Polymeric immersion heating element with skeletal support and optional heat transfer fins

• US 5,835,679 A
• Filed: 11/26/1996
• Issued: 11/10/1998
• Est. Priority Date: 12/29/1994
• Status: Expired due to Term

• Current Assignee: Rheem Manufacturing Company (Paloma Co., Ltd.), Watlow Electric Manufacturing Company
• Original Assignee: Energy Convertors, Inc., Rheem Technology Incorporated
• Inventors: Roden, James S., Eckman, Charles M.
• Primary Examiner(s): Walberg, Teresa J.
• Assistant Examiner(s): NGUYEN, QUAN PHUOC
• Application Number:
  US08/755,836
• Time in Patent Office: 714 Days
• Field of Search: 392/503, 392/497, 392/500, 392/501, 338/315, 338/316, 338/317, 338/318, 338/290, 338/286, 338/285, 338/58
• US Class Current: 392/503
• CPC Class Codes: H05B 2203/021 Heaters specially adapted for heating liquids
• CPC Class Codes: H05B 3/04 Waterproof or air-tight seals for heaters
• CPC Class Codes: H05B 3/46 heating conductor mounted on insulating base
• CPC Class Codes: H05B 3/48 heating conductor embedded in insulating material
• CPC Class Codes: H05B 3/82 Fixedly-mounted immersion heaters

Abstract

Electrical resistance heating elements, hot water heaters containing such elements, and methods of preparing such elements are provided. The electrical resistance heating elements of this invention can be disposed through a wall of a tank for heating fluid, such as water. They include a skeletal support frame having a first supporting surface thereon. They also include a resistance wire wound onto the first supporting surface and preferably connected to at least a pair of terminal end portions. The support frame and resistance wire are then hermetically encapsulated and electrically insulated within a thermally-conductive polymeric coating. The skeletal support frame of this invention improves injection molding operations for encapsulating the resistance wire, and can include heat transfer fins for improving thermal conductivity.

Claims

1. An electrical resistance heating element capable of being disposed through a wall of a tank for use in connection with heating a fluid medium, comprising:

(a) a first flanged end;

(b) a skeletal support frame having a plurality of openings therethrough and a first supporting surface thereon;

(c) a resistance wire wound onto said first supporting surface and connected to at least a pair of terminal end portions at said first flanged end of said element; and

(d) a thermally-conductive polymer coating disposed over said resistance wire for hermetically encapsulating and electrically insulating said resistance wire from said fluid.

2. The heating element of claim 1 wherein said skeletal support frame comprises a plurality of longitudinal splines.

3. The heating element of claim 2 wherein said longitudinal splines comprise a plurality of grooves for supporting said resistance wire.

4. The heating element of claim 3 further comprising a plurality of ring supports connecting said longitudinal splines.

5. The heating element of claim 4 wherein said skeletal support frame further comprises heat transfer fins disposed to extend into a fluid medium.

6. The heating element of claim 1 wherein said skeletal support frame comprises a generally tubular shape wherein said openings represent at least about 10 percent of the entire surface area of said tubular shape for facilitating a molding of said thermally-conductive polymeric coating over said resistance wire.

7. The heating element of claim 6 wherein said skeletal support frame comprises a plurality of longitudinal splines having a series of spaced grooves for receiving said resistance wire.

8. The heating element of claim 7 wherein said skeletal support frame and said thermally-conductive polymeric coating comprise a common thermoplastic resin.

9. A polymeric skeletal support frame for supporting resistance wire of an electrical resistance heating element, comprising:

a plurality of longitudinal splines including spaced grooves along their lengths, a plurality of heat transfer fins extending from said splines, said splines integrally connected by a plurality of longitudinally-spaced ring supports.

10. A water heater comprising:

(a) a tank for containing water;

(b) a heating element attached to a wall of said tank for providing electric resistance heating to a portion of the water in said tank, said heating element comprising;

(c) a skeletal support frame having a plurality of openings therethrough and a first supporting surface thereon;

(d) a resistance wire wound onto said first supporting surface and connecting to at least a pair of terminal end portions; and

(e) a thermally-conductive polymeric coating disposed over said resistance wire and a major portion of said skeletal support frame for hermetically encapsulating and electrically insulating said resistance wire from said fluid.

11. The water heater of claim 10 wherein said skeletal support frame comprises a plurality of longitudinal splines integrally connected by ring supports to provide a series of side wall apertures for facilitating the molding of said thermally-conductive polymeric coating over said resistance wire.

12. An electrical resistance heating element capable of being disposed through a wall of a tank for use in connection with heating a fluid medium, comprising:

(a) a polymeric skeletal support frame having a plurality of longitudinal splines connected by a series of spaced ring supports, said longitudinal splines comprising spaced grooves;

(b) a resistance heating wire having a pair of free ends joined to a pair of terminal end portions, said resistance heating wire wound onto and supported by said spaced grooves; and

(c) a polymeric coating containing an additive for improving the thermal conductivity of said coating disposed over said resistance wire and at least 90 percent of said skeletal support for hermetically encapsulating and electrically insulating said resistance wire from said fluid, whereby said skeletal support frame provides a plurality of openings for facilitating a molding of said polymeric coating.

13. The heating element of claim 12 wherein said skeletal support frame comprises a generally tubular shape.

14. The heating element of claim 13 further comprising heat transfer fins disposed on an internal surface of said tubular shape.

15. An electrical resistance heating element capable of being disposed through a wall of a tank for use in connection with heating a fluid medium comprising:

(a) a tubular, polymeric, skeletal support frame having a first supporting surface thereon;

(b) a resistance wire wound onto said first supporting service and connected to at least a pair of terminal end portions;

(c) a thermally-conductive polymeric coating disposed over said resistance wire and a significant portion of said support frame for hermetically encapsulating and electrically insulating said resistance wire from said fluid; and

(d) a plurality of heat transfer fins disposed to extend from the surface of said heating element to provide more efficient heating of said fluid.