阅读说明：本技术 用于具有十字头和密封振荡杆的机器的改进的杆密封组件 (Improved rod seal assembly for a machine having a crosshead and a sealed oscillating rod ) 是由 P·埃斯基尔松 A·弗纳 F·X·博拉斯 A·鲍米勒 A·埃德温松 O·萨夫 于 2020-01-29 设计创作，主要内容包括：一种用于机器的杆密封组件(1),所述机器包括十字头(3)和密封振荡活塞杆(100),其中,所述杆密封组件(1)包括：密封壳体(300)、杆密封件(101)、衬套(400)和杆密封基部(200),其中,所述杆密封件(101)、衬套(400)和杆密封基部(200)是环形的并且能够相对于所述密封壳体(300)横向移动,所述壳体(300)轴向地支撑所述杆密封基部(200),所述杆密封基部(200)适于围绕所述活塞杆(100)布置并且设置有基部部分(106),其中,所述基部部分(106)包括指向第一轴向方向的下轴向表面(114)和指向第二轴向方向的上轴向表面(113),其中,所述下轴向表面(114)邻接所述壳体(300)并且所述上轴向表面(113)设置有杆密封座(201),所述杆密封件(101)适于围绕所述活塞杆(100)布置,并且具有第一端部部分(102)和第二端部部分(103),其中,所述第一端部部分(103)被布置成在所述第一轴向方向上连接到所述杆密封基部(200),并且所述衬套(400)被布置成在所述第一轴向方向上邻接所述杆密封件(101),并且所述杆密封基部(200)和所述衬套被布置成具有轴向重叠(250)。(A rod seal assembly (1) for a machine comprising a crosshead (3) and a sealed oscillating piston rod (100), wherein the rod seal assembly (1) comprises: a seal housing (300), a rod seal (101), a bushing (400) and a rod seal base (200), wherein the rod seal (101), the bushing (400) and the rod seal base (200) are annular and laterally movable with respect to the seal housing (300), the housing (300) axially supporting the rod seal base (200), the rod seal base (200) being adapted to be arranged around the piston rod (100) and being provided with a base portion (106), wherein the base portion (106) comprises a lower axial surface (114) pointing in a first axial direction and an upper axial surface (113) pointing in a second axial direction, wherein the lower axial surface (114) abuts the housing (300) and the upper axial surface (113) is provided with a rod seal seat (201), the rod seal (101) being adapted to be arranged around the piston rod (100), and having a first end portion (102) and a second end portion (103), wherein the first end portion (103) is arranged to be connected to the rod seal base (200) in the first axial direction, and the bushing (400) is arranged to abut the rod seal (101) in the first axial direction, and the rod seal base (200) and the bushing are arranged with an axial overlap (250).)

1. A rod seal assembly (1) for a machine comprising a crosshead (3) and a sealed oscillating piston rod (100), wherein the rod seal assembly (1) comprises:

a seal housing (300), a rod seal (101), a bushing (400), and a rod seal base (200), wherein,

the stem seal (101), bushing (400) and stem seal base (200) are annular and laterally movable relative to the seal housing (300),

the housing (300) axially supporting the stem seal base (200),

the rod sealing base (200) is adapted to be arranged around the piston rod (100) and is provided with a base portion (106), wherein the base portion (106) comprises:

a lower axial surface (114) pointing in a first axial direction,

an upper axial surface (113) pointing in a second axial direction, wherein,

the lower axial surface (114) abutting the housing (300) and the upper axial surface (113) being provided with a stem seal seat (201),

the rod seal (101) is adapted to be arranged around the piston rod (100) and has a first end portion (102) and a second end portion (103), wherein the first end portion (103) is arranged to be connected to the rod seal base (200) in the first axial direction, and

the bushing (400) is arranged to abut the rod seal (101) in the first axial direction,

it is characterized in that the preparation method is characterized in that,

the stem seal base (200) and the bushing are arranged with an axial overlap (250).

2. The rod seal assembly (1) of claim 1 wherein the axial overlap (250) is formed by:

the bushing (400) extends in the first axial direction towards the rod seal base (200) at least partially beyond a position where the bushing (400) abuts the rod seal (101), and/or

The rod seal base (200) extends in the second axial direction towards the bushing (400) at least partially beyond a position where the rod seal base (200) abuts the rod seal (101).

3. The rod seal assembly (1) of any one of the preceding claims wherein the rod seal base (200) and the bushing (400) have radial contact at the axial overlap (250).

4. The rod seal assembly (1) of any one of the preceding claims wherein the rod seal (101) comprises a shoulder portion (104) and the bushing (400) comprises a corresponding shoulder portion (402) arranged to cooperate with the shoulder portion (104) of the rod seal (101).

5. The rod seal assembly (1) of claim 4 wherein the shoulder portions (104, 402) are corresponding conical shoulder portions such that a radial force is applied to the rod seal (101) towards the piston rod (100).

6. The rod seal assembly (1) according to claim 4 or 5, wherein the shoulder portion (104) of the rod seal (101) is provided with a secondary sealing ring (105).

7. The stem seal assembly (1) according to any one of the preceding claims, wherein the seal housing (300) extends radially inwardly with respect to an outer periphery (109) of the base (106) of the stem seal base (200) at both axial sides of the base (106) of the stem seal base (200).

8. The rod seal assembly (1) according to any one of the preceding claims, wherein an inner sealing ring (203) is arranged between the lower surface (114) of the base (106) and the seal housing (300).

9. The rod seal assembly (1) of claim 8 wherein the lower surface (114) of the base (106) is provided with an annular groove (202), wherein the annular groove (202) is defined by at least one radially inner wall (207) at which the inner sealing ring (203) is arranged.

10. The rod seal assembly (1) according to claim 8 or 9, wherein an outer sealing ring (204) is arranged between the lower surface (114) of the base portion (106) and the seal housing (300), wherein the outer sealing ring (204) is arranged radially outside the inner sealing ring (203).

11. The rod seal assembly (1) of claim 10 wherein the annular groove (202) includes an outer radial wall (208) and the outer seal ring (204) is disposed at the outer radial wall (208).

12. The rod seal assembly (1) of claim 10 or 11 wherein the base (106) further comprises a pressure relief channel (205) arranged to connect the lower axial surface (113) and the upper axial surface (114) of the base (106).

13. The rod seal assembly (1) of claim 12 wherein the rod seal assembly (1) further comprises an upper seal ring (111) disposed between the upper axial surface of the base (106) and the seal housing (300), and the pressure relief channel (205) opens between the inner seal ring (203) and the outer seal ring (204) at the lower axial surface (114) and opens radially inward of the upper seal ring (111) at the upper axial surface (113).

14. The rod seal assembly (1) of claim 13 wherein the lower axial surface (114) of the base portion (106) varies in axial extension such that it abuts the seal housing (300) only radially outward of the outer seal ring (204).

15. The rod seal assembly (1) of claim 13 or 14 wherein the outer diameter (D3) of the upper seal ring (111) is smaller than the outer diameter (D2) of the outer seal ring (204).

16. The rod seal assembly (1) of claim 15 wherein an upper axial surface of the rod seal base (200) confined to a radially inner side of the upper seal (111) and a radially outer side of the outer seal (204) is substantially equal to a lower axial surface of the rod seal base (200) located radially inner side of the inner seal (203).

17. The rod seal assembly (1) according to any one of the preceding claims 10 to 16, wherein the housing (300) is provided with a channel (203) extending from the outside of the rod seal assembly into the rod seat assembly (1) in the vicinity of the outer sealing ring (204) at a location radially outside the outer sealing ring.

18. The rod seal assembly (1) according to any one of claims 1 to 10, wherein the rod seal base (200) comprises a transverse bearing (700) arranged to allow a transverse displacement of the rod seal base (200) and the seal housing (300).

19. The rod seal assembly (1) of claim 18 wherein the transverse bearing (700) comprises a plurality of support rods extending from the housing (300) in a first axial direction towards the rod seal base (200) in which the rod seal base is suspended, or a plurality of laterally displaceable, longitudinally suspended rods arranged to abut the housing (300) from the rod seal base (200) in a first axial direction (AD1), or a circular ball bearing or a laminated bearing with a plurality of polymer layers between rigid layers.

20. The rod seal assembly (1) according to any one of the preceding claims, wherein the rod seal assembly (1) is provided with a gas permeable cover (600) near the first end portion (102) of the rod seal (101), wherein the cover (600) is annular and guided by the bushing (400) such that it follows the lateral movement of the bushing (100).

21. The rod seal assembly (1) according to any one of the preceding claims, wherein the rod seal assembly (1) further comprises at least one spring member (500) arranged to apply an axial force (Fs) to the rod seal (101) via the bushing (400) in the first axial direction (AD 1).

22. The rod seal assembly (1) of claim 21 wherein the spring member (500) is arranged radially outward of the rod seal (101) and at least partially axially outward of the bushing (400) and at least partially at the same axial height as the bushing (400), and preferably the spring member (500) is an extension spring (500).

23. The rod seal assembly (1) of claim 22 wherein the bushing (400) is provided with a radial flange (404), wherein the at least one spring member (500) is arranged radially outside the bushing (400) body and extends between the flange (404) and the seal housing (300).

24. A machine comprising a crosshead (3), a sealed oscillating piston rod (4) and a rod seal assembly (1) according to any one of claims 1 to 23.

25. A machine according to claim 24, wherein the machine is a stirling engine (10).

Technical Field

The present disclosure relates to a rod seal assembly for a machine having a crosshead and a sealed oscillating piston rod. In particular, the present invention relates to a rod seal assembly comprising an annular sealing ring arrangeable around a piston rod.

Background

In machines with a sealed oscillating rod, such as stirling engines, heat pumps or cryoprecipitation machines, there is a high pressure region within the cylinder, separated from a region of relatively low pressure. Obviously, the high pressure region must be sealed from the low pressure region to maintain the pressure differential.

Typically, the piston rod must extend through the seal between the high pressure region and the low pressure region, resulting in the piston rod seal forming a primary seal between the high pressure region and the low pressure region.

The piston rod together with the rest of the crank mechanism is also usually lubricated. Lubrication may also improve sealing at the piston rod seal; however, lubrication into the high pressure region of the cylinder is undesirable as it will result in increased wear and reduced efficiency of the engine. The high pressure region of the cylinder is the nominal dry region of the cylinder.

US 4,251,081 a discloses a piston rod seal comprising a gland with a tubular extension having a slightly increased diameter on the high pressure side. During piston rod oscillation, the increased diameter results in a pumping effect at the portion with increased diameter, resulting in a minimized oil delivery to the high pressure area of the cylinder. A disadvantage of the sealing properties of such piston rod seals is that, among other reasons, they also move orthogonally/laterally due to the piston rod not only moving in its axial direction, but also due to some play in the guide crosshead and the piston guide. The reason is the friction and the constraint between the seal and its support sealing the housing with respect to the stem. The limited movability of the annular seal laterally with respect to the stem results in misalignment and allows some leakage of lubricant and gas.

Disclosure of Invention

Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems by providing a rod seal assembly for a machine comprising a crosshead and a sealed oscillating piston rod according to claim 1. The proposed rod seal assembly provides an improved lateral following of the rod seal and its support portion to the piston rod. The rod seal assembly includes:

a seal housing, a stem seal, a bushing, and a stem seal base, wherein,

the stem seal, bushing and stem seal base are annular and laterally movable relative to the seal housing, the housing axially supporting the stem seal base,

the rod sealing base is adapted to be arranged around the piston rod and is provided with a base portion, wherein the base portion comprises:

a lower axial surface pointing in a first axial direction,

an upper axial surface directed in a second axial direction, wherein,

the lower axial surface abuts the housing and the upper axial surface is provided with a stem seal seat with a conical seat,

the rod seal is adapted to be arranged around the piston rod and has a first end portion and a second end portion, wherein the first end portion is arranged to be connected to the rod seal base in the first axial direction, and

the bushing is arranged to abut the stem seal in the first axial direction, wherein the stem seal base and the bushing are arranged with an axial overlap.

One exemplary effect of the axial overlap is that the bushing may be aligned with the rod seal base, whereby the lateral movement of the piston rod, which is transmitted to the rod seal, is also transmitted to the base and further to the bushing, whereby all laterally movable components are aligned by the rod seal in contact with the piston rod. Aligning all lateral movement of the rod seal assembly reduces wear of the rod seal assembly.

The rod seal may be provided with an inner diameter tapering outwardly towards its upper part, such that the rod seal has an inner diameter at its upper part which is larger than the outer diameter of the piston rod and larger than the inner diameter of its lower part.

The stem seal base and stem seal may be an integral component or separate components that abut one another. In an exemplary embodiment, the rod seal base and the rod seal are separate components, whereby the rod seat base is provided with a conical seat adapted to receive a corresponding conical first end portion of the rod seal.

In an exemplary embodiment, the stem seal is made of a soft sealing material so as to be able to form a tight seal towards any abutting surface. Exemplary materials are PTFE, PEEK, PI and its compounds, nitrile, neoprene, EPDM, rubber, fluorocarbon, and silicone.

In an exemplary embodiment, the stem seal base is made of a rigid material, such as a metal or a polymer or composite material. The bushing is made of a material having at least a rigidity that allows it to transmit the required axial force onto the rod seal.

In an exemplary embodiment of the overlap, the axial overlap is formed by the bushing extending at least partially past the location where the bushing abuts the rod seal in a first axial direction toward the rod seal base.

In an exemplary embodiment of the overlap, the axial overlap is formed by the rod seal base extending in a second axial direction towards the bushing at least partially past the position where the rod seal base abuts the rod seal.

In an exemplary embodiment of the overlap, the stem seal base and the bushing have radial contact at the axial overlap. The radial contact is preferably configured with minimal play, whereby one exemplary effect thereof is to maximize lateral alignment therebetween.

In another exemplary embodiment, the stem seal includes a shoulder portion and the bushing includes a corresponding shoulder portion arranged to mate with the shoulder portion of the stem seal.

In an exemplary embodiment, the shoulder portion is a corresponding tapered shoulder portion such that a radial force is applied to the rod seal towards the piston rod.

In an exemplary embodiment of the stem seal, a shoulder portion of the stem seal is provided with a secondary sealing ring. The secondary seal ring is adapted to seal between the bushing and the stem seal seat.

In an exemplary embodiment of the stem seal assembly, the seal housing extends radially inward relative to an outer periphery of the base of the stem seal base at both axial sides of the base portion of the stem seal base. Thus, the seal housing at least partially encloses the stem seal base on both axial sides. One exemplary effect of this is that an equal pressure surface can be formed on the stem seal base, which can reduce friction between the stem seal base and the housing.

In another exemplary embodiment of the rod seal assembly, an inner seal ring is disposed between the lower surface of the base and the seal housing. The sealing ring is usually arranged in a groove arranged at a certain radial distance from the centre axis, in this case the axis of the piston rod. The groove may be provided in the lower surface of the housing or base. One exemplary advantage by providing an inner seal ring is that an inner region of reduced diameter is created by the inner seal ring. The inner region forms a lubricated inner wet part, whereby an unlubricated outer (radially outer side of the inner sealing ring) dry part is also created. The reduced and lubricated diameter results in less friction and wear between the rod seal base and the seal housing during lateral movement between the rod seal base and the seal housing.

In another exemplary embodiment of the stem seal base, the lower surface of the base is provided with an annular groove, wherein the annular groove is defined by at least one radially inner wall at which the inner sealing ring is arranged. The annular groove may be open, i.e. without an outer radial wall, or at least partially closed, i.e. provided with an outer radial wall. One exemplary effect of the open slots is that the only attachment point between the rod seal base and the housing is the lubrication area between the inner seal and the piston rod.

In an exemplary embodiment of the rod seal assembly, an outer sealing ring is disposed between the lower surface of the base and the seal housing, wherein the outer sealing ring is disposed radially outward of the inner sealing ring.

In one exemplary embodiment of the stem seal base, the annular groove includes an outer radial wall, and the outer seal ring is disposed at the outer radial wall.

When the inner and outer seal rings are disposed between the stem seal base and the housing, they may be disposed in the same annular groove or in separate annular grooves. If the same annular groove is used, the annular groove may have a radial extension such that a space is created between the inner sealing ring, the outer sealing ring, the stem seal base and the housing. When using a separate annular groove, a corresponding space can also be created by adjusting the distance between the rod seat base and the housing between the two annular grooves/the inner sealing ring and the outer sealing ring.

In an exemplary embodiment of the stem seal base, the base further comprises a pressure relief channel arranged to connect the lower and upper axial surfaces of the base.

In an exemplary embodiment of the stem seal assembly, the stem seal assembly further comprises an upper seal ring disposed between the upper axial surface of the stem seal base and the seal housing, and the pressure relief passage opens radially between the inner seal ring and the outer seal ring at the lower axial surface and opens radially inward of the upper seal ring at the upper axial surface.

One exemplary effect of the pressure relief channel is that the pressure relief channel equalizes the pressure of the upper surface of the stem seal base (pointing in the second radial direction) with the pressure of the lower surface of the stem seal base (pointing in the first axial direction), i.e. the lower axial surface between the inner and outer sealing rings is subjected to high pressure from inside the compression chamber. One exemplary effect of this is that a reduced axial normal force on the stem seal base can be achieved by adjusting the axial surface that is subject to the pressure on the high pressure side so that the resulting pressure is substantially zero, wherein less friction and wear is achieved between the stem seal base and the seal housing during lateral movement between the stem seal base and the seal housing.

In an exemplary embodiment of the rod seal assembly, the outer diameter of the upper seal ring is less than the outer diameter of the outer seal ring. An exemplary effect of this is that a pressure balance can be created.

In an exemplary embodiment of the stem seal base, an upper axial surface of the stem seal base radially inward of the upper seal and radially outward of the outer seal is substantially equal to a lower axial surface of the stem seal base radially inward of the inner seal. One exemplary effect of this is to achieve a pressure balance that reduces friction between the stem seal base and the housing.

In one exemplary embodiment of the rod seal base, the lower axial surface of the base portion varies in axial extension such that it abuts the seal housing only radially outside the outer seal ring. That is, radially inward of the inner seal ring, the stem seal base extends in the first axial direction less than radially outward of the outer seal ring, whereby the base portion abuts the seal housing only radially outward of the outer seal ring.

In an exemplary embodiment, the housing is provided with a channel extending into the rod seal assembly from an environment side outside the rod seal assembly adjacent to and radially outward of the outer seal ring. One exemplary effect of this is to ensure ambient pressure outside the outer sealing ring. Additionally, if the channel extends from near the opening for the piston rod, lubrication of the lower surface of the rod seal base outside the outer seal may be achieved through the channel.

In an exemplary embodiment of the rod seal assembly, the rod seal base comprises a transverse bearing arranged to allow a transverse displacement of the rod seal base and the seal housing. One exemplary effect is that the transverse bearings can be used for transverse movement of the rod seal base without minimal friction between the components, thereby minimizing wear.

In an exemplary embodiment of the transverse bearing, the transverse bearing comprises a plurality of support rods extending from the housing in a first axial direction towards a rod seal base suspended therein. In an exemplary embodiment of the transverse bearing, a plurality of transverse flexible rods are arranged to abut the housing in the first axial direction from the rod seal base. In one exemplary embodiment of the transverse bearing, the transverse bearing comprises a circular ball bearing, while in another exemplary embodiment the transverse bearing comprises a laminated bearing comprising a plurality of flexible polymer layers between rigid layers. Lateral flexibility is related to the force applied in the application.

In an exemplary embodiment of the rod seal assembly, the rod seal assembly is provided with a gas permeable cover near the first end portion of the rod seal, wherein the cover is annular and guided by the bushing such that the cover follows the lateral movement of the bushing. One exemplary effect of the cover is that it prevents dust from entering the interior of the rod seal assembly and thereby minimizes wear.

In another exemplary embodiment of the rod seal assembly, the rod seal assembly further comprises at least one spring member arranged to apply an axial force to the rod seal via the bushing in the first axial direction. One exemplary effect of this is that the bushing can maintain the force acting on the rod seal, thereby ensuring a tight seal against the piston rod.

In an exemplary embodiment of the spring member, the spring member is arranged radially outside the rod seal and at least partly axially outside the bushing and at least partly at the same axial level as the bushing. One exemplary effect of providing the spring member radially outward of the main portion of the stem seal is that lateral movement of the bushing is not affected by the spring member. In an exemplary embodiment, the spring member is an extension spring. One exemplary effect of providing a tension spring is that it does not buckle.

In a further exemplary embodiment of the spring member, the bushing is provided with a radial flange, wherein the at least one spring member is arranged radially outside the bushing body and extends between the flange and the seal housing.

One aspect of the present disclosure is directed to a machine including a crosshead, a sealed oscillating piston rod, and a rod seal assembly according to any of the embodiments disclosed herein.

In an exemplary embodiment of the machine, the machine is a stirling engine.

Further advantageous embodiments are disclosed in the appended and dependent patent claims and in the drawings discussed below.

Drawings

These and other aspects, features and advantages of the invention will become apparent from and elucidated with reference to the following description of an embodiment of the invention, which is illustrated in the accompanying schematic drawings, wherein,

FIG. 1 is a schematic cross-sectional view of an embodiment of a rod seal assembly.

FIG. 2 is a schematic cross-sectional view of an embodiment of a rod seal assembly.

Fig. 3a to 3c disclose schematic cross-sectional views of embodiments of a stem seal with an integrated stem seal base.

Fig. 4 and 5 disclose schematic cross-sectional views of different embodiments of the rod seal assembly.

Fig 6 discloses a schematic cross-sectional view of a stirling engine comprising a rod seal assembly.

Fig. 7 discloses a schematic cross-sectional view of an embodiment of a rod seal assembly.

Fig. 8 discloses a schematic cross-sectional perspective view of an embodiment of a rod seal assembly.

Fig. 9 discloses a schematic cross-sectional perspective view of an embodiment of a rod seal assembly.

Fig. 10a to 10c disclose schematic views of a transverse bearing for a rod seal assembly.

Detailed Description

The present disclosure relates to a piston rod seal assembly 1 with a rod seal 101 for a machine 10 (fig. 6) having a crosshead 11 and a sealed oscillating piston rod 10. The machine is typically a hot gas machine, such as a stirling engine comprising a compression cylinder 12 and an expansion cylinder 13. The compression cylinder 12 is provided with a rod seal assembly 1 according to any embodiment disclosed herein. The rod seal assembly 1 seals the high pressure HP region from the low pressure LP region in the cylinder. The low pressure LP region typically has ambient pressure. The rod seal assembly 1 also seals and restricts lubricant from entering the high pressure HP region of the cylinder. Due to the improved lateral following of the rod seal 101 and its supporting components, e.g. rod seal base 200, bushing 400, spring 500, the rod seal assembly 1 disclosed herein results in reduced wear of the rod seal assembly 1 during lateral movement of the piston rod 100, reduced wear on the components of the rod seal assembly 1. Thereby, an additional effect is that leakage between the high pressure HP region and the low pressure region and between the dry region and the wet region is reduced, which substantially corresponds to the high pressure region and the low pressure region.

Fig. 1 discloses an exemplary embodiment of a piston rod seal assembly 1 according to the present disclosure. The rod seal assembly 1 is disposed in the cylinder 2 and includes an annular rod seal 101 disposed about a piston rod 100. The stem seal 101 has a lower partially tapered portion 103. That is, the lower portion of the rod seal 101 has a tapered outer surface that tapers inwardly toward its center and thus toward the piston rod 100. The lower tapered portion 103 is arranged to contact a separate annular stem seal base 200. The stem seal base 200 and the stem seal 101 are disposed within the seal housing 300. The stem seal base 200 seals between the seal housing 300 and the stem seal 101. The seal housing 300 has a passage 301 through which the piston rod 100 may be arranged to oscillate. The seal housing 300 may also form an enclosure or partial enclosure for the rod seal assembly 1. The seal housing 300 may also be referred to as a seal plate 300.

The exemplary embodiment of the rod seal 101 has an inner diameter that tapers outwardly towards its upper portion 102, such that the rod seal has an inner diameter that is slightly larger than the outer diameter Dp of the piston rod 100 at its upper portion 102. For example, the upper inner diameter Du at the upper portion 102 of the rod seal 101 is larger than the lower inner diameter D1 of the lower tapered portion 103 of the rod seal 101, and the upper inner diameter Du is thus larger than the outer diameter Dp of the piston rod 100, which is substantially equal to the lower inner diameter D1.

The seal ring 200 may also be referred to as a stem seal seat 200 or a stem seal base 200.

In an exemplary embodiment, the stem seal 101 and the stem seal base 200 form one integral component. The stem seal base 200 thus forms a lower part of the stem seal 101, as exemplarily disclosed in fig. 3a to 3 c. One exemplary effect of this is that fewer individual components are required in the rod seal assembly 1.

In the embodiment disclosed in fig. 1, 2 and 3-5 and 6-9, the stem seal base 200 and the stem seal 101 are separate components, and the stem seal base 200 has a conical seat 201. Embodiments are disclosed in which separate stem seal 101 and stem seal base 200 are interchangeable with the integrated stem seal 101 and stem seal base 200.

Now, in the embodiment disclosed in fig. 1, the conical seat 201 of the stem seal base 200 forms a conical seat for the stem seal 101. The piston rod 100, rod seal 101, and rod seal mount 200 may all move laterally relative to the seal housing 300. The rod seal base 200 is laterally fixed relative to the piston rod 100. The provision of the rod seal base 200 enables the piston rod 100 and the rod seal 101 to move laterally and maintain sealing performance in comparison to existing solutions. This is because the rod seal 101 is not retained relative to the seal housing 300, but is at least somewhat free to move laterally with the lateral movement of the piston rod 100.

To maintain the lower tapered portion 103 of the stem seal 101 within the stem seal base 200, a force is applied to the stem seal 101 toward the seal ring 200. This force is an axial force, i.e. it acts in the direction of the longitudinal extension of the rod seal 101. This force may be provided by a spring 500. The spring 500 may apply a force to the bushing 400 disposed around the rod seal 101. The bushing 400 may apply an axial force to at least the stem seal 101. The bushing 400 has a portion 402 for contacting the stem seal 101. The bushing 400 may be an annular bushing provided with an external shoulder 401 at a lower portion thereof. The external shoulder 401 forms a seat for the lower portion of the spring 500. The spring 500 may be disposed around the bushing 400. The spring 500 may be radially outward of the bushing 400. That is, the rod seal 101 may be inside the bushing 400 and the spring 500 may be outside the bushing 400. Alternatively, the axial force may be provided by inherent spring capabilities in the bushing 400.

As disclosed in all disclosed embodiments of the stem seal assembly 1, the stem seal base 200 and the bushing 400 have an axial overlap 250 where they have a radial contact such that the bushing 400 is guided by the stem seal base 200, i.e. the bushing 400 is laterally aligned with the stem seal base 200. The exemplary effect is that the bushing 400 always follows the lateral movement of the stem seal base 200.

Although not shown in the figures, the conical seat 201 and the lower conical portion 103 of the stem seal 101 may alternatively be flat, laterally extending portions that form a pair of mating surfaces. That is, the pair of mating surfaces extend at an angle of 90 ° to the longitudinal axis of the rod seal 101 and/or the piston rod 100. In this arrangement, there is no radial force applied by the seal ring 200 to the stem seal 101, and vice versa. The seal ring 200 and the stem seal 101 will only apply axial forces to each other in line with the longitudinal axis of the stem seal 101.

An embodiment in which the stem seal 101 and the stem seal base 200 are integral is disclosed in fig. 3a to 3 c. The stem seal 101 includes a lower portion that is a seal ring 200.

An enlarged view of a portion of the rod seal assembly 1 of fig. 1 is disclosed in fig. 2. The inner wall of the bushing 400 may be provided with an inner shoulder portion 402, which may be arranged to interact with a corresponding shoulder portion 104 of the lower portion of the stem seal 101. The shoulder portion 104 of the lower portion of the stem seal 101 may be a tapered portion that tapers radially outward, i.e., away from the piston rod 100. If the shoulder portion 104 of the lower portion of the stem seal 101 is a conically tapered portion, the interior shoulder portion 402 of the bushing 400 is a correspondingly tapered portion so that the surfaces mate. That is, the inner tapered portion 402 of the bushing 400 may be disposed adjacent to the upper tapered portion 104 of the lower portion of the rod seal 101. The corresponding tapered portion causes an axial force to be applied to the rod seal 101 towards the piston rod 100. The inner shoulder portion 402 and the shoulder portion 104 may also be flat, i.e., not tapered. The flat surface extends laterally outward from the longitudinal axis of the stem seal 101. A flat surface without the conical taper described above does not apply any lateral/radial force to the stem seal 101. The force applied to the bushing 400 by the spring applies a force to the rod seal 101 to maintain the bushing in place within the rod seal base 200. The lower portion of the bushing 400 may be provided with a lip 403 that extends beyond the upper shoulder portion 104 of the lower portion of the stem seal 101 such that the stem seal is substantially enclosed within the bushing 400. The inner diameter of the lip 403 may be greater than the inner diameter of the upper portion of the bushing 400. The lip may extend in the first axial direction AD1 such that it forms an overlap 250 to the stem seal base 200. The cylindrical outer surface 413 of the lip 403 may be guided in the cylindrical bore 306 of the rod seal housing 300 to ensure that the coil spring 500 limits the buckling of the spring 500 that would tilt the bushing 400 and apply lateral radial forces to the rod seal 101. However, if the rod seal assembly 1 is displaced laterally, the compression spring 500 as shown in fig. 1 and 2 may still buckle in some circumstances and the lip 403 does not allow lateral movement of the bushing due to its guiding function. Lateral movement of the stem seal is limited because the bushing 400 cannot move laterally more than the clearance allowed between the lip 403 and the stem seal housing. However, the lip 403 does fit tightly to the stem seal base 200 at the overlap 250 so that the bushing 400 is guided thereby.

A secondary seal ring 105 may be disposed between the upper tapered portion 104 and the lower tapered portion 103 of the stem seal 101. The secondary seal ring 105 may be, for example, an O-ring or similar gasket. The secondary seal ring 105 may seal between the stem seal 101, the bushing 400, and/or the seal holder 200.

The stem seal base 200 is disposed on the interior base 302 of the seal housing 300. The stem seal base 200 is provided with an annular groove 202. The annular groove 202 may be provided with a flexible sealing ring seal 203, such as an O-ring or similar gasket. The annular groove may receive a sealing ring seal 203. The seal ring seal 203 may at least partially form a seal separating a nominally dry portion of the cylinder from a nominally lubricated portion of the cylinder. The annular groove 202 is disclosed as being formed in the stem seal base 200, but may be equivalently formed in the base 302 of the seal housing 300.

The seal housing 300 seals against the wall of the cylinder 2. The radial periphery 303 of the seal housing 300 may be provided with an annular groove 304. The annular groove 304 may receive a seal 305, such as an O-ring or similar gasket, which will seal the seal housing against the wall of the cylinder 2.

A cover 600 may be provided over the rod seal 101 to seal against particles entering the lubricant on the piston rod 100. The cover 600 is disposed distal to the stem seal base 200. That is, the cover 600 is at the end of the stem seal assembly 1 opposite the stem seal base 200. The cover 600 closes at least the area including the stem seal 101. The cover 600 may be breathable so that it does not form an airtight seal. The cover 600 may be an annular member disposed between the bushing 400 and a washer 601 disposed on top of the cover 600. The gasket 601 is secured in the seal housing 300 such that the cover 600 is held in place over the stem seal 101. The cover 600 may for example be an annular cover with a central hole for the piston rod 100. The cover may comprise, such as consist of, a non-woven fabric, such as a felt or the like. The nonwoven fabric has the advantage that it is breathable and absorbs particulate matter that may enter the lubricant. The nonwoven fabric may also partially absorb the lubricant. The particulate matter present may be metal abraded from pistons, piston rings and other components in the stirling engine.

To further reduce friction between the seal housing 300 and the stem seal base 200, the groove 202 of the stem seal base 200 may be open at its outer diameter, as disclosed in fig. 4 and 5. That is, the groove 202 may extend to the radially outer wall of the stem seal base 200. The open groove 202 results in the stem seal base 200 having an annular recess around a base portion thereof. The annular recess forms an area of reduced outer diameter at the base of the stem seal base 200. Minimizing friction between the rod seal base 200 and the seal housing 300 results in reduced wear on the rod seal 101, the seal housing 300, and the piston rod 100. The open annular groove 202 results in surface contact between the seal housing 300 and the stem seal base 200 only at the lubricated portion of the stem seal assembly 1. There is no contact at the nominally dry portion of the cylinder, which reduces wear.

To further reduce friction between the seal housing 300 and the rod seal base 200, the rod seal base 200 may be coated with a low friction coating, such as a diamond-like carbon (DLC) or Polytetrafluoroethylene (PTFE) or similar coating. The low friction coating may be combined with the open slots 202 described above or any other friction reducing means described herein. Alternatively, or the combined inner base 302 of the housing 300 may be covered with the same or similar low friction coating.

To further improve the lateral mobility of the rod seal assembly 1, and thus reduce friction and wear on the components of the rod seal assembly 1, the rod seal base 200 may comprise an upper portion having a cylindrical alignment wall 206, as shown in the embodiments disclosed in, for example, fig. 3c, 4, 5, 7, 8 and 9.

Fig. 4 discloses a stem seal base 200 having a cylindrical wall 206 extending longitudinally in a second axial direction AD2 from the periphery of the bottom portion of the stem seal base 200. The cylindrical wall 206 extends coaxially with the rod seal 101 and the piston rod 100. In the embodiment disclosed in fig. 4, the stem seal base 200 comprises a conical seat 201. The conical seat 201 forms a seat for the stem seal 101. As described above, the conical seat 201 and stem seal 101 may also be flat such that they form a pair of laterally extending mating surfaces. The cylindrical wall 206 forms an alignment wall that partially surrounds the bushing 400 and thereby forms an overlap 250, ensuring that the bushing 400 can follow the lateral movement of the stem seal 101 and stem seal base 200. The cylindrical alignment wall 206 may extend further upward around the bottom portion of the bushing 400 or in the second axial direction. The cylindrical alignment wall 206 may surround a bottom portion of the stem seal 101. As previously described, to hold the stem seal 101 in place, the stem seal 101 is urged toward the stem seal base 200 by an axial force Fs. The bushing 400 is disposed around an upper portion of the stem seal 101. The axial force Fs may be introduced by the inherent spring capacity of the bushing 400 or, as disclosed in fig. 4, by the spring 500.

As described above, in some exemplary embodiments, the stem seal base 200 and the stem seal 101 may be integral. In this arrangement, the lower portion of the bushing 400 is disposed radially between the upper portion of the stem seal 101 and at least a portion of the cylindrical wall 206.

The base portion 210 of the stem seal base 200 may be provided with a split ring-shaped groove 202 as described above. A seal 203, such as an O-ring, may be disposed at the split annular groove 202. The seal 203 seals the lubricated side of the seal assembly 1 against the non-lubricated or dry side. As described above, the stem seal base 200 may be seated on the interior base 302 of the seal housing 300.

As described above, the cover 600 may be disposed over the stem seal. The cover may be breathable. It may comprise, for example, a nonwoven material capable of preventing particles from entering the lubricant. The cover 600 may be arranged to be held in place by the bushing 400 and/or the rod seal 101. The cover 600 may move laterally with the piston rod 100, rod seal 101, bushing 400, and/or rod seal base 200. The cover 600 is disclosed in the embodiments disclosed in fig. 1, 7, 8 and 9.

All embodiments of the disclosed rod seal assembly 1 include at least one spring 500 arranged to apply a force to the bushing 400 that applies a force at the rod seal 101 towards the rod seal base 200. In some exemplary embodiments of the springs 500, at least one of the springs 500 may be an extension spring as shown in fig. 4, 5, 7, and 9. The at least one spring may be connected at a first end 501 to a flange 404 disposed on an upper portion of the bushing 400. The flange 404 is an annular transverse flange that extends around an upper portion of the bushing 400. At least one spring 500 may be connected to the seal housing 300 at a second end 502. One exemplary effect of the tension spring is that it does not buckle and therefore does not need to be held within a bushing to prevent buckling. Furthermore, the extension spring does not limit the lateral movement of the rod seal assembly 1, thus reducing wear on the seal assembly 1. The at least one spring may be a plurality of springs or may be one single spring disposed around the bushing 400 and the rod seal base 200. The individual springs may for example be made of bent sheet metal. Fig. 8 discloses an embodiment of the rod seal assembly 1 provided with a compression spring 500 comprising two annular wave springs 500. The annular wave spring also has the benefit of not buckling. The wave spring is pressed down against the shoulder of the bushing 400 by a sleeve acting between the housing 300 and the spring 500.

Since the cover 600 may be air permeable, there may be gas flow into and out of the area sealed by the cover during the engine's operating cycle. This is due to the combination of the pressure difference during the entire working cycle and the resistance of the breathable cover 600. This airflow may cause the lubricant to be delivered through the cover 600 as an aerosol. This results in the lubricant being in the nominally dry region of the cylinder and reduced performance. When using an extension spring 500 or a wave spring as in fig. 8, the spring 500 may be arranged radially outside the stem seal 101, the bushing 400 and the stem seal base 200. Providing a spring outside of the stem seal 101, bushing 400, and stem seal base 200 results in a smaller volume inside the area sealed by the cover 600. By reducing the volume sealed by the cover 600, this airflow is reduced because there is less mass within the volume and therefore less or no lubricant transferred as an aerosol. Thus, even though the embodiment of the rod seal assembly 1 provided with the cover 600 and the embodiment with the tension spring 500 do not have to be combined, the combination thereof gives additional exemplary effects, e.g., less or no transfer of lubricant.

The exemplary embodiment of the stem seal assembly 1 of FIG. 5 is provided with a member 700 having a lateral compliance greater than its axial compliance that may be disposed between the stem seal base 200 and the seal housing 300. Fig. l0a to 10c disclose different embodiments according to 700. An embodiment of a member 700 as a laminated bearing 710 is disclosed in fig. 10 a. The laminated bearing 710 may be disposed between the rod seal base 200 and the seal housing 300. The laminated bearing 710 includes a plurality of rigid plate layers 711 separated by compliant layers 712. The compliant layer 712 of the laminated bearing 710 enables radial and lateral compliance while providing a substantially rigid axial platform. That is, the bearing 710 is substantially rigid in the axial direction of the piston rod 100, and flexible in a direction perpendicular to the axial direction of the piston rod 100. The laminated bearing 710 effectively separates the transverse forces from the longitudinal axial forces (i.e., forces coincident with the axis of the piston rod 100).

The stem seal base 200 may be arranged to sit on the laminated bearing 710. The rod seal base 200 may be provided with a support flange 205 that abuts the stack bearing 710 at its upper portion. The laminated bearing 710 abuts the inner base 302 of the seal housing 300. The laminated bearing 710 may be disposed radially outward of the seal 203. In some cases, the seal 203 may not be included, in which case the laminated bearing 701 may form a seal at a lower portion of the stem seal base 200.

In one embodiment of the member 700, instead of or in addition to the laminated bearing 710, the rod seal base 200 may be provided with a spherical roller bearing (not disclosed) that enables lateral movement of the rod seal base 200. Thus, the spherical roller bearing is disposed at the base of the rod seal base 200, in contact with the inner base 302 of the seal housing 300. The spherical roller bearing may be arranged radially outside the seal 203. The spherical bearing enables guided lateral movement of the rod seal assembly 1.

In an exemplary embodiment of the member 700 disclosed in fig. 10b, the member 700 comprises a plurality of laterally displaceable, longitudinally depending bars 720 at which the rod seal base 200 is arranged to be supported. In this arrangement, the seal housing 300 is provided with a member 721 extending longitudinally upward from the inner base 302 in the second axial direction AD2, the member having a flange 722 extending radially inward toward the piston rod seal 101. The flange 722 has a recess 723 for receiving each of the depending rods 720. The stem seal base 200 is provided with a recess 724 for receiving each depending stem 720. The rod seal base 200 is longitudinally retained by a plurality of depending rods 720 while the rod seal base is at least partially laterally movable. The depending stem 720 extends between a flange 722 of the housing 300 and the stem seal base 200.

In an exemplary embodiment of the member 700 disclosed in fig. 10c, the member 700 is a rod bearing 730 comprising a plurality of rods 731 arranged between two sheets 732, 733. The plurality of rods 731 are axially rigid, but provide lateral flexibility to allow lateral movement of the rod seal base 200. The rod bearing 730 is disposed axially between the rod seal base 200 and the housing's inner base 302.

The different embodiments of the disclosed member 700 may be interchanged and combined.

As shown in fig. 5, a labyrinth seal 405 may be provided in the liner 400. The labyrinth seal 405 may be disposed outside of the cover 600, i.e., on the opposite side of the cover 600 from the stem seal 101, i.e., the high pressure side HP. Labyrinth seal 405 further seals the nominally dry portion of the cylinder from lubricant ingress. Labyrinth seal 405 may include one or more recesses in the stem opening of bushing 400.

Fig. 5 shows an embodiment of a piston rod sealing assembly 1 comprising a piston rod 100, an annular rod seal 101 arranged around the piston rod 100. The stem seal 101 has a lower partially tapered portion 103. That is, the lower portion of the rod seal 101 has a tapered outer surface that tapers inwardly toward its center and tapers therein toward the piston rod 100. The lower tapered portion 103 is arranged to contact a separate stem seal base 200. The stem seal base 200 and the stem seal 101 are disposed within the seal housing 300. The stem seal base 200 seals between the seal housing 300 and the stem seal 101. The seal housing 300 has a passage 301 through which the piston rod 100 may be arranged to oscillate. The seal housing 300 may also form an enclosure or partial enclosure for the rod seal assembly 1. The seal housing 300 may also be referred to as a seal plate or a rod seal plate 300.

In fig. 1, an exemplary embodiment of a rod seal 101 is provided with an inner diameter that tapers outwardly towards its upper portion 102, such that the rod seal has an inner diameter Du that is slightly larger than the outer diameter Dp of the piston rod 100 at its upper portion 102. For example, the upper inner diameter Du at the upper portion 102 of the rod seal 101 is larger than the lower inner diameter D1 of the lower tapered portion 103 of the rod seal 101, and the upper inner diameter Du is thus larger than the outer diameter Dp of the piston rod 100, which is substantially equal to the lower inner diameter D1. All embodiments disclosed herein may be provided with such a rod seal 101.

In the exemplary embodiment of the stem seal 101 disclosed in fig. 1, 2, 4, 5, 7, 8, 9, the stem seal base 200 forms a conical seat 201 for the stem seal 101. The rod seal base 200 and the bushing 400 form an overlap 250 to align the bushing with the lateral movement of the rod seal base 200, and thus the rod seal 101 and the piston rod 100.

To maintain the lower tapered portion 103 of the stem seal 101 within the stem seal base 200, a force Fs is applied to the stem seal 101 towards the stem seal seat 200. The force Fs is an axial force, i.e. it acts in the direction of the longitudinal extension of the rod seal 101. The force Fs may be provided by a plurality of springs 500. The spring 500 may apply a force Fs to the bushing 400 disposed around the rod seal 101.

The bushing 400 is radially arranged within the cylindrical wall 206 of the stem seal holder 200, or the bushing 400 extends in the first axial direction AD1 to align with the stem seal base 200 at the base portion 200 thereof. The bushing 400 has a portion 401 for contacting the stem seal 101. The springs 500 may be arranged at substantially equal circumferential distances around the bushing 400. The spring 500 may be radially outward of the bushing 400. That is, the rod seal 101 is disposed inside the bushing 400, and the spring 500 is disposed radially outside the bushing 400. The spring 500 may be provided in connection with a flange 404 provided at an upper region of the bushing 400. The spring may be connected at a first end thereof to a flange 404 of the bushing 400 or to an element fixed to the bushing 400 during operation. The second end of the spring is connected to the housing 300.

In the exemplary embodiment disclosed in fig. 7, the pressure disc 110 is arranged at the housing, axially above the stem seal base 200. The pressure disc 110 is provided with a first annular groove and a second annular groove in its base. The annular grooves are provided with flexible sealing rings 111, 112.

The first annular groove has a diameter D3 that defines a region A3.

The stem seal base 200 has a recess 202 in its base. The recess 202 is defined by a pair of walls extending from the stem seal base 200 in the first axial direction AD1 that are perpendicular to the face of the lower surface of the stem seal base 200.

The recess 202 has a first seal 203 disposed at the innermost wall of the recess 202. The first seal 203 has a diameter D1. Diameter D1 defines and bounds a region a1, which is the region radially within first seal 203. Region a1 is nominally wet, so the friction in this region is generally lower than the region subject to lubrication during the duty cycle.

The recess 202 has a second seal 204 disposed at an outermost wall of the recess 202. That is, radially outward of the first seal 203. Second seal 204 has a diameter D2.

A pressure difference Δ R exists between the pressure in the crankcase of the hot-air engine (i.e., the low pressure region LP) and the working gas in the cylinder of the hot-air engine (i.e., the high pressure region HP). This Δ R applies a normal force to the region a1 at the stem seal 101 toward the stem seal seat 200. Since Δ R may be on the order of 100 bar, this force may be significant and cause wear at the surface of the stem seal base 200 that abuts the housing 300.

The diameter of the second seal 204 is larger than the diameter of the annular groove in which the upper seal 111 is disposed.

A pressure relief passage 205 is provided in the stem seal base 200 from the high pressure HP region above the pressure disc 110 to the groove 202. The pressure relief channel 205 enables high pressure working gas to enter the groove 202, thereby equalizing the pressure on both axial sides of the stem seal base 300.

By providing the second seal 204 and the upper seal 111 in the above-described relationship, the pressure on the respective axial sides of the stem seal base 200 becomes the same, whereby the normal force at which the stem seal base 200 abuts the housing 300 is minimized to be substantially equal to the force Fs exerted by the bushing 400 on the stem seal 101. That is, during a work cycle, only the force of the plurality of springs 500 applies a normal force and may cause friction at the stem seal seat 200.

Pressure compensation occurs according to the relationship where Dl, D2, D3 are as defined above and Dp is the diameter of the piston rod.

D2²–D3²＝D1²-Dp²

In the exemplary embodiment disclosed in fig. 7, the innermost wall of the recess 202 has a reduced height relative to the outer wall of the recess 202, so that contact between the innermost wall of the recess 202 and the seal housing 300 may be eliminated. The seal housing 300 is provided with a passage 302 from the lubricated crankcase area of the hot gas engine to the outer wall of the recess 202. This results in region a2 being lubricated with lubricant from the piston rod, thereby reducing friction and wear. Thus, the force Fs of the spring 500 acts only on the outermost wall of the groove 202, which is lubricated, and therefore the friction and wear of the components of the rod seal assembly 1 is reduced.

As previously described, the seal housing 300 may seal against the wall of the cylinder 2. The radial periphery 303 of the seal housing 300 may be provided with an annular groove 304. The annular groove 304 may receive a seal 305, such as an O-ring or similar gasket, that seals the seal housing against the wall of the cylinder.

Fig. 8 and 9 disclose two embodiments of a rod seal assembly 1 provided with a pressure relief channel 205 and a lubrication channel 302 as the embodiment disclosed in fig. 7. The main difference between the embodiment in fig. 8 and 9 and the embodiment in fig. 7 is that in the embodiment in fig. 8 and 9, the pressure plate 110 is replaced by a housing plate 310 arranged on the low pressure side LP of the housing 300. The housing plate 310 may be screwed or similarly attached to the housing 300.

The difference between the embodiment in fig. 8 and the embodiment in fig. 9 is that they are provided with different types of springs 500, both of which have been described previously.

As with the embodiment disclosed in fig. 7, in the embodiment disclosed in fig. 8 and 9, the space 202 between the inner and outer seal rings 203, 204 is connected with pressure from the high pressure region HP by a pressure relief passage 205, and the upper and lower axial regions of the stem seal base 200 exposed to the pressure from the high pressure region HP are substantially equal so that their final pressures cancel each other out, thereby achieving pressure balance. It is also foreseen that the relationship between the upper and lower axial regions is such that the resulting pressure also at least partially counteracts the spring force Fs, so as to reduce the normal force between the stem seal base 200 and the housing even more.

The terms "axial" and "longitudinal" as used in this disclosure are meant to coincide with the oscillation axis of the piston rod 100. I.e., up and down in fig. 1-4. The terms transverse and radial generally refer to being perpendicular to the axis of oscillation of the piston rod. These limitations are not intended to limit the present disclosure, but are merely intended to clarify terminology related to the aspects of the figures provided and described herein.

Although the present invention has been described above with reference to specific embodiments, the present invention is not intended to be limited to the specific forms set forth herein. Rather, the invention is limited only by the following claims.

In the claims, the term "comprising" does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Furthermore, singular references do not exclude a plurality. The terms "a", "an", "first", "second", etc. do not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.