Band-type Electric Heaters

Abstract

A band-type electric heater adapted to be secured around the periphery of a cylindrical object to be heated, comprising an elongated metal-sheathed electric heater bent longitudinally to arcuate shape so that an inner surface follows the curvature of the object, and a flexible metal clamping band adapted to encompass the object and overlie the outer surface of the heater, and having means to draw it tightly around the object and thereby press the heater inner surface against the periphery of the object. The band has embossments which engage the heater outer surface and limit surface-to-surface contact between the band and the heater, to thereby reduce the amount of heat conducted to the band, and to also reduce frictional contact between the band and the heater to permit the two to move relatively and adjust to conform to good heating relationship with the object at the time the band is drawn tightly around the object.

Description

BACKGROUND AND SUMMARY

Band-type heaters of the general construction herein disclosed are known in the prior art, and a good example is found in U. S. Pat. No. 2 545 653. In this patent, the band has full contact with the heater and as a result considerable heat is transmitted to the band. This is objectionable not only because of heat loss butalso because the highly heated band may be dangerous to certain things in its environment. Full contact of the band with the heater is also objectionable because the high frictional contact sometimes prevents relative movement therebetween and hinders adjustment of the parts to conform to good heating relationship with the object to be heated at the time the band is drawn tightly around the object.

I have discovered that by forming embossments in the band to limit surface-to-surface contact between the band and the heater, the foregoing disadvantages are eliminated without sacrificing any of the desirable features of band-type heaters.

DESCRIPTION OF THE DRAWINGS

In the drawings accompanying this description and forming a part of this specification, there is shown, for purpose of illustration, an embodiment which my invention may assume, and in these drawings:

FIG. 1 is a face view of a band-type electric heater, which is clamped around a cylindrical object,

FIG. 2 is a side view of the heater shown in FIG. 1,

FIG. 3 is a perspective view of one of two similar metal-sheathed electric heaters forming part of the assembly shown in FIG. 1 and 2,

FIG. 4 is a plan view of the clamping band, prior to bending it to circular shape,

FIG. 5 is an edge view of the band shown in FIG. 4,

FIG. 6 is an enlarged, fragmentary sectional view corresponding to the line 6--6 of FIG. 1,

FIG. 7 is a fragmentary sectional view corresponding to the line 7--7 of FIG. 6, and

FIGS. 8 through 10 are fragmentary plan views of the clamping band, showing various forms of embossments.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The band-type heater is adapted to be secured around a cylindrical object O which may be an extrusion nozzle, a water tank, or the like. The heater comprises two similar metal-sheathed electric heating elements 15,15 of any suitable type. In the presently disclosed embodiment, the elements are of the so-called "mica heater" type wherein a resistance wire or ribbon 16 is wound to sinuous form and disposed between layers 17 of mica, the assembly being contained within a metal sheath 18 of rectangular cross-section, as seen in FIG. 6, which was originally of trough form, the legs of the trough being bent inwardly over a closure plate 19. The bottom of the trough forms the inner surface 20 of the heater, and the closure plate 19 forms the heater outer surface. The heating element 15 has terminals 22 at opposite ends, and each terminal extends transversely from the heater outer surface 19 and is adapted to be connected in circuit with a power source. The terminals 22, in accordance with usual practice, are electrically connected to opposite ends of the resistor wire 16 within the heating element. Instead of mica insulation, the insulating material may be of any other suitable form. Each heater 15 is elongated and bent longitudinally to an arcuate shape so that the inner surface 20 follows the curvature of the periphery of the object O.

The clamping band 23 is made of flexible metal strip, such as stainless steel, and is of the split band type with means at the split for drawing the band tightly around the object O and thus in turn press the electric heaters into engagement with the peripheral surface of the object O.

Asbest seen in FIGS. 4 and 5, the clamping band comprises a central strap 24, a pair of jumper straps 25,25 and a pair of end straps 26,26. The straps may be of the same gauge strip and the central strap 24 and end straps 26,26 may be of the same width, as seen in FIG. 4. The jumper straps 25,25 are preferably wider, and each is formed with a relatively large and elongated opening 27.

One end of each jumper strap 25 is connected to an end of the central strap 24, as by spot welds 30. The opposite end of each jumper strap 25 is connected to an end of an end strap 26, as by spot welds 31. The opposite end of each end strap 26 is doubled over and spot welded as shown at 32, to form a loop 33. The loops 33 contain barrel nuts 34 (FIG. 1) through which is threaded a clamping bolt 35.

In the assembly, the two electric heaters are disposed in end-to-end relation within the band 23, as seen in FIG. 1, with the facing ends in alignment with the jumper straps 25 so that the terminals 22,22 at such facing ends freely project through the openings 27 in respective jumper straps 25, as see in FIG. 2.

The central strap 24 is formed with a plurality of embossments which, as shown in FIG. 4, are circular depressions 36 arranged in staggered relation. The embossments engage the outer surface 19 of the lower heater 15, as seen in FIG. 1, and limit surface-to-surface contact between the central strap 24 and the heater outer surface 19 to thereby reduce the amount of heat conducted to the clamping band and to also reduce the frictional contact between the central strap and the heater to permit the same to move relatively and adjust to conform to good heating relationship with the object O at the time the clamping band is drawn tightly around the object. Again referring to FIG. 4, it will be noted that each end band has a single embossment 37 and these function in the same manner as the embossments 36.

The embossments in the central strap 23 may be arranged in single file, as shown at 36a in FIG. 8, or in spaced pairs as shown at 36b in FIG. 9. Further, the embossments may be elongated and extend transversely of the central strap 23, as shown at 37c in FIG. 10.

Claims

I claim:

1. A band-type electric heater adapted to be secured around the periphery of a cylindrical object to be heated, comprising:

a pair of elongated metal-sheathed electric heaters, each bent longitudinally to an arcuate shape so that an inner surface follows the curvature of said object, each heater having a terminal at its opposite ends which extends transversely from the outer surface of the same,

and a split, flexible metal clamping band adapted to encompass said object and means at the split to draw the band tightly around said object,

said band comprising a central strap, a pair of jumper straps, each having an end connected to an end of said central strap and each having an elongated opening therein, and a pair of end straps, each having an end connected to the opposite end of a jumper strap and having means at its opposite end to receive a part of the means to draw said band tightly around said object,

in assembly, said heaters being disposed in end-to-end relation within said band with pairs of facing ends in alignment with respective jumper straps and with terminals at facing ends extending freely through an opening in a jumper strap, and with said central strap, said jumper strap and said end straps overlying and pressing against the outer surface of each heater to press the inner surface of the same against the periphery of said object when said band is drawn tightly around the latter,

said central strap having embossments which engage the adjoining outer surface of at least oneheater and limit surface-to-surface contact therebetween,thereby reducing the amount of heat conducted to said band, and also reducing the frictional contact between said central strap and the heater to permit the same to move relatively and adjust to conform to good heating relationship with said object at the time the band is drawn tightly around said object.

2. The construction according to claim 1 and further including at least one embossment in said end straps to perform the same function as the embossments in said central strap.

3. The construction according to claim 2 wherein said end straps are considerably shorter than said central strap, and each end strap has a single embossment formed therein.