Belt structures for rotary electrical contact device

1. A rotary electrical contact device, comprising:

a first sheave disposed about a first axis;

a second sheave;

a third sheave;

a fourth sheave, wherein the third sheave and the fourth sheave revolve around the first axis during operation of the device; and

a belt that extends around at least a portion of each of the first, second, third, and fourth sheaves such that the belt makes electrical contact with each of the four sheaves, the belt comprising:

a first helical coil; and

a second helical coil, the second helical coil being wound around the first helical coil.

2. The rotary electrical contact device of claim 1 , further comprising a coupling mechanism that couples the first sheave, the second sheave, the third sheave, and the fourth sheave, wherein the coupling mechanism is configured to apply a force to the third sheave and the fourth sheave such that the belt is placed under tension.

3. The rotary electrical contact device of claim 1 , further comprising an idler sheave, the idler sheave configured to apply a force to the belt, wherein the force causes the belt to apply a pressure to at least one of the first, second, third, or fourth sheaves, wherein the idler sheave revolves around the first axis during operation of the device.

4. The rotary electrical contact device of claim 1 , wherein the first helical coil comprises a first electrical conductor and wherein further the second helical coil comprises a second electrical conductor.

5. The rotary electrical contact device of claim 1 , the first helical coil and the second helical coil having a same pitch such that each winding of the second coil contacts two adjacent windings of the first coil.

6. The rotary electrical contact device of claim 1 , the first helical coil and the second helical coil being wound in a same direction.

7. The rotary electrical contact device of claim 1 , the first helical coil having a first end, the second helical coil having a second end, the belt being formed by threading the first end of the first helical coil into the second end of the second helical coil.

8. The rotary electrical contact device of claim 1 , the belt further comprising a substantially inextensible core element positioned such that the first helical coil and the second helical coil are wrapped around the core element.

9. The rotary electrical contact device of claim 8 , the core element comprising an aramid fiber.

10. The rotary electrical contact device of claim 8 , the belt further comprising a protective sheath that surrounds the core element, the protective sheath being surrounded by the first helical coil and the second helical coil.

11. The rotary electrical contact device of claim 10 , wherein the sheath comprises a polymer.

12. The rotary electrical contact device of claim 1 , wherein the second helical coil is composed of a material having a greater hardness than the first helical coil.

13. The rotary electrical contact device of claim 1 , wherein the first helical coil comprises a first copper wire and the second helical coil comprises a second copper wire.

14. The rotary electrical contact device of claim 1 , wherein at least one of the first helical coil or the second helical coil comprises a copper-clad steel wire.

15. A method for manufacturing a rotary electrical contact device, the method comprising:

constructing a conductive belt, wherein constructing the conductive belt comprises:

winding a first conductive element and a second conductive element around a winding tool such that the first conductive element forms an inner helical coil and the second conductive element forms an outer helical coil, the outer helical coil surrounding the inner helical coil, the outer helical coil and the inner helical coil having respective first and second ends; and

threading a first end of the inner helical coil into a second end of the outer helical coil such that the inner helical coil and the outer helical coil form the conductive belt;

obtaining a plurality of at least four sheaves; and

installing the conductive belt around the at least four sheaves such that the conductive belt makes contact with each of the at least four sheaves.

16. The method of claim 15 , wherein constructing the conductive belt further comprises threading a core element through the inner helical coil prior to threading the first end of the inner helical coil into the second end of the outer helical coil, wherein the core element is substantially inextensible.

17. An electric machine comprising:

a rotor;

a stator;

a first sheave disposed about a first axis and coupled to the rotor;

a second sheave coupled to the stator;

a third sheave;

a fourth sheave, wherein the third sheave and the fourth sheave revolve around the first axis during operation of the device; and

a belt that extends around at least a portion of each of the first, second, third, and fourth sheaves such that the belt makes electrical contact with each of the four sheaves, the belt comprising:

a first helical coil; and

a second helical coil, the second helical coil being wound around the first helical coil.

18. The electric machine of claim 17 , wherein the electric machine is a motor.

19. The electric machine of claim 17 , wherein the electric machine is a generator.

20. The electric machine of claim 17 , wherein the belt further comprises a core element that extends through an interior of the belt defined by the first helical coil and the second helical coil, wherein the core element is substantially inextensible.