Electric heating – Heating devices – With heater-unit housing – casing – or support means
Patent
1984-12-20
1986-12-09
Goldberg, E. A.
Electric heating
Heating devices
With heater-unit housing, casing, or support means
219217, 219202, 219549, H05B 334
Patent
active
046281886
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to electrical means in heating pads. Such pads are used for seats in vehicles, in the cabins of various public and industrial transport means. A heating pad may be placed loose on the seat or it may be built in to the back and seat of the chair itself. If a loose heating pad is used it consists of one section for the seat and one for the back-rest. In the case of built-in heating pads, too, there is one heating-wire loop for the seat and one for the back-rest. The heating-wire loops for seat and back-rest are normally connected in series. The series-connected heating wires cooperate with each other by means of a thermostat which connects and disconnects the current to the two heating loops. It has been found that when the current is disconnected a rather unpleasant phenomenon occurs in which there is a recoil of energy from the back-rest to the person using the seat with heating pad. The back of a user is extremely sensitive and such a recoil of energy is therefore injurious since, for instance, the blood vessels in the back may expand, so that the user may catch cold, particularly if he goes directly out into a cold atmosphere with an over-heated back.
The object of the present invention is to reduce to a minimum the possibility of an energy recoil from the back of the seat when the current is disconnected from the heating-wire loop in the back-rest. According to the invention, this is in practice solved in that the ratio between the resistance in the heating wire in the section of the heating pad located in the seat and the resistance in the heating wire located in the back-rest increases when current flows through. The total resistance in the section of the heating pad located in the seat shall thus be greater than the resistance in that part which is located in the back-rest.
It is also possible according to the invention to use a wire in the part of the heating pad located in the seat which has such properties that the resistance increases when a current flows through it, and at the same time use a heating wire in the pad located in the back-rest which has such material properties that its resistance remains constant or alters more slowly at increased temperature, e.g. thicker copper wire which does not acquire such a high temperature as the wire in the seat.
Further characterics of the present invention are revealed in the following claims.
The invention will be described further with reference to the accompanying two drawings in which
FIG. 1 shows in an exploded perspective the three parts forming a heating pad, and
FIG. 2 shows the heating pad when assembled in perspective.
FIG. 3 is an electrical schematic of a modified form of my invention.
In the drawings 1 is the bottom part of a heating pad, consisting of a seat section and a back-rest. The back-rest is designated 3 and the seat section 4. The bottom part may be of any suitably material. Foam plastic or woven fabric is preferably used. An top part 2 is also shown, consisting of a seat section 6 and a back-rest 5. The material in the top part 2 may be of the same type as the bottom part 1. An electrical heating unit 7 is placed between the bottom and top parts. The heating unit is formed by a wire arranged to provide two sections, a first section 11 for the seat and a second section 10 for the back-rest. The two sections are made from a single wire having a connection cable 8 and a plug-in contact 9. The wire in the two sections may be copper, for instance. The wire in section 10 is preferably thicker than that in section 11. The wire in section 10 may thus have a cross-sectional area of 0.24 mm.sup.2 and the wire in section 11 a cross-sectional area of 0.16 mm.sup.2 . At room temperature, therefore, the wire in section 10 will have a resistance of ca. 0.8 ohm and at the same temperature, the wire in section 11 may have a resistance of 1.2 ohm. If the heating pad, assembled as shown in FIG. 2, is connected by contact 9 to a voltage source in a vehicle, the wire in the two sections 10 and 11 will be heated and as th
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AB Mekania-Verken
Goldberg E. A.
Walberg Teresa J.
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