Pressure compensation device and use thereof

Abstract

The invention relates to a pressure compensation device, comprising a grid-shaped housing (1) with a gas passage opening (2) that connects an inner side (3) and an outer side (4) of the pressure compensation device in a flow-conducting manner depending on differential pressure in a flow direction (5), wherein the gas passage opening (2) is covered by an inner membrane (6) arranged towards the inner side and an outer membrane (7) arranged towards the outer side (4), wherein the inner membrane (6) and the outer membrane (7) are in each case gas-permeable and are arranged in a functional series circuit with respect to one another, and wherein the inner membrane (6) and the outer membrane (7) are arranged adjacent to one another at a spacing (8) as viewed in the flow direction (5) between the inner side (3) and the outer side (4). A gas-permeable first protective structure (14) is functionally connected upstream of the inner membrane (6) on the side facing the inner side (3) and / or a gas-permeable second protective structure (9) is arranged in the spacing (8).

Description

[0001] Pressure equalization device and its use

[0002] Description

[0003] Technical area

[0004] The invention relates to a pressure compensation device comprising a grid-shaped housing with a gas passage opening which connects an inner side and an outer side of the pressure compensation device in a flow-conducting manner in the flow direction depending on the differential pressure, wherein the gas passage opening is covered by an inner membrane arranged towards the inner side and an outer membrane arranged towards the outer side, and wherein the inner and outer membranes are each gas-permeable and arranged in a functional series connection to one another.

[0005] Furthermore, the invention relates to a use of the pressure compensation device.

[0006] State of the art

[0007] DE 10 2021 102 444 A1 discloses such a pressure compensation device, comprising an inner side and an outer side connected by a gas passage opening in a pressure-dependent and flow-conducting manner. The gas passage opening is covered by two gas-permeable membranes arranged on the side of the gas passage opening facing the outer side and each comprising at least one nonwoven fabric layer. The membrane facing the inner side comprises a nonwoven fabric layer comprising fibers substantially completely encased by an elastomer sheath. This membrane thus exhibits oil-repellent properties.

[0008] The inner membrane covers the gas passage opening on the side of the gas passage opening facing the outer membrane. The inner side of the inner membrane faces the inside of the pressure compensation device and thus the interior of a machine housing, and can therefore be directly exposed to medium from the machine housing.

[0009] If there are liquid media, such as oil, on the inside of the pressure compensation device, i.e. inside a machine housing that is equipped with the pressure compensation device, it must be prevented that the liquid medium passes from the inside through the pressure compensation device to the outside and thus into the environment.

[0010] In pressure equalization devices with only a single membrane between the inside and outside made of a conventional, porous PTFE material, the pressure equalization device would function well when new. The membrane acts like a filter. As the service life of such a PTFE membrane increases, its pores become clogged by the medium, especially oil. Consequently, the gas permeability of the PTFE membrane deteriorates, and the differential pressure between the inside and outside increases to an undesirable degree. A loss of watertightness is also possible.

[0011] In order to ensure a permanently good pressure equalization, the fibers of the membrane facing the inside of the known pressure equalization device are essentially completely covered by a sheath made of an elastomer.

[0012] Description of the invention

[0013] The invention is based on the object of further developing a pressure compensation device of the type mentioned above in such a way that the membranes in the pressure compensation device exhibit consistently good performance characteristics over a long service life, in particular that the membranes are well protected from exposure to medium from a machine housing to which the pressure compensation device is assigned. This protection of the membranes should also ensure that the pressure compensation device exhibits consistently good performance characteristics over a long service life, since the gas permeability of the membranes does not deteriorate significantly with increasing service life of the pressure compensation device.

[0014] In addition, one use of the pressure equalization device should be mentioned.

[0015] This object is achieved according to the invention by a pressure compensation device and a use having the features of claim 1 and claim 16.

[0016] The subclaims refer to advantageous embodiments.

[0017] To achieve the object, a pressure compensation device is provided, comprising a grid-shaped housing with a gas passage opening which connects an inner side and an outer side of the pressure compensation device in a flow-conducting manner in the flow direction as a function of the differential pressure, wherein the gas passage opening is covered by an inner membrane arranged towards the inner side and an outer membrane arranged towards the outer side, wherein the inner and outer membranes are each gas-permeable and arranged in a functional series connection with one another, and wherein the inner and outer membranes, viewed in the flow direction between the inner and the outer side, are arranged adjacent to one another at a distance, and wherein a gas-permeable first protective structure is functionally arranged upstream of the inner membrane on the side facing the inner side and / or wherein a gas-permeable second protective structure is arranged at the distance.

[0018] The first protective structure ensures that the medium from the inside of the machine housing first impacts the protective structures before flowing outward. This prevents the inner membrane from being directly and immediately exposed to the medium. The risk of the medium penetrating the inner membrane is minimized by the first protective structure.

[0019] As a result, the outer membrane, which is more sensitive than the inner one, is doubly protected, namely by the first protective structure and the inner membrane, and is therefore well protected against exposure to the medium.

[0020] Furthermore, the protection of the outer membrane is improved when the second protective structure is used in addition to the first protective structure. Any medium that penetrates the inner membrane to the outside despite the first protective structure is prevented from penetrating the outer membrane by the second protective structure.

[0021] The two diaphragms are each functionally individualized, with the inner diaphragm designed to protect the outer diaphragm. The inner diaphragm, together with the first protective structure, protects the outer diaphragm from direct exposure to a medium contained within a machine housing, such as oil.

[0022] This allows the outer membrane to have a simple structure. It can, for example, contain PTFE or ePTFE, materials that, without the protection of at least one of the protective structures and the inner membrane, would react to oil exposure by deteriorating their performance properties, particularly by deteriorating their air permeability.

[0023] This deterioration of the performance characteristics is prevented by the inner membrane and the first protective structure functionally arranged upstream of the inner membrane and / or by the second protective structure arranged at a distance.

[0024] This particularly effective protection of the outer membrane ensures that it retains its good gas permeability even during a long service life of the pressure equalization device.

[0025] The inner and outer membranes are arranged adjacent to each other at a distance from each other, viewed in the direction of flow between the inside and outside. This reduces the risk of the outer membrane being exposed to media that would impair its performance characteristics. This distance is advantageous because the inner membrane is also gas-permeable and therefore breathes depending on the differential pressure, even when exposed to oil. This allows oil to reach the upper side of the inner membrane, which faces the outer membrane.

[0026] Even then, the risk of the outer membrane being exposed to pressure on the side facing the inner membrane is minimized by the distance between the membranes and also by the second protective structure arranged at a distance. Further improved protection of the outer membrane against exposure to medium from the interior of a machine housing is thus achieved by arranging the second protective structure at this distance.

[0027] The second protective structure can be formed by an annular collar which delimits the gas passage opening on the outer circumference.

[0028] The collar can be funnel-shaped.

[0029] The advantage here is that it provides a large opening for breathing. The collar can be made in one piece, for example, by injection molding. When mounted horizontally, any oil that may be present will collect at the lowest point and drip back.

[0030] According to another embodiment, it can be provided that the second protective structure is designed in a labyrinth-like manner.

[0031] The advantage here is that there is also a large opening for breathing and that oil droplets first hit the protective structure before reaching the outer membrane.

[0032] Another advantage is that a labyrinth-like protective structure is a separate component, thus allowing for a high degree of design flexibility for the protective structure.

[0033] The first and / or second protective structure can have perforations. It is advantageous that the protective structures have good gas permeability. The number and shape of the perforations allow the breathability to be adapted to the specific conditions of the application. A small opening cross-section of the perforations ensures that the risk of larger oil droplets penetrating is minimized.

[0034] The second protective structure can be made of the same material and formed integrally with the housing. The gas permeability of both membranes is not impaired by the previously described configurations, but the outer membrane is effectively protected from exposure to medium located on the surface of the inner membrane, which is arranged toward the outer membrane.

[0035] The second protective structure can be configured with an inner and an outer mounting projection for securing the inner and outer membranes, wherein the mounting projections extend opposite each other in the flow direction. The mounting projections reliably keep the membranes spaced apart during the intended use of the pressure compensation device, particularly when a differential pressure exists between the inside and outside and the pressure compensation device is in operation.

[0036] This is also helped if the membranes are arranged on opposite sides of the second protective structure.

[0037] The second protective structure and the fastening projections are preferably formed integrally with one another and are made of the same material. Further preferably, the second protective structure, the fastening projections, and the housing are formed integrally with one another and are made of the same material. Such a design allows for simple and cost-effective manufacture of the pressure compensation device, as well as its assembly. The pressure compensation device has a simple design with few parts.

[0038] The housing is preferably made of a tough, polymeric material.

[0039] Such housings are easy and inexpensive to manufacture and are lightweight. The housing can have an inner surface facing the membranes and coated with an oleophobic coating. This has the advantage of reducing the potential adhesion and creep of fluid from the machine housing, such as oil, along the housing of the pressure compensation device. Such an oleophobic coating can be applied, for example, through plasma treatment or by fluorination of the surface, by applying a fluorinated oil or varnish.

[0040] Further preferably, the parts formed integrally with the housing and made of the same material can also be coated with oleophobic coating, i.e. the second protective structure and the fastening projections.

[0041] The protective structures can also be coated with oleophobic coating and then also have the advantages described above.

[0042] The housing and outer membrane can be covered by a cover on the outside. This has the advantage of preventing the interior of the pressure compensation device from being directly exposed to liquid media and / or dust from the environment. The cover protects the outer membrane from environmental influences and mechanical stress, thus maintaining its excellent performance characteristics over a long service life.

[0043] The outer membrane can be designed to be water-repellent, at least on the side facing the outside, such that the pressure compensation device preferably has an IPX 6K, IPX 7, or IPX 9K standard according to ISO 20653. Further preferably, the outer membrane is designed to be not only water-repellent, but also dust-repellent, at least on the side facing the outside, so that the pressure compensation device preferably achieves an IP6X standard according to the aforementioned standard.

[0044] The inner membrane can be designed to be oil-repellent on the inner side to protect the outer membrane as effectively as possible from exposure to media that are detrimental to the performance characteristics of the outer membrane. For this purpose, the inner membrane can be made of an open-pore structure made of woven fabric or nonwoven fabric, for example, a nonwoven fabric comprising fibers that are essentially completely coated with an elastomer, as described above with regard to the prior art.

[0045] Furthermore, the invention relates to the use of a pressure compensation device, as described above, for a machine housing in which an oil-containing medium is accommodated. The machine housing can be, for example, a transmission housing, an axle housing, or a housing for electric motors, whereby the aforementioned machine housings can be used in motor vehicles, trucks, agricultural machinery, or ships.

[0046] Short description of the drawing

[0047] Three embodiments of a pressure compensation device according to the invention are explained in more detail below with reference to the schematically illustrated Figures 1 to 3.

[0048] Figure 1 shows a first embodiment. Figures 2 and 3 show two further embodiments, which differ from the embodiment of Figure 1 in the second protective structure.

[0049] In Figure 3, the first protective structure is also different.

[0050] Implementation of the invention

[0051] The pressure compensation devices from Figures 1 to 3 each comprise the grid-shaped housing 1, which consists of a tough, polymeric material.

[0052] In the illustrated embodiments, the housing 1 of the pressure compensation device is mounted in a recess 16 of the machine housing 15. In these embodiments, the mounting is achieved by a screw connection using a thread 17, with the recess 16 being sealed to the outside 4 by a seal 18 made of a rubber-elastic material. The seal 18 is arranged sealingly between the housing 1 and the machine housing 15 under elastic prestress.

[0053] The gas passage opening 2 is arranged in the housing 1, through which the inside 3 and the outside 4 of the pressure compensation device are connected in a flow-conducting manner in the flow direction 5, depending on the differential pressure.

[0054] The gas passage opening 2 is covered by an inner membrane 6 on the side facing the inner side 3 and by an outer membrane 7 on the side facing the outer side 4. The membranes 6, 7 are each made of a gas-permeable material and are arranged in a functional series circuit. The outer membrane 7 is designed to be water- and dust-repellent to prevent moisture and contaminants from penetrating the interior of the pressure compensation device. To protect the outer membrane 7 from mechanical stress and for further improved protection against the ingress of moisture and contaminants, the housing 1 is provided with a cover 13 that covers the outer membrane 7 on the outside.

[0055] The pressure equalization is not impaired by the cover 13 because the cover 13 allows air circulation due to its design, in particular its openings.

[0056] The first protective structure 14, the inner membrane 6, and the second protective structure 9 have the task of protecting the outer membrane 7 as best as possible from exposure to media from the interior of the machine housing 15, in particular from exposure to oil-containing media, without the performance characteristics of the pressure compensation device being significantly impaired by this protection. For this purpose, the inner membrane 6 is designed to be oil-repellent and, in the exemplary embodiment shown, consists of an open-pore material. The open-pore material can be a fleece or a woven fabric. As described above, the inner membrane 6 is oil-repellent; however, oil can still penetrate the side of the inner membrane 6 facing the outer membrane 7 because the inner membrane 6, like the outer membrane 7, is gas-permeable.

[0057] In Figure 1, the second protective structure 9 is designed as a funnel-shaped collar 19.

[0058] In order to prevent the outer membrane 7 from being pressurized with medium from the machine housing and / or from the outside of the inner membrane 6 as reliably as possible during the intended use of the pressure compensation device, in particular when a differential pressure exists between the inner side 3 and the outer side 4, the first protective structure 14 is initially provided. Also arranged in the flow direction 5 within the distance 8 is the annular second protective structure 9 in the form of the collar 19, which in the illustrated embodiment has a central opening and which delimits the gas passage opening 2 on the outer circumference.

[0059] The inner membrane 6 is arranged on the side of the gas passage opening 2 facing the inner side 3, in this case the second protective structure 9, while the outer membrane 7 is arranged on the side facing the outer side 4.

[0060] This allows a large distance 8 to be provided between the membranes 6, 7, for particularly effective protection of the relatively more sensitive outer membrane 7.

[0061] The second protective structure 9 forms the inner 10 and outer mounting projections 11 for securing the inner 6 and outer membranes 7. The arrangement and shape of the mounting projections 10, 11 allow the distance 8 between the membranes 6, 7 to be adapted to the specific conditions of the application. The mounting projections 10, 11 extend opposite one another, viewed in the flow direction 5.

[0062] The pressure compensation device has a particularly simple design with few parts. The housing 1, the second protective structure 9, and the fastening projections 10, 11 are integrally formed and made of a single material, consisting of a tough, hard polymer material.

[0063] To minimize the adhesion of medium from the machine housing 15 inside the pressure compensation device, the inner surface 12 of the housing 1, the protective structures 9, 14, and the fastening projections 10, 11 are coated with an oleophobic coating. Medium that would adhere inside the housing 1 without an oleophobic coating is thus diverted toward the machine housing 15.

[0064] To minimize the exposure of the inner membrane 6 to medium from the machine housing 15, the gas-permeable first protective structure 14 is functionally arranged upstream of the inner membrane 6 on the side facing the inner side 3. This first protective structure 14 prevents the inner membrane 6 from being directly exposed to medium from the machine housing 15.

[0065] Because the inner membrane 6 is already protected by the first protective structure 14 from direct exposure to medium from the machine housing 15, the outer membrane 7 is also particularly well protected. This protection is particularly important if the material of the outer membrane 7 would react to exposure to medium from the interior of the machine housing 15 by deteriorating its performance properties, in particular by deteriorating its gas permeability.

[0066] In Figure 2, the second protective structure 9 is labyrinth-like, and in Figure 3, the first 14 and second protective structures 9 have openings. Otherwise, the embodiments according to Figures 2 and 3 do not differ in function from the embodiment in Figure 1.

Claims

Patent claims 1. Pressure compensation device, comprising a grid-shaped housing (1) with a gas passage opening (2) which connects an inner side (3) and an outer side (4) of the pressure compensation device in a flow-conducting manner in the flow direction (5) depending on the differential pressure, wherein the gas passage opening (2) is covered by an inner membrane (6) arranged towards the inner side (3) and an outer membrane (7) arranged towards the outer side (4), wherein the inner (6) and the outer membrane (7) are each gas-permeable and arranged in a functional series connection with one another, and wherein the inner (6) and the outer membrane (7), viewed in the flow direction (5) between the inner (3) and the outer side (4), are arranged adjacent to one another at a distance (8), characterized in thatthat a gas-permeable first protective structure (14) is functionally arranged upstream of the inner membrane (6) on the side facing the inner side (3) and / or that a gas-permeable second protective structure (9) is arranged in the distance (8).

2. Pressure compensation device according to claim 1, characterized in that the second protective structure (9) is formed by an annular collar (19) which delimits the gas passage opening (2) on the outer circumference.

3. Pressure compensation device according to claim 2, characterized in that the collar (19) is funnel-shaped.

4. Pressure compensation device according to claim 1, characterized in that the second protective structure (9) is labyrinth-like.

5. Pressure compensation device according to claim 1, characterized in that the first (14) and / or the second protective structure (9) has openings.

6. Pressure compensation device according to one of claims 1 to 5, characterized in that the second protective structure (9) is designed with an inner (10) and an outer fastening projection (11) for fastening the inner (6) and the outer membrane (7) and that the fastening projections (10, 11) extend opposite to one another in the flow direction (5).

7. Pressure compensation device according to claim 6, characterized in that the second protective structure (9) and the fastening projections (10, 11) are formed integrally into one another and are made of the same material.

8. Pressure compensation device according to one of claims 6 or 7, characterized in that the second protective structure (9), the fastening projections (10, 11) and the housing (1) are formed integrally into one another and are made of the same material.

9. Pressure compensation device according to one of claims 1 to 8, characterized in that the housing (1) consists of a tough, polymeric material.

10. Pressure compensation device according to one of claims 1 to 9, characterized in that the housing (1) has on its side facing the membranes (6, 7) an inner side (12) which is coated oleophobically.

11. Pressure compensation device according to one of claims 1 to 10, characterized in that at least one of the two protective structures (14, 9) is coated oleophobically.

12. Pressure compensation device according to one of claims 1 to 11, characterized in that the housing (1) and the outer membrane (7) are covered on the outside by a cover (13).

13. Pressure compensation device according to one of claims 1 to 12, characterized in that the outer membrane (7) is designed to be water-repellent at least on the side facing the outer side (4).

14. Pressure compensation device according to one of claims 1 to 13, characterized in that the outer membrane (7) is designed to be dust-repellent at least on the side facing the outer side (4).

15. Pressure compensation device according to one of claims 1 to 10, characterized in that the inner membrane (6) is designed to be oil-repellent at least on the side facing the inner side (3).

16. Use of a pressure compensation device according to one of claims 1 to 15 for a machine housing (15) in which an oil-containing medium is accommodated.

Images