US2265549A - Electrical heating element - Google Patents

Description

Dec. 9, 1941. s w 2,265,549

ELECTRICAL HEATING ELEMENT Filed July 17, 1940 2 SheetsSheet l ATTORNEY.

Dec. 9, 1941. H. N. SHAW 2,265,549

ELECTRICAL HEA'IVING ELEMENT Filed July .17, 1940 2 Sheets-Sheet 2 INVENTOR Patented Dec. 9, 1941 UNITED STATES PATENT OFFICE,

ELECTRICAL HEATING ELEMENT Harold N. saw, Erie, Pa.

Application July 17,1940, Serial No. 345,909

16 Claims.

of a helical element, it is desirable to provide refractory means for suitably spacing said adjacent portions to prevent the same from contacting one another. In my copending application this is accomplished by the use of insulator segments positioned between adjacent portions of the heating element, and held in position by the shape of the insulators, and in the case of a helical heating element these insulators are assembled in helical form and are threaded at intervals between turns of the heating element.

In the use of this type insulator, as well as insulators insertible between adjacent sections of a flat type element embodying a return bend,

it is advantageous to definitely hold the heating element against the insulators, so that even if the element is stretched, while it is being pulled into a duct, as in the case of a long helical element, the insulators will still be held in proper position against certain of the turns.,

In addition, while in a helical element of the type described in my prior application it is practical to employ the helical insulators only at intervals, instead of every turn, nevertheless, there is danger, due to inequalities of manufacture and due to inequal expansion under heat, of certain of the turns, between which there are no insulators contacting one another.

It is therefore an object of the present invention to provide insulator segments of refraotory material for spacing adjacent turns or portions of a heating element, together with other refractory means positionable between said insulator segments at desired locations and having laterally extend-ed portions which embrace the remote edge of an adjacent heating element portion to hold the latter portion against the insulator segments and also, in the case of a helical heating element, to serve as a supplemental spacer between turns where'there is no insulator assembly, whereby all turns of the element are prevented from contacting one another.

A more specific object of the invention, referring to one species of the above concept, is to provide in a fiat type heating element consisting of two or more adjacent and parallel heating element sections connected by one or more return bends, a plurality of spaced insulators between said parallel sections for preventing the same from contacting one another, and other refractory means positioned between some 0! said spaced insulators and extending transversely thereof for holding the adjacent heating element sections against the insulators.

A further specific object 01' the invention, rei'erring to another species of the concept, is to provide in a helical heating element, helical insulators threaded onto said element atintervals 01' approximately every other turn, said insulators being of segmental form and there being certain segments of different shape which have lateral hook extensions to hold the adjacent turn of the heating element against theinsulator and also to serve as a spacer between turns wherethere is no insulator assembly, whereby all turns of the element are prevented from contacting one another.

A further object of the invention is to provide in a helical heating element construction as above described, means for preventing shifting of the helical insulator assembly on the heating element.

Afurther object of the invention is to provide in a heating element means extending longitudinally thereof for preventing longitu-.

dinal elongation.

A further object of the invention is to 'provide insulator assemblies and holding members cooper-able therewith which do not interfere with heat radiation from the element.

A still further object of the invention is to provide segmental insulator and holding members assembled in groups wherein the segments are formed to engage with each other-in such a manner as to permit flexibility while preventing tilting of a segment out 01' position and while preventing breakage of theinsulator assemblies due to expansion under heat or rough handling.

A further object of the invention is to provide a heating element having insulator assemblies thereon together with holding members cooperable with said insulator assemblies, wherein the insulators serve to support the heating element in an elongated duct in spaced relation from the sides of the duct, said heating elements being flexible to permit insertion in curved ducts such as those extending around the sides of a kettle or the like.

With the above and other objects in view, the

invention consists of the improved electrical heating element and all its parts and combinations as set forth in the claims and all equivalents thereof.

In the accompanying drawings illustrating several preferred embodiments of the invention, in which the same reference numerals designate the same parts in all of the views:

Fig. 1 is a top view of a flat type heating element embodying two parallel sections connected by a return bend;

Fig. 2 is an edge view of said element showing it in curved condition; 7 Fig. 3 is a sectional view on an enlarged scale taken on the line 3--3 of Fig. 1;

Fig. 4 is a transverse sectional view taken through one of the oval holding members, also on an enlarged scale;

Fig. 5 is a perspective view on a smaller scale of one of the insulators alone;

Fig. '6 is a front view of a modified form of holding member on an enlarged scale;

Fig. 7 is a fragmentary plan view of a modifled form of heating element wherein the heating lement comprises a small coil, instead of metal, which is channel shaped in cross section,

as in Fig. 1;

Fig. 8 is a sectional view taken on line 88 of Fig. 7 on an enlarged scale;

Fig. 9 is an end view of one of the insulators used in the assembly of Fig. '7;

Fig. 10 is a view of one of the holding members used in the assembly of Fig. 7;

Fig. 11 is a view similar to Fig. 8 showing another modification wherein the heating element comprises a flat strip; v

Fig. 12 is a top view of a helical heating element, part being broken away;

Fig. 13 is an end view of the element of Fig. 12;

Fig. 14 is a sectional view taken on the line l4-l4 of Fig. 12; v

Fig. 15 is a sectional view taken on the lin l5|5 of Fig. 14;

Fig. 16 is an edge view of one of the helical insulator assemblies alone showing the hookshaped holding members assembled thereon;

channel.

sections 32 and 33 from spreading to free the insulators 34, holding members 31 are utilized. The holding members 31 and the insulators 34 are all formed of refractory material. The holding members have laterally extending portions 38 which extend beneath the heating element sections 32 and 33 and then upwardly, as at 39, to hold the heating element sections 32 and 33. In the form of the invention shown in Figs.

1 and 3, it is preferred that these' holding members be in the form of complete links, but said holding members may take the form of the modiflcation 40, illustrated in Fig. 6. The holding members are thickened at the outer edgs, as at 4|, for strength (Fig. 4) and are relatively thin at the inner edge, as at 42, so as to prevent interference with free heat radiation from the element. Both sides of the base of the heating element channels 32 and 33 are free to radiate heat, and both sides of one flange are open to free radiation. Radiation from the other flange is partially obstructed by the insulator separators 34, but with relatively wide channels and low flanges this does not cause the obstructed flange torun appreciably hotter than the base of the In practice, all parts of the heating element channels operate at practically the same temperature.

This element can be operated as a single (low voltage) unit or in banks. Single units may be installed in parallel ducts and connected in series by spot welding the ends. This fiat construction makes possible a rugged but flexible element of thin ribbon with practically all parts of both the heating element and insulators spaced for free heat radiation so that there is a minimum of stored heat.

The assembly of Figs. 1 and 2 is self-locking, because the end insulator butts against the return bend, and the holding link at the end opposite from the return bend is held by bending the ends of the channel laterally, as at 43, and

Fig. 17 is a side view of one of the segments the numeral 30 designates a heating element.

formed from metal. which is U-shaped in cross section, and capable of having electricity passed therethrough to create heat. The length of material 30 embodies a return bend 31' to provide two parallel heating element sections 32 and 33. More than two sections may, of course, be formed by utilizing additional return bends.

Positioned between the parallel sections 32 and 33 are insulator segments 34 which have enlarged upper and lower portions 35 and 3G to overlap the adjacent heating element sections 32 and 33 in the manner shown in Fig. 3. In order to prevent the adjacent heating element spreading the same.

This construction is not as flexible as a helical heating element, but by using relatively small refractory parts and thin metal for the element, there is plenty of flexibility to prevent breakage by rough handling or expansion under heat. The flexibility permits curving, as indicated in Fig. 2, to allow installation in curved ducts. This element may be installed in flat tubes for bayonet type immersion units, may be used for water heating, for heating lead pots, and for other similar purposes. The use of light weight heating elements with this form of the invention makes possible close temperature control and quick heating.

Figs. 7 to 10 inclusive, illustrate amodification wherein in lieu of the heating element 30 formed of stock which is channel shaped in cross section, a small coil 44 is employed. The coil embodies a return bend 45 and adjacent parallel sections are separated by insulators 46 (see Figs. 8 and 9) which correspond to the insulators 34 of the form of the invention of Fig. 1. Between the insulators are holding members or links 41 (see Figs. 8 and 10) which have spaced holes 48 through which the heating element coil extends. In order to prevent undue stretching of the coil 44, holding wires 44' which extend through holes 46 in the insulators and holes 41' in the holding mem bers 41, may be employed. These holding wires 44' have their extreme ends bent or looped, as at 48' at a point to allow sufilcient expansion while preventing undue elongation.

Fig. 11 illustrates a modification and is identical to the structure of Fig. 3, except that flat heating element sections 48 and 50 are employed instead of the channel shaped sections 32 and 33, the insulators and holding members being more compact, as shown in Fig. 11, to conform to the flat heating element. In other respects the element is the same as that illustratedin Figs. 1 and 3.

Referring to the helical type of heating element illustrated in Figs. 12 to 22 inclusive, the heating element proper comprises metal ribbon which is channel shaped in cross section and which is wound in helical form to provide adja: cent sections 52, 53, and 54 which correspond to the adjacent sections 32 and 33 of the form of the invention illustrated in Fig. 1.

Insulator assemblies 55 comprising a plurality of segments 56 of refractory material are assembled in helical form, as shown in Fig. 16, by passing a cotter pin 51 or the like through registering holes 58 in the insulators, The meeting ends of the segmentshave cooperating tongues 59 and grooves 60 (see Fig. 17) which look the insulators together while providing for flexibility.

The insulator assemblies of Fig. 16 which are approximately one turn in length are preferably used only every other turn on the heating element, as shown in Fig. 12. In order to prevent the uninsulated intervening turn from contacting under pressure, and in order to hold the heating element turn against the insulator assembly, one or more holding members SI, of refractory material, are used between certain of the se ments 56. It is preferred to use two of such holding members 6| on each insulator assembly. These holding members 81 correspond to the holding members 31 of the form of the invention of Fig. 1, in that they embody a portion 62 which extends laterally beneath the adjacent heating element section, which portion is then hooked upwardly, as at 83, to space uninsulated turns, such as the turns 53 and 54 apart and to hold one of the turns, such as the turn 54 (Fig. 12)

against the insulator assembly on the other side of the turn. The function of the holding members 6| is therefore a common function with the .holding member 31 of Fig. 1, i. e., to hold the adjacent heating element section against the insulator. I

The holding members 61 may also take the form of Fig. 20 and be provided with an enlarged v end 65 to overlap adjacent heating element seccotter pin 51 may be bent laterally, as at 68 (Fig.

15) to butt against the end of an adjacent insulator assembly. Another method of preventing shifting is to bend one of the ends of the cotter pin outwardly, as at 69, to extend through a hole in the adjacent heating element section, as illustrated in Fig. 21.

The outer or looped end of each cotter pin is through the relatively thick end discs 13, which end discs are of refractory material, and through the alined loops 1|. The extreme ends of the holding wire 12 are looped, as at 14, to prevent withdrawal of the wire 12. The result of. this construction is that the insulator assemblies are held against shifting because of the wire" 12 extending through the loops 1|, and in addition the entire heating element is locked against stretching which might occur while the element is being pulled into an elongated duct. Such stretching, if permitted, might cause some of the turns to separate and cause displacement of insulator assemblies therebetween.

The ends of the heating element 51 have flat terminals 15 welded thereto, as at 16, and said terminals extend through slots in the end refractory discs 13. In addition one end of the bent inwardly of the helix, as indicated at 1i in cotter pin of each endmost insulator assembly is extended through the adjacent end disc 13 and bent over, as at 11 (Figs. 12 and 13).

By having insulator assemblies such as the assembly of Fig. 16 every other turn and by having two holding members 6| on each insulator assembly with the spacing hook 63, every turn of the helical heating element is positively spaced.

, Thus sagging of the element is prevented if it is used in a vertical position. The tongue and groove engagement between the insulator segments and between the segments and the holding members 8| prevents the holding members from pivoting downwardly toward th center of the heating element. The length of the holding wire 12, which extends longitudinally of the element, is suflicient to allow for some expansion, and when the element, is being pulled through a duct, the turns I end of an adjacent insulator assembly can be used alone without the elongated wire 12 to prevent shifting of the insulators, or the method of Fig. 21 may be employed alone. Also the method of Fig. 21 may be employed to hold very short insulator assemblies against shifting and in such an arrangement there could be three or four short insulator assemblies on each turn which are held spaced apart from each other by the cotter pin and hole engagement with the element as in Fig. 21.

Various other forms and modifications maybe provided without departing from the spirit of the invention, and all of such modifications are contemplated as may come within the scope of the claims.

What I claim is:

1. An electrical heating element comprising elongated heating element sections which extend adjacent one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, and holding members formed of refractory material positioned between some of said insulator segments, each holding member. having means engaging with an adjacent heating element section for holding the latter against the insulator segments.

2. An electrical heating element comprising elongated heating element sections which extend adjacent one another, insulator segments formed of refractory material positioned between said.

adjacent one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, and holding members formed of refractory material positioned between some of said insulator segments,

each holding member having means extending transversely across an adjacent heating element section and then at an angle to engage the remote edge of said section for holding the latter against the insulator segments.

4. An electrical heating element comprisingelongated heating element sections which extend adjacent one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, and holding members formed of refractory material positioned between some of said insulator segments, each holding member having means engaging with the adjacent heating element sections on both sides for holding the latter in engagement with the insulator segments.

5. An electrical heating element comprising elongated heating element sections which extend adjacent to one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, said insulator segments having grooves in opposite sides Within which the edges of the heating element sections fit, and holding members formed of refractory material positioned between some of said insulator segments, each holding member being of link form and engaging around the heating element sections on both sides of the insulator segments to hold said two sections in engagement with the grooves of the insulator segments therebetween.

6. An electrical heating element comprising elongated heating element sections which extend adjacent one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, and holding members formed of refractory material positioned between some of said insulator segments, each holding member having means engaging with an adjacent heating element section for holding the latter against the insulator segments, said holding members being of decreasing thickness toward the center thereof to cause a minimum of interference with heat radiation.

'7. An electrical heating element comprising an elongated helix of metal, insulating supports of helical shape threaded at spaced intervals onto the element between the turns thereof, said supports being substantially dumb-bell shaped an adjacent turn of the helix to hold said turn against the insulating supports.

8. An electrical heating element comprising an elongated helix of metal, insulating supports of helical shape threaded onto the element between the turns thereof, said supports being each formed of a plurality of segments having means overlapping the edges of the metal forming the turns to hold the segments in position between turns, there being holding members between some of said segments which have hook-shaped portions engaging the remote edge of an adjacent turn of the helix to hold said turn against said segments,

and means in addition to the heating element connecting said segments and holding members in assembled groups.

9. An electrical heating element comprising an elongated helix of metal, insulating supports of helical shape threaded onto the element between the turns thereof, said supports being each formed of a plurality of segments having means overlapping the edges of the metal forming the turns to hold the segments in position between turns, there being holding members between some of said segments which have hook-shaped portions engaging the remote edge of an adjacent turn of the helix to hold said turn against said segments, and means in addition to the heating elements connecting said segments and holding members in assembled groups, there being a tongue and groove engagement between said segments and holding members topreventrelative tilting.

10. An electrical heating element comprising an elongated helix of metal, insulating supports of helical shape threaded onto the element between the turns thereof, said supports being each formed of a plurality of segments having alined openings, and some of said segments having hook-shaped portions which engage the remote edge of an adjacent turn of the helix to hold ports of helical shape threaded onto the element in cross-section to engage above and below the edges of the 'metal forming the element, and

holding members between some of said sup-' between the turns thereof, said supports being each formed of a plurality of segments having alined openings, and an elongated member extending through the openings of the segments to connect the same, said segments being formedwith means cooperating with the edges of the metal forming the heating element to maintain the insulating supports in position, and means extending longitudinally of and within the element and engaging with said supports for preventing rotatable shifting of the helical insulating supports on the helix of metal.

12. An electrical heating element comprising an elongated helix of metal, a plurality of insulating supports of helical shape threaded onto the element between the turns thereof, said supports being each formed of a plurality of segments having alined openings, an elongated member extending through the openings of the segments to connect the same, said segments being formed with means cooperating with the edges of the metal forming the heating element to maintain the insulating supports in position, one end of the elongated member of each helical insulating support having a loop, and the loops of the plurality of helical insulating supports being alined within the heating element, and an elongated member extending through said alined loops and having stops at the ends thereof for limiting longitudinal elongation of the heating element and for preventing shifting of the insulating supports relative to each other.

" 13. An electrical heating element comprising an elongated helix of metal. and insulating supports of helical shape threaded onto the element between the turns thereof, said supports being 'each formed of a plurality of segments having alined openings, and an elongated member extending through the openings of the segments to connect the same, said segments being formed with means cooperating with the edges of the metal forming the heating element to maintain the insulating supports in position, a refractory disk adjacent each end of the heating element, and means for anchoring the endmost insulating supports and the ends of the metal helix to said refractory disks.

14. An electrical heating elementcomprising elongated channel-shaped heating element sections which extend adjacent to one another, insulator segments formed of refractory material positioned between said adjacent sections for spacing the latter, said insulator segments having grooves in opposite sides within which the inner sides of the heating element channels at. and holding members formed of refractory material positioned between some of said insulator segments, each holder member having means engaging with the outer sides of the heating element channels for holding the inner sides of said channels in engagement with the grooves of the insulator segments.

15. An electrical heating element comprising terial positioned between said adjacent sections for spacing the latter and projecting above and below the element, said insulator segments having grooves in opposite sides within which the edges of the heating element sections fit, and holding members formed of refractory material positioned between some of said insulator segments, each holding member having means engaging the outer sides of both heating element sections for holding the latter in engagement with the insulator segments.

16. An electrical heating element comprising a pair of elongated heating element sections which extend longitudinally adjacent one another, said sections being electrically connected to each other at one end of the element. a row of insulator segments formed of refractory material p0.

sitioned between said adjacent sections for spacing the latter and projecting above and below the element, said insulator segments having grooves in opposite sides within which the edges of the heating element sections tit, and holding members formed of refractory material positioned between some of said insulator segments, each holding member having means engaging the outer sides of both heating element sections for holding the latter in engagement with the insulator segments, said element being flexible to permit insertion in a curved duct.

HAROID N. SHAW.

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