Pressure relieving slipper seal system

Abstract: A sealing system for use in sealing a rod bore (24) and reciprocating rod (26) including a first and second sealing assembly. The first sealing assembly (20), disposed within a gland (28) in the rod bore wall, comprises a seal ring (32), non-sealing backup rings (36, 38), and an energizer (34) that seals only in one direction. The energizer has axial and radial grooves (68, 70) permitting one way sealing. The backup rings have channels (52) preventing sealing in either direction. One embodiment of the sealing system includes the first seal assembly containing no downstream backup ring (38).

Description: The present invention relates to a sealing system for use in sealing a rod bore according to the prior art portion of claim 1. In many applications of hydraulic systems, such as in modern aircraft, there is a need to be able to manually extend and retract the rod connected to an actuator. Because of the new composite designs of aircraft bodies, when repairs are to be accomplished, one cannot jump up and down on the flight control surfaces to connect the flight control surfaces to the actuators. One has to be able to manually move the actuator to the control surface. Interstage pressure buildup or trapping between dual unvented seals of the actuator, prevents easy manual reversal of the actuator rod because the seals remain energized. Prior solutions to solving this pressure buildup problem between the two seals involved providing one of the seals with two backup rings that shift within the seal gland. In this case, the groove or gland in which the seal sits allows the seal to move back and forth axially upon the rod. It was believed that, upon system pressure reduction, the seals would move within the glands away from the interstage pressure volume thus creating a larger volume for the pressurized fluid between the two seals, whereby the increased volume would act to reduce the interstage pressure. However, in practice the pressure did not drop enough to solve the problem. Another attempt to solve the problem was by putting a pressure relieving notch in the elastomer and to provide narrow backup rings. This construction did not consistently relieve interstage pressure at all times, since the backup ring itself could act to seal within the rod bore glands. A sealing system having the features of the prior art portion of claim 1 is known from FR-A-1,135,032. The known sealing system limits the pressure buildup that occurs in the space between the two seal assemblies by venting this space. By avoiding the buildup of pressure in the interstage volume, friction can be reduced when the apparatus is not in the pressurized state so as to permit manual operation and movement of the piston. The sealing ring for use in the seal assembly comprises a ring part of resilient material provided with a sliding seal surface and pierced by vent means spaced from said surface. One or more valve members are attached to said ring part and adapted to close said vent means against passage of fluid under pressure in one direction only. A valve member is provided, the radial dimension of which is approximately two thirds of the main part of the sealing ring. The sealing ring is provided with a radial slit which extends from the corner of a step more than half-way into the thickness of the ring at this part. The ring is pierced by vent passages at intervals around its circumference which passages are spaced inwardly from the sliding surface and extend parallel to the axis of the ring from the radial slit to the face of the ring. Thus, the valve member can close the vent passages at their ends where it overlies the passages. However, when the buildup of pressure in the interstage volume is very high and the pressure drop very fast, the relief of this pressure causes the seal assembly to be pushed into the direction of the circular slit leading to the system pressure region. This causes a risk for the seal ring to be extruded into the circular slit and therefore a risk that the pressure which is built up in the interstage volume cannot bleed off so that still much friction will be left. Therefore, the invention seeks to provide a reliable pressure relief of the interstage area between the primary and secondary seals at all times and in particular when the system pressure drops rapidly after a significant buildup of pressure in the interstage volume. This problem is solved by providing the pressure relieving means in a sealing system of the above kind with a backup ring which is disposed upstream from said seal ring means toward said system pressure region, said upstream backup ring having a channel means for allowing pressure to be relieved from said interstage volume when said sealing system is in said pressure relieved state. In one embodiment the pressure relieving means comprises a seal ring, an energizer, and at least one backup ring. The seal ring provides a high pressure seal between the rod bore and reciprocating rod. The energizer, formed from an elastomer material, urges the seal ring into sealing engagement with the rod. At least one backup ring is disposed between the gland walls and the energizer-seal ring combination to prevent seal extrusion. A backup ring upstream from the energizer-seal ring combination permits pressure relief, while an optional backup ring downstream from the energizer-seal ring combination seals with the rod and prevents extrusion. In a further embodiment of the present invention, the pressure relieving means in the first seal assembly includes an elastomeric energizer, a high pressure seal ring, and at least one non-sealing backup ring. The energizer has a plurality of radial and axial grooves along its circumference and radial faces to allow the energizer to seal in a downstream direction toward the interstage volume, but not seal in an upstream direction from the interstage volume. Consequently, this arrangement relieves pressure in the interstage pressure when the sealing system is not under system pressure. The upstream backup ring has a channel means cut into the ring to prevent sealing. The channel means may comprise a butt cut or missing sector in the backup ring. The downstream backup ring also has a channel means cut into it, but in this case the channel means comprises a circumferential chamfer and an axial notch to prevent backup ring sealing in the relieving mode only. An advantage of the sealing system of the present invention is that the pressure within the interstage volume, after system pressure is lowered, is always reliably relieved, thereby allowing manual movement of the rod within the rod bore. Another advantage of the sealing system of the present invention is that of the low friction between the seals and the rod because of the diminished pressure buildup in the interstage area. Another advantage of the sealing system of the present invention is that of potential longer seal system life and potential longer seal life, since the seal assemblies are placed under a decreased pressure load when pressure in the interstage volume is relieved. A further advantage of the sealing system of the present invention is consistent venting of the pressure buildup within the interstage pressure volume. Yet another advantage of the sealing system of the present invention is the provision of backup rings which do not seal, but allow the interstage pressure to be relieved without seal extrusion. Yet another advantage of the sealing system of the present invention is that it allows for a temperature increase of the interstage volume and relief of the attendant interstage pressure without any potential extrusion of the seals. The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a cross sectional view of the first seal assembly of the sealing system, according to the present invention; Fig. 2a is a top view of an embodiment of the upstream backup ring of the assembly of Fig. 1, particularly showing the pressure relieving channel; Fig. 2b is a side view of the backup ring of Fig. 2a; Fig. 3a is a top view of an alternative design of the upstream backup ring of the assembly of Fig. 1; Fig. 3b is a side view of the backup ring of Fig. 3a; Fig. 4a is a top view of an embodiment of the downstream backup ring of the assembly of Fig. 1, particularly showing axial notches and a chamfer; Fig. 4b is a side view of the backup ring of Fig. 4a; Fig. 5a is a top view of an alternative embodiment of the downstream backup ring of the assembly of Fig. 1; Fig. 5b is a side view of the backup ring of Fig. 5a; Fig. 6a is a top view of another alternative embodiment of the downstream backup ring of the assembly of Fig. 1; Fig. 6b is a side view of the backup ring of Fig. 6a; Fig. 7 is a cross sectional view of the sealing system of the present invention in a pressurized state; Fig. 8 is a cross sectional view of the sealing system of Fig. 7 in a pressure relieving state; Fig. 9 is a cross sectional view of an alternative embodiment of the sealing system of present invention in a pressurized state; Fig. 10 is a cross sectional view of the sealing system of Fig. 9 in a pressure relieving state; Fig. 11 is a top view of the energizer of Fig. 1; Fig. 12 is a cross sectional view of the energizer of Fig. 11 taken along the line 12-12; Fig. 13 is a top view of an alternative embodiment of the energizer; Fig. 14 is a cross sectional view of the energizer of Fig. 13 taken along the line 14-14; Fig. 15 is a cross sectional view of the energizer of Fig. 13 taken along the line 15-15; Fig. 16 is a top view of a seal ring; and Fig. 17 is a cross sectional view of the seal ring of Fig. 16 along the line 17-17. In one embodiment of the invention as shown in the drawings and in particular by referring to Figs. 1 and 9, the first or primary seal assembly 20 (Fig. 1) is incorporated in the dual unvented sealing system 22 of (Fig. 9). The dual unvented sealing system 22 which provides a seal between a rod bore 24 and a reciprocating rod 26 is shown disposed in a glands 28 in rod bore wall 30. Alternatively glands 28 may be located in rod 26. The first or primary seal 20 includes an annular seal ring 32, an annular elastomeric energizer 34, both bounded in the upstream and downstream directions by annular backup rings 36 and 38 respectively. The specific parts of first seal 20 will be more thoroughly described herein. The second or secondary seal assembly 40 is a known seal that can effectively seal between rod bore 24 and rod 26. An effective second seal 40 may be made of an annular seal ring 42 and an annular elastomeric energizer 44. Seals of this type are described in U.S. Patents 4,268,045 and 4,231,578 and are hereby explicitly incorporated by reference. The first seal assembly 20 and second seal assembly 40 define an interstage volume 46. The first seal assembly 20 also separates the system pressure region 48 at system pressure, from interstage volume 46. This system pressure region 48 is considered upstream from the sealing system 22. Likewise the second seal assembly 40 separates the interstage volume 46 and ambient or outside pressure region 50, which is considered downstream from sealing system 22. The specific parts of the first seal assembly will now be discussed. By referring to Fig. 2a, an embodiment of the upstream backup ring 36 is shown wherein a channel means 52, specifically a butt cut or removed section of backup ring 36, prevents backup ring 36 from sealing within the gland 28. The discontinuity of upstream backup ring 36 prevent the ring from sealing within gland 28. Figs. 3a and 3b are an alternative embodiment of upstream backup ring 36 in which channels 54 on both faces 56 and 58 prevent upstream backup ring 36 from sealing within gland 28. The embodiment of downstream backup ring 38 as seen in Fig. 4a, shows axial notches 60 and a chamfer 62 along the circumference to prevent sealing within gland 28 when the seal system is in a relieving state. Chamfer 62 prevents the downstream backup ring 38 from sealing in gland corner when the seal system 22 is in a relieving state. Figs. 5 and 6 show alternative embodiments of downstream backup ring 38 which also prevent sealing in the relieving state, including inside axial notches 64 and circumferential axial notches 66. The energizer 34 shown in Fig. 1 is best viewed separately in Fig. 11 wherein the pressure relieving means is shown. The energizer 34 has an inside diameter 65, circumference 67 and a first and second radial face 69 and 71. An axial channel 68 along the circumference 67, and a radial channel 70 along upstream first radial face 69, prevent sealing in the upstream direction while allowing sealing in the downstream direction, when system pressure is greater than interstage pressure (ie. pressure within interstage volume 46). The axial channel 68 connects first and second radial faces 69 and 71. The radial channel 70 along the upstream first radial face 69 connect inside diameter 65 to circumference 67. An alternate embodiment of the energizer 34 is shown in Fig. 13 showing more axial and radial notches. Fig. 14 shows a cross section of elastomeric energizer 34 through radial channel 70. Fig. 15 is a cross section of energizer 34 through an axial channel 68. These channels allow interstage pressure to flow over energizer 34, toward the system pressure region, upstream. When the system pressure is less than the interstage pressure, sealing between rod bore 24 and rod 26 does not occur. The annular seal ring 32 as shown in cross section in Fig. 17, contains a circumferential recess 72 to help energizer 34 engage seal ring 32 within gland 28. An alternate embodiment of first seal assembly 20 has only one backup ring 28 on the upstream side of gland 28. The operation of sealing system in both the one backup ring and two backup ring configurations will now be discussed. Referring to Figs. 7-10, upon system activation, system pressure in the system pressure region 48 will force seal ring 32 and energizer 34 within the gland 28 toward interstage volume 46. The pressure difference between interstage volume 46 and system pressure region 48 are such that seal ring 32 and energizer 34 contact gland wall 74. Because of sealing of the second or secondary seal assembly 40 shown in Figs. 7-10, interstage pressure is built up in interstage volume 46, which pressure is generally greater than the pressure downstream from secondary seal assembly 40 in ambient or outside pressure region 50. When the system pressure upstream from the first or primary seal assembly 20 decreases to a value lower than the interstage pressure, a pressure relieved state takes place. This relieved state causes the first or primary seal assembly 20 to move slightly upstream, thereby allowing interstage pressure to flow through axial channels 68 and radial channels 70 of energizer 34 and through the various channel means in the backup ring 36 or backup rings 36 and 38. The arrows in Figs. 8 and 10 show a path of pressure relief from interstage pressure volume 46 to system pressure region 48 through energizer 34 and backup rings 36 and 38. Since the interstage pressure volume 46 is then substantially at the same pressure as the pressure in system pressure region 48, friction is reduced and manual operation of rod 26 within rod bore 24 is possible.

Claims: A sealing system for use in sealing a rod bore (24) and reciprocating rod (26), said rod bore (24) and said rod (26) including a pair of glands (28) separating a system pressure region (48) from an ambient pressure region (50) therein, said sealing system comprising: first and second seal assemblies (20, 40), each said assembly having a seal ring means (32, 42) adapted to be respectively disposed in one of said glands (28), said seal assemblies (20, 40) defining an interstage volume (46), said first seal assembly (20) having a pressure relieving means (34) for relieving pressure in said interstage volume (46), whereby said sealing system may operate in either a pressurized state or pressure relieved state characterized in that said pressure relieving means (34) includes a backup ring (36) which is disposed upstream from said seal ring means (32) toward said system pressure region, said upstream backup ring (36) having a channel means (52, 54) for allowing pressure to be relieved from said interstage volume (46) when said sealing system is in said pressure relieved state. The sealing system according to Claim 1 characterized in that said pressure relieving means comprises: a generally annular energizer (34), formed of an elastomeric material having an inside diameter (65) and a circumference (67), said energizer having a first radial face (69) and a second radial face (71), wherein said energizer is operatively arranged to seal only in a downstream direction toward said interstage volume; a seal ring means (32) for providing a high pressure seal between said rod and said rod bore, said energizer urging said seal ring means into sealing engagement with said rod; and at least one backup ring (36) located adjacent said seal ring means and said energizer, said backup ring including a channel means (52) for allowing pressure to be relieved from said interstage volume when said sealing system is in said pressure relieved state. The sealing system according Claim 2 characterized in that said circumference of said energizer includes at least one generally axial channel (68) connecting said first and said second radial faces, said radial face of said energizer opposite said interstage volume having at least one generally radial channel (70) connecting said inside diameter and said circumference, thereby allowing said energizer to seal in a downstream direction toward said interstage volume and, when said sealing system is in said pressure relieved state, to release pressure in an upstream direction. The sealing system according to Claim 2 characterized in that said channel means comprises a cut out sector (52) of said backup ring to prevent sealing of said backup ring in said gland. The sealing system according to Claim 2 characterized in that said backup rings are two in number, the first said backup ring (36) located upstream from said seal ring means and said energizer, the second said backup ring (38) located downstream from said seal ring means and said energizer. The sealing system according to Claim 5 characterized in that said channel means in said first backup ring comprises a cut out sector (52) to prevent sealing of said first backup ring in said gland and said channel means in said second backup ring comprises a circumferential chamfer (62) and an axial notch (60) to prevent sealing of said second backup ring in said gland. A sealing system for use in sealing a rod bore (24) and reciprocating rod (26), said rod bore and said rod including a pair of glands (28) separating a system pressure region (48) from an ambient pressure region (50) therein, said sealing system that may operate in either an pressurized state or a pressure relieved state, said sealing system comprising: first and second seal assemblies (20, 40), each said assembly adapted to be respectively disposed in one of said glands, said seal assemblies defining an interstage volume (46) between a system pressure region and an ambient pressure region, said first seal assembly including a pressure relieving means (34) for relieving pressure in said interstage volume; characterized by said first assembly comprising an energizer (34), formed of an elastomeric material having an inside diameter (65) and a circumference (67), said energizer having a first radial face (69) and a second radial face (71), said circumference having at least one generally axial channel (68) connecting said first and said second radial faces, said radial face opposite said interstage volume including at least one generally radial channel (70), said radial channel connecting said inside diameter and said circumference, thereby causing sealing only in a downstream direction toward said interstage volume and, when said sealing system is in a pressure relieved state, causing pressure to be released in an upstream direction toward said system pressure region; a seal ring (32) for providing a high pressure seal disposed between said rod and said rod bore, said energizer urging said seal ring into sealing engagement with said rod; and two backup rings (36, 38) located adjacent said seal ring and energizer, said first backup ring (36) being discontinuous to prevent sealing of said backup ring in said gland, said first backup ring disposed upstream from said seal ring and said energizer toward said system pressure region, said second backup ring (38) including a circumferential chamfer (62) and an axial notch (60) to prevent sealing of said second backup ring in said gland, said second backup ring disposed downstream from said seal ring and said energizer, toward said interstage pressure volume.

Inventors: MARINGER MARTIN M, MARINGER, MARTIN M.
Applicants: SHAMBAN & CO W S, W.S. SHAMBAN & COMPANY
Application year: 1992
Main classification: F16J15
IPC codes: F16J15