Shrinkable electrical cable core for cryogenic cable
First Claim
1. A cable core construction for a cryogenic electrical cable including in combination an inner metal strip having a helical lay of a predetermined angle and with successive convolutions spaced from one another, an outer metal strip having a helical lay with its angle of lay in the opposite direction and with successive convolutions spaced from one another, whereby the angle of lay of one strip is a right hand helix and the angle of lay of the other strip is a left hand helix, the outside surfaces of the convolutions of the inner strip being immediately adjacent to the inside surfaces of the convolutions of the outer strip for mutual support of one another, means fastening the inner and outer helixes to one another at both ends of the cable, and a plastic insulating jacket for the cable extending around the outside circumference of the outer helix.
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Abstract
This invention is a cable core made of two layers of helically wound strips of metal with one layer having a right hand lay and the other layer having a left hand lay. The angle of lay is such that the diameter of the core changes at a faster rate than the length of the strips change with differences in temperature. This increase in the change of the core diameter makes the change correspond more closely to that of a plastic jacket or insulation that surround the core and thus avoids excessive stresses in the insulation as it cools and resulting cracking of the insulation in the case of substantial changes in temperature. The angle of lay of one layer is different from that of the other layer so as to set up restraint conditions that provide stability for the composite construction.
61 Citations
9 Claims
- 1. A cable core construction for a cryogenic electrical cable including in combination an inner metal strip having a helical lay of a predetermined angle and with successive convolutions spaced from one another, an outer metal strip having a helical lay with its angle of lay in the opposite direction and with successive convolutions spaced from one another, whereby the angle of lay of one strip is a right hand helix and the angle of lay of the other strip is a left hand helix, the outside surfaces of the convolutions of the inner strip being immediately adjacent to the inside surfaces of the convolutions of the outer strip for mutual support of one another, means fastening the inner and outer helixes to one another at both ends of the cable, and a plastic insulating jacket for the cable extending around the outside circumference of the outer helix.
Specification