US2230440A - Electrical heating means - Google Patents

Description

Feb. 4, 1941.

E. L. 'NIEGI ND ELECTRICAL HEATING mums Filed Sept. 7, 1939 4 Sheets-Sheet 1 n v E. Fig. 1. Q E

ATTORNEYS Feb. 4, 1941. 5 LJWIEGAND ELECTRICAL HEATING IEANS Filed s t. 'r, 1939 4 Sheets-Sheet 3 41 Edwml;

I NVBNTOR ATToRNE s Patented Feb; 4, 1941 UNITED STATES PATENT OFFICE 19 Claims.

My invention relates to electrical heating means and is particularly adapted for embodiment in heating elements and electrical heating apparatus of the fluid convection or forced fluid convection type, and the principal object 7 of my invention is to provide new and improved electrical heating means of these types.

In the drawings accompanying this specification, and forming a part of this application, I have shown, for purposes of illustration, several forms which my invention may assume. In these drawings:

Figure 1 is a fragmentary front'elevation of a blower heater embodying the invention,

Figure 2 is a side elevation of the blower heater shown in Figure 1, on a smaller scale than Figure 1, certain parts being broken away,

Figure 3 is a fragmentary front elevation, on an enlarged scale, of several of the finned heating elements forming part of the blower heater shown in Figure 1,

Figure 4 is a section taken on the line 4-4 of Figure 3, looking in the direction of the arrows,

Figure 5 is a'section taken on the line 5-5 of Figure 4, looking in the direction of the arrows,

Figure 6 is a perspective view of a fin element which may be used for providing the fins of the finned heating elements,

Figure 7 is a fragmentary front elevation, similar to Figure 3, of another embodiment of a plurality of finned heating elements which may be used in place of the embodiment shown in Figure 3,

Figures 8, 9, 10, 11, and 12 are views similar to Figure 7 showing still other embodiments respectively,

Figure 13 is a front elevation of a fin element of an embodiment different from that shown in Figure 6,

Figure 14 is a perspective view of the fin element shown in Figure 13, and

Figure 15 is a fragmentary front elevation of a plurality of finned heating elements, illustrating still another embodiment.

Referring to Figures 1 and 2, there are here shown a plurality of finned heating elements I mounted in a housing 2, here shown as of, generally rectangular cross-section. In the rear of the housing 2 is mounted, in any suitable way, an electric motor 3 for driving a fan 4. The fan 1 is adapted to draw in air through the open rear end 5 of the housing 2 and blow this air through the heating elements I and out of the front end 6 of the housing. The front end 6 of the housing 2 is here shown as provided with a desired number of louvres I which may be used to regulate the air stream issuing fromthe front end of the housing.

5 In the blower heater shown in Figures 1 and 2 the finned heating elements lcomprise a row of six finned electrical heating elements a1, or, as, 614, as, as, disposed in spaced side-by-s ide relation in a general plane transverse to the stream of air provided by the fan 4. It will of course be understood that the blower heater need not comprise six heating elements but may comprise any other desired number of heating elements. The blower heater illustrated in Figures 1 and 2 is further shown as comprising another row of six heating elements bl, b2, b3, b4, b5, b6, disposed in side-by-side relation in a general plane to the rear of and generally parallel to the plane in which the heating elements (11 through as are disposed. The heatin elements in the row b1 through be are spaced in side-by-side relation similarly to the row' of heating elements an through as, so that the heating elements (11 through as are in general front to back alinement with the heating elements b1 through be respectively, and in general alinement with the air stream provided by the fan I. It will be understood that any desired number of rows of heating elements, each row in a different plane transverse to the air stream, may be utilized On the other hand, only one row, of any desired number of heating elements, in a plane transverse to the air stream may be provided.

Referring now to Figure 3, there are here shown fragments of three of the heating elements, a1, a2, (13, .of the front row of heating elements of the blower heater of Figures 1 and 2, and three of the heatingelements, b1, b2, be, of the row of heating elements immediately to the rear of the heating elements m, as, a:. Each heating element is here shown as comprising a metallic sheath 8 of oblong generally rectangular cross-sectional outline, as shown in Figure 5. It will be evident that the heating elements are so disposed that wide sides of the sheaths of adjacent heating elements face each other, so that the narrow sides of the sheaths are transverse to the air stream.

The sheath 8 is here shown as comprising a sheet metal channel the marginal portions 9 of which are bent over a cover plate H), but the sheath may be of any other suitable form. Disposed within the sheaith 8 is a resistor ll, here shown as comprising a strip or ribbon of resistance material disposed in zig-zag fashion and insulated from the sheath by any suitable insulating material I2 in which the resistor is 5 embedded. It will be understood that the resistor II may be a wire helix instead of a. zigzag ribbon, or it may be of any other suitable form.

The sheath 8 of each heating element is prolo vided with a plurality of fin elements, such as I3, Figure 6, spaced longitudinally of the sheath, and these fin elements are here shown as comprising a collar I4 having integral therewith at one end thereof a flange here shown as comprising a root portion I5 of oblong rectangular form, generally symmetrical with the collar I4, and defining a plane at right angles to the axis of the collar. The flange further comprises end portions I6, extending in a general direction transverse to the general plane of the root portion I5 and in this instance in a direction away from the root portion I5 generally the same as the direction in which the collar I I extends from the root portion I5. In the particular instance illustrated, the end portions IG each make an angle of 45 with the root portion, but I do not limit myself to this particular angle.

The collar H of the fin elements, as most clearly seen in Figures 5 and 6, has a portion of one wide side pressed inwardly to form an inwardly embossed portion I! which substantially fits in the groove formed by the gap between the edges of the bent-over marginal portions 9 of the metallic sheath 8 of the heating element, the embossed portion I1 being in contact with the cover plate I0. Constructing the collar in this fashion is however not essential. In general, the collar I4 of a fin element is made so generally complementary to the cross-sectional outline of the metallic sheath of a heating element that the collars of the fin elements may be telescoped snugly over the metallic sheath 8 as is apparent from Figures 3, 4, and 5. As shown in Figure 4, the unfianged or free end of a collar Id of one of the fin elements is adapted to nest to a certain desired degree in the slightly flaring opening of the flanged end of the adjacent fin element.

Referring again to Figure 3, the fin elements associated with the heating elements of the a row of heating elements have been designated with the reference character I3a, and the fin elements associated with the b row of heating elements have been designated with the referenEe character I3b. Referring now more particularly to the heating element (11 of Figure 3, it will be noted that the fin elements I3a are mounted on the metallic sheath 8 of this element in such a way that the end portions I6 of the fins or flanges extend in a generally downward direction from the respective root portions I5 of the flanges. On the other hand, referring to the heating element as, the fin elements I3a are mounted on the metallic sheath 8 of the heating element a2 so that the end portions I6 of the fins or flanges extend in a generally upward direction from the root portions I5 of these flanges. Referring to the element as, the fin elements I3a are mounted on the metallic sheath 8 of the element as in the same manner as in the case of the element a1 and consequently, in the "a row of heating elements the directions of the end portions I6 alternate from one direction to the other from one element to the next adjacent.

v (5 In the instance of Figure 3 the root portions I5 of the fin elements of adjacent heating elements of the "a row are in staggered relation,

In the b row of heating elements, which row, as stated, is to the rear of the a row, the directions of the end portions I6 of the fins of the fin elements I3b also alternate from element to element, but the alternations of the rear row are out of phase with the alternations of the front row, the end portions I6 of the fins on the heating element In extending upwardly with respect to their root portions I5, with the result that the directions in which the. end portions I6 of the fins extend from their respective root portions I5 not only alternates with reference to heating elements in the same general plane transverse to the direction of the air stream, but also alternates with reference to heating elements which are aligned with the air stream in front to back relation. Furthermore, the fin elements I3b are in staggered relation, front to back, with respect to the fin elements I3a, so that in front elevation, as viewed in Figure 3, the root portions I5 of the fin elements I3b are intermediate the root portions I5 of the fin elements I3a. Considering, first, a set of end portions I6 at a given side of the fin elements I3b of the heating element In, and, second, the set of end portions I8 at the corresponding side of the fin elements I3a of the element a1,

it will be noted that the first set of end portions extends in the general plane of row b in a direction transverse to the direction in which the second set extends in row a. Consequently, such corresponding sets of end portions are in crossed relation, front to back. In like manner other corresponding sets of end portions I6 are in crossed relation, front to back.

In order to secure the relations between the fin elements of the respective heating elements hereinbefore described, the finned heating elements may be mounted in the housing 2 in any suitable way, or the fin elements I3 may be mounted on the sheaths 8 of the heating elements in any suit-- able way. In the embodiment of Figure 1 it will be noted that the lowermost fin element, of the heating element b1 has its root portion I5 resting on a plate I8 mounted in the housing 2. On the other hand, the lowermost fin element of the heating element 0.1 has the tips of its end portions I6 resting on the plate I8. In this instance the end portions I6 of the lowermost fin element of the heating element (11 may be trimmed slightly so as to secure the desired position of the heating element 111 with respect to the heating element In. If desired, the end portions I6 of the lowermost fin element of the heating element a1 may be left untrimmed and be bent outwardly slightly to secure the same result, or any other expedient may be adopted for securing the desired staggered relation between the fin elements. The unfinned lower ends of the heating elements may be disposed in slots or openings (not shown) in the plate I8, these slots or openings serving to space the heating elements a desired distance from each other. As herein used the expression spacing of the heating elements means the distance between the median planes of the body portions or sheaths 8 of adjacent heating elements. The minimum spacing of the heating elements is governed by a desired gap between the ends of adjacent sets of end portions IS. The unfinned upper ends may be similarly disposed in slots or openings in an upper plate I8a. If desired, a flanged collar 20 may be provided on each heating element, the flange 2| of the collar being underneath the plate I8, as may be seen in Figures 1 and 2. These flanged collars 20 may be provided to cooperate with the adiacent endmost fin elements on the respective heating elements to prevent longitudinal movement of the respective elements with respect to the mounting plate II, but such flanged collars are not essential.

Each heating element is in this instance shown as provided with a pair of terminals I! at the lower end thereof, one terminal of each element of the "a row being indicated in Figure 1. The terminals on each element are suitably connected to the respective resistor ll. Current may be led to the terminals I! of the heating elements through an outlet box 22 by means of conductors (not shown).

Before discussing the advantages of the constructions and arrangements hereinbefore described, it may be pointed out that in order to secure a large surface for contacting with 9. current of air, it is desirable that there be a comparatively large number of fin elements per unit length of an electrical heating element and that the fin elements be comparatively thin. For example, the number of fin elements per inch length of the heating element may be as many as four,

or more, and the material of which the fin elements are made may be approximately twentyfive thousandths (.025) of an inch thick. These figures are however given merely by way of iilustration and it will be apparent as the description proceeds that my invention is not limited to particular numbers or dimensions. Particularly with comparatively thin fin elements it is difilcult to maintain a sufilciently rapid fiow of heat by conduction from the sheath 8 of the heating element out to the outermost tip of a fin element. Accordingly, it is not profitable to extend a plane fin outwardly from the sheath of the heating element indefinitely because an unduly extended fin heated only by conduction will have its end portions soon cooled in a steam of air to a point where the absorption of heat from the fin is not suihcient to warrant such extension of the fin. Stated in other words, there is in such case too great a disparity between the temperature of the tip of the fin and the root of the fin, and the difference in temperature between the air stream and the tip of the fin is too small. Furthermore, the capacity of a finned electrical heating elementcannot be increased at will, because at higher temperatures a large share of the heat is radiant heat, and a stream of air cannot be heated efliciently by radiant heat. A danger point is consequently reached where, even if the finned heating element is placed in a blast of air, the element will eventually burn out by reason of the fact that the air cannot carry away the heat as fast as it is generated in the resistor of the heating element. The manner in which I have provided against these difiiculties may be best understood by reference first to one of the simpler embodiments of my invention.

Referring first to Figure 7 a plurality of finned heating elements av, aa, an, is here shown, the fin elements I311 on these heating elements being of the same construction as shown in Figures 5 and 6, but in this instance the fin elements are so mounted on the sheaths I of the heating elements that the root portions II are in alinement and the end portions Ii of the fin elements all extend downwardly from the respective root portions 15 of the fin elements. It is of course evident that if desired one or more rows of heating elements, the same as shown in Figure 7, may be disposed in spaced planes to the rear of the row of heating elements visible in Figure 7, the fin elements of the heating elements being either in alinement with each other, front to back, or in staggered relation.

Considering an end portion l6 of any one of the fin elements lid of the heating element :11, for which purpose one of these'end portions has been designated in, it will be apparent that this end portion, l6x, will intercept radiant heat radiated laterally outwardly from the body of the heating element, that is, more specifically, heat radiated laterally outwardly from the wide face of the collar x. Thus, while heat is fed to the root portion ii of a tin element principally by conduction from the body portion of the heating element heat is fed to the end portion liaaof the fin element principally by radiation from the body portion of the heating element. The heat radiated to the end portion lbs: of course heats that end portion and raises its temperature, thereby reducing the general difference in temperature as between the end portion I60: and the root portion I5m, in other words, the tendency is towards equalization of these temperatures. By optimum selection of the lateral extent of the root portion I 50: measured from a wide side of the sheath 8 to the junction of the root portion with the end portion ISLE, depending upon temperature conditions for one thing, heat may also be fed from the end portion l6: into the root portion I51: at the junction of the root portion with the end portion, thereby tending towards equalization of the temperatures of the parts of the root portion |5x nearest and furthest from the sheath 8. By raising the temperature of the end portion Iliz, heat is readily and efficiently abstracted therefrom by the stream of air passing along that end portion. The same is of course true regarding the more efiicient heating'of the root portion and the consequent more efiicient abstraction of heat therefrom. In general, by constructions and arrangements which will satisfy the desideratum that parts of the fin element are sufficiently heated which would not otherwise be sufiiciently heated, heat is readily and efiiciently abstracted by the air stream from the finned heating element as a whole. Any radiant heat radiated laterally outwardly from the collar a: to the end portion lia: which is not absorbed by the end portions lSsc, may be reflected downwardly to the upper side (as viewed in Figure 7) of that end portion l6 which is immediately below the end portion l6x, where it may be absorbed, and then dissipated by the air stream. It is of course obvious that each of the fin elements l3a functions in the same manner as hereinbefore described.

My invention accordingly provides a heating element which may be safely operated at a given electrical input, whereas the same element would burn out if operated at the same input without my invention. On the other hand, heating elements of much greater capacity than hitherto are made feasible by reason of the rapid dissipation the end portions l6 of the fin elements also intercept radiant heat which would otherwise be radiated from the body portion of one heating element to the body portion of an adjacent heating element. Accordingly, it is possible not only to increase the individual capacity of a given heating element but also, if desired, to decrease the spacing of the heating elements of a row of heating elements, thereby increasing the total (a1 through as) of heating elements of Figure 3,

but in Figure 8 it may be considered that, if desired, there is a row of finned heating elements, constructed and arranged the same as the row of finned heating elements visible in Figure 8, but behind and in alinement with that row, front to back. On the other hand, a row of finned heating elements constructed and arranged the same as the row shown in Figure 8 may be disposed to the rear of the row shown in Figure 8 and staggered front to back with respect to each other. In this instance while the fin elements would be staggered, front to back, with respect to each other as in Figure 3, corresponding sets of end portions I6 would not cross as in the instance of Figure 3.

Considering the right hand set of end portions iii of the fin elements I3a of the heating element am and the adjacent left hand set of end portions I5 of the fin elements l3a of the heating element an, it will be noted that these adjacent sets extend in the same general direction in the general plane defined by the heating elements. The result is that the outer faces of one set of end portions I6 are directed toward the outer faces of the adjacent set of end portions I6. Accordingly, heat that may be radiated by or reflected from the outer faces of one set, through gaps between the sets, such as a gap 23, is intercepted by the other set.

In the embodiment shown in Figure 9 there is a row of heating elements .am, (114, (115, each heating element being provided with fin elements I3a. Behind the row of heating elements an, 1114, is another row of heating elements bis, bu, b15,

'each heating element being provided with fin elements I317. The fin elements I3a and I3b are similar to the fin elements I3 of Figures 5 and 6 but have root portions I5I of less lateral extent than that of the root portions I5, and end portions I6I which are longer than the end portions I6. The arrangement of the heating elements of Figure 9 is generally similar to the arrangement shown in Figure 3, but in Figure 9 the root portions I5I of the fin elements I3a are in side-to-side alinement, whereas in Figure 3 the root portions I5 of the fin elements I3a are in staggered relation side-to-side. Also, in Figure 9 the root portions I5I of the fin elements I31) of the heating element In; are in front to back alinement with the root portions I5I of the fin elements I'3a,,of the heating element an; the same applies with' respect to the pairs of heating elements 1114, an and his, (115- It will be noted that a given set of end portions SI of the fin elements I3a is in crossed relation with respect to the corresponding set of end portions ISI of the fin elements I3b, as is the case in Figure 3, but due to the greater length of the end portions IGI, a given end portion IGI of a fin element I3a is in front to back crossed relation with two end portions I6I of two fin elements I3b, instead of only one, as in Figure 3. In general, constructing and arranging the fin elements so that the end portions of the fin elements are in crossed relation gives a desirable amount of turbulence to the air stream, better effecting abstraction of heat from the fin elements by the air stream.

In the embodiment shown in Figure 10' there is a row of finned heating elements are, an, an, each heating element being provided with fin elements I3a, similar to the fin element I3 shown in Figures 5 and 6, but of different proportions,

the root portions I52 being of less lateral extent than the root portions I5, but the end portions I62 being of substantially the same length as the end portions I6. It will be noted that the spacing of the heating elements an, an, an is the same as of the heating elements in Figures 3 through 9, but that the free space between the end portions I62 of the fin elements of one heating element and the adjacent end portions I62 of an adjacent heating element is greater. Under certain circumstances, depending for example on the amount of heat to be dissipated, or the velocity of the air stream, or other factors, it may be desirable and satisfactory to utilize the less extensive fin elements shown'in Figure 10. It will be obvious that in principle the mode of operation of the less extensive fin elements, such as shown in Figure 10, is the same as already described, particularly in connection with Figure 7. Furthermore, under such circumstances it may be desirable to utilize heating elements with the less extensive fin elements shown in Figure 10, but instead of retaining the wider spacing of the heating elements there shown, the ,heating elements may be brought closer together, so that adjacent end portions of the fin elements of .adjacent heating elements are closely spaced as in Figures 3 through 9. Thereby a greater number of heating elements may be disposed in the same space and, for a given capacity of a single'heating element, the total amount of heat dissipated may, in this way also, be further increased. This is made possible not only by reason of the fact that heat is more efliciently and rapidly abstracted by the air stream from an individual heating element but because inter-radiation of heat from an individual heating element to an adjacent heating element is substantially prevented by reason of the intercepting end portions of the fin elements.

Figure 11 shows an embodiment in which a plurality of heating elements am, (120, am is disposed in side-by-side relation, each heating element being provided with fin elements I3a which are similar to the fin element I3 of Figure 6, but in this instance have their end portions I63 bent so as to extend at right angles to their root portions I53, instead of at 45, as in the case of Figure 6. The end portions I63 are here shown as of substantially the same length as the end portions I6 of the fin elements shown in Figures 3, 7, and 8, for example, but the root portions I53 have greater lateral extent than have the root portions of the fin elements of Figures 3, 7, and 8. However, by reason of the fact that the end portions I63 extend at right angles to the root portions I53 the spacing of the heating elements am, (120, (121 may be, and in Figure 11 is shown, less than the spacing of the heating elements of the embodiments of Figures 3, 7, and 8.

Figure 12 shows an embodiment, similar to Figure 11, in which a plurality of heating ele ments (122, am, (124 is disposed in side-by-side relation, each heating element being provided with fin elements I3a which are similar to the fin elements I3a of Figure 11 but in this instance, while the end portions I are of substantially the same length as the end portions I63, the root portions I34 have less lateral extent than have the root portions I33. Consequently, the spacing of the heating elements an, G23, 024 may be, and in Figure 12 is shown, less than the spacing of the heating elements an. 020, (121 01' Figure 11.

In embodiments in which the end portions of the fin elements extend at right angles to the root portions, as in Figures 11 and 12, it is desirable that there be a space, such as 24, left between the end of each end portion (I63 or I64) a fin element and the surface of the adjacent fin element. Such an equivalent space is of course necessarily present in the other embodiments hereinbefore described.

In Figures 13 and 14 is shown an embodiment of a fin element 25 comprising a collar 26, similar to the collar ll of the fin element I3 of Figures and 6, and having also a flange comprising a root portion 21 and end portions 23. The root portion 21 is here shown as similar to the root portion I 5 but the end portions 28, while they each make an angle of 45 with the root portion 21, extend in a direction away from the root portion '21 generally opposite from the direction in which the collar 26 extends from the root portion 21. A plurality of fin elements, such as shown in Figure 14, may be used in place of fin elements such as shown in Figure 6, to build up finned heating elements similar to those shown in Figures 1 through 10, wherever it may be found desirable. It may also be found desirable under some conditions to utilize a finned heating element provided with fin elements such as shown in Figure 6 and to utilize adjacent thereto a finned heating element provided with fin elements such as shown in Figure 14.

In the embodiment shown in Figure there is shown a row of heating elements (125, an, an, each heating element being provided with fin elements 29. Each fin element 29 has a collar 30 similar to the collar I I of the fin element shown in Figure 6, and a flange comprising a root portion 3I similar to the root portion I5, and end portions 32. One of the two end portions 32 of a given fin element 29 extends in a general direction away from the associated root portion the same as the direction in which the respective collar 36 extends away from the root portion, while the other end portion 32 extends in a general direction away from the root portion opposite from the direction in which the collar extends away from the root portion. By comparison with the type of construction and arrangement shown in Figure 8 it will be apparent that the same type 01' construction and arrangement may be arrived at by the use of fin elements such as shown in Figure 15. It will be noted that in arriving at the construction and arrangement of Figure 8, utilizing fin elements such as shown in Figure 6, the fin elements must be telescopegi over the heating element sheath 8, collar first in the case of heating element am, for example (assuming that the terminals I6 of the heating element are at the lower end as viewed in Figure 8), and flange first in the case of the adjacent heating element, an, for example. On the other hand, in the construction and arrangement of Figure 15 the fin elements may be telescoped over the heating element sheaths 6 either all collar first or all flange first as desired.

It also will be apparent that finned heating elements such as shown in Figure 15 may be .5 utilized in constructions and arrangements such as shown in Figures 3 and 9, so asto secure the crossed relation of the end portions of the fin elements, front to back. To secure such an arrangement with finned heating elements of the type shown in Figure 15 all that is necessary is to provide another row of such finned heating elements to the rear of the row shown, the heating elements in the rear row being simply turned 180 about their longitudinal axes, with respect to the front row.

It will be apparent that the construction shown in Figure 15, as well as in the constructions heretofore described, the finned heating elements may be so constructed and arranged that the root portions of the fin elements of a given heating element are staggered with respect to the root portions of the fin elements of a laterally adjacent heating element, or, if there is a heating element in front to back alinement with a given heating element, the root portions of the fin elements or these heating elements may be staggered, or both these conditions may obtain.

Whereas in' the type or construction shown in Figures 11 and 12, the length of the end portions I63 or I64 is limited by the length of the respective collars, that is by the longitudinal spacing of the fin elements, the length of the end portions of the fin elements shown in Figures 3, 7, 8, 10, and 15 is not so limited but may be increased to a desired extent, as it has been increased, for example, in the construction shown in Figure 9.

As examples of good proportioning of the parts, the following may be given. Assuming that in a construction such as in Figure 7 the pitch of the fin elements I3a per inch length of the heating element 3 is four and that the transverse dimension 01 a collar I4 is approximately of an inch, a suitable length for an end portion I6 is approximately 15 of an inch, or more, while the total width of the root portion I5, measured from its junction with one end portion I6 to its junction with the other end portion I6, is approximately 3". The heating elements a1, as may then be spaced a minimum distance, of approximately 1 /2 inches, but may be spaced a greater distance, as already explained. Referring to Figure l1 and again assuming that the pitch of the fin elements I3a per inch length of the heating element 8 is four and that a collar is of an inch across, a suitable maximum length for an end portion I63 is approximately of an inch, while the root portion I53, measured from its junction with one end portion I63 to its junction with the other end portion I63, is approximately 11 inches. The heating elements am, use may then be spaced a minimum distance of approximately 1% inches but may, of course, be spaced a greater distance. The foregoing dimennons are given merely by way of example and it will be apparent that these dimensions may be varied as has been explained in connectionwith comparisons hereinbefore made between, on the one hand, the fin elements of Figures 7 and 11 and, on the other hand, the other illustrated embodiments.

From the foregoing it will be apparent to those skilled in the art that each of the illustrated embodiments of my invention provides a new and thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of. my invention, or sacrificing all of the advantages thereof, and that accordingly, the disclosure herein is illustrative only, and my invention is not limited thereto.

I claim:

1. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including parts spaced longitudinally of said body portion, at said body portion, and extendingitransversely with respect to said body portion, adjacent free end portions of said fin means being spaced from each other and from adjacent said parts and so constructed and arranged as to intercept heat radiated laterally from said body portion.

2. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including parts spaced longitudinally of said body portion, at said body portion, and extending transversely with respect to said body portion, adjacent free end portions of said fin means being spaced from each other and from adjacent said parts a distance less than the spacing of said parts.

3. Heating apparatus, comprising: at least two electric heating elements, each having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely of said body portions respectively; said heating elements being disposed in side-by-side relation in a general plane; and adjacent fin means, of adjacent heating elements, each having a set of end portions extending transversely of the respective said fin parts, one of said sets of end portions extending in a direction generally transverse to the general direction of the other of said set of end portions.

4. Heating apparatus, comprising: at least two electric heating elements for use in a stream of fluid, each element having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely of said body portions respectively; said heating elements being disposed in general alinement with the fiuid stream in respective general planes transverse to the fiuid stream; and the fin means, of alined heating elements, each having a corresponding set of end portions extending transversely of the respective said fin parts, one of said sets of end portions extending in its respective said general plane in a direction generally transverse to the general direction of the other of said set of end portions in its respective said general plane.

5. Heating apparatus, comprising: at least two electric heating elements for use in a stream of fluid, each element having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated irom said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely 01 said body portions respectively; said heating elements being disposed in general alinement with the fiuid stream and so disposed that said respective fin parts are in staggered relation; and the fin means, of alined heating elements, each having a corresponding set of, end portions extending transversely of the respective said fin parts.

6. Heating apparatus, comprising: at least two electric heating elements for use in a stream 0! fiuid, each element having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely of said body portions respectively; said heating elements being disposed in general alinement with the fiuid stream in respective general planes transverse to the fluid stream and so disposed that said respective fin parts are in staggered relation; and the fin means, of alined heating elements, each having a corresponding set of end portions extending transversely of the respective said fin parts, one of said sets of end portions extending in its respective said general plane in a direction generally transverse to the general direction of the other of said set of end portions in its respective said general plane.

'7. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including a plurality of fins extending transversely with respect to said body portion and spaced longitudinally of said body portion solely by collars telescoped over said sheath, said collars being integral with said fins respectively, and said fins being so bent as to intercept heat radiated laterally'from said collars.

8. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including parts spaced longitudinally of said body portion, at said body portion, and extending transversely with respect to said body portion to free end portions to provide free spaces extending laterally outwardly between said parts from said body portion to said free end portions respectively, adjacent free end portions being spaced from each other and so constructed and arranged as to intercept heat radiated laterally outwardly in said spaces from said body portion.

9. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including parts spaced longitudinally of saidbody portion, at said body portion, and extending transversely with respect to said body portion to free end portions at opposite sides of said body portion to provide free spaces extending laterally outwardly between said parts from opposite sidesof said body portion to said free end portions respectively, adjacent free end portions being spaced from each other and so constructed and arranged as to intercept heat radiated laterally outwardly in said spaces from the respective side of said body portion.

10. An electrical heating element, comprisingr an elongated body portion, and fin means for dissipating heat from said body portion; said portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including sheet metal parts spaced longitudinally of said body portion, at said body portion, and extending transversely with respect to said body portion to free end portions at opposite sides of said body portion to provide free spaces extending laterally outwardly between said parts from opposite sides of said body portion to said end portions respective, adjacent free end portions being so bent relative to the respective said parts as to intercept heat radiated laterally outwardly in said spaces from the respective side or said body portion.

11. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including sheet metal parts spaced longitudinally of said body portion, at said body portion, and extending transversely with respect to said body portion to free end portions to provide free spaces extending laterally outwardly between said parts from said body portion to said end portions respectively, adjacent free end portions being so bent relative to the respective said parts as to substantially close off respective said spaces, to intercept heat radiated from said body portion, while leaving a space between a given free end portion and that one of said parts toward which said given end portion is bent.

12. Heating apparatus, comprising: at least two electric heating elements each having an elongated body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, said heating elements being disposed in side-by-side spaced relation in a general plane; and metallic means constructed and arranged to receive heat only from at least one of said electric heating elements, said means heing interposed between said heating elements and constructed and arranged to intercept heat radiated from one of said body portions toward the adjacent body portion.

13. Heating apparatus, comprising: at least two electric heating elements each having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath; and each said fin means including parts spaced longitudinally of the respective body portion and extendin transversely of the respective body portion; each of said heating elements constituting a separate finned heating element, and said heating elements being disposed in selected side-by-side relation in a general plane; and said fin means being so constructed and arranged as to intercept heat radiated from one of said body portions outwardly from said body portion between said parts.

14. Heating apparatus, comprising: at least two electric heating elements, each having an elongated body portion and fin means for dissi pating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely of said body portions respectively; each of said heating elements constituting a separate finned heating element, said heating elements being disposed in selected side-by-side relation in a general plane; and adjacent fin means of adjacent heating elements having end portions extending transversely of said fin parts.

15. Heating apparatus, comprising: at least two electric heating elements, each having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, and said fin means including fin parts spaced longitudinally of said body portions respectively and extending transversely of said body portions respectively; each of said heating elements constituting a separate finned heating element, said heatin elements being disposed in selected sideby-side relation in a general plane; and adjacent fin means, of adjacent heating elements, each having a set of end portions extending transversely oi the respective said fin parts, said sets of end portions extending toward each other.

16. An electrical heating element, comprising: an elongated body portion, and fin means for dissipating heat from said body portion; said body portion including a metallic sheath, a resistor disposed in and insulated from said sheath; said fin means including a plurality of sheet metal fins extending transversely with respect to said body portion and spaced longitudinally of said body portion by collars telescoped over said sheath, said collars being integral with said fins respectively, and said fins having free end por tions so bent as to intercept heat radiated laterally Irom said collars, adjacent bent end portions having opposed collateral spaced surfaces.

17. Heating apparatus, comprising: a housing providin a passage through which a stream of fluid is adapted to be directed; at least two electric heating elements, each having an elongated body portion including a metallic sheath and a resistor disposed in and insulated from said sheath, said heating elements being disposed in side-by-side spaced relation in a general plane transverse to said passage; and metallic means constructed and arranged to receive heat only from at least one of said electrical heating elements, said means being interposed between said heating elements and constructed and arranged to intercept heat radiated normally outwardly from one of said body portions toward the adjacent body portion.

18. Heating apparatus, comprising: a housing providing a passage through which a stream of fiuid is adapted to be directed; at least two electric heatin elements, each having an elongated body port-ion including a metallic sheath and a resistor disposed in and insulated from said sheath, said heating elements being disposed in side-by-side spaced relation in a general plane transverse to said passage; and at least one sheet metal part interposed between said heating elements and disposed edgewise with respect to the stream of air so that the stream is adapted to abstract heat from opposite surfaces of said part, said part being constructed and arranged to intercept heat radiated normally outwardly from one oi. said body portions toward the adjacent body portion.

19. Heating apparatus, comprising: a housing providing a passage through which a stream of fluid is adapted to be directed; at least two electric heating elements, each having an elongated body portion and fin means for dissipating heat from said body portion, each said body portion including a metallic sheath and a resistor disposed in and insulated from said sheath; and each said fin means including parts spaced longitudinaliy or the respective body portion and extending transversely of the respective body portion; each of said heating elements constituting a separate finned heating element; said heating elements being disposed in selected side-by-side portions outwardly from said body portion be- 10 tween said parts.

EDWIN L. WIEGAND.

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