Cylinder degassing unit and working cylinder

Abstract

The invention relates to a cylinder degassing unit, comprising a basic body, an inner discharge portion, an annular chamber and an outer discharge portion, wherein the basic body is designed to be arranged in a positionally fixed manner on a working cylinder at a wall perforation of a cylinder residual air space and has a concave contour which forms the annular chamber, wherein the inner discharge portion has an inner discharge channel and an inner elastomeric annular body, wherein the inner discharge channel is arranged in the basic body, connects the cylinder residual air space to the annual chamber and has an inner inlet on the cylinder residual air space and an intermediate outlet on the annual chamber, wherein the inner elastomeric annular body covers the intermediate outlet and has preloading and is designed to form a first pressure barrier in a discharge direction and to form a second sealing plane in an inlet direction, wherein the outer discharge portion has an outer discharge channel and an outer elastomeric annular body, wherein the outer discharge channel is arranged in the basic body, connects the annular chamber to an external atmosphere and has an intermediate inlet on the cylinder residual air space and an outer outlet on the annular chamber, wherein the outer elastomeric annular body covers the outer outlet and has preloading and is designed to form a second pressure barrier in a discharge direction and to form a second sealing plane in an inlet direction.

Description

[0001] The invention relates to a cylinder degassing unit for venting a working cylinder and to a working cylinder with such a cylinder degassing unit.

[0002] Particularly in single-acting lifting or pulling cylinders, i.e., working cylinders that are hydraulically actuated in only one direction and are returned to their original position either by load or spring force, dissolved gases and moisture can pass through the piston seal into the empty movement space under the high pressure of the hydraulic fluid. This is exacerbated by the negative pressure created in the empty space during the return movement of the piston, since the empty movement space is subject to a change in volume due to the piston's stroke movement.

[0003] Consequently, the empty space must be vented again during the working movement. This venting occurs to remove such gases and control the pressure conditions in the empty movement space. For this purpose, state-of-the-art technology, for example, provides an air exchange hole that connects the empty movement space to the ambient atmosphere.

[0004] To ensure that no outside air and the associated contamination enters the empty movement space of the cylinder during the alternating piston movements, such an air exchange bore is provided with a functional element, for example, according to the state of the art.

[0005] The current state of the art describes various solutions. Examples include pure filter elements made of porous material or valves with a one-sided self-locking function. This allows the trapped gas to escape. It also prevents backflow of outside air and the dirt particles it contains.

[0006] A technically sophisticated solution is described in utility model application DE 20 2011 102 288 U1. The gas exchange barrier described therein is a check valve with an integrated filter element, designed as a module and thus easy to install. A disadvantage of existing solutions lies in the design complexity. Document DE 20 2005 003835 U1 discloses a single-stage cylinder degassing unit.

[0007] The object of the invention is to provide a cylinder degassing unit with which the venting of a residual cylinder space of a working cylinder can be provided in a structurally simple, cost-effective, particularly reliable manner, and adaptively for different parameters. Furthermore, the object is to provide a working cylinder with such a cylinder degassing unit.

[0008] The problem is solved with respect to the cylinder degassing unit by the features listed in patent claim 1 and with respect to the working cylinder by the features listed in claim 9. Preferred developments emerge from the associated dependent claims.

[0009] According to the invention, the cylinder degassing unit comprises as basic components a base body, an inner discharge section, an annular chamber and a discharge section.

[0010] The cylinder degassing unit is designed as a compact modular component.

[0011] Typically, the cylinder degassing unit is used to vent piston chambers in lifting or pulling cylinders.

[0012] According to the invention, the cylinder degassing unit is based on the fact that a working cylinder has a residual air space that is not pressurized by a hydraulic pressure medium and whose volume changes as a result of the stroke of the working cylinder's piston. A wall perforation is formed on the working cylinder, providing a connection between the residual air space and the outside atmosphere, which is routed via the cylinder degassing unit.

[0013] The base body is designed for a fixed position on a hydraulic working cylinder, hereinafter also referred to as the working cylinder. When used as intended, the base body is arranged at least partially in the wall perforation of the working cylinder.

[0014] The base body has a concave contour, which preferably forms the annular chamber in the form of a circumferential annular gap or a circumferential annular groove. The concave contour is preferably designed as a diameter taper of the base body and, together with the inner surface of the wall perforation, forms a circumferential cavity that provides the annular chamber.

[0015] The volume of the annular chamber controls the storable air volume and the outgoing air flow. The annular chamber also functions as a pressure chamber.

[0016] According to the invention, the inner discharge section has an inner discharge channel and an inner elastomeric ring body.

[0017] The inner discharge channel is arranged in the base body and can, in particular, be provided as a bore. The inner discharge channel connects the residual cylinder air space with the annular chamber. For this purpose, the inner discharge channel has an inner inlet at one end, located at the residual cylinder air space. At the other end of the inner discharge channel, there is an intermediate outlet at the annular chamber.

[0018] The inner elastomeric annular body covers the intermediate outlet and has a prestress. The inner elastomeric annular body is designed to form a first pressure barrier in an outlet direction and a second sealing plane in an inlet direction.

[0019] The outer discharge section is constructed similarly to the inner discharge section. It is also located in the base body and has an outer discharge channel and an outer elastomeric annular body.

[0020] The outer discharge channel connects the annular chamber to the outside atmosphere. For this purpose, the preferably inclined outer discharge channel has an intermediate inlet at the cylinder's residual air space at its first end and an outer outlet to the outside atmosphere at its opposite end. The outer elastomeric annular body covers the outer outlet. Like the inner elastomeric annular body, the outer elastomeric annular body also has a prestress and is designed to form a second pressure barrier in the discharge direction and a first sealing plane in the inlet direction. When the second pressure barrier is overcome, the discharge medium escapes into the low-pressure region of the atmosphere.

[0021] For the purposes of the present invention, the discharge direction is understood to be the direction from inside to outside, i.e., from the residual cylinder air space toward the outside atmosphere. The discharge direction describes the possible path of a discharge medium from the residual cylinder air space into the outside atmosphere.

[0022] The inlet direction is understood to be the direction opposite to the outlet direction.

[0023] The order of designation of the pressure barriers follows the discharge direction and the order of designation of the sealing levels follows the inlet direction.

[0024] The discharge medium is primarily a gaseous medium such as air or gases that are released from the hydraulic pressure medium due to pressure differences, or sometimes also a hydraulic pressure medium that can enter the residual cylinder air space in small quantities by wiping it off the inner surface of the working cylinder as a result of piston movement or as a leakage flow, or even condensate. The discharge medium is sometimes also referred to as gas or air below.

[0025] Depending on the operating condition, the sealing levels make it possible to divide a high-pressure area in the cylinder residual space and the inner discharge channel, a medium-pressure area after the inner elastomeric ring body in the ring chamber and the outer discharge channel up to the outer ring body and then a low-pressure area in the outside atmosphere.

[0026] The material hardness, the preload after being pulled onto the base body and the wall thickness of the respective elastomer ring body as well as the opening cross-section of the intermediate outlet or the outer outlet define the pressure required for the discharge medium to flow out.

[0027] Once the defined pressure in the inner discharge channel is reached, the inner elastomeric ring expands, allowing the discharge medium to escape into the annular chamber. Due to the closing force created by the preload, a defined pressure remains in the residual cylinder air space after the discharge.

[0028] The same applies to the outer outlet. Once the minimum pressure is reached, the outer elastomeric ring expands, opening the outer outlet. The gas can escape from the intermediate space via the outer discharge channel and the outer outlet into the atmosphere. The preload of the outer elastomeric ring defines the residual pressure at which it closes the outer outlet. This allows a defined pressure to be maintained in the annular chamber, also referred to here as the intermediate pressure zone.

[0029] The air distribution module is further designed according to the invention to have a full discharge operating state, a partial discharge operating state and a closed operating state.

[0030] In the full discharge operating state, there is an overpressure in the cylinder residual air space relative to the outside atmosphere. This pressure overcomes the first and second pressure barriers and leads to the discharge medium escaping from the cylinder residual air space via the inner discharge section, the annular chamber, and the outer discharge section into the outside atmosphere. The described stepped pressure conditions of high pressure in the cylinder residual air space, medium pressure in the annular chamber, and low pressure in the outside atmosphere exist here.

[0031] In the partial discharge operating state, there is an overpressure in the residual cylinder air space relative to the annular chamber. This pressure overcomes the first pressure barrier, and media escapes from the residual cylinder air space via the inner discharge section into the annular chamber. In the partial discharge operating state, however, the pressure difference is not so great that the second pressure barrier is also overcome. The first sealing level remains closed.

[0032] In the closed operating state, neither the first nor the second pressure barrier is overcome. The inner discharge section seals the remaining cylinder air space from the annular chamber, and the outer discharge section seals the annular chamber from the outside atmosphere.

[0033] With the cylinder degassing unit according to the invention, a surprisingly simple structural solution was found that provides several particular advantages.

[0034] With particularly simple and robust means, both a valve effect and pressure control are achieved in functional integration.

[0035] Advantageously, a two-stage discharge path is provided, first from the residual cylinder air space into the annular chamber and then secondly from there into the atmosphere, with two barrier-forming elastomeric annular bodies. This achieves a lock function. Thus, the residual cylinder air space is not directly connected to the cylinder's surroundings. This, in turn, leads to increased protection of the residual cylinder air space against the harmful influences of the atmospheric environment. Dirt particles, harmful gases, or aerosols are kept out in two stages and cannot penetrate the cylinder and damage it.

[0036] Advantageously, the outer discharge section already shields the annular chamber from contamination, so that the inner elastomer ring in particular is particularly protected and its functionality is not impaired even under problematic external atmospheric conditions.

[0037] Equally advantageous is the defined residual pressure in the annular chamber enabled by the invention. This residual pressure can achieve several advantageous effects in functional integration.

[0038] The residual pressure is, on the one hand, one stage of a beneficial pressure cascade, providing an intermediate pressure level between a possible maximum pressure in the residual cylinder air space and a merely atmospheric pressure in the outside atmosphere. The total pressure difference is thus advantageously divided between two stages.

[0039] Furthermore, there is the advantage that even if the cylinder residual air space is under pressure compared to the outside atmosphere, an overpressure between the annular chamber and the outside atmosphere prevents outside air from penetrating into the annular chamber.

[0040] By applying the residual pressure to the inner piston ring - viewed in the inlet direction - the residual pressure supports the sealing effect of the inner piston ring in its closed operating state.

[0041] This allows for a vacuum to be created during the piston's reciprocating movement, increasing the volume of the remaining cylinder air space, without the risk of introducing outside air and contaminants. This supports the piston's working movement and makes it more energy-efficient.

[0042] Furthermore, the transition of the outflowing air during rapid piston movements into at least two pressure stages advantageously reduces noise pollution. The discharge flow is buffered by the annular chamber. This avoids the loud hissing noises that occur in conventional cylinders that discharge directly from the high-pressure to the low-pressure range.

[0043] Another advantage is the structural simplicity. The base body can be easily provided as a turned-milled part. The elastomer ring bodies can be designed as simple hose sections or rubber rings. This has the advantage of being particularly robust. Furthermore, the ring bodies can be easily replaced and renewed as needed. The base body can advantageously be arranged in a wall perforation such that it protrudes axially outwards with the outer discharge section. This allows the outer elastomer ring body, which is potentially subject to greater environmental stress, to be replaced without dismantling the cylinder degassing unit from the wall perforation and, ideally, even without tools.

[0044] Furthermore, by selecting the preload of the elastomeric ring bodies and the desired pressures in the residual cylinder air space and in the ring chamber, it is possible to specify the application-specific pressures using the same base body with the same dimensions of the discharge channels and outlets. Further adaptation is also possible by changing the cross-sections of the outlets.

[0045] In a first advantageous development of the cylinder degassing unit according to the preceding claim, the base body has a cylindrical basic shape and is received in a wall hole of the cylinder residual air space designed as a hollow cylindrical bore.

[0046] Advantageously, the base body can be designed with an external thread that engages a corresponding internal thread in the wall hole of the working cylinder. However, other connections, such as a press fit, are also possible.

[0047] According to a further advantageous development, the inner elastomeric ring body and the outer elastomeric ring body are of identical construction.

[0048] This refinement enables further design simplification and optimization. If different differential pressures are to be provided using the inner elastomeric ring body at the intermediate outlet as the first pressure barrier and the outer elastomeric ring body at the outer outlet as the second pressure barrier, this is still possible, for example, by selecting different cross-sections for the respective outlets of the discharge channels or different diameters for the bearing seats of the elastomeric ring bodies.

[0049] In another advantageous development of the cylinder degassing unit, the annular chamber is formed by the concave contour of the base body and an inner shell of the wall perforation.

[0050] The concave contour of the base body can be created inexpensively and easily, preferably by turning. However, milling a non-radially symmetrical concave contour is also possible. The geometric design of the concave contour of the base body, in conjunction with the usually cylindrical inner shell, defines the shape and volume of the annular chamber. In this way, the pressure conditions and flow behavior can be specifically influenced.

[0051] In another advantageous development of the cylinder degassing unit, the annular chamber is designed for an overpressure relative to the outside atmosphere in the closed operating state.

[0052] The overpressure creates a lock function in the annular chamber. The ingress of dirt or other contaminated air is prevented by the constant overpressure. The overpressure in the annular chamber remains constant during the piston stroke, in every possible piston position, and at every possible pressure state of the residual cylinder air space. The overpressure in the annular chamber prevents outside air and contaminants from entering the annular chamber and supports the sealing effect of the inner elastomeric annular body in its function as a second sealing level.

[0053] In another advantageous development of the cylinder degassing unit, it has an inner O-ring which is designed for a sealing engagement with the wall perforation and forms a sealing plane between the cylinder residual air space and the annular chamber.

[0054] This further development demonstrates a way to further simplify the design and increase the effectiveness of the pressure control function and valve function.

[0055] In another advantageous development of the cylinder degassing unit, it has an outer O-ring which is designed for a sealing engagement with the wall perforation and forms a sealing plane between the annular chamber and the outside atmosphere.

[0056] Here too - in a similar manner to the inner O-ring - a further structural simplification and an increase in the effectiveness of the pressure control function and valve function is provided.

[0057] In another advantageous development of the cylinder degassing unit according to the preceding claims, it has a further inner discharge section and a further annular chamber, which are functionally arranged in series with the inner discharge section and the annular chamber.

[0058] The further training is based on another special advantage: the multi-level structure can be further expanded with a third or further level.

[0059] Depending on the application, with different piston speeds and applied pressure ranges, additional pressure stages can be connected in series within the cylinder degassing unit. This allows damping, noise generation, and the behavior of the outflowing gases to be controlled and further improved. Furthermore, the pressure difference required between the respective pressure stages is advantageously reduced while maintaining the same overall pressure difference between the residual cylinder air space and the outside atmosphere.

[0060] A further aspect of the present invention relates to a working cylinder. This cylinder has a residual air space, which is associated with a wall perforation that provides a passage.

[0061] In addition, this working cylinder according to the invention has a cylinder degassing unit according to the invention, which is arranged on the wall perforation. The cylinder degassing unit is designed according to one of claims 1 to 8.

[0062] The working cylinder according to the invention is advantageously designed as a single-acting hydraulic working cylinder that is actuated by a fluid in only one working direction. The empty movement space, defined by the piston and its piston seal, forms the residual cylinder air space. For example, the empty movement space is the piston chamber in the case of a pull cylinder and the piston rod chamber in the case of a pressure cylinder. Otherwise, the working cylinder is designed in a conventional manner.

[0063] The invention is illustrated by way of example with reference to Fig. 1 schematic sectional view of the working cylinder Fig. 2schematic sectional view of the cylinder degassing unit explained in more detail.

[0064] Identical reference symbols in the various figures refer to identical features or components. These reference symbols are used in the description even if they are not shown in the respective figure.

[0065] The Figure 1 shows a schematic sectional view of an embodiment of the working cylinder 8 with the mounted cylinder degassing unit 7.

[0066] In the present embodiment, the working cylinder 8 is a hydraulic pull cylinder. It has a lateral pressure medium connection in the cylinder wall through which the piston rod chamber can be pressurized. This applies pressure to the annular surface of the piston facing the guide closure part, and the piston, with the connected piston rod, performs an inward stroke movement. The residual cylinder air space is not pressurized with the pressure medium but remains empty. As a result of the stroke movement, the volume of the residual cylinder air space 5 changes.

[0067] The cylinder degassing unit 7 is connected to the residual cylinder air space 5 in the exemplary embodiment and is placed in a widened section of the wall perforation 5.1, which is designed as a bore and is associated with the residual cylinder air space 5 and forms a single pressure chamber with it. Due to this arrangement, the cylinder degassing unit 7 can vent the residual cylinder air space 5 during a retracting piston movement. Further details of the cylinder degassing unit 7 are shown below. Fig. 2

[0068] The Figure 2 shows a schematic sectional view of the cylinder degassing unit 7.

[0069] This consists of the base body 1, an inner discharge section 2 and an outer discharge section 4. Furthermore, the annular chamber 3 is formed by the concave contour 1.1 of the base body 1.

[0070] When properly installed, the inner discharge section 2 is arranged in the wall perforation 5.1 of the working cylinder, designed as a bore, and its inner discharge channel 2.1 is pressure-connected to the cylinder residual air space 5. The inner discharge channel 2.1 begins with the inner inlet 2.3 at the cylinder residual air space 5 at the bore and leads to the intermediate outlet 2.4, with which it leads into the annular chamber 3. The intermediate outlet 2.4 is covered by the inner elastomeric annular body 2.2, which in the exemplary embodiment is designed as a clamped rubber ring or plastic ring with a flat cross-section. The sealing and pressure separation between the cylinder residual air space 5 and the annular chamber 3 is achieved in the exemplary embodiment by the inner O-ring 9.

[0071] The outer discharge section 4 is designed analogously and consists of the outer discharge channel 4.1 and the outer elastomeric annular body 4.2. Designed as a bore, the outer discharge channel 4.1 penetrates the base body 1. The outer discharge channel 4.1 has a pressure connection to the annular chamber 3 via the intermediate inlet 4.3 and ends in the discharge direction with the outer outlet 4.4 on the outer elastomeric annular body 4.2, thus leading to the outside atmosphere 6, which is not part of the device according to the invention.

[0072] For an active lifting movement of the pull cylinder in the exemplary embodiment, the hydraulic pressure medium is directed into the piston rod chamber, where it moves the piston toward the piston crown. The volume in the piston chamber decreases, and the pressure of a discharge medium accumulated there increases. The piston chamber here is the residual cylinder air space 5.

[0073] In the event of an overpressure in the cylinder residual air space 5 which is so great that it overcomes the prestress of the elastomeric ring body 2.2, the gases to be discharged flow via the inner inlet 2.3 into the inner discharge channel 2.1 and flow through this to the intermediate outlet 2.4 and from there pass the inner elastomeric ring body into the ring chamber 3. In the exemplary embodiment, the ring chamber 3 is a circumferential hollow space which is formed by the concave contour 1.1 of the base body 1 and by the wall of the bore, shown schematically here by the vertical dashed lines.

[0074] The intermediate outlet 2.3 is closed by the inner elastomeric ring body 7, and only at a certain pressure does the inner elastomeric ring body 7 open. It transitions from the high-pressure area in the working cylinder into its residual cylinder air space 5 into the medium-pressure area of an annular chamber 3. The annular chamber 3 is filled with the discharge medium due to the pressure difference.

[0075] The gases then flow into the outer discharge section 4. Via the intermediate inlet 4.3, the gases flow into the outer discharge channel 4.1. The outer outlet 4.4 is closed by the outer elastomeric ring body 4.2. This also opens at a certain gas pressure, allowing it to flow into the outside atmosphere, the low-pressure region.

[0076] During a passive stroke movement of the piston in the extension direction, the volume in the piston chamber increases again and the pressure drops. Both elastomeric annular bodies 2.2, 4.2 rest against the respective associated outlets 2.4, 4.4, closing them and thus forming a first and a second sealing level. Even if the pressure in the residual cylinder air chamber 5 is lower than in the outside atmosphere 6, a relative overpressure remains in the annular chamber 3 compared to the outside atmosphere 6 due to the closure of the intermediate outlet 2.4 by the inner elastomeric annular body 2.2 - as a second sealing level - and due to the preload of the outer elastomeric annular body 4.2 at the outer outlet as a second pressure barrier. This reliably prevents the penetration of outside air. The closed operating state exists.

[0077] The circles surrounding reference numerals 5, 3, and 6 indicate the different pressure zones. Furthermore, the horizontal dashed lines schematically show the boundaries of the different pressure zones. Reference symbols used

[0078] 1Main body 1.1Concave contour 2Inner discharge section 2.1Inner discharge channel 2.2Inner elastomeric ring body 2.3Inner inlet 2.4Intermediate outlet 3Annular chamber 4Outer discharge section 4.1Outer discharge channel 4.2Outer elastomeric ring body 4.3Intermediate inlet 4.4Outer outlet 5Cylinder residual air space 5.1Wall perforation 6External atmosphere 7Cylinder degassing unit 8Working cylinder 9Inner O-ring

Claims

1. A cylinder degassing unit (7), comprising a basic body (1), an inner discharge portion (2), an annular chamber (3) and an outer discharge portion (4), wherein the basic body (1) is designed to be arranged in a positionally fixed manner on a working cylinder (8) at a wall perforation (5.1) of a cylinder residual air space (5) and has a concave contour (1.1) which forms the annular chamber (3), wherein the inner discharge portion (2) has an inner discharge channel (2.1) and an inner elastomeric annular body (2.2), wherein the inner discharge channel (2.1) is arranged in the basic body (1) and is designed to connect the cylinder residual air space (5) to the annular chamber (3), and comprises an inner inlet (2.3), which is connectable to the cylinder residual air space (5), and an intermediate outlet (2.4) at the annular chamber (3), wherein the inner elastomeric annular body (2.2) covers the intermediate outlet (2.4) and is preloaded and designed to form a first pressure barrier in a discharge direction and to form a second sealing plane in an inlet direction, wherein the outer discharge portion (4) comprises an outer discharge channel (4.1) and an outer elastomeric annular body (4.2), wherein the outer discharge channel (4.1) is arranged in the basic body (1) and is designed to connect the annular chamber (3) to an outside atmosphere (6), and comprises an intermediate inlet (4.3) at the annular chamber (3) and an outer outlet (4.4), which is connectable to the outside atmosphere (6), wherein the outer elastomeric annular body (4.2) covers the outer outlet (4.4) and is preloaded and designed to form a second pressure barrier in an outlet direction and a first sealing plane in an inlet direction, wherein the cylinder degassing unit (7) is designed to comprise a complete discharge operating state, a partial discharge operating state and a closing operating state, and wherein in the complete discharge operating state, there is a positive pressure in the cylinder residual air space (5) relative to the outside atmosphere (6), which overcomes the first and second pressure barriers and provides a media outlet from the cylinder residual air space (5) via the inner discharge portion (2), the annular chamber (3) and the outer discharge portion (4) into the outside atmosphere (6), wherein in the partial discharge operating state, there is a positive pressure in the cylinder residual air space (5) relative to the annular chamber (3), which exclusively overcomes the first pressure barrier and provides a media outlet from the cylinder residual air space (5) via the inner discharge portion (2) into the annular chamber (3), and wherein the outer discharge portion (4) seals the annular chamber (3) to the outside atmosphere (6), and wherein, in the closing operating state, neither the first nor the second pressure barrier is overcome and the inner discharge portion (2) seals the cylinder residual air space (5) against the annular chamber (3) and the outer discharge portion (4) seals the annular chamber (3) against the outside atmosphere (6).

2. The cylinder degassing unit (7) according to claim 1, characterized in that the basic body (1) has a cylindrical basic shape and is designed to be accommodated in a wall perforation, formed as a hollow cylindrical bore hole, to the cylinder residual air space (5).

3. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that the inner and the outer elastomeric annular bodies (2.2, 4.2) are identical in construction.

4. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that the annular chamber (3) is formed by the concave contour (1.1) of the basic body (1) and an inner jacket of the wall perforation.

5. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that in the closing operating state the annular chamber (3) is designed for a positive pressure relative to the outside atmosphere (6).

6. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that it has an inner O-ring (9) which is designed for a sealing contact to the wall perforation (5.1) and forms a sealing plane between the cylinder residual air space (5) and the annular chamber (3).

7. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that it has an outer O-ring which is designed for a sealing contact to the wall perforation (5.1) and forms a sealing plane between the annular chamber (3) and the outside atmosphere (6).

8. The cylinder degassing unit (7) according to one of the preceding claims, characterized in that it has a further inner discharge portion and a further annular chamber, which are functionally arranged in series to the inner discharge portion (2) and the annular chamber (3).

9. A working cylinder (8), comprising the cylinder residual air space (5) and a wall perforation (5.1), and comprising a cylinder degassing unit (7) that is arranged at the wall perforation (5.1), wherein the cylinder degassing unit (7) is designed according to one of the claims 1 to 8.

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