GB2201502A - Sun canopy - Google Patents

Abstract

A portable sun canopy is described which uses a light-weight electronic ballast (12) and which provides substantially uniform UV radiation because the fluorescent tube temperature is maintained substantially constant by using convection coding. This is permitted by having open grids (14) or meshes (24) above and below the fluorescent tubes (16) for natural ventilation. The convection of heated air creates a vertical air flow or 'chimney effect' which enhances the cooling of the tubes (16) without discomfort to the user. <IMAGE>

Description

SUN CANOPY The present invention relates to sun canopies and to sun beds incorporating sun canopies.

Sun canopies and sun beds help to produce a body tan without normal sunlight and generally consists of an array of fluorescent lamps producing light with a high proportion of ultra-violet output. This light is produced by phosphors giving an output mainly in the UV-A wavelengths regarded as being medically safe to use within recommended times of exposure.

Earlier sun canopies and sun beds were mainly designed for use in health clubs, saunas and the like and sun beds consists of a bed containing an array of lamps and a canopy also with an array of lamps so the user is exposed on all sides to the UV light. Of course, for the canopy the bed is omitted so that the user is exposed to W light from above. Typically the number of fluorescent tubes used might be between 3 or 4 (for a canopy only) to 30 or more for a sun bed. Each tube is normally controlled by an inductive 'ballast' and start switch and is of 85 to 140 W. rating. The weight of each ballast is normally around 1.5 to 2 kilogrammes so the apparatus becomes extremely heavy and has to be of robust construction particularly in the canopy part which is normally arranged to be moved to allow the user access to the bed.

A further disadvantage of these existing structures apart from the weight is the considerable heat generated both in the lamps and particularly in the ballast apparatus. This heat has two disadvantages; firstly, there may be discomfort to the user, and secondly, the lamps have an optimum operating temperature (usually 38/40 degrees C) where the production of W-A light is most efficient. If the lamp is run below or is heated beyond this temperature the production of W-A falls considerably leading to ineffective use of the apparatus.

The heat produced means that such devices must be well ventilated and this requires the addition of fans which add to the heat and noise and weight, which contributes additional sources of discomfort, especially when cold air is initially produced. In addition, the cooling of long fluorescent tubes requires careful design so that excess cooling does not occur at one end and too little at the other, resulting in a temperature difference along the tube providing non-uniform W radiation leading to non-uniform exposure and tanning. In addition, the reflector may tend to focus the UV radiation undesirably on one area of the body causing potential localised burning and increased risk of skin cancer.

The weight and heat produced normally make these devices static and in the applications outlined above the disadvantage of this is generally acceptable. However, it will be clear that if such apparatus could be made lighter and require less ventilation it may be made portable with advantages for domestic applications.

In a conventional sun canopy assembly the tubes are mounted inside a box with a closed top which often contained a metal reflector behind the tubes to control direction of light emission. For safety a W transmissive front panel beneath the tubes is mounted in case of the rare possibility of a broken tube. This closed construction requires ventilation or it will cause over-heating of the tubes and this adds further weight and noise to the unit.

Conventional canopies have, because of their heavy weight, required a strong construction and metal support; a typical support might be a steel tube in a friction bearing running across the top of the canopy at the centre of gravity. The tube is bent or fabricated to a vertical position and can be used as part of a telescopic height adjustment by sliding within a corresponding tube in the base section. This is extended to carry the feet and castors, and is necessarily heavy and bulky and an awkward shape to transport. If conventional ballasts are used in the canopy itself the weight may be balanced by a gas-strut or similar device. If the ballasts are carried in the base a considerable number of electrical connections have to be safely routed through or around this height adjusting and tilting mechanism, adding cost and complexity.

The increasing use of sun-tanning devices has led to its use domestically and in hiring units for use in the home. As such devices have a necessity to be portable, the weight and heat disadvantages become very important.

Generally, units designed for this purpose consist of a canopy only, which can be moved above a bed or a similar piece of furniture on which the user lies. The canopy is designed to be adjustable in height and to be moved on castors on a foot assembly so that it can be removed for storage. Usually the lamp assembly can be moved to a vertical position for storage or for use by someone standing or sitting. The canopy feet are arranged to extend under the bed to enable the weight of the canopy to be transferred to the floor. This construction is necessary because of the weight of the canopy which cannot be easily lifted and can only be moved by pushing the unit around on castors. In addition, the canopy tends to be top-heavy and may easily topple over while being moved.

While domestic units may be made with as few as three or four tubes it is desirable, in order to give an efficient tanning operation, a minimum of six and preferably eight tubes are necessary. With conventional inductive ballasts to control each tube the weight of the control apparatus is in the order of 16 kilogramms and the robust construction necessary to carry this plus the ventilation fans makes the total weight of the apparatus around 25 kilogramms (55 Ibs).

An object of the present invention is to provide an improved tanning device which obviates or mitigates the aforesaid disadvantages.

This is achieved by providing a sun-tanning device which is portable because of the use of a light weight electronic ballast and which provides substantially uniform W radiation because the fluorescent tube temperature is maintained substantially constant by using convection cooling. This is permitted by having open grids or meshes above and below the fluorescent tubes for natural ventilation. The convection of heated air creates a vertical air flow or "chimney effect" which enhances the cooling of the tubes without discomfort to the user.

In a preferred arrangement the sun-tanning device is a canopy and the grids or meshes are coated with reflective material to decrease UV dispersion from the desired area to the irradiated. This provides a concentration of W but with very even distribution (ISO irradiance) over the subject. The canopy is generally planar and has a plurality of parallel fluorescent tubes with an associated electronic ballast at one end. The canopy has two pivotable legs spaced along its length which can be swung into an in-use position to support the canopy in a cantilevered manner above a bed, or swung into a storage position in the same plane as the canopy. The legs also permit the canopy to be disposed in a vertical position for tanning standing subjects.

The grids or meshes are generally plastic or thin metal or a honeycomb structure to give the necessary rigidity with little additional mechanical support. The tubes can also have reflective or silvered coatings to enhance the amount of W radiation to be directed to the subject.

According to one aspect of the present invention there is provided sun-tanning apparatus comprising a housing for containing a plurality of ultra-violet (UV) light emitting sources, electronic drive means connectable to a source of power for energising said UV light emitting sources, said housing having at least a lower surface provided with passages to permit air to pass therethrough so that, in use, when said W light emitting sources are energised air passes through said passages providing cooling of said sources.

Preferably said W light emitting sources are W fluorescent tubes. Alternatively said UV light emitting sources are quartz arc lamps with a parabolic reflector and 'Fresnel' type sectional lenses of pressed aluminium or metalised plastic or variable angle louvre reflectors.

Preferably also, said electronic drive means is suitable lightweight electronic ballast means.

Preferably, the electronic ballast has multiple outputs to drive the array of W light emitting sources and includes internal timing means. Preferably also, said ballast is arranged to switch off after treatments being re-settable only by switching off at the mains supply to avoid miss-use.

Preferably also, said housing is generally planar.

Conveniently, said housing is curved with the irradiating surface being concave relative to the subject being irradiated.

Preferably, the passages are provided by open frameworks forming a lower surface an -an upper surface of the housing so that air is drawn by convection from the bottom to the top of the housing. Conveniently the housing is a canopy.

Preferably also, the canopy has leg means for supporting the canopy and are movable between an in-use position and an out-of-use position, so that in the in-use position the legs support the canopy in a cantilevered fashion and in the out-of-use position the legs are stored in the same plane as the canopy.

Also, the open frames or meshes and the fluorescent tubes may be reflective so that the W light directed towards the subject is maximised.

These and other aspects of the invention will become apparent from the following description when taken in combination with the accompanying drawings in which: Fig. 1 is a diagrammatic view of an embodiment according to the present invention; Fig. 2 is a partly enlarged longitudinal section taken on the lines 2-2 of Fig. 1; Fig. 3 is an end view of Fig. 1; Fig. 4 is a plan view of Fig. 3 with the legs stored; Fig. 5 shows a side view similar to Fig. 2 with the canopy disposed in a vertical position; and Fig. 6 is an enlarged cross-sectional view taken on the lines 6-6 of Fig. 1.

Reference is first made to Figs. 1,2 and 6 which shows the construction of the canopy light box 10 and ballast assembly 12. The canopy 12 consists of a reflective grid or open frame 14 of deep construction above which are mounted the UV emitting fluorescent tubes 16 which also reflect W light. A suitable material for the grid 14 is plastic or aluminium having a mesh of approximately the same width as the depth. A depth of about 12mm to 20mm (one-half inch to three-quarters of an inch) is suitable.

The grid 14 slots into a surrounding wall 18 which is deep enough to box the fluorescent tube assembly between plates 20 and the two parts are rigidly attached by adhesive clips, or other methods so as to give a rigid box construction with an open top end 22 with the grid 14 acting as the base. The walls 18 of the box are preferably constructed of rigid formed plastic, structural foamed plastic which may be extruded or moulded in a well known manner, or lightweight metal or wood.

The top of the box is closed by a light reflective mesh screen 24 which fits tightly into a recess 26 in the wall top. If necessary this screen 24 may be reinforced at intervals along its length by spacers 18 (best seen in o Fig. 6) running across the width of the box which are made to fit tightly between the insides of the longer length walls, so as to give additional strength to the construction. These spacers have slots 30 to allow the tubes 16 to pass through. The top 22 (with spacers) is held in place by clips, dzus fasteners or similar devices (not shown) and the assembly is easily removable for the replacement of tubes as required. Alternatively, this top section 22 may be made from the same deep grid material 14 as the lower diffuser to enhance the rigidity of the whole assembly and the "chimney effect" or convection cooling.

Control of the lamps 16 is by the electronic ballast assembly 12. This ballast 12 supplies current to the tubes at a relatively high frequency (around 25/45 KHZ) which, as is known, has an enhanced light output, due to better#retention of the discharge in the tube and gives a more even and cooler light emission. In fact the tubes heat faster than when fan cooled but do not overheat on prolonged use maintaining the UV output in comparison to uncooled beds such that after (say) 20 minutes operating the output of UV may be as much as 50% (or more) higher than for the equivalent uncooled unit.

This ballast assembly 12 is very light (approximately 650 grams) and may be preferably mounted at one end of the canopy 10 as shown in Fig. 1. Alternatively, it may be mounted along the side. Tube holders 19 are mounted#to the plate 20 at each end of which may be a printed circuit board to simplify interconnection. The electronic assembly 12 may be mounted to plate 20 (when at one end) so as to be easily dismounted for assembly, repair or replacement. Connection to the end plate may be by plug and socket (not shown) to simplify wiring, and to the far end by ribbon cable or loom (also with plug and socket if desired). The sockets or holders may be resiliently mounted to protect the tubes.

In one form of construction the electronic assembly 12 is contained in a metal box 10 which may be ventilated top and bottom and the plates 20 carrying the tube holders 19 used as the fourth side of the canopy 10 with the electronics mounted outside the grid-box combination.

Alternatively, the grid and box may be extended to include the electronics assembly and a metal box or screen is useful to reduce any possibility of radio interference from the ballast. In fact, the metalised grid and mesh on the canopy effectively screen the tubes allowing even higher frequencies of operation to be used, thus reducing size and weight and enhancing efficiency still further.

In use, energisation of the W tubes 16 causes emission of the W radiation and the tubes 16 heat up. As air around the tubes is heated it rises through the mesh 24, thus drawing in cooler air from beneath grid 14 through grid 14. This cooler air cools the tubes 16 and this 'ventilation' by convection results in an average tube temperature of about 38/400C along the tube providing uniformity of UV radiation for tanning. The reflective grid 14, mesh 24 and tube 16 decrease dispersion losses and enhance the radiation supplied to the subject.

Reference is now made to Figs. 1,3,4 and 5 of the drawings in which two L-shaped legs 32 are attached to one side 34 of the canopy 10 by friction locks 36 which can be opened to-allow the legs to swivel. Additionally, if required the legs can be altered in length by sliding them through the friction lock. Both legs can be attached to the middle of the canopy via a common friction device, adjustment of these legs can be made to alter the height of the canopy above the bed and it can be arranged to be higher at one end if required. when the canopy is supported by the bed itself feet 38 having non-slip grips 40 can be arranged to be outside the area in which the user lies. Both legs 32 are attached to side 34 of the canopy to allow access from the other side 35.

This form of construction enables the feet 32 to be folded to be in line with the canopy 10 itself as shown in Figs. 3 and 4. This makes the device with a height of around four inches, or less and allows the canopy 10 to be hand carried or stored for example under a bed when not in use. In contrast to conventional units which require to be stored in a corner of the room to prevent the feet protruding into the room space. Alternatively, as seen in Fig. 5, the canopy can be held in the vertical position by supporting it on one foot 38 and a buffer at the end of the canopy 10.

The attachment of the legs 32 to the canopy 10 may have a further degree of relative movement allowing the canopy 10 to be tilted on its side (relative to the legs) to a vertical position. This would enable a user to lie in position and lower the canopy. However, because the weight of the canopy is so small it is simple, if better access is required, to lift the canopy in order to get underneath. This also allows the user a further degree of freedom in that, with the tilting friction hinge set to a near vertical position, they can lie on their side to receive a tan. This is of advantage for those users who find it difficult, unpleasant or medically undesirable to lie on their front.

Various modifications may be made to the embodiment hereindescribed without departing from the scope of the invention. For example, a further means of mounting, storage and use enabled by the very light weight is to suspend the canopy 10 form hooks attached to the ceiling joists by means of a cord and pulley system, (which would preferably be of the 'friction' type), since the most common place of use tends to be over a bed, for example.

This allows the bed simply to be raised up by the cord and pulley system to the ceiling to be out of the way for storage. The legs may be fitted with a second hinge or mounted on the canopy ends to enable the bed to be pivoted. Also, the lower grid may be uncoated plastic having an opalescent surface; alternatively the grid may be plated, for example, in a metallic finish which reflects the light passing through to concentrate the light in the optimum direction. The grid shape and dimensions are such that light impinging on it at an angle of 45 degrees or less to the surface of the bed will be cut off from spilling to the sides of the bed and will be reflected onto the user. The mesh screen forming the top of the box may be punched sheets of metal or plastic.

-It will be obvious -that the type of construction described ventilates both the tubes and the electronic ballast in a simple and effective way. This is enhanced by the 'chimney effect' of the deep grid. Also the use of a high frequency supply ensures that heat loss in thetubes is less than the loss in the tubes when used at normal supply frequencies. The electronic ballast itself is much more efficient and therefore heat removal from the ballast is also much easier.

The construction described thus gives a rigid structure of very light weight which can adequately carry and support the fluorescent tubes. However, it may be of advantage to allow one or both ends of the tubes to float with a limited degree of freedom so that no stress can be applied to the tubes in the event of severe bending or twisting forces being inadvertently applied.

Further features of the invention relate to the electronic ballast and are concerned with safety of operation as follows. In conventional sunbeds the exposure time is usually set on a mechanical timer-which is turned to a desired setting and which turns back to zero when it alarms the user. While such units are normally reliable they have been known to stop (or the user to reset them) before reaching the zero-time 'OFF' position causing the user to have the risk of a longer than desirable exposure. The electronic ballast circuit may include a 'Back-Up' timer, to switch off in a fixed maximum safe time even if the normal timer fails.

However, an electronic timer, preferably with a digital readout, is easily and cheaply obtained because it can use the ballast power supply and internal power devices tQ switch on and off. Such a timer may be set by push buttons and indicates the set time in minutes and the time still to go at any point in the response period. An additional refinement is for the electronic timer to have a memory so that the use of a second button will immediately repeat an already set exposure. Furthermore the ballast may be arranged to switch lamps off completely after two sessions (front and back) requiring user to reset at main switch. This reduces the chance of miss-use. The digital display would normally. be mounted on the end of, or beside the ballast where it can be seen by the user.Alternatively it could be mounted on a movable flap which would enable it to be read both from below and from outside the canopy.

The ballast control circuit can be arranged to dim the W intensity down to about a fraction of full value. A push button control of this enables user with sensitive skins to set a light level to suit their requirements thus adding a second safety feature.

A further safety feature relates to the fluorescent tubes. It is known that in the event of a tube failure that a high voltage can produced by the series resonant circuit used to power the tubes. The electronic ballast circuit is arranged such that when a tube fails (normally to open circuit) or if a tube is taken out of circuit, that this voltage is suppressed to a safe value.

Additionally a switch operated by removal of the top mesh cover can be arranged to cut off the supply. However, this would not normally be necessary.

A further advantage of the electronic ballast in combination with a light weight canopy is obtained by running the tubes at a higher current than normal. By such means a greater light output can be obtained without overheating. It has been established that the tube life is substantially longer with the electronic supply than with conventional 50 HZ mains supply so this can be used without prejudice to the useful life of the unit. The extra light obtained can be used to give the same output from six tubes as would be obtained from, say, eight tubes as in a normal unit. Thus, a further saving, in size, weight, and energy consumed is obtained. The saving in size and weight allows a bed design which may be arranged to fold in half for transport and storage.

While the embodiment has been described with relation to sun canopies only, many of the advantages described can also be obtained by applying the principle to sunbeds.

For example, the canopy can be made lighter and more easily adjusted. In addition, the benefits obtained and the controls available from electronic ballasts are equally applicable to sunbeds. These include time control and intensity control and the safety features.

Claims (14)

CLAIMS:

1. Sun-tanning apparatus comprising a housing for containing a plurality of ultra-violet (W) light emitting sources, electronic drive means connectable to a source of power for energising said W light emitting sources, said housing. having at least a lower surface provided with passages to permit air to pass therethrough so that, in use, when said UV light emitting sources are energised air passes through said passages providing cooling of said sources.

2. Sun-tanning apparatus as claimed in-claim 1 wherein said W light emitting sources are W fluorescent tubes.

3. Sun-tanning apparatus as claimed in claim 1 wherein said W light emitting sources are quartz arc lamps with a parabolic reflector and 'Fresnel' type sectional lenses.

4. Sun-tanning apparatus as claimed in any preceding claims wherein said electronic drive means is a lightweight electronic ballast means.

5. Sun-tanning apparatus as claimed in any preceding claim wherein said electronic means has multiple outputs to drive the array of W light emitting sources and includes internal timing means.

6. Sun-tanning apparatus as claimed in claim 4 or claim 5 wherein said electronic ballast means is arranged to switch off after a preset number of treatments and being re-settable by switching off a mains supply when connected thereto.

7. Sun-tanning apparatus as claimed in any preceding claim wherein said housing is generally planar.

8. Sun-tanning apparatus as claimed in any one of claims 1 to 6 wherein said housing is curved with the irradiating surface being concave relative to the subject being irradiated.

9. Sun-tanning apparatus as claimed in any preceding claims wherein said passages are provided by open frameworks forming a lower surface and an upper surface of the housing so that air is drawn by convection from the bottom to the top of the housing.

10. Sun-tanning apparatus as claimed in any preceding claim wherein said housing is a canopy.

11. Sun-tanning apparatus as claimed in claim 10 wherein said canopy has leg means coupled thereto for supporting the canopy in a raised generally horizontal position.

12. Sun-tanning apparatus as claimed in claim 11 wherein said leg means are coupled to one side of the canopy and are movable between an in-use position and an out-of-use position so that in the in-use position the legs support the canopy in a cantilevered fashion and in the out-of-use position the legs are stored in the same plane as the canopy.

13. Sun-tanning apparatus as claimed in claim 9 wherein said open frameworks and said fluorescent tubes are reflective to maximise UV radiation directed towards the subject.

14. Sun-tanning apparatus substantially as hereinbefore described with reference to the accompanying drawings.