CA1100560A - Ceramic band heater and method for making the same - Google Patents
Ceramic band heater and method for making the sameInfo
- Publication number
- CA1100560A CA1100560A CA269,213A CA269213A CA1100560A CA 1100560 A CA1100560 A CA 1100560A CA 269213 A CA269213 A CA 269213A CA 1100560 A CA1100560 A CA 1100560A
- Authority
- CA
- Canada
- Prior art keywords
- assembly
- heater
- recited
- housing
- ceramic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/54—Heating elements having the shape of rods or tubes flexible
- H05B3/58—Heating hoses; Heating collars
Landscapes
- Resistance Heating (AREA)
- Surface Heating Bodies (AREA)
Abstract
Abstract of the Disclosure An electric band heater of low expansion characteristics having a resistance wire wound element surrounding and embedded in a body of agglomerated densely packed ceramic particles and tightly encased within a metal housing. The invention also relates to a core body for an electric band heater which is formed from a resistance wire element embedded in and sandwiched between ceramic particle sheets, the ceramic particle sheets consisting of strips of heat dissipatable organic material having ceramic particles densely packed therein.
Description
110~560 This invention relates to improvements in electric band or strip heaters, and is more particularly concerned with such heaters of relatively thin configuration and which are fabricated from a novel assembly of organic bound ceramic particle strips sandwiching a resistance wire wound organic-ceramic heater core element. The organic bound ceramic particle strips and organic-ceramic core element consist of flexible sheets of organic material densely packed with ceramic particles wherein the organic material may be dissipated when subjected to heat.
In conventional band heaters of standard mica configuration, a wire wound mica heating element is assembled between mica ins~lator strips.
The resultant mica sandwich is then encased in a sheet metal enclosure and formed into a desired shape. The electrical mica insulators used are of relatively low thermal conductivity and thus limit the heat transfer efficiency. Also, these insulator strips undergo physical and chemical changes upon exposure to temperature in excess of 1200F., which consist of dehydration or baking out of the water of hydration. These changes further decrease thermal conductivity and also reduce electrical insulating proper-ties.
The presence of air voids and undesirable expansion under elevated temperature inherent in conventional mica heaters reduce heat transfer capability and result in loss of heater efficiency. These factors cause a -~ conventional heater to operate at relatively higher than most efficient internal temperatures, resulting in premature heater failure. Additionally, where clamp force must be applied to maintain the heater in a given position, e.g. around a nozzle of a tube having contents which must be heated as they pass therethrough, expansion of the heater under elevated temperatures causes loss of clamping force, resulting in heater inefficiency because the heater must be hotter to achieve a given surface temperature, and the higher temperature of the heater induces further expansion as the temperature is elevated.
In a second type of conventional band heater, coils of element wire are strung through preformed ceramic insulator blocks which are shielded ,. ., --1--,~.
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11~1C~560 by a light sheet metal cover. Such an assembly is then strapped around an object to be heated. The resulting assembly can be likened to an oven assembly wherein heat transfer to the heated object is principally by con-vection rather than conduction. Such a heating system is not capable of high wattage because the inefficient convection heat transfer will not remove heat from the element fast enough, and thus would lead to over-temperaturing of the wire and premature element failure. This limitation of wattage thus increases heat-up time of any object to be heated. Due to the open design of the casing for such conventional ceramic heaters, carbon forming materials can enter the heater, causing grounding type failures, which also may con-; stitute a safety hazard. ~lso inherent bulk and thickness requirements for :.
conventional ceramic heaters prevent their use where space is critical.
In the present invention, during fabrication of the heater, instead of a formed mica core and mica insulations strips as in conventional mica ~i heaters, and instead of preformed blocks strung with wire as in conventional ceramic heaters, a resistance wire element is wound on a core strip of ~ organically bound ceramic particles, and sandwiched between similar organical-;l~ ly bound ceramic particle strips; and the assembly is placed in a metal housing and rolled or pressed to eliminate air voids between the elements, whereupon the entire assembly is heated to bake out the binders and agglomerate the ceramic particles into a densely packed unitary mass embedding therein the heater wire element and the ceramic particles surround all exposed , ~, surfaces of the heater wire element.
These novel organically bound ceramic particle strips each com-prise a thin pliable "green" sheet of ceramic particles, pressed and rolled to a high density, and bonded together with binder materials, usually organic in nature, to an overall thickness upwards of .018 inch. The ceramic particles in the sheets are typical powdered ceramic materials, such as particles of aluminum oxide, magnesium oxide, boron nitride, or silicone dioxide. The binders for the ceramic particle sheets are typically silicone, rubber, varnish, glyptal nr the like. These bonded "green" or unbaked ceramic particle sheets conventionally are used in the fabrication of
In conventional band heaters of standard mica configuration, a wire wound mica heating element is assembled between mica ins~lator strips.
The resultant mica sandwich is then encased in a sheet metal enclosure and formed into a desired shape. The electrical mica insulators used are of relatively low thermal conductivity and thus limit the heat transfer efficiency. Also, these insulator strips undergo physical and chemical changes upon exposure to temperature in excess of 1200F., which consist of dehydration or baking out of the water of hydration. These changes further decrease thermal conductivity and also reduce electrical insulating proper-ties.
The presence of air voids and undesirable expansion under elevated temperature inherent in conventional mica heaters reduce heat transfer capability and result in loss of heater efficiency. These factors cause a -~ conventional heater to operate at relatively higher than most efficient internal temperatures, resulting in premature heater failure. Additionally, where clamp force must be applied to maintain the heater in a given position, e.g. around a nozzle of a tube having contents which must be heated as they pass therethrough, expansion of the heater under elevated temperatures causes loss of clamping force, resulting in heater inefficiency because the heater must be hotter to achieve a given surface temperature, and the higher temperature of the heater induces further expansion as the temperature is elevated.
In a second type of conventional band heater, coils of element wire are strung through preformed ceramic insulator blocks which are shielded ,. ., --1--,~.
.
11~1C~560 by a light sheet metal cover. Such an assembly is then strapped around an object to be heated. The resulting assembly can be likened to an oven assembly wherein heat transfer to the heated object is principally by con-vection rather than conduction. Such a heating system is not capable of high wattage because the inefficient convection heat transfer will not remove heat from the element fast enough, and thus would lead to over-temperaturing of the wire and premature element failure. This limitation of wattage thus increases heat-up time of any object to be heated. Due to the open design of the casing for such conventional ceramic heaters, carbon forming materials can enter the heater, causing grounding type failures, which also may con-; stitute a safety hazard. ~lso inherent bulk and thickness requirements for :.
conventional ceramic heaters prevent their use where space is critical.
In the present invention, during fabrication of the heater, instead of a formed mica core and mica insulations strips as in conventional mica ~i heaters, and instead of preformed blocks strung with wire as in conventional ceramic heaters, a resistance wire element is wound on a core strip of ~ organically bound ceramic particles, and sandwiched between similar organical-;l~ ly bound ceramic particle strips; and the assembly is placed in a metal housing and rolled or pressed to eliminate air voids between the elements, whereupon the entire assembly is heated to bake out the binders and agglomerate the ceramic particles into a densely packed unitary mass embedding therein the heater wire element and the ceramic particles surround all exposed , ~, surfaces of the heater wire element.
These novel organically bound ceramic particle strips each com-prise a thin pliable "green" sheet of ceramic particles, pressed and rolled to a high density, and bonded together with binder materials, usually organic in nature, to an overall thickness upwards of .018 inch. The ceramic particles in the sheets are typical powdered ceramic materials, such as particles of aluminum oxide, magnesium oxide, boron nitride, or silicone dioxide. The binders for the ceramic particle sheets are typically silicone, rubber, varnish, glyptal nr the like. These bonded "green" or unbaked ceramic particle sheets conventionally are used in the fabrication of
-2-~LlQ~S60 ceramic underlayment for printed circuits, the end product when baked out being referred to as "ceramic substrate" but in their "green" state before baking they are pliable and bendable.
In fabricating a heater according to the present invention, a lower organic - ceramic particle strip is laid over the bottom wall of a -metal housing, ~nd the core organic-ceramic particle strip which has been formed with a Nichrome or other resistance wire element, which is placed ~.
over the lower strip. A second or upper organic-ceramic particle insulator strip is placed over the resistance wire element core strip, and a metal pressure plate is installed over the upper strip. The edges of the housing are bent over the pressure plate, and the assembly is then rolled and flattened, thereby eliminating air voids between the elements and amalgamating and unifying the structure.
The assembly may then be shaped, for example, bent into a curved band heater. When the heater assembly is in its final finished shape, it is fired at an elevated temperature above the vaporization point of the binder materials in the strips and below the melting point of the sheath covering, preferably in an oxygen atmosphere, to vaporize and carbonize the binders and oxidize the carbon, which is vented from the heater assembly in the form of carbon dioxide. The assembly may be rolled again to further compact the body. As a result of this process, the ceramic particles agglomerate and are densely packed into a thin integral heat conducting and electrically insulating mass. Leads may then be connected to the heater element terminals and any desired heater mounting members may then be attached.
It is therefore an object of the present invention to provide a novel electric heater assembly of the character referred to.
According to one aspect of the invention there is provided a thin integral ceramic band heater assembly comprising a closed metal housing, a heater core body secured tightly within the housing without air voids, said heater core body comprising a compacted agglomerated mass of unbound ceramic particles electrically insulating and surrounding an electrical resistance llQ~560 .
heater element embedded therein, and leads for connecting the heater element and a source of electric power insulated from and through said housing.
According to another aspect of the invention there is provided a core body for a ceramic band heater assembly comprising a sandwich of aligned sheets of ceramic particles bonded together by vaporizable binders and an electrical resistance heater element arranged between said sheets, said body being adapted to amalgamate into a unitary mass of agglomerated ceramic particles embedding said heater element therein upon application of sufficient heat to vaporize said binders.
According to a further aspect of the invention there is provided in a method for fabricating a unitary electric ceramic band heater comprising the steps of assembling resistance wire on an uncured sheet of ceramic particles impregnated to a high density and bound together in heat dissipat-able binder material, arranging said assembled wire and uncured sheet between uncured sheets of insulator particles bound together in heat dissipatable ~ -binder material, compressing said arranged assembled wire and uncured sheet and said uncured insulator sheets together to substantially eliminate air voids between said sheets, and heating said compressed arranged assembly at a temperature sufficient to substantially dissipate said binder materials and ~ , cure said ceramic and insulator particles into an integral mass.
Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which Figure 1 is a perspective view of a curved ceramic band heater assembly embodying the invention;
Figure 2 is a perspective exploded view of the separated parts of a heater assembly embodying the invention;
Figure 3 is a perspective view of a strip heater assembly embodying the invention;
Figure 4 is a sectional view of assembled parts of the heater before closing the housing and compressing and heating the assembly; and Figure 5 is a sectional view of the heater assembly before com-pression.
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~: : -: ; , , ?S60 With reference to the drawings, a curved band heater 10 (as shown in Figure 1) or a strip heater 11 (as shown in Figure 3) may be fabricated from a sheet metal channel 12 having a flat base 19 and upstanding sides 14, and into the channel is placed, successively, a thin flat pliable insulator sheet 15 of bound ceramic particles, a resistance wire element core 16, a second or upper insulator sheet 17 of bound ceramic particles, and a metal pressure plate 18 may be set thereover, all of which may be held together and centered during initial assembly by means of suitable tape or adhesive.
The margins 29 of the upstanding sides 14 on channel 12 may be bent over the pressure plate 18 to close the assembly and bind the pressure plate thereover. The closed assembly is then rolled flat or is formed into a curved finished shape to compress the parts together and eliminate air voids between the elements, as shown in Figure 5.
Ceramic particle core element strip 16 is formed with Nichrome ; (Trademark) or other resistance wire 20 wound around a sheet of bound ceramic particles similar to the sheets 15 and 17, and the ends of the wire may be bound with terminal pads 21. The pre~sure plate 18 and insulator strips 15 and 17 are of about the same length and width as the base 19, to fit snugly within channel 12, but the core element 16, while about the same length as the base 19, is narrower than the strips 15 and 17, to provide a gap 24 for electrical clearance between the core 16 and its wire winding 20, and the channel sides 14.
The bound ceramic particle insulator sheets 15 and 17 and the ceramic particle core 16 each comprise high density ceramic particles bound together by a binder, usually organic material, which has been fabricated by pressing and rolling the material together. While the strips are green, i.e.
before heating to the vapor point of the binder material and agglomerating and packing of the ceramic particles into a dense mass, the strips are pliable and bendable, but after heating to a temperature above the vapor point of the organic or inorganic binder material and after agglomerating and packing of the ceramic particles, the strips amalgamate into a packed dense mass of ceramic particles to insulate the resistance wire 20 embedded ,, ,-therein, while providing efficient heat transfer and low expansion character-istics when a current is applied to the resistance wire element.
Before heating, the assembly is bendable and formable without damaging the core 16 and insulator strips 15 and 17, so the assembly may be shaped, for example into the configuration of a curved band heater 10, shown in Figure 1, or left in its extended form to be completed as a strip heater 11, shown in Figure 3. After the forming step, the assembly is fired at an elevated temperature, preferably in an oxygen atmosphere, sufficient to , vaporize and bake out the binder materials of the strips 15 and 17 and the binder of core 16 and to agglomerate the ceramic particles, joining them ! together into a single mass. The applied temperature for vaporization ;~ should be less than the melting point of the metal members, so as not to weaken those parts.
Electric leads 25 and 26, respectively, may be connected to each of the terminal pads 21, connecting the heater wires 20 to a power source.
A slight extension 13 may be provided on each edge of the channel to support the lead wires, and the channel edges may be potted with suitable electrical cement 35 to close and finish the connection to the heater assembly.
Means for mounting or clamping the heater assembly to or about a surface to be heated may also be connected to the finished heater assembly.
Such means may comprise a band 27, which may be spot welded to the pressure plate 18, having turned and apertured ends 30, through which apertures a bolt 30 may be inæerted, and clamping may be accomplished by tightening a nut 31 on the bolt.
ll(l~S60 Supplementary Disclosure In the drawings accompanying this Supplementary Disclosure:-Figure 6 is a sectional view of the completed heater assembly;
Figure 7 is a perspective exploded view of the separated parts of a heater assembly similar to Figure 2, except the wire wound heater element consists of a metallic ribbon, Figure 8 is a sectional view of a completed heater assembly having the ribbon heater element shown in Figure 7;
Figure 9 is a detailed schematic view of the ceramic particles before compression;
Figure 10 is a perspective view of a modified seamless housing for the heater assembly.
`~ With reference to the embodiment of the invention shown in Figures -~ 7 and 8, instead of the wire wound core element 16, a flat wire ribbon 36 assembled between the insulator strips 15 and 17 defines the heater core of the assembly. The ends of this wire ribbon 36 may be connected to leads in the manner previously described. 1`he assembly of the heater elements is sub-stantially as described with reference to Figures 2 and 4-6, except, in the case of this embodiment, the insulator strips 15 and 17 surround and embed the ribbon 36 after the members are assembled and compressed and formed, and the binders for the strips 15 and 17 are baked out in the manner previously described.
The ceramic particles 40, which were bound together in the green strip form, are packed into a dense mass during the compression step described, the burning out of the binders leaving these ceramic particles agglomerated. Additional pressing of the mass of ceramic particles 40 makes the agglomeration tighter and even more dense, with a consistency similar to very tightly compressed talc.
Where it is desired that the completed heater assembly have a seamless housing, instead of utilizing a channel 12, the core 16 and insulator strips 15 and 17 are assembled together, with or without a pressure plate 18, and the assembly may be inserted into a flattened tube 42, and then formed, . - ,, compressed and heated in the manner described to complete the ceramic band heater.
Because the ceramic particles 40 are very small, the strips 15 and 17 and the core 16 may be relatively thin and only thick enough to provide adequate electrical insulation without concern for the mechanical limitations of conventional preformed ceramic blocks. The result is a relatively thin completed heater assembly which has superior heat transfer characteristics within minimum space requirements. Also, the structure permits the wire element 20 or 36 to be formed in a wide variety of heater coils engineered primarily for electrical requirements only and without consideration for the . ., ~ mechanical strength of the wire or coil.
:
~'
In fabricating a heater according to the present invention, a lower organic - ceramic particle strip is laid over the bottom wall of a -metal housing, ~nd the core organic-ceramic particle strip which has been formed with a Nichrome or other resistance wire element, which is placed ~.
over the lower strip. A second or upper organic-ceramic particle insulator strip is placed over the resistance wire element core strip, and a metal pressure plate is installed over the upper strip. The edges of the housing are bent over the pressure plate, and the assembly is then rolled and flattened, thereby eliminating air voids between the elements and amalgamating and unifying the structure.
The assembly may then be shaped, for example, bent into a curved band heater. When the heater assembly is in its final finished shape, it is fired at an elevated temperature above the vaporization point of the binder materials in the strips and below the melting point of the sheath covering, preferably in an oxygen atmosphere, to vaporize and carbonize the binders and oxidize the carbon, which is vented from the heater assembly in the form of carbon dioxide. The assembly may be rolled again to further compact the body. As a result of this process, the ceramic particles agglomerate and are densely packed into a thin integral heat conducting and electrically insulating mass. Leads may then be connected to the heater element terminals and any desired heater mounting members may then be attached.
It is therefore an object of the present invention to provide a novel electric heater assembly of the character referred to.
According to one aspect of the invention there is provided a thin integral ceramic band heater assembly comprising a closed metal housing, a heater core body secured tightly within the housing without air voids, said heater core body comprising a compacted agglomerated mass of unbound ceramic particles electrically insulating and surrounding an electrical resistance llQ~560 .
heater element embedded therein, and leads for connecting the heater element and a source of electric power insulated from and through said housing.
According to another aspect of the invention there is provided a core body for a ceramic band heater assembly comprising a sandwich of aligned sheets of ceramic particles bonded together by vaporizable binders and an electrical resistance heater element arranged between said sheets, said body being adapted to amalgamate into a unitary mass of agglomerated ceramic particles embedding said heater element therein upon application of sufficient heat to vaporize said binders.
According to a further aspect of the invention there is provided in a method for fabricating a unitary electric ceramic band heater comprising the steps of assembling resistance wire on an uncured sheet of ceramic particles impregnated to a high density and bound together in heat dissipat-able binder material, arranging said assembled wire and uncured sheet between uncured sheets of insulator particles bound together in heat dissipatable ~ -binder material, compressing said arranged assembled wire and uncured sheet and said uncured insulator sheets together to substantially eliminate air voids between said sheets, and heating said compressed arranged assembly at a temperature sufficient to substantially dissipate said binder materials and ~ , cure said ceramic and insulator particles into an integral mass.
Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which Figure 1 is a perspective view of a curved ceramic band heater assembly embodying the invention;
Figure 2 is a perspective exploded view of the separated parts of a heater assembly embodying the invention;
Figure 3 is a perspective view of a strip heater assembly embodying the invention;
Figure 4 is a sectional view of assembled parts of the heater before closing the housing and compressing and heating the assembly; and Figure 5 is a sectional view of the heater assembly before com-pression.
.
~: : -: ; , , ?S60 With reference to the drawings, a curved band heater 10 (as shown in Figure 1) or a strip heater 11 (as shown in Figure 3) may be fabricated from a sheet metal channel 12 having a flat base 19 and upstanding sides 14, and into the channel is placed, successively, a thin flat pliable insulator sheet 15 of bound ceramic particles, a resistance wire element core 16, a second or upper insulator sheet 17 of bound ceramic particles, and a metal pressure plate 18 may be set thereover, all of which may be held together and centered during initial assembly by means of suitable tape or adhesive.
The margins 29 of the upstanding sides 14 on channel 12 may be bent over the pressure plate 18 to close the assembly and bind the pressure plate thereover. The closed assembly is then rolled flat or is formed into a curved finished shape to compress the parts together and eliminate air voids between the elements, as shown in Figure 5.
Ceramic particle core element strip 16 is formed with Nichrome ; (Trademark) or other resistance wire 20 wound around a sheet of bound ceramic particles similar to the sheets 15 and 17, and the ends of the wire may be bound with terminal pads 21. The pre~sure plate 18 and insulator strips 15 and 17 are of about the same length and width as the base 19, to fit snugly within channel 12, but the core element 16, while about the same length as the base 19, is narrower than the strips 15 and 17, to provide a gap 24 for electrical clearance between the core 16 and its wire winding 20, and the channel sides 14.
The bound ceramic particle insulator sheets 15 and 17 and the ceramic particle core 16 each comprise high density ceramic particles bound together by a binder, usually organic material, which has been fabricated by pressing and rolling the material together. While the strips are green, i.e.
before heating to the vapor point of the binder material and agglomerating and packing of the ceramic particles into a dense mass, the strips are pliable and bendable, but after heating to a temperature above the vapor point of the organic or inorganic binder material and after agglomerating and packing of the ceramic particles, the strips amalgamate into a packed dense mass of ceramic particles to insulate the resistance wire 20 embedded ,, ,-therein, while providing efficient heat transfer and low expansion character-istics when a current is applied to the resistance wire element.
Before heating, the assembly is bendable and formable without damaging the core 16 and insulator strips 15 and 17, so the assembly may be shaped, for example into the configuration of a curved band heater 10, shown in Figure 1, or left in its extended form to be completed as a strip heater 11, shown in Figure 3. After the forming step, the assembly is fired at an elevated temperature, preferably in an oxygen atmosphere, sufficient to , vaporize and bake out the binder materials of the strips 15 and 17 and the binder of core 16 and to agglomerate the ceramic particles, joining them ! together into a single mass. The applied temperature for vaporization ;~ should be less than the melting point of the metal members, so as not to weaken those parts.
Electric leads 25 and 26, respectively, may be connected to each of the terminal pads 21, connecting the heater wires 20 to a power source.
A slight extension 13 may be provided on each edge of the channel to support the lead wires, and the channel edges may be potted with suitable electrical cement 35 to close and finish the connection to the heater assembly.
Means for mounting or clamping the heater assembly to or about a surface to be heated may also be connected to the finished heater assembly.
Such means may comprise a band 27, which may be spot welded to the pressure plate 18, having turned and apertured ends 30, through which apertures a bolt 30 may be inæerted, and clamping may be accomplished by tightening a nut 31 on the bolt.
ll(l~S60 Supplementary Disclosure In the drawings accompanying this Supplementary Disclosure:-Figure 6 is a sectional view of the completed heater assembly;
Figure 7 is a perspective exploded view of the separated parts of a heater assembly similar to Figure 2, except the wire wound heater element consists of a metallic ribbon, Figure 8 is a sectional view of a completed heater assembly having the ribbon heater element shown in Figure 7;
Figure 9 is a detailed schematic view of the ceramic particles before compression;
Figure 10 is a perspective view of a modified seamless housing for the heater assembly.
`~ With reference to the embodiment of the invention shown in Figures -~ 7 and 8, instead of the wire wound core element 16, a flat wire ribbon 36 assembled between the insulator strips 15 and 17 defines the heater core of the assembly. The ends of this wire ribbon 36 may be connected to leads in the manner previously described. 1`he assembly of the heater elements is sub-stantially as described with reference to Figures 2 and 4-6, except, in the case of this embodiment, the insulator strips 15 and 17 surround and embed the ribbon 36 after the members are assembled and compressed and formed, and the binders for the strips 15 and 17 are baked out in the manner previously described.
The ceramic particles 40, which were bound together in the green strip form, are packed into a dense mass during the compression step described, the burning out of the binders leaving these ceramic particles agglomerated. Additional pressing of the mass of ceramic particles 40 makes the agglomeration tighter and even more dense, with a consistency similar to very tightly compressed talc.
Where it is desired that the completed heater assembly have a seamless housing, instead of utilizing a channel 12, the core 16 and insulator strips 15 and 17 are assembled together, with or without a pressure plate 18, and the assembly may be inserted into a flattened tube 42, and then formed, . - ,, compressed and heated in the manner described to complete the ceramic band heater.
Because the ceramic particles 40 are very small, the strips 15 and 17 and the core 16 may be relatively thin and only thick enough to provide adequate electrical insulation without concern for the mechanical limitations of conventional preformed ceramic blocks. The result is a relatively thin completed heater assembly which has superior heat transfer characteristics within minimum space requirements. Also, the structure permits the wire element 20 or 36 to be formed in a wide variety of heater coils engineered primarily for electrical requirements only and without consideration for the . ., ~ mechanical strength of the wire or coil.
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Claims (25)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A thin integral ceramic band heater assembly comprising a closed metal housing, a heater core body secured tightly within the housing without air voids, said heater core body comprising a compacted agglomerated mass of unbound ceramic particles electrically insulating and surrounding an electrical resistance heater element embedded therein, and leads for connect-ing the heater element and a source of electric power insulated from and through said housing.
2. The heater assembly recited in Claim 1, wherein said housing comprises a closed-ended U-shaped channel and a pressure plate arranged over and closing said channel, and said body is snugly engaged within the channel.
3. The heater assembly recited in Claim 2, wherein said channel has a base, upstanding walls and extensions disposed between said walls, and the free ends of said walls are bent over said pressure plate.
4. The heater assembly recited in Claim 3, wherein the leads extend from the ends of said channel and said ends and leads are closed and insulated with electrical cement.
5. The heater assembly recited in Claim 1, wherein said electrical resistance heater element has a terminal pad and a lead is connected to said terminal pad.
6. The heater assembly recited in Claim 1, wherein the entire heater assembly is bent around a radius.
7. The heater assembly recited in Claim 1, wherein said heater element comprises coiled wire.
8. A core body for a ceramic band heater assembly comprising a sand-wich of aligned sheets of ceramic particles bonded together by vaporizable binders and an electrical resistance heater element arranged between said sheets, said body being adapted to amalgamate into a unitary mass of agglomerated ceramic particles embedding said heater element therein upon application of sufficient heat to vaporize said binders.
9. The body recited in Claim 8, wherein said sheets are pliable and bendable before heating.
10. The body recited in Claim 8, wherein said heater element comprises a winding of wire arranged around a sheet of ceramic particles bonded together by vaporizable binders.
11. The body recited in Claim 8, wherein said sheets and element are compressed together without air voids between them.
12. The body recited in Claim 8, wherein a closed housing snugly engages said sheets and heater element.
13. The body recited in Claim 12, wherein said housing comprises a closed-ended U-shaped channel and a pressure plate arranged over and closing said channel.
14. The body recited in Claim 12, wherein the entire core body and housing are rolled and formed in a curved shape and adapted to conform to a curved surface to be heated.
15. In a method for fabricating a unitary electric ceramic band heater comprising the steps of assembling resistance wire on an uncured sheet of ceramic particles impregnated to a high density and bound together in heat dissipatable binder material, arranging said assembled wire and uncured sheet between uncured sheets of insulator particles bound together in heat dissipat-able binder material, compressing said arranged assembled wire and uncured sheet and said uncured insulator sheets together to substantially eliminate air voids between said sheets, and heating said compressed arranged assembly at a temperature sufficient to substantially dissipate said binder materials and cure said ceramic and insulator particles into an integral mass.
16. The method recited in Claim 15, wherein leads for electrically connecting said winding to a source of power are attached to the resistance wire after said assembly is heated.
17. The method recited in Claim 15, wherein said arranged assembly is placed in a housing before the assembly is compressed, and the housing is compressed together with said assembly.
18. The method recited in Claim 17, wherein said housing is closed before said compression step.
19. The method recited in Claim 15, wherein said compressed assembly is formed before it is heated.
20. The method recited in Claim 15, wherein means for mounting the assembly on a selected surface is connected to said assembly after the assembly is compressed and heated.
21. The method recited in Claim 19, wherein said compressed assembly is bent into a curved shape.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
22. The heater assembly recited in Claim 1, wherein said housing comprises a flattened metal tube.
23. The heater assembly recited in Claim 1, wherein said heater element comprises a flat wire ribbon.
24. The body recited in Claim 8, wherein said heater element comprises a flat wire ribbon.
25. The body recited in Claim 12, wherein said housing comprises a flattened tube.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66829276A | 1976-03-18 | 1976-03-18 | |
| US668,292 | 1976-03-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1100560A true CA1100560A (en) | 1981-05-05 |
Family
ID=24681759
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA269,213A Expired CA1100560A (en) | 1976-03-18 | 1977-01-06 | Ceramic band heater and method for making the same |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1100560A (en) |
| GB (3) | GB1583773A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10136474B2 (en) | 2012-07-11 | 2018-11-20 | Eberspacher Catem Gmbh & Co. Kg | Heat generating element |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4698614A (en) * | 1986-04-04 | 1987-10-06 | Emerson Electric Co. | PTC thermal protector |
| ES2103670B1 (en) * | 1994-12-27 | 1998-05-01 | Nugar Bobinajes Sl | ELECTRIC RESISTANCE. |
| EP2017103B1 (en) * | 2007-07-18 | 2016-05-04 | Eberspächer catem GmbH & Co. KG | Electric heating device |
| EP2395295B1 (en) * | 2010-06-11 | 2013-03-06 | Behr GmbH & Co. KG | Heat exchanger |
| EP2395296B1 (en) * | 2010-06-11 | 2016-04-27 | MAHLE Behr GmbH & Co. KG | Heat exchanger |
| CN112189904A (en) * | 2020-11-03 | 2021-01-08 | 深圳睿蚁科技有限公司 | Durable heating wire and preparation process thereof |
| GB2618837A (en) * | 2022-05-19 | 2023-11-22 | Finar Module Sagl | enclosure for a power resistor assembly |
-
1977
- 1977-01-06 CA CA269,213A patent/CA1100560A/en not_active Expired
- 1977-03-18 GB GB4236579A patent/GB1583773A/en not_active Expired
- 1977-03-18 GB GB433877A patent/GB1583771A/en not_active Expired
- 1977-03-18 GB GB3999579A patent/GB1583772A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10136474B2 (en) | 2012-07-11 | 2018-11-20 | Eberspacher Catem Gmbh & Co. Kg | Heat generating element |
Also Published As
| Publication number | Publication date |
|---|---|
| GB1583773A (en) | 1981-02-04 |
| GB1583771A (en) | 1981-02-04 |
| GB1583772A (en) | 1981-02-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |