Claims
- 1. A vacuum-molded electrical heating unit comprised of a resistance heating coil embedded in a ceramic-fiber body, the interior of said coil being substantially free of ceramic fiber, said unit being prepared by the process comprising:
- placing said coil on a sieve-like tray, in a frame above a suction box,
- introducing a slip into the frame, said slip being composed of a slurry of ceramic fibers, a binder and water,
- applying suction by way of said suction box whereby said body builds up and is cured, thereby containing the resistance heating coil as an embedded heating element, wherein portions of the surface of the sieve-like tray which lie beneath the resistance heating coil are impervious, and are narrower than one of the group of maximum diameter and width of the heating coil in a plane parallel with the sieve-like tray, whereby the space inside the heating coil remains substantially free of fiber material during the vacuum-molding operation.
- 2. The electrical heating unit of claim 1, wherein, in a preliminary operation, strips are placed on the sieve-like tray, at the positions of the heating coil, before the latter is inserted.
- 3. The electrical heating unit of claim 2, wherein the strips are attached to the heating coil, on the side which is to face the sieve-like tray, their attachment being adhesive and easily releasable.
- 4. The electrical heating unit of claim 2, wherein the strips comprise spacing strips possessing a thickness of 0.1-30 mm.
- 5. The electrical heating unit of claim 4, wherein the sieve-like tray is not perforated in those portions of the surface which lie beneath the heating coil.
- 6. The electrical heating unit of claim 4, wherein said strips possess the thickness of 2-10 mm.
- 7. The electrical heating unit of claim 1, wherein said coil is recessed into the interior of said body, said coil having a radiating surface zone which is exposed by an opening in said body.
- 8. The electrical heating unit of claim 7, wherein the distance from said exposed radiating surface to the opposite end of said opening is between 0.1 and 30 mm.
- 9. The electrical heating unit of claim 1, wherein said coil has an eliptical cross-section.
- 10. The electrical heating unit of claim 1, wherein said coil has a round cross-section.
- 11. The electrical heating unit of claim 1, wherein said coil has a rectangular cross-section.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3233181 |
Sep 1982 |
DEX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/462,951, filed on Jan. 8, 1990, now abandoned, which is a continuation of Ser. No. 06/860,416 filed May 7, 1986, abandoned, which is a continuation of Ser. No. 477,752, filed Mar. 22, 1983, now U.S. Pat. No. 4,617,450, granted Oct. 14, 1986.
US Referenced Citations (6)
Foreign Referenced Citations (1)
Number |
Date |
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1441577 |
Jul 1976 |
GBX |
Continuations (3)
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Number |
Date |
Country |
Parent |
462951 |
Jan 1990 |
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Parent |
860416 |
May 1986 |
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Parent |
477725 |
Mar 1983 |
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