GB2172393A - Heating installation - Google Patents

Abstract

A local heating installation intended for use with furniture such as a chair incorporates a panel 17 of flexible material in which is embedded a flexible tube 22, 23, 26, 27. An electrical heater 24 is arranged to heat liquid in the tube and circulate it through the tube by natural convection. A reservoir constituted by loop 30 by virtue of a by-pass connection 20 is arranged in such a position as to collect air or gas which may separate out from the liquid so that natural convection is still effective despite this separation. <IMAGE>

Description

SPECIFICATION Local Heating Installations The invention relates to local heating installations.

It is becoming increasingly important in view of increased energy costs and diminishing energy resources to provide a means for keeping inactive people acceptably warm as efficiently as possible, that is in return for a minimum energy usage. This problem is particularly acute with old people who tend to be inactive, tend to suffer more than other people from the effects of cold and in many cases have low incomes and live in older homes which are difficult to heat efficiently.

Conventional methods of providing for inactive people, other than those who are in bed, involve some form of room heating appliance such as central heating involving hot air distribution or hot water circulation or room heating devices powered by electricity or a locally combusted fuel. In heating a whole room, a large amount of energy is dissipated and it would be advantageous to provide a local heating installation tailored to the needs of the person concerned. Such a local heating installation, heating less than the complete room, would enable different people in the room to be heated to different extents.

It has already been proposed in our published UK patent application 21 32334A to provide a local heating installation comprising a panel of flexible material, fluid flow passages within the panel and an electric heater for supplying heated fluid to the passages and causing it to circulate through the passages. The panel is attached, in use, to a chair or a bed to provide local heating for an occupant. One problem which has arisen with this kind of heating installation, particularly when the fluid is water based, is to achieve effective fluid circulation over a reasonable life of the installation, without recourse to a mechanical pump.

In accordance with the present invention there is provided a local heating installation comprising a panel of flexible material; a liquid flow path within the panel; a heater for liquid in communication with the liquid flow path so as to form a closed loop therewith and adapted to be positioned sufficiently low down in relation to the panel to cause heated liquid from the heater to circulate around the loop by natural convection; and a reservoir in communication with the loop and arranged above the level of the heater in such a position asto collect air to gas which may separate out from the liquid.

The panel may be formed of foam plastics material having embedded therein at least one flexible tube providing said fluid flow passages. The passages may comprise a single tube laid out in a zig-zag pattern with a by-pass connection for the top section of the zig-zag to thereby define the reservoir above the by-pass connection.

Preferably the heater is an electric heater.

The panel may be of such a shape and size as to fit conveniently over a chair back and the seat portion of the chair may be provided with securing means such as fixing tapes for holding it in position. An electrical heater may be mounted to the lower part of the chair whereby heated fluid circulates through the panel by natural convection.

Particularly when the panel is intended to be laid flat, as on a bed, so that there is no part of the panel which is significantly higher than other parts, the heater may comprise a primary chamber incorporating an electric heater element and a liquid space surrounding the element, a reservoir chamber arranged above the primary chamber such that air or gas bubbles forming at the surface of the element can rise into the reservoir chamber, at least one outlet from above the heater element but below the reservoir chamber leading to the flow path in the panel and at least one inlet to the chamber below the heater element returning from the flow path.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic perspective view of a chair on which has been installed a local heating installation in accordance with the invention; Figure 2 shows in greater detail an electric heater unit employed in the installation of figure 1; and Figure 3 shows an alternative form of heater unit particularly suitable for an installation intended for use on a bed.

Figure 1 shows a conventional armchair with a seat portion 11, a back rest 12, rear legs 13, front legs 14, arms 15 and arm supports 16. A relatively upright chair with open arms has been chosen for purposes of illustration because it enables the invention to be explained more readily but it should be understood that the invention may be applied to chairs with upholstered, closed-in arms and without separate legs. The use of such chairs can help to confine locally generated heat and improve the effectiveness of the invention.

The chair shown is fitted with a flexible heater panel 17 which covers substantially the whole of the seat portion 11 and back rest 12. The panel also extends down as shown at 19 in front of the seat portion. Various ties 21 hold the panel in position by securing it to the rear legs 13, arm supports 16 and other parts of the chair. The panel is comprised of a flexible elastomeric material and in this example it is constituted by a foam plastics material such as polyurethane foam. Embedded in the foam is a single tube of flexible plastics material. The tube incorporates a zig-zag run running continuously from the lower front to the upper rear part of the panel, part of the zig-zag being omitted from the drawing in the interests of clarity.A return run 23 of the tube within the panel 17 extends down and along one side edge of the panel and then traverses the lower front edge of the panel to emerge therefrom adjacent to the beginning of the zig-zag run 22. The main flow loop formed by the tube by-passes the top section 30 of the zig-zag run 22 by virtue of a short by-pass connection 20 crossing from the second zig-zag section to the return run. The top section 30 forms a reservoir for a purpose to be described.

It is convenient to mould the panel with a narrow necked groove in its upper surface so that the tube can be clipped in to the groove.

An electrical heater 24 is secured by straps 25 to a front leg of the chair below the seat portion 19. The upper part of the heater 24 is connected at 26 to the beginning of zig-zag tube run 22. The return tube run is connected to the lower end of the heater at 27. In this way the tube and the interior of the heater together form a closed loop for the flow of liquid.

The materials selected for the panel 17 should be such that they do not deteriorate when heated over long periods to temperatures of the order of 65"C.

The whole of the panel, including liquid in the tube normally operates at lower temperatures than this but it is essential that the materials do not deteriorate, for example by becoming brittle, underthe influence of temperatures normally encountered.

The panel is covered with a surface of textile material corresponding to that normally employed as upholstery fabric.

Further details of the electrical heater unit 24 are shown in Figure 2. The heater unit comprises a main tubular body 31,formed for example from copper tubing. At its lower end, main body 31 is closed by a bush 32 which incorporates both a fluid connection 27 to the panel (see figure 1) and a mounting aperture 33 within which an electrical heater element 34 is installed. The heater element 34 is kept separate from the interior of main body 31 by a further copper tube 35 having an upper end closed by end plate 36. Electrical leads 37 provide a power supply to the heater element.

At its upper end, the main tubular body 31 is closed by an end cap 38 to which is connected a pipe section 39 leading to an airlock 41 through which air can be bled from the system and a connection 26 to the zig-zag run as illustrated in Figure 1.

In use, the electrical heater unit and the tube 22,23 are filled with a liquid which may be water with suitable additives or may be a stable organic fluid.

Water with an ethelene glycol additive to avoid freezing is particularly useful. When the installation is fitted on a chair as shown in Figure 1 and the heater is connected to an electrical supply, the heated fluid becomes less dense than cooler fluid and rises up through the zig-zag tube 22 to supply heat to the panel 17. As the liquid cools and contracts, it returns down the tube run 23 to the heater. In this way, continuous circulation is established so that heat generated in the unit 24 is distributed throughout the panel 17. Near the top of the panel, some heated liquid may flow around the reservoir constituted by top section 30 but much of the flow passes from the zig-zag section 22 to the return run 23 via the by-pass connection 20.

There is a tendency for air or other gas to be in solution in the liquid with which the tube is filled, particularly but not exclusively if this is water-based.

Expedients such as boiling tend to reduce the inclusion of air but not to eliminate it. Thus there is a tendency for airto be driven out of solution atthe heater and for this air to rise to the top section of the tube and accumulate there. In the absence of the by-pass connection 20 and reservoir 30, accumu la- tion of air (or other gas) in the top section of tube would result in flow breaking down and thus would prevent heat distribution to the panel at a satisfactory rate. However, the air accumulates in the reservoir above the main flow path through the by-pass connection 20 with the result that liquid continues to flow around the system through connection 20, despite the presence of a substantial volume of air.

In a modification, the heater unit 24 may be attached to a back leg 13 of the chair and the flow path may be up the chair back, down the chair back and out to the front edge of the seat portion, returning across the seat cushion to the heater. In a further alternative the heater unit 24 may be embedded in the panel 17 near the base of the backrest.

It has been found that a power of approximately 50 watts is sufficient to apply enough heat to the panel 17 to significantly warm a person sitting on the chair.

The heating effectforthe person is of course improved if the chair is more closed in and this is particularly so if the chair or the heating panel incorporate some means for partially surrounding the head of the occupant of the chair because the head is a region from which a substantial proportion of body heat escapes. The foam plastics material and textile fabric of the panel result in gentle distribution and transfer of heat from the tubes and the textile fabric also provides a comfortable and attractive appearance. A temperature sensor attached to the outside of the heater unit and set to switch off the electrical supply when the temperature reaches 55"C is particularly suitable. Normally the installation will be used in conjunction with a chair for elderly or otherwise immobile persons who require to be kept warm at low cost.The system may also be used in conjunction with a chair in situations where an elderly and immobile person is living in the same household as more fit persons and where the elderly person requires more warmth than other occupants of the same home.

In a further modification, the panel may be intended for laying on the surface of a bed for heating an occupant of the bed. The fact that the electrical heater is away from the occupant of the bed, for example by being mounted under the bed, renders this installation much more safe than an electrical blanket. This is particularly so when the whole of the panel including its liquid are constituted of materials which are electrical insulators. The risks of electrocution and of fire are both substantially reduced.

However, a problem which arises in relation to an installation for a bed is that with the panel horizontal, there is no clearly defined upper region in which air will collect and which can thus be by-passed to provide a reservoir.

Figure 3 shows an alternative form of heater unit incorporating a reservoir for air to replace a reservoir formed in the upper part of the panel. The heater unit comprises a primary chamber 42 in the form of a horizontal tube containing a horizontal electrical water element 43 within a sleeve 44. An 80 watt heater is suitable for a single bed. Both ends of the tube are closed off, the heater element being mounted by one of these ends. A reservoir chamber 45 is positioned above the primary chamber 43 and is in the form of a tube corresponding to that of the primary chamber, with closed offends but without the heater element. A further connecting tube 46 extends vertically between the two chambers 42 and 45.

Two outlets 47 and 48 lead from the connecting tube 46 to two flexible tubes 49 and 51 which lead to and are embedded in a flexible panel in the same way as described in relation to Figure 1, except that the panel is intended to lie horizontally on a bed. A return or inlet connection 52 has two branches 53 and 54 to which the return ends of the flexible tubes 49 and 51 respectively are connected. The two tubes 49 and 51 may be so arranged in the panel that one heats the head end of a bed and the other heats the foot end. As with the previous embodiment a temperature sensitive switch may be provided.

The panel is laid flat on a bed and the heater unit is secured to the bed in the orientation shown at a level below that of the panel.

The heater unit of Figure 3 may be constructed in any convenient way. For example, the chambers 42 and 45 together with connecting tube 46 may be made from two standard T shaped copper pipe connections soldered or brazed together and the end closures, inlets and outlets may also be brazed or soldered in position. As an alternative, suitable for production in large numbers, the unit may be injection moulded from plastics material.

In use, the complete system is filled with a water based liquid in which some air or other gas is likely to be dissolved. The air tends to come out of solution as the liquid is heated by formation of bubbles on the surface of the sleeve 44 surrounding the heating element. This air tends to rise up within the system and to be collected within the reservoir 45. Very little of this air passes into the outlet 47 and 48 with the result that natural convection between the heater unit and the panel can continue despite the collection of air in the reservoir 45.

With either embodiment it is desirable to boil the water prior to filling the system to drive off some air.

However some air or constituents of air remain in the water and then in use of the installation this collects in the reservoir.

Claims (9)

1. A local heating installation comprising a panel of flexible material; a liquid flow path within the panel; a heater for liquid in communication with the liquid flow path so as to form a closed loop therewith and adapted to be positioned sufficiently low down in relation to the panel to cause heated Iqiuid from the heater to circulate around the loop by natural convection; and a reservoir in communication with the loop and arranged above the level of the heater in such a position as to collect air or gas which may separate out from the liquid.

2. An installation as claimed in claim 1 wherein the panel is formed of foam plastics material having embedded therein at least one flexible tube providing said fluid flow passages.

3. An installation as claimed in claim 2 wherein said passages comprise a single tube laid in a zig-zag pattern with a by-pass connection for an end section of the zig-zag intended to be elevated above other parts to thereby define the reservoir above the by-pass connection.

4. An installation as claimed in any one of the preceding claims wherein the heater is an electric heater.

5. An installation as claimed in any one of the preceding claims wherein the panel is of such shape and size to fit conveniently over a chair back and the seat portion of the chair and is provided with securing means for holding it in position to a chair.

6. An installation as claimed in claim 5 including an electrical heaterfor the fluid adapted to be secured to a lower part of the chair whereby heated fluid circulates through the panel by natural convection.

7. A heating installation as claimed in claim 1 wherein the heater comprises a primary chamber incorporating an electric heater element and a liquid space surrounding the element, a reservoir chamber arranged above the primary chamber such that air or gas bubbles forming at the surface of the element can rise into the reservoir chamber, at least one outlet from above the heater element but below the reservoir chamber leading to the flow path in the panel and at least one inlet to the chamber below the heater element returning from the flow path.

8. A heating installation as claimed in claim 7 wherein the primary chamber is a horizontal tube, the reservoir chamber is a horizontal tube positioned above the primary chamber, a further tube interconnects the two chambers and the outlet is connected in to the further tube.

9. A heating installation substantially as described with reference to and as illustrated by Figures 1 and 2 or Figure 3 of the accompanying drawings.