WO2009022124A1

WO2009022124A1 - Illuminated keyboard

Info

Publication number: WO2009022124A1
Application number: PCT/GB2008/002724
Authority: WO
Inventors: Abraham Engelhard
Original assignee: Babel Tech Limited
Priority date: 2007-08-11
Filing date: 2008-08-11
Publication date: 2009-02-19
Also published as: GB0715680D0; GB2445632B; GB2445632A

Abstract

A push to make switch assembly having a hollow push button and upper window through which light may be emitted of specific construction is provided. The switch assembly may be used in an illuminatable keyboard comprising a light source and a plurality of keys having optically clear upper faces, the keys being located in apertures in a mask interposed between the light source and the keys, the keys having a hollow structure so as not to obstruct light passing directly from the light source to the surface of the key.

Description

Illuminated keyboard

The present invention relates to an illuminated keyboard. In particular, the invention relates to an improved illuminated keyboard and a switch assembly suitable for used in such a keyboard, for example, a computer keyboard.

The computer keyboard is ubiquitous and comprises an array of similar, push-to-make switches having caps suitable for pressing with a finger so as to actuate the switch. The ability of a user to effectively operate a keyboard is dependent upon a large number of factors, particularly accurate visual recognition of a key. This is particularly so for the many people who cannot touch type and therefore need to visually identify a key at each keystroke. The speed at which such people can type can therefore potentially be improved by designing a keyboard and individual keys so as to facilitate key location and identification.

A group of people for whom the location and identification of keys on a keyboard is a particularly limiting aspect in their ability to type, or to type with any speed, is people with dyslexia. Dyslexia is characterised by difficulties with phonological processing, rapid naming, working memory, processing speed and the automatic development of skills that are unexpected in relation to an individual's other cognitive abilities. It has been established that the colour of an object and its background, such as that of a word or letter, can influence the correct identification of that object for a dyslexic person. It is therefore known that providing keyboards with coloured keys can assist people in learning typing (for example US 2003052863). It is also suggested that it may assist those with dyslexia. However, the colour or colour combination that is most effective may vary from person to person and even over time for a particular person.

It is also known to illuminate keys on a keyboard and a person may find keyboard illumination of assistance in improving typing speed, such as in low light conditions. A large number of methods of key illumination are known:

US 4,365,903 (Siemens) discloses an illuminated switch assembly for use as a key. The assembly comprises a light emitting diode (LED) housed in a key cap and wired to a main body of the switch assembly by flexible wires. Such devices are unreliable as a keyboard is typically rated for millions of key presses and flexible wires are prone to eventually break. The switch is also complex to produce. A more recent example of this approach can be found in FR 2868150.

GB 2 235 295 (Technophone) discloses a keypad illuminated overall by a number of LEDs disposed behind a transparent backplane or plate having lenses and reflectors so as to guide light across the backplane so as to give overall illumination of a keypad. This is one example of numerous keyboard illumination techniques that depend upon light being channelled perpendicular to the axis of keys, i.e. parallel to a keyboard surface. Examples include US 2004/0257829 and NL 1021474 (Samad). Such illumination is difficult to provide evenly over a surface and requires that the keyboard as a whole is illuminated. In particular light emanates from the edges of the planar light guide, and also around the base of keys distracting the eye from the centre of a key where a key identifier symbol is usually placed. This detracts from illumination of individual key caps and so does not improve key location and identification except in so far as a keyboard can be better seen under poor light conditions.

GB 2 150 722 (Muller) discloses a switch assembly for use as a key. The assembly comprises a liquid crystal display (LCD) incorporated into a base portion of a key assembly having a moveable cap or lid which covers the LCD and is useable to actuate a switch. Such assemblies are complex, costly and require extensive wiring to enable an LCD. Such assemblies are more recently available as illuminated colour LCDs. In addition to complexity, each switch acts as separate light source and therefore it is extremely difficult to provide such a keyboard with equal illumination intensity across an array of keys and furthermore equal coloration across an array of keys. Any differences in illumination intensity or colour will be readily picked up by the eye and serve to distract the user from visually selecting a correct key. However, such LCD keyboards are not intended for such uniform use and are intended rather for displaying different coloured pictures across keys of a keyboard, such keyboards are therefore even more difficult for a dyslexic person to use and can hinder speed of recognition as the keyboard layout inevitably departs for the familiar appearance of an 'IBM' keyboard. Further, the processing power required to actuate and update an array of LCD keys is very large and greatly offsets the power efficiency of such displays in themselves, this makes the supply of power to a keyboard through a computer keyboard connection alone impractical. EP0644565 (Ford) and US 6,179,432 (Compaq) disclose a keyboard having an electroluminescent back panel to provide overall illumination to a keyboard. As above overall illumination serves a different purpose than selective key illumination and does not facilitate key location and identification beyond the benefits of general illumination.

US 5404133 (Alps) discloses a luminous key top or cap illuminated from a separate light source. However, no disclosure as to how the key top can be incorporated into a switch assembly, such as one suitable for use in a keyboard is made.

There is therefore a need for a self illuminatable key suitable for use in a keyboard wherein a light source for illuminating one or more keys is remote from moving parts of the keys yet enables light to directly illuminate a key cap, facia or window portion of a key only. The problems of complexity and durability associated with having a light source incorporated into a moving part would thus be addressed. The problem of variation in light intensity and, optionally, colour across several keys is also addressed. The problem of the loss of light intensity and evenness of light distribution caused by light channels would thus also be addressed. Further, there is a need for illumination of a key cap or facia only so as not to remove the distinctiveness of illumination by an overall background illumination. A key cap is a whole key top, a facia is an, in use, upper face of a key top, a window is a portion of a facia, particularly a portion on which a key designator may be placed for key identification.

There is further a need for an illuminated keyboard, i.e. a keyboard having self illumination, wherein the illumination is adjustable over a wide range of colour and/or intensity and optionally duration, so as to enable a spectrum of colour and/or a range of light intensities in illumination. There is further needed for a keyboard wherein the colour of illumination can be dynamically adjusted to suit the needs of a user. There is furthermore a need for a system of keyboard illumination which is self optimising for the needs of a user.

There is an associated need to provide a keyboard comprising illuminated keys against an un-illuminated back plane, so as to enhance the visual identity of each key. - A -

Objects of the present invention include addressing the aforementioned needs and problems.

The present invention in its various aspects is as set out in the accompanying claims.

A further embodiment of the invention provides an illuminated keyboard comprising a light source and a plurality of keys having optically clear upper faces, in the form of a whole upper face that is clear or in the form of a window having an opaque frame or surround, such as opaque key cap side faces; the keys being located in apertures in a mask interposed between the light source and the keys, the keys having a hollow structure so as not to obstruct light passing directly from the light source to and through a key cap comprising the, in use, upper surface of the key.

A key suitable for use in a keyboard is a key having an upper face or window on which a character or other symbol or message may be placed so as to differentiate the function of one key over others. These features may be printed on the key caps, such as on the clear upper face or window and/or they may be in relief, such as an upstanding or embossed, or indented or engraved, feature.

The keys are each associated with a separate resilient means in the form of at least one leaf spring for restoring the keys and associated switch mechanism to a start position after actuation; the resilient means may be integral to each key cap. Use of a shared resilient means between keys is deficient, particularly when used for closely spaced keys as the depression of one key can result in a reduction in restoring force for adjacent keys, thus increasing the risk of accidental key presses of adjacent keys. The resilient means of the present invention comprise at least one leaf spring. The resilient means preferably comprise a plurality of leaf springs located symmetrically about the hollow central structure of the key so as not to obstruct light and to resiliently bias the key evenly. The resilient means thus configured enables a positive key action to be obtained from a key having a hollow structure.

Alternatively the resilient means may be separate from, but specific to, each key as part of an overall switch assembly. Such resilient means is preferably in the form of an undulating leaf spring. That leaf spring is preferably in the form of a loop, such as a loop that circumscribes or at least encircles walls of the key, such as walls in the form of a tube about the hollow central structure of the key. The keyboard is preferably a computer keyboard, such as a keyboard suitable for use with a desktop personal computer. The keyboard is preferably of a standard QWERTY (UK & USA) or AZERTY (France) layout. The keyboard typically comprises a plurality of keys set out in an array of rows of keys in offset or staggered columns. The keyboard is preferably configured so that it communicates with a desktop or Personal Computer ('PC) computer and also receives power by means of a single cable terminating in an Universal Serial Bus (USB) or 6-pin "mini-DIN" also known as a "PS/2" or an "AT" connector.

In some instances, such as where a particularly large keyboard, or a keyboard requiring bright illumination a power supply separate from the keyboard or computer may be used, such as a DC power supply. This provides a significant benefit in reducing keyboard complexity, set-up, power supply and user acceptability over known illuminated computer keyboards which consume a greater amount of current than can be supplied using such standard connector types (typically 50OmA maximum) such as because of using separate illumination means for each key. Connection of a keyboard of the invention to a PC may act to initiate a system for setting up and optimising the keyboard illumination. A plurality of USB connectors may be provided for the purpose of drawing additional power from a computer system, thus overcoming the requirement for a separate power supply or limited illumination.

The keyboard may be illuminated by a light source for providing coloured light. The coloured light is preferably variable across the whole visible spectrum, optionally including white light. The coloured light is preferably of an intensity that can be varied for any given colour. Light intensity may be variable in relation to ambient illumination, such as may be detected by a detector mounted on the keyboard. The light source is preferably one or more Red Green Blue (RGB) light emitting diodes (LEDs). LED's are more energy efficient and durable than incandescent and photo luminescent light sources. The number of LED's is preferably lower then the number of keys, each LED sharing the illumination of a plurality of keys. This feature acts to even out variations in light colour and intensity so as to give a more evenly illuminated keyboard. To conserve power the LED's may be modulated, such as by use of a square wave power source. The power supplied to Red, Green and Blue components of an RGB LED may be modulated with different mark to space ratios so as to compensate for LED response times and thus conserve light output colour over a range of modulation frequencies and average mark to space ratios. This modulation of the power may be used to adjust the intensity of illumination.

The target luminous intensity of the keys as white light is 7.28 k lux (677 foot candelas). This light may comprise target intensities of red, green and blue light optimally distributed in target intensity of red at 2.86 k lux (266 foot candelas), green at 5.0 k lux (470 foot candelas) and blue at 1.0 k lux (99.4 foot candelas). These values have been found to provide optimal lighting from a RGB LED. The above target values may be expressed as target ranges of plus and minus 20% of the target values for a LED array having a 120 degree (the range 100 to 140 degree) viewing angle when placed at 25mm from (i.e. under) the optically clear upper face or window of the key caps.

The keys or switches of the present invention have optically clear upper faces or windows. By optically clear is meant a material can transmit visible light without appreciable loss in light intensity. Hence, transparent and translucent materials are considered optically clear. Translucent materials may be advantageously used to diffuse light emitted from a clear upper face or window of a key or switch assembly so as to enable viewing of keys at various angles from the vertical, such as in a keyboard, whilst maintaining an even light intensity to a viewer. Translucency may be obtained by providing a roughened surface to a clear upper face, such a roughening advantageously also provides improved tactile feel to the user aiding accurate key presses. Alternatively the clear upper face may be transparent.

The clear upper face may be planar or just a window portion of the fascia may be planar.

The clear upper face or, optionally a window portion thereof, i.e. having a surrounding frame may be concave or convex, preferably so as to provide a lens. A convex (i.e. dished) upper face is preferred so as to more accurately locate a finger tip on a key. A clear upper face configured as a divergent lens so as to spread light so as to enable viewing of keys with similar light intensity when at angles from the vertical, such as in a keyboard, whilst maintaining an even light intensity to a viewer. The angle from the vertical at which light is distributed will upon the focal length of the lens. The angle may be about 45° from the vertical; preferably the angle is about 30° from the vertical. The lens may be configured to be astigmatic, giving a light distribution at, say about 45° or more to the vertical to the left right and bottom of a keyboard array in use but less than 45° to the top of the array, say 10° or less. About means +/- 20°.

The clear upper face or window is preferably both concave and configured as a divergent lens. When individual switch assemblies are used together on a keyboard a mixture of concave and convex clear upper faces or windows may be used, preferably all configured as diverging lenses.

The illuminated keyboard of the present invention preferably comprises an optical mask to mask light from emerging between keys. The optical mask may be the support sheet, a switch membrane or a separate opaque layer having apertures therein so as to define a mask. The optical mask may be configured as an apertured, opaque (i.e. not optically transparent) sheet interposed between the light source or sources of the keyboard and key caps of the key(s). A mask or optical mask is a structure that does not transmit light; the mask is preferably a planar structure. Only one of the support sheet, switch membrane and mask need be opaque and act as a mask. Preferably a lower side of support sheet, or if the support sheet is transparent the mask or the switch membrane, is reflective to reduce light lost by light absorbtion by the mask.

The illuminated keyboard of the present invention preferably comprises a switch membrane typically comprising three layers. A base layer having a first wiring pattern and a supported layer having second wiring pattern, the layers sandwiching a resilient and electrically insulating and supporting separating layer. Those three layers each have coincident apertures with apertures in the support sheet, over which the membrane is secured. The apertures are for accommodating a switch assembly such as a tubular portion such as may be in the form of an insert portion or legs as herein described adjacent switching points. The upper layer having a second wiring pattern is arranged such that depression of a key resiliently compresses part of the second wiring pattern against part of the first wiring pattern to reversibly make an electrically contact for performing an electrical switching operation. The switch membrane may be transparent or may be advantageously opaque so as to obviate the need for a separate optical mask. The switch membrane of the present invention is preferably a single sheet (typically comprising several layers bound together) for ease of production. The sheet therefore comprises an aperture or apertures cut out in the membrane in order for the key to go up and down through the membrane and optionally further aperture or apertures to permit light to reach the facia of the key, if the membrane is opaque, from the on-board self illumination light source.

The illuminated keyboard of the present invention may comprise a keyboard housing or case, the case having at least a base and sides to accommodate on a further, upper, face an array of keys as herein described. Below the array of keys is preferably a printed wiring board supporting an array of LED' s for illuminating the keyboard, the LEDs are wired to the printed wiring board and associated control circuitry so as to, in use, enable the keyboard to be illuminated in a selected colour at a selected light intensity. Above the printed wiring board is a substrate material in the form of a rigid apertured sheet in which a plurality press-to-make electrical switch assemblies as herein described are arranged. The keys being configured to be resiliently biased upward from the substrate to a limit constrained by means of a stop on the switch body, such as a latching piece for latching a key into the substrate. Between the key body and the substrate is optionally located a switch membrane as herein described, other configurations are a printed wiring board/substrate combination in conjunction with a conductive key portion for forming a key contact. The switch membrane is retained in position by means of the resilient means of the keys compressing the membrane onto the substrate and also by the key bodies, legs or tubular portions such as may be in the foπn of an insert portion passing through the membrane. The keyboard further comprises a data transmission and power cable for communicating key press and other information, such as key board illumination state and ambient illumination intensity to a computing apparatus to which, in use, the keyboard is attached.

The illuminated keyboard of the present invention optionally comprises a press-to-make electrical switch assembly, the switch comprising i) a support sheet, such as a back plane, having an aperture therein for locating a pushbutton; ii) said push-button for manually operating the switch by means of pressure applied perpendicular to an optically clear upper face of the push-button so as to depress the push button towards the support sheet , the push-button being located, at least partially, in said aperture, the push button being retained at the rim of the aperture and the push-button having at least, but preferably, 4 side faces, two of said opposed side faces comprising a resilient means for providing a force to urge the push-button away from the support sheet and for restoring the pushbutton to a starting position after a switching operation and at least two, and optionally all, of said side faces each comprising at least one latch for retaining the push-button on the support sheet by means of latching to a side of the rim away from the upper surface of the switch ii) a switch membrane located on the same side of the support sheet as the upper side of the push button comprising a switching means capable of being operated by depression of the push button.

The side faces having resilient means and the side faces having the latch may be the same, said, side faces. The switch membrane is actuated (actuateable) by a boss on the pushbutton acting as a localised contact on the membrane at a switching point on the membrane. The push button comprises between 1 and 4 such bosses, preferably as pairs on opposed sides (see diagrams) of the push-button so as to allow for some skew on depression of the push button without compromising the registrability of a key press. Alternatively the switch membrane (of this and can be configured so as to require two bosses to impinge on the membrane before a key press is registered. This provides for a key that only registers when a very full and deliberate press is made. This is useful in situations where an accidental key press may be harmful or for people with limited manual dexterity where accidental contacts may be frequent. A keyboard of the invention may comprise a combination of such single and multiple (e.g. two) boss keys.

A keyboard according to the present invention may be used in a system comprising a computer wherein the computer is programmed to provide information relating to the illumination and optionally specific selection and operation of keyboard keys. For examples, overall colour, colour of a left and right side of a keyboard etc. may be selected. The programme may further provides control of one or more of the intensity of illumination, the colour of illumination and the duration of illumination of keyboard key criteria. The system is configured to operate by offering one or more a key selections and timing the response of a user in operating a key. The accuracy and speed of key operation is then correlated with the keyboard illumination and that criteria adjusted in response, such that, by means of an iterative procedure optimal keyboard illumination is obtained for a specific user under ambient lighting conditions.

The keyboard illumination system may comprise i) A keyboard as herein described; ii) A computer system linked to the keyboard for the inputting of information typed on the keyboard by a user, such as information from a predetermined test script designed to identify common typing errors, such as those associated with dyslexia; iii) A computer programme for monitoring the resulting key presses on the keyboard and at least one of the colour, intensity and duration of illumination of keys on the keyboard, iv) A further computer programme for correlating at least one of the frequency of key presses and the frequency of key press errors with the data monitored at iii). Errors may be determined by monitoring and recording uses of the back-space and/or delete keys of a keyboard, errors may also be determined by means of a spelling checker program. Error monitoring may be used intensively by means of a predetermined test script and it may be used during ongoing keyboard usage. Optimisation of illumination may be measured by a parameter such as a key presses per minute divided by key press errors made in that same time period, the higher such a parameter the better the illumination for a given operation, such as a test script. v) Means for adjusting the illumination of the keyboard according to predefined rules and adjustment of the illumination according to those rules, the rules using data from both of steps iii) and iv) to provide illumination adjustment with an expectation of influencing typing speed or accuracy. These means may be in the foπn of modulation of power fed to red, green and blue light sources that combine to provide the light source. Alternatively the light sources may be supplied with a constant but adjustable voltage or current for varying intensity, such as, for example, to provide different colours, vi) Steps iii), iv) and v) may be used repeatedly to iteratively to optimise keyboard illumination for the user as determined by one of both of the parameters frequency of key presses and the frequency of key press errors selected at iv) vii) A visual map, such as of CIE colour space may be provided on a monitor screen of the computer system whereon successive adjustments of illumination from step vi) are displayed to chart the progress towards optimising keyboard illumination, to illustrate colour optimisation changes over time, such as due to changes in ambient or background illumination. viii) The portrayal of information on a visual display unit or monitor screen may be adjusted as part if the system so that its portrayal or information (e.g. black characters on a green background etc.) corresponds to and is adjusted in conjunction with the keyboard illumination. The adjustment and optimisation of information portrayal may occur separately from the optimisation of keyboard illumination. ix) The illumination adjustment is an adjustment of one or more of colour of illumination, illumination intensity and illumination duration, preferably only of colour.

The system may further provide for storage and retrieval of the optimised conditions and association of those conditions with a user profile. A computer keyboard according to the present invention may therefore be optimally set-up for use by a user such as a dyslexic user. The system may optionally monitor the optimal user conditions over time. The system may further comprise a measure of ambient lighting conditions against which to calibrate and optimise a user profile. Hence, a user may operate a keyboard of the invention under a variety of conditions without having to redo the optimisation procedure on each use. The measure of ambient lighting conditions may be a user input (such as a choice between outdoors, indoor fluorescent, indoor incandescent illumination etc.) or a light sensitive electrical sensor such as photocell.

The switch assembly as herein described may further comprise an illumination means for illuminating the upper face of the switch from below the support sheet.

The present invention will now be illustrated with reference to the accompanying drawings, in which:

Figure 1 shows a first side elevation of a push-button actuator portion of a switch of the present invention;

Figure 2 shows a second side elevation of a push-button actuator portion of a switch of figure 1 the present invention; Figure 3 shows a plan view from below of a push-button actuator portion of a switch of figure 1 the present invention;

Figure 4 shows a first side elevation of a cap of push-button actuator portion of a switch of figure 1 the present invention;

Figure 5 shows a second side elevation of a cap of push-button actuator portion of a switch of figure 1 the present invention;

Figure 6 shows a plan view from below of a cap of a push-button actuator portion of a switch of figure 1 the present invention;

Figure 7 shows a first side elevation of a tubular portion in the form of an insert of a pushbutton actuator portion of a switch of figure 1 the present invention;

Figure 8 shows a second side elevation of a tubular portion in the form an insert of a pushbutton actuator portion of a switch of figure 1 the present invention;

Figure 9 shows a perspective view from above of an insert of a push-button actuator portion of a switch of figure 1 the present invention;

Figure 10 shows a perspective view from above of a push-button actuator portion of a switch of the present invention;

Figure 11 shows a side view of a press-to-make electrical switch assembly of the present invention;

Figure 12 shows a cross section of the side view of figure 7 of a press-to-make electrical switch assembly of the present invention;

Figure 13 shows a plan view of keyboard of the present invention;

Figure 14 shows a cross section along line A-A of figure 13; Figure 15 shows a cross section along line C-C of figure 13; and wherein

Figure 16 shows a side elevation of a key cap according to a second embodiment of the invention;

Figure 17 shows a side elevation of a key cap as figure 16 in conjunction with a spring element, according to a second embodiment of the invention;

Figure 18 shows a plan view of a spring for used in the second embodiment of the invention;

Figure 19 shows a side elevation of the spring of figures 17 and 18, according to a second embodiment of the invention;

Figure 20 shows a perspective view of the spring of figures 17 and 18, according to a second embodiment of the invention;

Figure 21 shows a perspective view of a key cap as figure 16 in conjunction with a spring element, according to a second embodiment of the invention;

Figure 22 shows a perspective view from below of Figure 21;

Figure 23 shows a keyboard of the second embodiment of present invention partially populated with key caps of that embodiment;

Figure 24 shows an end elevation of the keyboard of figure 23; and

Figure 25 which shows the arrangement of a light source inside the keyboard of figure 23 along the line A-A.

An embodiment of a press-to-make electrical switch assembly for use in a keyboard of the invention is as follows. Referring now to figures 1 to 6, the push-button or actuator switch portion 10 comprises a cap 12 and insert 14. Whilst this embodiment shows parts 12 and 14 as separate, it is also within the scope of the invention that parts 12 and 14 may for a single unit of the form shown in figures 1, 2 and 10, and that insert (14) may not necessarily be used in relation to the cap (12) by insertion, the insert (14) therefore also termed a tube in the present invention. The cap 12 comprises four tapered sides 20 and rounded corner portions 22 and a transparent optically clear upper face or window 40 of the push-button 24, which in use acts as an illumination zone. The sides 20 and corner portion 22 may be transparent but preferably and in this embodiment only the window 40 is transparent. Attached to two opposing sides of the cap 12 at a lower edge 26 of the cap are resilient means 28 for providing a force to urge the push-button away from a support sheet (not shown) and for restoring the push-button to a starting position after a switching operation. The resilient means are integrally moulded with the cap from an optically clear plastics material. The resilient means 28 are in the form of arcuate members attached to the cap at a centre portion and adapted to resiliently urge the push-button against a support sheet (not shown,) abutting ends 30 of the resilient means. At the centre portion is located a cylindrical boss 32 for, on actuating the pushbutton, pressing against a switch membrane (not shown) to reversibly make an electrically contact for performing an electrical switching operation.

The cap 12 and the insert 14 are preferably made from an injection moulded plastics material. The cap is preferably made from polypropylene and the insert from acrylonitrile butadiene styrene (ABS) thermoplastic.

The resilient means 28 is integrally moulded with the cap 12. However, the resilient means may be in the form of a metal leaf spring. Such a spring can be advantageously secured to the cap by means of the switch membrane contact boss 32.

The insert 14 is a square-section tube that is inserted into and retained within the cap 12 so as to form the push-button 10. The two part construction enables materials best suited for optical transparency and as a moving mechanical slider to be chosen separately, as well as reducing the complexity of a mould required to make a push-button as a single entity. The insert has two planar opposing sides 50 attached at corners 54 to two further opposing sides 52 having an upper edge 56 for retention, such as adhesive retention, in the cap 12. At a lower edge of sides 52 is a latch 60 on a lower portion or flap 62 of side 52 configured so as to enable the flap 62 to be resiliently distorted inward so as to enable latches 60 to enter into an aperture of a support surface and resiliently return so as to secure the push-button on the support sheet.

Referring now to figures 10, 11 and 12, the figures show a press-to-make electrical switch assembly of the present invention comprising a push switch 10 itself comprising a cap 12 and insert 14. The push switch is located in an aperture 64 of a support sheet 70 which has sides 76 (shown on an adjacent key for clarity) of fractionally larger internal dimensions to the external dimensions of the insert 14 so as to permit travel of the push button within the aperture 64. The push button is resiliently biased away from the support sheet by means of the resilient means 28, which are under compressive tension. Latches 58 engage the under side (i.e. latching to a side of the rim away from the upper surface of the switch) of the support sheet 70 to prevent the push button from being urged out of aperture 64. Area 74 is schematic shading to indicate the area in which further, adjacent, key caps may be present.

Interposed between the resilient members 28 of the push button 10 and the support sheet 20 is a switch membrane 80 as hereinbefore described. The switch membrane 80 has a portion 82 suitable for switch actuation by pressure of boss 32 on the membrane. The key having two bosses 32, the contact of either with the switch membrane 80 serving to register a key press.

The press-to-make electrical switch assembly of the present invention may further comprise (particularly when present as part of a keyboard) an illumination means, such as an LED 90. LED 90 is supported on a printed wiring board 92 which acts to support and supply power to the LED. The LED is a tricolour (or 'RGB') LED comprising component light emitting diodes capable of emitting red, green and blue light. The LED is configured such that a control circuit (not shown) such as a microcontroller enables independent supply of each component LED. A spectrum of coloured light may thereby be generated by the LED. The LED is disposed below the push button, i.e. on the side of the push button remote from the cap. Light emitted from the LED is generally stopped from exiting the switch assembly or keyboard by means of the light mask and a casing (not shown). However, light may pass through the inside of the push button 64 surrounded by reflective inside walls 62, 50 and the aperture 64 in sheet 70, and thus exit the switch assembly, for viewing by a user through the window 40 of the switch assembly. As light from the LED is direct and unobstructed light intensity is higher than when light has to pass a light guide and optical filtering and diffraction of different wavelengths of light, and hence colour distortion, is avoided. A user may more readily locate and identify the key, particularly when the key is located on a keyboard.

The light source or illumination means may serve to illuminate a plurality of keys, preferably a plurality of keys all in the form of switch assemblies of the present invention. A plurality of light sources, such a plurality of RGB LEDS may be used as the illumination means. The switch assembly or keyboard may advantageously provide control means for adjusting at least one of the intensity of illumination, the colour of illumination and the duration (such as for a power saving or 'sleep mode') of illumination are adjustable by a user. The control means may comprise means of a, such as a dial, located on the switch assembly or keyboard for ready accessibility by a user.

The switch membrane 80 and the support sheet 70 as shown in figures 11 and 12 act together to provide an optical mask to stop light emerging between the keys. The overhang of sides 20 of the caps enables any light that may escape between switch insert 14 and aperture 64 to be stopped from being viewed by a user, thus limiting escaping light, when the key switch is illuminated to the window area 40.

Figures 16 to 22, which show various views of a key cap assembly 210 for use in a switch and keyboard according to a second embodiment of the present invention, will now be referred to along with figure 25.

Key cap 212 comprises a rectangular optically clear, transparent, window 240 which is surrounded by an opaque frame 242. The frame 242 has a leg 250 at each corner, having four corners the cap therefore has four legs. The legs taper from a point of attachment to the frame to a latch member 260 for latching into corresponding apertures for each key in a support sheet 274. The latches 260 comprise flanges 262 on two outer sides of the leg to snap over a lower face of the rim of the apertures 264 to retain the key cap on the support sheet 274. A key cap assembly of the second embodiment comprises a rectangular leaf spring 228 of dimension such that the spring encircles the legs 260 and covers an area corresponding to the lower face of the frame 242. The leaf spring 260 is configured such that in expanded form the spring contacts at its upper face at four points 234' the four bosses 232 of the key cap and at the lower face 230" of its four corners 230 contact the support sheet 274. The leaf spring 260 in combination with the flanges 260 of the legs 250 thus retain a key cap assembly 210 in place on the support sheet 274 with lower faces of spring centre portions 234" biased away from the surface of the support sheet 274 and the covering transparent switch membrane 280 such as when part of an array of keys on a keyboard.. The switch membrane 280 comprises apertures corresponding with the apertures in the transparent support sheet 274. The switch membrane 280 is constructed so that at least one switch contact lies beneath at least one of a spring centre portion 234".

In use pressure on an upper face 240 of a key cap causes legs 250 to move through apertures 264 as the key cap moves towards the support sheet 274. By this action the leaf spring 228 resiliently deforms as bosses 232 and support sheet 274 act upon spring centre faces 234' and spring corner lower faces 230". As the spring 228 progressively compresses, eight upper spring faces 236 may be configured come in to contact with a lower face of the frame 242 and provide additional resilient resistance to further key cap movement.

Further depression of a key cap serves to further splay corners 230 of the leaf spring 228.

The leaf spring 228 (28) is made from a polymeric material, such as polypropylene. Alternatively a metal may be used, such as spring steel, and is desirable in the second embodiment (Fig 20) as a higher Young's modulus is obtained and the spring can be made thinner. By providing a spring that can be conveniently seated upon a key, between the latches 260 and the frame 242 and around the legs 250 a sub-assembly is conveniently created by pressing the spring over the latches 260 of a key cap.

The spring and key cap are symmetrical, having two axes of symmetry, the above sub assembly can therefore be provided by placing the spring 228 over the key cap 212 in any of four orientations (for a square key).

Similarly the key assembly bosses 232 and associated lower spring faces 234" are present on every side of the key cap 212 so that however a key is placed in the support sheet 274 the key will be capable of actuating the switch membrane, even if only one switching point is present on the membrane, thus keys may be placed in the support sheet 274 in any of 4 orientations, for later annotation with a character or other symbol or message, such as a letter symbol.

Further, routing of tracks on the switch membrane is problematic with keyboards as at least two contacts per key are required and space is limited, particularly when it is required to pass light through that membrane as conductive tracks are opaque. The use of four legs reduces the membrane 'real estate' used by the key caps and maximise the area for routing tracks. By providing a transparent support sheet 274 and switch membrane 280 generalised lighting below the support sheet 274 may be provided, such as by LEDs 290. The visibility of light at the keyboard surface is thus regulated by a combination of light transmission through the optically clear windows 240 and light absorption or back- reflection by a mask 276 between the keys and the key frames 242. This provides a keyboard that is evenly illuminated across a plurality of keys since several keys will use light from several light sources, thus evening out light distribution, which is seen only at the windows 240. The keyboard case 298 serves to prevent the escape of light elsewhere on the keyboard. Essentially the same considerations apply to the keyboard of the first embodiment of the invention.

Figures 23 and 24, which show a keyboard 284 according to a second embodiment of the present invention, will now be referred to. The key cap assemblies 210 of the second embodiment of the invention may be arranged in an array in a case so as to form a keyboard. The keyboard is as the previously described keyboard but being equipped with keys according to the second embodiment of the invention. The key cap assemblies cover the surface of the support sheet 274 with gaps between the key caps 212. Light is prevented from escaping from these gaps by means of a mask 276 placed over the support sheet 274 or over the switch membrane 280. The mask may be a sheet of material or may be printed upon the support sheet 274 and or the switch membrane 280. The switch membrane 280 may comprise tracks that also act as the mask, or part of the, mask, this may reduce or remove the need for a separate mask. Such tracks may include tracks present only for acting as part of the mask or only as tracks for conducting electrical signals. Keyboards 84/284 of the present invention also comprise control electronics, such as dedicated keyboard controller chip, such as one in the form of a microcontroller. The control electronics preferably comprise circuitry to provide modulation of light from the LEDs 290 and to change the colour output of the LEDs 290. The keyboard may also comprise manual controls 310, 312 to provide on/off, brightness and red, green, blue light controls in order to obtain each colour or a mix of colours when the keyboard illuminates itself. The controls may be provided in the form of wheels, such as wheels connected to potentiometers. The RGB colour mix may preferably be controlled by a joystick type control pad 310 which provides more intuitive control of RGB colour mixing to cover the position of the light output in what is known as colour space. Alternatively the joystick type control pad 310 may control light intensity only. Activation of the control pad may serve to activate a program that provides a depiction of a form of colour space on a computer monitor screen so that the controls 310, 312, 312' etc, can be manipulated with visual feedback of where in colour space the selected keyboard mix is. This is particularly important when using separate red, green, blue and overall brightness controls as an uniformed user, such as a child, may not be otherwise able to navigate to their desired colour. This is particularly advantageous for mixed colours such as orange. The keyboards of the invention may comprise a hand rest portion 314. Provision of apertures in a front side of the keyboard 84/284 may be used in conjunction with a transparent or translucent hand rest component 314 so as to permit illumination of the hand rest 314. The present invention thus permits the illumination of other features of a keyboard other than only keys by the provision of a generalised light source 290 inside a case 298.

The case 98/298 of a keyboard of the present invention preferably comprises a reflective surface finish on the inside of the case. The light efficiency is thus improved; this is not possible with keyboards not having general illumination as light reflected from one key would reflect back to other keys. Similarly the wiring board 292, supporting the LED's may have a metallised surface, such as from tinned printed wiring board tracks so as to improve light efficiency by internal reflection.

The switch may be used with an illumination means so as to provide a selectively illuminated key. Switches of the invention are advantageously useable in groups, such as to provide a keyboard. Various advantages and descriptions of features are disclosed above for the various embodiments of the present invention. It should be understood that those features are also applicable, any necessary changes being made, to the other embodiments.

In the present invention it is to be understood those terms like illuminate and illuminated are intended to refer to devices of the invention as such and not to background illumination from the environment. The term illuminatable herein means capable of self illumination, i.e. auto -illumination or if referring to a switch then capable of passing light from an, in use, lower or enclosed side to an upper, key press side.

Claims

1. An illuminated keyboard (84, 284) comprising an internal light source (90, 290), a plurality of keys (10, 210) having optically clear upper faces (40, 240), a casing having a support sheet (70, 274) on one face and a switch membrane (80, 280) for detecting key presses of each of the plurality of keys, the switch membrane being located over the support sheet and below tops of the keys, the keys each having retaining (58, 260) and guiding (50, 250) portions located in apertures (64, 264) through the sheet and membrane, the tops of the keys being resiliently biased away from the sheet and membrane by at least one leaf spring (28, 228) located outside the guiding portions and acting upon the tops of the keys and the switch membrane, the keys having a hollow structure so as not to obstruct light passing directly from the light source to the clear upper faces of the keys.

2. The keyboard of claim 1 wherein the keyboard further comprises an optical mask to prevent light escaping between the keys.

3. The keyboard of claim 2 wherein the switch membrane and/or the support sheet performs the function of the mask.

4. The keyboard of any one of claims 1 to 3, wherein the optically clear upper faces of the keys comprise a central window and an opaque surrounding frame.

5. The keyboard of claim 4, wherein the at least one leaf spring and the retaining and guiding portions are located entirely under the frame so as not to obstruct light from the light source.

6. The keyboard of any of claims 1 to 5 wherein the optically clear upper faces of the keys are the face of a lens.

7. The keyboard of any of claims 1 to 6 wherein, the internal light source is one or more light emitting diodes, the diodes being remote from the keys and each diode serving to illuminate one or more than one key.

8. The keyboard of claim 7, wherein the one or more light emitting diodes are single diodes of different colour output or combined red/green/blue (RGB) diodes capable of selectively emitting a spectrum of visible light.

9. The keyboard of claim 8, wherein the manner in which the single diodes of different colour output or RGB diodes selectively emitting a spectrum of visible light are adjustable by a user by means of controls mounted on the keyboard.

10. The keyboard of claim 8, wherein the manner in which the single diodes of different colour output or RGB diodes selectively emitting a spectrum of visible light are adjustable by a user under software control from a computer to which the keyboard can be attached.

13. Then illuminated keyboard of any of claims 1 to 10, comprising a press-to-make electrical switch assembly wherein the key guiding portions are in the form of legs, the legs depending from the key about the optically clear upper face in the form of a window and terminating in a retaining member in the form of a latch, the legs each penetrating the support sheet on one face and a switch membrane by means of corresponding apertures therein.

12. The illuminated keyboard of claims 1 to 10, comprising a press-to-make electrical switch assembly wherein the key guiding portions are the sides of a tube depending from the key and circumscribing the optically clear upper face in the form of a window and terminating in a retaining member in the foπn of a plurality of latches, the tube penetrating the support sheet on one face and a switch membrane by means of a corresponding aperture therein.

13. The switch assembly according to claim 11 or claim 12 further comprising an illumination means for illuminating the upper face of the switch from below the support sheet.

14. The switch assembly of claim 13 wherein the illumination means is a single colour LED, a cluster of differently coloured single coloured LEDs or an RGB LED.

15. A keyboard illumination system comprising i) a keyboard according to any of claims 1 to 12; ii) a computer system linked to the keyboard for the inputting of information typed on the keyboard by a user; iii) a computer programme for monitoring the resulting key presses on the keyboard and at least one of the colour, intensity and duration of illumination of keys on the keyboard iv) a further computer programme for correlating at least one of the frequency of key presses and the frequency of key press errors with the data monitored at iii) v) means for adjusting the illumination of the keyboard according to predefined rules and adjustment of the illumination according to those rules, the rules using data from both of steps iii) and iv) to provide illumination adjustment with an expectation of influencing typing speed or accuracy; vi) optionally iterative operation of steps iii), iv) and v) to optimise keyboard illumination for the user as determined by one of both of the parameters frequency of key presses and the frequency of key press errors selected at iv) vii) optionally provision of a visual map of CIE colour space whereon successive adjustments of illumination from step vi) are displayed to chart the progress towards optimising keyboard illumination. viii) optionally in conjunction with any previous step, providing a illumination of information on a visual display unit as part if the computer system usable by the user for monitoring their typed information, wherein the illumination corresponds to and is adjusted in conjunction with the keyboard illumination ix) optionally, wherein the illumination adjustment is an adjustment of one or more of colour of illumination, illumination intensity and illumination duration, preferably only of colour.

16. The use of a keyboard according to any of claims 1 to 12 to optimise the illumination of the keys of the keyboard by means of the system of claim 15.

17. A keyboard as herein described with reference to any one of figures 1 to 15 and the accompanying description.

18. A keyboard as herein described with reference to any one of figures 16 to 26 and the accompanying description.