FORCE BALANCED SPLIT RING DYNAMIC SHAFT SEALS

• US 3,743,303 A
• Filed: 12/29/1970
• Issued: 07/03/1973
• Est. Priority Date: 12/29/1970
• Status: Expired due to Term

• Current Assignee: Adam N. Pope
• Original Assignee: Adam N. Pope
• Inventors: Pope, Adam N.
• Primary Examiner(s): Perlin, Meyer
• Assistant Examiner(s): Capossela, Ronald C.
• Application Number:
  US05/102,440
• Time in Patent Office: 917 Days
• Field of Search: 277/3,27,74,75,173
• US Class Current: 277/422
• CPC Class Codes: F01D 11/00 Preventing or minimising internal leakage of working-fluid, e.g. between stages sealings in general F16J ; sealing arrangements for transition ducts of combustor cans F01D9/023
• CPC Class Codes: F01D 11/02 by non-contact sealings, e.g. of labyrinth type for sealing space between rotor blade tips and stator F01D11/08
• CPC Class Codes: F04D 29/10 Shaft sealings
• CPC Class Codes: F16J 15/441 with floating ring
• CPC Class Codes: Y10S 277/928 Seal including pressure relief or vent feature

Abstract

A dynamic shaft seal assembly of the piston ring type includes means for generating servoforces at the seal interfaces to reduce rubbing loads and wear. The servoforces are generated by venting the bottom of a groove which supports the seal ring and by providing passageways through the seal ring to pressurize the low pressure face and the outer face thereof. The forces thus generated vary in response to changes in the dimension of the gap between the seal ring and the seal seats with the overall axial forces tending to center the seal ring in the groove. Leakage is controlled primarily by varying the dimension of a radial passageway formed between the high pressure face of the seal ring and one of the axial seats.

Claims

1. In a dynamic shaft seal assembly for an apparatus having at least one rotating component, said seal assembly including a sealing ring subjected to a relatively high pressure on one side thereof and a lower pressure on its opposite side, a radial seat for supporting said sealing ring in a radial direction, and a groove for receiving said sealing ring, said groove forming a first axial seat on one side of said ring and a second axial seat on the opposite side of said ring, the improvement of which comprises:

said sealing ring including means for generating a servoforce on a first face of said ring spaced by a gap from said first axial seat, said servoforce generating means including passage means for fluidically connecting said first face of said ring to the high pressure side of said sealing ring, said passage means being sized so as to operate as the primary restriction in the flow path from the high pressure side to the low pressure side when said gap is a first size and as a minimal restriction in the flow path when said gap is a second size, the change from the primary to the minimal restriction acting to vary said servoforce whereby said ring tends to be centered in said groove and rubbing forces between said face and said axial seat are substantially eliminated.

2. The improved seal assembly recited in claim 1 further including means for preventing flow between said sealing ring and said radial seat.

3. The improved seal assembly recited in claim 2 further characterized in that said servo force generating means include one or more circumferential grooves located in said first face of said sealing ring, and said servoforce generating means further includes means for fluidically connecting said grooves to the high pressure side of said sealing ring, said means for fluidically connecting said grooves to the high pressure side comprising at least one orifice extending through said ring, said orifice being sized so as to operate as the primary restriction in the flow path from the high pressure side to the low pressure side when said gap is a first size and as a minimal restriction in the flow path when said gap is a second size.

4. The improved seal assembly recited in claim 3 wherein said second face of said sealing ring cooperates with said second axial seat to form a generally radial flow passage which determines the approximate leakage rate for said seal assembly.

5. The improved seal assembly recited in claim 4 further including means for venting that portion of said groove which lies beneath said sealing ring to a pressure lower than that of the high pressure side of said sealing ring.

6. The improved seal assembly recited in claim 5 wherein said flow preventing means comprise a pressure dam integrally formed with, and extending in a generally radial direction from, said sealing ring.

7. The improved seal assembly recited in claim 6 wherein said pressure dam is located near the low pressure side of said sealing ring.

8. The improved seal assembly recited in claim 7 wherein said sealing ring comprises a split ring.

9. The improved seal assembly recited in claim 8 further including means for generating a radial pressure force on said sealing ring.

10. The improved seal assembly recited in claim 9 wherein said radial pressure force generating means comprise a circumferential groove positioned in the outer face of said sealing ring and passageway means for connecting said circumferential groove to the high pressure side of said sealing ring.

11. The improved seal assembly recited in claim 6 wherein said pressure dam is located near the high pressure side of said sealing ring and said sealing ring includes an axial extension on its high pressure side whereby high pressure air exerts a force radially outward on said extension.

12. The improved seal assembly recited in claim 5 wherein said sealing ring comprises a solid ring, said solid ring having a circumferential groove in its outer surface, and said flow preventing means comprise a split ring positioned within said circumferential groove in said solid ring.

13. A dynamic shaft seal assembly for an apparatus having at least one rotating component, said assembly including a solid sealing ring subject to a high pressure on one side thereof and a lower pressure on the opposite side thereof, a radial seat for supporting said solid sealing ring in a radial direction, means forming a circumferential groove for receiving said solid sealing ring, said groove forming a first axial seat on one side of said ring and a second axial seat on the opposite side of said ring, said solid ring including a groove in the outer face thereof, a split sealing ring positioned within said groove of said solid ring, and said solid sealing ring including means for generating a servoforce on a face thereof spaced from said first axial seat, said servoforce generating means including passage means for fluidically connecting said sealing ring to the high pressure side of said sealing ring, said passage means being sized so as to operate as the primary restriction in the flow path from the high pressure side to the low pressure side when said gap is a first size and as a minimal restriction in the flow path when said gap is a second size, the change from the primary to the minimal restriction acting to vary said servoforce whereby said solid ring tends to be centered in said circumferential groove and rubbing forces between said face and said first axial seat are substantially eliminated while said split sealing ring prevents flow between said ring and said radial seat.

14. The seal assembly recited in claim 13 further characterized in that said first face of said solid sealing ring includes one or more circumferential grooves and said passage means fluidically connect said grooves to the high pressure side of said ring.

15. The seal assembly recited in claim 14 wherein said second face of said solid sealing ring cooperates with said second axial seat to form a generally radial flow passage which determines the approximate leakage rate for said seal assembly.

16. The seal assembly recited in claim 15 further including means for venting that portion of said groove which lies beneath said solid sealing ring to a pressure lower than that of the high pressure side of said solid sealing ring.

17. A dynamic shaft seal assembly for an apparatus having one or more rotating components, said seal assembly including a sealing ring subjected to a relatively high pressure on one side thereof and a lower pressure on its opposite side, a radial seat for supporting said sealing ring in a radial direction, and a groove for receiving said sealing ring, said groove forming a first axial seat on one side of said ring and a second axial seat on the opposite side of said ring, said ring including a plurality of orifices, each having an inlet located in fluid flow communication with a first face of said ring spaced from said first axial seat and an outlet located in a second face of said ring spaced from said second axial seat, said second face including at least one circumferential groove therein which lies in fluid flow relationship with said outlet of at least one of said orifices, said orifices being sized with respect to a gap between said second face of said ring and said second axial seat such that a pressure drop occurs between said inlets and said outlets of said orifices when said gap is at a first relatively large dimension and substantially equal pressures exist at said inlets and outlets when said gap decreases to a relatively small dimension.