Pressure equalization device

Abstract

Pressure equalization device comprising a cage (1) with a gas passage opening (2), wherein the gas passage opening (2) is enclosed by a valve seat (3) and a diaphragm (4) arranged in the cage (1), which is held on a retaining element (5) and is designed as a valve body (6), wherein the diaphragm (4) can be snapped, depending on the differential pressure, from a retaining position (7) in which it seals against the valve seat (3) to an opening position (8) in which it is lifted from the valve seat (3) and allows a direct passage through the gas passage opening (2), wherein the diaphragm (4) has a bistable instability (9) or an instability (9) with a metastable and a stable state.

Description

Technical area

[0001] The invention relates to a pressure compensation device. State of the art

[0002] A pressure compensation device for a housing is known from DE 10 2017 003 360 B3. The previously known pressure compensation device has an inner side, an outer side, and a cage with a gas passage opening. The gas passage opening connects the inner side and the outer side in a flow-conducting manner depending on the differential pressure. The gas passage opening is covered by a gas-permeable membrane, to which a pressure relief valve designed as a burst protection device is assigned in a functionally parallel circuit.

[0003] Another pressure equalization device is known from EP 2 545 882 A1. The pressure equalization device is provided for equalizing an internal pressure in a housing, wherein an electrochemical device is arranged within the housing. A gas-permeable membrane is deformable depending on changes in the internal pressure and is preferably made of a PTFE material. The membrane normally enables pressure equalization between the inside and the outside. In the event of an undesirably high internal pressure in the housing, the membrane is destroyed by a mandrel designed as an emergency degassing element. The destroyed membrane opens a gas passage opening for emergency degassing of the housing. This provides burst protection for the housing. Description of the invention

[0004] The invention is based on the object of further developing a pressure compensation device such that it has a simple and component-free design, is thus simple and cost-effective to manufacture in terms of both manufacturing technology and cost-effectiveness, and functions reliably over a long service life. Furthermore, the pressure compensation device should enable very rapid pressure equalization by allowing the highest possible flow rates to flow through it.

[0005] This object is achieved according to the invention by a pressure compensation device having the features of claim 1.

[0006] The claims directly or indirectly referring back to claim 1 refer to advantageous embodiments.

[0007] To achieve the object, a pressure compensation device for a housing is provided, comprising a cage with a gas passage opening, wherein the gas passage opening is enclosed by a valve seat and a membrane arranged in the cage, which membrane is held on a holding element and is designed as a valve body, wherein the membrane can be snapped, depending on the differential pressure, from a holding position in which it contacts the valve seat in a sealing manner, into an opening position in which it is lifted off the valve seat and releases a direct passage through the gas passage opening, wherein the membrane has a bistable instability or an instability with a metastable and a stable state.

[0008] Such instability is comparable to an instability similar to that of a cracking frog.

[0009] The pressure compensation device can be provided for a housing and mounted in a housing wall of the housing and / or integrated in a cover for the housing.

[0010] The pressure compensation device has the advantage that pressure equalization occurs very quickly due to high volume flows, exclusively through the instability-provided diaphragm. This allows the pressure compensation device to have a particularly simple design with few parts, making it easy and cost-effective to manufacture.

[0011] In particular, the pressure compensation device guarantees only minimal fluctuations in the trigger pressure. Pressure compensation is non-destructive, allowing the pressure compensation device to be 100% tested, as will be explained later.

[0012] The function of the pressure compensation device is as follows: The membrane encompasses a bistable instability, or an instability with a metastable and a stable state. Metastability is a weak form of stability. The metastable state is stable against small external changes, such as pressure, but unstable against larger external changes.

[0013] Bistable instability, or instability with a metastable and a stable state, also occurs with a so-called twist-off screw cap. Due to the negative pressure in the container sealed by the twist-off screw cap, the central part of the twist-off screw cap, shaped like a snapping frog, is kept in a metastable state. If air flows into the previously sealed container when the twist-off screw cap is opened, the central part of the cap snaps back into the stable state. Based on the membrane in the inventive

[0014] Pressure compensation device means that the diaphragm is held in its holding position and sealingly contacts the valve seat during a pressure increase inside a housing that is within a non-critical range.

[0015] As the pressure inside the housing continues to rise, a critical threshold is reached at which the diaphragm, due to instability, suddenly snaps into the open position, thereby exposing the gas passage opening almost instantaneously, with a large or even full opening cross-section. Because a large volume flow can pass through the gas passage opening, pressure equalization within the housing occurs very quickly, protecting the housing from damage or destruction.

[0016] Due to the instability described above, the pressure compensation device can have larger manufacturing tolerances and still performs its function consistently well even over a long period of use.

[0017] The snap action of the membrane is designed for a specific trigger pressure by its material and geometry. Manufacturing tolerances of the membrane, such as the tolerance of the material thickness and the general fluctuation of the material properties, have only a negligible impact on the membrane's performance characteristics.

[0018] The snap-in diaphragm eliminates any further tolerance chaining that would affect other components of the pressure compensation device, such as the cage. This is because the diaphragm experiences a significant displacement when snapping from the metastable to the stable state, compared to the diaphragm's manufacturing tolerances. This displacement is often five to ten times the manufacturing tolerances. This ensures good functional reliability of the pressure compensation device, especially of the diaphragm during snap-in.

[0019] Another advantage is that 100% quality control is possible, since no material is destroyed in the pressure equalization device during its intended use. In particular, no bursting foils, which are often subject to significant aging effects, are used.

[0020] During production, the pressure compensation device can be subjected to a functional test / overpressure test, in which the diaphragm is loaded until it snaps. The differential pressure during the diaphragm's transition from the metastable to the stable state can be measured. If this differential pressure is within the specified tolerance range, the diaphragm can then be reinstalled in the pressure compensation device and returned to the metastable state before the component is packaged and shipped.

[0021] The instability then becomes metastable when the diaphragm makes sealing contact with the valve seat. The interior and exterior of the housing are then sealed off from each other by the diaphragm.

[0022] If the pressure inside the housing increases, the diaphragm deforms depending on the differential pressure until the internal pressure in the housing reaches a critical threshold and the diaphragm snaps into its opening position due to the instability.

[0023] Depending on the design of the retaining element, there is a possibility that the membrane could be completely separated from the retaining element when snapping into its open position, for example, by flying off. In such a case, the entire opening cross-section of the gas passage opening is opened almost instantly, allowing for the greatest possible volume flow and the fastest possible pressure equalization.

[0024] The membrane can preferably be made of an elastic material with small strain ranges, for example, a tough, hard polymer material. Such a material is particularly well-suited for instability because it is easy to generate such instabilities and design them in such a way that the material limits are not exceeded, thus enabling a non-destructive, 100 percent test, as described above.

[0025] Depending on the specific circumstances of the application, the membrane can be composed of a combination of a gas-tight material and a breathable membrane component. A polymer material, as described above, and a membrane component made of PTFE and / or nonwoven fabric are preferred. The membrane component can cover and close an opening in the membrane. In such a case, the pressure compensation device would also have a venting and de-aeration function during normal operation, similar to the function of the pressure compensation device described above.

[0026] The membrane is preferably disc-shaped and is attached to the valve seat on the outer circumference in a manner that allows it to be lifted off.

[0027] The valve seat can be formed, for example, by a sealing ring, preferably an O-ring, which is arranged in a corresponding groove of the holding element.

[0028] Alternatively, the sealing ring can also be part of the membrane and enclose it on the outer circumference.

[0029] During normal operation, the diaphragm bulges toward the interior of the housing. The outer periphery of the diaphragm then forms a seal against the valve seat surrounding the outer periphery of the diaphragm. If the pressure inside the housing exceeds a predetermined threshold, the diaphragm, which initially bulges inward, is moved from its holding position to the opening position. Due to its instability, the diaphragm suddenly snaps from the holding position into the opening position. In the simplest case, the diaphragm flies out of the retaining element.

[0030] The membrane, with its instability, can be reused several times.

[0031] The retaining element and the cage can be formed as a single piece and made of the same material. This results in a simple, component-free pressure compensation device.

[0032] The cage can be connected to the housing in a suitable manner. For example, the cage and housing can be connected using a screw or bayonet connection. This type of connection can be implemented particularly quickly and easily. Short description of the drawing

[0033] An embodiment of the pressure compensation device according to the invention is described in more detail below with reference to the figure. Implementation of the invention

[0034] The figure shows an embodiment of a pressure compensation device according to the invention in a schematic representation.

[0035] The pressure compensation device is mounted on a housing 10, which in the embodiment shown is formed by a battery housing.

[0036] The pressure compensation device comprises the cage 1, which in the illustrated embodiment is formed integrally with the retaining element 5 and made of the same material, and is connected to the housing 10 via a thread. Alternative fastening options, for example, using a bayonet connection, are also possible.

[0037] The retaining element 5 defines the outer circumference of the gas passage opening 2, wherein the gas passage opening 2 is enclosed by the valve seat 3. In this exemplary embodiment, the valve seat 3 is formed by a radially inwardly open groove in the retaining element 5, in which an O-ring made of a rubber-elastic material is arranged.

[0038] The membrane 4 is disc-shaped and made of a polymeric material. Other materials, which also allow for the provision of an instability 9 as claimed, are also possible.

[0039] The membrane 4 simultaneously forms the valve body 6, which is held sealingly on the valve seat 3 in the holding position 7.

[0040] The diaphragm 4 can be moved from the holding position 7, shown here in solid lines, to the opening position 8, shown here in dashed lines, depending on the differential pressure. The movement from the holding position 7 to the opening position 8 occurs when the diaphragm 4 suddenly snaps from the holding position 7 to the opening position 8. This snapping movement is achieved by the instability 9.

[0041] The instability 9 has a metastable state in the holding position 7, but a stable state in the opening position 8.

[0042] During assembly of the pressure compensation device, the diaphragm 4 is pressed into its lower position, the metastable holding position 7. The holding position 7 is maintained by the sealing support of the diaphragm 4 against the cage 1 and the valve seat 3, here in the form of an O-ring.

[0043] When a predetermined limit pressure / a predetermined differential pressure is reached, the membrane 4 snaps back from its metastable to the stable state and is thereby pushed out of the holding element 5, whereby pressure equalization occurs.

[0044] In the example shown, the internal pressure p i inside and the outside pressure p a outside of the membrane 4.

[0045] In the holding position 7, the membrane 4 seals the outer circumference of the valve seat 3.

[0046] If the internal pressure p i , the membrane 4 initially remains sealed until a critical threshold value of the internal pressure pi in the housing 10 is exceeded. Then the diaphragm 4 snaps from the holding position 7 into the opening position 8 and the diaphragm 4 lifts off the valve seat 3. The diaphragm 4 flies off the holding element 5 and, almost instantly, releases the entire opening cross-section of the gas passage opening 2. This allows even high volume flows to quickly escape from the interior of the housing 10 into the environment, and the housing 10 is protected from damage / destruction.

[0047] If, during the intended use of the pressure compensation device, an excess pressure were to be applied to the membrane 4 from the outside, the membrane 4 would strike the holding element 5 at its outer lower edge in such a way that the sealing effect is still ensured by the compression of the O-ring.

[0048] To mount the membrane 4 in the holding element 5, the membrane 4 in this embodiment is pressed into the holding position 7 by elastic deformation and is thereby sealingly connected to the valve seat 3 under elastic prestress.

[0049] The membrane 4, which is made of a plastic, is subject to practically no wear during the intended use of the pressure compensation device and can therefore be reused even after pressure equalization. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 003 360 B3

[0002] EP 2 545 882 A1

[0003]

Claims

[1] Pressure compensation device, comprising a cage (1) with a gas passage opening (2), wherein the gas passage opening (2) is enclosed by a valve seat (3) and a membrane (4) arranged in the cage (1), which membrane is held on a holding element (5) and is designed as a valve body (6), wherein the membrane (4) can be snapped, depending on the differential pressure, from a holding position (7), in which it contacts the valve seat (3) in a sealing manner, into an opening position (8), in which it is lifted off the valve seat (3) and allows a direct passage through the gas passage opening (2), wherein the membrane (4) has a bistable instability (9) or an instability (9) with a metastable and a stable state. [2] Pressure compensation device according to claim 1, characterized by that the instability (9) has a metastable state when the membrane (4) makes sealing contact with the valve seat (3). [3] Pressure compensation device according to one of claims 1 or 2, characterized by that the instability (9) has a stable state when the membrane (4) has snapped from the holding position (7) into the opening position (8) depending on the differential pressure. [4] Pressure compensation device according to one of claims 1 to 3, characterized by that the membrane (4) is completely separated from the holder element (5) in its opening position (8). [5] Pressure compensation device according to one of claims 1 to 4, characterized by that the membrane (4) consists of a tough, polymeric material. [6] Pressure compensation device according to one of claims 1 to 5, characterized by that the membrane (4) is disc-shaped and is attached to the valve seat (3) on the outer circumference in a manner that can be lifted off. [7] Pressure compensation device according to one of claims 1 to 6, characterized bythat the holding element (5) and the cage (1) are formed integrally into one another and are made of the same material.

Images