CA2120825C - Electric heater with ceramic resistor - Google Patents
Electric heater with ceramic resistorInfo
- Publication number
- CA2120825C CA2120825C CA002120825A CA2120825A CA2120825C CA 2120825 C CA2120825 C CA 2120825C CA 002120825 A CA002120825 A CA 002120825A CA 2120825 A CA2120825 A CA 2120825A CA 2120825 C CA2120825 C CA 2120825C
- Authority
- CA
- Canada
- Prior art keywords
- radiators
- radiator
- ceramic
- heater according
- heater
- 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 - Fee Related
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
- H05B3/02—Details
Landscapes
- Resistance Heating (AREA)
Abstract
A heater is described in which a plurality of heating elements made of ceramic resistors with positive temperature coefficient are arranged in series to form several parallel rows. A plurality of wave radiators with good electric and thermal conductivity are adhered to two sides of each row of the ceramic resistors by means of adhesive applied on a contact plate provided at one side of each radiator.
With the adhesive, the heating elements and the radiators can be conveniently and firmly assembled to form a heating unit and any voids left between the ceramic resistors and the radiators can be filled up to secure good electrical and thermal conduction therebetween. Furthermore, two heat-resistant cushions made of rubber material are separately clamped and compressed between two outer sides of the assembled heating unit and a corresponding fixing member attached thereto to absorb deformation of the heating unit due to any expansion or contraction caused by temperature and to serve as an electrical and thermal insulation.
With the adhesive, the heating elements and the radiators can be conveniently and firmly assembled to form a heating unit and any voids left between the ceramic resistors and the radiators can be filled up to secure good electrical and thermal conduction therebetween. Furthermore, two heat-resistant cushions made of rubber material are separately clamped and compressed between two outer sides of the assembled heating unit and a corresponding fixing member attached thereto to absorb deformation of the heating unit due to any expansion or contraction caused by temperature and to serve as an electrical and thermal insulation.
Description
1~/3~ 2 5 ELECTRIC HEATER WITH CERAMIC RESISTOR
FIELD OF TEIE INVENTION
The present invention relates to a heater mainly used on appliances such as warmers, driers, etc. that need electrothermal energy. More particularly, it relates to a heater which a ceramic resistor with a positive temperature coefficient (PTC) is used as its heating element, and in which an adhesive is used to connect the heating elements and the radiators in a more convenient rnanner. Ileat-resisting rubber cushions are used to press upon two sides of the assembled heating elements and radiators to maintain a substantially rigid assembly, and to provide the improved heat conduction.
A heater with a similar structure has been disclosed in US Patent No. 5,057,672, in WhiC~I ceramic resistors with Pl'C are used as the heating elements and conductive radiators are used to conduct the heat generated by the heating element.
Ilowever, all the ceramic resistors wi~h Prc in these heaters are disposed on a frame which is formed with a plurality of slots to accommodate each ceramic resistor. Io addition, leaf springs are used to press against two sides of the assembled and colllpleted heater. 'Ihe disadvantages of such arrangement are as follows.
1. ~To assemble the heater, the ceramic reslstors with PTC must first be placed in the slots on the frame one by one. Then, each frame with the ceramic resistors with PTC must be sandwiched between two radiators to form a heating unit.
, .~ 1 -212082~
-Normally, at least three rows of ceramic resistors with PTC
are required to form a heating unit, and therefore, these assembly steps must be repeated at least three times.
Finally, outer frames and side frames, as well as leaf springs are used to enclose the assembled heating units. Such an assembly method is time and labour consuming.
FIELD OF TEIE INVENTION
The present invention relates to a heater mainly used on appliances such as warmers, driers, etc. that need electrothermal energy. More particularly, it relates to a heater which a ceramic resistor with a positive temperature coefficient (PTC) is used as its heating element, and in which an adhesive is used to connect the heating elements and the radiators in a more convenient rnanner. Ileat-resisting rubber cushions are used to press upon two sides of the assembled heating elements and radiators to maintain a substantially rigid assembly, and to provide the improved heat conduction.
A heater with a similar structure has been disclosed in US Patent No. 5,057,672, in WhiC~I ceramic resistors with Pl'C are used as the heating elements and conductive radiators are used to conduct the heat generated by the heating element.
Ilowever, all the ceramic resistors wi~h Prc in these heaters are disposed on a frame which is formed with a plurality of slots to accommodate each ceramic resistor. Io addition, leaf springs are used to press against two sides of the assembled and colllpleted heater. 'Ihe disadvantages of such arrangement are as follows.
1. ~To assemble the heater, the ceramic reslstors with PTC must first be placed in the slots on the frame one by one. Then, each frame with the ceramic resistors with PTC must be sandwiched between two radiators to form a heating unit.
, .~ 1 -212082~
-Normally, at least three rows of ceramic resistors with PTC
are required to form a heating unit, and therefore, these assembly steps must be repeated at least three times.
Finally, outer frames and side frames, as well as leaf springs are used to enclose the assembled heating units. Such an assembly method is time and labour consuming.
2. The surfaces of both the ceramic resistors with PTC and the radiators must be highly smooth so that every ceramic resistor may completely and closely contact the adjacent radiator. This requires a high fabrication cost to create the required highly smooth surfaces.
3. It is also required that every component of the heating unit has highly accurate dimensions with low errors so that the assembly thereof can meet the requirement of accuracy. This also increases the manufacturing cost.
4. When the assembled heating unit is carelessly dropped, the components thereof tend to part from one another easily.
5. The plastic frames tend to have bubbles and pores formed during the course of injection moulding and are therefore apt to break at such bubbles or pores. When such a condition happens, the ceramic resistors with PTC immediately separate from the frame due to insufficient contact between the ceramic resistors and the frame or the radiators. When this happens, the electrical and thermal conduction of the heater is immediately adversely affected.
6. Since both the side frames and the leaf springs are made of metallic material, current passing through the radiators will easily flow through the side frames, too. In addition, metallic material has higher thermal conductivity which will cause transfer of heat energy generated by the heater to the side frames. Such a heater is, therefore, not practical in use for the industrial field.
It is therefore desirable to have a heater in which the heating elements and the radiators are assembled in a more convenient and safer manner.
The heater according to the present invention, in one embodiment, consists of a plurality of heating elements made of ceramic resistors with PTC arranged in series to form several parallel rows, and a plurality of heat radiators with good electric and thermal conductivity adhered to two sides of each row of the heating elements by means of adhesive applied on a contact plate provided at one side of every radiator.
With the adhesive, the heating elements and the radiators can be conveniently and firmly assembled to form a heating unit and any gaps left between the heating elements and the radiators can be filled up to maximize the electric and thermal conduction of the heater. In addition, two heat-resistant or thermally insulating cushions made of rubber CA 0212082~ 1998-06-1~
material are separately disposed between a lateral fixing member of the heater and two outer sides of the assembled heating unit to serve as an electric and thermal insulator.
In its broadest embodiment, this invention provides an electrical resistance heater comprising in combination at least one ceramic resistor having a positive temperature coefficient and at least one heat radiator having good electrical conductivity, and having a surface bonded to a face of the ceramic resistor by means of a substantially continuous film of electrically and thermally conductive adhesive disposed between the ceramic resistor face and the electrically conductive radiator and an insulant at the ends of the radiator.
Preferably, both the face of the ceramic resistor, and the surface of the radiator, are substantially flat.
Preferably, the at least one ceramic resistor has two faces, which are both substantially flat and substantially parallel to each other, and which are bonded between two radiator surfaces. More preferably, a plurality of ceramic resistors are bonded end to end in a row between two elongate radiator surfaces. Most preferably, the heater comprises a plurality of rows of ceramic resistors and a plurality of radiators, wherein each elongate radiator has two surfaces, which are substantially flat and substantially parallel, and wherein each row of ceramic resistors is bonded between two radiator surfaces.
CA 0212082~ 1998-06-1~
In a preferred embodiment, each row of ceramic resistors is of the same length.
The invention will be described by way of reference to the attached figures, in which:
Fig. 1 shows the basic structure of the present invention, that is, a ceramic resistor with PTC sandwiched between two radiators;
2120~25 .
Fig. 1-1 is an enlarged and fragmentary view showing the manner in which the ceramic resistor and the radiators are adhered together;
Fig. 2 is an exploded perspective of a heater according to the present invention;
Fig. 3 is an assembled perspective of the heater of Fig. 2; and Figs. 4A and 4B show the structure of a conventional heater.
Referring first to Figures 4A and 4B, the structure of a conventional heater is shown. All of the ceramic resistors with PTC are disposed in a frame 7 which is formed with a plurality of slots 71 each of which accommodate a ceramic resistor 70. Each frame 7 with ceramic resistors 70 is sandwiched between two radiators 8a and 8b, to form a heating unit. Outer frames 9 and side frames 90, as well as leaf springs 91, are used to enclose and press together the assembled heating unit.
One embodiment of a heater according to this invention is shown in Figures 1, 1-1, 2 and 3. As shown, in Figures 1 and 1-1, the heater consists of a plurality of heating elements 1. Each heating element 1 is a ceramic resistor with PTC and has a flat rectangular configuration.
CA 0212082~ 1998-06-1~
The heating element 1 has two side faces lA, lB, both of which are heated to a constant temperature when there is current passing through the heating element 1. The constant temperature is set in accordance with known methods, based on the nature of the usage proposed at the time the heating element 1 is manufactured. To conduct the current properly, each heating element 1 is sandwiched between two radiators 2A, 2B so that the latter are in close contact with the ceramic resistor side faces lA, lB, respectively. The radiators 2A, 2B may be made of aluminium material and each has attached to it a plurality of continuously formed wave-like ribs 21 to provide excellent electric and thermal conductivity. When there is current passing through the heating element 1, the heating element 1 is heated, and the heat energy so generated by the heating element 1 is conducted to and dissipated by the ribs 21.
A plurality of heating elements 1 are arranged in series to form several rows, and radiators 2A, 2B are disposed at two sides of each row of the serial heating elements 1 such that an elongate contact plate 22 provided at one side of each radiator 2A, 2B contacts a side face lA, lB of each of the heating elements 1, respectively. Before assembly, adhesive is applied to each contact plate 22 on the surface which will be in contact with the side face lA, lB
of the heating element 1, as shown in Fig. 1-1, so that the radiators 2A, 2B are closely and tightly adhered to the two sides of the heating elements 1.
The assembled rows of alternating heating elements and 212~825 radiators form a plane heating unit 4, as shown in Fig. 3.
The a&esive 20 is so applied that a thin film is formed on the contact plates 22. After the radiators 2A, 2B and the heating elements 1 are assembled together, they are further compressed relative to one another before the adhesive 20 has completely dried, i.e. whilst it is still in a fluid state, so that the adhesive 20 is evenly spread over the contact interface between the heating elements 1 and the radiators 2A, 2B under the compression. From Fig. 1-1, which is an enlarged fragmentary view, it can be seen that both the contact plates 22 and the heating elements 1 have uneven surfaces, having a plurality of indents 202 and protuberances 201 thereon. When the adhesive 20 is spread under compression, it will flow into and fill up the indents 202. The protuberances 201 provide electrical contact between the ceramic resistors and the radiators, thus permitting current to flow between the heating elements 1 and the radiators 2A, 2B. The indents 202 filled with adhesive 20 permit thermal conduction between the heating elements 1 and radiators 2A, 2B with a thermal conduction efficiency better than that conventionally provided by air present in similar gaps between the heating elements and the radiators. Therefore, the heater of the present invention provides both improved thermal conduction efficiency and more even transfer of heat. Since the adhesive 20 may be effectively applied to the corresponding interfaces of the heating elements 1 and the contact plate 22 of the radiators 2A, 2B in an evenly spread manner to form an even film which may fill up any vacancy left between the interfaces due to any 2l2ns2s deformation of the heating elements 1 and/or the contact plates 22, the conductive property of the ceramic resistors with PTC forming the heating elements 1 can be efficiently utilised. Covers 3 are used to cover the top and bottom ends of the plane heating unit 4. Terminals 41 are provided at and projecting from the ends of the radiators 2A, 2B, and extend through holes in the covers 3. Suitable electrical leads are connected to these terminals for the input of current to the heating elements 1.
Channel-shaped fixing members 5A, 5B are provided on the two lateral sides of the plane heating unit 4. Hooks 51 provided at two ends of the fixing members 5A, 5B, engage with and are firmly locked in corresponding apertures in the covers 3 (not shown in Fig. 2). In addition, a heat-resistant cushions 5 made of synthetic rubber having a U-shaped cross section are disposed between the fixing members 5A, 5B and the outer radiators 2A, 2B, respectively, with is U-shaped opening 50 facing outward to urge the assembly of heaters and radiators together, and to enhance the tight, close, and even contact of every contact plate 22 with the heating elements 1 thereby enabling heat to be evenly transferred between them.
These cushions also serve to accommodate any thermal expansion and contraction of the heater during use. Since the rubber cushions 5 are made of electrically insulating material, the fixing members 5A, 5B are thereby insulated from electric current and therefore are safe for touching by a user's hands.
The rubber cushions 5 also have a thermal insulation effect 212~825 and the fixing members 5A, 5B are thereby protected from being heated to an undesirable extent. This makes the assembled heater more suitable for applications in the industrial field.
With the above elements and combination thereof, a complete heater is formed.
To facilitate the efficient dissipation of heat generated by the heater, an electric blower 6 may be provided behind the heater.
It is therefore desirable to have a heater in which the heating elements and the radiators are assembled in a more convenient and safer manner.
The heater according to the present invention, in one embodiment, consists of a plurality of heating elements made of ceramic resistors with PTC arranged in series to form several parallel rows, and a plurality of heat radiators with good electric and thermal conductivity adhered to two sides of each row of the heating elements by means of adhesive applied on a contact plate provided at one side of every radiator.
With the adhesive, the heating elements and the radiators can be conveniently and firmly assembled to form a heating unit and any gaps left between the heating elements and the radiators can be filled up to maximize the electric and thermal conduction of the heater. In addition, two heat-resistant or thermally insulating cushions made of rubber CA 0212082~ 1998-06-1~
material are separately disposed between a lateral fixing member of the heater and two outer sides of the assembled heating unit to serve as an electric and thermal insulator.
In its broadest embodiment, this invention provides an electrical resistance heater comprising in combination at least one ceramic resistor having a positive temperature coefficient and at least one heat radiator having good electrical conductivity, and having a surface bonded to a face of the ceramic resistor by means of a substantially continuous film of electrically and thermally conductive adhesive disposed between the ceramic resistor face and the electrically conductive radiator and an insulant at the ends of the radiator.
Preferably, both the face of the ceramic resistor, and the surface of the radiator, are substantially flat.
Preferably, the at least one ceramic resistor has two faces, which are both substantially flat and substantially parallel to each other, and which are bonded between two radiator surfaces. More preferably, a plurality of ceramic resistors are bonded end to end in a row between two elongate radiator surfaces. Most preferably, the heater comprises a plurality of rows of ceramic resistors and a plurality of radiators, wherein each elongate radiator has two surfaces, which are substantially flat and substantially parallel, and wherein each row of ceramic resistors is bonded between two radiator surfaces.
CA 0212082~ 1998-06-1~
In a preferred embodiment, each row of ceramic resistors is of the same length.
The invention will be described by way of reference to the attached figures, in which:
Fig. 1 shows the basic structure of the present invention, that is, a ceramic resistor with PTC sandwiched between two radiators;
2120~25 .
Fig. 1-1 is an enlarged and fragmentary view showing the manner in which the ceramic resistor and the radiators are adhered together;
Fig. 2 is an exploded perspective of a heater according to the present invention;
Fig. 3 is an assembled perspective of the heater of Fig. 2; and Figs. 4A and 4B show the structure of a conventional heater.
Referring first to Figures 4A and 4B, the structure of a conventional heater is shown. All of the ceramic resistors with PTC are disposed in a frame 7 which is formed with a plurality of slots 71 each of which accommodate a ceramic resistor 70. Each frame 7 with ceramic resistors 70 is sandwiched between two radiators 8a and 8b, to form a heating unit. Outer frames 9 and side frames 90, as well as leaf springs 91, are used to enclose and press together the assembled heating unit.
One embodiment of a heater according to this invention is shown in Figures 1, 1-1, 2 and 3. As shown, in Figures 1 and 1-1, the heater consists of a plurality of heating elements 1. Each heating element 1 is a ceramic resistor with PTC and has a flat rectangular configuration.
CA 0212082~ 1998-06-1~
The heating element 1 has two side faces lA, lB, both of which are heated to a constant temperature when there is current passing through the heating element 1. The constant temperature is set in accordance with known methods, based on the nature of the usage proposed at the time the heating element 1 is manufactured. To conduct the current properly, each heating element 1 is sandwiched between two radiators 2A, 2B so that the latter are in close contact with the ceramic resistor side faces lA, lB, respectively. The radiators 2A, 2B may be made of aluminium material and each has attached to it a plurality of continuously formed wave-like ribs 21 to provide excellent electric and thermal conductivity. When there is current passing through the heating element 1, the heating element 1 is heated, and the heat energy so generated by the heating element 1 is conducted to and dissipated by the ribs 21.
A plurality of heating elements 1 are arranged in series to form several rows, and radiators 2A, 2B are disposed at two sides of each row of the serial heating elements 1 such that an elongate contact plate 22 provided at one side of each radiator 2A, 2B contacts a side face lA, lB of each of the heating elements 1, respectively. Before assembly, adhesive is applied to each contact plate 22 on the surface which will be in contact with the side face lA, lB
of the heating element 1, as shown in Fig. 1-1, so that the radiators 2A, 2B are closely and tightly adhered to the two sides of the heating elements 1.
The assembled rows of alternating heating elements and 212~825 radiators form a plane heating unit 4, as shown in Fig. 3.
The a&esive 20 is so applied that a thin film is formed on the contact plates 22. After the radiators 2A, 2B and the heating elements 1 are assembled together, they are further compressed relative to one another before the adhesive 20 has completely dried, i.e. whilst it is still in a fluid state, so that the adhesive 20 is evenly spread over the contact interface between the heating elements 1 and the radiators 2A, 2B under the compression. From Fig. 1-1, which is an enlarged fragmentary view, it can be seen that both the contact plates 22 and the heating elements 1 have uneven surfaces, having a plurality of indents 202 and protuberances 201 thereon. When the adhesive 20 is spread under compression, it will flow into and fill up the indents 202. The protuberances 201 provide electrical contact between the ceramic resistors and the radiators, thus permitting current to flow between the heating elements 1 and the radiators 2A, 2B. The indents 202 filled with adhesive 20 permit thermal conduction between the heating elements 1 and radiators 2A, 2B with a thermal conduction efficiency better than that conventionally provided by air present in similar gaps between the heating elements and the radiators. Therefore, the heater of the present invention provides both improved thermal conduction efficiency and more even transfer of heat. Since the adhesive 20 may be effectively applied to the corresponding interfaces of the heating elements 1 and the contact plate 22 of the radiators 2A, 2B in an evenly spread manner to form an even film which may fill up any vacancy left between the interfaces due to any 2l2ns2s deformation of the heating elements 1 and/or the contact plates 22, the conductive property of the ceramic resistors with PTC forming the heating elements 1 can be efficiently utilised. Covers 3 are used to cover the top and bottom ends of the plane heating unit 4. Terminals 41 are provided at and projecting from the ends of the radiators 2A, 2B, and extend through holes in the covers 3. Suitable electrical leads are connected to these terminals for the input of current to the heating elements 1.
Channel-shaped fixing members 5A, 5B are provided on the two lateral sides of the plane heating unit 4. Hooks 51 provided at two ends of the fixing members 5A, 5B, engage with and are firmly locked in corresponding apertures in the covers 3 (not shown in Fig. 2). In addition, a heat-resistant cushions 5 made of synthetic rubber having a U-shaped cross section are disposed between the fixing members 5A, 5B and the outer radiators 2A, 2B, respectively, with is U-shaped opening 50 facing outward to urge the assembly of heaters and radiators together, and to enhance the tight, close, and even contact of every contact plate 22 with the heating elements 1 thereby enabling heat to be evenly transferred between them.
These cushions also serve to accommodate any thermal expansion and contraction of the heater during use. Since the rubber cushions 5 are made of electrically insulating material, the fixing members 5A, 5B are thereby insulated from electric current and therefore are safe for touching by a user's hands.
The rubber cushions 5 also have a thermal insulation effect 212~825 and the fixing members 5A, 5B are thereby protected from being heated to an undesirable extent. This makes the assembled heater more suitable for applications in the industrial field.
With the above elements and combination thereof, a complete heater is formed.
To facilitate the efficient dissipation of heat generated by the heater, an electric blower 6 may be provided behind the heater.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrical resistance heater comprising in combination at least one ceramic resistor having a positive temperature coefficient and at least one heat radiator having good electrical conductivity, and having a surface bonded to a face of the ceramic resistor by means of a substantially continuous film of electrically and thermally conductive adhesive disposed between the ceramic resistor face and the electrically conductive radiator and an insulant at the ends of the radiator.
2. A heater according to Claim 1 wherein both the face of the ceramic resistor, and the surface of the radiator, are substantially flat.
3. A heater according to Claim 1 wherein the at least one ceramic resistor has two faces, which are both substantially flat and substantially parallel to each other, and which are bonded between two radiator surfaces.
4. A heater according to Claim 3 wherein a plurality of ceramic resistors are bonded end to end in a row between two elongate substantially flat radiator surfaces.
5. A heater according to Claim 4 comprising a plurality of rows of ceramic resistors and a plurality of radiators, wherein each elongate radiator has two surfaces, which are substantially flat and substantially parallel, and wherein each row of ceramic resistors is bonded between two radiator surfaces.
.
.
6. A heater according to Claim 3 wherein the radiators also provide electrical connection to the at least one ceramic resistors.
7. A heater according to Claim 5 wherein the radiators also provide electrical connection to the ceramic resistors.
8. A heater according to Claim 5 wherein each row of ceramic resistors is of the same length.
9. A heater according to Claim 5 further including cover members located across the ends of the radiators, attached to fixing members disposed adjacent the end radiators, and wherein said insulant is a heat and electrical insulant cushion members between the end radiators and the adjacent fixing members, so that when assembled the fixing members compress the cushion members against the adjacent radiators.
10. A heater according to Claim 9 wherein the cushion members are fabricated from a synthetic rubber material.
11. A heater according to Claim 1 or 2 wherein the radiator comprises an elongate contact plate in contact with the adhesive, and which has attached to it a plurality of wave-like ribs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002120825A CA2120825C (en) | 1994-04-07 | 1994-04-07 | Electric heater with ceramic resistor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002120825A CA2120825C (en) | 1994-04-07 | 1994-04-07 | Electric heater with ceramic resistor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2120825A1 CA2120825A1 (en) | 1995-10-08 |
| CA2120825C true CA2120825C (en) | 1998-11-17 |
Family
ID=4153329
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002120825A Expired - Fee Related CA2120825C (en) | 1994-04-07 | 1994-04-07 | Electric heater with ceramic resistor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2120825C (en) |
-
1994
- 1994-04-07 CA CA002120825A patent/CA2120825C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2120825A1 (en) | 1995-10-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |