FR2723454A1 - Flat keyboard for radiotelephones, calculators or facsimile machines - Google Patents

Abstract

The flat keyboard has its face (1) divided into zones (2) that define keys. Behind each key is a detector (12) responding to pressure on the key. A light source (11) is embedded in the region of the centre of the key grid. Light diffusers (5) round the light source carry light to the underside of keys that are to be illuminated. The light diffusing blocks (5) fill the space between the underside of the key and the detector (12), transmitting motion from the key to the detector. The light diffuser is a translucent material with an elastomer layer on top or bottom faces. The detector is a deformable bubble cap.

Description

Flat data entry keyboard.

  Most electronic terminals have a keyboard that allows the user to control the terminal. We can think for example of a

  radiotelephone, calculator or fax machine.

  A flat keyboard has a front face, with a plurality of zones delimiting keys, and a corresponding plurality of key activation detector means arranged behind the front face and respectively associated with the keys. In the event of insufficient ambient lighting, the keys or their inscriptions, characters or other markers that they can carry are barely visible, so

  that the keyboard is difficult to use and that the risk of error is high.

  The present invention aims to overcome this drawback.

  To this end, it relates to a keyboard of the type mentioned above, characterized in that it comprises at least one light source and means for diffusing the light from the source to illuminate from the rear at least

  some of the front panel keys.

  Preferably, the diffusion means comprise a housing for receiving the light source and there are provided, between the front face and the detectors, the diffusion means and spacing means respectively of shapes.

appreciably complementary.

  The invention will be better understood using the following description of the form

  preferred embodiment of the flat keyboard of the invention, with reference to the accompanying drawing, in which: - Figure 1 is an exploded perspective view of the keyboard of the invention and

  - Figure 2 is a sectional view of the keyboard, on an expanded scale, along line II-

11 of Figure 1.

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  The keyboard comprises a front face 1 here comprising four zones 2, delimiting keys and each bearing a particular inscription 3, such as a character, locating the key. The front face 1 consists of an elastic layer of a translucent material and the inscriptions 3, as well as a frame 4

  delimiting the keys, are painted there.

  A layer 5 of translucent elastomeric material is disposed behind the front face 1 and comprises a housing 6, constituted here by a through hole, to receive a light-emitting diode, or LED, 11, unique in this example of a keyboard of reduced size, but which could, for a larger keyboard,

  exist in several copies distributed in layer 5.

  Layer 5 has, here, a cut corresponding substantially to the shape of the

keys 2.

  A printed circuit board 10 carries the LED 11, permanently supplied, as well as elastic deformable metal cups 12, respectively associated with the keys and arranged opposite them, behind the layer 5. When it is crushed, a cup 12 establishes an electrical contact allowing passage, by a ribbon cable 13 of keyboard interface,

  of a particular signal to the cup 12 concerned.

  In order to avoid accidental sinking of the cups 12, a rigid layer 14 forms a spacer between the printed circuit 10 and the front face 1, to guarantee the existence of a space between them. As shown in FIG. 1, the spacer layer 14 has a shape of cut complementary to that of the translucent layer 5, so that these two layers 5 and 14 overlap and

  extend substantially in the same plane.

  The operation of the keyboard will now be explained.

  The overlapping translucent layer 5 and the spacer layer 14 are mounted

  sandwiched between the front face 1 and the printed circuit 10.

  The translucent layer 5 has the function of capturing the light from the LED 11 and diffusing it over the rear part of the front face 1. In this example, this

  diffusion is in fact a distribution limited to zones 2 of the keys.

  Static keys could have been provided, detecting the presence of a finger, for example by capacitive effect, but, here, it is a tactile keyboard, the actuation of which is mechanical. Therefore, the material of the front face 1 is elastically deformable so that the cups 12 detect the sinking

  keys via layer 5.

  The translucent layer 5 therefore has, here, a second function, which is to transmit the sinking force transmitted by the key, that is to say that it is elastically deformable locally, like a flexible tongue, and,

  in this example, it can even crash elastically.

  The light striking the front face 1 from behind crosses the latter through the zones 2, excluding the places having the inscriptions 3, the shape of which

  thus appears to the user, here in dark on a light background.

  It will be understood that the difference in optical transparency between the inscriptions 3, with their frame 4, and the rest of the key or frame 4, which creates an optical contrast making the keyboard readable, could be obtained otherwise. For example, these are the inscriptions 3 which could be transparent and, the rest of the front face 1, opaque. Likewise, a color filter could create the desired transparency difference in the wavelength range. An optical network in the form of streaks would, again, locally deflect the light and thus determine the transparency of certain

portions of the front panel 1.

  In view of the examples above, it will be understood that the transparency of portions of the front face 1 can be determined by localized deposition, on one side or

  the other, a layer with specific transparency and / or by etching.

  As has been explained, the function of layer 5 is to collect the light from the light source in order to diffuse it over the rear of the front face 1. As it is a question of diffusing and deflecting laterally the light injected into the plane

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  of the diffusion layer, it could also be achieved by means of a layer of transparent material comprising, on its face opposite to the front face 1, a distributed etched network ensuring the diffusion and the reflection substantially at right angles to a multitude of elementary beams emerging laterally from the diffusion layer to illuminate the rear of the front face. Likewise, the front face and the diffusion layer could form a single element. The inscriptions would for example be arranged on the surface, external side accessible by the user, or even on the other side or even in the mass, in order to locally modify the intensity and / or the nature of the light.

  reflected by the rear face, if this is the case, or diffused by the material.

  In order to ensure better uniformity of distribution, provision may be made for

  cover between the light source and the front panel 1.

  The light-generating source can also be placed outside the keyboard and connected by a light pipe, the end of which acts as a

light source.

Claims (8)

  1. Flat data entry keyboard comprising a front face (1), with a plurality of zones (2) delimiting keys, and a corresponding plurality of means (12) for key activation detectors arranged behind the front face (1 ) and respectively associated with the keys, keyboard characterized by the fact that it comprises at least one light source (11) and means (5) for diffusing the light from the source (11) for back lighting at least   some of the buttons on the front panel (1).   2. Keyboard according to claim 1, in which the diffusion means (5)   extend between the front face (1) and the detector means (12).   3. Keyboard according to claims 1 and 2, wherein the diffusion means   (5) comprise a diffusion layer of translucent material.   4. Keyboard according to claims 2 and 3, wherein, the keys being of   push-in type, the detector means (12) detect the push-in of the   keys via the diffusion means (5).   5. Keyboard according to claim 4, in which the diffusion means (5)   have a layer of elastomeric material.   6. Keyboard according to one of claims 1 to 5, wherein the means for   diffusion comprise a housing (6) for receiving the light source (11).   7. Keyboard according to one of claims 4 to 6, wherein the means   detectors include a deformable cup (12).   8. Keyboard according to one of claims 1 to 7, in which it is provided, between   the front face (1) and the detectors (12), the diffusion means (5) and spacing means (14) respectively of substantially complementary shapes.