GB2284711A - Electric switch - Google Patents

Abstract

An electric switch includes an illuminatable surround (21) of the type described in GB 2251980 disposed around an operating toggle (13) for indicating the location of the switch. In order to ensure that all the required safety standards are met when the surround is designed as an ab initio component of a switch/surround combination, the internal electrical connections are in the form of a printed circuit board (41) on which the switch contacts are mounted, and the illuminated surround (21) is spaced from that hoard by a physical insulating barrier (31) so as to prevent any significant possibility of the surround being electrically or thermally influenced by the currents and voltages in the board. <IMAGE>

Description

Electric switch fittings This invention relates to electric switch fittings, and concerns in particular such fittings incorporating an illuminated surround.

Electrical switches of the sort found wall-mounted in homes, offices, factories and other buildings, and used for the supply and control of electric appliances such as room lights, heaters, televisions and the like, are often used - turned on - when the ambient light conditions are poor. Indeed, light switches in particular are commonly employed when it is actually so dark that the switch itself can barely be seen. It has therefore been suggested a number of times in the past that each switch should be fitted with some sort of small and inexpensive light source by which the location of the switch can immediately and easily be seen even in what would otherwise be complete darkness. One such suggestion is that the subject of our co-pending British Patent Application No: 91/26,717.9 (Publication No: 2,251,980A), in which there is described and claimed a behind-the-switch mounting plate that is constructed partly as an annular light guide (of the totallyinternally-reflected type), to which light is supplied from a light source, and partly as an annular light diffusion member, to which light is uniformly delivered from the light guide and from which that light can escape into the surrounding space, the annular light diffusion member extending more or less evenly around the switch plate so that in effect the light from the light source is seen as a halo-like glow surrounding the switch.

As is explained in the Specification of our aforementioned Application, this earlier illuminated mounting/backing plate, or surround, may be designed either as an ab initio component of a switch/surround combination (of which it may be either an integral part or a separate part attached thereto during production) or as a separate item for subsequent fitting to an already-installed switch, and it works well in either form. However, when intended for use ab initio as a part of the fitting the result may not meet all the required safety standards, especially in cases where the light guide is adjacent, and not physically separated from, the electrical components of the unit. The present invention seeks to deal with this problem, to provide a switch unit meeting the appropriate standards, by proposing first a unit wherein the internal electrical connections are in the form of a printed circuit board (pcb) to which the other components are both physically and electrically mounted and attached, and then by spacing the illuminated surround from that pcb by a physical insulating barrier so as to prevent any significant possibility of the surround being electrically or thermally influenced by the currents and voltages in the pcb.

In one aspect, therefore, the invention provides an electric switch incorporating an illuminatable surround, wherein the switch and surround combination comprises: a switch unit having a switch toggle mounted adjacent a wiring loom incorporating switch contacts operated by the toggle and operatively connectable between a supply of electricity and an electrical device to be switched, wherein the loom takes the form of a printed circuit board (pcb) defining the necessary conductive elements and carrying mounted thereon the switch contacts; an illuminatable surround, of the backing plate type described and claimed in our aforementioned Application, operatively disposed around the toggle; and spacer means situated around the surround and between it and the adjacent pcb wiring loom so as physically and electrically to separate one from the other.

Disposed around the toggle of the switch of the invention is an illuminated surround according to our aforementioned Application. The details of this surround/backing plate may be obtained from the Specification of that Application, but for convenience they are now briefly repeated here.

Basically, the surround comprises: a generally annular light guide around which light delivered thereinto is transmitted as a result of total internal reflection; mounting means for a light source operable to deliver light into the light guide to be transmitted therearound as aforesaid; and a generally annular light diffuser disposed alongside and operatively connected to the light guide in use to receive therefrom some of the light being thusly transmitted therearound, and diffusely radiate it away therefrom; the size and shape of the light diffuser being such that in use it lies around the switch, projecting generally evenly laterally therefrom, so enabling the diffuse light radiated therefrom to be seen as a halo around the switch.

The light guide, or light pipe, is "generally annular" (ring-like), and preferably it is a whole ring, but of a rounded square/oblong shape (an especially preferred shape is that of a rhombus, or diamond, which enables a better dispersal of light to the diffuser).

The light guide should be so shaped, curved and dimensioned as to cause light injected into it to pass round and round, being reflected (by total internal reflection) off the inside surface without any - or any significant amount - leaking out into the surrounding space (except, of course, where that is actually required). A typical overall form for such a light guide is a solid pipe or rod of transparent material, conveniently one of about 0.5 cm (0.3 in) circular cross-section (although one preferred embodiment has a square section in which the surface on the outside of the annular pipe is slightly curved the better to reflect light toward the diffuser adjacent the inside surface). The guide material, which may be water white or coloured, is advantageously made of that acrylic plastics available from ICI Acrylics under the name DIAKON.

To improve or modify its diffuse light output, the light guide can contain distributed therethrough a fluorescent substance, or be made of a material that is naturally fluorescent, and then be used with a light source that outputs at least part of its energy at the wavelengths that cause that substance to fluoresce.

The light source mounting means is desirably a small recess formed within the guide, the source - a correspondingly small neon bulb, for instance conveniently being inserted thereinto. Advantageously there is more than one source, and thus more than one mounting means - in a preferred embodiment there are two, located one at either end of a diameter (or diagonal) across the annular light pipe.

The or each source is most conveniently a small electrically-powered neon bulb powered from the switch's own power source. It may be operatively associated with an appropriate photodetector device, to make it lightsensitive so that it only glows when the ambient light conditions are such that it is dark.

The annular light diffuser, or escape channel, matches in shape and size both the light guide from which it receives light and the switch beyond which the diffuser is required to project in use.

The surround combination of annular light guide and annular light diffuser disposed therealong can be one wherein the ring of the diffuser lies outside the ring of the guide, especially where the diffuser is to extend laterally beyond the switch front plate. However, with small switches, or when the diffuser is to surround not the front plate but the switch unit directly (and in particular the switch's toggle), it may be more convenient, in the space available, to position the diffuser to lie inside the ring of the guide. An example of this latter arrangement is discussed hereinafter with reference to the accompanying Drawings.

The light diffuser section is conveniently of generally rectilinear section, with flat front and rear (as used) faces.

The diffuser is most desirably integral with the light guide. Indeed, in the most preferred form the guide is a solid ring having a laterally projecting integral flange which is, or is continuously integral with, the diffuser.

The diffuser preferably has a window portion, from which the light actually radiates, and a diffusing element that directs light to the window in such a way that most actually passes through rather than being reflected and "re-captured". One especially convenient way to attain this is to provide a prismaticallyreflective surface area on the rear (as used) side of the diffuser, with a window on the opposite, front (as used) side, the rear surface being so angled (at about 45 ), and the prismatic area being so positioned, that light entering the diffuser from the guide falls on this prismatic area and is specularly scattered forwards to and through the window. Such an arrangement is shown in the accompanying Drawings.

The shape and size of the diffuser is such that in use it more or less evenly surrounds, and projects - by a centimetre or even less - laterally beyond, the switch (or the switch toggle), so that light radiating from the diffuser can spread outwards into the surroundings ad can be seen from all sides without hindrance by the switch, and in the preferred forms the front surface area of the surrounding/projecting part is the window referred to above.

It is also advantageous so to shape the diffuser that the switch itself "fits" therewith. It may be especially preferred to make the front projecting surface of the diffuser - the window - actually flush with the front surface of the switch.

The diffuser may be made of any suitable material, and can contain within itself a fluorescent substance, and/or be coloured. Of course, where the guide and diffuser are one integral whole then most conveniently they are made from the same material.

Where the surround is one integral whole, then most conveniently it can be made by moulding or stamping/ pressing.

As will be apparent from the foregoing, the diffuser of the surround may be of any suitable shape and size - provided, of course7 that in use it surrounds/projects out from the switch, and more particularly from the switch front plate (the plate behind which the working parts of the switch are supported). For one preferred type of switch this front plate is a small hollow rectangle, typically around 0.75 x 1.75 in (2 x 4 cm), barely surrounding the switch unit (the toggle and contacts) itself. In such a case it is preferred to employ one wherein the diffuser ring lies inside the guide ring.

The switch unit of the invention incorporates a switch toggle (the mechanics of the switch may take any appropriate form) mounted adjacent a wiring loom (which carries the actual switch contacts operated by the toggle, which contacts are operatively connectable between a supply of electricity and the electrical device to be switched); the loom takes the form of a printed circuit board (pcb) defining the necessary conductive elements (the circuitry for the internal light source feeding the light guide). The use of a pcb - which may itself take any appropriate form - allows the various conductive members to be kept neatly and tidily in place, stably spaced away from the surround itself.

The conductive elements within the switch may get hot, and operation of the switch contacts may cause arcing. The surround needs to be protected from the resultant thermal and electrical conditions, and accordingly in the switch of the invention there is spacer means situated around the surround and between it and the adjacent pcb wiring loom (and switch contacts) so as physically and electrically (and thermally) to separate one from the other. In principle this spacer means is little more than an insulating layer, conveniently of a significant thickness, between the surround and the pcb, and preferably actually disposed on and over the pcb-facing surfaces of the surround, rather like a sleeve. However, in practice it is very preferably much more than that, in that it also surrounds, sleeve-like, the switch toggle, and is sufficiently thick and rigid, and strong, to provide not only the required spacing but also the pivot points/supports for the toggle. A typical material for this spacer means is a rigid plastics substance such as a (phenol)urea polymer.

The switch unit's faceplate and backplate may be made of any of the strong insulating materials typically a plastic such as a (phenol)urea polymer used or suggested for use in the Art for electric switch bodies, and no more need be said about that here.

An embodiment of the invention is now described, though by way of illustration only, with reference to the accompanying diagrammatic Drawings in which: Figures 1A to C show respectively side and front elevation, and "sectional", views of a switch/surround combination of the invention; Figures 2A to D show various front, rear, and sectional views of an illuminatable surround shown in use in Figure 1; Figures 3A to F show an "exploded" isometric view of the main components of the Figure 1 unit; Figures 4A to F show sectional views matching the Figure 3 perspective views; and Figures SA & B are circuit diagrams showing the use of switches of the invention.

Referring to Figure 1, the switch (generally 11) has a faceplate (12) in the centre of which is mounted the switch toggle (13) immediately surrounded and supported by a thin wall (14) which carries (not shown here: see Figures 3C and 4C) on its internal surface the toggle pivot (35). This wall 14 is part of the spacer means (31), and surrounding it is the visible front edge/window (15) of the surround's light diffuser (23 in Figure 2: the "cross hatching" represents the prismatic rear surface of the diffuser's diffuser element). At the back of the switch is a backplate (16) shutting of the switch innards from prying fingers: these innards the light guide and the main body of the surround (21), the main body of the spacer 31, and the printed circuit board (pcb 41) - can be seen in Figure 1C (in part) and perhaps more clearly in Figures 2 to 4.

Figure 2 shows the surround - the combination of light guide and light diffuser. The surround (generally 21) has a roughly rhomboidal annular light guide (22), of squarish section, that is integral with a correspondingly rhomboidal light diffuser (23) disposed co-axially with and inwardly thereof. The light guide 22 has two apertures (as 24) into which in use project the light sources (see Figure 3), and the rear surface (25) of the diffuser 23 is both angled, to reflect forwardly light escaping from the guide into the diffuser, and prismatically shaped, to "scatter" that forwardly-reflected light as it exits the diffuser via the window surface (15).

In use, the surround fits into a recess in the rear surface of the faceplate 11, the back of the diffuser 23 sitting slightly recessed of the rear surface (see Figure 1C).

The major components of the switch unit of Figure 1 are shown in Figures 3 and 4 (the Figure 4 sections are taken on a line/vertical plane IV-IV as indicated in Figure 3). The faceplate 11, surround 21 and backplate 16 have already been discussed. The remaining components are the spacer (generally 31), the switch toggle 13, and the pcb (generally 41).

The spacer 31 comprises a flat plate (32) with a central aperture (33: to contain the switch toggle 13) surrounded by a wall 14. The plate 31 has two apertures (as 34) through which the light source bulbs (43) carried by the pcb 41 project into the light guide, and is shaped and sized to match the faceplate recess holding the surround 21: fitting in on top of the surround it "seals" the surround from the pcb 41.

Similarly, the wall 14 is shaped and sized to fit around the toggle 13 and inside the diffuser 23: thus, it "seals" the surround from the switch contacts (see Figure 1C).

On the inside surface of the wall 14 are two opposed inverted "V" recesses (35: only one is shown) which provide the actual pivots for the switch toggle 13. As can be seen in Figure 3D, the toggle carries on its matching outer surfaces two "corresponding" - slightly smaller - inverted "V" projections (36: only one is shown) that fit loosely into the recesses 35 and allow the toggle to rock back and forth therein. The mechanism of the toggle switch and its contacts (generally 44) is best seen from Figure 1C. It is quite conventional, and needs no further comment here.

Beneath the toggle 13 and the surround 21, and spaced therefrom by the spacer 31, is the pcb 41. It carries the conductive elements (as 42) necessary for the functioning of the switch and light source, the light source itself - in this case the two bulbs 43 and, on its surface distant from the toggle, the actual switch contacts (44: see Figure 1C). The pcb also carries the other necessary components, such as resistors (45 in Figure 4E), as well - in this case - as a small double pole switch (44) wired into the circuit to enable the main switch unit to be converted between single and double pole operation at will (see also the circuit diagram of Figure 5).

Finally, the backplate 16 bears channels (as 46) and fixing means (47: see Figure 1C) for the insertion thereinto of the appropriate wires connecting the switch into the power/device circuit), as well as various recesses (not referenced) to accommodate the several projecting items on the pcb.

Switch units according to the invention may be used in circuits of the type shown in Figure 5. Figure 5A shows a single switch unit (the apparatus within the dashed box SU, including the actual switch contacts C=Common, L1=Line 1, L2=Line 2 - and the switchilluminating neons N) controlling a mains-powered light (ML), while Figure 5B shows the use of two such switches (SU1,SU2) so that the light can be turned on or off by either switch. The circuits undoubtedly speak for themselves - including the operation of the small slider switches 44 each movable between positions 1W and 2W to convert its main switch from single to double pole operation - and need no further comment here, save perhaps simply to observe that in each case, the neons N in each switch unit SU light when the main light ML is off (in Figure 5A the main light is on, and the neons are "off" because there is insufficient voltage drop across them, while in Figure 5B the main light is off (the several resistors limit the available current), and both sets of neons are on).

Claims (12)

Claims

1. An electric switch incorporating an illuminatable surround, wherein the switch and surround combination comprises: a switch unit having a switch toggle mounted adjacent a wiring loom incorporating switch contacts operated by the toggle and operatively connectable between a supply of electricity and an electrical device to be switched, wherein the loom takes the form of a printed circuit board (pcb) defining the necessary conductive elements and carrying mounted thereon the switch contacts; an illuminatable surround operatively disposed around the toggle, the surround comprising a generally annular light guide around which light delivered thereinto is transmitted as a result of total internal reflection, mounting means for a light source operable to deliver light into the light guide to be transmitted therearound as aforesaid, and a generally annular light diffuser disposed alongside the-inside of the light guide annulus and operatively connected to the light guide in use to receive therefrom some of the light being thusly transmitted therearound, and diffusely radiate it away therefrom, the size and shape of the light diffuser being such that in use it can lie around the toggle, so enabling the diffuse light radiated therefrom to be seen as a halo around the toggle; and spacer means situated around the surround and between it and the adjacent pcb wiring loom so as physically and electrically to separate one from the other.

2. A switch as claimed in Claim 1, wherein the light guide is a whole ring, of a rounded square/oblong, or diamond, shape.

3 A switch as claimed in either of the preceding Claims, wherein the light guide annulus is a solid pipe or rod of transparent material having a generally square section, the surface on the outside of the annulus being very smooth and curved the better to reflect light toward the diffuser adjacent the inside surface.

4. A switch as claimed in any of the preceding Claims, which is to be used with two light sources, located one at either end of a diameter (or diagonal) across the annular light guide.

5. A switch as claimed in any of the preceding Claims, which is to be used with a light source powered from the switch's own power source and wired in such a way that it goes out when the switch is on.

6. A switch as claimed in any of the preceding Claims, wherein the annular light diffuser is a whole ring, of a shape matching the shape of the light guide, and has a generally rectilinear section, with flat front and rear faces.

7. A switch as claimed in any of the preceding Claims, wherein the light diffuser is integral with the light guide, the guide taking the form of a solid ring having a laterally projecting integral flange which is, or is integral with, the diffuser, and the connection between the light guide and the light diffuser is continuous all around the guide.

8. A switch as claimed in any of the preceding Claims, wherein the light diffuser has a window portion, from which the light actually radiates in use, and a diffusing element that directs light to the window in such a way that most actually passes through rather than being reflected and "re-captured", the diffusing element being either a prismatically-reflective or an amorphous roughened surface area on the rear (as used) side of the light diffuser, with the window on the opposite, front (as used) side, the rear surface being so angled (at about 45 ), and the prismatic or roughened area being so positioned, that light entering the diffuser from the guide falls on this prismatic/roughened area and is specularly or diffusely scattered forwards to and through the window.

9. A switch as claimed in any of the preceding Claims, wherein the shape and size of the light diffuser is such that in use it evenly surrounds, and projects laterally beyond, the switch toggle, so that light radiating from the diffuser can spread outwards into the surroundings and can be seen from all sides without hindrance by the switch.

10. A switch as claimed in any of the preceding Claims, wherein the spacer means is an insulating layer disposed on and over the pcb-facing surfaces of the surround.

11. A switch as claimed in Claim 10, wherein the spacer means also surrounds the switch toggle, and provides not only the required spacing but also the pivot points/supports for the toggle.

12. An electric switch as claimed in any of the preceding Claims and substantially as described hereinbefore.