US 1980528 A
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Description (OCR text may contain errors)
Patented Nov. 13, 1934 UNITED STATES PATENT OFFICE ELECTRIC HEATING PAD Application March 22, 1932, Serial No. 0,492
' In Austria March 28, 1931 1 Ciaim.
The electric heating pads for thennic treatment of parts of the human body as heretoiore used are not sufliciently safe against short circuiting by the body or against grounding by penetrating moisture which would prove dangerous to the patient. Nor do these electric heating pads satisfy the requirements as regards mechanical strength to the desirable extent and finally they are open to the objection that they 4 cannot be made to fit exactly any' shape of the part of the body to be heated. The attempts heretofore made to remove these drawbacks did not lead to satisfactory results.
In the electric heating pad Iorming the subject matter of the invention the said drawbacks are fully done away with by tightly enclosing on all sides the resistance wire provided with a heat insulating covering as well as its supply wires in a pliant rubber or rubber like mass The annexed drawing illustrates by way of example an embodiment of the present invention,
Fig. 1 is an elevation partly in section and Fig. 2 a transverse section ot an electric heating pad.
'As the resistance wire a preierably a wire wound around an asbestos coreis used which wire is also provided with a covering plaited thereon, say of asbestos. A suitable number of zig zags of this wire is embedded in the rubber mass b and connected to the supply cable c also covered with a rubber layer. It is essential that the rubber layer covering the cable c is integral with the rubber mass b.
In order to bring the rubber mass as quickly as possible to the desired temperature, it is necessary to heat the resistance wire to a temperature exceeding to a certain extent the desired and permissible temperature of the heating pad. 40 But this higher heating oi' the resistance wire would result in a deleterlous eflect on the rubber mass surrounding the same by reducing the pliancy and elasticity oi' this mass. For this reason the resistance wire is provided. as stated above, with a heat insulating covering, such !or instance as asbestos, which prevents the overheating of the rubber mass.
Preierably the resistance wire is embedded in the rubber mass while the latter is in a plastic condition. By a vulcanizing process extending over the entire rubber mass enclosingthe resistance wire and the supply wires a resistlng and pliant structure of the desired shape is obtained in which the penetration oi' moisture to 5 the electrically conducting parts is prevented.
(Ci. 219-463) l The intimate enclosing of the individual lengths of the resistance wire by the elastic rubber mass prevents any injury to the resistance wire when the shape ot the heating pad is changed. On the contrary the individual lengths of the resistance wire will follow the elastic deiormations of the rubber body without breaking. The high pliancy and elasticity of the heating pad enable it to adapt itself to the shape of any part oi' the human body, shoulder, knee and so on.
A particular advantage of the heating pad according to the invention consists besides in that it may be readily disiniected, since owing to the fact that the. pad is completely closed and has a smooth surface, it may be placed in a disin- !ecting liquid of a comparatively high temperature or even boiled without any detriment.
Instead of a rubber mass any other mass having similar properties as to pliancy, elasticity and resistance to heat as rubber may be used. The resistance wire may also be embedded into the rubber mass or similar mass by pouring or pressing the mass round the wire.
Finally I wish it to be understood that when automatic switches are used these too have to be vulcanized. cast or pressed into the rubber mass or similar mass.
What I claim is:
An electric heating pad comprising a flexible resistance wire provided with an asbestos covering plaited thereon and wound around an asbestos core, and supply wires electrically connected with the said resistance wire and a carrier tor the said resistance wire consisting of rubber the said resistance wire being completely vulcanized into the said carrier and the said supply wires being completely embedded in a sheath o! rubber integral. with the said carrier and extending from the said carrier to a plug contact over a considerable length whereby any contact o! the body to which the pad is applied with the said plug contact is avoided. r