Insulator for open coil electrical resistance heater, heater using same, and method of use
An open coil electrical resistance heater employs an insulator having a coil convolution engaging portion that is adapted to engage heater coils with small diameters, small wire diameters, and/or small pitches without distorting the coil and compromising heater performance.
1. An insulator for a heater coil in an electrical resistance heater for supporting the heater coil comprising:
at least one coil convolution engaging portion; and
an insulator support portion, the insulator support portion including a portion configured to engage structure of the electrical resistance heater so that the insulator provides electrical isolation between the structure and the heater coil,
the at least one coil convolution engaging portion further comprising:
a slot having an open end and a slot end face, the slot further comprising a first segment including the open end and sides angled with respect to a longitudinal axis of the insulator and a second segment having opposing parallel sides that terminate at the slot end face,
a pair of convolution guide portions, each convolution guide portion having an outer end face that has at least an angled portion, one end of the outer end face terminating at the open end of the slot and the other end of the outer end face terminating at an edge of an I-shaped coil convolution catch, each I-shaped coil convolution catch having a first face extending towards the longitudinal axis of the insulator and a second face that is generally aligned with the longitudinal axis of the insulator, the outer end faces adapted to guide coil convolutions into the I-shaped coil convolution catches,
wherein the first face of each I-shaped coil convolution catch is spaced a distance from the open end of the insulator in a direction parallel to the longitudinal axis of the insulator, said distance being less than a distance between the slot end face and the open end of the insulator, as measured in a direction parallel to the longitudinal axis of the insulator, wherein when a first coil convolution engages the slot end face, adjacent coil convolutions are pinched against the second faces of the I-shaped coil convolution catches and when the adjacent coil convolutions engage the first faces of the I-shaped coil convolution catches, the first coil convolution is spaced from the slot end face.
2. The insulator of claim 1 , further comprising a pair of coil convolution engaging portions with the insulator support portion between the pair.
3. The insulator of claim 1 , wherein the first face of each of the I-shaped catches is curved.
4. The insulator of claim 2 , wherein the first face of each the I-shaped catches is curved.
5. The insulator of claim 1 , wherein the slot end face is curved.
6. The insulator of claim 2 , wherein the slot end face is curved.
7. In a method of heating a fluid such as air using an open coil electrical resistance heater that includes insulators for supporting heater coils of the heater for at least electrical isolation, the improvement comprising supporting the heater coils using at least one insulator according to claim 1 .
8. In a heater having an open coil electrical resistance heater that includes insulators for supporting heater coils of the heater for at least electrical isolation, the improvement comprising at least one insulator according to claim 1 .