to the outside. The disadvantages of this procedure compared to attaching a present as a ready-to-install unit flat keyboard are obvious.

A development of the invention provides to apply a support disk made of a stiff material on the side facing away from the switching element of the soft elastic rubber or plastic layer in the touch area. Such a support disk can for example be applied by on the side facing away from the switching element of the rubber or plastic layer in the region of the trigger surface of the sensing area an epoxy resin is dropped. The surface tension automatically forms a front convex support disk. Thus, in the area of the triggering surface, the soft elastic rubber or plastic layer defines a very high rigidity, which can easily exceed the stiffness of a rubber mill block of hard rubber several millimeters thick. However, the elastic flexibility in the edge region of the sensing area still remains.

Although keyboards with rubber bodies are known, the tower-shaped rubber blocks are covered with a rigid layer of epoxy resin. Since the respective stiffness is already given by the rubber block of hard rubber, which is several millimeters thick, the layer of epoxy resin has the function of an abrasion protection of the usually printed button surface.

Another development of the invention provides a ram-shaped projection on the side facing the switching element. On the one hand, the dynamics of deceleration can be optimally optimized by means of a corresponding cross-sectional design of the extension. On the other hand, the release force is transmitted to the center of the switching element by an appropriately trained pestle-shaped extension in combination with a high rigidity in the touch area even with an eccentric force into the touch area. In particular, in the case of switching elements formed in the form of a dome, a substantially constant magnitude of the tripping force is thereby made possible and indeed - in contrast to membrane keyboards of the prior art Technology - regardless of the exact position of the release force within the sensing range.

An alternative embodiment of a flat keyboard according to the invention has a front side with a transparent viewing area, via which a display can be read. In a corresponding flat trained display even a flat keyboard would be conceivable, which has an integrated display that can be controlled via additional tracks. This would be a firmly assembled, ready to install control and display unit realized.

Figur 1

eine Draufsicht auf ein Ausführungsbeispiel einer erfindungsgemässen Flachtastatur,

Figur 2

eine vergrössert dargestellte Detailansicht des Ausführungsbeispiels aus Figur 1 in der Schnittansicht II-II und

Figur 3

eine vergrössert dargestellte Detailansicht des Ausführungsbeispiels aus Figur 1 in der Schnittansicht III-III.

The invention will be described in more detail below purely by way of example with reference to the figures of the drawing. Like parts in different embodiments, which perform the same functions, are provided below with the same designations or reference numerals. Show it:

FIG. 1

a top view of an embodiment of an inventive flat keyboard,

FIG. 2

an enlarged detail view of the embodiment of FIG. 1 in the sectional view II-II and

FIG. 3

an enlarged detail view of the embodiment of FIG. 1 in sectional view III-III.

The FIG. 1 shows a plan view of the front surface of an embodiment of an embodiment of the invention, for example, a flat keyboard for a hand-held laser rangefinder. At this Flat keyboard here are a small, square sensing area 3 "and a large, circular sensing area 3"'- each with different cross-sectional areas - provided. For example, the illumination of the display or the rangefinder of the laser rangefinder can be operated via the square scanning area 3 "and the circular scanning area 3"'.

Within the square sensing area 3 "and the circular sensing area 3" 'is a square support disk 6 "and a circular support disk 6"', here each made of transparent epoxy resin. Outside of the touch areas 3 "and 3" 'is a trained as a polycarbonate film cover layer 8, in the two recesses for the two support plates 6 "and 6"' are provided. The material of the cover layer 8 can be selected according to the specific requirements for a cover surface, for example a high abrasion resistance. It is even possible to use the same material for the cover layer and the housing of the laser rangefinder and to obtain a uniform, quiet-looking device surface. Between the two support disks 6 "and 6" 'and the cover layer 8, a part of a rubber or plastic layer 5 formed here as a sprayed silicone mat is visible. The two support disks 6 "and 6" 'and the cover layer 8 here essentially form the front surface of the flat keyboard.

FIG. 2 shows a first detailed view of the embodiment FIG. 1 which represents the vicinity of the square touch area 3 "in the sectional view II-II, the square touch area 3" becomes here centrically initiated a release force 4 on the front surface.

In the illustrated section, the exemplary embodiment has a carrier material layer 1 formed as a PET film, a spacer film 12, the soft elastic rubber or plastic layer 5 formed as a silicone mat, the cover layer 8, the square support disk 6 ", a fastening layer 9, two adhesive rubber adhesive films 13 on both sides , a fixing foil 14 and a switching element 2 embodied as a dome. Four first buttons and a second button with the respective associated conductor tracks, which are applied together here on the carrier material layer 1, are shown in FIG FIG. 2 not visible.

In a conventional manner, the attachment layer 9 is here as a two-sided adhesive film - for example, with a film thickness of 0.05 millimeters - formed. On the one hand, it is adhesively joined to the substrate layer 1 and on the other hand, a protective paper is attached, which is removed when installing the flat keyboard.

Also in a known manner, the carrier material layer 1 as a PET film - for example, with a film thickness of 0.1 millimeters - and formed with the spacer sheet 12 - for example, with a film thickness of 0.22 millimeters - glued together. How out FIGS. 2 and 3 can be seen, in each case a recess for each switching element 2 is here concentric to each of the Tastbereiche 3 "and 3"'provided in the spacer sheet 12. In the respective recess a switching element 2 is inserted in each case so that the switching element 2 rests on the four first switching contact surfaces. The switching element 12 is locally fixed here via the fixing film 14, which is adhesively joined together with the spacer-retaining film 12.

According to the invention, the essentially flat rubber or plastic layer 5 is assigned to the switching element 2. About this soft elastic rubber or plastic layer 5, the release force 4, which is introduced via the front surface, indirectly on the switching element 2. About one of the rubber adhesive films 13 here the rubber or plastic layer 5 is adhesively joined together with the fixing.

The rubber or plastic layer 5 embodied here as a silicone mat has a different layer thickness and in the center of the touch region 3 "has a pusher-shaped projection 7 which is directed against the switching element 2. By means of this pusher-shaped projection 7, the indirect initiation of the triggering force 4 becomes directly in the center This ensures the constancy of the magnitude of the tripping force.

Here, the layer thickness is, for example, 0.75 millimeters outside of the touch region 3 ", the layer thickness being, for example, 0.6 millimeters under the support disk 6" and about 1 millimeter in the area of the pestle-shaped extension 7. The area of the silicone mat beneath the support disk 6 "is connected to the area outside the touch area 3" via a circumferential web-with a layer thickness of, for example, 0.25 millimeters. About the second rubber adhesive film 13 here the cover sheet 8 is connected to the rubber or plastic layer 5.

FIG. 3 shows a second detail view of the embodiment FIG. 1 showing the vicinity of the circular touch area 3 "'in sectional view III-III FIG. 2 Here, too, the periphery of the novel flat keyboard and the connection of the conductor tracks 10 are shown. Also, the triggering force 4 is introduced here eccentrically in the circular sensing area 3 "'.

The soft elastic rubber or plastic layer 5 extends in the periphery of the flat keyboard laterally encircling the firmly assembled foil package of substrate layer 1, spacer sheet 12, fixing 14 and rubber adhesive films 13 and is hereby joined directly to the attachment layer 9 in the periphery directly. The rubber or plastic layer 5 and the attachment layer 9 encapsulate the interior of the flat keyboard in a hermetically sealed manner. Such a trained flat keyboard is particularly suitable for a tight installation in a housing from the outside. The recess in the attachment layer 9 for a passage of the conductor tracks 10 is to be provided with advantage within the periphery.

Through the support disk 6 "'and 6" it is possible to realize touch areas 3 "' and 3" with very different cross-sectional areas (see FIG. 1 ). In contrast to the prior art, the switching elements 2 assigned to the touch areas 3 "and 3"'each have the same embodiment and the same dimensions. As a result, substantially the same tripping forces 4 with identically formed pressure points are produced for differently sized touch areas 3 "and 3"' allows, which increases the ease of use.

The formation of a soft elastic rubber or plastic layer with a pestle-shaped extension in combination with the application of a stiff support disk allows for triggering a substantial insensitivity to an eccentric introduction of a triggering force in a tactile area. This is particularly advantageous in the case of large-area scanning areas. This makes a further contribution to increasing the ease of use of a flat keyboard possible.

The surface of the soft elastic rubber or plastic layer 5 below the support plates 6 "and 6"'can before applying the support plates 6 "and 6"' in a conventional manner with - for example, in FIG. 1 visible - symbols are printed.

Claims (11)

1. Flat keypad for operating an electrically controlled device, for example a hand-held laser distance meter, with

   - a carrier material layer (1), formed as a sheet, on which first switching contact areas and second switching content areas have been applied,

   - switching elements (2) formed in an electrically conducting manner and like snap-action contact lugs, by means of which the first and second switching contact areas assigned to them can be connected to one another in an electrically conducting manner under the action of triggering forces (4), the switching elements (2) being formed in a dome-shaped manner and such that they can be deformed by the triggering forces (4), while reverting of their own accord,

   - key regions (3", 3"'), which are respectively assigned to the switching elements (2) and to which the triggering forces (4) are introduced via a front area of the flat keypad during operation,

   - the carrier material layer (1) and the switching elements (2) being securely joined together with further material layers of a substantially two-dimensional form to form a unit ready for assembly,

   characterized in that
   a layer of soft elastic rubber or plastic (5), for example silicone foam, covering the switching elements (2) and having substantially the same two-dimensional extent as the carrier material layer (1), is provided, so that the triggering forces (4) applied to the key regions (3", 3"') via the layer of rubber or plastic (5) act indirectly on the switching elements (2).
2. Flat keypad according to Claim 1, characterized in that the switching elements (2) are connected to the layer of rubber or plastic (5) substantially centrally with respect to the key regions (3", 3"'), substantially at the crown of the dome.
3. Flat keypad according to Claim 1 or 2, characterized in that the layer of rubber or plastic (5) has in the key region (3", 3"') an area, if appropriate of a flat form, on which a supporting disc (6" , 6"'), if appropriate of a frontally convex form, of a material that is rigid in comparison with the layer of rubber or plastic (5), for example epoxy resin, has been applied.
4. Flat keypad according to any one of the preceding claims, characterized in that the layer of rubber or plastic (5) has a differing layer thickness and is formed such that, particularly in the peripheral region of the key region (3", 3"'), it is thinned in a web-like manner.
5. Flat keypad according to Claim 4, characterized in that, in the central region of the key region (3", 3"'), the layer of rubber or plastic (5) has on the side facing the switching element (2) a plunger-shaped continuation (7), which rests directly or indirectly on the switching element (2).
6. Flat keypad according to any one of the preceding claims, characterized in that a number of key regions (3) with different cross-sectional areas are provided, the switching elements (2) assigned to the key regions (3", 3"') having the same embodiment and the same dimensions.
7. Flat keypad according to any one of the preceding claims, characterized in that a hard outer layer (8), for example a sheet of polycarbonate, which has clearances for the key regions, has been applied frontally on the layer of rubber or plastic (5).
8. Flat keypad according to any one of the preceding claims, characterized in that an attachment layer (9), for example an adhesive film, forms the rear side of the flat keypad.
9. Flat keypad according to Claim 8, characterized in that the layer of rubber or plastic (5) is connected all around to the periphery of the attachment layer (9) in a waterproof manner.
10. Flat keypad according to Claim 9, characterized in that conductor tracks (10) to the switching contact areas are led through a clearance lying within the periphery.
11. Flat keypad according to any one of the preceding claims, characterized in that the front side of the flat keypad has a transparent viewing region, via which it is possible to read off a display, which if appropriate is securely joined together with the flat keypad to form a unit.

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