US3666922A - Thermal controlled disposable unit heating apparatus - Google Patents

Abstract

Heating apparatus for synthetic yarn processing comprising a pin or plate heater having a passive portion for attachment to a machine to provide and maintain predetermined alignment for a load contacting element of a removable and replaceable active portion. The thin load contacting element carries a thin etched foil heater and intimate resistance sensor bonded to its inner surface and is equipped with electrical leads to comprise the disposable active portion. The passive portion further thermally isolates the active portion to ensure high efficiency in transferring heat to the yarn load. Fast response inexpensive metals serve as the load contacting element so the compact low mass foil heater requires less power, responds quicker, and weighs and costs less than conventional yarn heaters.

Description

United States Patent Leitner et al.

1 51 May 30, 1972 [54] THERMAL CONTROLLED DISPOSABLE UNIT HEATING APPARATUS [72] Inventors: Frank W. Leitner; Clayton 0. Miller, both of Charlotte, N.C. 1

[73] Assignee: Coltron Industries, Inc., Charlotte, NC.

[22] Filed: Nov. 18, 1969 [21] App]. No.: 877,654

s21 U.S.Cl .....219 469,219/536,219 542 511 1111.01 ..B21b27 04 5s FieldoiSearch ..219/318,351,403,447,469, 219/463, 536, 542, 470, 471, 543, 388

[56] References Cited UNITED STATES PATENTS 2,870,312 1/1959 Westervelt ..219 543 3,414,711 12/1968 Guyetetal ...219/470x 3,417,226 12/1968 Thomiszer.. ...2l9/388X 3,296,418 6/1967 Johnson ..219/469 3,484,581 12/1969 Bliss ..219/469 Primary Examiner-Bemard A. Gilheany Assistant Examiner-F. E. Bell Attorney-Wilfred G. Caldwell ABSTRACT Heating apparatus for synthetic yarn processing comprising a pin or plate heater having a passive portion for attachment to a machine to provide and maintain predetermined alignment for a load contacting element of a removable and replaceable active portion. The thin load contacting element carries a thin etched foil heater and intimate resistance sensor bonded to its inner surface and is equipped with electrical leads to comprise the disposableactive portion. The passive portion further thermally isolates the active portion to ensure high efficiency in transferring heat to the yarn load. Fast response inexpensive metals serve as the load contacting element so the compact low mass foil heater requires less power, responds quicker, and weighs and costs less than conventional yarn heaters.

17 Claims, 10 Drawing Figures Patented May 30, 1972 3 Sheets-Sheet 2 INVENTORS CLAYTON Q MILLER FRANK W. LEITNER BY M g (M ATTORNEY Patented May 30, 1972 3,666,922

3 Sheets-Sheet 5 INVENTORS CLAYTON O. MILLER FRANK W LEITNER BY MW W ATTORNEY THERMAL CONTROLLED DISPOSABLE UNIT HEATING APPARATUS The present invention relates to controlled heater apparatus in general and, in particular, to controlled heating surfaces for synthetic yarn processing, to household appliances or to other applications where temperature control is the significant requirement, but wherein'it is desirable to permit replacement of the active heater portion without disturbing the thermal control characteristics of the system.

The invention will be explained in connection with the illustrated application thereof to industrial pin or plate heaters; it being understood that various other or different shaped apparatus including rotating roll heaters, drum heaters, motorized roll heaters, and heated godets, as well as steam or non-steam irons may be made incorporating the principles herein taught.

In a typical installation, up to 144 heaters may be employed on a given machine or at a single location and, of course, even hundreds and thousands may be used in a single factory. With the. ever increasing cost of labor, it can be readily appreciated that in dealing with such magnitudes the disposable element or unit approach is almost mandatory to financial survival.

The present invention proposes the rapid disassembly of the apparatus through the release of a single fastener, which may be of a common type for all models, to remove and replace the active or disposable unit without disturbing mechanical alignment or thermal control characteristics of the repaired heater.

In the usual case, the active unit will comprise the load supporting or wearing surface, a heating element and one or more sensors, the electrical wiring or cable, and the connector for the wires of the cable. The inactive unit will include the mounting structure for the active elements which mounting structure maintains intact the mechanical alignment with the load, such that the new wearing surface assumes the location and configuration of the one replaced without requiring any adjustments. 1 I I The heating elements are preferably of the type described in copending U. S. application, Ser. No. 779,778 entitled Logical Control For Discretely Metering Energy To Thermal Systems Incorporating Apparatus and Methods For Simulating Time Related Temperatures" filed Nov. 29, 1968 by Frank W. Leitner and Bobby B. Childress and assigned to Coltron Industries, Incorporated. These heaters are characterized by extreme thinness as they usually comprise etched heater elements in thermoplastic materials with one or more sensing elements of the resistance type being in intimate relation with the heater elements.

Such heaters may be used with very thin, relatively inexpensive materials to comprise a much improved pin or plate heater compatible to high speed control from on-off type energization, with suitable controls also being depicted in the above identified application.

In the present pin heater, the load contacting surface is a cylinder having affixed to its interior the'thin heater and sensor. The passive portion thermally isolates and supports the cylinder in a given position and orientation for cooperation with other machine components in efiecting drawing, twisting, draw-twisting, and etc..

By way of example, the present pin heater is compared to conventional pin heaters A and B in the following table:

' Pin Pin Present Heater A Heater B O.D. 2'' 2" 2" Length 2.125 2.125" 2.125 Wall Thickness .059" .375" 0.375" Material Steel Aluminum Brass Relative Thermal Capacitance l 2.1 5.7

Wattage I50 200 220 Time to elevate from 1 25C to 175C (secs) 72 I62 270 Relative Response Time (secs) 1 2.25 3.75

efficiency because of low losses, and enables overall less power requirements because of less and better suited materials and more efiicient interrelation or cooperation of the elements in the compact heater unit.

The invention is also depicted and described hereinafter in connection with its application to a plate heater whereinthe active portion includes the same elements with the load surface or wearing surface being an elongated strip that is arcuate but not cylindrical and the mounting structure being slightly more elaborate than that necessary to a pin heater. However, in both types of heaters, it will be noted that thermal control is inherently built into the mounting structure to isolate the wearing or load surface and heating and sensing element from undesirable heat loss while improving the efficiency of the heat transfer to the load. In both cases, the heating units are isolated by employing supporting members of low thermal conductivity materials and by providingair gaps or dead air spaces infurther'insulating relation thereto. Thus, the elongated, relatively narrow work surface for the plate heater is isolated by longitudinal air gaps from the mounting structure. The present foil heater element permits the entire heating unit to be quite thin and, thus, heat does not flow readily along the strip length to be lost at the ends, nor across the strip width.

The described plate heater improves over conventional plate heaters A and B as shown in the table below:

Deten'nined by thermal watts/thermal capacitance ratio and efficiency of thermal coupling.

With the foregoing in mind, it is among the objects of the invention to provide an improved heating apparatus incorporating a readily removable active unit for replacement purposes.

Another object of. the invention is the provision of such a heater apparatus utilizing a thin wearing or load contacting surface and a thin heating element bonded thereto.

A further object of the invention is the provision of such apparatus in various types all adapted for replacement of the active unit through the use of a single fastener.

A. still further object is the provision of such heating apparatus capable of incorporating relatively inexpensive thin material for faster thermal response than heretofore available.

Another object of the invention is the provision of thermal control apparatus wherein each heating unit incorporates an active and a passive part and wherein the passive part is the mount or support for the active part and remains connected to a machine or the like while permitting ready replacement of I the active portion without disturbing of any alignment.

The invention will be better understood from the reading of the following detailed description, when taken in the light of the accompanying drawings wherein:

FIG. 1 is a perspective view of the new pin heater;

FIG. 2 shows, in perspective, the active or replaceable portion of the heater ofFIG. l;

' FIG. 3 is a view primarily in cross section of the heater of FIG. 1;

FIG. 4 is a view in end elevation of the heater of FIG. 1', FIG. 5 is an end view of the connector of FIG. 1;

FIG. 6;

FIG. 9 is a view of the other end of the heater of FIG. 6 showing provisions to provide ready disassembly; and

FIG. 10 is a view in perspective of the active unit of the heater of FIG. 6.

In FIG. 1, a fully assembled pin heater 11 is shown ready for mounting to a machine panel 41 (FIG. 3). It comprises a load contacting surface or body 13 mounted to a frame 15, in turn adapted to be secured to a machine or the like by means of stud screw 21.

The cylindrical heater body is secured to circular frame 15 by means of a screw 23 fastening end plate 25 against the load surface cylinder 13, and in turn connected to coupling nut 45 (see FIG. 3).

In FIG. 1, a cable 19 brings out the electrical leads 35 to connector 17 by way of slot 29 in frame 15, with the cable 19 being retained in the slot 29 by a compressible or a non-compressible bushing or grommet 27. I

Referring now collectively to FIGS. 1 through 5, it may be seen that the active or replaceable unit 31 of FIG. 2 comprises the load contacting surface or cylinder 13, an inner heater and sensor means 33, electrical leads 35, cable 19, grommet 27, and connector 17. Unit 33 comprises one or more flexible foil etched heater or heaters and an intimate sensor or sensors all in thermoplastic material bonded or vulcanized to the inner wall or side of the cylinder or load contacting means 13 and' the foil heater and sensor leads 35 are brought out to pins such as 37 (FIG. 5) of connector 17. Thus, it may be appreciated that this structure admits of mass production techniques at the factory at less cost than the disposable unit 31 could be returned and repaired. The units 31, then may all exhibit the same thermal characteristics so substitutions may be made without adjustments.

A feature of the invention resides in the provision of the single fastener 23 of the screw type, inserted and removed through the use of an Allen wrench, which serves as the sole connection for securing the active portion 31 to the inactive frame or mounting portion. It should be apparent that base 15 and set screw 21 affixed therethrough by the provision of nut 43 and inner coupling nut 45 are maintained in a fixed position of exact alignment with the machine panel or wall 41 (FIG. 3) regardless of whether the active unit 31 is present or not. Thus, any number of units 31 may be used as replacements and still present the same alignment of cylinder or surface 13 with wall 41, it being apparent that all other cooperating apparatus (not shown) is also aligned to wall 41. Frequently the cylinder 13'is to have an exact mutual relation to a separator roll or the like (not shown) of for-example -l0. Then the inadvertent cocking of a replacement cylinder 13 as much as one degree could change the thread path and cause it to pile up. Thus, the preservation of alignment is quite important.

It will be noted that cable 19 carries the grommet 27 which is free to slide out of the notch or slot 29 of frame 15. It should be mentioned that a nylon sleeve may be substituted for rubber grommet 27 and ordinarily a nylon string is knotted about cable 19 or a bulge formed thereon just below grommet 27 to eliminate any inadvertent strain on electrical leads 35.

When the load carrying sleeve or cylinder 13 is secured about a shoulder of base 15, a notch (not shown) in the inner end of sleeve 13 is provided to receive the stud or 45 degree angle projection 49 to re-enforce the union. It similarly will be noted that a notch 39 in connector 17 serves to insure that when the correct wires 35 are connected to the correct pins 37, the two sensing leads and the two heater terminals will be correctly located for a pluggable connection to other equipment.

It will also be appreciated that the head of screw 23 fits the countersink 47 in end cap 25, and the end cap has its edge bevelled or tapered at 35.

Considering now the structure described as an efficient pin heater, it will be noted that the wall 13 may be of thin, inexpensive steel of the order of 0.059 inches thick having bonded or vulcanized thereto a heater sensor unit of a few thousands (e.g. 13 or the like) of an inch thick. Thus, initially the heat path is directed through the surface 13 to the load, which normally would comprise synthetic strands wrapped about cylinder 13. The central or core region within the heating element 33 is a dead air space and the supporting structure is low thermal conductivity material, preferably plastic, for the base 15 and the end cap 25. Therefor, a highly efficient pin heater with -fast response performance, low wattage requirements and duplicatable characteristics from active element to active element is presented.

FIGS. 6 through 10 depict a plate heater 51 incorporating the same desirable principles for providing a high efiiciency disposable element heating apparatus. The base or frame 53 may comprise an inexpensive extruded section-of aluminum channel or the like having an upper longitudinal slot to accommodate the load carrying surface 55 (which is the only surface subject to wear) freely between the spaced apart side arms 55.

End caps 57 and 61 are provided to close the frame or channel 53 with endears 59 and 63 extending outwardly to provide ingress and egress guides for the textile fibers to be heated by surface 55. The end caps or pieces 57 and 61 also provide recesses for receiving the ends of strip 55, which strip is bowed outwardly in the middle by a plastic upright post 93 (FIG. 7). This configuration ensures that good contact is madewith the strands for providing the set point temperatures.

The heater plate assembly 5 permits removal of the active unit 101 (shown in FIG. 10) by removal of the screw 81 and end cap 57. It should be noted that screw 81 may include an Allen wrench receiving head in the manner of the pin heater assembly 1 1 of FIG. 1 in order that both heaters may be disassembled and their active portions replaced utilizing the same tool. Otherwise, the end cap 61 is more permanently secured to the channel or base frame 53 by screws 73 and 75 which are received in lugs, such as 83 and 85 (FIG. 7) molded into the low thermal conductivity material, e.g. plastic, of end cap 61.

It should be mentioned that, usually the plate heater 51 will be mounted in a vertical position, and the threaded screw holes 77, 77', 79, and 79' are provided for mounting to a machine panel or the like. Also, it should be pointed out that the side arms 55' are spaced apart sufficiently to leave air gap spacings 96 between the strip 55 and the arms for its entire length, thereby assuring that the only contact made with the strip 55 by the frame 53 is through the plastic or low thermal conductivity materials of end caps 57 and 61 and biasing post 93, the latter being secured to the bottom of base 53 by screw 95. Also, a right angle bracket 87 is permanently secured to the bottom of frame 53 to receive the screw or bolt 81 (FIG. 7).

In order to remove the cable 65 and connector 67, shown as of the fanning strip type, the channel 53 is slotted at four end locations, each shown closed by the rubber bushings or grommets 71, 71, 69, and 69. Thus, it is only necessary to remove the appropriate end cap, such as 57 and slide cable 65 out the right slotted end of channel 53, along with the strip 55 and combination heater and sensor backing 91 of the type heretofore described. Replacement is made in the reverse order.

In FIG. 10, the active unit 101 is shown including the strip 55 with heater sensor 91, electrical leads 103, cable 65, grommet 69, and connector strip 67. 104 is a second sensor for readout and is an iron constant an thermocouple It should be noted that the connectors 17 for the pin heater and 67 for the plate heater may be interchanged or may both be of the same type depending on the installation. Additionally, it may be pointed out that the interior of channel 53 may be lined with fiberglass insulation or finished inside and out with white resisting coating, even further to assist in the direction of heat from heater 91 through strip 55. The strip 55 is well insulated from its support 53, and since it is a long thin strip(in one example, approximately 8 inches by three-fourth inches) it will not conduct much heat lengthwise and thus end losses are minimized. Similarly, very little heat is conducted laterally of strip 55. Also, strip 55 may comprise fast responsive and inexpensive material, such as steel, and being thin and having reduced losses, the wattage requirements are considerably reduced in transfering the heat to the load. The strip 55 is preferably finished by flame coating.

In summary then, the active unit 101 is disposable because it can be mass produced reliably at the factory to the same specifications cheaper than it can be repaired, particularly where inexpensive materials are employed. The thinness of the strip substantially prevents lateral and longitudinal losses and the bulk of the heat. is directed outwardly to the load. This efficiency is further enhanced by the air and plastic insulation otherwise bounding strip 55.

What is claimed is;

l. Stationary or non-rotating low thermal mass heating apparatus for fast response controlled heating of a load comprising in combination a passive unit and an active unit readily disconnectible therefrom; said passive unit comprising a frame and fastening means for securing the active unit to the frame; said active unit comprising load supporting and contacting surface means, heater means for the surface means disposed against said means opposite the load contacting surface on its inner side, resistive sensor means, and electrical lead-in means for the heater means and sensor means; said supporting surface means, heater means, and sensor means being inseparably bonded together.

2. The apparatus of claim 1 wherein said frame comprises an end piece of low thermal conductivity adapted to mate with an end of the load supporting and contacting surface means to securethe latter to the frame via the fastening means.

3. The apparatus of claim 2 wherein the load supporting and contacting surface means is arcuate and the heater means is arcuate in conformity thereto.

4. The apparatus of claim 3 wherein the frame comprises a further portion of low thermal conductivity adapted to receive the opposite end of the load supporting and contacting surface means and the frame further provides air gap separation between it and the heater means.

S. The apparatus of claim 1 wherein said heating apparatus comprises a pin heater for synthetic yarn; said load supporting and contacting surface means comprises a cylinder for containing the heater means therein; and said frame comprises mounting means for securing it to a machine or the like in predetermined orientation and said frame orienting the cylinder to it and the machine whereby replacement of said active unit automatically orients the replacement cylinder in the required orientation relative to the machine.

6. The apparatus of claim 5 wherein the frame comprises spaced apart portions of low thermal conductivity for receiving opposite ends of the cylinder; said fastening means securing the portions together to orient and hold the cylinder in predetermined position. v

7. The apparatus of claim 6 wherein one of said portions is slotted to its edge at one location to accommodate the electrical lead-in means; and further comprising means carried by the lead-in means for insertion into and removal from the slotted location to permit replacement of the active unit.

8. The apparatus of claim 1 wherein said heating apparatus comprises a plate heater for synthetic yarn; said load supporting and contacting surface means comprises an elongated strip; said heater means substantially conforming to the configuration of the strip and disposed on its inner side relative to the frame; and said frame being adapted to be secured to a machine or like in predetermined orientation and said frame orienting said strip to it and to the machine whereby replacement of said active unit automatically orients the replacement strip in the required orientation relative to the machine.

9. The apparatus of claim 8 wherein the frame comprises spaced apart portions of low thermal conductivity for receiving opposite ends of the strip, said fastening means securing the portions together to orient and to hold the strip in predetermined position.

10. The apparatus of claim 9 wherein the frame is slotted to its edge at one location to accommodate the electrical lead-in means; and further comprising means carried by the lead-in means for insertion into and removal from the slotted location to permit replacement of the active unit.

11. Heater apparatus capable of fast thermal response and the use of disposable components to supply controlled heat to a load, comprising in combination an active unit and a passive unit, said activeunit comprising a heater body characterized by low thermal capacitance for contact with the load on one side thereof, combination heating and resistive sensor means permanently affixed to the other side of the heater body and characterized by thinness of the order of less than a major portiori of the thickness of the heater body, and electrical leads for the heating means; said passive unit comprising frame means for aligning and supporting the heater body, and means for releasing the heater body and fastening a replacement heater body in the alignment of the replaced heater body.

12. The heater apparatus of claim 11 wherein said frame means comprise elements of low thermal conductivity material for supporting the heater body at more than a single location and for otherwise isolating the heating means through air insulation. I

13. The heater apparatus of claim 12 wherein the heater body is arcuate and the heating means is arcuate in conformity thereto.

14. The heater apparatus of claim 13 comprising a pin heater for a synthetic yarn load; said heater body comprising a cylinder for containing the heating means; and said frame means being adapted to be secured to a machine or the like in predetermined alignment to establish alignment of the cylinder relative to the machine.

15. The apparatus of claim 13 comprising a plate heater for a synthetic yarn load; said heater body comprising an elongated strip; and said frame means being adapted to be secured to a machine or the like in predetermined alignment to establish alignment of the strip relative to the machine.

16. Plate heater apparatus for the efficient heating of a load of moving synthetic yarn comprising in combination a relatively thin, narrow, but elongated heater body of a material characterized by relatively fast thermal response time of the order of steel for contact along one elongated surface thereof with the load; frame means of low thermal conductivity material for supporting the body by its ends and for providing air gaps along the edges between said ends; heating and resistive sensing means permanently affixed to the opposite surface of the heater body and characterized by extreme thinness relative to the body; electrical leads permanently connected to the heating and sensing means; and means for readily releasing the heater body, heating and resistive sensing means and electrical leads therefor from the frame means to permit replacement thereof without otherwise disturbing the frame means.

17. The apparatus of claim 11 wherein said combination heating and resistive sensor means are substantially in the same plane when seen in a cross-section view taken through the heater body and combination heating and resistive sensor means.

Claims (17)

1. Stationary or non-rotating low thermal mass heating apparatus for fast response controlled heating of a load comprising in combination a passive unit and an active unit readily disconnectible therefrom; said passive unit comprising a frame and fastening means for securing the active unit to the frame; said active unit comprising load supporting and contacting surface means, heater means for the surface means disposed against said means opposite the load contacting surface on its inner side, resistive sensor means, and electrical lead-in means for the heater means and sensor means; said supporting surface means, heater means, and sensor means being inseparably bonded together.

2. The apparatus of claim 1 wherein said frame comprises an end piece of low thermal conductivity adapted to mate with an end of the load supporting and contacting surface means to secure the latter to the frame via the fastening means.

3. The apparatus of claim 2 wherein the load supporting and contacting surface means is arcuate and the heater means is arcuate in conformity thereto.

4. The apparatus of claim 3 wherein the frame comprises a further portion of low thermal conductivity adapted to receive the opposite end of the load supporting and contacting surface means and the frame further provides air gap separation between it and the heater means.

5. The apparatus of claim 1 wherein said heating apparatus comprises a pin heater for synthetic yarn; said load supporting and contacting surface means comprises a cylinder for containing the heater means therein; and said frame comprises mounting means for securing it to a machine or the like in predetermined orientation and said frame orienting the cylinder to it and the machine whereby replacement of said active unit automatically orients the replacement cylinder in the required orientation relative to the machine.

6. The apparatus of claim 5 wherein the frame comprises spaced apart portions of low thermal conductivity for receiving opposite ends of the cylinder; said fastening means securing the portions together to orient and hold the cylinder in predetermined position.

7. The apparatus of claim 6 wherein one of said portions is slotted to its edge at one location to accommodate the electrical lead-in means; and further comprising means carried by the lead-in means for insertion into and removal from the slotted location to permit replacement of the active unit.

8. The apparatus of claim 1 wherein said heating apparatus comprises a plate heater for synthetic yarn; said load supporting and contacting surface means comprises an elongated strip; said heater means substantially conforming to the configuration of the strip and disposed on its inner side relative to the frame; and said frame being adapted to be secured to a machine or like in predetermined orientation and said frame orienting said strip to it and to the machine whereby replacement of said active unit automatically orients the replacement strip in the required orientation relative to the machine.

9. The apparatus of claim 8 wherein the frame comprises spaced apart portions of low thermal conductivity for receiving opposite ends of the strip, said fastening means securing the portions together to orient and to hold the strip in predetermined position.

10. The apparatus of claim 9 wherein the frame is slotted to its edge at one location to accommodate the electrical lead-in means; and further comprising means carried by the lead-in means for insertion into and removal from the slotted location to permit replacement of the active unit.

11. Heater apparatus capable of fast thermal response and the use of disposable components to supply controlled heat to a load, comprising in combination an active unit and a passive unit, said active unit comprising a heater body characterized by low thermal capacitance for contact with the load on one side thereof, combination heating and resistive sensor means permanently affixed to the other side of the heater body and characterized by thinness of the order of less than a major portion of the thickness of the heater body, and electrical leads for the heating means; said passive unit comprising frame means for aligning and supporting the heater body, and means for releasing the heater body and fastening a replacement heater body in the alignment of the replaced heater body.

12. The heater apparatus of claim 11 wherein said frame means comprise elements of low thermal conductivity material for supporting the heater body at more than a single location and for otherwise isolating the heating means through air insulation.

13. The heater apparatus of claim 12 wherein the heater body is arcuate and the heating means is arcuate in conformity thereto.

14. The heater apparatus of claim 13 compRising a pin heater for a synthetic yarn load; said heater body comprising a cylinder for containing the heating means; and said frame means being adapted to be secured to a machine or the like in predetermined alignment to establish alignment of the cylinder relative to the machine.

15. The apparatus of claim 13 comprising a plate heater for a synthetic yarn load; said heater body comprising an elongated strip; and said frame means being adapted to be secured to a machine or the like in predetermined alignment to establish alignment of the strip relative to the machine.

16. Plate heater apparatus for the efficient heating of a load of moving synthetic yarn comprising in combination a relatively thin, narrow, but elongated heater body of a material characterized by relatively fast thermal response time of the order of steel for contact along one elongated surface thereof with the load; frame means of low thermal conductivity material for supporting the body by its ends and for providing air gaps along the edges between said ends; heating and resistive sensing means permanently affixed to the opposite surface of the heater body and characterized by extreme thinness relative to the body; electrical leads permanently connected to the heating and sensing means; and means for readily releasing the heater body, heating and resistive sensing means and electrical leads therefor from the frame means to permit replacement thereof without otherwise disturbing the frame means.

17. The apparatus of claim 11 wherein said combination heating and resistive sensor means are substantially in the same plane when seen in a cross-section view taken through the heater body and combination heating and resistive sensor means.

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