MXPA00004366A - Quartz substrate heater - Google Patents

Abstract

An electric, resistance element heater utilizes quartz as a sheath material and has a resistance (heating) element that is in intimate, substantially continuous contact with a surface of the quartz. This allows the heater to operate in any one or all of the three modes of heat transfer, namely, radiation, conduction and convection. Such intimate, substantially continuous contact of the resistance element is achieved by applying the element in direct contact with the quartz surface. This is accomplished by applying a heating circuit directly to the quartz surface, which heating element can be a foil element, or a thick or a thin film deposition element. The overall heater is formed by covering the heater element by a quartz sheath and attaching leads formed on the ends of the heater element to a source of electric energy. Sensors such as thermocouples, RTD's and the like can also be incorporated directly into the heater structure. Also, the heater can be fashioned into a variety of shapes.

Description

HEATER WITH QUARTZ SUBSTRATE Field of the Invention The present invention relates to electric heaters and, more particularly, to electric resistance heaters that use one or more quartz substrates.

Background of the Invention It is known that there are three types or forms of heat transfer, which are conduction, convection and radiation. All electric resistance heaters use one of these forms of heat transfer to supply heat to the surrounding environment. In general, electric resistance heaters have a heat generating element (e.g., a resistance wire) that couples to a source of electrical energy. When electrical power is supplied to the resistance wire, the wire will be heated due to its resistance. The amount of heat produced by the resistance wire is a factor of the material and shape of the wire and the voltage, current and / or frequency of the electrical power supplied to it. REF .: 120049 In general, in electric resistance heaters, the resistance wire is surrounded and / or minimally in contact with a coating material. The coating material also contributes to the operating characteristics of the heater.

It is also known to have electric heaters that use quartz for the external coating material, although quartz is considerably more expensive to use compared to the coating materials of common heaters such as metals or ceramics. There are several reasons to use quartz, which include: 1. Quartz can resist use at high temperature. 2. Quartz is relatively transparent to infrared energy which allows the heat generating element inside the quartz to radiate heat directly from the element to the process or be charged with small quartz temperature rise. 3. Quartz is considered to be one of the few acceptable materials for the use in environments or processes such as ultra pure semiconductor processing, e.g. heating of deionized water. 4. Quartz has a low coefficient of thermal expansion that inherently gives the ability to overcome significant thermal shock and temperature excursions without fracturing.

. Quartz has reasonably good resistance to corrosion when exposed to many chemicals and deionized water. 6. Quartz is typically a vitrio material fused with very small molecular spacing. In this way it is possible to manufacture sealed heaters that do not "aspirate" or allow aminant e s. to 1 around them to penetrate through these and attack the heating element, nor allow the materials to be released by the heating element from contaminating the process or the surrounding environment.

However, while there are known electrical resistance heaters that use quartz as the external coating material, the configuration of such prior art heaters, in general, dictates that they function as radiation heaters (in the form of heat transfer radiation). ) and not as convective or conductive heaters (respectively the convective form of heat transfer and the conductive form of heat transfer). This situation exists because the quartz heaters of the prior art do not substantially heat the quartz itself as it is required to be present for the type of heating by convection and conduction. As such, the prior art electrical resistance quartz heaters do not take advantage of the many characteristics of quartz as a coating material and thus, do not operate as conductive convection heaters. This limits the scope of applications in which the heater could be used.

In U.S. Pat. 3,047,702 entitled Píate Heater, presented by F.L. Lefebvre on July 31, 1962, a plate heater utilizing quartz is described. A resistance element formed as a coil is retained against a surface of a quartz plate, so that the portions of the coil are in contact therebetween. However, because the majority of the heating surface of the propellers of the resistive coil is not in contact with the quartz, there is little heating of the quartz. Instead of transferring heat to the quartz plate, the heating coil heats the surrounding medium. In this way, the plate heater 702 generally only operates in a form of radiation heat transfer which makes the heater more efficient and / or limits its use to lower temperature heating applications.

In U.S. Pat. 4,531,047 entitled Clip-Mounted Quartz tube Electric Heater, presented by Canfield et al. on July 23, 1985, an electric heater is described which includes a quartz tube having a heating coil therein. The heating coil is supported by a ceramic support that extends the length of the coil and is formed with a heat reflecting groove. The small arched portions of each helix of the heating coil are in contact with the inner surface of the quartz tube. The 047 patent recognizes that the quartz heaters of the prior art such as the Lefebvre 702 patent were deficient as indicated above, and in this way try to mitigate the deficiencies by adding a supported heat reflecting member to concentrate the heat produced inside the tube by the heating coil.

From the above point of view, it is an object of the present invention to provide a more efficient quartz heater.

It is another object of the present invention to provide a quartz heater that can operate in any of all three forms of heat transfer.

It is still another object of the present invention to provide an electric resistance element type heater having a quartz coating, wherein the quartz coating delivers heat in the form of heat transfer by convection or conduction.

Brief Description of the Invention The present invention is an electrical resistance heater having a quartz substrate / coating that allows the heater to be used in any of the three forms of heat transfer; radiation, convection and conduction.

The foregoing is carried out in the present invention by having the electric heating element in continuous contact, intimate with the substrate / quartz coating. Preferably, the electric heating element is applied directly to the substrate / coating and covered by another substrate / quartz coating. This forms a laminated structure.

In one form thereof, the heater comprises a laminated structure having a first quartz substrate on which an electric heating element is directly disposed, and a second quartz substrate covering the exposed heating element. This method allows the use of the heater in the forms of heat transfer by conduction and convection, which depends on the intimate contact between the electric heating element and the quartz. This results in a lower element temperature that allows densities of higher energies. Being thus heated, the outer quartz surfaces provide the heat to the process and / or the charge in the heat transfer forms by convection and conduction.

In one form thereof, the laminated structure is formed of a first quartz substrate, cut to the desired shape, on which is disposed an electric heating circuit of engraved metal foil of a given pattern, and a second substrate of quartz, complementary placed on the heating element. The electric heating element is laminated / superposed between the two quartz substrates, with the two quartz substrates permanently bonded to one another to maintain the laminated structure together by a welding process, a specially formulated sealing glass such as the one made by Vitta Glass Co., or another process. The fusion of the two quartz substrates could be either continuous or discontinuous depending on whether or not the finished heater needs to be sealed from the environment in which it will be used.

In another form, the laminated structure is formed of a first quartz substrate, cut to the desired shape, on which a conductive or resistive ink is stencilled, whereby the heating element is formed. The printed circuit is made using special conductive inks manufactured by companies such as Electro Science Laboratories. Stencilled ink (circuits of electric heaters) is then cured through an ionization / agglomeration process. After curing, a second substrate is placed on the heating circuit and is bonded in the same manner as described above with respect to the engraved metal foil heating element.

In yet another form thereof, the laminated structure is formed by depositing a thin conductive film on a first quartz substrate using a thin film deposition process such as ionic etching, chemical vapor deposition or the like. Again, a second quartz substrate is attached on the electric heating circuit and on the first quartz substrate. ' Conductors or terminals are provided in the heating element to which the external energy conductors are attached, already before fusing, if the conductors are external to the laminated structure or after fusing, if the conductors are external to the laminated structure.

Applying the principles of the present invention, it should be readily understood that quartz substrates could take any form such as a tube, tank, polygonal or the like. The electrical circuits can be mounted or applied to the interior and / or exterior surfaces of the quartz substrates. Depending on the application and the shape, the thick film, thin film or foil circuits can be used as the heating element. Other types of heating elements may be used if they are applied according to the principles of the present invention.

Detectors, such as thermocouples or RTDs can also be included within the heater assemblies. The detectors and their related circuits could be supported alone, stamped stamps or thin film components or laminations included in the manufacturing process. Also, it is possible to have multiple substrates with circuits applied to multiple surfaces of such substrates.

Brief Description of the Drawings The features, advantages and other objects mentioned above and others of the present invention, and the manner in which they are obtained, will become more apparent and will be better understood with reference to the detailed description in conjunction with the accompanying drawings which continue, in which: Fig. 1 is a top plan view of a quartz substrate with a heating element thereon in accordance with the principles of the present invention; Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1; Fig. 2A is a cross-sectional view taken along line 2A-2A of Fig. 1; Fig. 3 is a perspective view of the structure of the laminated quartz heater according to the principles of the present invention; Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 3; Fig. 5 is a top plane view of an alternative embodiment of a quartz substrate with the heating element therein in accordance with the principles of the present invention; Fig. 6 is an isometric view of the present invention applied to a tubular quartz substrate; and Fig. 7 is a cross-sectional view taken along line 7-7 of Fig. 6.

Detailed description of the invention With reference now to Figs. 1 and 2, a quartz substrate 10 is shown, in a generally disk-like manner. It should be absolutely clear and understood that the substrate could take on substantially any shape or design as may be modeled from the quartz so long as the principles of the present invention are followed as set forth in this specification. In this way, the quartz substrate 10, instead of being disk-shaped, could be tubular (as in Figs 6 and 7), spherical, polygonal or any other shape in which the quartz could be modeled. In addition, the substrate 10 shown in Figs. 1 and 2 is only a portion of the overall heater coating, but is shown to illustrate the electric heating element in relation to the substrate An electrical resistance heating element 12 is directly disposed on an upper or first surface 11 of the quartz substrate 10., which, as seen in Fig. 2, has a lower side or surface 13 that is substantially continuously in direct contact with the upper surface 11 of the quartz substrate 10. Maximizing the contact of the surface area between the surface of the substrate and the heating element, maximum heat transfer is achieved. The shape of the heating element 12 is a way of designing considerations that depend on the output of the heater. In Fig. 1, the heating element 12 is formed in a sinuous pattern on the upper surface of the quartz substrate. The heating element 12 terminates at the end in the conductors or terminations 15, 16 and is adapted to be connected to an electric current conductor for the application of electrical energy in a known manner, for controlling the heating. The conductors (not shown) could be welded, joined, by brass welding or mechanically joined to the terminations 15, 16 as is well known in the electric heaters of the art.

The maximum, continuous and intimate contact is best accomplished by the use of a flat heating element 12 as shown in the Figures. A flat heating element has very thin side surfaces compared to the upper and lower surfaces thereof and thus, in accordance with the principles defined herein, is a form of the ideal heating element, although other forms could be used, including, those with curved surfaces. The thickness of the flat heating element is exaggerated in the Figures to better demonstrate the configuration thereof.

A flat heating element is obtained by various methods, having a surface in intimate and substantially continuous contact with the surface of the quartz substrate. A first method for forming the heating element is to use a metal foil electric heating circuit such as metal foil electric circuits as are known in the heater industry, which is placed directly on a surface of a quartz substrate preferably the previous form. The metal sheet circuit could be formed by etching, stamping, perforating, cutting or similar processes by known processes.

A second method for forming the heating element is to use a thin film deposition material, such as resistive or electrically conductive inks printed by spreading directly on the surface of the quartz substrate.

Such spill-printed resistive and conductive inks that function as heated resistors are obtained through various companies such as Electro Science Laboratories. In general, with thick film inks, the circuits must be completely cured by an ionization / agglomeration process.

The thick film could also be deposited by banding, printing or painting, whereby the film is placed on an intermediate substrate io - and dried appropriately. The film is subsequently transferred to the white quartz substrate and cured to form a thick electrically conductive film circuit.

A third method is to form a thin film heating element by a thin film deposition process, such as ionic ion picking, chemical vapor deposition, ion implantation or other thin film deposition process.

Another heater structure is represented in the Figs. 3 and 4, and the attention now goes to these figures. Because of the full capabilities, the present heater is optimized by having the surface area of the heating element in direct contact with the quartz substrate, a heater structure 20 preferably consists of a superposed assembly. A first quartz substrate 22 has a heating element 24 disposed therein in accordance with the present principles, so that a lower surface 25 thereof is in intimate or adjunct, substantially continuous contact. A second quartz substrate, preferably complementary in shape 26, is disposed on and on an upper surface 27 of the heating element 24. The upper surface 27 of the heating element 24 is in intimate contact or substantially continuous adjoining with the surface of the second substrate. quartz 26 The second quartz substrate 26 is clamped on the first quartz substrate 22 and then preferably permanently bonded together with crossover / coupling area 23 either by a welding process or through the use of a specially formulated sealing glass, such as the facts of Vitta Glass Company, for which a structure assembly of the heater / lamination is formed. The coupling area 23 is represented by a line in Figure 3 for clarity, however in reality the two substrates 22, 26 are homogeneous after bonding, and therefore, the coupling area 23 is not visible to the naked eye . The substrates 22, 26 could also be coupled by fusing, joining, or other similar means. However, it should be understood that the coupling of the two quartz substrates could be continuous or not depend on whether or not the finished heater needs to be hermetically sealed from the environment in which it will be used. The two substrates could also be pre-charged to effect a compressive force that further enhances intimate contact between the substrate and the circuit.

Fig. 5 depicts an alternative embodiment of the present invention, wherein the quartz substrate 30 is square. The electric heating element 32 is again arranged directly on a surface 31 of the substrate, so that a maximum surface area of one side of the heating element is in intimate, substantially continuous contact with the surface 31. The heating element has the terminations 34 , 36 again for connection to external electrical conductors.

Of course, the substrate 30 and the heating element 32 is covered by a second quartz substrate in the manner described above to complete the structure of the heater Figs, 6 and 7 show another heater 40 incorporating the concepts of the present invention in a quartz substrate tube 42. This embodiment is particularly useful in applications such as heating deionized water, which would flow through the hollow opening 44 of the quartz tube 42. Again, the heating element 46 is shown with an exaggerated thickness to better demonstrate the configuration thereof. Fig. 6 also shows an alternative configuration for the terminations 48, 50, which here are formed as bands around the ends of the quartz tube 42, thereby minimizing any required orientation of the heater 40 when coupled to a power source electric It should also be understood that the quartz coating, and thus the respective quartz substrates comprising the quartz coating, could be fabricated only about any size with the electrical circuits mounted or applied on the interior and / or exterior of the surfaces of the same. This would be dependent on the application of the heater and other design considerations.

Also, it would be possible and within the scope of this description to provide detectors in the heater structures. Such detectors could be thermocouples, RTDs and the like. The detectors and their related circuits could be supported alone, stamped, deposited by thin film or the like. In addition, various heating elements or circuits could be arranged on simple substrates and controlled separately or together.

Therefore, while this invention is described with reference to a preferred embodiment of the invention, it is not intended to be constructed in a limited sense. It is better to cover any variation, uses or adaptations in the invention that use its general principles. Various modifications will be apparent to people in the art with reference to this description. It is therefore contemplated that the appended claims and any other claims will cover any such modifications or modalities that fall within the scope of the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (37)

1. A heater, characterized in that it comprises: a first quartz substrate defining at least one surface of the first substrate; a heating element defining a surface of the first element and a surface of the second element, the surface of the first element in intimate contact, substantially continuous with the surface of the first substrate, the heating element has conductors adapted to be connected to a source of electrical energy; Y a second quartz substrate defining, at least, a surface of the second substrate, the surface of the second substrate in intimate contact, substantially continuous with the surface of the second element.

2. The heater of claim 1, characterized in that the first quartz substrate is joined to the second quartz substrate.

3. The heater of claim 2, characterized in that the first quartz substrate is joined to the second quartz substrate by welding.

4. The heater of claim 2, characterized in that the first quartz substrate is joined to the second quartz substrate by melting.

5. The heater of claim 4, characterized in that the first quartz substrate is joined to the second quartz substrate by bonding.

6. The heater of claim 1, characterized in that the heating element is a metal foil circuit.

7. The heater of claim 1, characterized in that the heating element is a thick film deposition element.

8. The heater of claim 1, characterized in that the heating element is a thin film deposition element.

9. An electric heater, characterized in that it comprises: a quartz substrate having a quartz contact surface area; Y a resistance heating element having a surface contact area of the element and terminations, the resistance heating element is disposed over the quartz contact surface area, so that the contact surface area of the element is in contact with With substantially continuous adhesion to the quartz contact area, the terminations are adapted to receive energy from an external electrical power source.

10. The electric heater of claim 9, characterized in that it further comprises: a second quartz substrate having a second quartz contact surface area; wherein the resistance heating element has a second surface contact area of the element, the second contact surface area of the contact element of substantially continuous adhesion with the second quartz contact area.

11. The electric heater of claim 10, characterized in that the second quartz substrate is joined to the first quartz substrate by welding.

12. The electric heater of claim 10, characterized in that the second quartz substrate is joined to the first quartz substrate by melting.

13. The electric heater of claim 10, characterized in that the second quartz substrate is joined to the first quartz substrate by bonding.

14. The electric heater of claim 9, characterized in that the resistance heating element is a metal foil circuit.

15. The electric heater of the reign indication 9, characterized in that the resistance heating element is a thick film deposition element.

16. The electric heater of claim 9, characterized in that the resistance heating element is a thin film deposition element.

17. The electric heater of claim 9, characterized in that the resistance heating element is a flat conduit.

18. A laminated structure of the heater, characterized in that it comprises: a first quartz substrate a second quartz substrate; Y an electrical resistance heating element having a first surface area, a second surface area and a third surface area, the first contact surface area of substantially continuous adhesion with the first quartz substrate, the second surface area in substantially continuous adhesion contact with the second quartz substrate; wherein the first and second surface areas are substantially greater than the third surface area.

19. The laminate structure of the heater of claim 18, characterized in that the first and second quartz substrates are joined together.

20. The laminate structure of the heater of claim 19, characterized in that the second quartz substrate is joined to the first quartz substrate by welding.

21. The laminate structure of the heater of claim 19, characterized in that the second quartz substrate is joined to the first quartz substrate by melting.

22. The laminate structure of the heater of claim 19, characterized in that the second quartz substrate is bonded to the first quartz substrate by bonding.

23. The laminate structure of the heater of claim 18, characterized in that the electric resistance heating element is a leaf circuit

24. The laminate structure of the heater of claim 18, characterized in that the electric resistance heating element is a thick film deposition circuit.

25. The laminate structure of the heater of claim 18, characterized in that the electric resistance heater element is a thin film deposition circuit.

26. A method for forming a heater, characterized in that it comprises: provide a first quartz substrate; Y placing an electric heating element on the first quartz substrate such that a substantial portion of a first contact area of the electric heating element is in adhesion contact with the first quartz substrate.

27. The method of claim 26, characterized in that it further comprises the steps of: provide a second quartz substrate; Y joining the second quartz substrate to the first quartz substrate, so that a substantial portion of a second contact area of the electric heating element is in adhesion contact with the second quartz substrate

28. The method of claim 27, characterized in that the electric heating element is a metal foil circuit.

29. The method of claim 28, characterized in that the metal sheet circuit is formed by a process of the group consisting of: engraving, perforating, stamping and cutting.

30. The method of claim 27, characterized in that the electric heating element is a thick film deposition circuit.

31. The method of claim 30, characterized in that the thick film circuit is applied to the quartz substrates by a process of the group consisting of: printing, web, transfer and painting.

32. The method of claim 27, characterized in that the electric heating element is a thin film deposition circuit.

33. The rei indication method 32, characterized in that, the thin film circuit is applied to the quartz substrates by a process of the group consisting of: elect roatomized ion, vapor deposition and ion implantation.

34. The method of claim 27, characterized in that the second quartz substrate is joined to the first quartz substrate by welding.

35. The method of claim 27, characterized in that the second quartz substrate is joined to the first quartz substrate by melting.

36. The rei indication method 27, characterized in that the second quartz substrate is attached to the first quartz substrate by bonding.

37. The method of claim 26, characterized in that the heating element is applied to the quartz substrate in a continuous process, and further comprises the step of cutting the substrate to a desired length.