1. An electric heating element, comprising a sheath, resistance means within said sheath for generating heat when an electrical current is passed therethrough, material within said sheath for electrically insulating said resistance means from said sheath and for conducting heat from said resistance means to said sheath, a flexible terminal conductor connected to said resistance means for conducting electrical current thereto from a source, said terminal conductor extending outwardly of an end of said sheath, and insulator means at said sheath end for conforming the outwardly extending portion of said terminal conductor to extend angularly relative to the longitudinal axis of said sheath, said insulator means having a passage through which said terminal conductor extends, said passage providing portions extending parallel and angularly with respect to the longitudinal axis of said sheath, and said insulator means including a pair of insulators having abutting surfaces, the parallel portion of said passage being formed in one insulator and both insulators having matching recesses in said abutting surfaces to form said angular
2. The construction of claim 1 wherein said insulators are held within said
3. The construction of claim 2 wherein said sheath has an opening in its side wall at said one sheath end to pass side portions of said insulators,
4. The construction of claim 3 wherein the extremity of said sheath one end
5. The construction of claim 1 wherein said passage portions are at right
6. An electric heating element, comprising a sheath, resistance means within said sheath for generating heat when an electrical current is passed therethrough, material within said sheath for electrically insulating said resistance means from said sheath and for conducting heat from said resistance means to said sheath, a multi-stranded flexible conductor wire connected to said resistance means, and insulator means at one end of said sheath providing a passage of a size to closely pass said conductor wire, said passage having a first portion innermost of said sheath which extends parallel to the longitudinal axis of the latter, and a second portion outermost of said sheath which extends angularly with respect to the first portion and leads to the exterior of said sheath, said conductor wire extending from said resistance means through said passage portions and to the exterior of said sheath for connection to a source of electrical current, said passage portions bending said conductor wire to follow their angular dispositions whereby that part of said conductor wire which extends outwardly of said second passage portion is
7. The construction according to claim 6 wherein said insulator means is contained entirely within said sheath and the latter is provided with a side opening for passage of the outwardly extending portion of said conductor wire.
BACKGROUND AND SUMMARY
In many cases it is desirable to have the conductor leads of an electric heating element bent at a sharp angle to the longitudinal axis of the heater and this is especially true of cartridge heaters where installation space is limited.
It is difficult to sharply bend the conductor leads of a heater when the leads normally extend generally parallel to the axis of the heater since the strain imposed in sharply bending the leads may fracture the electrical insulation at the heater end. Further, in some cases, it is not possible to bend the leads sufficiently to accommodate the space limitations.
Our invention provides an electric heater wherein the leads may extend at right angles from the heater sheath and this is made possible by the novel construction hereinafter described.
DESCRIPTION OF THE DRAWING
In the drawing accompanying this description and forming part of this specification, there is shown, for purpose of illustration, an embodiment which our invention may assume, and in this drawing:
FIG. 1 is an end elevational view of our improved heater,
FIG. 2 is an enlarged, fragmentary sectional view corresponding to the line 2--2 of FIG. 1,
FIG. 3 is a transverse sectional view corresponding to the line 3--3 of FIG. 2,
FIG. 4 is a separated perspective view of parts of the heater, and
FIGS. 5 and 6 are plan views of insulators and used in the heater construction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring particularly to FIG. 2 of the drawing, a core 10 of molded or extruded ceramic material is disposed within a metal sheath 11. The core 10 may be of the type shown in U.S. Pat. No. 3 217 279, issued Nov. 9, 1965, to A. C. Boggs and assigned to the same assignee as the present invention, and more than one core, as shown in said patent, may be disposed in the sheath, depending upon requirements.
The core 10 is formed with a pair of side-by-side longitudinally extending openings 12, and a resistance wire 14 is helically wound upon the periphery of the core. A contact member 15 has a rectilinear portion 16 disposed within one of the openings 12 at one end of the core, as seen in FIG. 2. The contact member has an angular portion 17 lying along the end of the core and terminating in a clip 18 which is clamped upon one end of the resistance wire 14. A similar contact member (not shown in the drawing but comparable to that shown in said Boggs patent) is connected to the other end of the resistance wire 14 and has a rectilinear portion disposed in the other opening 12 at the other end of the core.
Terminal conductors 19 are inserted into respective core openings 12 and are of a transverse size to closely fit the openings and thereby electrically engage the contact strips 15. This is also shown in said Boggs patent with the exception that in the present case the terminal conductors are in the form of twisted wire leads to impart thereto a greater degree of flexibility than the solid leads shown in said patent. Also, as shown in the patent, the leads may be used to electrically connect the resistance wires of a plurality of cores. In the present case, both leads 19 extend from one end of the sheath and the other sheath end is sealed in any suitable manner. However, it is possible to have the leads extend from opposite ends of the sheath, as shown in said patent.
Centering bushings, like the bushing 36 shown in FIG. 2, are disposed over opposite ends of the core. The busing are pre-formed of ceramic material and have recesses 37 in the periphery thereof. The core 19, with bushings 36 and leads 19 attached, is disposed within the sheath 11, and the space between the core and sheath is filled with granular refractory material 20 which may be compacted in any suitable manner to fill all voids. The peripheral recesses 37 in the bushings 36 permit the introduction of the granular refractory material. Thereafter, a layer of suitable cement 21 is inserted into the sheath end to cover the end of the adjacent centering bushing 36. The cement 21 may be of any suitable type which sets to rock-like hardness and has electric-insulating heat-resistant qualities. Next, a thin layer of cement 22 is applied over the cement 21. The cement 22 may be of the type marketed by the Carborundum Company under the name Fiberfrax and is a coating cement which will withstand heat in the range of about 2,300° F. and resist thermal shock.
Up to this time, the twisted wire leads extend outwardly from the heater sheath and are rectilinear and generally parallel to the longitudinal axis of the sheath, as suggested in the phantom lines 19a in FIG. 2. Thereafter sleeves 23, of woven insulating threads, are inserted over the rectilinear leads 19a,and insulator means are assembled with the leads and are disposed within the sheath end. The insulator means provide passages for each of the sleeved, flexible leads, each passage having a portion to receive an inner end of a lead and a further portion to conform the lead to extend angularly with respect to the longitudinal axis of the sheath.
As best seen in FIG. 4, the sheath end is formed with a side opening 24 and the leads 19a extend rectilinearly from the sheath end. The sleeves 23 may be of the type known as ExFlex 1,500 sleeving made by Bentley-Harris Company. Preferably the inner ends of the sleeves are flared, as shown at 24, and dipped in Fiberfrax cement. The sleeves 23 are disposed over the rectilinear flexible leads to abut the flared ends 24 firmly against the face of the cement 22 before the latter has set.
Thereafter, the insulator means are applied. In the embodiment herein disclosed, the insulator means are in the form of two disc-like molded ceramic members 25,26 which have flat faces 27,28 respectively, adapted to abut each other. The ceramic members have peripherally extending wings 29, 30, respectively, for a purpose to appear.
The member 25 has a pair of openings 31 extending therethrough, and a pair of grooves 32, substantially semi-circular in cross-section, extending in parallel relation from the openings 31 to the periphery of the wing 29. The member 25 is disposed over the sleeved leads while the latter are rectilinear, so that the leads extend through the openings 31 with the grooves 32 outermost and the face of the member opposite the face 27 disposed against the cement 22. It will be noted in FIG. 2 that the ceramic member 25 clamps the extremity of the flared ends 24 against the cement 22 and causes such ends to spread and become embedded in the cement.
The sleeved leads are bent at right angle about the corner 33 formed between the openings 31 and the grooves 32. The ceramic member 26 has a pair of semi-circular grooves 34 formed in its face 28, the grooves 34 being complementary to the grooves 32 in the member 25. The member 26 is assembled with its face 28 abutting the face 27 of member 25, so that the complementary grooves 32, 34 form a circular passageway for the sleeved leads. Thereafter, a metal washer 50 is disposed over the outer face of the member 26 and the extremity of the sheath end is bent inwardly, as shown at 35 in FIG. 2 to lock the ceramic members 25 and 26 in position. In this locking operation, the ceramic members 25,26 are forced inwardly of the sheath so that the inner face of the member 25 clamps over the flared ends 24 of the sleeves 23, and such inner face also acts as a piston to extrude the cement 22 to fill all voids in the adjacent area.
The wings 29 and 30 of the members 25,26 are disposed within the opening 24 in the sheath end and fit closely therein to locate the ceramic members and hold them against rotation. The sleeved leads are therefore bent within the sheath 11 and the outer ends thereof extend at right angles from the side of the sheath.