SEALING RING HAVING A POROUS LAYER
A sealing ring segment of a sealing ring assembly may include three layers. The middle layer is permeable to gas, thus allowing radial pressure-balancing on the sealing ring segment to reduce wear. The gas-permeable allows gas to permeate from a high-pressure region to a clearance gap between a radially outer surface of the segment and a bore of a cylinder. The flow of gas affects the pressure at the radially outer surface, thus reducing the resultant radial outward force on the segment, as compared to no gas permeation. The gas-permeable layer may be porous, sintered, or have any other suitable structure having suitable gas permeability properties. The gas-permeable layer may be positioned central or rearward axially, in relation to the outer layers. The gas-permeable layer may extend the full radial thickness of the sealing ring segment.
1 . A sealing ring segment comprising:
a first layer substantially impermeable to gas;
a second layer permeable to gas arranged axially adjacent to and rearward of the first layer; and
a third layer substantially impermeable to gas and arranged axially adjacent to and rearward of the second layer.
2 . The sealing ring segment of claim 1 , further comprising:
a radially inner face; and
a radially outer face configured to seal against a bore.
3 . The sealing ring segment of claim 2 , wherein the at least one ring segment is configured to allow a gas of a high-pressure region to permeate the second layer from the radially inner face at least radially to reach the radially outer face.
4 . The sealing ring segment of claim 3 , such that gas permeating the second layer to reach the radially outer face affects a pressure at the radially outer face.
5 . The sealing ring segment of claim 1 , wherein the second layer comprises a porous material permeable to the gas.
6 . The sealing ring segment of claim 1 , wherein the second layer comprises a sintered material permeable to the gas.
7 . The sealing ring segment of claim 1 , wherein at least one of the first layer, the second layer, and the third layer comprises a respective self-lubricating material.
8 . The sealing ring segment of claim 1 , wherein at least one of the first layer, the second layer, and the third layer comprises a graphite-based material.
9 . The sealing ring segment of claim 1 , wherein:
the first layer comprises a first radial thickness;
the second layer comprises a second radial thickness;
the third layer comprises a third radial thickness; and
the first, the second, and the third radial thicknesses are substantially the same.
10 . The sealing ring segment of claim 1 , wherein:
the first layer comprises a first axial thickness;
the second layer comprises a second axial thickness;
the third layer comprises a third axial thickness;
the first axial thickness, the second axial thickness, and the third axial thickness sum to a total axial thickness; and
the second axial thickness is 40% or less than the total axial thickness.
11 . A piston assembly comprising:
a piston comprising a circumferential groove; and
a sealing ring assembly arranged in the circumferential groove and comprising at least one ring segment comprising:
a first layer substantially impermeable to gas;
a second layer permeable to gas arranged axially adjacent to and rearward of the first layer; and
a third layer substantially impermeable to gas and arranged axially adjacent to and rearward of the second layer.
12 . The piston assembly of claim 11 , wherein the at least one ring segment further comprises:
a radially inner face; and
a radially outer face configured to seal against a bore.
13 . The piston assembly of claim 12 , wherein the at least one ring segment is configured to allow a gas of a high-pressure region to permeate the second layer from the radially inner face at least radially to reach the radially outer face.
14 . The piston assembly of claim 13 , such that gas permeating the second layer to reach the radially outer face affects a pressure at the radially outer face.
15 . The piston assembly of claim 11 , wherein the second layer comprises a porous material permeable to the gas.
16 . The piston assembly of claim 11 , wherein the second layer comprises a sintered material permeable to the gas.
17 . The piston assembly of claim 11 , wherein at least one of the first layer, the second layer, and the third layer comprises a respective self-lubricating material.
18 . The piston assembly of claim 11 , wherein at least one of the first layer, the second layer, and the third layer comprises a graphite-based material.
19 . The piston assembly of claim 11 , wherein:
the first layer comprises a first radial thickness;
the second layer comprises a second radial thickness;
the third layer comprises a third radial thickness; and
the first, the second, and the third radial thicknesses are substantially the same.
20 . The piston assembly of claim 11 , wherein:
the first layer comprises a first axial thickness;
the second layer comprises a second axial thickness;
the third layer comprises a third axial thickness;
the first axial thickness, the second axial thickness, and the third axial thickness sum to a total axial thickness; and
the second axial thickness is 40% or less than the total axial thickness.
21 . A device comprising:
a cylinder comprising a bore; and
a piston assembly arranged to move axially in the bore and comprising:
a piston comprising a circumferential groove, and
a sealing ring assembly arranged in the circumferential groove, configured to seal against the bore, and comprising at least one ring segment comprising:
a first layer substantially impermeable to gas,
a second layer permeable to gas arranged axially adjacent to and rearward of the first layer, and
a third layer substantially impermeable to gas and arranged axially adjacent to and rearward of the second layer.
22 . The device of claim 21 , wherein the at least one ring segment further comprises:
a radially inner face; and
a radially outer face configured to seal against the bore.
23 . The device of claim 22 , wherein the at least one ring segment is configured to allow a gas of a high-pressure region of the bore to permeate the second layer from the radially inner face at least radially to reach the radially outer face.
24 . The device of claim 23 , such that gas permeating the second layer to reach the radially outer face affects a pressure between the radially outer face and the bore.
25 . The device of claim 21 , wherein the second layer comprises a porous material permeable to the gas.
26 . The device of claim 21 , wherein the second layer comprises a sintered material permeable to the gas.
27 . The device of claim 21 , wherein at least one of the first layer, the second layer, and the third layer comprises a respective self-lubricating material.
28 . The device of claim 21 , wherein at least one of the first layer, the second layer, and the third layer comprises a graphite-based material.
29 . The device of claim 21 , wherein:
the first layer comprises a first radial thickness;
the second layer comprises a second radial thickness;
the third layer comprises a third radial thickness; and
the first, the second, and the third radial thicknesses are substantially the same.
30 . The device of claim 21 , wherein:
the first layer comprises a first axial thickness;
the second layer comprises a second axial thickness;
the third layer comprises a third axial thickness;
the first axial thickness, the second axial thickness, and the third axial thickness sum to a total axial thickness; and
the second axial thickness is 40% or less than the total axial thickness.