Illuminating Device With A Rechargeable Battery Or A Mains Supply Power Source

Abstract

This disclosure relates to an illuminating device, primarily for use as a book reader, in which a slightly tapering transparent sheet is illuminated edgewise by low-intensity lamps in a housing extending along its thicker edge. The sheet is placed flat against the book page to be read, the page being illuminated by light internally reflected from the front surface of the transparent sheet and being read through the transparent sheet. Circuits are described for alternatively energizing the lamps from the mains supply and a rechargeable battery.

Description

The present invention relates to an illuminating device for enabling books and other documents to be read or viewed in a dark room without producing substantial illumination in the room. The device is particularly suitable for enabling a person to read in bed at night, for example at home or in hospitals, with the minimum of interference with other persons sleeping or resting in the same room.

The illuminating device according to the invention consists of a generally rectangular sheet of transparent material of a convenient size to cover the whole or a part of the page of a book or other document to be read, said sheet tapering slightly in thickness from one edge to the opposite edge, and a housing containing one or more low voltage low-intensity lamps disposed along the thicker edge of the sheet and arranged to illuminate said edge of the sheet, the arrangement being such that the light projected into the sheet is internally reflected from a surface thereof (hereinafter referred to as the upper surface) so that at least a part of the light passes out of the sheet through the other surface thereof (hereinafter referred to as the lower surface) said lower surface being free from obstruction so that it can be placed flat against the page of the book or surface of the document to be read.

By means of this device the page can be substantially uniformly illuminated so that it can be read by looking through the transparent sheet, while scattered light in the room remains low. In fact the main proportion of light which is scattered in the room arises from reflection from the page being read, so that by keeping the intensity of the light low and sufficient only to enable easy reading without eye-strain the amount of scattered light can be kept to the minimum. The edges of the sheet other than where the light passes thereinto may be rendered opaque by painting or in any other convenient manner in order to avoid light from leaving the device other than through the upper and lower surfaces of the sheet.

The lamp or lamps in the housing of the device may be energized from the mains supply through a stepdown transformer, or they may be energized from a battery contained in the housing or in a separate casing.

According to the feature of the invention the device is adapted to be energized from the mains through a stepdown transformer and also incorporates a battery which serves the purpose of an alternative source of electric supply when a mains supply is not available and/or for effecting remote switching on and off of the mains supply. Preferably the battery is of the rechargeable type and is connected so as to be chargeable from the mains supply when the lamps are being illuminated from the mains supply and/or when the device is not in use but is still connected to the mains supply.

A further feature of the invention consists in providing the device with a mirror surface to enable it also to be used as a mirror.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of a book page illuminating device according to the invention.

FIG. 2 is a section through the housing of the device along the line A--A of FIG. 1.

FIG. 3 is a scrap view of the housing.

FIGS. 4 and 5 are two circuit diagrams.

FIG. 6 is a sectioned perspective view of a picture illuminating device according to the invention.

Referring to FIGS. 1-3, the device comprises a sheet 1 of a transparent material, conveniently a transparent plastics material such as known under the Registered Trademark "Perspex." Along one edge of the sheet is secured an opaque housing 2 which contains one or more small electric lamps 9, such as lamps as used in hand torches, for illuminating the sheet edgewise. The upper surface 1a of the sheet slopes towards the lower surface 1b in the direction away from the illuminated edge, and the arrangement is such that some of the light entering the sheet will be reflected internally from the upper surface and out through the lower surface to illuminate the page to be read, against which the lower surface of the sheet is laid flat when the device is in use. The other edges, 3, 4 and 3' of the sheet are rendered opaque, for example by painting. A convenient size for the sheet is 81/2".times.5", and it may be about 1/4" thick adjacent the housing 2 and taper to about 1/16" at its other end.

The lamps are energized from the electric mains supply through a stepdown transformer contained in a casing 6 provided with contacts 5 for plugging it into a conventional mains lighting socket, and is connected to the lamps 9 by a flexible cable 7, preferably provided with plug-in connections 10,11. The housing 2 may carry an appropriate control switch or switches 12.

In order to reduce the temperature to which the housing 2 is heated by the heat generated by the lamp or lamps 9, the housing may be provided with ventilating apertures 8, preferably disposed in the wall of the housing at positions above and below the lamp or lamps when the sheet is substantially horizontal, baffles being provided to prevent light from the lamps passing out of the housing through the ventilation apertures. As shown in the drawing, the baffles are constructed as reflectors 13 to guide light from the lamps 9 towards the edge of the transparent sheet 1. Alternatively separate reflectors for this purpose may be provided in the housing. The housing 2 is also shown as accommodating a battery 17 in a compartment 18 accessible by removing the end cap 2a of the housing. The compartment 18, reflectors 13 and holders for the lamps 9 may be assembled on a spine or frame 19 and removable as a unit from the housing 2 for servicing or lamp replacement. The spine or frame may be conveniently carried on the other end cap 2b of the housing and removable therewith. The switch or switches 12, or at least the contacts thereof, is/are preferably removable with the spine or frame and may conveniently be mounted on the end cap 2b.

The battery 17 is preferably of the rechargeable type and connected in a circuit so that it is rechargeable from the output of the mains transformer. The battery can be used as an alternative source of supply for the lamps, when a mains supply is not available. It is desirable, if the device is to be used for reading while in bed, and especially so if the user is a patient in a hospital, that the lamps may be switched off without the user having to get out of bed to switch off the mains switch in order to render the device "safe."

One suitable form of circuit is shown in FIG. 4 in which the battery 17 is connected in series with a diode 20 and resistor 21 across the terminals 10a, 10b into which the plug 10 at one end of the cable 7 is inserted, the plug 11 at the other end of the cable being inserted into the terminals 11a, 11b on the casing 6 containing the stepdown transformer 22. The lamp 9 is connectable across the battery 17 when the switch 12 is closed.

With the circuit described, the output from the transformer 22 is rectified by the diode 20 and charges the battery. When the switch 12 is closed the lamp 9 is illuminated from the battery, irrespective of whether or not it is being simultaneously charged from the mains. With the circuit described there is always the battery charging load across the output of the transformer so that the transformer will not overheat or burn out if the lamp is switched off and the mains switch is left on.

FIG. 5 shows another circuit in which the battery is used for the remote control of switching on and off of the mains supply to the transformer. To this end the casing 6 also contains a relay 23 having normally open contacts 23a in the circuit to the primary winding of the transformer 22 and the cable 7 contains a third wire connecting a terminal 11c on the casing 6 to a terminal 10c on the housing 2. The relay 23 is bridged across the terminals 11a, 11c and is also connected in series with the secondary winding of the transformer across the terminals 11a, 11b. Terminal 10c is connected through a normally open contact 12a to the junction between the diode 20 and the battery 17. Between the terminal 10a and the other pole of the battery 17 is a normally closed contact 12b. The switch 12 has a third position in which it connects the lamp 9 to the terminal 10b.

With the circuit of FIG. 5, by momentarily closing contact 12a the battery 17 is connected across the relay 23 which energizes and closes its contact 23a. The transformer is thus connected to the mains supply and the resulting current in the secondary circuit through the charging diode 20 and the battery 17 holds the relay 23 energized when contact 12a is opened. When the switch 12 is in its lowermost position the lamp 9 is energized direct from the mains and the battery is simultaneously charged. In the central position of switch 12, only battery charging takes place and the lamp 9 is extinguished. In the upper position of the switch 12 the lamp 9 is energized from the battery 17 which is simultaneously being charged. By opening contact 12b the circuit through the relay 23 is opened and consequently its contacts 23a open and the mains supply to the transformer is cut off. The contacts 12a, 12b, which are conveniently pushbutton operated, thus effect remote control of the mains supply to the transformer. When the mains supply is cut off, and also when the device is not connected to the transformer, the lamps 9 can still be illuminated by the battery by turning the switch 12 to its upper position.

If a nonchargeable battery is used, the circuit may be similar to that shown in FIG. 5 but the diode 20 and resistor 21 would then be omitted.

In order that the lower surface of the sheet 1 may be placed flat against the page to be read, it must be kept free from obstruction. Even if the sheet is lifted only a short distance away from the surface of the page the intensity of illumination of the page is seriously reduced in view of the low intensity of the light from the lamps. If desired the device may be provided with a clip for clipping the device on to a page of the book. This clip may itself comprise a backplate 14 of thin rigid material of substantially the same size as the sheet 1 so that the page to be read is held flat between the sheet 1 and the backplate 14. The backplate may be pivoted to the housing 2 by pivots 15, and the sheet and backplate may be urged together by a spring 16.

The backplate 14 may have a mirror surface, or carry a mirror, on either or both its front and rear surfaces, so that the device can be used as a mirror as well as a book reader. The backplate 14 may be of sheet metal with a highly polished or plated surface.

If desired the upper surface of the sheet may be silvered or treated to form a semitransparent mirror surface. This assists in increasing the illumination of the page and also enables the device to be used as a mirror.

The surfaces of the sheet 1 may be processed or coated to possess antistatic and/or antiscratch properties.

It will be appreciated that the device, instead of being used as a book reader, can be used for illuminating other documents or surfaces to be viewed instead of read, such as pictures, paintings or photographs. It is only necessary to mount the picture behind the sheet 1. The housing containing the lamps may, as shown in FIG. 6, be constructed as part of a picture frame 24 of which the sheet forms the front "glass" behind which the picture or photograph is mounted. The frame may be provided with means for hanging it on a wall or supports for standing it on a surface. The frame may incorporate a rechargeable battery as above described, so that the frame can be stood or hung in any desired position, and illuminated, without it being necessary to have an electric cable leading thereto while it is illuminated.

While particular embodiments have been described, it will be understood that various modifications may be made without departing from the scope of the invention. For example, instead of being made of a transparent plastics material, the sheet 1 may be made of glass. Moreover, the rectifier and resistor of the charging circuit may be incorporated in the casing 6 instead of in the housing 2.

Claims

I claim:

1. An illuminating device comprising a generally rectangular sheet of transparent material of which both opposite surfaces are flat smooth and polished, said sheet tapering slightly in thickness from one edge to a thinner opposite edge, and a housing containing at least one low-voltage low-intensity lamp disposed along the thicker edge of the sheet and arranged to illuminate said edge of the sheet, the arrangement being such that the light projected into the sheet is internally reflected from one surface thereof so that a part of the light passes out of the sheet through the other surface thereof, said other surface being free from obstruction so that it can be placed flat against a surface to be illuminated with only low light intensity sufficient to enable it to be viewed by looking through the transparent sheet.

2. A device as claimed in claim 1, wherein the housing is provided with apertures to allow air to circulate therethrough to cool said at least one lamp and the housing, light baffles preventing any substantial amount of light from being emitted through said apertures.

3. A device as claimed in claim 1 in combination with a stepdown mains transformer having primary and secondary windings, a flexible cable connecting said secondary winding to the device to provide current for energizing said at least one lamp, a battery as an alternative source of current for said at least one lamp, and a relay which is assembled as a unit with the transformer and is connected in circuit with said secondary winding and, when energized, closes normally open contacts in the circuit to the primary winding of the transformer, and a remote control switch which, when closed, completes a circuit from the battery and through the flexible cable to energize the relay, the relay remaining energized, when said switch is reopened, so long as the secondary current flows therethrough.

4. A device as claimed in claim 3, wherein said battery is rechargeable and a rectifier is provided connectable in a circuit in series with the battery and said secondary winding for charging the battery, and the housing carries a switch for connecting said at least one lamp across the poles of the battery.

5. A device as claimed in claim 1, in combination with a stepdown mains transformer having a primary and a secondary winding, a flexible cable connecting said secondary winding to the device to provide current for energizing said at least one lamp, a rechargeable battery in series with a charging rectifier connected across said secondary winding in parallel with said at least one lamp, and a relay which is assembled as a unit with the transformer and when energized, closes normally open contacts in the circuit to the primary winding of the transformer, a remote control switch which, when closed, completes a circuit from the battery and through the flexible cable to energize the relay, said relay being connected with said secondary winding so as to remain energized, when said switch is reopened, so long as the secondary current flows.

6. An illuminating device as claimed in claim 4, and including means for assisting dissipation of the heat generated by said at least one lamp; a frame carrying said at least one lamp, a compartment for said battery and said switch and the associated electrical connections and forming a subassembly insertable as a unit in said housing; means rendering opaque the edges of said transparent sheet other than said thicker edge.

7. A device as claimed in claim 6, wherein the housing is provided with apertures to allow cooling air to circulate therethrough, and at least one light baffle for preventing substantial escape of light through said apertures, said at least one baffle constituting a reflector for directing light from said at least one lamp towards the edge of the transparent sheet and being carried by said frame, and wherein said one surface of the transparent sheet is formed as a semitransparent mirror.

8. A device as claimed in claim 1, wherein said at least one lamp, a compartment for housing a battery, a control switch and the associated electrical circuitry and connections are carried on a frame insertable as a unit into said housing.

9. A device as claimed in claim 1, wherein a backplate is provided adjacent said other surface of the transparent sheet for holding a sheet to be illuminated close against said other surface, said backplate being pivoted to the housing and being urged by a spring towards said other surface of the sheet, and at least one of the surfaces of said backplate comprising a mirror.

10. A device as claimed in claim 1, wherein the housing forms part of a picture frame of which the transparent sheet forms the front "glass," and means mounting a picture or the like against the rear surface of the transparent sheet.