Sealing device for piston rod of reciprocating compressor

Abstract

To provide a sealing device (15) for sealing a piston rod (8) of a reciprocating compressor (1) during a compressor rest state that improves operational safety, the sealing device (15) includes a plurality of first packing retainers (18), each having a retaining opening (18a) in which a first packing ring (19) is disposed, and a second packing retainer (20a) having a retaining opening (20a) in which a second packing ring (21) is disposed. and a second retainer (20) located closer to the second axial device end (15a) than the plurality of first packing retainers (18) in the axial direction of the sealing device (15). The second packing ring (21) is an unbroken ring having a continuous inner circumferential sealing surface (21a), the second packing ring (21) configured to seal the piston rod (8) when the compressor (1) is at rest. The sealing device (15) includes a support passage (28). the support passage (28) has a first support passage end (28a), a second support passage end (28b), and a valve (29) for opening and closing the support passage (28), and the support passage (28) vents gas leaking through at least one of the plurality of first packing rings (19) in at least a direction from the first axial device end (15a) to the second axial device end (15b) from the first support passage end (28a) to the second support passage end (28b). the sealing device (15) further having an unobstructed vent passage (31), the vent passage (31) having a first vent passage end (31a) and a second vent passage end (31b), the vent passage (31) being configured to vent gas leaking past the second packing ring (21) in a direction from the first axial device end (15a) to the second axial device end (15b) from the first vent passage end (31a) to the second vent passage end (31b).

Description

[Technical Field]

[0001] The present invention provides a sealing device for sealing a piston rod of a reciprocating compressor, the sealing device comprising: a first axial device end configured to face a cylinder of the compressor; an opposite second axial device end configured to face a crankcase of the compressor; and a plurality of first packing retainers, each retainer having a retention opening in which a first packing ring is disposed; and a second packing retainer having a retention opening in which a second packing ring is disposed, the second packing retainer being located axially closer to the second axial end than the plurality of first packing retainers. the second packing ring is an unbroken ring having a continuous inner circumferential sealing surface, the second packing ring is configured to seal against the piston rod when the compressor is at rest, and the sealing apparatus further includes a support passage having a first support passage end, a second support passage end, and a valve for opening and closing the support passage, the support passage configured to vent gas leaking past at least one of the plurality of first packing rings in a direction from the first axial device end to the second axial device end from the first support passage end to the second support passage end. The present invention further relates to a reciprocating compressor including such a sealing apparatus, as well as a method for operating such a piston compressor.

[0002] In reciprocating piston compressors, a sealing device is used to seal the compression chamber in the cylinder against the crankcase or spacer. Such a sealing device often has multiple packing retainers formed as circular plates, each with a retaining opening. A packing ring is disposed in each retaining opening, and the packing ring cooperates with the outer peripheral surface of the piston rod to form a sealing barrier during compressor operation. During compressor operation, the piston rod primarily reciprocates relative to the sealing device in the axial direction of the cylinder. Packing rings consisting of multiple segments are often used. However, such segmented packing rings are typically activated to form a sealing barrier only during operation by a pressure differential between the high pressure in the compression chamber and the low pressure in the crankcase.

[0003] However, when the compressor is at rest, these segmented rings are typically not (at least partially) activated. This is due to the fact that when the piston rod cools after stopping, the sealing surfaces of the segmented rings no longer conform to the outer surface of the piston rod, even though a certain pressure differential still exists. This essentially occurs as a result of the segmented rings and the piston rod having different thermal expansions. Therefore, at low temperatures, e.g., at ambient temperature, a certain gap forms between the segmented rings and the piston rod, and this gap forms a leakage path.

[0004] Therefore, such a segmented packing ring cannot establish a sufficient sealing barrier when in a resting state. However, this is undesirable because, when in a resting state, gas trapped inside the compression chamber may leak axially from the compression chamber, past the sealing device, toward the crankcase, e.g., into the spacer. While such leakage is not a problem in some cases, for example, when air is used as the compressed gas, it can lead to various problems when other gases, such as flammable or toxic gases, are used. When a flammable gas, such as natural gas, is compressed, leakage must be prevented for safety reasons to avoid a flammable atmosphere that may form in the spacer or in the environment surrounding the compressor. On the other hand, leakage must also be prevented for environmental reasons, since the leakage of any greenhouse gases into the environment is undesirable and, in some cases, prohibited or at least limited.

[0005] In the past, several different approaches have been developed to solve this particular leakage problem during compressor shutdown. U.S. Pat. No. 10,883,483, for example, discloses a sealing device using a non-segmented seal ring, which is activated by the residual pressure differential after shutdown when a valve in the vent line is closed. During compressor operation, the valve is open, and the seal ring is relieved by the absence of a pressure differential across the ring. However, if the sealing action of the non-segmented seal is reduced, for example due to wear or damage to the non-segmented seal ring, venting through the vent line is not possible due to the closed valve, allowing unwanted gas leakage through the worn or damaged seal ring to the crankcase or spacer. While gas from the vent line can be safely treated, for example by sending it to a combustion device, gas that accumulates in the spacer often remains untreated and can form an explosive atmosphere and / or cause environmental damage by releasing greenhouse gases into the air.

[0006] It was therefore an object of the present invention to provide a sealing device for sealing the piston rod of a reciprocating compressor in the compressor's rest state, which improves operational safety.

[0007] This object is achieved by the sealing device described above, further comprising an unobstructed ventilation path, the ventilation path having a first ventilation path end and a second ventilation path end, the ventilation path being configured to vent gas leaking past the second packing ring in a direction from the first axial device end to the second axial device end from the first ventilation path end to the second ventilation path end, thereby improving operational safety by preventing gas from entering, for example, a compressor spacer, which could create a dangerous environment, such as a flammable atmosphere, even in the event of malfunction or damage to the second packing ring.

[0008] According to a preferred embodiment, the first support passage end is connected to the retaining opening of the second packing retainer, preferably in a region radially outward of the second packing ring, or the first support passage end is located between the second packing ring and the first packing ring of the adjacent first packing retainer in the axial direction of the sealing device, or the plurality of first packing retainers includes at least two first packing retainers, and the first support passage end is located in a region of the first packing ring adjacent to the second packing ring, or between the first packing ring adjacent to the second packing ring and the first sealing device end in the axial direction of the sealing device. The first two options increase design flexibility and are substantially similar in function. The third option can be advantageous in two ways. On the one hand, this configuration provides additional sealing for the first packing ring adjacent to the second packing ring during the period between compressor shutdown and activation of the second packing ring, which is delayed due to the time required for thermal activation. On the other hand, the pressure drop across the first packing ring adjacent to the second packing ring can be used to cool the second packing ring, thereby facilitating thermal activation. In this case, it is particularly preferred if each first packing ring comprises a metallic material.

[0009] S The sealing device further includes at least one third packing retainer, the third packing retainer having a retention opening in which a third packing ring is disposed, the at least one third packing retainer being disposed closer to the second axial device end of the sealing device than the second packing retainer, and the first vent passage end being connected to the retention opening of the third packing retainer, preferably radially outward of the at least one third packing ring, or the first vent passage end being located between the second and third packing rings in the axial direction of the sealing device. The third packing ring can further improve safety by creating an additional seal barrier behind the second seal ring.

[0010] Preferably, the second vent end of the unblocked vent passage and the second support passage end of the support passage are connected to a common exhaust passage that can be connected to the exhaust space, preferably to a waste system. This allows a single waste system to be used for gas coming from the support passage and gas coming from the vent passage. In this case, the valve of the support passage can of course only open and close the support passage, while the vent passage remains unblocked.

[0011] Preferably, the valve has an electrically controllable actuator that can be controlled by a control unit to open and close the valve, for example via the compressor control unit, thereby opening and closing the support passage.

[0012] Preferably, the valve further comprises a sensor configured to generate a sensor value representative of the valve's open state, thereby forming a closed control loop, which makes it possible, for example, to not start the compressor if the valve is still closed.

[0013] In a preferred embodiment, the second packing ring is formed from a polymer-containing material having a thermal expansion coefficient at least twice that of steel, and below a predetermined activation temperature, the inner diameter of the second packing ring is smaller than the outer diameter of the piston rod to be sealed, thereby forming a tight seal between the continuous inner circumferential sealing surface of the second packing ring and the outer circumferential surface of the piston rod when the second packing ring is radially preloaded with the sealing device installed in the compressor, and at a given operating temperature, the inner diameter of the second packing ring is larger than the outer diameter of the piston rod, thereby separating the continuous inner circumferential sealing surface from the outer circumferential surface of the piston rod when the sealing device is installed in the compressor, thereby providing an axial leakage path between the inner circumferential surface of the second packing ring and the outer circumferential surface of the piston rod, thereby enabling automatic heat-dependent activation and deactivation of the sealing action of the second packing ring. By reducing the contact pressure between the second packing ring and the piston rod to zero during compressor operation, wear on the second packing ring is also minimized. Furthermore, thermal activation of the second packing ring eliminates the need for a predetermined residual pressure in the compression chamber when the compressor is shut down. This allows the sealing device of the present invention to be applied to virtually all compressor applications, regardless of the cylinder suction pressure. Therefore, the sealing device will operate even with a suction pressure substantially below ambient air (as in a vacuum compressor). On the other hand, the sealing device of U.S. Pat. No. 10,883,483, because it necessarily requires a predetermined cylinder pressure to activate the non-segmented sealing ring, cannot function in compressors whose suction pressure is below ambient pressure.

[0014] In a preferred embodiment, the material of the second packing ring has a coefficient of thermal expansion of at least 30×10 -6 K -1 , preferably at least 60 x 10 -6 K -1 , especially at least 90 × 10 -6 K -1 30×10 -6 K-1 The above ranges have been found to provide adequate expansion.

[0015] The operating temperature is preferably 90° C. or higher and / or the activation temperature is preferably 80° C. or lower, the operating temperature and activation temperature being the temperatures in the area of ​​the piston rod, in particular the temperature of the outer periphery of the piston rod, which allows for good sealing in the rest state and sufficient expansion to separate the second packing ring from the piston rod.

[0016] In a preferred embodiment, the second packing ring has a first axial end and an opposite second axial end, the second packing ring is positioned in the retaining opening of the second packing retainer with the first axial end facing the first axial end of the sealing arrangement, the second packing ring having a U-shaped cross section with radially spaced apart inner and outer legs, the inner leg providing the inner peripheral sealing surface of the second packing ring and the outer leg providing the radially outer peripheral surface, the open side of the U-shape being axially spaced apart from the first axial end of the second packing ring. the second packing ring may have one of the following configurations: a U-shaped cross section facing the opposite end, an L-shaped cross section having an axial leg and a radial leg, the axial leg carrying the inner sealing surface of the second packing ring and the radial leg carrying the radially outer peripheral surface of the second packing ring, the radial leg being disposed at the second axial end of the second packing ring, or a rectangular cross section having a plurality of openings in the second packing ring, each opening connecting the first axial end of the second packing ring to the outer peripheral surface of the second packing ring. This provides a variety of preferred shapes for the second packing ring to be flexibly adapted to various applications.

[0017] If the second packing ring has a U-shaped profile, a plurality of openings are preferably provided on the outer leg, each connecting the interior space of the U-shaped packing ring to the radially outer surface of the second packing ring, the interior space being located radially between the inner and outer legs, and the openings being spaced apart from opposite axial ends of the second packing ring. If openings are provided, the plurality of openings preferably comprise a plurality of elongated or elliptical holes, each having a longitudinal axis, a first hole end, and a second hole end opposite the longitudinal axis, the first hole end being located closer to the first ring end than the second hole end. Preferably, the axial length of the inner leg is less than the axial length of the outer leg when the second packing ring is unassembled. The openings allow gas to flow through the second packing ring. Additionally, the openings provide the second packing ring with a predetermined degree of axial flexibility, which allows for a tight fit of the second packing ring in the retention openings of the second packing retainer substantially independent of axial thermal expansion.

[0018] The material of the second packing ring is preferably a fiber-reinforced composite material, which improves the mechanical strength of the second packing ring. Additionally or alternatively, the polymer of the material of the second packing ring preferably includes at least one of polytetrafluoroethylene, polyphenylene sulfide, polyether ether ketone, polyimide, and polyamide. These polymers provide sufficient rigidity and have favorable tribological properties.

[0019] In a preferred application, at least one sealing device according to the present invention is preferably used in a reciprocating piston compressor having a plurality of cylinders, each of which is arranged with a reciprocatingly movable piston. Each piston is connected to a piston rod, and for at least one of the plurality of cylinders, a sealing device according to the present invention is arranged to seal the corresponding piston rod, the sealing device being arranged so that a first axial device end faces the cylinder and a second axial device end faces the compressor crankcase. If the compressor has two or more cylinders, a sealing device according to the present invention is preferably arranged in each cylinder.

[0020] The compressor preferably has a compressor control unit for controlling operation of the compressor, the control unit being further configured to control the electrically controllable actuator of the valve of the support passage in response to an operating condition of the compressor, thereby enabling the opening and closing of the valve to be linked to the operating condition of the compressor.

[0021] In a preferred embodiment, the compressor has an operating condition sensor, preferably a temperature sensor or a motion sensor, configured to detect a sensor value representative of an operating condition of the compressor, and an electrically controllable actuator of a valve of the support passage is configured to control the valve in response to the sensor value, or the control unit is configured to control the electrically controllable actuator of the valve in response to the sensor value, thereby allowing the valve to be opened or closed in response to a preferred condition of the compressor.

[0022] Preferably, the compressor also has a drive unit for driving the compressor, and the compressor control unit is configured to send a start signal to the drive unit to start operation of the compressor and to send an open signal to an actuator of a valve in the support passage to open the valve simultaneously with the start signal or before the start signal with a predetermined or adjustable opening lead time, the opening lead time preferably being in the range of 0 to 60 seconds. Additionally or alternatively, the control unit is preferably configured to send a stop signal to the drive unit to stop operation of the compressor and to send a close signal to an actuator of a valve in the support passage to close the valve simultaneously with the stop signal or after a predetermined or adjustable closing delay time after the stop signal, the closing delay time preferably being in the range of 0 to 120 seconds. In this way, the opening and closing of the valve can be directly linked to the start / stop of the drive unit.

[0023] The object of the present invention is to provide a method for operating a reciprocating piston compressor, the compressor having a plurality of cylinders, each of which has a reciprocatingly movable piston arranged therein, each piston connected to a piston rod, and for each of the plurality of cylinders a sealing device is provided for sealing the corresponding piston rod, the sealing device having a first axial device end facing the corresponding cylinder and an opposite second axial device end facing a crankcase of the compressor, at least one sealing device of the plurality of sealing devices comprising a plurality of first packing retainers, each retainer having a retention opening in which a first packing ring is disposed, and a second packing retainer having a retention opening in which a second packing ring is disposed, the second retainer being located axially closer to the second axial device end than the plurality of first packing retainers, the second packing ring being an uncut ring with a continuous inner circumferential sealing surface, the sealing device further having a support passage and a support member. The passage has a first support passage end, a second support passage end, and a valve for opening and closing the support passage, and the sealing device further has an unobstructed vent passage, the vent passage having a first vent passage end and a second vent passage end, and the method includes, during operation of the compressor, deactivating a seal between the piston rod and an inner peripheral sealing surface of the second packing ring, opening the valve of the support passage, and directing gas leaking past at least one of the plurality of first packing rings in a direction from the cylinder to the crankcase from the first support passage end to the second support passage end. or, while the compressor is at rest, activating a seal between the piston rod and the inner sealing surface of the second packing ring, closing a valve of the support passage, and venting gas that may leak past the second packing ring in the direction from the cylinder to the crankcase from the first vent passage end to the second vent passage end of the unobstructed vent passage.

[0024] The invention will now be explained in more detail with reference to FIGS. 1 to 4c, which show exemplary, schematic and non-limiting advantageous embodiments of the invention. [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows a reciprocating piston compressor with a sealing device according to an advantageous embodiment of the invention; [Figure 2a] 1 is a cross-sectional view showing a sealing device according to a preferred embodiment of the present invention. [Figure 2b] 1 is a cross-sectional view showing a sealing device according to a preferred embodiment of the present invention. [Figure 2c] 1 is a cross-sectional view showing a sealing device according to a preferred embodiment of the present invention. [Figure 2d] 1 is a cross-sectional view showing a sealing device according to a preferred embodiment of the present invention. [Figure 3a] 10 illustrates a second packing ring in an advantageous embodiment; [Figure 3b] 10 illustrates a second packing ring in an advantageous embodiment; [Figure 3c] 10 illustrates a second packing ring in an advantageous embodiment; [Figure 4a] FIG. 10 illustrates another preferred embodiment of the second packing ring. [Figure 4b] FIG. 10 illustrates another preferred embodiment of the second packing ring. [Figure 4c] FIG. 10 illustrates another preferred embodiment of the second packing ring.

[0026] FIG. 1 illustrates an exemplary reciprocating piston compressor 1. For simplicity's sake, the term "compressor" will be used below. The compressor 1 has a compressor casing, which in this example includes a crankcase 2, a spacer 3, and a cylinder housing 4. However, the spacer 3 is merely optional, and the compressor 1 can also be designed without the spacer 3. A crankshaft 5, which can rotate about an axis of rotation, is arranged within the crankcase 2. The crankshaft 5 is connected to a connecting rod 6, which is itself connected to a crosshead 7. The crosshead 7 is attached to the crankcase 2 via suitable bearings so that the crosshead 7 can perform axial movement. The crosshead 7 is connected to a piston rod 8, which extends through the spacer 3 into a cylinder 9 arranged within the cylinder housing 4. A piston 10, connected to the piston rod 8, is arranged within the cylinder 9. The illustrated compressor 1 is designed as a single-cylinder compressor. However, the compressor 1 may of course have several cylinders 9, each of which is arranged with a piston connected via a piston rod 8 to a common crankshaft 5. For simplicity, the invention will be described with respect to only one cylinder 9.

[0027] The compressor 1 is designed as a double-acting compressor, and the piston divides the cylinder 9 into a first compression chamber 11a facing away from the crankshaft 5 and a second compression chamber 11b facing the crankshaft 5. The first compression chamber 11a is axially closed by a first cylinder head 12a, and the second compression chamber 11b is axially closed by a second cylinder head 12b. For each compression chamber 11a, 11b, at least one inlet valve 13 and at least one outlet valve 14 are provided in the cylinder housing 4. The inlet and outlet valves 13 and 14 are shown in simplified form. The valves 13, 14 may be designed as automatic valves or may have electrically controllable actuators for opening and closing them. If the inlet valves are designed as automatic valves, a valve unloader (not shown) may additionally be provided, configured to keep the corresponding valve open independently of the pressure differential acting on the valve. The valve unloader may have an electrically controllable actuator for actuating the valve unloader.

[0028] A suitable drive unit 16 is further provided for driving the crankshaft 5 of the compressor 1. For simplicity's sake, the drive unit 16 is shown only in schematic form. The drive unit 16 can comprise, for example, a suitable electric motor, a combustion engine, or another suitable drive. In the case of an electric motor, a power supply (not shown) is also provided for supplying electrical energy. The compressor 1 further comprises a compressor control unit 17 configured to control various functions of the compressor 1. For simplicity's sake, the abbreviation "control unit" is used below. Via the control unit 17, the drive unit 16 can be controlled to start or stop the operation of the compressor 1 or to control the operating speed of the compressor 1. The control unit 17 can comprise suitable hardware and / or software. The control unit 17 can be configured, for example, to control the aforementioned actuators of the inlet valve 13 and the outlet valve 14 or the actuator of the valve unloader. Of course, other available functions of the compressor 1, such as the supply of oil to the cylinders, can also be controlled by the control unit 17. It can also control monitoring functions, such as processing sensor values.

[0029] Furthermore, the compressor 1 includes a sealing device 15 for sealing the piston rod 8. If the compressor 1 includes multiple cylinders 9, a sealing device 15 is provided for each piston rod 8 of each cylinder 9. The sealing device 15 has a first axial end 15a facing the cylinder 9 and an opposite second axial end 15b facing the crankcase 2. In the illustrated example, the first end 15a is located on the second cylinder head 12b, and the second end 15b is located on the spacer 3. Of course, this location can vary depending on the design of the compressor 1. The sealing device 15 is substantially cylindrical and includes a plurality of substantially disk-shaped packing retainers. Each packing retainer may have a retaining opening (not shown in FIG. 1) in which a packing ring can be positioned. The packing ring surrounds the piston rod 8 to form a sealing barrier. The sealing device 15 according to the present invention will be described in more detail below with reference to FIGS. 2a to 2d.

[0030] FIG. 2a illustrates a cross-sectional view of the sealing device 15 of FIG. 1 in accordance with an exemplary embodiment of the present invention. The sealing device 15 has a first axial device end 15a configured to face the cylinder 9 of the compressor 1, which represents the high-pressure side HP. The sealing device 15 has an opposite second axial device end 15b configured to face the crankcase 2 or spacer 3 of the compressor 1, respectively. The sealing device 15 includes a plurality of first packing retainers 18, each having a retention opening 18a in which a first packing ring 19 is disposed. Each of the first packing rings is configured to seal against the piston rod 8 during operation of the compressor 1. The retention opening 18a is shown for only one packing retainer 18 in FIG. 2a. The first packing retainer 18 may have the shape of a cylindrical disk and may be formed from a suitable material, such as steel or a steel alloy.

[0031] Each of the first packing rings 19 may have, for example, multiple ring segments in the axial direction (as shown in FIG. 2a) and / or multiple ring segments in the circumferential direction (not shown). The first packing rings 19 may have, for example, a tangentially cut sealing ring and a radially cut sealing ring. The tangentially cut sealing ring may have multiple ring segments in the circumferential direction that abut at cooperating sealing surfaces to form a radial seal. The radially cut sealing ring may have multiple ring segments in the circumferential direction that are configured to overlap the tangential cuts of the tangentially cut ring to form an axial seal. Combination rings having both tangential cuts and radial cuts are also known. Furthermore, a so-called “backup ring” may be disposed in the retaining opening 18a adjacent to the first packing ring 19. The backup ring is uncut and configured to prevent the ring segments of the first packing ring 19, which are typically made of plastic, from being extruded. However, the backup ring is typically made of metal and does not function to seal against the piston rod. These various packing rings are known to those skilled in the art, so a detailed description will not be provided at this time. Of course, the first packing rings 19 disposed within the first packing retainers 18 do not necessarily have to be identical.

[0032] The sealing device 15 further includes a second packing retainer 20 having a retaining opening 20a in which a second packing ring 21 is disposed. The second packing ring 21 is an unbroken ring having a circumferentially continuous inner sealing surface 21a. The second packing ring 21 is configured to be activated to seal against the piston rod 8 when the compressor 1 is at rest, but not activated when the compressor 1 is operating. The sealing action of the second packing ring 21 can be pressure activated, for example, similar to that disclosed in U.S. Pat. No. 10,883,483. However, alternatively and preferably, the sealing action of the second packing ring 21 when the compressor 1 is at rest can be thermally activated, as described in more detail below. The second packing ring 21 has a different design from the plurality of first packing rings 19. As can be seen from FIG. 2a, in the axial direction of the sealing device (corresponding to the axial direction of the piston rod 8), the second packing retainer 20 is located closer to the second axial device end 15b than the plurality of first packing retainers 18.

[0033] In the illustrated example, an intermediate plate 27 is disposed between the second packing retainer 20 and the first subsequent first packing retainer 18. The intermediate plate 27 axially defines the retention opening 20a of the second packing retainer 20 and also the retention opening 18a of the subsequent first packing retainer 18, with these openings facing each other. Thus, the intermediate plate 27 separates the second packing ring 21 disposed in the retention opening 20a of the second packing retainer 20 from the first packing ring 19 disposed in the retention opening 18a of the adjacent first packing retainer 18. However, the intermediate plate 27 is merely optional and may be omitted if the first packing retainers 18 are arranged in a mirror-image configuration.

[0034] As shown in FIG. 2a, the second packing ring 21 may have, for example, a U-shaped cross section, with the open side of the U facing the first axial device end 15a of the sealing device 15. The U-shape assists the ring in deformation under pressure load. For the same reason, the second packing ring 21 may also be L-shaped. However, in general, a ring with a solid cross section can also be used as the second packing ring 21. Preferred embodiments of the second packing ring 21 will be described below in connection with FIGS. 3a to 4c.

[0035] According to a preferred optional embodiment of the present invention, the second packing ring 21 has a thermal expansion coefficient of iron, α FE In a preferred embodiment, the second packing ring 21 may be made of a material including a polymer having a coefficient of thermal expansion α of at least twice the coefficient of thermal expansion α of α=30×10. -6 K -1 , preferably at least α=60×10 -6 K -1 , especially at least α=90×10 -6 K -1 According to a preferred embodiment, the polymer comprises at least one of polytetrafluoroethylene (known as PTFE), polyphenylene sulfide (known as PPS), polyetheretherketone (known as PEEK), polyimide (known as PI) or polyamide (known as PA). Of course, combinations of different polymers are also conceivable.

[0036] The second packing ring 21 is preferably designed so that, at (or below) a predetermined activation temperature, the inner diameter d_i of the second packing ring 21 is smaller than the outer diameter D_a of the piston rod 8, thereby radially preloading the second packing ring 21 and forming a tight seal between the continuous inner circumferential sealing surface 21a of the second packing ring 21 and the outer circumferential surface 8a of the piston rod 8. The second packing ring 21 is further designed so that, at a given operating temperature, the inner diameter d_i of the second packing ring 21 is larger than the outer diameter D_a of the piston rod 8, thereby spacing the continuous inner circumferential sealing surface 21a from the outer circumferential surface 8a of the piston rod 8 and providing an axial leakage path between the inner circumferential surface 21a of the second packing ring 21 and the outer circumferential surface 8a of the piston rod 8. The cold state at ambient temperature is shown in FIG. 2a. Of course, when the second packing ring 21 is installed, the inner diameter d_i of the second packing ring 21 corresponds to the outer diameter D_a of the piston rod 8. However, when the second packing ring 21 is not installed, the inner diameter d_i of the second packing ring 21 is smaller than the outer diameter D_a of the piston rod 8 at ambient temperature, and therefore there is an interference similar to that of a press fit.

[0037] The activation temperature at which the second packing ring 21 is in a contracted state and seals against the piston rod 8 is typically below 80°C. The operating temperature at which the second packing ring 21 is in an expanded state and no longer seals against the piston rod 8 is typically in the range of 90°C or higher. However, the activation temperature is highly dependent on the operating temperature of the compressor 1, which itself may vary depending on the particular design and application of the compressor 1. Therefore, if the expected operating temperature is known, the design of the second packing ring 21 can be adapted to the desired activation temperature. The operating temperature and activation temperature are preferably temperatures in the region of the piston rod 8, and in particular the temperature of the surface 8a of the piston rod 8.

[0038] Due to the above-mentioned features, during (sufficiently long) rest of the compressor 1, the temperature of the second packing ring 21 as well as the temperature of the piston rod 8 drops from the operating temperature to a temperature below the activation temperature, e.g., ambient temperature or a temperature between the activation temperature and ambient temperature, so that the second packing ring 21 forms a tight sealing barrier with the surface 8a of the piston rod 8. This prevents gas still contained in the cylinder 9 from escaping axially from the cylinder 9 into the spacer 3 and possibly further into the crankcase 5 or into the ambient environment.

[0039] After starting the compressor 1, the components of the compressor 1 begin to heat up during operation due to the work of compression and due to friction. In particular, the second packing ring 21 and the piston rod 8 heat up due to friction resulting from the reciprocating motion of the piston rod 8 relative to the second packing ring 21 and also relative to the plurality of first packing rings 19. After a predetermined operating period, an operating temperature is reached, and this temperature remains substantially constant during further operation. Within the scope of the present invention, "substantially constant" may mean that the operating temperature includes a predetermined fluctuation, which may be in the range of ±10°C. Due to the above-mentioned characteristics, when the operating temperature is reached, the continuous inner peripheral sealing surface 21a of the second packing ring 21 separates from the outer peripheral surface 8a of the piston rod 8, thereby forming an axial leakage path between the inner peripheral surface 21a of the second packing ring 21 and the outer peripheral surface 8a of the piston rod 8.

[0040] When the compressor 1 is stopped again, the reverse effect occurs: the components of the compressor 1 are gradually cooled until the activation temperature is reached. Once the activation temperature is reached, the second packing ring 21 contracts back onto the rod (d_i≦D_a), thereby re-establishing a tight sealing barrier. It can thus be seen that a substantially temperature-dependent sealing action is achieved automatically, without the need for any control intervention. However, as will be explained in more detail below, the sealing device can be provided with further advantageous features to improve its performance.

[0041] As shown in FIG. 2a, the second packing ring 21 preferably has a U-shaped cross-section with radially spaced apart inner and outer legs 24 and 25. A preferred embodiment of such a U-shaped second packing ring 21 is shown in detail in FIGS. 3a-3c, where FIG. 3a shows a cross-sectional view of the second packing ring 21, FIG. 3b shows a plan view of the second packing ring 21, and FIG. 3c shows an isometric view of the second packing ring 21. As can be seen in FIG. 2a, the second packing ring 21 has an outer diameter d_a that is smaller than the diameter of the retaining opening 20a of the second packing retainer 20 into which the second packing ring 21 is to be placed. Thus, a ring-shaped space is formed between the outer peripheral surface 21b of the second packing ring 21 and the inner peripheral surface of the cylindrical retaining opening 20a.

[0042] Furthermore, in the example shown in FIGS. 3a-3c, multiple openings 22 are provided on the outer leg 25 of the second packing ring 21, each connecting the interior space 23 of the U-shaped packing ring 21 to the radially outer surface 21b of the second packing ring 21. The interior space 23 is formed radially between the opposing legs 24, 25 of the U-shape. The openings 22 therefore extend through the outer leg 25 and are spaced apart from the opposing axial ends 21c, 21d of the second packing ring 21. The multiple openings 22 may have virtually any suitable shape, such as cylindrical drillings or groove-like millings. More complex shapes may also be used if the second packing ring 21 is formed, for example, by 3D printing.

[0043] Preferably, the plurality of openings 22 are shaped as elongated or elliptical holes, with elongated holes shown in FIG. 3c. Each elongated hole has a longitudinal axis L, a first hole end 22a, and a second hole end 22b opposite the longitudinal axis L. The first hole end 22a is preferably located closer to the first ring end 21c than the second hole end 22b, which is located closer to the second axial ring end 21d. Thus, the elongated holes 22 are substantially inclined relative to the front faces of the second packing ring 21, which are formed at the axial ring ends 21c, 21d. This shape is advantageous because it makes the second packing ring 21 more flexible in the axial direction.

[0044] Furthermore, the U-shaped outer leg 25 has an axial length b_a, which is longer than the axial length b_i of the inner leg 24. In the unmounted state, the length b_a of the outer leg 25 is preferably slightly longer than the axial length of the retaining opening 20a of the second packing retainer 20. In the example shown in FIG. 2a, the axial length of the retaining opening 20a of the second packing retainer 20 is defined by the distance between the axial end face of the retaining opening 20a and the opposing axial end face of the intermediate plate 27, as can be seen in FIG. 2a. The openings 22 provide the outer leg 25 with a predetermined structural elasticity, allowing the outer leg 25 to elastically deform in the axial direction and thereby fit tightly inside the retaining opening 20a. The number and arrangement of the openings 22 in the second packing ring 21 can vary depending on the size of the ring. To provide as uniform elasticity as possible in the circumferential direction, the openings 22 are preferably evenly spaced in the circumferential direction.

[0045] In the radial direction, however, the second packing ring 21 does not have such structural elasticity but is particularly rigid, so that even in a heated state at operating temperature, it is virtually not elastically deformed (or only slightly deformed) by the pressure difference. At operating temperature, as a result of thermal expansion, as described above, it is therefore ensured that the inner diameter d_i of the second packing ring 21 is always larger than the outer diameter D_a of the piston rod 8. In order to improve the structural rigidity even at higher temperatures, the material of the second packing ring 21 is advantageously a fiber-reinforced composite material.

[0046] The embodiment according to Figures 3a to 3c is of course not limiting, and as mentioned above, other embodiments are possible, some of which are described below in connection with Figures 4a to 4c.

[0047] FIG. 4a shows a U-shaped second packing ring 21 that is substantially similar to the ring shown in FIGS. 3a-3c. Therefore, only the differences will be described in detail. The second packing ring 21 according to FIG. 4a additionally includes an O-ring 37, which has a relatively high elasticity, particularly significantly higher than the material of the second packing ring 21. The O-ring is located on a shoulder formed by a circumferential groove 38. The circumferential groove 38 is located adjacent to the outer peripheral surface 21b and adjacent to the surface of the second packing ring 21 at the second axial end 21d. As can be seen in FIG. 4a, the diameter of the O-ring 37 in the unmounted state is slightly larger than the axial depth of the groove 38. In the installed state of the second packing ring 21, the O-ring 37 acts essentially like a spring. Because the axial length of the second packing ring 21 is smaller at low temperatures than at high temperatures due to thermal expansion, which also acts in the axial direction, the O-ring 37 assists in radial sealing (between the second axial end 21d of the second packing ring 21 and the axial wall of the retention opening 20a, see FIG. 2a) when the second packing ring 21 is in a low temperature state. At high temperatures, when the second packing ring 21 thermally expands axially, the O-ring 37 compresses to offset the change in axial length, thus reducing mechanical stress on the outer leg 25 of the second packing ring 21.

[0048] FIG. 4b shows a cross-sectional view of another preferred embodiment of the second packing ring 21. It can be seen that the second packing ring 21 has an L-shaped cross section. This allows for extremely simple manufacturing, since the opening 22 is not required in this embodiment. Similar to the U-shaped rings of FIGS. 3a-3c and 4a, the second axial end 21d of the L-shaped second packing ring 21 of FIG. 4b also faces the first axial device end 15a of the sealing device 15 (or the cylinder 9, respectively, see FIG. 1) or the high-pressure side HP (see FIG. 2a), respectively. Of course, an O-ring (not shown) may additionally be provided on the L-shaped packing ring 21 of FIG. 4b, as in FIG. 4a.

[0049] FIG. 4c shows a cross-sectional view of another preferred embodiment of the second packing ring 21. In this embodiment, the second packing ring 21 has a rectangular cross-section. A plurality of openings 41 are provided connecting the first axial end 21c of the second packing ring 21 to the outer peripheral surface 21b of the second packing ring 21 to allow gas flow from the first axial end 21c (cylinder side) to the outer peripheral surface 21b of the ring. The openings 41 may have virtually any suitable shape, for example, angled drillings or intersecting, preferably orthogonal, axial and radial openings, as shown in FIG. 4c.

[0050] According to the present invention, the sealing device 15 further includes a support passage 28, which has a first support passage end 28a and a second support passage end 28b, as shown in FIG. 2a. For simplicity, a portion of the support passage 28 is only shown schematically in FIG. 2a. In the illustrated embodiment, the first support passage end 28a of the support passage 28 is connected to the retaining opening 20a of the second packing retainer 20 in a region radially outward of the second packing ring 21. In particular, the first support passage end 28a opens into the space formed between the outer peripheral surface 21b of the second packing ring 21 and the inner peripheral surface of the retaining opening 20a in which the second packing ring 21 is disposed. However, this is merely one exemplary embodiment, and the first support passage end 28a of the support passage 28 does not necessarily need to be connected to the retaining opening 20a. The first support passage end of the support passage 28 may be located between the second packing ring 21 and the subsequent first packing ring 19, for example, on the inner circumferential surface of the intermediate plate 27. However, if the second packing retainer 20 is designed differently, the first support passage end 28a of the support passage 28 may be located, for example, on the inner circumferential surface of the second packing retainer 20, adjacent to the retaining opening 20a, toward the first axial device end 15a. Furthermore, a valve 29 for opening and closing the support passage 28 is provided between the first support passage end 28a and the second support passage end 28b.

[0051] 2a, a first portion of the support passage 28 is integrally formed with the second packing retainer 20, while a second portion of the support passage 28 is located outside the second packing retainer 20. The second portion of the support passage 28 may be implemented, for example, as a conduit connected to the second packing retainer 20 by a suitable connector. In the illustrated embodiment, the connector is located on the axial surface of the second packing retainer 20 facing the second device end 15b of the sealing device 15. However, other locations, for example on the radially outer peripheral surface, are also possible, provided that sufficient space is provided for connecting the second portion of the support passage 28.

[0052] In the illustrated example, the second packing retainer 20 also serves as a mounting flange for mounting the sealing device 15 to the compressor 1. For simplicity, mounting elements such as screws and the like are not shown in FIG. 2a. Of course, this is not necessary, and the second packing retainer 20 may be provided as an additional separate component in addition to the mounting flange, in particular adjacent to the mounting flange in the direction of the first axial device end 15a. In this case, a first portion of the support passage 28 (adjacent to the first passage end 28a) may be integrally formed with the second packing retainer 20, a second (middle) portion of the support passage 28 may be integrally formed with the flange, and a third portion of the support passage 28 (adjacent to the second passage end 28b) may again be implemented as a conduit. Of course, a suitable sealing element, such as an O-ring, may be disposed between the flange and the second packing retainer 20 to provide a seal between a first portion of the support passage 28 (inside the second packing retainer 20) and a second portion of the support passage 28 (inside the flange).

[0053] The support passage 28 essentially has two functions. During operation of the compressor 1 (e.g., when operating temperature is reached and the second packing ring 21 is disengaged from the piston rod 8 due to thermal activation, as described above), the function of the support passage 28 is to provide a substantially free leakage path for gas flow from the cylinder 9, past the plurality of first packing rings 19, toward the second device end 15b of the sealing arrangement 15. In this manner, in the disengaged state, the support passage 28 substantially prevents an undesirably relatively large pressure drop across the second packing ring 21 due to the relatively small (throttle-like) gap that would otherwise exist (without the passage 28) between the inner peripheral sealing surface 21a of the second packing ring 21 and the outer peripheral surface 8a of the piston rod 8. The valve 29 is, of course, open during operation of the compressor 1.

[0054] On the other hand, when the compressor 1 is at rest (e.g., below the activation temperature), in the activated sealing state of the second packing ring 21, a tight sealing barrier is formed between the second packing ring 21 and the piston rod 8. For the second packing ring 21 to develop its desired sealing effect, the support passage valve 29 must naturally be in the closed position. Otherwise, gas would not be retained and would flow through the support passage 28 in the direction of the second support passage end 28b. To automatically control the opening and closing of the valve 29, the valve 29 advantageously has an electrically controllable actuator 30, which can be controlled by a control unit (e.g., the compressor control unit 17 as shown in FIG. 2a) to open or close the valve 29.

[0055] According to the present invention, the sealing device 15 further includes an unobstructed ventilation passage 31 having a first ventilation passage end 31 a and an opposite second ventilation passage end 31 b. The ventilation passage 31 is configured to allow gas leaking from the first axial device end 15 a (or each of the cylinders 9) to the second axial device end 15 b (or each of the spacers 3) through the plurality of first packing rings 19 and through the second packing ring 21 (particularly between the inner circumferential surface 21 a of the second packing ring 21 and the outer circumferential surface 8 a of the piston rod 8) to vent from the first ventilation passage end 31 a to the second ventilation passage end 31 b. This improves safety when the compressor is idle, as gas that leaks past the second packing ring 21, for example because the second packing ring 21 is worn, damaged, or completely broken, can always be safely vented through the unobstructed vent path 31.

[0056] Preferably, the sealing device 15 further includes at least one third packing retainer 32, as shown in FIG. 2a, having a retention opening 32a in which a third packing ring 33 is disposed. The at least one third packing retainer 32 may be designed substantially similarly to the plurality of first packing retainers 18. However, as can be seen in FIG. 2a, different types of packing rings may be used for the third packing ring 33 and for the first packing ring 19. Accordingly, the size of the retention opening 32a of the third packing retainer 32 may differ from the size of the retention opening 18a of the first packing retainer 18.

[0057] The third packing retainer 32 is positioned closer to the second axial device end 15b of the sealing device 15 than the second packing retainer 20. As described above in relation to the intermediate plate 27, the retaining opening 32a of the third packing retainer 32 is defined by the axial front surface of the second packing retainer 20, which faces the second device end 15b of the sealing device 15. Like the first packing ring 19, the at least one third packing ring 33 may have, for example, multiple ring segments in the axial direction and / or multiple ring segments in the circumferential direction. In the example shown in FIG. 2a, a single third packing retainer 32 is provided, and the third packing ring 33 positioned within the retaining opening 32a of the third packing retainer 32 has three axially consecutively arranged sealing rings, each having multiple ring segments in the circumferential direction. As already described above in relation to the first packing ring 19, such rings are known.

[0058] Similar to first packing retainer 18 and second packing retainer 20, third packing retainer 32 may be formed from a single piece, e.g., milled, into which retention opening 32a is disposed, or may be assembled from two or more pieces. For example, third packing retainer 32 may have a faceplate and an adjacent piece in which third packing ring 33 is disposed. The faceplate may be a cylindrical plate, e.g., intermediate plate 27, and the adjacent piece may be a hollow cylinder, for example.

[0059] If the third packing retainer 32 is provided in the sealing device 15, the first vent passage end 31a of the unobstructed vent passage 31 may be directly connected to the retaining opening 32a of the third packing retainer 32, preferably to a space formed radially outward of the third packing ring 33, as shown in the example of FIG. 2a. Again, as described in connection with the support passage 28, a first portion of the vent passage 31 adjacent the first vent passage end 31a may be integrally formed with the third packing retainer 32, and a second portion of the vent passage 31 adjacent the second vent passage end 31b may be formed by a conduit. However, FIG. 2a only shows an exemplary embodiment, and the first vent passage end 31a of the vent passage 31, as well as the first support passage end 28a of the support passage 28, may also be located in different positions. For example, the first air passage end 31a may be located between the third packing ring 33 and the second packing ring 21 in the axial direction of the sealing device 15, for example, on the inner circumferential surface of the second packing retainer 20.

[0060] As can be seen in FIG. 2a, the second vent end 31b of the unblocked vent passage 31 and the second support passage end 28b of the support passage 28 are preferably connected to a common discharge passage 34 that can be connected to a discharge space 35. Because the vent passage 31 is unblocked, gas that leaks through the second packing ring 21 can be safely discharged into the discharge space 35 at any time. The discharge space 35 may be, for example, a reservoir for storing gas, such as a tank, or a disposal system for disposing of gas, such as a flare device for burning gas. This allows for extremely safe operation, even if the second packing ring 21 is damaged, because gas can be safely discharged through the vent passage 31 and therefore cannot enter the spacer 3 when the compressor 1 is at rest with the valve 29 in the closed position.

[0061] In the illustrated example, the valve 29 of the support passage 28 can be actuated (opened or closed) by an electrically controllable actuator 30. Preferably, the actuator 30 can be controlled in response to operating conditions of the compressor 1. For example, logic for controlling the actuator 30 of the valve 29 in response to a start signal S_start and / or a stop signal S_stop for the drive unit 16 can be implemented in the control unit 17. The control unit 17 can be configured to send a start signal S_start to the drive unit 16 to initiate operation of the compressor 1, as shown in FIG. 2a. Additionally, the control unit 17 can send an open signal S_open to the actuator 30 of the valve 29 of the support passage 28 to open the valve 29. The open signal S_open can be sent simultaneously with the start signal S_start, thereby opening the valve 29 immediately upon startup. Alternatively, the open signal S_open can be sent with a predetermined or adjustable opening lead time before the start signal S_start is sent, thereby opening the valve 29 at a predetermined time before startup. The start lead time can preferably be in the range of 0 to 60 seconds. This ensures that the valve 29 is open at the moment the compressor starts.

[0062] The control unit 16 may be configured to send a stop signal S_stop to the drive unit 16 to stop the operation of the compressor 1, and may also send a close signal S_close to the actuator 30 of the valve 29 in the support passage 28 to close the valve 29. The close signal S_close may also be sent simultaneously with the stop signal S_stop or after a predetermined or adjustable close delay time has elapsed since the stop signal S_stop was sent. The close delay time is also preferably in the range of 0 to 120 seconds. Simultaneous transmission is possible, but not required, since, according to the present invention, the second packing ring 21 is activated thermally and not by differential pressure. A predetermined close delay time may be advantageous, for example, to ensure that the piston rod 8 is fully at rest before the valve 29 is closed, thereby avoiding contact and possible wear of the second packing ring 21 in any case.

[0063] The valve 29 preferably also includes a sensor 36 for detecting the open state of the valve 29. The sensor 36 is configured to transmit a sensor value X representing the open state (e.g., open or closed position) to the control unit 17. The control unit 17 can then process the sensor value X and, for example, transmit a start signal S_start to the drive unit 16 only if a sensor signal X representing the open state of the valve 29 is received. This allows the compressor 1 to be started only when the valve 29 is open and to be prevented from starting as long as the valve 29 is closed. This prevents the compressor 1 from starting with the valve 29 closed, which would result in a high differential pressure acting on the second packing ring 21. A high differential pressure could press the packing ring 21 too hard against the piston rod 8, which could result in overheating, excessive wear, or even mechanical failure.

[0064] According to another preferred embodiment, the compressor 1 may include a suitable operating condition sensor (not shown) configured to detect a sensor value representative of the operating condition of the compressor 1. The operating condition sensor may, for example, be a temperature sensor configured to detect the operating temperature. The temperature sensor may be arranged at a suitable position for detecting the operating temperature, for example, in the region of the second packing ring 21 and / or in the region of the piston rod 8. The operating condition sensor may be connected to the control unit 17 to provide the control unit 17 with the sensor value. The control unit 17 may further be configured to control a valve 29 in the support passage 28 depending on the sensor value, in particular the operating temperature. Alternatively, the valve 29 may be directly controlled by the operating condition sensor, thereby eliminating the need for control by the control unit 17. In this case, for example, a thermally operated valve may be used as the valve 29, which essentially combines the valve 29, the actuator 30, and the operating condition sensor. The actuator 30 of the valve 29 may therefore automatically open or close the valve 29 depending on the detected sensor value, without requiring control intervention by the control unit 17.

[0065] According to an alternative embodiment, the operating condition sensor may be, for example, a motion sensor configured to detect a sensor value representative of the motion of a moving part of the compressor 1. The motion sensor may be, for example, a speed sensor for detecting the rotational speed of the crankshaft or the translational speed of the piston rod 8, etc. The motion sensor may also be connected to the control unit 17, which is configured to control the actuator 30 of the valve 29 depending on the sensor value of the motion sensor. On the other hand, the motion sensor may also be implemented in the valve 29 together with the actuator 30, so that the valve 29 is directly operated independently of the compressor control unit 17. Of course, the temperature sensor and the motion sensor are merely examples, and other sensors suitable for detecting relevant sensor values ​​representative of the operating conditions of the compressor 1 may be used. In a preferred embodiment, the actuation value of the measured sensor value, e.g., temperature, rotational speed, etc., at which the valve 29 should be closed or opened, can be adjusted, for example, via the control unit 17 or directly at the valve 29 or the actuator 30.

[0066] Although not shown in the example according to FIG. 2a, additional packing retainers may be arranged in the sealing device 15. For example, it is conceivable to add a fourth packing retainer 42 adjacent to the third packing retainer 32, which is arranged closer to the second axial device end 15b than the third packing retainer 32. An exemplary embodiment is shown in FIG. 2b. The fourth packing retainer 42 has a retaining opening 42a in which a wiping ring 43 is arranged, which serves to wipe residual oil from the outer peripheral surface 8a of the piston rod 8. The wiping ring 43 may have one or more wiping edges 43a on its inner peripheral surface. The wiping ring 43 may further have one or more drainage passages 43b connecting the inner peripheral surface of the wiping ring 43 to the outer peripheral surface. The wiped oil can be conveyed via a discharge passage 43b to an oil collection space located radially outside the wiping ring 43 and inside the retaining opening 42a. The discharge space can be connected to an oil reservoir 44 by a suitable oil return line 45. Such wiping rings 43 are known, so a detailed description will not be given at this time. Such an embodiment of the sealing device 15 including the wiping ring 43 can be used, for example, in compressors 1 that do not have a spacer 3, as the compressor 1 shown in FIG. 1 has. Such sealing devices 15 are often referred to as so-called combined sealing devices.

[0067] Like the embodiment according to FIG. 2a, the sealing device 15 according to FIG. 2b also has a support passage 28 with a valve 29 and an unobstructed ventilation passage 31. The functions of the support passage 28 and the ventilation passage 31 have already been described in detail in connection with FIG. 2a, so only the differences between the two embodiments will be described below. Unlike FIG. 2a, in the embodiment according to FIG. 2b, the first ventilation passage end 31a of the ventilation passage 31 is located between the third packing ring 33 and the second packing ring 21 in the axial direction of the sealing device 15 (or of the piston rod 8, respectively). The first portion of the ventilation passage 31 is integrally formed with the second packing retainer 20, in which the second packing ring 21 is arranged. In this case, the first ventilation passage end 31a is located on the inner circumferential surface of the second packing retainer 20. In the illustrated example, the second packing retainer 20 also serves as a mounting flange for mounting the sealing device 15 to the compressor 1. Of course, suitable attachment means (not shown), such as bolts or screws, can be provided on the flange. However, the function of the vent passage 31 remains the same as in Figure 2a. Such a design is advantageous because it allows a standardized packing retainer (without built-in passages) to be used as the third packing retainer 32.

[0068] In the embodiment of FIG. 2b, the position of the first support passage end 28a of the support passage 28 also differs from the embodiment according to FIG. 2a. In FIG. 2a, the first support passage end 28a is directly connected to the retaining opening 20a of the second packing retainer 20. In contrast to this, in FIG. 2b, the first support passage end 28a is located between the first packing ring 19_1 arranged adjacent to the second packing ring 21 and the first packing ring 19_2 that follows it in the direction of the first axial device end 15a of the sealing device 15. This design has essentially two advantages over the preferred embodiment with a thermally activated second packing ring 21. On the one hand, this configuration allows the first packing ring 19_1 adjacent to the second packing ring 21 to provide additional sealing during the period between shutdown of the compressor 1 and thermal activation of the second packing ring 21, which is delayed due to the time required for cooling and shrinkage. Therefore, until the sealing action of the second packing ring 21 is fully developed, the first packing ring 19_1 can provide additional sealing action due to the residual pressure in the cylinder 9 (FIG. 1).

[0069] To provide this additional sealing effect, the first packing ring 19_1 adjacent to the second packing ring 21 is advantageously designed differently from the subsequent first packing ring 19_2 (and differently from the other first packing ring 19_3 arranged adjacent to the first packing ring 19_2 toward the first axial device end 15a in FIG. 2b). In particular, the first packing ring 19_1 is preferably designed as a so-called "double-acting" ring and is configured to provide sealing even when there is no pressure difference across the ring. A double-acting ring can, for example, have a ring assembly with two tangentially cutting rings, for example, two identical tangentially cutting rings. Another suitable ring can, for example, be a so-called "tangential to the rod" ring. Such rings are known. The first seal ring 19_2 and the subsequent first seal ring 19_3 may be identical, for example, and may each have a ring assembly with a radial-cut ring and a tangential-cut ring, as already mentioned in connection with the first packing ring 19 in FIG. 2a. On the other hand, the pressure drop across the first packing ring 19_1 adjacent to the second packing ring 21 can be used to cool the second packing ring 21, thereby accelerating cooling and thus thermal activation. In this case, it is particularly preferred if the corresponding first packing ring 19_1 comprises a metallic material. For example, the aforementioned backup ring made of metal can be used as part of the first packing ring 19_1.

[0070] Another preferred embodiment of the sealing device 15 of the present invention will be described with reference to FIG. 2c. The plurality of first packing retainers 18 of the sealing device 15 of the illustrated embodiment includes two first packing retainers 18, each having a retention opening 18a in which a first packing ring 19 is disposed. The first packing rings 19 may also be designed as described above. Of course, a greater number of first packing retainers 18 may be provided, as in FIGS. 2a and 2b. The sealing device 15 further includes a second packing retainer 20, which has a retention opening 20a in which a second packing ring 21 is disposed. The second packing retainer 20 is disposed closer to the second device end 15b than the first packing retainers 18. An exemplary U-shaped second packing ring 21 is shown. 3a-4c, the second packing ring 21 may have a different design. Adjacent to the second packing retainer 20 is an intermediate plate 27, in which a first portion of the unobstructed ventilation passage 31 is arranged. As can be seen, similar to the embodiment according to FIG. 2b, the first ventilation passage end 31a of the ventilation passage 31 is located between the second packing ring 21 and the first packing ring 19 that follows it in the direction of the second device end 15b.

[0071] The sealing device 15 further includes a fifth packing retainer 46 having a T-shaped cross section and two retaining openings 46a axially separated by a central portion of the T-shaped cross section. A fifth packing ring 47 is disposed in each of the retaining openings 46a. Each of the fifth packing rings 47 is formed as a so-called single-acting SLP ring assembly, which has three consecutive rings in the axial direction. Each of the three rings is a cut ring and has multiple ring segments in the circumferential direction. The center ring and one of the outer rings each have a chamfer, with the chamfer of the center ring facing radially outward and the chamfer of the outer ring facing radially inward. The chamfers face each other and are in contact with each other.

[0072] As shown in FIG. 2c, the two fifth packing rings 47 are arranged in a mirror-image manner, with their outer chamfered rings facing each other axially and in contact with the central portion of the T-shaped cross section of the fifth packing retainer 46. When the sealing device 15 is installed in the compressor 1, a pressure chamber 46b is formed in the space located axially between the two fifth packing rings 47 and radially between the central portion of the T-shaped cross section of the fifth packing retainer 46 and the piston rod 8. Furthermore, a flange F is arranged on the sealing device 15 for mounting the sealing device 15 to the compressor 1. The flange F is located on the extreme left side and has a second axial device end 15b of the sealing device 15 configured to face the crankcase 2 (FIG. 1). As can be seen in FIG. 2c, flange F defines a retention opening 46a on the left side of fifth packing retainer 46 closer to second device end 15b, and intermediate plate 27 defines a retention opening 46a on the right side of fifth packing retainer 46 closer to first device end 15a.

[0073] The sealing device 15 further includes a purge passage 48 having a first purge passage end 48a and a second purge passage end 48b. The first purge passage end 48a is located on the inner circumferential surface of the central portion of the T-shaped cross section of the fifth packing retainer 46, axially between the two fifth packing rings 47. A first portion of the purge passage 48 adjacent to the first purge passage end 48a is integrally formed with the fifth packing retainer 46, a second intermediate portion of the purge passage 48 is integrally formed with the flange F, and a third portion of the purge passage 48 adjacent to the second purge passage end 48b is formed as a conduit appropriately connected to the flange F. The second purge passage end 48b is connected to a pressurized gas source 49, preferably containing nitrogen. A valve (not shown) for opening and closing the purge passage 48 may also be provided.

[0074] When pressurized gas from the pressurized gas source 49 is introduced into the pressure chamber 46b, pressure is generated in the pressure chamber 46b, which presses the corresponding outer chamfered ring of each fifth packing ring 47 axially against the corresponding central ring. The interacting chamfers force the central chamfered ring radially against the piston rod 8, forming a tight seal. Thus, gas leaking from the first device end 15a (or compression chamber 9, respectively; FIG. 1 ), past the first packing ring 19 and past the second packing ring 21 toward the second device end 15b, can be safely vented through the unobstructed vent path 31. This is due not only to the sealing action of the fifth packing ring 47, but also to the pressure in the pressure chamber 46b, which is preferably higher than the pressure in the region of the first vent path end 31a.

[0075] FIG. 2d shows a different design of the sealing device 15, including a fifth packing retainer 46. In this case, the fifth packing retainer 46 has an L-shaped cross section and only a single retaining opening 46a. The retaining opening 46a faces the second axial device end 15b of the sealing device 15 and is axially defined by a flange F. A single fifth packing ring 47 is disposed within the retaining opening 46a, and this packing ring has a different design from the fifth packing ring 47 of FIG. 2c. In this case, the fifth packing ring 47 is a so-called double-acting DSLP ring assembly. The DSLP ring assembly is essentially a combination of the above-described SLP ring assembly, in which each outer chamfered ring is combined with a single central ring having chamfers on both axial sides. Thus, the fifth packing ring 47 of FIG. 2c has five axially consecutive rings, each with multiple ring segments in the circumferential direction.

[0076] The first purge passage end 48a of the purge passage 48 is connected to a space inside the retaining opening 46a, which is located radially outside the fifth packing ring 47, and which forms a pressure chamber 46b. The axial position of the first purge passage end 48a is preferably the center of the retaining opening 46a, but other positions are also possible. A first portion of the purge passage 48 adjacent to the first purge passage end 48a is integrally formed with the fifth packing retainer 46, and a second, intermediate portion of the purge passage 48 is integrally formed with the flange F. A third portion of the purge passage 48 adjacent to the second purge passage end 48b is located outside the flange F and may be implemented as a conduit. The conduit is connected to a pressurized gas source (not shown). Furthermore, in the embodiment according to FIG. 2d, an unobstructed vent path 31 also passes through the fifth packing retainer 46 and the flange F.

[0077] The purge passage 48 is circumferentially spaced apart from the ventilation passage 31 so as not to interfere with the latter. Similar to FIG. 2c, the first ventilation passage end 31a of the ventilation passage 31 is located between the second packing ring 21 and the fifth packing ring 47 in the axial direction of the sealing device 15. However, the intermediate plate 27 as in FIG. 2c is not required in the embodiment of FIG. 2d. Therefore, the overall axial length of the sealing device 15 according to FIG. 2d may be slightly less than the length of the sealing device according to FIG. 2c. The second packing ring 21 is designed according to the embodiment of FIG. 4c. However, of course, any of the other designs described are also possible.

[0078] When pressurized gas from a pressurized gas source (not shown in FIG. 2d) is introduced into pressure chamber 46b, pressure is generated within pressure chamber 46b. This pressure radially presses the central double-chamfered ring of fifth packing ring 47 against the two adjacent single-chamfered rings. The interacting chamfers press the single-chamfered rings radially against piston rod 8 and axially against the non-chamfered rings, forming a tight seal in both the axial and radial directions. Therefore, gas leaking from first axial device end 15a (or compression chamber 9, respectively; FIG. 1) past first packing ring 19 (not shown) and second packing ring 21 toward second axial device end 15b can safely vent through unobstructed vent path 31. Again, this is due not only to the sealing action of fifth packing ring 47 but also to the pressure within pressure chamber 46b, which is preferably higher than the pressure in the region of first vent path end 31a.

Claims

1. a first axial end (15a) configured to face a cylinder (9) of the reciprocating piston compressor; an opposite second axial end (15b) configured to face a crankcase (2) of the reciprocating piston compressor; a plurality of first packing retainers (18), each having a retaining opening (18a) in which a first packing ring (19) is disposed; and a second packing retainer (20), each having a retaining opening (20a) in which a second packing ring (21) is disposed, the second packing retainer (20) being closer to the second axial end (15b) than the plurality of first packing retainers (18) in an axial direction of the sealing device (15). wherein the second packing ring (21) is an unbroken ring having a continuous inner circumferential sealing surface (21 a), and the second packing ring (21) is configured to seal the piston rod (8) when the reciprocating piston compressor (1) is at rest; the seal device (15) further includes a support passage (28), the support passage (28) having a first support passage end (28 a) and a second support passage end (28 b), and a valve (29) for opening and closing the support passage (28), and the support passage (28) is configured to vent gas leaking past at least one of the plurality of first packing rings (19) in a direction from the first axial device end (15 a) to the second axial device end (15 b) from the first support passage end (28 a) to the second support passage end (28 b). The seal device (15) further includes an unobstructed ventilation passage (31), the ventilation passage (31) having a first ventilation passage end (31 a) and a second ventilation passage end (31 b), the ventilation passage (31) being configured to vent gas leaking past the second packing ring (21) in a direction from the first axial device end (15 a) to the second axial device end (15 b) from the first ventilation passage end (31 a) to the second ventilation passage end (31 b), the seal device (15) further includes at least one third packing retainer (32), the third packing retainer (32) being configured to: a retaining opening (32a) in which a third packing ring (33) is disposed, the at least one third packing retainer (32) being disposed closer to the second axial device end (15b) of the sealing device (15) than the second packing retainer (20), and the first air passage end (31a) being connected to the retaining opening (32a) of the third packing retainer (32) or the first air passage end (31a) being located between the second packing ring (21) and the third packing ring (33) in the axial direction of the sealing device (15).

2. 2. The sealing device (15) according to claim 1, wherein the first support passage end (28a) is connected to the retaining opening (20a) of the second packing retainer (20), or the first support passage end (28a) is located between the second packing ring (21) and the first packing ring (19) of the adjacent first packing retainer (18) in the axial direction of the sealing device (15), or the plurality of first packing retainers (18) includes at least two first packing retainers (18), and the first support passage end (28a) is located in a region of the first packing ring (19) adjacent to the second packing ring (21), or is located between the first packing ring (19) adjacent to the second packing ring (21) in the axial direction of the sealing device (15) and the first axial device end (15a).

3. 2. The sealing device (15) according to claim 1, wherein the second ventilation passage end (31b) of the unobstructed ventilation passage (31) and the second support passage end (28b) of the support passage (28) are connected to a common discharge passage (34) that can be connected to a discharge space (35).

4. 2. The sealing device (15) of claim 1, wherein the valve (29) comprises an electrically controllable actuator (30) that can be controlled by a control unit (17) to open and close the valve (29).

5. The sealing device (15) of claim 1, wherein the valve (29) comprises a sensor (36) configured to generate a sensor value (X) representative of an open state of the valve (29).

6. The second packing ring (21) is formed from a material containing a polymer, and the material has a thermal expansion coefficient (α) that is at least twice the thermal expansion coefficient (αFE) of iron. At or below a predetermined activation temperature, the inner diameter (d_i) of the second packing ring (21) is smaller than the outer diameter (D_a) of the piston rod (8) to be sealed. Therefore, when the sealing device (15) is installed in the reciprocating piston compressor (1), the second packing ring (21) is preloaded in the radial direction, so that the continuous inner peripheral sealing surface (21a) of the second packing ring (21) and the piston rod (8) are sealed.

2. The sealing device (15) of claim 1, wherein a tight seal is formed between the second packing ring (21) and the outer peripheral surface (8 a) of the piston rod (8), and at a given operating temperature, the inner diameter (d_i) of the second packing ring (21) is greater than the outer diameter (D_a) of the piston rod (8), such that, when the sealing device (15) is installed in the reciprocating piston compressor (1), the continuous inner peripheral sealing surface (21 a) of the second packing ring (21) is spaced from the outer peripheral surface (8 a) of the piston rod (8), thereby providing a leakage path axially through the second packing ring (21).

7. The thermal expansion coefficient (α) of the material of the second packing ring (21) is at least 30×10 －６ The sealing device (15) according to claim 6, wherein the sealing device (15) is K-1.

8. 7. The sealing device (15) according to claim 6, wherein the operating temperature is 90°C or higher and / or the activation temperature is 80°C or lower, the operating temperature and the activation temperature being temperatures in the region of the piston rod (8).

9. The second packing ring (21) has a first axial end (21c) and an opposite second axial end (21d), and the second packing ring (21) is disposed in the retaining opening (20a) of the second packing retainer (20) so that the first axial end (21c) faces the first axial device end (15a) of the sealing device (15), and the second packing ring (21) a U-shaped cross section having radially spaced apart inner and outer legs (24, 25), the inner leg (24) being provided with the inner circumferential sealing surface (21 a) of the second packing ring (21) and the outer leg (25) of the second packing ring (21) being provided with a radially outer circumferential surface (21 b), the open side of the U facing axially towards the first axial end (21 c) of the second packing ring (21); an L-shaped cross section having an axial leg (39) and a radial leg (40), the axial leg (39) being provided with the inner circumferential sealing surface (21a) of the second packing ring (21) and the radial leg (40) being provided with the radially outer circumferential surface (21b) of the second packing ring (21), the radial leg (40) being arranged at the second axial end (21d) of the second packing ring (21); a rectangular cross-section, said second packing ring (21) being provided with a plurality of openings (41), each of said openings (41) connecting said first axial end (21c) of said second packing ring (21) to the outer peripheral surface (21b) of said second packing ring (21); The sealing device (15) of claim 1, further comprising one of:

10. 10. The sealing device (15) of claim 9, wherein a plurality of openings (22) are provided on the outer leg (25), each of the plurality of openings (22) connecting an internal space (23) of the U-shaped second packing ring (21) to the radially outer peripheral surface (21 b) of the second packing ring (21), the internal space (23) being located radially between the inner leg (24) and the outer leg (25), and the openings (22) being located spaced apart from the opposing first and second axial ends (21 c, 21 d) of the second packing ring (21).

11. The sealing device (15) of claim 10, wherein the plurality of openings (22) comprise a plurality of elongated or elliptical holes.

12. 12. The sealing device (15) of claim 11, wherein each elongated or elliptical hole has a longitudinal axis (L), a first hole end (22a) and a second hole end (22b) opposite in the direction of the longitudinal axis (L), the first hole end (22a) being located closer to the first axial end (21c) than the second hole end (22b).

13. 10. The sealing device (15) according to claim 9, wherein in an unassembled state of the second packing ring (21), the axial length (b_i) of the inner leg (24) is less than the axial length (b_a) of the outer leg (25).

14. 7. The sealing device (15) of claim 6, wherein the material of the second packing ring (21) is a fiber-reinforced composite material and / or the polymer of the material of the second packing ring (21) comprises at least one of polytetrafluoroethylene, polyphenylene sulfide, polyetheretherketone, polyimide, and polyamide.

15. 1. A reciprocating piston compressor (1), comprising a plurality of cylinders (9), each of which has a reciprocatingly movable piston (10) arranged therein, each piston (10) being connected to a piston rod (8), and for at least one cylinder (9) of the plurality of cylinders (9), a sealing device (15) according to any one of claims 1 to 14 is provided to seal the corresponding piston rod (8), the sealing device (15) being arranged such that a first axial device end (15a) faces the cylinder (9) and a second axial device end (15b) faces a crankcase (2) of the reciprocating piston compressor (1).

16. 16. The reciprocating piston compressor (1) according to claim 15, further comprising a compressor control unit (17) for controlling the operation of the reciprocating piston compressor (1), the compressor control unit (17) being configured to control an electrically controllable actuator (30) of a valve (29) in a support passage (28) depending on an operating condition of the reciprocating piston compressor (1).

17. 17. The reciprocating piston compressor (1) according to claim 16, wherein the reciprocating piston compressor (1) comprises an operating condition sensor configured to detect a sensor value representative of an operating condition of the reciprocating piston compressor (1), and wherein the electrically controllable actuator (30) of the valve (29) of the support passage (28) is configured to control the valve (29) in response to the sensor value, or the compressor control unit (17) is configured to control the electrically controllable actuator (30) of the valve (29) in response to the sensor value.

18. The reciprocating piston compressor (1) has a drive unit (16) for driving the reciprocating piston compressor (1), and the compressor control unit (17) is configured to send a start signal (S_start) to the drive unit (16) to start the operation of the reciprocating piston compressor (1), and to send an open signal (S_open) to the actuator (30) of the valve (29) in the support passage (28) to open the valve (29) simultaneously with the start signal (S_start) or with a predetermined or adjustable open lead time before the start signal (S_start). n), and / or the compressor control unit is configured to send a stop signal (S_stop) to the drive unit (16) to stop operation of the reciprocating piston compressor (1), and to send a close signal (S_close) to the actuator (30) of the valve (29) in the support passage (28) to close the valve (29) simultaneously with the stop signal (S_stop) or after a predetermined or adjustable closing delay time after the stop signal (S_stop).

19. A method for operating a reciprocating piston compressor (1), the reciprocating piston compressor (1) having a plurality of cylinders (9), each of the cylinders (9) having a reciprocatingly movable piston (10) disposed therein, each piston (10) being connected to a piston rod (8), and for each cylinder (9) of the plurality of cylinders (9), a sealing device (15) is provided for sealing the corresponding piston rod (8), the sealing device (15) having a first axial device end (15a) facing the corresponding cylinder (9) and an opposite second axial device end (15b) facing a crankcase (2) of the reciprocating piston compressor (1), at least one sealing device (15) of the plurality of sealing devices comprising a plurality of first packing retainers (18), a plurality of first packing retainers (18), each having a retention opening (18a) in which a first packing ring (19) is disposed, and a second packing retainer (20), each having a retention opening (20a) in which a second packing ring (21) is disposed, the second packing retainer (20) being located closer to the second axial device end (15b) than the plurality of first packing retainers (18) in the axial direction of the sealing device (15), the second packing ring (21) being an uncut ring having a continuous inner circumferential sealing surface (21a), the sealing device (15) further having a support passage (28), the support passage having a first support passage end (28a), a second support passage end (28b), and a valve (29) for opening and closing the support passage (28), The sealing device (15) further includes an unobstructed vent passage (31), the vent passage (31) having a first vent passage end (31a) and a second vent passage end (31b), and the method includes: during operation of the reciprocating piston compressor (1), deactivating the seal between the piston rod (8) and the inner peripheral sealing surface (21 a) of the second packing ring (21) and opening the valve (29) of the support passage (28) to vent gas leaking past at least one of the first packing rings (19) in the direction from the cylinder (9) to the crankcase (2) from the first support passage end (28 a) to the second support passage end (28 b) of the support passage (28) and to vent gas leaking past the second packing ring (21) in the direction from the cylinder (9) to the crankcase (2) from the first vent passage end (31 a) to the second vent passage end (31 b) of the unobstructed vent passage (31); or - activating the seal between the piston rod (8) and the inner peripheral sealing surface (21 a) of the second packing ring (21) during the rest of the reciprocating piston compressor (1) and closing the valve (29) of the support passage (28) to vent gas that may leak past the second packing ring (21) in the direction from the cylinder (9) to the crankcase (2) from the first vent end (31 a) to the second vent end (31 b) of the unobstructed vent passage (31); A method comprising:

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