PNEUMATIC DEVICE WITH SEALING MEANS AND METHOD THEREFOR

Abstract

A pneumatic device (1) has at least one venting path (10) for venting the pneumatic device (1) in an outflow direction (R1). The venting path (10) includes a first volume (12), through which a flow can pass, a first compressed-air passage (14), and a sealing mechanism (18). The first compressed-air passage (14) pneumatically connects the first volume (12) to a pressurized part (16) of the pneumatic device (1). The sealing mechanism (18) changes between a normal state (Z1) and a sealing state (Z2). In the normal state (Z1) a flow can pass through the first compressed-air passage (14) both in the outflow direction (R1) and in an oppositely directed inflow direction (R2). In the sealing state (Z2) a flow can pass through the first compressed-air passage (14) only in the outflow direction (R1).

Claims

1. A pneumatic device (1) comprising: at least one venting path (10) for venting the pneumatic device (1) in an outflow direction (R1), wherein the venting path (10) comprises: a first volume (12), through which a flow can pass; a first compressed-air passage (14) pneumatically connecting the first volume (12) to a pressurized part (16) of the pneumatic device (1); a sealing mechanism (18) that changes at least between a normal state (Z1) and a sealing state (Z2); wherein in the normal state (Z1) of the sealing mechanism (18) a flow passes through the first compressed-air passage (14) both in the outflow direction (R1) and in an oppositely directed inflow direction (R2), and wherein in the sealing state (Z2) of the sealing means (18) a flow passes through the first compressed-air passage (14) only in the outflow direction (R1).

2. The pneumatic device (1) as claimed in claim 1, wherein the sealing mechanism (18) changes from the normal state (Z1) into the sealing state (Z2) when a fluid (F) in the first volume (12) and/or in the first compressed-air passage (14) exceeds a threshold value (S).

3. The pneumatic device (1) as claimed in claim 2, wherein the fluid (F) is water (W) and the threshold value is a height of the water.

4. The pneumatic device (1) as claimed in claim 1 , wherein the sealing mechanism (18) is arranged in the first compressed-air passage (14).

5. The pneumatic device (1) as claimed in claim 1 , wherein the sealing mechanism (18) comprises a sealing member (20) and a seal seat (23), wherein the sealing member (20) abuts the seal seat (23) in a sealing manner in the sealing state (Z2).

6. The pneumatic device (1) as claimed in claim 5, wherein the sealing member (20) floats on water (W).

7. The pneumatic device (1) as claimed in claim 5 , wherein the sealing member (20) has a mean density of 900 kg/m.sup.3 or less.

8. The pneumatic device (1) as claimed in claim 5 , wherein the seal seat (23) points downstream in the outflow direction (R1), and wherein the sealing member (20) is arranged downstream of the seal seat (23) in the outflow direction (R1).

9. The pneumatic device (1) as claimed in claim 5 , wherein the sealing member (20) is movable between a first position (P1) and a second position (P2), wherein the sealing member occupies the first position (P1) in the normal state (Z1) and the second position (P2) in the sealing state (Z2).

10. The pneumatic device (1) as claimed in claim 9, wherein the first position (P1) is downstream of the second position (P2) in the outflow direction (R1).

11. The pneumatic device (1) as claimed in claim 9 , wherein the sealing mechanism (18) includes a guide (24) for the sealing member (20), wherein the sealing member (20) moves between the first position (P1) and the second position (P2) along the guide (24), wherein the seal seat is situated at an upstream end (26) of the guide (24) in the outflow direction (R1).

12. The pneumatic device (1) as claimed in claim 11, wherein the guide (24) includes a stop (30) that prevents the sealing member (20) from coming out of the guide (24), wherein the stop (30) is disposed at a downstream end (28) of the guide (24) in the outflow direction (R1).

13. The pneumatic device (1) as claimed in claim 11 , wherein the sealing member (20) is a ball (32) and the guide (24) is a ball cage (34).

14. The pneumatic device (1) as claimed in claim 13, wherein the ball cage (34) includes a plurality of guide bars (38) extending in the outflow direction (R1).

15. The pneumatic device (1) as claimed in claim 1 , wherein the first compressed-air passage (14) has a cross-sectional width with dimensions that are smaller than a length of the compressed-air passage defined in the outflow direction.

16. The pneumatic device (1) as claimed in claim 1 ,the first compressed-air passage (14) is arranged vertically at least in some portions in an installation situation of the pneumatic device (1).

17. The pneumatic device (1) as claimed in claim 16 , wherein the pressurized part (16) of the pneumatic device (1) is arranged above the first volume (12) in an installation situation of the pneumatic device (1).

18. The pneumatic device (1) as claimed in claim 1 , wherein the venting path (10) further comprises a second compressed-air passage (40) pneumatically connecting the first volume (12) to an external environment (U) of the pneumatic device (1).

19. The pneumatic device (1) as claimed in claim 1 , wherein the pneumatic device (1) is a pneumatic brake system (B) or a relay valve (R).

20. A method for preventing fluid from entering a pressurized part (16) of a pneumatic device (1) in an inflow direction (R2), the pneumatic device having at least one venting path (10), the venting path (10) including a first volume (12), through which a flow can pass, a first compressed-air passage (14) pneumatically connecting the first volume (12) to a pressurized part (16) of the pneumatic device (1), and a sealing mechanism (18); wherein the method comprises: providing fluid (F) above a threshold value (S) in the first volume (12) and/or in the first compressed-air passage (14) of the pneumatic device (1); bringing the sealing mechanism (18) from a normal state (Z1) into a sealing state (Z2); wherein in the normal state (Z2) a flow passes through the first compressed-air passage (14), which pneumatically connects the first volume (12) to the pressurized part (16) of the pneumatic device (1), both in the inflow direction (R2) and in an oppositely directed outflow direction (R1); and wherein in the sealing state (Z2) a flow passes through the first compressed-air passage (14) only in the outflow direction (R1).

21. The method as claimed in claim 20, wherein the fluid (F) brings the sealing mechanism (18) into the sealing state (Z2) by exceeding the threshold value (S) in the first volume (12).

22. The method as claimed in claim 21, further comprising: venting the pressurized part (16) of the pneumatic device (1) in the outflow direction (R1) in both the normal state and the sealing state.

23. A method for installing the pneumatic device (1) as claimed in claim 1, wherein the method comprises: arranging the sealing mechanism (18) in the first compressed-air passage (14) of the pneumatic device (1); wherein the sealing mechanism (18) is arranged in the first compressed-air passage (14) between the first volume (12) and the pressurized part (16) and arranged to be able to change at least between the normal state (Z1) and the sealing state (Z2); wherein in the normal state (Z1) a flow can pass through the first compressed-air passage (14) both in an outflow direction (R1) and in an oppositely directed inflow direction (R2); and wherein in the sealing state (Z2) a flow can pass through the first compressed-air passage (14) only in the outflow direction (R1); wherein the sealing mechanism (18) is a separate structural unit configured for installation or retrofitting in existing pneumatic devices as a separate sealing mechanism.

24. The method as claimed in claim 20, further comprising using a ball (32) to establish the sealing state (Z2) of the pneumatic device (1), starting from the normal state (Z1) of the pneumatic device (1), wherein the sealing state (Z2) prevents fluid (W) from entering the pressurized part (16) of the pneumatic device (1), when the fluid (F) in the first volume and/or in the first compressed-air passage (12) exceeds the threshold value (S).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows a cross-section through a pneumatic device of an exemplary embodiment according to an aspect of the disclosure, wherein a sealing member is arranged in a second position and a sealing state.

[0032] FIG. 2 shows the cross-section from FIG. 1, wherein a first position and a normal state of the sealing member is illustrated by a broken line.

[0033] FIG. 3 shows a guide for a sealing member, as can be used in the exemplary embodiment of FIGS. 1 and 2 and in further exemplary embodiments according to aspects of the disclosure.

[0034] FIG. 4 shows a cross-section of the sealing member according to FIG. 3.

DETAILED DESCRIPTION

[0035] In the following text, the first, second, third, and fourth aspects of the present disclosure will be explained in relation to an exemplary embodiment, shown in particular in FIGS. 1 and 2, of a pneumatic device according to the first aspect of the disclosure. As will be apparent from the following description, the pneumatic device shown is suitable for, but not limited to, carrying out a method according to the second and/or fourth aspect of the disclosure and/or being installed by way of a method according to the third aspect of the disclosure. It will be appreciated that the features and advantages described in connection with FIGS. 1-4 are applicable to all the aspects and sub-aspects of the disclosure which have been described above.

[0036] FIGS. 1 and 2 show a pneumatic device 1 having a venting path 10 in an installation situation. The venting path 10 is adapted to vent a pressurized part 16 of the pneumatic device 1. For this purpose, a first volume 12 of the pneumatic device 1 is pneumatically connected via a first compressed-air passage 14 to a pressurized part 16 of the pneumatic device 1. A second compressed-air passage 40 pneumatically connects an external environment U of the pneumatic device 1 to the first volume 12. On venting of the pressurized part 16, compressed air flows from the pressurized part 16 through the first passage 14, through the first volume 12, and then through the second compressed-air passage 40 into the environment U. The flow path of the compressed air so described predominantly follows an outflow direction R1 indicated diagrammatically in FIGS. 1 and 2 by way of an arrow with two bends.

[0037] In FIG. 1, a fluid F with fluid level H1 is present in the environment U, so that the entire pneumatic device 1 is arranged below the fluid level H1 and is surrounded by fluid F. The pneumatic device 1 has a threshold value S for the fluid F, which in the exemplary embodiment shown is arranged in the region of the second compressed-air passage 40. Because the second compressed-air passage 40 is arranged beneath the fluid level H1, fluid F could enter the first volume 12 through the compressed-air passage 40. As can be seen in FIG. 1, the fluid level H1 of the fluid F is above the threshold value S. The fluid F therefore fills the first volume 12 completely, and the first compressed-air passage 14, at least to the extent that the fluid F therein exceeds the threshold value S.

[0038] FIG. 2 shows the pneumatic device 1 from FIG. 1, wherein in this illustration a fluid F is present in the environment U of the pneumatic device 1 with a second fluid level H2. For reasons of legibility, FIG. 2 is not provided with all the reference numerals that are included in FIG. 1, but it will be appreciated that FIGS. 1 and 2 show the same pneumatic device 1. The fluid level H2 is below the threshold value S but above the second compressed-air passage 40. The fluid F therefore fills the first volume 12 almost completely up to the fluid level H2, while the first compressed-air passage 14 is largely free of fluid F. The threshold value S is thus not reached by the fluid F in the pneumatic device 1.

[0039] In the exemplary embodiment of FIGS. 1 and 2, the pneumatic device 1 includes a sealing mechanism 18 which is arranged in the first compressed-air passage 14. The first compressed-air passage 14 shown is in particular a channel-shaped, cylindrical connecting portion between the first volume 12 and the pressurized part 16. In this context, channel-shaped means that the length L of the first compressed-air passage 14 is greater than the diameter D of its cross-section. The outflow direction R1, and the inflow direction R2 explained below, are defined in the region of the first compressed-air passage 14 by the geometry thereof and run therein along the length L. The sealing mechanism 18 shown extends over the entire length L of the first compressed-air passage 14.

[0040] The sealing mechanism 18 in FIGS. 1 and 2 further comprises a sealing member 20, a guide 24 for the sealing member 20, and a seal seat 23 provided at an end 26 of the guide 24 that is situated upstream in the outflow direction R1. The sealing member 20 is designed to abut the seal seat 23 in a sealing manner in a sealing state Z2.

[0041] In the exemplary embodiment shown, the sealing member 20 is a hollow ball 32 and the guide 24 is a ball cage 34 adapted to the ball 32. The ball 32 is movable along the ball cage 34 between a first position P1 (shown in FIG. 2) and a second position P2 (shown in FIG. 1). The seal seat 23 is formed by a circumferential surface 22 extending around the ball cage 34 in the interior thereof. The circumferential surface 22 largely corresponds to the lateral surface of a truncated cone, and at the end thereof that is situated upstream in the outflow direction R1 there is arranged an edge 21. The seal seat 23 faces downstream in the outflow direction R1, that is to say a normal N to the circumferential surface 22 has at least one component Nv which is parallel to and aligned with the outflow direction R1 (see FIG. 4).

[0042] As described above, it is advantageous for reliable operation of the pneumatic device 1 that the fluid F is reliably prevented from entering the pressurized part 16 of the pneumatic device 1. In particular in the case of a first fluid level H1 as in FIG. 1, the fluid F, without appropriate counter-measures, could rise in the inflow direction R2 from the environment U through the first volume 12, through the first compressed-air passage 14, into the pressurized part 16. The inflow direction R2 is shown diagrammatically in FIG. 1 as an arrow running largely parallel to the outflow direction R1.

[0043] In order to prevent water from entering the pressurized part 16 in this way, the sealing mechanism 18 is designed to change at least between a normal state Z1 and a sealing state Z2. In FIG. 1, the sealing mechanism 18 is shown in the sealing state Z2, in which the ball 32 is in the second position P2. Position P2 is located at the end 26 of the guide 24 that is situated upstream in the outflow direction R1. In this second position P2, the ball 32 abuts the seal seat 23, specifically the edge 21, in a sealing manner, so that a flow through the first compressed-air passage 14 in the inflow direction R2 is prevented. A closed cavity 33 preferably provided inside the ball 32 reduces the mean density of the ball compared to the density of the material of which the ball 32 is made to such an extent that the ball 32 is capable of floating on the fluid F. Alternatively, a filling material with a low density can be provided, in order to increase the dimensional stability of the ball 32. Because the ball 32 is arranged in the ball cage 34 downstream of the seal seat 23 in the outflow direction R1, the resulting buoyant force F.sub.A presses the ball 32 in a sealing manner against the edge 21 of the seal seat 23. When venting of the pressurized part 16 is carried out in the sealing state Z2, a pushing force F.sub.P on the ball 32 which results from an excess pressure P.sub.Ü in the pressurized part 16 and is oppositely directed to the buoyant force F.sub.A can thus exceed the amount thereof. The ball 32 is thus lifted from the seal seat 23 by the pushing force F.sub.P for the duration of the venting process so that compressed air can be vented from the pressurized part 16 in the outflow direction R1. The ingress of fluid is then prevented by the outflowing air. In the sealing state Z2, a flow can thus pass through the first compressed-air passage 14 only in the outflow direction R1. In other words, the sealing mechanism 18 in the sealing state Z2 performs the function of a check valve and in that state preferably forms such a valve.

[0044] It is preferred that the size of the closed cavity 33 in the ball 32 is adapted according to the density of the material of a shell 35 of the ball 32 and the density of the fluid F against which the pressurized part 16 is to be sealed, in order to achieve a mean density which allows the ball 32 to float on the fluid F. It is further preferred that the sealing member 20 is designed, by corresponding adaptation of its mean density, so that the ball 32 lifts from the seal seat 23 at a specific excess pressure P.sub.Ü. It is preferred that the material of the ball 32 is matched to the material of the ball cage 34 and/or of the seal seat 23, in order to achieve the desired sealing properties. The ball 32 and the ball cage 34 and/or the seal seat 23 are preferably made either of the same material or of different materials. Suitable materials for the ball 32 and the ball cage 34 and/or the seal seat 23 are, for example, metals such as brass and copper and their alloys, in particular bronze. Likewise suitable are thermoplastic, thermosetting and elastomeric plastics, for example silicones, PTFE, PE, PA, PP and POM, or materials obtained from renewable raw materials, such as rubber or cellulose.

[0045] It will be appreciated that a sealing mechanism 18 according to the present invention is not limited to the embodiment shown. For example, in further exemplary embodiments the first compressed-air passage 14 and/or the sealing mechanism 18, other than shown in FIGS. 1 and 2, is not arranged solely vertically. In order for the sealing member 20 to be pressed against the seal seat 23 by the sealing member 20 floating on the fluid F, it is sufficient if the seal seat 23 is oriented so that it points vertically downwards at least in part, that is to say that a normal to a surface of the seal seat 23 has at least one component that is oriented vertically downwards. It is further possible that the sealing mechanism 18, instead of being arranged wholly in the first compressed-air passage 14, is arranged only partially in the first compressed-air passage 14 and/or is arranged at, beneath, or next to the first compressed-air passage 14.

[0046] It will further be appreciated that the form of the sealing member 20 is not limited to the ball 32 shown. Thus, further embodiments of the sealing member 20 can have different forms, for example the form of a cylinder, a disk, a cone, a truncated cone, or an ellipsoid. Likewise, the form of the guide 24 is not limited to a linear guide which encloses the sealing member 20, as is shown by the ball cage 34. For example, the guide 24 in further embodiments is of helical form and/or is designed so that the sealing member 20 is guided on or next to the guide 24. It is further conceivable that the guide 24 is not form-fitting, as in the case of the ball cage 34, but is effected by way of a force, for example by magnetic attraction, which biases the sealing member 20 in the direction towards the seal seat 23. It is likewise preferred to combine biasing with a form-fitting guide 24. In particular, it is preferred to bias the ball 32 shown towards the seal seat 23 by way of a biasing element, for example a spring.

[0047] Likewise, the sealing member 20 is not limited to having a closed cavity 33 therein in order to be capable of floating on the fluid F. Thus, the sealing member 20 can be made wholly or partially of a material which has a lower density than the fluid F. For example, such a material can be foam, in particular closed-cell foam. It is likewise possible that a closed cavity 33 of a sealing member 20 is filled with a material which has a lower density than the material of the shell 35 of the sealing member 20. It is suitable in particular to fill the cavity 33 with foam or with gas.

[0048] In FIG. 2, the fluid level H2 of the fluid F is below the threshold value S. The sealing mechanism 18 is in the normal state Z1, in which the ball 32 is arranged not in the second position P2 but, for example as shown, in the first position P1. This first position P1 of the ball 32 is identified in FIG. 2 by a broken line and is arranged at the end 28 of the guide 24 that is situated downstream in the outflow direction R1. In the normal state Z1, the ball 32 does not abut the seal seat 23; the ball 32 and the seal seat 23 are spaced apart from one another. In this normal state Z1, a flow can pass through the first compressed-air passage 14 both in the outflow direction R1 and in the inflow direction R2.

[0049] Because the ball 32 is linearly movable along the guide 24 along the degree of freedom M and is capable of floating on the fluid F, the ball 32 can occupy any intermediate position between the first position P1 and the second position P2 according to a fluid level of the fluid F which is between the second fluid level H2 and the threshold value S.

[0050] At the end 28 of the guide 24 that is situated downstream there is preferably provided a stop 30 which prevents the ball 32 from coming out of the guide 24 when the fluid level of the fluid F falls below the depicted fluid level H2. For example, the stop 30, as shown in FIGS. 1 and 2, can be a cup-shaped screen which is designed to prevent particles in the fluid F from entering the first compressed-air passage 14. If such particles reach the region of the seal seat 23, they can impair the proper sealing action of the sealing mechanism 18.

[0051] The exemplary embodiment shown is particularly preferred because the sealing mechanism 18, as a result of the ball 32 floating on the fluid F, can be brought into the second position P2, and thus from the normal state Z1 into the sealing state Z2, by the fluid F itself when the fluid level of the fluid F rises above the threshold value S. The exemplary embodiment shown is further particularly preferred because the threshold value S is defined by the combination of the arrangement of the seal seat 23 with the properties of the ball 32, in particular the mean density and the diameter D.sub.a thereof. The threshold value S corresponds to the fluid level of the fluid F in the first volume 12 and/or in the first compressed-air passage 14 at which the ball 32, by floating on the fluid F, comes into contact with the seal seat 23.

[0052] In other preferred embodiments, the sealing mechanism 18 is designed to detect by suitable devices, for example sensors, that the fluid F has exceeded the threshold value S and to establish the sealing state Z2 by a suitable mechanism, for example by actuators. In such embodiments, the threshold value S is defined by the position of a sensor and/or of the measuring point of the sensor. In particular, it will be appreciated that the sealing mechanism 18 is not limited to the combination shown of the guide 24, the seal seat 23, and the sealing member 20. Any sealing mechanism which can change between the normal state Z1 and the sealing state Z2 can replace the sealing mechanism 18 shown. Thus, it is possible to use as the sealing mechanism 18 a check valve which can be held in the open position by suitable mechanisms, for example by way of electronic actuators.

[0053] The exemplary embodiment shown is also particularly preferred because the elements of the sealing mechanism 18, in particular the ball 32 and the ball cage 34, can be present separately from the pneumatic device 1, wherein it can be possible to retrofit an existing pneumatic device 1 with a sealing mechanism 18 according to the present invention.

[0054] In the exemplary embodiment of FIGS. 1 and 2, the pneumatic device 1 is a pneumatic brake system B with a relay valve R, wherein the brake system B is shown in its installation situation in a commercial vehicle. For a more detailed explanation of the features of the brake system B, in particular of the relay valve R, reference may be made to the relevant prior art. It will be appreciated, however, that a pneumatic device according to the present disclosure can be any pneumatic device that has a first compressed-air passage between a first volume and a pressurized part, in particular a pressure-generating system, for example a compressor.

[0055] FIGS. 3 and 4 show a ball cage 34 which is used as the guide 24 in the pneumatic device 1 of FIGS. 1 and 2 and which can also be used in further embodiments (not shown) of the pneumatic device 1. FIG. 4 is a sectional view through the ball cage 34, which is shown from outside in FIG. 3. Features which are already shown in FIGS. 1 and 2 have the same reference signs in FIGS. 3 and 4.

[0056] The ball cage 34 has a plurality of guide bars 38 extending from the end 26 that is situated upstream in the outflow direction R1. At the end 26 of the ball cage 34 that is situated upstream in the outflow direction R1, the ball cage 34 has a portion 43 which is continuous in the circumferential direction, in which the seal seat 23 with the circumferential surface 22 and the edge 21 is also arranged. The guide bars 38 are arranged on the circumference of the ball cage 34 and are spaced apart from one another in the circumferential direction, so that a largely cylindrical cavity 44 of diameter D.sub.i is arranged in the interior of the ball cage 34. In the cavity 44, the ball 34 is guided in its movement between the first position P1 and the second position P2 by the guide bars 38.

[0057] In the circumferential direction, a flow channel 41 is arranged between two mutually spaced apart guide bars 38. The embodiment shown is particularly preferred because it allows an outside diameter D.sub.a of the ball 32 (see FIG. 2) and the diameter D.sub.i of the cavity 44 to be so configured that the ball 32 is guided in the cage 34 both with no or only a small amount of play and with only low friction. At the same time, the flow channels 41 in the ball cage 34 allow the pneumatic device 1 to be vented, wherein the outflowing compressed air flows around the ball 32 by way of the flow channels 41.

[0058] In the exemplary embodiment shown (FIGS. 1 to 4), the ball cage 24 is of monolithic form, that is to say the guide bars 38, the continuous portion 43, and the seal seat 23 consist of a cohesive piece. In particular, the monolithic ball cage 24 is made of a single material.

[0059] In alternative embodiments, individual portions of the ball cage 24 are manufactured separately and joined together to form the ball cage 24. In particular, it is thus possible to produce the guide bars 38 from a first material which facilitates sliding or rolling of the ball 32 along the guide bars 38, for example PTFE or bronze. At the same time or alternatively, the seal seat 23 consists of a second material which contributes to the sealing action between the seal seat 23 and the ball 32.

[0060] It is further possible to coat at least the inwardly facing faces 45 of the guide bars 38 with a material which facilitates sliding or rolling of the ball 32. Likewise, the seal seat 23 can be coated with a material which improves the sealing action.

[0061] The outside diameter D.sub.A of the ball cage 34 is adapted to the cross-sectional diameter D of the first compressed-air passage 14 (see FIG. 1), so that the ball cage 34 can preferably be installed in the first compressed-air passage 14 by way of a press-fit.

[0062] In the exemplary embodiment shown, the ball cage 34 has elongated guide bars 39 which extend further in the outflow direction R1 than the other, shorter guide bars 47. As is shown in FIG. 1, the inside diameter Ds of the stop 30 is larger than the inside diameter D.sub.i of the ball cage 34, and is arranged non-coaxially with the first compressed-air passage 14, that is to say eccentrically thereto. The ends of the shorter guide bars 47 that are situated downstream in the outflow direction R1 are flush with a side wall 48 of the cup-shaped stop 30. The elongated guide bars 39 extend into an inner region of the cup-shaped stop 30 and are so oriented that they separate off a region 50 of the stop 30 that is not in direct alignment with the inner cavity 44 of the ball cage 34. The ball cage 34 is thus so configured that it prevents the ball 32 from moving to the side into the region 50 of the stop 30. The ball 32 can thus be prevented from canting between the stop 30 and the cage 34 as the fluid level rises and thus possibly being impeded from moving from the first position P1 into the second position P2.

[0063] In the exemplary embodiment of the pneumatic device 1, the fluid F against which the pressurized part 16 is to be directed is water W. The mean density of the sealing member 20 is preferably 1000 kg/m.sup.3 or less, 900 kg/m.sup.3 or less, 800 kg/m.sup.3 or less, 700 kg/m.sup.3 or less or 600 kg/m.sup.3 or less. Preferably, the sealing member 20 has a density which is selected from a range which is defined by a maximum value down to 0 kg/m.sup.3, wherein the maximum value is included in the range. The maximum value is particularly preferably any desired value from 1000 kg/m.sup.3 to 0.01 kg/m.sup.3.

TABLE-US-00001 List of reference signs (part of the description) 1 pneumatic device 10 venting path 12 first volume, through which a flow can pass 14 first compressed-air passage 16 pressurized part 18 sealing mechanism 20 sealing member 21 edge 22 circumferential surface 23 seal seat 24 guide 26 end situated upstream in the outflow direction R1 28 end situated downstream in the outflow direction R1 30 cup-shaped screen, stop 32 ball 34 ball cage 35 (ball) shell 38 guide bar 39 elongated guide bar 40 second compressed-air passage 41 flow channel 43 continuous portion 44 inner cavity 45 inwardly facing face 47 shorter guide bar 48 side wall 50 region not in direct alignment with the inner cavity 44 52 valve plate 54 control piston B pneumatic brake system D cross-sectional diameter of the first compressed-air passage 14 D.sub.A outside diameter of the ball cage 34 Da outside diameter of the ball 32 D.sub.i inside diameter of the cavity 44 Ds inside diameter of the cup-shaped stop 30 F fluid F.sub.A buoyant force F.sub.P pushing force H1 first fluid level H2 second fluid level L length of the first compressed-air passage 14 N normal vector Nv vertical component of the normal vector N P.sub.Ü excess pressure P1 first position P2 second position R relay valve R1 outflow direction R2 inflow direction S threshold value U environment W water Z1 normal state Z2 sealing state