US2959661A - Electric band type heater - Google Patents

Description

1960 T. A. BOTHWELL ETAL 2,959,661

ELECTRIC BAND TYPE HEATER Filed June 1'7. 1959 ELECTRIC BAND TYPE HEATER Thomas A. Bothwell, Middletown, and Rudolph A. Krasovec, Whitehouse Station, N.J., assignors to Glenn Electric Heater Corporation, Newark, Ni, a corporation of New Jersey Filed June 17, 1959, Ser. No. 820,899

Claims. (Cl. 219-19) This invention relates generally to the field of electric heaters, and more particularly to an improved type of band type heater adapted to surround a tubular conduit or similar structure. Devices of the type contemplated by the present invention are known in the art, and the invention resides in specific constructional details in the disclosed embodiment.

It is among the principal objects of the present invention to provide an improved band type heater of the class described in which the heating elements disposed therein are supported in such manner that thermal expansion is readily possible without damage either to the elements themselves or th supporting structure. As is well known in the art, where the component parts of a heater are of different configuration, and/or formed of materials having different thermal coefiicients of eX- pansion, difficulty has been encountered in using the devices in such manner as to avoid damage to any of the component parts, with resultant shortening of the useful life of the device.

Another object of the invention lies in the provision of improved band type heater construction including a plurality of segmented heat transmitting elements of highly conductive material in combination with a strap and cover element to provide a substantially complete enclosure of elongated heating elements disposed therebetween, in such manner as to completely shield the same without limiting thermal expansion of the heating elements.

Still another object of the invention lies in the provision of an improved band type heater construction which may be readily modified for use in conjunction with varying voltages and wattages by substitution of interchangeable heating elements.

Still another object of the invention lies in the provision of a heater band which will effectively combine the durability of the cast-in type band, with the manfacturing economy of the mica insulated band heater.

These objects, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claims.

In the drawing, to which reference will be made in. the specification, similar reference characters have been employed to designate corresponding parts throughout the several views.

Figure 1 is a view in perspective of an embodiment of the invention.

Figure 2 is a vertical transverse sectional view partly broken away as seen from the plane 22 on Figure 1.

Figure 3 is a vertical longitudinal sectional view as seen from the plane 33 on Figure 1.

Figure 4 is a view in perspective showing an individual heating element which comprises a part of the embodiment.

Figure 5 is a fragmentary radial sectional view as seen from the plane 55 on Figure 1.

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Figure 6 is a view in perspective showing a portion of a heating element.

In accordance with the invention, the device, generally indicated by reference character 10, comprises broadly: a plurality of segmented heat-transmitting elements 11, a plurality of heating elements 12, a combination strap and heating element cover element 13, and a terminal box element 14.

The heat-transmitting elements 11 are generally similar, each including an inner surface 16 adapted to contact the outer surface of a pipe (not shown) or other tubular conductor. Edge surfaces 17 and 18 are disposed perpendicular to the inner surface 16, while inner surfaces 19 and 20 are substantially parallel to the lower surface 16. A surface 21, recessed with respect to the surfaces 19 and 20, is provided with inwardly extending arcuate grooves 22 and 23 in which the heating elements 12 are disposed, while certain of the elements 11 are provided with lateral grooves 24 to permit the heating elements to be looped in a reverse direction. Rabbet portions 25 and 26 form a supporting surface for the strap and cover element 13 when in engaged position, as will more fully appear.

The heating elements 12 are preferably of a magnesium oxide or similar granular oxide insulated type, including a centrally disposed heating core 35 through which electrical power is permitted to fiow, an electrically insulative layer 36, and an outer metallic shield 37. As is Well known in the art, the insulative layer 36 is preferably of magnesium oxide, which is electrically insulative while readily transmitting heat without deterioration. The heating elements 12 are of generally arcuate configuration to correspond to the shape of the heat-transmitting elements 11, and are provided with outwardly extending portions 38 mounting threaded terminals 39 thereon. Square terminal assemblies 38 permit connections from any desired angle, and allow, for example, the use of straight bus bars for electrical connections to adjacent heaters. Alternate positions of the same are shown in Figures 2 and 3, wherein it will be observed that headed over pintles 39' support the assemblies 38'.

The strap and cover element 13 is preferably formed of a metal having a low coefiicient of thermal expansion. The same is preferably of utilized construction, and includes first and second terminals 45 and 46, respectively, each of which is provided with a loop 47 to accommodate threaded interconnection means 48. The means 48 include a transverse rod 49 having a bore 50, as well as a second threaded transverse rod 51. The threaded bolt 52 extends through openings 53 and 54. Screw means 55 serves to interconnect the element 13 with the upper two heat-transmitting elements 11, the lower transmitting elements 11 being supported by the heat-transmitting element when the device is opened by removal of the bolt 52. The screw means 55 also serves to maintain the terminals 38 at proper clearance,

As best seen on Figures 2 and 3, the central portion 56 of the element 13 is provided with cut-out portions 56 and 57 to accommodate the outwardly extending portions 38 of the heating elements 12. This portion is reinforced by a similarly shaped reinforcement member 58 welded thereto. The reinforcement member 58 includes a central arcuately shaped portion 59 and a pair of radially extending flanges 60 at either end thereof. The flanges 60 include a plurality of threaded bores 61, best seen in Figure 2.

The terminal box element 14 may be formed from a single stamping of metallic planar material, and includes sidewalls 66 and 67, a top wall 68, and end walls 69 and 70, the latter of which includes an opening 71 through which a. power cable (not shown) may extend. Extending downwardly from the end walls 69 and 70 are angularly offset mounting flanges 72 which provide means for engaging the flanges 60, whereby the box element 14 may be supported upon the strapand cover element 13.

During use, it will-be ;observed that owing to the relatively low coefficient of thermal-expansion of the strap and cover element 13, which is substantially less than that of the segmented heat-transmitting elements ll and heating elements 12, the hotter the device becomes, the tighter and more complete the contact betweenthe surface 16 of each of the elements 11 with respect to the pipe or conduit being heated. The heating elements 12, which ride within the grooves'22 and 23, and are maintained therein solely by the cross sectional shape of the grooves, which are seen in Figures 3 and 5 are formed with a circumference of greater than 180 degrees. Thus, although the heating elements are initially snapped into position past adead center point, they are free to expand within the grooveswithout damage to either the heating elements 12 or the heat-transmitting elements 11.

It may thus-be seen that we have invented novel and highly useful improvements in electric band type heaters, in which a high efliciency durable construction may be produced at a reasonably low cost. Where desired, substitution of heating elements may be made with relatively little effort on the part of the user, thereby permitting the remaining components of the device to be again utilized over a period of time which is greater than the life of the individual heating elements. The device may be made in a Wide variety of sizes and power consumption, and where desired, three heating elements may be arranged for use in conjunction with three phase current.

We wish it to be understood that we do not consider the invention limited to the precise details of structure shown and set forth in this specification, for obvious modifications will occur to those skilled in the art to which the invention pertains.

We claim:

1. In an electric band type heater of the type described, a plurality of segmented heat-transmitting elements of generally arcuate configuration, said heat-transmitting elements having a generally curved inner heattransmitting surface, a pair of outer edge surfaces, and a pair of upper surfaces defining a circular recess therein, said recess being bounded by a recessed surface and a pair of rabbet portions disposed adjacent said outer edge surfaces, said recessed surface in turn having at least one elongated groove extending therefrom into the body of said heat-transmitting elements; an elongated heating element disposed within said elongated groove and capable of thermal expansion, and a strap element surrounding said heat-transmitting element and adapted to lie upon said recessed surface to constrict said heat-transmitting elements upon an object to be heated while supported by said recessed surface to be substantially free of contact with said heating element.

2. In an electric band type heater of the type described, a plurality of segmented heat-transmitting elements of generally arcuate configuration, said heat-transmitting elements each having a generally curved inner heat-transmitting surface, a pair of outer edge surfaces, and a pair of upper surfaces defining a circular recess therein, said recess being bounded by a recessed surface and a pair of rabbet portions disposed adjacent said outer edge surfaces, said recessed surface in turn having a plurality of elongated parallel recesses therein.

3. In an electric band type heater of the class described, a plurality of segmented heat-transmitting elements of generally arcuate configuration, said heat-trans- .4 mitting elements having a generally curved inner heattransmitting surface, a pair of outer edge surfaces and a pair of upper surfaces defining a circular recess therein, said recess being bounded by a recessed surface and a pair of rabbet portions disposed adjacent said outer edge surfaces, said recessed surface in turn having at least one elongated groove extending therefrom into the body of said heat-transmitting elements; said groove having a generally quasi-arcuate. cross-section; an elongated heating element of generally circular cross-section disposed within said elongated groove and capable of thermal expansion, and a strap element surrounding said heat-transmitting element and adapted to lie upon said recessed surface to constrict said heat-transmitting elements upon an object to be heated while supported by said recessed surface to be substantially free of contact with said heating element.

4.1m an electric band type heater of the class described, a pluralityof segmented heat-transmitting elements ofgenerally arcuate configuration, said heat-transmitting elements. having a generally curved inner heattransmitting surface, a pair of outer edge surfaces and a pair of upper surfaces defining a circular recess therein, said recess being bounded by a recessed surface and a pair of rabbet portions disposed adjacent said outer edge surfaces, said recessed surface in turn having at least one elongated groove extending therefrom into the body of said heat-transmitting elements; said groove having a generally quasi-arcuate cross-section; an elongated heating element of generally circular cross-section disposed within saidelongated groove and capable of thermal expansion, and a strap element surrounding said heat-transmitting element and adapted to lie upon said recessed surface to constrict said heat-transmitting elements upon an object to be heated while supported by said recessed surface to be substantially free of contact with said heating element; the arcuate portion of said recess being greater than whereby said heating element may be maintained within said groove by the cross-sectional shape of said groove.

5. In an electric band type heater of the class described, a heat-transmitting element of generally arcuate configuration, said heat-transmitting element having a generally curved inner heat-transmitting surface, a pair of outer edge surfaces, and a pair of upper surfaces defining a circular recess therein, said recess being bounded by a recessed surface and a pair of rabbet portions disposed adjacent said outer edge surfaces, said recessed surface in turn having at least one elongated groove extending therefrom into the body of said heat-transmitting element; an elongated heating element disposed within said elongated groove and capable of thermal expansion, said groove having an arcuate configuration of greater than 180, whereby said heating element may be maintained within said groove by the cross-sectional shape of said groove.

ReferencesCited in the file of this patent UNITED STATES PATENTS 2,029,075 Knight Jan. 28, 1936 2,545,653 Desloge Mar. 20, 1951 2,740,035 Young Mar. 27, 1956 2,786,125 Drugmandet al. Mar. 19, 1957 2,851,577 Bolds et al, Sept. 9, 1958 FOREIGN PATENTS 720,939 Great Britain Dec. 29, 1954

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