GB1602734A - Electrically-powered heating panels - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRICALLY-POWERED HEATING PANELS (71) We, THERMONEI"IE APPLIANCES LIMITED, of 68, Compstall Road, Romiley, Cheshire, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electrically-powered heating panels.

As used herein, the term "electricallypowered heating panel" is intended to include electrically-powered under-carpet heaters, blankets, mattresses and pads. The invention is particularly applicable, however, to electricallypowered blankets, or, more simply, "electric blankets".

In our Patent No. 1,456,684, there is described and claimed an electrically-powered heating panel comprising a tortuously-disposed dual coil heating element interlocated with a tortuously-disposed single coil heating element.

As used in Patent No. 1,456,684 and as used herein, a "dual coil heating element" is defined as an inner heating coil covered with insulating material with an outer heating coil wound on the insulating material and a "single coil heating element" is defined as a single heating coil covered with insulating material.

According to the present invention, an electrically-powered heating panel comprises a tortuously-disposed dual coil heating element (as herein defined) interlocated with a tortuouslydisposed single coil heating element (as herein defined), wherein energy regulator means are provided to control the energy input into the panel, said energy regulator means being operable so as to switch power to the panel on and off cyclically, the duration of the on/ off periods being controllable.

Examples of such electrically-powered heating panels will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 shows, in circuit diagram form, a panel according to the invention claimed in said Patent No. 1,456,684, and Figures 2, 3 and 4 show differing energy regulator means for the panel of Figure 1.

With reference to Figure 1, an electricallypowered heating panel comprises a dual coil heating element 1, 2 disposed tortuously over the area of the panel and interlocated with a tortuously-disposed single coil heating element 3. Insulation between coils 1 and 2 is indicated by the numeral 7. Electrical connections to the panel of Figure 1 are taken at points X and Y.

The dual coil heating element 1,2 is a know element and customarily comprises an inner coil wound on a rayon core and covered with an insulating sheath (which is insulation 7), such as P.V.C., and an outer coil wound on the insulating sheath and itself covered with an outer insulating sheath.

For further details of the panel construction, reference may be made to Patent No. 1,456,684, these details not being repeated herein as the present invention is directed to circuit details rather than constructional details. However, it is relevant to note that in the event of overheating in the panel, such as by energising it when folded or bundled, the inner insulating sheath 7 of the dual coil heating element becomes conductive or melts whereby current can flow between coils 1 and 2 so that a lowresistance circuit from line to neutral is set up which will cause a fuse to blow.

Figure 2 shows one way in which the energy input into the heating panel of Figure 1 can be regulated. There is provided an oscillating on-off switch 9 which causes heating current to flow through the coils 1, 2, 3 in pulse form. The switch 9 is thermally actuated and comprises a pair of bi-metallic contacts 15 and a heater 16 for heating the contacts. Output of the heater 16 is adjustable by a rheostat 17.

The contacts 15 are intially closed and open when current flowing through the heater 16 has heated the contacts sufficiently. Current flow through the heater 16 then ceases until the contacts 15 have cooled sufficiently to close once again. Typically, the "on" and "off' periods of current flow each comprise 10 minutes.

The circuit of Figure 2 is connected to the panel of Figure 1 at the points X, Y. Power input is made at pointsA, B. A fuse F is included.

Figure 3 shows an alternative way in which the energy input into the heating panel of Figure 1 can be controlled. There is provided energy regulator means in the form of a Thyristor 30 which is switched on and off by an RC timing circuit comprising a variable control resistor 31 and condenser 32 acting through a diode 33 on the Thyristor 30. A fuse F is included. As with the circuit of Figure 2, an on/off input is received at the heating panel, the length of the on/off periods being controllable by control resistor 31 adjustment.

Figure 4 shows a further alternative way in which energy input can be regulated. As with the circuits of Figures 2 and 3, an on/off input is provided with control of on/off duration.

This input is provided by a Triac 40 triggered through a Diac 41 from a RC timing circuit comprising a condenser 42, control resistor 43 and fixed resistor 44.

The coils 1, 2 and 3, and fuse F are preferably disposed in the panel so as to be replaceable as a unit. The cost of such a unit can be low relative to the cost of the whole heating panel and hence a long-life panel can be provided with a high level of protection against fire hazards.

The panel 1 can be constructed using tunnelconstructed blanket material.

WHAT WE CLAIM IS: 1. An electrically-powered heating panel comprising a tortuously-disposed dual coil heating element (as herein defined) interlocated with a tortuously-disposed single coil heating element (as herein defined), wherein energy regulator means are provided to control the energy input into the panel, said energy regulator means being operable so as to switch power to the panel on and off cyclically, the duration of the on/off periods being controllable.

2. A panel as claimed in Claim 1, wherein the power switching is derived from a thermal switch having a control resistor.

3. A panel as claimed in Claim 1, wherein the power switching is derived from an electronic three-terminal switch under the control of an adjustable RC circuit.

4. A panel as claimed in Claim 3, wherein the three-terminal switch is a thyristor.

5. A panel as claimed in Claim 3, wherein the three-terminal switch is a triac.

6. An electrically-powered heating panel as claimed in Claim 1, substantially as hereinbefore described with reference to Figure 1, taken with any one of Figures 2, 3 or 4 of the accompanying drawings.

7. A panel as claimed in any preceding claim in the form of an electric blanket.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. Thyristor 30 which is switched on and off by an RC timing circuit comprising a variable control resistor 31 and condenser 32 acting through a diode 33 on the Thyristor 30. A fuse F is included. As with the circuit of Figure 2, an on/off input is received at the heating panel, the length of the on/off periods being controllable by control resistor 31 adjustment. Figure 4 shows a further alternative way in which energy input can be regulated. As with the circuits of Figures 2 and 3, an on/off input is provided with control of on/off duration. This input is provided by a Triac 40 triggered through a Diac 41 from a RC timing circuit comprising a condenser 42, control resistor 43 and fixed resistor 44. The coils 1, 2 and 3, and fuse F are preferably disposed in the panel so as to be replaceable as a unit. The cost of such a unit can be low relative to the cost of the whole heating panel and hence a long-life panel can be provided with a high level of protection against fire hazards. The panel 1 can be constructed using tunnelconstructed blanket material. WHAT WE CLAIM IS:

1. An electrically-powered heating panel comprising a tortuously-disposed dual coil heating element (as herein defined) interlocated with a tortuously-disposed single coil heating element (as herein defined), wherein energy regulator means are provided to control the energy input into the panel, said energy regulator means being operable so as to switch power to the panel on and off cyclically, the duration of the on/off periods being controllable.

2. A panel as claimed in Claim 1, wherein the power switching is derived from a thermal switch having a control resistor.

3. A panel as claimed in Claim 1, wherein the power switching is derived from an electronic three-terminal switch under the control of an adjustable RC circuit.

4. A panel as claimed in Claim 3, wherein the three-terminal switch is a thyristor.

5. A panel as claimed in Claim 3, wherein the three-terminal switch is a triac.

6. An electrically-powered heating panel as claimed in Claim 1, substantially as hereinbefore described with reference to Figure 1, taken with any one of Figures 2, 3 or 4 of the accompanying drawings.

7. A panel as claimed in any preceding claim in the form of an electric blanket.