Open coil electric resistance heater using twisted resistance wires and methods of making

• US 6,737,616 B1
• Filed: 04/02/2003
• Issued: 05/18/2004
• Est. Priority Date: 04/02/2003
• Status: Expired due to Term

• Current Assignee: Tutco LLC (Smiths Group International Holdings Ltd.)
• Original Assignee: Tutco, Inc.
• Inventors: Sherrill, James L.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Patel, Vinod D.
• Application Number:
  US10/404,086
• Time in Patent Office: 412 Days
• Field of Search: 219/532, 219/536, 219/537, 219/539, 219/552, 219/476, 219/477, 219/478, 338/260, 338/304, 338/305, 338/316, 338/319, 338/320
• US Class Current: 219/536
• CPC Class Codes: H05B 3/16 the conductor being mounted on an insulating base

Abstract

An open coil resistance heating apparatus uses a pair of twisted wires having a particular gauge and pitch as the resistance heating wire. Using the twisted pair of wires in the selected gauge and pitch results in significant cost reductions; less wire is needed to achieve the same heating capacity.

Claims

1. In an open coil resistance heating apparatus having a frame with a plurality of insulator supports and a plurality of insulators, the plurality of insulators being spaced apart from each other when each is mounted to a respective insulator support, and at least one resistance wire coil having a helical shape and being mounted on the plurality of spaced-apart insulators with a defined watt loading, wherein the coil has a central axis and is open to atmosphere so that a medium can be directed against the coil for medium heating, the improvement comprising a pair of resistance wires forming the at least one resistance wire coil, the pair of resistance wires twisted with respect to each other to define a pitch.

2. The apparatus of claim 1, wherein the central axis of helical coil follows a serpentine path between terminal ends of the pair of resistance wires.

3. The apparatus of claim 1, wherein a ratio of the pitch of the twisted pair of resistance wires to a wire diameter of each of the pair of resistance wires ranges between 25 and 40.

4. The apparatus of claim 3, wherein the ratio ranges between 30 and 34.

5. The apparatus of claim 3, wherein the central axis of the helical coil follows a serpentine path between terminal ends of the pair of resistance wires.

6. The apparatus of claim 1, wherein, based on the defined watt loading of the heating apparatus and the diameter of the single resistance wire, a size of each of the pair of resistance wires is based on the formula:

3.5 plus a B&

S gauge that generally corresponds to the diameter of the single resistance wire equals the size of the each of the pair of resistance wires as measured using B&

S gauge.

7. The apparatus of claim 6, wherein a gauge of each pair of resistance wires has a size range when using B&

S gauge numbers of between 16.0 and 21.0.

8. The apparatus of claim 1, wherein the pitch of the twisted pair of wires ranges between about 0.70 inches and about 2.00 inches.

9. In a method of heating a medium by forcing the medium across an open coil resistance heating apparatus having a frame with a plurality of insulator supports and a plurality of insulators, the plurality of insulators being spaced apart from each other when each is mounted to a respective insulator support, and at one resistance wire coil having a helical shape and being mounted on the plurality of spaced-apart insulators with a defined watt loading, wherein the coil has a central axis and is open to atmosphere so that a medium can be directed against the coil for medium heating, the improvement comprising heating the medium by providing a pair of resistance wires as the at least one resistance wire coil, the pair of resistance twisted with respect to each other to define a pitch.

10. The method of claim 9, wherein the medium is air.

11. The method of claim 9, wherein a ratio of the pitch of the twisted pair of resistance wires to a wire diameter of each of the pair of resistance wires ranges between 25 and 40.

12. The method of claim 11, further comprising determining the diameter of the single resistance wire based on the defined watt loading, and selecting a diameter for the pair of resistance wires according to the formula:

3.5 plus a B&

S gauge that generally corresponds to the diameter of the single resistance wire equals the size of the each of the pair of resistance wires as measured using B&

S gauge.

13. The method of claim 9, wherein the pitch of the twisted pair of wires ranges between about 0.70 inches and about 2.00 inches.

14. The method of claim 9, wherein a B&

S gauge number of each pair of resistance wires ranges between 16.0 and 21.0.

15. The method of claim 9, wherein the central axis of the helical coil follows a serpentine path between terminal ends of the pair of resistance wires.

16. A method of making a heater having a watt loading based on a single resistance wire in an open coil resistance heater comprising the steps of:

a) identifying a wire diameter of the single resistance wire and a gauge number of the wire diameter in the B&

S gauge system;

b) adding 3.5 to the identified B&

S gauge number to get a twisted wire B&

S gauge number and identifying a wire diameter size for each twisted wire based on the identified twisted wire B&

S gauge number and selecting a pair of individual resistance wires corresponding to the identified wire diameter for each twisted wire;

c) twisting the individual resistance wires around each other to form a twisted wire pair have a predefined pitch; and

e) using the twisted wire pair in the heater.

17. The method of claim 16, wherein a ratio of the pitch of the twisted pair of resistance wires to a wire diameter of each of the pair of resistance wires ranges between 25 and 40.

18. The method of claim 17, wherein the ratio ranges between about 30 and 34.

19. The method of claim 16, wherein the pitch of the twisted pair of wires ranges between about 0.70 inches and about 2.00 inches.