DE20307486U1 - Front film for a film covered keyboard includes backing blocks with recesses for snap disks to fit contour of keys and prevent excessive deformation - Google Patents

Abstract

The front film (1) of thermoplastic or deep-drawn material has backing blocks (2) attached on the underside at the position where deformation is to take place to form the keys. The blocks (2) have recesses (6) to accept integrated snap disks (8) or LEDs. The sides of the block act as guide surfaces to ensure vertical movement of the keys. The block (2) is slightly smaller but deeper than the deformation of the film. The depth of the recess (6) corresponds to the compressed height of the disk (8). The block (2) is attached with adhesive (3) and made by injection molding or cut from sheet material.

Description

Richard Wöhr GmbH

Graefenau 58 - 60

75339 Hofen

18.04.03 Design and/or front films made of thermoplastic or cold-stretchable plastic

The invention relates to design and/or front films made of thermoplastic or cold-stretchable plastic, with the aid of a negative molding tool, in which the film has fillers at the points that are deep-drawn, the contours of which are approximately the same and/or the same as the contour of the deep-drawing cavities, but whose profile thickness is significantly higher than the profile depth of the deep-drawing cavities and which are arranged and aligned in accordance with the deep-drawing cavities, wherein the fillers have a key cap integrated on their underside, which has a recess in the shape of the snap disk and/or milled outs and/or recesses for LEDs, wherein the contour of the snap disk recess is slightly larger than the outer shape of the snap disk and the height of the recess corresponds approximately to the height of the pressed-together contacting snap disk, so that when the design and/or front film is used with a film-covered keyboard based on a snap disk, the filler simultaneously serves as a stop against damage and impermissible pressing through of the snap disk.

DE 38 40 542 C1 and DE 37 27 926 C2 disclose deep-drawing processes for films or thin plates made of thermoplastic or cold-stretchable plastic and formed using known vacuum and compressed air processes. Deep-drawing tools with metal matrices are used for this purpose, in which the cavities forming the negative molds are either cast or machined.

DE 198 27 550 A1 discloses a method for producing partially reinforced plastic components, in which heat-formable reinforcing materials containing fibers with a length of > 1 mm are used to reinforce the partially reinforced component areas. However, these components are not used as decoration and/or front films.

Furthermore, deep-drawing tools for deforming films are known in which the matrix consists of one and/or several superimposed plates made of dimensionally stable plastic, in which the cavities are arranged in the form of cut-out openings.

The films produced using such processes are used, among other things, as design and/or front films for film-covered keyboards, whereby the deep-drawn profiles serve as positive elevations for the manually operated keys of the film-covered keyboards.

To stabilize and better protect against these films from being pushed through, there are known ways of providing the deep-drawn profiles with fillers that are subsequently cast and/or inserted into the hollow profiles after the molding process. These processes are expensive and complicated.

From DE 198 51 731 C1 a deep-drawing process is known in which the film is provided with fillers at the points where the deep-drawing profiles are produced before deep-drawing, wherein the contours and profile thicknesses of the fillers are each designed to correspond at least approximately to the contours and/or profile depths of the deep-drawing cavities into which they are sunk during the deep-drawing process.

The disadvantage of using these films on keyboards covered with film is that the function of the keys is impaired by the cast cavities and that the snap domes are not fixed in position and can be pushed through. In addition, the processes are very complex and expensive to use.

The invention is therefore based on the object of creating films of the type mentioned at the outset which can be produced in a simple and cost-effective manner by means of deep-drawing forming processes, which do not affect the function of the keyboard when the film is used in film-covered keyboards based on snap disks and which ensure that the snap disk cannot be pushed through and that the snap disk is fixed in position.

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This object is achieved according to the invention in that the film to be deformed, before it is stretched onto the die of the deep-drawing tool, is provided with filler bodies at the points where the deep-drawing profiles are created, the outer contour of which corresponds approximately to the outer contour of the deep-drawing cavities and the profile thickness of which is significantly greater than the profile depth of the deep-drawing cavities, and wherein the underside of the filler bodies has additional recesses for the snap-action disks and the contour of the recess is slightly larger than the contour of the snap-action disk and the height of the recess is designed such that the filler body designed as a touch cap serves as a stop when the snap-action disk is actuated and thus the height of the recess corresponds approximately to the height of the pressed-together snap-action disk, and in addition, milled recesses and/or light-guiding chambers for LEDs are present on the underside of the filler bodies.

The main advantage of this design is that the film only needs to be cut to size after being removed from the deep-drawing tool and that the snap disks are fixed in position in the filler bodies and cannot be pushed through.

It is advantageous that the fillers are firmly fixed to the film by means of an adhesive and/or glue.

An improvement in the tactile behavior is achieved by designing the filler body in such a way that it simultaneously functions as a key cap for guiding and limiting the key stroke of the snap disk.

It is advantageous if the filler is the same size in the upper area adjacent to the film and is adapted to the shape of the deep-drawing cavities and has an edge in the area adjacent to the film and is then designed with the remaining height in the area of the edge.

The invention is explained in more detail using some embodiments, some of which are shown schematically in the drawings. It shows:

Fig. 1: Section through a foil with filler and integrated touch cap for the snap domes before deep drawing

Fig. 2: Section through the foil with filler and integrated touch cap for the snap domes after deep drawing

Fig. 3: Design and/or front foil for foil-covered keyboard

Fig. 4: Filler in section with cutout for LED

Fig. 5: Top view of a filling body with light guide chamber for LED and recess for snap disk

Fig. 6: Section through a multi-stage packing

Fig. 7: Section through a filler with convex surface and optical effect for LED

Fig. 8: Section through a membrane keyboard with a probe integrated in the filling body and guided in the spacer layer

Figure 1 shows a section through a film with a filler and integrated recess for the snap disks before deep drawing. The base film made of polyester 1 has fillers 2 that are firmly fixed to the base film 1 by means of an adhesive layer 3. The outer contour of the fillers 4 is cylindrical. A recess 6 is integrated on the underside of the filler 5, the outer contour 7 of which is slightly larger than that of the snap disk 8. The depth 9 of the recess 6 corresponds approximately to the height of the compressed snap disk.

Figure 2 shows a section through a film with a filler and integrated recess for the snap-on disks after deep-drawing. The base film 1 has deep-drawing profiles 10. The fillers are somewhat smaller in terms of contour 4 than the contour of the deep-drawing profiles 10. The height 11 of the fillers is significantly higher than the height 12 of the deep-drawing profiles 10. The underside of the filler has recesses 6, the outer shape of which corresponds to the contour of the snap-on disk and is somewhat larger than the shape of the snap-on disk, as well as light-guiding chambers 33 for the LEDs.

Figure 3 shows the design and/or front foil for foil-covered keyboards. The foil 1 has deep-drawn profiles 10 that are raised on the foil 1 and mark positions for buttons 13. The deep-drawn profiles 10 represent elevations in the form of the domes 14 on the covering foil 1 and are circular in plan and in the shape of a spherical segment. The middle domes 15 on the foil have a square plan with rounded corners, being flat at the top and convexly curved at the edge with a curvature of approx. 90°. The logo 16 is in the form of a glass.

Figure 4 shows a cross-section of a filler body with a cutout for LEDs. The filler body 17 has a convex surface 18 and a recess 19 on the underside in the shape of the outer contour of the snap disk, whereby the shape of the recess is slightly larger than the contour of the snap disk and the height of the recess 20 is designed so that when the snap disk is actuated, the filler body, designed as a button cap, serves as a stop. In addition, cutouts 21 for LEDs are integrated on the underside.

Figure 5 shows a top view of a filling body with a light-guiding chamber for LED and a recess for a snap-action disk. A light-guiding chamber 23 is integrated on the underside of the filling body 22, as well as a recess 19 in the shape of the outer contour of the snap-action disk, whereby the shape of the recess is slightly larger than the contour of the snap-action disk and the height of the recess 20 is designed such that when the snap-action disk is actuated, the filling body, designed as a key cap, serves as a stop.

Figure 6 shows a section through a multi-stage filling body. The filling body 24 has a spherical dome 26 on the upper side 25 and a cylindrical guide 27. The recesses are again integrated on the underside.

Figure 7 shows a section through a filling body with a convex surface and optical effect for LEDs. The filling body 24 is made of a clear and/or transparent and/or translucent material.

Figure 8 shows a section through a membrane keyboard with a touch head integrated in the filler and guided in the spacer layer. The filler 24 is designed so that it can be viewed as a touch head and is guided vertically in the recess 25 of the spacer layer 26. On the underside 27, the filler has the recess 28 for the snap disk. The contact-making snap disks 29 are inserted into the recesses 25 of the spacer layer 26 and fixed in position. The covering design film 30 with the raised areas 31 is laminated to the switching film 32 with the spacer layer 26.

Claims (7)

1. Design and/or front foils made of thermoplastic or cold-stretchable plastic with the aid of a negative mold, characterized in that the foil has fillers at the points that are deep-drawn, the contours of which are approximately the same and/or the same as the contour of the deep-drawn cavities, but whose profile thickness is significantly higher than the profile depth of the deep-drawn cavities and which are arranged and aligned in accordance with the deep-drawn cavities, the fillers having a key cap integrated on their underside, which has a recess in the shape of the snap disk and/or milled recesses and/or light guide chambers for LEDs, the contour of the snap disk recess being slightly larger than the outer shape of the snap disk and the height of the recess corresponding approximately to the height of the pressed-together contacting snap disk, so that when the design and/or front foil is used with a foil-covered keyboard based on a snap disk, the filler simultaneously serves as a stop against damage and impermissible pressing through of the snap disk. 2. Design and/or front films made of thermoplastic or cold-stretchable plastic according to claim 1, characterized in that the key caps serve for vertical guidance of the filling bodies. 3. Design and/or front films made of thermoplastic or cold-stretchable plastic according to one of the preceding claims, characterized in that the fillers are firmly connected to the film. 4. Design and/or front films made of thermoplastic or cold-stretchable plastic according to one of the preceding claims, characterized in that the filling bodies are produced as injection-molded parts. 5. Design and/or front films made of thermoplastic or cold-stretchable plastic according to one of the preceding claims, characterized in that the filling bodies are made of sheet material. 6. Design and/or front films made of thermoplastic or cold-stretchable plastic according to one of the preceding claims, characterized in that the film is made of polycarbonate or polyester. 7. Design and/or front films made of thermoplastic or cold-stretchable plastic according to one of the preceding claims, characterized in that the film is a metal foil.