Arch-bound ring seal and ring seal system including an arch-bound ring seal

1. A ring seal assembly comprising:

a shaft having an outer circumferential surface with a diameter;

a plurality of arc-shaped ring segments mounted around the outer circumference shaft and forming a ring seal with an innermost diameter, each of the plurality of ring segments having a radially outer face, a radially inner face, a first axial side face, a second axial side face, a first circumferential end and a second circumferential end, the plurality of ring segments being shiftable between an arch-bound configuration wherein the first circumferential end of each ring segment circumferentially contacts the second circumferential end of an other ring segment of the plurality and a non-arch-bound configuration wherein the first circumferential end of each ring segment is circumferentially spaced from the second circumferential end an other ring segment of the plurality, and that the innermost diameter of the ring seal is greater in the non-arch-bound configuration than in the arch-bound configuration;

a spring biasing the plurality of arc-shaped ring segments toward the arch-bound configuration; and

at least one circumferential ramp in the radially inner face of each of the plurality of ring segments configured to generate an air cushion when the shaft rotates inside the ring seal to radially expand the innermost diameter of the ring seal by transitioning the plurality of ring segments from the arch-bound configuration to the non-arch-bound configuration,

wherein the ring segments are sized such that the radially inner faces of the ring segments are radially spaced from the outer circumferential surface of the shaft by a gap while in the arch-bound configuration so that the ring seal is not in contact with the shaft under low rotational speed and shaft startup conditions.

2. The ring seal assembly according to claim 1 , wherein the radially inner face of each of the plurality of ring segments includes a bleed slot extending from the first axial side face toward the second axial side face and wherein the ramp extends from the bleed slot.

3. The ring seal assembly according to claim 2 , wherein the circumferential ends of each of the plurality of ring segments each include at least one circumferentially facing surface, at least one radially facing surface and at least one axially facing surface.

4. The ring seal assembly according to claim 2 , wherein the plurality of ring segments comprises at least three ring segments.

5. The ring seal assembly according to claim 1 ,

wherein the radially inner face of each of the plurality of ring segments includes a bleed slot extending from the first axial side face toward the second axial side face,

wherein the ramp extends from the bleed slot,

wherein the ramp comprises a floor of a notch formed in the radially inner face, and

wherein the circumferential ends of each of the plurality of ring segments each include at least one circumferentially facing surface, at least one radially facing surface and at least one axially facing surface.

6. A ring sealing system comprising:

a shaft having an outer surface, a portion of the outer surface having an outer diameter;

a ring seal surrounding the portion of the outer surface of the shaft and having an innermost diameter, the ring seal comprising a plurality of arc-shaped ring segments, each of the plurality of ring segments having a radially outer face, a radially inner face facing the portion of the outer surface of the shaft, a first axial side face, a second axial side face, a first circumferential end and a second circumferential end, the plurality of ring segments being shiftable between an arch-bound configuration wherein the first circumferential end of each ring segment circumferentially contacts the second circumferential end of an other ring segment of the plurality and a non-arch-bound configuration wherein the first circumferential end of each ring segment is circumferentially spaced from the second circumferential end an other ring segment of the plurality, and that the innermost diameter of the ring seal is greater in the non-arch-bound configuration than in the arch-bound configuration; and

a spring biasing the plurality of arc-shaped ring segments toward the arch-bound configuration,

the innermost diameter of the ring seal in the arch-bound configuration being greater than the outer diameter of the portion of the outer surface of the shaft on which the ring seal is mounted such that the radially inner faces of the ring segments are radially spaced from the portion of the outer surface of the shaft by a gap while in the arch-bound configuration so that the ring seal is not in contact with the shaft under low speed shaft rotation and shaft startup conditions, and wherein higher speed shaft rotation conditions cause radial outward lift such that the plurality of ring segments shift from the arch-bound configuration to the non-arch-bound configuration;

the radially inner face of each of the plurality of ring segments including a bleed slot extending from the first axial side face toward the second axial face, and including at least one recess in the radially inner face in communication with the bleed slot and extending from the bleed slot in a circumferential direction.

7. The ring sealing system according to claim 6 , wherein the portion of the outer surface of the shaft comprises a runner.

8. The ring sealing system according to claim 7 , wherein the at least one recess of each of the plurality of ring segments is configured to generate an air cushion between the runner and the radially inner faces of the plurality of ring segments when the runner rotates, and wherein the ring seal is configured to shift from the arch-bound configuration to a non-arch-bound configuration in response to a pressure generated by the air cushion.

9. The ring sealing system according to claim 6 , wherein each recess comprises a ramp extending into the radially inner face of the respective ring segment in which each recess is located.

10. The ring sealing system according to claim 6 ,

wherein the portion of the outer surface of the shaft comprises a runner,

wherein the at least one recess of each of the plurality of ring segments is configured to generate an air cushion between the runner and the radially inner faces of the plurality of ring segments when the runner rotates, and wherein the ring seal is configured to shift from the arch-bound configuration to a non-arch-bound configuration in response to a pressure generated by the air cushion, and

wherein each recess comprises a ramp extending into the radially inner face of the respective ring segment in which each recess is located.

11. A ring seal assembly comprising:

a shaft having an outer circumferential surface with a diameter;

a ring seal surrounding the shaft, the ring seal having an innermost diameter and including a plurality of curved ring segments and a plurality of joints, each ring segment having a radially outer face, a radially inner face, a first axial side face, a second axial side face, a first circumferential end and a second circumferential end, the ring seal being shiftable between an arch-bound configuration wherein the first circumferential end of each curved ring segment circumferentially contacts the second circumferential end of an other one of the curved ring segments and a non-arch-bound configuration wherein the first circumferential end of each curved ring segment is circumferentially spaced from the second circumferential end of an other one of the curved ring segments, and the innermost diameter of the ring seal is greater in the non-arch-bound configuration than in the arch-bound configuration;

a spring biasing the ring seal toward the arch-bound configuration; and

at least one circumferential ramp in the radially inner face of each curved ring segment configured to generate an air cushion when the shaft rotates inside the ring seal to radially expand the innermost diameter of the ring seal by transitioning the ring seal from the arch-bound configuration to the non-arch-bound configuration;

wherein the ring segments are sized such that the radially inner face of each element is radially spaced from the outer circumferential surface of the shaft by a gap while in the arch-bound configuration so that the seal is not in contact with the shaft under low rotational speed and shaft startup conditions.

12. The ring seal according to claim 11 , wherein the plurality of curved ring segments comprises at least three curved ring segments.

13. The ring seal according to claim 11 , wherein the spring is formed from a material different than a material the ring seal is formed from and extends circumferentially across the plurality of joints.