JP2662616B2 - Double-sided heater - Google Patents

Abstract

A dual plate heater (2) provides two parallel temperature self-regulating heater plates (6, 8) or wire mesh comprising ferromagnetic material with one or more electrically energized coils (4) parallel to and located between the heater plates (6, 8) which coil(s) (4) when energized by a constant current (14) or by an otherwise controlled current heat the plates to their Curie temperature or temperatures. The coil may be a flat spiral of thin conductive (copper) wire (4) embedded in a thin layer of a heat conductive, electrically non-conductive material (14) between said plates whereby heat energy generated in the coil is supplied to the heater plates (6, 8). The dual plate heater (2) may be employed to heat plastic pipes (Fig. 14) to their butt welding temperatures after which the heater is removed and the ends of the pipes to be joined are brought into contact under pressure. The dual plate heaters may also be employed in other arrangements such as shelves (Fig. 15) in a dispensing machine.

Description

Detailed Description of the Invention Related Application This application is a continuation-in-part of application Ser. No. 07 / 780,977, filed Oct. 23, 1991, entitled "Two Sided Heaters."

BACKGROUND OF THE INVENTION The present invention relates to a self-regulating two-sided heater, in particular,
The present invention relates to a heater having opposed surfaces that are self-regulated to the same or different temperatures for multiple purposes, including butt welding of plastic pipes, shelf heaters of vending machines, and the like.

In butt welding of plastic pipes, the pipe ends are each heated to the melting temperature by a cartridge type heater, but since this heat heats the entire housing,
Extremely inefficient. This problem is exacerbated when the housing is large and made of aluminum because the entire heating is considerable. Also, this device is very heavy and difficult to use. Furthermore, the temperature distribution of this device is not good and long heating and cooling times are required.

In the field of vending machines, the food to be heated is removed from the machine and heated in a microwave oven or other type of oven. If food such as soup is packed in a metal can and microwaves are used, the food is removed from the can and placed on a non-metallic dish and heated. At lunch, a long line in front of the microwave oven waits for a turn to heat your food.

OBJECT OF THE INVENTION An object of the present invention is to provide a two-sided heater using one pancake induction coil or two independently excited pancake induction coils to heat two parallel ferromagnetic members to the Curie temperature. To provide.

Another object of the invention is to be lightweight, relatively small,
It is to provide a structure for heating two parallel plates that is physically easy to manage.

Yet another object of the present invention is to provide a dual plate heater in which each plate or each assembled plate can be easily replaced with a different temperature plate.

It is yet another object of the present invention to provide a dual plate heater that provides significant heat only to the area of each plate having a thermal load.

Yet another object of the invention is to provide a dual plate heated by induced current from one, two or more electric coils.
It is to provide a heater.

Yet another object of the present invention is to provide a dual plate heater for use in butt welding plastic pipes, in which substantially no heat is transmitted to the support, so that the heating and cooling time is considerably shorter than that of a conventional heater. To provide.

It is yet another object of the present invention to provide a dual plate heater for use as a heating or cooking shelf in a vending machine.

SUMMARY OF THE INVENTION The present invention preferably comprises two substantially parallel ferromagnetic plates, having the same or unequal Curie temperatures, selected according to the temperature at which each load is heated, between the plates. They consist of at least one, preferably pancake coil, located parallel to the plate, so that when the coil is excited by a high-frequency current, the plate is heated to approximately the respective Curie temperature.

The heater excites the heater until the plates reach their respective Curie temperatures, then removes the heater, butts the end of the joining pipe against the plate and applies the appropriate axial pressure to complete the weld. While joining the pipe ends, it can be used for pad welding of plastic pipes.

Various configurations of coil structures and coil heater plate structures are described herein. According to one configuration, a round wire is embedded in a thermally and electrically insulating material, and a heater plate is provided on each side of the insulator. It has been found that as a result of the thermal insulation, the coil temperature is much higher than the plate temperature and the life of the coil is shortened unless the entire operation is completed quickly before the coil becomes hot. If rapid heating, which is not always possible, is not obtained, the final temperature of the coil is always the same with constant power.
It takes longer to get there, but you can get there anyway. Cooling may be used to control the temperature of the coil.

In a preferred embodiment of the present invention, a flat body made of a thermally conductive material is disposed between the heater plate and the coil to provide a good thermal path therebetween. The heat of the plate is transferred to the load, and as long as the temperature of the coil is higher than the temperature of the plate, heat energy is transferred from the coil through the thermally conductive material to the plate. In practice, the temperature required to melt the end of the plastic pipe is between 500 ° F and 600 ° F.
It would be $ F. Copper and the like can withstand this temperature. Therefore, placing the coil thermally and physically close to the plate improves flux transfer and, importantly, the thermal energy of the coil (loss I ² R) is such that the coil temperature is higher than the plate temperature When it is transmitted to the plate. The coil should be designed to minimize thermal energy, but as long as heat is generated, it is used in a shape suitable for heating the plate. It has been found that flat wound coils generate less heat than flat wound coils and that the temperature of the coil is maintained at an allowable temperature higher than the plate temperature.

The current optimum coil has been found to be formed of a highly conductive copper, for example, an alloy of copper 110 having a rectangular cross section of 0.3 inches wide and 0.062 inches thick. The coil has a space between turns of 0.1
It is wound 7 times and 3/4 in flat spirals as inches. The coil is currently used with an approximately 1/8 thick heater plate having 15 mils of alloy 42-6 on both sides of an aluminum alloy 1100 plate. The diameter of the coil and plate are approximately the same, the diameter of the coil is about 8.4 inches, and the pitch is approximately 0.4 inches.

A thermally conductive electrically insulating compound must be used between the coil and the plate. Otherwise, the compound will short the coil. However, this material must be very thin, for example, about 0.15 inches, and must have good heat transfer capabilities. One such material is based on magnesium oxide and is sold under the model number 906 by Coatronics Corp. This material has a thermal conductivity of 40 BTU in / hr'F.

The double plate heater is used, for example, as a cooking shelf or a heating shelf of a vending machine for heating a product from above and below. When a product is requested, a specific area of the plate is heated for a certain period of time, then the heating is stopped, and finally the product is discharged.

In yet another embodiment of the present invention, a ferromagnetic material in the form of a mesh wire is used so that the heater can be deformed into various shapes, for example, bendable to connect a saddle valve to a pipe. The wire is heated by alternating current or induction flowing through it.

One or two coils may be used. Also, the coil is used with two plates having different Curie temperatures if each plate needs to be heated to a different temperature.

As used herein, the term "Curie temperature" refers to the temperature at which a plate loses sufficient ferromagnetism at which heating decreases and cooling begins. This phenomenon can be detected by several well-known methods and occurs between 1 ° C. and 100 ° C. below the absolute Curie temperature, depending on the ferromagnet used.

As used herein, the term "ferromagnetic material" includes conductive ferromagnetic materials, ferrimagnetic materials, ferrites, and other materials that lose much of their magnetic permeability at a certain temperature.

The use of a constant current power supply results in a seed of effective heating. The current is P = I ² R. If the current is constant, I ² = K,
P = KR. As the Curie temperature is approached, flux coupling to the plate is greatly reduced, eddy currents and hysteresis losses in the plate are reduced, and the temperature is reduced until the material is again effective ferromagnetic and heating is continued. In this regard, see U.S. Patent No. 4,256,945. Other methods of controlling heating as a function of Curie temperature are described in U.S. Pat.Reissue No. 33,644 and U.S. Pat.No. 4,795,886, which discloses a preferred method of controlling the Curie temperature of an apparatus according to the present invention. I have.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a basic embodiment of the present invention.

FIG. 2 is a schematic diagram showing magnetic flux coupling from a coil to a heater plate.

3a-f are perspective views of heater plates of various shapes.

 FIG. 4 is a sectional view of a conventional heater structure.

FIG. 5 is a sectional view of an embodiment of the double-layer coil of the present invention.

FIG. 6 is a cross-sectional view of a double-layer coil in which two layers are separated by an insulating layer.

FIG. 7 is a circuit diagram in which two coils are connected in parallel to each plate.

FIG. 8 is a circuit diagram in which two coils, one for each plate, are connected in series.

FIG. 9 is a sectional view of an embodiment including coils connected in parallel.

FIG. 10 is a cross-sectional view of coils connected in parallel separated by a layer of ferrite material.

FIG. 11 is a cross-sectional view of a single double-layer coil in which two layers are separated by a ferrite material.

FIG. 12 is a cross-sectional view of two coils separated in parallel by an insulating layer and connected in parallel.

FIG. 13 is a perspective view of a practical tool incorporating a heater according to the present invention.

FIG. 14 is a perspective view of the utility tool of FIG. 13 being used to heat the end of the pipe to be butt welded.

FIG. 15 is a schematic perspective view of an apparatus using a double plate heater as a shelf.

FIG. 16 is a perspective view of a heater using a net mesh instead of a solid plate.

 FIG. 17 is a perspective view of a modification of the heater of FIG.

FIG. 18 is a schematic diagram of a sandwich structure of a heater coil and a heater plate according to a preferred embodiment of the present invention.

FIG. 19 is a perspective view of a coil used in the embodiment of FIG.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, there is shown a basic configuration of the present invention. The heater 2 has a flat coil 4 formed of a litz wire, a conductive tube, or the like, located between the plates 6 and 8 made of a refractory material. In the illustrated embodiment, the coil is embedded in an epoxy-based material, foam, or other similar material for various purposes, such as insulating from the plate, separating the coil, holding the coil in place, and the like. Heater plate, especially
The ferromagnetic plates 10, 12 are arranged in contact with the refractory materials 6, 8 to complete the simplest basic configuration. The surfaces of the plates 10, 12 may be provided with a Teflon coating 17, 19 to eliminate stickiness. Also, metals 13 and 15 having high thermal conductivity such as copper and aluminum may be provided between the plates 10 and 12 and the Teflon coating. When a conductive tube is used as a coil material, it may be hollow and cooled with air, water, or the like.

When connecting the coil 4 to a high frequency source or a constant current source as shown in reissued U.S. Pat. No. 33,644 or U.S. Pat. No. 4,795,886, indicated at 14, a radio frequency (RF) power supply, 14, plate 1 while generating eddy current and hysteresis loss to generate heat in the plate,
Generate a discontinuous or continuous alternating electromagnetic field linking 12 (see FIG. 2). When the Curie temperature is reached, plate 10,
The energy transfer to 12 is greatly reduced and the plate disappears faster than it produces heat and cools again until it becomes an effective ferromagnet and the heat production is above the heat dissipation level. This action is almost instantaneous, and a normal temperature state is maintained.

Plates 10 and 12 are round, C-shaped, rectangular, cup-shaped,
The shape is determined to be a desired shape such as an L-shape, and the shape is determined according to the expected use condition of the heater. See Figures 3a-f.

Referring to FIG. 4, the coil 4 to be structurally strong is made of a ceramic material or a cast material (such as aluminum).
A conventional heater embedded in the housing 14 is shown. Preferred embodiments of conventional heaters include cal rods (Ca
lrod) A heater is used.

The main advantage of a double layer coil, i.e. two separate coil layers preferably connected in parallel but connected in series, is that two heater plates with different Curie temperatures can be used. In such a situation, a single-layer coil may be used, but when one of the plates reaches the Curie temperature, the magnetic flux mainly couples to the other plate and affects the temperature control. Interaction between them is inevitable.

A certain degree of decoupling is achieved by using multilayer coils, especially those having an insulating layer between the layers. The use of ferrite material between the layers of the coil provides additional decoupling and improves the temperature control of high Curie temperature plates. The use of two separate coils connected in series requires a performanc
Although e) is improved, the best results are obtained with two coils connected in parallel with a ferrite material between the coils. In such a case, complete separation of the two loads is achieved, especially if the power supply is not overloaded by simultaneous loading on the two coils.

The above situation also applies when the Curie temperatures of the two plates are the same and the heat loads are substantially different. In such a case, it is desirable that one plate reach the Curie temperature before the other plate to avoid plate interaction.

Referring to FIG. 5, the coil 16 is provided for the reasons described above.
It is also wound in two layers to provide additional energy to the heater, especially to provide greater flux concentration to the plate.

In FIG. 6, an insulator 18 is placed between the two coils 20 to achieve some decoupling between them. FIG.
Insulator 18 reduces cross-coupling of coil magnetic flux,
This configuration is more efficient than the configuration of FIG. In the configuration of FIG. 5, a magnetic field extinguishing effect occurs due to the mutual approach of the two coils, which makes the configuration of FIG. 6 more efficient.

The coil is wound as two separate coils connected in parallel or in series, but the parallel configuration provides more energy to the device than the series and provides additional decoupling. As mentioned above, the side-by-side configuration is particularly beneficial when the two plates have different Curie temperatures. When a single coil or two series coils are configured in this manner, interaction occurs between the coils, that is, they affect each other, so that the temperature control of the single coil is poorer than that of the parallel connection coil. While a single coil or series coil configuration is satisfactory under these circumstances, a parallel connection coil configuration is preferred.

The circuit of the parallel structure device is shown in FIG. 7, and the circuit of the series structure device is shown in FIG.

The configuration of the double-layer coil connected in parallel is shown in FIG. The first coil 22 is connected between the leads 24, 26, and the second coil 28 is connected across the leads 30, 32. Lead wires 24 and 32 are lead wire sources
The leads 26, 30 are connected to a lead source 36 while being connected to 34.

The configuration shown in FIG. 10 is basically the same as that of FIG. 9 except that the coil concentration is increased in the heater plates 40, 42 to achieve a higher magnetic flux concentration than when using the plate.
The difference is that a ferrite plate 38 is provided between 22 and 28. With ferrite, the magnetic flux from the coil is adequately shielded from the coil on the other side of the ferrite, and the device achieves optimal shielding of the coils and plates of each embodiment.

Referring to FIG. 11, the two-layer single coil 40 has a ferrite layer.
With layers separated by 42.

FIG. 12 shows dual coils 44, 46 separated by an insulating layer 48 and connected in parallel.

FIG. 13 shows a practical embodiment of the present invention. Apparatus 61 includes a dual plate heater 50 mounted to housing 52. The housing 62 is a long arm that terminates at the handle 56
Has 54. The housing may have inclined plates 58, 60 for supporting the structure used to heat the pipe to be melted. The surfaces of the inclined plates 58, 60 may be coated with a thermal insulator to reduce heat conduction to adjacent members.

The device 61 mentioned in the description of FIG. 13 is shown in FIG. The overall device 62 includes a pair of parallel rails 64, 66 separated by the distance between the inclined plates 58, 60 of FIG. When the device of FIG. 13 is operated with the handle 56, the device is positioned between the rails and the inclined plates 58, 60
On 66. The heater plate is heated to the Curie temperature by the excitation of the coil and the butt-welded pipe 6
8, 70 contact both plates of the double plate heater. Once the two plates have reached the Curie temperature, the pipe is brought into contact with the plates and heated to the melting temperature,
The device 61 is removed and the heated pipe ends are butted and pressed together until welded.

Rails 64, to help properly align the pipe with the heater plate and then the pipe itself
Between the 66, pipe positioning devices 72, 74 may be arranged. The distance between devices 72 and 74 should be sufficient to allow the insertion of a double plate heater.

Referring to FIG. 15, there is shown an apparatus in which a product to be heated is located between shelf shelves of a container. Shelves 80, 82 and 84
Are double plate heaters. The load 86 to be heated is located between the shelves 80, 82, and the heat load 88
Are distributed between the shelves 82.

Each shelf is a double plate heater of any type shown in FIGS. 1, 4-12, wherein the bottom of shelf 80 and the top of shelf 82 preferably have the same Curie temperature. Similarly Shelf 82
And the top of shelf 84 preferably have the same Curie temperature.

As the product is heated, the plate in contact with the desired product is excited. The shelf has a heating area at a fixed location, and the goods are brought into contact with the heating area as they are heated prior to discharge or use. Alternatively, the shelf is made of a ferromagnetic material, and has a plurality of heating regions formed by individual coils connected to a power source when the shelf is rotated to the discharge position when the shelf is rotated. You may.

Referring to FIG. 16, there is illustrated a heater utilizing a ferromagnetic mesh embedded in a strong, non-magnetic, thermally conductive plastic such as carbon fiber or liquid crystal material. There are two advantages of such a configuration. The wire mesh acts as a heater and a ferromagnetic member, and has flexibility. It can be formed into virtually any shape and can be easily reused to fuse the saddle valve to plastic pipes and other irregular or irregular shapes.

The basic idea of this heater is shown in FIG. 16 and has a ferromagnetic cross line 90 and a ferromagnetic vertical line 92. These wires are braided and the mesh is made of a continuous wire that is heated by passing an electric current through the leads 94, 96 described above. These wires may be formed of a conductive material coated with a ferromagnetic material to improve Curie temperature control. One for two heater surfaces
Two such members are used each,
The member includes lines 90 'and 92'.

Alternatively, the wires may be heated by a high frequency magnetic field, in which case the wires need not be insulated from each other. Any of the coil structures of FIGS. 1, 2 and 5 to 11 may be used. Such a device is shown in FIG.

Referring to FIG. 17, wires 90 and 90 'are
4 is disposed adjacent to the surfaces 98 and 100 of the member 102 containing the 4. The coil is embedded in a non-thermally conductive plastic so as not to interfere with the Curie point control reaction of the mesh.

With further reference to FIGS. 18 and 19, various preferred embodiments of the present invention are illustrated.

In this embodiment, the unitary heater coil 106 is preferably gripped between two heater plates 108,110. Thermally conductive and electrically insulating potting material layer 11
2 is provided between the coil and each plate. In commercial units, the ends of the elements are coated with a material 112 to add mechanical strength.

The coil is a 8.4 inch unit with 7 turns and 3/4 flat spiral (FIG. 19). The wraps described above are formed about 0.30 inches apart using 110 copper pieces of 0.3 × 0.062 inches. The performance of the combination of coil and one plate is shown in Table I below.

Note that the coil and plate are initially at the same temperature. When current is applied to the coil, the plate is rapidly heated by the effect of the magnetic flux of the ferromagnetic plate. After some time, in this case 5.5 minutes, the plate temperature automatically adjusts between about 489'-490'F, but at 4.5 minutes the coil temperature exceeds the plate temperature. Because the heat dissipation from the exposed and loaded plate is more rapid than from the buried coil, the coil temperature in this case is much lower than the coil wire can tolerate.
Settles to about 535'F. Thus, by using a thermally conductive potting compound, the coil temperature is above the plate temperature, pumping heat to the plate and then to the load, and stabilizing at acceptable levels.

The cooling time of the heater plate and coil is shown in Table II below.

To pot the coil, the coil cools at a lower rate than the plate. The values in this table were obtained using a coil with 9 turns and an extra 1.24 turn in the center, and therefore had little effect on the results.

The coil may be formed by laser etching, or may be formed by winding a wire of a desired end face as described above to reduce cost. In the latter case, the wire to be wound and the spacer wire are sandwiched between starter tools and wound around this tool. After winding, the spacer wire is removed.

It has been found that spacer wires of constant width, ie, diameter, are not suitable because the outer part of the spiral is easier to unravel than the inner part. In order to make the space between the number of turns evenly 0.10 inch, use a 0.068 inch wire for the innermost winding,
It's too big for outside winding. A 28 inch long 0.068 inch inside diameter wire was used for the inner winding, and a 0.068 inch long wire was used with a 50 inch long 0.053 inch inside diameter wire. It would be desirable to do the following: That is, 0.068 inch wire is 2
Use 8 inches followed by 28 inches of 0.053 inch wire, then use 0.040 inch wire without spacer wire for the last few turns. The innermost radius of the coil is about 0.832 inches.

Once disclosed, many other features, changes and modifications will be apparent to those skilled in the art, which are considered to be within the scope of the invention as set forth in the following claims.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Finnegan, Joel Dee United States 94555 California, Fremont, Bodkin Terrace 34334 (56) References JP-A-62-227584 (JP, A) US Patent 4,0081,118 (US, A)

Claims (23)

(57) [Claims] 1. A two-sided heater, comprising: a first ferromagnetic member; a second ferromagnetic member; and a first ferromagnetic member, wherein the first ferromagnetic member is located between the first and second ferromagnetic members. At least one coil having energy sufficient to self-regulate near each Curie temperature, said first and second ferromagnetic members and said at least one coil.
A two-sided heater in which two coils are arranged almost parallel to each other and configured as a single unit. 2. The two-sided heater according to claim 1, wherein said coil is a single-layer pancake coil. 3. The two-sided heater according to claim 1, wherein said coil is a multilayer pancake coil. 4. The apparatus according to claim 1, wherein a plurality of physically independent coils are provided between said first and second ferromagnetic members.
A two-sided heater according to item 1. 5. The two-sided heater according to claim 4, wherein said physically independent coils are connected in series. 6. The two-sided heater according to claim 4, wherein said physically independent coils are connected in parallel. 7. The two-sided heater according to claim 4, further comprising an electric insulating material located between said plurality of coils. 8. A two-sided heater according to claim 7, wherein said electrical insulation comprises a thin layer of a thermally conductive material. 9. The two-sided heater of claim 4, wherein said plurality of coils comprise flat spirals of thin conductive material. 10. The two-sided heater of claim 1 wherein said coil comprises a flat spiral of thin conductive material. 11. The two-sided heater according to claim 4, further comprising a ferrite material layer located between said plurality of coils. 12. The two-sided heater according to claim 1, wherein said first and second ferromagnetic members comprise a pair of ferromagnetic plates, and said coil is located between said plates. 13. A two-sided heater according to claim 1, wherein each of said first and second ferromagnetic members comprises a flexible wire mesh embedded in a non-magnetic, thermally conductive material. 14. A flexible wire, wherein each of said first and second ferromagnetic members is embedded in a non-magnetic, non-thermally conductive material.
The two-sided heater according to claim 1, comprising a mesh. 15. A two-sided heater according to claim 1, and a frame for supporting the two-sided heater, wherein the frame is in contact with the surface of the heater when the frame supports the heater. A two-sided heater structure including a long arm extending in one direction in parallel and a handle provided at an end of the arm. 16. The two-sided heater according to claim 1, wherein the two-sided heater has a heater surface facing in opposite directions, and heating the two sides of the two-sided heater to a predetermined temperature; Moving to each surface; and keeping the pipe in contact with the heater surface until the pipe reaches the welding temperature; removing the two-sided heater and pressing the heated ends of the pipe together. Contacting the pipes until welding is completed. A butt welding method for a plastic pipe, comprising: 17. A shelf comprising at least a pair of two-sided heaters according to claim 12 in a vending machine, wherein the opposed surfaces of said at least one pair of shelves have substantially the same Curie temperature, and are heated. Is disposed between the at least one pair of shelves, and the opposed surfaces of the shelves are heated by generated heat. 18. The two-sided heater according to claim 1, wherein said coil is excited by a constant current AC power supply. 19. The two-sided heater according to claim 1, a pair of parallel rails, and the heater can be removed between the rails in a state where the heater surface is orthogonal to the length direction of the rail. Means for supporting a welded pipe extending parallel to said rail, and a pipe support disposed along the axis of said pipe, the structure for heat welding plastic pipes. body. 20. A ferromagnetic first flexible wire structure; a ferromagnetic second flexible wire structure; and a non-magnetic structure. A second wire structure supported in the non-magnetic structure as providing a separate heat source on a generally oppositely oriented surface of the non-magnetic structure; The first and second wire structures for generating or flowing current through the first and second wire structures to heat the first and second wire structures to at least a temperature close to the Curie temperature A two-sided heater, further comprising means for connecting to a power supply. 21. A ferromagnetic first flexible wire structure; a ferromagnetic second flexible wire structure; and a non-magnetic structure. A second wire structure supported in the non-magnetic structure as providing a separate heat source on a generally oppositely oriented surface of the non-magnetic structure; A two-sided heater, further comprising means for heating the first and second wire structures to their respective Curie temperatures, wherein said means for generating an alternating magnetic flux connecting said first and second flexible wire structures. 22. The non-magnetic material is heat conductive.
Or the two-sided heater according to 21. 23. The non-magnetic material is non-thermally conductive.
22. The two-sided heater according to 20 or 21.