GB2162409A

GB2162409A - Electrically-heated blankets

Info

Publication number: GB2162409A
Application number: GB8513891A
Authority: GB
Inventors: L C Owens
Original assignee: THERMONETTE APPLIANCES Ltd
Current assignee: THERMONETTE APPLIANCES Ltd
Priority date: 1984-07-24
Filing date: 1985-06-03
Publication date: 1986-01-29
Also published as: GB8513891D0; GB8418822D0

Abstract

With reference to Fig. 1, an electrically-heated blanket 10 comprises a tortuously disposed heating element 11 defining legs 13 running transversely between ends 12 and 14 of the blanket. Lateral spacing of the legs is non-uniform, changing progressively between the blanket ends 12 and 14. Thus less heat is generated at the head-end 12 of the blanket 10 than the foot-end 14 thereof. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electricallyheated blankets This invention relates to electrically-heated blankets.

According to the invention, an electricallyheated blanket comprises at least one tortuously disposed heating element defining a plurality of laterally-spaced legs, wherein spacing between the adjacent legs is non-uniform.

Two heating elements may be provided, wherein a leg of one element is interposed within the spacing of adjacent legs of the other element.

Advantages can be gained by providing the non-uniform leg spacing of the heating element(s). There is less heat generated at the foot of a bed by the occupant than in the rest of the occupied area of the bed. The invention provides that this non-uniform heat generation is adjusted by altering the disposition of heat generated in the blanket, so that, in use of the blanket, more heat per unit area is generated in the foot region of the bed than in other parts.

This heat distribution is preferably achieved by decreasing the leg spacing of that part of the heating element disposed in the foot region of the blanket.

The invention is applicable both to overblankets, (which are customarily powered all night), and to under-blankets, which are powered prior to occupying the bed.

The leg spacing of a heating element can progressively change, or zones can be provided of differing spacing.

The invention will now be described, by way of example only, with reference to the accompanying drawings, wherein Figs. 1 and 2 illustrate, in diagrammatic plan view, two electrically-heated blankets, each according to the invention.

Reference should also be made, for background purposes, to British Patent Specification No. 1,456,684, which discloses an electrically-heated electric blanket comprising a pair of tortuously disposed heating elements.

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.

With reference first to accompanying Fig. 1, there is shown thereby an electrically-heated blanket 10 having a single-coil flexible heating element 11 which terminates at the headend 1 2 of the blanket. The heating element 11 is tortuously disposed so as to define a plurality of laterally-spaced legs 1 3 in parallel array. The element 11 is embedded in the blanket 10 and is distributed over substantially the whole of the blanket area. The use of tunnel-constructed blanket material is preferred.

In all, the heating element 11 comprises eighteen legs 1 3 runnings transversely to the blanket between the head-end 1 2 and footend 14. At the head-end 1 2 of the blanket 10, the lateral spacing between adjacent legs 1 3 is typically 6 cms. At the foot-end 14 of the blanket 10, the lateral spacing between adjacent legs 1 3 is typically 3 cms. The leg spacing changes progressively between the blanket ends 1 2 and 14 and is thus nonuniform.

In an alternative arrangement of the Fig. 1 embodiment, the first ten legs 13, (starting from foot-end 14), have an equal leg spacing of 4.5 cms, (thus occupying 45 cms length of the blanket), and the remaining eight legs have a spacing of 8.5 cms (thus occupying 68 cms length of the blanket). Thus zones of different leg spacings are provided.

A control switch, (not shown), is connected to the heating element terminals 15, 16. The circuit is also provided with a fuse, (not shown).

Fig. 2 illustrates an electrically-heated blanket 20 comprising a double-coil flexible heating element 21 tortuously disposed over substantially the whole of the blanket area, and defining a plurality of laterally-spaced legs 23 in parallel array.

As in the case of the blanket of Fig. 1, the lateral spacing between adjacent parallel legs 23 of the element 21 progressivly changes between the head-end 22 and foot-end 24 of the blanket 20.

The dual coil heating element 21 comprises an inner coil wound on a central core of RAYON (R.T.M.) and covered with an insulating sheath of thermoplastics material. A suitable thermoplastics material is a polyethylene compound, such as ALKATHENE (R.T.M.) obtainable from l.C.I. Limited of the U.K., which enables electrical conduction to take place between the inner and outer coils at an elevated temperature. The outer coil is wound on the insulating sheath and itself covered with an outer sheath of insulating material such as polyvinyl chloride (P.V.C.).

A multi-heat selection switch, (not shown), is connected to the heating element terminals 30, 31, 32, 33. The switch has high, medium and low selector positions. The switch affects line and neutral connections of an A.C.

power supply. The circuit is also provided with a fuse, (not shown).

A typical blanket of the invention can have a heat output of 32 watts at the head and trunk zone, (which zone occupies two-thirds of the length of the blanket), and an equal heat output of 32 watts at the foot zone, (which zone occupies the remaining one-third of the blanket).

The legs of heating elements 11 and 21 need not be parallel.

Claims

1. An electrically-heated blanket, comprising at least on tortuously disposed heating element defining a plurality of laterally-spaced legs, wherein spacing between at least some of the adjacent legs of the element is nonuniform.

2. A blanket as claimed in Claim 1, pro- vided with two heating elements, wherein a leg of one element is interposed within the spacing of adjacent legs of the other element.

3. A blanket as claimed in Claim 1, wherein the lateral leg spacing of the heating element changes progressively.

4. A blanket as claimed in Claim 1, provided with zones of different leg spacing of the heating element.

5. A blanket as claimed in Fig. 2, provided with multi-heat selection means.

6. An electrically-heated blanket substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

7. An electrically-heated blanket substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

8. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.