US2612585A - Radiant heating pad for the feet and lower limbs - Google Patents

Description

B. P. M CANN Sept. 30, 1952 RADIANT HEATING PAD FOR THE FEET AND LOWER LIMBS 2 SHEETSSHEET 1 Filed May 1, 1950 BERT a MC CANN Zmnentor (Ittornegs Patented Sept. 30, 1952 RADIANT HEATING PAD FOR THE FEET AND LOWER 'LIMBS Bert McGann, Seattle, Wash. v

Application May 1, 1950, Serial No. 159,181

4 Claims. (01. 219-19) 1 This present invention consists of a pad of a sizeconvenient for resting the feet on or standing upon and which is so arranged that it is an effective radiant heating means for the feet and lower legs. The invention makes use of an insulated electrical resistance wire element which is of such resistance and length that it can never attain, from normal electric outlets, a temperature that will be uncomfortable to rest the feet on. Means are further provided for directing the greater amount of the heat generated upwardly in the form of radiant energy so that the feet canbe maintained at a comfortable temperature and the radiant transmission from the surface of the pad will be sufiicient to keep the calves of the legs and knees warm at the same time.

In the past, the normal means for heating dwellings, ofiices, factories, and the like, was by heating the ambient air and to circulate this either by conversion from radiators or by induced draft, such as is normally considered forced air circulation. Such heating is generally accepted but there are so many, instances in which it does not provide warmth for the feet of those who are forced by their vocations to sit or stand at wherein steam or hot water pipes are laid in the fioors of factories, office buildings and homes, provide a very fine solution of this problem. However, they can only be available to a relatively small proportion of the people, and it is to provide this type of heat to those. persons who work or live in areas where such heating cannot be made available that I have developed this present foot heatingpad.

This invention provides an individual heating pad of firm, durable materialwhich can be walked on or stood on} or upon'which the feet can be rested and which, while intended to cover only a relatively small area, will provide a; high degree, of comfort and improved good health to a'large mass of working people.

For instance, the man'operating a machine tool, which nor-1 mally is on a concrete floor, can have on top of the concrete floor a pad just sufficiently large to take care of his essential movement, and this pad can be heated very economically and the heat given out by .it will counteract the cold floors, warm his feet, and the radiant energy given oiT from the:.upper surface of the pad'will warm the lower legs so the person will be comfortable and thus able to achieve his highest possible work output. There are many other persons such as those who stand watch in commercial establishments as officers of the law, or on sea-going vessels, who thus, for the first time, have available to them, a source of real foot comfort. I

The principal object of this invention is to provide a heating pad that will provide a warm fioor' area for a person confined to a limited area.

' A further object of this invention is to provide an electric heating pad which may be used outof-doors or in manufacturing establishments and the like, where the same must be capable of taking unusual use without damage to itself or endangering the person using the pad.

-A further object of this invention is to provide an electric heatin pad making use of low temperature heating wire-to theend that expensive thermostatic controls, and the like, with their attendant servicing difficulties, will be eliminated.

A further object of this invention is to provide an electric heating padin which the entire surface of thepad will form a transmitting surface for radiant energy at low temperature levels so they will give real warmth to theuser yet will never be hot enough to be uncomfortable when the feet are kept in close engagement therewith, as by standing thereon for long periods. V

A furtherobject of this invention is to provide a low temperature electric heating pad that can be economically constructed and which will have a long, trouble-free useful life.

Further objects, advantages and capabilities will be apparent from the description and disclosure in the drawings, or may be comprehended or are. inherent in the device.

In the drawings:

Figure 1 is a perspective view showing how this heating pad may be used by a desk worker;

Figure 2 is a perspective view, partly broken away and shown in section, and with a portion ofthe heating wire raised from its retaining groove to more'fully illustrate thereof;

7 Figure 3 is an enlarged perspective viewtaken in the same sense as Figure 2 and showing the channels for the electric heating elements and the manner in which the terminal connector is imbedded in the heating pad so that no unex-' invention and showing the form that has been found bestadaptable for outdoor use in that the pad will not accumulate water on its surface;

the construction struction thereof;

Figure I is a fragmentary vertical sectional view showing an alternate insulating arrangement;

Figure 8 is a fragmentary vertical sectional. view showing an alternate use of reflectwemsu lation material.

Referring more particularly to the-disclosurein the drawings, the numerals l and: H designate respectively the upper and lower layers which form the heating pad l2 of this invention. These two layers may be made of any dense noncond'uctivematerial that may be madein". sheet form or molded; The basic requirement. isthat the.

sheet be relatively stiff so there-will be no tend.- ency for the edges to-curl, yetthey should preferably be'slightly flexible when joined together so that they will conform to the fioor'surfaceon which they are used even though the same is not perfectly level and smooth. It is further necessarythat' this materialbe of sufhcient density' so that it can either be water-proofed' or preferably; will be-inherently water-proof. The materials'that have'been found mostsuitable are the tempered hard wall-boards.- l The layers may, however; be'molded-of'quite a wide range ofmaterials such asplastic; rubber, or the synthetic rubbers. The laminated materials which combine rubber and fabric; plastic and fabric, or flexible sheet stoclgsuch as paper and the like, are also suitable, It is. desirablethat the material from which the layers are madehave some dielectric properties. and; that they be resistant to the entrance of moisture.

Disposed betweenthe top and bottom layers is the insulated low temperature heating cable l4. Cables of'this order have been used for heating under special conditions for some time. They wereoriginally.developed'for use in heating hotbed'sand' greenhousesand have found some use in. the, radiant heating, particularly of small homes where they are quite often tacked to the lath. and then covered withplaster. Such cables are. designed for thetype of electric current available. and. are so arranged, duejto the wire gauge and to their length, that the resistance is such that. the temperature of the cable can neverrise aboverthe d'esignedmaximum, As the cable deteriorates after. years of use, t he maximum temperature may not be achieved but there is no danger of it ever going above the designed maximum. This is a very important characteristic of this. type of. heating cable in that it permits the use of' aneconomical heat source which is not dependent upon the used thermostatic control. However, it' is conceivablev that the smaller type of. screw-adjusted thermostat might be used in an installation of this order, in the interest of.

over-all economy of construction and in the interest of, not introducing into the unit an electrical device. that might needservice or replacement ithas been. found. preferable to carefully design the cable. to-keep it below the maximum allowable temperature.

fromwhichthe top and bottom layers are made andtlie thickness-ofthe same, together withtlie The exact cable design. will be dependent, to a degree; uponthe materials should exceed 85 Fahrenheit, and for use, as under a desk, where the users feet may rest at the same point for a considerable period this temperature should not exceed Fahrenheit Cable l4 should normally be placed in grooves as I Bcut into, preferably, thebottom layer This leaves the top layer of uniform strength throughout its entirety and adds materially to its longer life, and further tends to more thoroughly equal- 1Z6, the'distribution of heat throughout the top layer. The usual form of groove [6 is indicated 7 n dotted lines in Figure 2, it being necessary to start at the cable connector and anchor 18 and make'a continuous panel coil which then must have its outermost end connec e co tor 8. t d to the cable the prime need of -a foot-warming pad of this. order is for use formany kinds of floors it may-not only be unheated, but actually may be,

in contact with the ground, as for instance, a

concrete: ground floor, and thus have its heat conducted away from it so-that it is mu than the ambient air. Under such con i ti s i t naturally follows; it is believed, that steps should betaken to prevent the dissipation of the heat downwardly and endeavor to retain the maximumfloor radiation upwardly. To this end it is found desirable to employ one of the .various accepted" forms of insulating material 0 s h D ne ver effective 1118211181? to employ a sheet of reflective insulating material I? between the topand bottom layers. This keeps thethickness of the heat ing' pad to a minimum and does not affect its.

ability toflex slightly The refie otive material normally used-is aluminum. foil andwill readily permit sufhcient'deformation to partially encirclethe lower part of wire I 4* as it r ests ingrooves I6. An improved theoretical use of the foil or sheet aluminum is shown in Figure .8 in which the, foil,

or sheet rests in a r cess in la I o yer H and theto layer is supportedby a grid of. support ribs I; This arrangement. permits the .maximum. reflectiorr from the upper surface of the sheet. An

alternate construction is sho I wn, in Figure '7 in which a fibroussheet is employed, such as 20 between the top and bottom layers. In this con structionit is found best to form insulating fibre sheet Z'dpreferably as partof the bottom layer so that again the top 1a yer may bea she unifoim thickness; In this form: it is define desirable to form grooves within fibre sheet 20- for the accommodation of' the insulated heating wire I4; In this modified form it h as been found most effective. to employ. rivets or through-boltsas' 22 which will be et slightl h s y inwardl OI the surface of the topv andbottom layer e. This makes it possible. to. obtain a good seal at-the igllllgggged 24 soliihat the heating cable: can' be e as'we as the fibro intrusion of moisture. ls-board, from-the Normally it has been found com parativel eas tothbond the. upper and lower layers tog ethei ei or by heat, fllSlOI1,- or by the application of adhesives suitable for the surfaces joined toge her. There. is,- however, no real objection to the employment of throu gh-rivets or flush boltilriegcetslggiyiygg the body of thepad if that appears ecause of the t ethe two layers- 31p of sheets used in In Figure 2 the preferred form of thi heating pad is shown as adapted to the -u f thosepersons who are well shielded from the weather or dampness. However, it has been found. thatmany persons who must work under adverse weather conditions; are actually the ones who are urgently in need of a device of this order, and to serve this field, there has been illustrated in Figures 4 and 5, a modified form of structure, modified only however, in that the pad is pierced with a large number of regularly positioned openings so as to reduce the surface and to prevent the accumulation of water thereon by allowing it to drain off. In other words, a form of screening or open mat is provided which has been found most adaptable for the outside use. The various openings 30 are, of course, so disposed as to be in between the loops of cable [4 so that the structure. basically, is the same as shown in Figure 2. The cross-sectional view of Figure 5 shows generally the structure where the top and bottom layers are fused together, as can be achieved with many of the plastics and certain of the rubber substitutes.

It is readily apparent that a pad of this order will be very simple to use. Normally, the wattage employed is relatively low and the temperature, of course. will vary somewhat with the conditions of use. For inside use it normally will not exceed 100 or 200 watts. and for outside use will rarely exceed 300 watts, due to the fact that the I pads need to cover only 3 or 4 sduare feet. The pad functions in use very similarly to a radiantly heated floor. In other words, the entire upper, or top layer. becomes heated to the maximum allowable temperature. normally 80 Fahrenheit. and the top surface then becomes a heat transmitter. The heat transfer. of course. follows the same laws as any other form of heating and takes fully into acco nt the natural tendency of warm air to rise. This causes a conduction transfer which may amount to as much as of the total heat transmitted and leave for radiant transfer approximately 55% of the total. It will thus be a parent. it is believed. that not only will the soles of the feet be warm. but a ood deal of heat will be assed on to the lower limbs.

It is believed that it will be clearly apparent from the above description and the disclosure in the drawin s that the invent on com rehends a novel construction of a radiant heating pad for the feet and lower limbs.

Having thus disclosed the invention, I claim:

1. A radiant heating pad for the feet and lower limbs, comprising: a top layer and a bottom layer of durable sheet material having dielectric and water resistant properties. said top and bottom layer being fixedly secured together: an insulated, low temperature heating cable coiled between said la ers to produce a tem erature on the u per surface of said top layer within a range of temperatures comfortable to feet, resting on the pad, said cable having a single wire of such small gauge and being of such length that it cannot heat be ond a low designed maximum temperature: said bottom laver being configured to accept said heatin cable to lie in a plane below said top layer: a cable connector positioned between said top laver and bottom layer and both ends of said cable being connected to said connector making a continuous panel coil: and a sheet of heat-reflective. metal foil on the up er surface of said bottom la er and pressed into the configurations in said bottom laver to lie below said heatin cable.

2. A radiant heating pad for the feet and lower limbs. comprising: a top layer and a bottom layer of durable sheet material having dielectric and water resistant properties: an insulated. low tem perature heating cable coiled between said layers and lying in a common plane below the lower surface of said top layer to produce a temperature on the upper surface of said top layer within a range of temperatures comfortable to feet, resting on the pad, said cable having a single wire of such small gauge and being of such length that it cannot heat beyond a low designed maximum temperature; said cable having means for connecting the cable to a source of electricity; insulating material disposed between said layers and below said heating cable only; said bottom layer being configured to accept said heating cable and said insulating material.

3. A radiant heating pad for the feet and lower limbs, comprising: a durable thin heating pad of a size to accommodate the feet of a person; a low temperature heating cable coiled in said heating pad and lying in a common horizontal plane to produce a substantially even temperature on the upper surface of the heating pad within a range of temperatures comfortable to feet; resting on the pad, said cable having a single wire of such small gauge and being of such length that it cannot heat beyond a low designed maximum temperature; said cable having a dielectric coating insulating said cable to prevent conduction of electricity from said cable to the surfaces of .said pad; said cable having means for connecting the cable to a source of electricity; and said pad having a single sheet of reflective insulating material positioned under said cable to reflect heat from said cable upward.

4. A radiant heating pad for the feet and lower limbs, comprising: a durable fiat, thin heating pad of a size to accommodate the feet of a person, said pad having separate upper and lower members with their exterior faces forming the top and bottom surfaces of said pad; a low temperature heating cable coiled in said heating pad below the lower surface of said upper member to produce a substantially even temperature on the upper surface of the heating pad within a range of temperatures comfortable to feet. resting on the pad, said cable having a single wire of such small gauge and being of such length that it cannot heat beyond a low designed maximum temperature; said cable having a dielectric coating insulating said cable to prevent conduction of electricity from said cable to the surfaces of said pad; said cable having means at the juncture of its two ends for connecting the cable to a source of electricity; and a single sheet of heat insulating material disposed between said cable and said lower member.

BERT P. McCANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 12,782 Landry Apr. 21, 1908 1,263,350 Schneider Apr. 16, 1918 1,703,640 Schmidt-Predari Feb. 26, 1929 1,994,759 Dermott Mar. 19, 1935 FOREIGN PATENTS Number Country Date 13,989 Great Britain June 17, 1913 118,300 Great Britain Aug. 19, 1918 251,853 Switzerland Nov. 30, 1947 488,826 Great Britain July 14, 1938 OTHER REFERENCES Modern Plastics, pages 108-109, August 1946.

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