US1927035A - Electrical heating device - Google Patents

Description

p 9, w. w. HICKS 1,927,035

ELECTRICAL HEATING DEVICE Filed July 2, 1928 F I E '.l

FIE| E [DUE] EIUEIIEIDEIDEEIE] III mmcmclcmjnm El DECIDE] El DEBQEHMEEIUEI El [JEIIUEIDEHDEIEI El [118535511355 I] DEIIDEIEIEJEUU Jr" 'Il= E A TTOR E YS Paten ted Sept. 19, 1933 ELECTRICAL HEATING DEVICE William Wesley Hicks, San Francisco, Calif., assignor to Wesix National Company, San Francisco, Calif., a corporation of Delaware Application July 2, 1928. Serial No. 289,709

2 Claims. (01. 219-46) This invention relates generally to devices for converting electrical energy into heat.

It is an object of this invention to devise a novel unit or electrical heating element which can be universally applied to supply heat either by conduction or convection.

It is a further object of this invention to devise an electrical heating unit which is inher- .ently flexible and which can be looped upon it self or which can be bent to various forms without permanent deformation.

It is a further object of this invention to devise a heating unit having a relatively small heat lag and a relatively eflicient heat transmitting surface. 3

Further objects of the invention -will appear from the following description in which I have set forth the preferred embodiment of my invention. It is to be understood that the appended claims are to be accorded a range of equivalents consistent with the state of the prior art.

Referring-to the drawing: w Figure 1 is a side elevational view of a device incorporating my invention.

Fig. 2 is an enlarged cross sectional detail of a portion of the unit shown in Fig. 1.

. Fig. 3 is a detail perspective view showing the metal strip employed for formingmy flexible metalsheath.

Fig. 4 is a front'elevational view of an electrical air heater incorporating a unitsuch as shown in Fig..-1."

Fig. 5'is a cross sectionalv view taken along the line 5-5 of Fig. 4.

Fig. 6 is a front elevational view showing an-' other manner in which device of Fig. 1 can be looped about supporting means.

Fig.7 is a detail of a modified form of the unit in which a singlesheath encloses a pair of resist- I -ance conductors.

' fi' elo'ngated 'metal tube. In adapting such-heating units to various conditions of operation or to different heating appliances with which they are employed, they can be bent from the normal shape in which they are manufactured, but such bending effects a permanent deformation. In

other words a small amount'of bending of the metal sheath or tube exceeds the elastic limit of the metal with the result that the bend is permanent. It is apparent that bending of an ele- -ment of this kind must not only be done carefully beads 12 of insulating material.

so as not to injure the element, but "in most cases the elements cannot again be straightened or bent to a different shape to suit other conditions. Furthermore this bending cannot be accomplished quickly and readily as with the invention herein disclosed. j

' In my invention I enclose an insulated resist.- ance conductor in a metal sheath but this sheath is constructed in such a manner as to be inherently flexible'to such a degree that the elements can be looped upon itself without permanent deformation.

Referring to the drawing for a detailed description of the preferred embodiments of my invention, in Figs. 1 and 2 I have shown an electrical heating unit comprising a flexible resistance conductor 11 which is preferably convoluted so as to provide suflicient resistance and a high degree of flexibility. Conductor 11 is provided with flexible insulation, which in this case is preferably formed by a plurality of contiguous tubes or and the bead or tubes are enclosed within an inherently flexible metal case 13. a

As an example of an inherently flexible sheath, I have shown a construction utilizing a strip 14 made of metal having relatively high resilience. This strip is formed as shown in Fig. 3 so as to The conductor provide oppositely extending edges 16 and 1'7 and is wound in the form of a helicoid or a spiral in such a manner that the projecting edges 16 ,and' 17 are caused to interlock between adjacent looping such a sheath upon itself the e astic limit a of the metal is not exceeded and therefore the 'sheath does not take a permanent deformation.

Another advantage of a sheath of this kind is that it is of comparatively light weight compared to a solid tube of equal lateral strength,v and therefore my unit has small heat lag.

The insulating tubes 12 are preferably of such a length, and have suflicient clearance between the sheath 13 that they will not be cramped and broken when the sheath is flexed to its radius. For connection with the ends of conductor 11, I have shown suitable connection blocks 18 mounted upon the ends of the flexible sheath 13. As a means for securing these blocks to the sheath, I have shown each block provided with a portion 19 adapted to project within the cooperating end of sheath 13. A suitable clamp face and increases the surface of contact between serves to efiectively clamp the sheath to portion 19. A suitable connection terminal 22 is provided upon block 18, and a lead from conductor 11 extends to terminal 22 thru the opening 23.

In Figs. 4 and 5 I have shown one particular use for the units shown in Figs. 1 and 2. In this case the unit forms an electrical heating element for an air heater. This heater has been shown conventionally as comprising an. outer housing 26 having an open front which is covered by a suitable grille or front plate 27. Positioned within the housing 26 there is a shell 28 which accommodates a supporting plate 29. A flexible unit such as that described above and which has been indicated generally at 31, is looped about the support 29 in any convenient way. When in use convection currents can flow thru grille 29 into and out of the open front shell 28, and likewise into the lower and out of the upper portion of housing 26 between the shell 23 and the housing.

It is to be noted that because of -the character of my flexible metallic sheath, the outer surface of this sheath is grooved and thus provides an effective augmented heat transmitting surface. Such a grooved surface is of particular advantage when my unit is employed for heating fluids such as air, as it materially increases the radiating surthe sheath and surrounding fluid medium.

In Fig. 6 another adaptation of my heating unit is shown, in which this unit 31 is looped about and supported by a plurality of insulating knobs 32. While in case of the uses illustrated in Figs. 4, 5 and 6, the unit effects heating principally by radiation and convection, it is apparent that it can also be employed for heating by direct conduction, as-for example the unit can be wrapped about or otherwise placed in heat conducting relationship with a body to be heated.

1,927,036 21 surrounding the end portion of sheath 13,

In Fig. '7 I have shown a flexible sheath 33 similar in construction to that shown in Figs. 1 and 2, but adaptedto enclose a plurality of resistance conductors 11. In this case the sheath 33 is fiattened and encloses two conductors 11-and their insulating tubes in side by side relationship. The properties of a unit constructed in this manner are similar to the properties of the single conductor unit previously described.

I claim:

1. In an electrical heating device, a flexible.

resistance conductor, a plurality of insulating tubes strung upon the conductor, a second conprising a spirally wound strip 01 metal having interlocking turns, whereby said sheath is capable oi. assuming various curved. contours without permanent deformation, the insulating material of which said tubes are composed being relatively compact, and having relatively small heat lag, thereby affording eflicient'heat transfer from said conductor to said flexible sheath in any position which the sheath may assume, each 01 said tubes being of a length at least equal to but less than twice the width 01' said strip.

WILLIAM WESLEY HICKS.

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