Self-locking membrane system

Abstract

Membrane system with a membrane (1) and connecting elements (2, 5, 8) for connecting the membrane to a membrane pump for pumping a fluid, the pump having a drive shaft designed for an oscillating translational movement perpendicular to the membrane plane during operation of the membrane pump and having an external thread at one end section for engaging with the membrane system by screwing, characterized in that the connecting elements comprise a threaded fitting (2), a pressure ring (5) and a pressure plate (8), wherein the threaded fitting (2) has a cylindrical section arranged coaxially to an axis perpendicular to the membrane plane, is fixedly or detachably connected to the membrane (1), has an external fitting thread (3) on the outside of the cylindrical surface of its section and an internal fitting thread (4) on the inside of the cylindrical surface of its section.preferably having a blind hole thread, wherein the pressure ring (5) has a cylindrical section which is arranged coaxially to the cylindrical section of the threaded fitting, and has on the inside of the cylindrical surface of its section an internal pressure ring thread (6) which is designed as a mating thread to the external thread (3) of the threaded fitting (2), wherein the pressure plate (8) has a cylindrical section which is arranged coaxially to the cylindrical section of the threaded fitting (2), has on the outside of the cylindrical surface of its section an external pressure plate thread (9) which is designed as a mating thread to the internal thread (4) of the threaded fitting (2), and has on the inside of the cylindrical surface of its section an internal pressure plate thread (10) which is designed for connection to the external thread on an end section of a drive shaft of a diaphragm pump,wherein the external thread (9) of the pressure plate (8) and the internal thread (4) of the threaded fitting (2) designed as a mating thread have a different thread pitch, a different thread rotation direction, or both a different thread pitch and a different thread rotation direction than the internal thread (6) of the pressure ring (5) and the external thread (3) of the threaded fitting (2) designed as a mating thread, and wherein the pressure plate (8) is connected to the pressure ring (5) via a connecting section (11) in a torque-resistant manner.

Description

SUBJECT OF THE INVENTION

[0001] The present invention relates to a membrane system comprising a membrane and connecting elements for connecting the membrane to a membrane pump for conveying a fluid, which has a drive axis designed for an oscillating translational movement perpendicular to the membrane plane during operation of the membrane pump and has an external thread at one end section for engagement with the membrane system by screwing.

[0002] The invention also includes a diaphragm pump for conveying a fluid, in particular a diaphragm metering pump, which has a diaphragm system of the type according to the invention and a drive shaft which is designed for an oscillating translational movement perpendicular to the diaphragm plane during operation of the diaphragm pump and has an external thread at one end section for engagement with the diaphragm system by screwing. BACKGROUND OF THE INVENTION

[0003] Diaphragm pumps for pumping fluids have a pumping chamber with at least one suction port through which the fluid to be pumped is sucked from a suction line into the pumping chamber, and at least one pressure port through which the fluid to be pumped is expelled through a pressure line. Valves are provided on the suction port and the pressure port which are opened and closed in opposite directions when fluid is sucked in and expelled, i.e. when fluid is sucked in the valve at the suction port is opened and the pressure port is closed so that fluid is not sucked back from the pressure line into the pumping chamber, and conversely when fluid is expelled the valve at the pressure port is opened and the suction port is closed so that fluid is not forced back into the suction line.

[0004] The delivery chamber is separated from the working chamber in a fluid-tight manner by a flexible diaphragm (delivery diaphragm). This diaphragm contains means for oscillating the diaphragm back and forth between a suction stroke position at the end of a suction stroke and a discharge stroke position at the end of a discharge stroke. During the suction stroke, the diaphragm is moved toward the working chamber, increasing the volume of the delivery chamber. This reduces the pressure in the delivery chamber and draws fluid in through the suction port. During the discharge stroke, the diaphragm is moved in the opposite direction, reducing the volume of the delivery chamber again, increasing the pressure in the delivery chamber and expelling fluid through the discharge port.

[0005] The diaphragm is generally circular disc-shaped and is firmly and fluid-tightly connected to the housing of the delivery chamber at its peripheral edge, for example by clamping or gripping between the housing parts of the delivery chamber and the working chamber. During oscillating back and forth, the diaphragm experiences the greatest deflection between the suction stroke position and the discharge stroke position due to its fixing at its peripheral edge in the middle. The back and forth movement of the diaphragm can be achieved in various ways, for example hydraulically through pressure changes in the working chamber or purely mechanically by means of a drive axis in the working chamber, which executes an oscillating translational movement perpendicular to the diaphragm plane and is connected essentially centrally to the circular disc-shaped diaphragm on the working chamber side.When reference is made here to a drive axis, this includes any means capable of performing an oscillating translational movement perpendicular to the plane of the membrane and transmitting it to the membrane in engagement with the membrane.

[0006] The drive shaft can be connected to the diaphragm in various ways, either detachably or permanently. However, a detachable connection between the drive shaft and the diaphragm is advantageous, allowing the diaphragm to be removed from the drive shaft and replaced in the event of a defect or wear. On the other hand, the connection between the drive shaft and the diaphragm must be sufficiently secure against accidental release during operation of the diaphragm pump, as this could result in failure or even destruction of the pump. Furthermore, the connection between the drive shaft and the diaphragm should have little or no play and ensure precise positioning and deflection of the diaphragm between the suction stroke and the discharge stroke positions.

[0007] A detachable screw connection between the drive shaft and the diaphragm has proven to be effective for this purpose. This is typically achieved by providing an external thread at one end of the drive shaft for screwing into a corresponding internal thread as a counter-thread on a connecting element attached to the diaphragm.

[0008] Since the diaphragm is subjected to oscillating back and forth during operation, it is made of one or more layers of a flexible material, usually a sufficiently flexible polymer material, although metallic diaphragms are also used in certain applications. Commonly used elastomer composite diaphragms typically consist of one or more interconnected layers of a thermoplastic polymer, such as ethylene propylene diene (monomer) rubber (EPDM), fluorocarbon rubber (FKM), or acrylonitrile butadiene rubber (AB or NBR), and regularly have a fabric embedded in the elastomer, for example, a polyamide fabric. On the pumping chamber side, elastomer composite diaphragms are often provided with an additional layer of polytetrafluoroethylene (PTFE; Teflon ®). For connection to the pump's drive shaft, a connecting element made of metal or a hard polymer, such as polyphenyl ether, with an internal thread that counteracts the external thread on the drive shaft, is bonded to the diaphragm material by bonding or during the vulcanization process of the elastomer. Such connections can be manufactured very stable and with sufficient durability for the service life of the elastomer composite diaphragm.

[0009] Due to mechanical stress, diaphragms have a limited service life, which varies depending on the material and structure of the diaphragms, the specific application, and the fluid being pumped. Furthermore, they are exposed to additional chemical attack when pumping and metering certain aggressive fluids, which can further shorten the service life of elastomer composite diaphragms, particularly due to degradation and / or embrittlement of the elastomer material itself and the bonds between different diaphragm layers. Therefore, in some applications, elastomer composite diaphragms in particular must be replaced after just a few months of operation, resulting in costs for the replacement diaphragms and downtime for diaphragm replacement.

[0010] Made entirely of polytetrafluoroethylene (PTFE; Teflon ®) (hereinafter referred to as PTFE membranes) have proven in many cases to be significantly more durable and long-lasting than conventional elastomer composite membranes, particularly when pumping and metering chemically aggressive fluids due to the chemical resistance of the PTFE material and because the membranes are made from solid PTFE material and not as a composite of individual membrane layers. The mechanical strength of PTFE membranes is just as good as that of many elastomer composite membranes. Depending on the intended application, diaphragm pumps are therefore either equipped with PTFE membranes during manufacture or delivery, or users are replacing used elastomer composite membranes with PTFE membranes in order to extend the replacement cycles.

[0011] It is therefore necessary, or at least advantageous, for diaphragm replacement and flexible use of the diaphragm pump if both elastomer composite diaphragms and PTFE diaphragms (i.e., diaphragms made of solid PTFE material) can be used equally in the same diaphragm pump. This requires that both diaphragm types be dimensioned to fit the spatial requirements of the diaphragm pump without resulting in technical disadvantages for one or the other diaphragm type. The means for connecting the diaphragm to the drive shaft for both diaphragm types must meet the spatial requirements, as well as the requirements for stability during operation and interchangeability when replacing the diaphragm.

[0012] However, these requirements for PTFE membranes come with the difficulty that connecting elements cannot be securely bonded to the PTFE material in the same way as with the elastomer materials commonly used for membranes, for example, by bonding or vulcanization. The PTFE material does not form a stable adhesive bond with metal or with hard polymers suitable for connecting elements.

[0013] A stable, particularly torque-resistant connection between the diaphragm and the connecting element for screwing it to the drive shaft is also important for diaphragm replacement, as the screw connection between the connecting element and the drive shaft is often very difficult to loosen after a certain period of operation, even with the application of relatively high torque. If the connection between the diaphragm and the connecting element is not sufficiently torque-stable, this can lead to the connecting element detaching from the diaphragm when unscrewing the diaphragm for the purpose of replacing the diaphragm and remaining attached to the drive shaft.

[0014] In a known PTFE diaphragm, the diaphragm is manufactured in one piece with a pin arranged centrally on the diaphragm and extending perpendicular to the diaphragm plane. The pin has a circular cross-section and an external thread (bolt thread) on its circumferential surface. A substantially cylindrical diaphragm pressure piece made of a hard polymer material, such as polyphenyl ether, is screwed onto the PTFE pin. For this purpose, the cylindrical diaphragm pressure piece has an internal thread extending from one end of the cylinder, which serves as a counter thread for screwing into the external thread of the pin. A further internal thread extending from the opposite end of the cylindrical diaphragm pressure piece is provided, which serves as a counter thread to the external thread on the drive shaft of a diaphragm pump and is intended to connect the diaphragm to the drive shaft.

[0015] A disadvantage of this design is that the cylindrical diaphragm pressure piece is relatively long, as it requires a thread on both ends, one to accommodate the external thread on the PTFE pin on the diaphragm and the other to accommodate the external thread on the drive shaft. This required installation depth perpendicular to the diaphragm plane limits the applicability of such PTFE diaphragms, for example, in diaphragm pumps with limited installation space. The manufacturability of PTFE diaphragms for replacement with existing elastomer composite diaphragms is also limited due to the required installation depth, as the connecting element in elastomer composite diaphragms can be considerably shorter because it only requires a thread on one side to connect to the external thread on the drive shaft and can be securely bonded directly to the diaphragm material on the opposite side.

[0016] A further disadvantage of this known PTFE diaphragm design is that, to ensure a torque-resistant connection of the diaphragm pressure piece to the PTFE journal, one or more metal bolts or cotter pins must be driven through one or more holes in the diaphragm pressure piece into the PTFE material of the journal. This is particularly important to ensure that the diaphragm does not detach from the diaphragm pressure piece when unscrewed for disassembly or replacement, but remains attached to the thread of the drive shaft. Inserting these bolts or cotter pins is very complex and therefore very costly during diaphragm manufacturing. OBJECT OF THE INVENTION

[0017] Based on the described prior art, it was therefore an object of the present invention to provide a membrane of the type mentioned at the outset, which overcomes the disadvantages of the prior art and ensures a secure and torque-resistant connection between the membrane and the connecting element to be screwed to a drive axle. DESCRIPTION OF THE INVENTION

[0018] According to the invention, this object is achieved by a membrane system with a membrane and connecting elements for connecting the membrane to a membrane pump for conveying a fluid, which has a drive axis which is designed for an oscillating translational movement perpendicular to the membrane plane during operation of the membrane pump and has an external thread at one end section for engagement with the membrane system by screwing, wherein the connecting elements comprise a threaded connector, a pressure ring and a pressure plate, where the threaded connector - has a cylindrical section arranged coaxially with an axis perpendicular to the plane of the membrane, - is firmly or detachably connected to the membrane, - has a male thread on the outside of the cylindrical section and - has an internal thread, preferably a blind hole thread, on the inside of the lateral surface of its cylindrical section, where the pressure ring - has a cylindrical portion arranged coaxially with the cylindrical portion of the threaded connector, and - has a pressure ring internal thread on the inside of the lateral surface of its cylindrical section, which is designed as a counter thread to the external thread of the threaded socket, where the printing plate - has a cylindrical section arranged coaxially with the cylindrical section of the threaded connector, - has on the outside of the lateral surface of its cylindrical section a pressure plate external thread, which is designed as a counter thread to the socket internal thread of the threaded socket, and - has on the inside of the lateral surface of its cylindrical section a pressure plate internal thread which is designed to be connected to the external thread on an end section of a drive shaft of a diaphragm pump, wherein the pressure plate external thread of the pressure plate and the socket internal thread of the threaded socket designed as a counter thread thereto have a different thread pitch, a different thread rotation direction or both a different thread pitch and a different thread rotation direction than the pressure ring internal thread of the pressure ring and the socket external thread of the threaded socket designed as a counter thread thereto, and wherein the pressure plate can be or is connected to the pressure ring in a torque-resistant manner via a connecting section.

[0019] The essential connecting elements according to the invention, namely the threaded connection piece, thrust ring, and thrust plate, serve to connect the diaphragm to a drive shaft of a diaphragm pump by screwing. They ensure that the thrust plate, with its internal thread, which is screwed to the external thread on a drive shaft, is in a torque-resistant relationship with the diaphragm and does not detach from the diaphragm or the threaded connection piece on the diaphragm when the diaphragm is unscrewed from the drive shaft and does not remain on the drive shaft, even if loosening the screw connection to the drive shaft is difficult and requires a high torque.

[0020] To assemble the membrane system according to the invention, the pressure ring with the pressure ring internal thread is first screwed onto the external thread of the threaded connector connected to the membrane, preferably until the pressure ring rests against the membrane. The pressure plate with the pressure plate external thread is then screwed into the internal thread of the threaded connector, which serves as a counter-thread. The pressure plate is then torque-tightly connected to the pressure ring.

[0021] For the torque-resistant connection of the pressure plate to the pressure ring, the pressure plate preferably has at least one connecting section extending radially outward from the end of its cylindrical portion facing away from the diaphragm, which extends at least as far as the pressure ring or beyond its end facing away from the diaphragm. The torque-resistant connection of the pressure plate to the pressure ring is achieved via the connecting section of the pressure plate, preferably by gluing the pressure plate to the pressure ring.

[0022] In a preferred embodiment, the connecting section is designed as a circular disk that extends radially outward from the cylindrical section of the pressure plate. The cylindrical section of the pressure plate is thus perpendicular to the circular disk, so that the pressure plate has a substantially hat-shaped cross section.

[0023] In an alternative embodiment, two or more connecting sections designed as webs or tabs are provided, which extend radially outward from the cylindrical section.

[0024] In a preferred embodiment, the torque-resistant connection between the pressure plate and the pressure ring is an adhesive connection. For this purpose, an adhesive is expediently applied to the pressure ring before the pressure plate is screwed into the internal thread of the threaded socket using the pressure plate external thread, or at least before the pressure plate is fully screwed in and there is still a gap between the pressure ring and the connecting section or sections of the pressure plate that allows the introduction of adhesive. As soon as the adhesive has cured, the pressure plate and the pressure ring are firmly connected to one another, in particular in a torque-resistant manner. The pressure plate and / or the pressure ring expediently also have structures that enlarge the surfaces on which the adhesive can spread and adhere, for a stronger connection.In addition, projections, recesses and / or undercuts can be provided on the pressure plate and / or pressure ring, which are surrounded by the adhesive in the not yet cured state and, after the adhesive has cured, also bring about a positive connection between the pressure plate and the pressure ring in addition to the additional adhesive surfaces thus formed.

[0025] In one embodiment of the invention, the pressure ring has at least one recess or groove open in the direction of the pressure plate or at least one connecting section of the pressure plate. Profiled features such as elevations, projections, pins, recesses or undercuts can also be provided on the wall surfaces in the recess or groove. If, when gluing the pressure plate to the pressure ring, adhesive is also applied to the recess or groove on the pressure ring in addition to the adhesive being applied to the contacting surfaces of the pressure ring and pressure plate, a particularly stable connection is formed between the pressure ring and pressure plate after the adhesive has hardened due to the additional adhesive surfaces and any profiled features present in the recess or groove.

[0026] The invention also encompasses alternative connections for the torque-resistant connection of the pressure plate to the pressure ring, including a welded connection, a bolted connection, a positive connection, a snap-in connection or a combination of two or more of the aforementioned connections.

[0027] A welded joint can be created, for example, by ultrasonic welding or laser welding, if the connecting section of the pressure plate and the pressure ring are made of weldable materials, such as a thermoplastic polymer. Suitable materials and techniques for this purpose are generally known, and, with knowledge of the present invention, their selection lies within the skill of the skilled person.

[0028] A bolt connection can be created, for example, by inserting one or more bolts, e.g. screws, rivets, cotter pins, etc., into corresponding receptacles or holes with or without threads in the connecting section of the pressure plate and in the pressure ring.

[0029] For a positive connection or a locking connection, corresponding structures are provided on the connecting section of the pressure plate and on the pressure ring, for example, a toothing with insertion bevels on one component and corresponding locking surfaces on the other component, into which the toothing can engage, so that when the pressure plate is screwed with the pressure plate external thread into the socket internal thread of the threaded socket, a positive or locking engagement occurs between the connecting section of the pressure plate and the pressure ring. With knowledge of the present invention, the selection and arrangement of corresponding structures lies within the skill of the expert.

[0030] The combination of the torque-resistant connection between the pressure plate and the thrust ring with the different thread designs—namely, the pressure plate external thread and the nozzle internal thread on the one hand, and the pressure ring internal thread and the nozzle external thread on the other—creates a self-locking effect that prevents the pressure plate connected to the pressure ring from unscrewing from the threaded nozzle. This self-locking effect prevents the pressure plate from becoming detached from the diaphragm or the threaded nozzle on the diaphragm when unscrewing the diaphragm from the drive shaft of a diaphragm pump, leaving it on the drive shaft.

[0031] In a preferred embodiment of the invention, the threaded connector is firmly connected to the membrane. Particularly preferably, the threaded connector is made of the same material as the membrane. The integral construction of the threaded connector with the membrane ensures a secure and firm connection between these two functional elements.

[0032] The invention has particular advantages when used with membranes made of PTFE or other materials that are difficult to bond or weld to the materials of the connecting elements, but it is fundamentally not limited to such membrane materials. In a particularly preferred embodiment of the invention, the membrane is therefore made of PTFE in one piece with the threaded connector.

[0033] The thrust ring is preferably made of a hard polymer material, which gives the thrust ring structural stability and ensures a stable screw connection with the threaded connector. In a preferred embodiment of the invention, the thrust ring is made of polyphenyl ether (PPE) or a derivative thereof, or of a polymer blend containing polyphenyl ether (PPE) or a derivative thereof, or of a polymer alloy containing polyphenyl ether (PPE) or a derivative thereof. Preferably, the polymer, polymer blend, or polymer alloy is glass fiber reinforced. The use of polyphenyl ether ensures high heat resistance, dimensional stability, and dimensional accuracy of the thrust ring made from it. By adding glass fibers, the properties such as hardness, compressive strength, and dimensional accuracy of the polymer material can be further increased.In one embodiment of the invention, the pressure ring is therefore made of glass fiber reinforced polyphenyl ether (PPE+GF). In an alternative embodiment, the pressure ring is made of metal or a metal alloy, preferably brass.

[0034] The pressure plate is preferably made of metal or a metal alloy, particularly preferably brass, which gives the pressure plate high structural stability and ensures a stable screw connection with the threaded connector. The metal, for example, brass, can be bonded to the pressure ring made of hard polymer material using an adhesive bond, providing a stable and torque-resistant connection.

[0035] In an alternative embodiment, the pressure plate, like the pressure ring, is made of a hard polymer material. The pressure plate can also be made of polyphenyl ether (PPE) or a derivative thereof, or of a polymer blend containing polyphenyl ether (PPE) or a derivative thereof, or of a polymer alloy containing polyphenyl ether (PPE) or a derivative thereof, and can preferably also be glass fiber reinforced.

[0036] The invention also encompasses embodiments in which the pressure plate, in addition to the torque-resistant connection to the pressure ring, has at least one bolt or locking pin which extends through the connecting section of the pressure plate into the cylindrical section of the threaded connector. This ensures additional torque protection of the pressure plate relative to the threaded connector. In one embodiment, for such additional protection, at least one through-hole is provided in the connecting section of the pressure plate, through which a bolt or locking pin is passed after the pressure plate external thread of the pressure plate has been screwed to the connector internal thread of the threaded connector and is inserted, driven in, or screwed into the material of the threaded connector. If the threaded connector is made of the comparatively soft material PTFE, for example, a pin can be driven into the material of the threaded connector.Alternatively, a bolt with a self-tapping or self-drilling thread can be screwed into the material of the threaded socket and anchored there.

[0037] The invention also includes a diaphragm pump for conveying a fluid, which has a diaphragm system according to the invention and a drive shaft which is designed for an oscillating translational movement perpendicular to the diaphragm plane during operation of the diaphragm pump and has an external thread at one end section for engagement with the diaphragm system by screwing. FIGURES

[0038] Further advantages, features, and possible applications of the present invention will become clear from the following description and the accompanying figures. In the figures, identical elements are designated by identical reference numerals. Fig. 1 shows a cross-sectional view of an embodiment of a membrane system according to the invention with a membrane, a threaded connector formed integrally with the membrane, a pressure ring and a pressure plate in assembly. Fig. 2 shows various views of the membrane with the threaded connector integrally formed thereon according to the Fig. 1 shown embodiment (a) in a view from above ( Fig. 2a), (b) in a cross-sectional view along the line AA ( Fig. 2b) and (c) in a perspective view ( Fig. 2c). Fig. 3 shows different views of the pressure ring according to the Fig. 1 shown embodiment (a) in a view from below ( Fig. 3a), (b) in a cross-sectional view along the line AA ( Fig. 3b) and (c) in a perspective view ( Fig. 3c). Fig. 4 shows different views of the printing plate according to the Fig. 1 shown embodiment (a) in a view from above ( Fig. 4a), (b) in a cross-sectional view along the line AA ( Fig. 4b) and (c) in a perspective view ( Fig. 4c). Fig. 5 shows a cross-sectional view ( Fig. 5a) of a membrane system according to the state of the art with a membrane, a pin formed integrally with the membrane and a membrane pressure piece in assembly as well as a perspective view ( Fig. 5b) the membrane with a pin integrally formed thereon.

[0039] The Fig. 1 to Fig. 4 show various representations and views of an embodiment of a membrane system according to the invention with a PTFE membrane 1, a threaded connector 2 formed integrally with the membrane 1 and therefore also made of PTFE, a pressure ring 5 and a pressure plate 8. Fig. 1 shows a cross-sectional view of the membrane system in assembly, while the Fig. 2 to Fig. 4 which in Fig. 1 connected components membrane 1 with threaded connector 2, pressure ring 5 and pressure plate 8 each individually in different views.

[0040] The membrane 1 is essentially circular in shape. As can be seen in the cross-sectional view of the Fig. 1 and also in the Fig. 2b and Fig. As can be seen in Figure 2c, the diaphragm 1 is thicker at its circumferential edge than in the sections further inward, since the diaphragm is usually firmly and fluid-tightly connected to the housing of the discharge chamber of a diaphragm pump at its circumferential edge by clamping the circumferential edge of the diaphragm between housing parts of the discharge chamber and the working chamber of the diaphragm pump. The sections of the diaphragm further inward, starting from the circumferential edge, are initially thinner in order to ensure sufficient flexibility and bendability during the oscillating back and forth movement of the diaphragm during operation, with the material of the diaphragm becoming thicker towards the center for a stable and rigid structure in the one-piece design with the threaded connector 2 adjoining the diaphragm 1.

[0041] The threaded connector 2 essentially comprises or consists of a cylindrical section arranged coaxially with the axis perpendicular to the membrane plane and passing through the center of the membrane. On the outer side of the cylindrical section, the threaded connector 2 has an external thread 3 for screwing to the pressure ring 5, and on the opposite inner side of the cylindrical section, an internal thread 4 for screwing to the pressure plate 8.

[0042] The pressure ring 5 comprises a cylindrical section which is arranged coaxially to the cylindrical section of the threaded connector 2 and has, on the inside of the lateral surface of its cylindrical section, a pressure ring internal thread 6 which is designed for screwing onto the threaded connector 2 as a counter thread to the connector external thread 3. In the present embodiment, the pressure ring is made of glass fiber reinforced polyphenyl ether (PPE+GF). Fig. 1 and Fig. The blind holes 14 shown in Figure 3 on the pressure ring 5 serve to engage a tool when screwing the pressure ring onto the threaded socket 2.

[0043] The pressure plate 8 also has a cylindrical section which is arranged coaxially to the cylindrical section of the threaded connector 2, and on the outside of the outer surface of its cylindrical section a pressure plate external thread 9 which is designed as a counter thread to the connector internal thread 4 of the threaded connector 2, and on the inside of the outer surface of its cylindrical section a pressure plate internal thread 10 which is designed for connection to the external thread on an end section of a drive shaft of a diaphragm pump.

[0044] Furthermore, the cylindrical portion of the pressure plate 8 is adjoined by a connecting portion formed as a circular disk, which extends radially outward from the cylindrical portion of the pressure plate 8. The cylindrical portion of the pressure plate is thus perpendicular to the circular disk, so that the pressure plate has a substantially hat-shaped cross section. In the present embodiment, the pressure plate 8 is made of brass.

[0045] To assemble the membrane system according to the invention, the pressure ring 5 with the pressure ring internal thread 6 is first screwed onto the socket external thread 3 of the threaded socket 2 until the pressure ring rests against the membrane. In the present embodiment, an adhesive connection is created between the pressure plate 8 and the pressure ring 5 to achieve the torque-resistant connection required according to the invention. For this purpose, after the pressure ring 5 has been screwed onto the threaded socket 2, an adhesive is applied to the pressure ring 5 and then the pressure plate 8 with the pressure plate external thread 9 is screwed into the socket internal thread 4 of the threaded socket 2. In the present embodiment, the pressure ring 5 additionally has a circumferential groove 7 that is open in the direction of the pressure plate 8 and into which adhesive is also introduced in order to achieve a particularly stable connection between the pressure ring 5 and the pressure plate 8 after the adhesive has hardened.Furthermore, in the present embodiment, two additional bores 13 are provided in the connecting section 11 of the pressure plate 8, into which adhesive can also penetrate, creating additional adhesive surfaces and, after the adhesive has cured, additional sections with a positive connection that prevents rotational movement of the pressure plate 8 relative to the pressure ring 5. Once the adhesive has cured, the pressure plate 8 and the pressure ring 5 are firmly connected to one another, in particular in a torque-resistant manner.

[0046] In the present embodiment, the external thread 3 of the threaded connector 2 and the internal thread 6 of the thrust ring 5 are designed as right-hand M18 × 1.25 fine threads, while the internal thread 4 of the threaded connector 2 and the external thread 9 of the thrust plate 8 are designed as right-hand M8 × 0.75 fine threads. An M5 × 0.8 standard thread is provided as the internal thread 10 of the thrust plate for screwing to the drive shaft of a diaphragm pump. Alternatively, right-hand and left-hand threads with the same or different thread pitches can be combined.

[0047] By combining the torque-resistant connection between pressure plate 8 and pressure ring 5 with the different thread pitches (or different thread speeds) on the pressure plate external thread 9 and nozzle internal thread 4 on the one hand and pressure ring internal thread 6 and nozzle external thread 9 on the other hand, a self-locking effect is achieved against unscrewing the pressure plate 8 connected to the pressure ring 5 from the threaded nozzle 2. The self-locking effect prevents the pressure plate 8 from becoming detached from the threaded nozzle 2 on the diaphragm 1 when the diaphragm is unscrewed from the drive shaft of a diaphragm pump and from remaining on the drive shaft.

[0048] In the present embodiment, two through-openings 12 are provided in the circular disk-shaped connecting section 11 of the pressure plate 8, through which, in addition to the torque-resistant adhesive connection with the pressure ring, bolts or locking pins (not shown here) can be introduced and anchored in the comparatively soft PTFE material of the cylindrical section of the threaded connector 2. This ensures additional torque protection of the pressure plate 8 relative to the threaded connector 2. Simple metal pins, preferably sharpened for easier driving into the material of the threaded connector 2, or alternatively screws with a self-tapping or self-drilling thread, can be used as bolts or locking pins.

[0049] Fig. Figure 5a shows a cross-sectional view of a membrane system according to the prior art described above, comprising a PTFE membrane 20, which is made in one piece with a PTFE pin 21 arranged centrally on the membrane 20 and extending perpendicular to the membrane plane. The pin 21 has a circular cross-section and has an external thread 22 on its circumferential surface. A substantially cylindrical membrane pressure piece 23 made of a hard polymer material is screwed onto the PTFE pin 21. For this purpose, the cylindrical membrane pressure piece 23 has a first internal thread 24 extending from one end of the cylinder, which is designed as a counter thread for screwing into the external thread 22 of the pin 21.Starting from the opposite end of the cylindrical diaphragm pressure piece 23, a second pressure piece internal thread 25 is provided, which is designed as a counter thread to the external thread on the drive shaft of a diaphragm pump and is intended for connecting the diaphragm to the drive shaft. Fig. 5b shows a perspective view of the PTFE membrane 20 with the pin 21, which is manufactured in one piece therewith and extends perpendicular to the membrane plane, without the membrane pressure piece attached thereto.

[0050] Since the diaphragm pressure piece 23 is merely screwed onto the PTFE pin 21, one or more metal bolts or split pins (not shown here) must be driven through one or more holes in the diaphragm pressure piece (not shown here) into the PTFE material of the pin in order to secure the diaphragm pressure piece 23 to the PTFE pin 21 in a torque-resistant manner. This ensures that the diaphragm 20 with the pin 21 does not detach from the diaphragm pressure piece 23 when unscrewed from a drive shaft for disassembly or replacement, and that the diaphragm pressure piece remains on the thread of the drive shaft.

[0051] A comparison of the Fig. 1 and Fig. 5 shows a further disadvantage of the prior art design, namely that the cylindrical membrane pressure piece 23 must be comparatively long, since it must accommodate a thread from both ends, which in turn limits the usability of such PTFE membranes.

[0052] For the purposes of original disclosure, it is noted that all features as they become apparent to a person skilled in the art from the present description, the drawings, and the claims, even if they were specifically described only in conjunction with certain other features, can be combined both individually and in any combination with other features or groups of features disclosed herein, unless expressly excluded or technical circumstances render such combinations impossible or pointless. A comprehensive, explicit presentation of all conceivable combinations of features is omitted here solely for the sake of brevity and readability of the description.

[0053] While the invention has been illustrated and described in detail in the drawings and the foregoing description, this illustrative description is provided by way of example only and is not intended to limit the scope of protection as defined by the claims. The invention is not limited to the illustrated embodiments.

[0054] Modifications of the disclosed embodiments will be apparent to those skilled in the art from the drawings, the description, and the appended claims. In the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are claimed in different claims does not preclude their combination. LIST OF REFERENCE SYMBOLS 1 membrane 2 threaded connectors 3 male threads 4 female threads 5 Pressure ring 6 pressure ring internal thread 7 Groove on the pressure ring 8 printing plate 9 pressure plate external thread 10 pressure plate internal threads 11 Connecting section of the pressure plate 12 Through hole at the connecting section of the pressure plate 13 holes on the pressure plate 14 blind holes for tool engagement on the pressure ring 20 membrane 21 cones 22 male thread 23 Diaphragm pressure piece 24 first pressure piece internal thread 25 second pressure piece internal thread

Claims

[1] Membrane system with a membrane (1) and connecting elements (2, 5, 8) for connecting the membrane to a membrane pump for conveying a fluid, which has a drive axis which is designed for an oscillating translational movement perpendicular to the membrane plane during operation of the membrane pump and has an external thread at one end section for engagement with the membrane system by screwing, characterized by , that the connecting elements comprise a threaded connector (2), a pressure ring (5) and a pressure plate (8), whereby the threaded connector (2) - has a cylindrical section arranged coaxially with an axis perpendicular to the plane of the membrane, - is firmly or detachably connected to the membrane (1), - has a male thread (3) on the outside of the lateral surface of its cylindrical section and - has an internal thread (4), preferably a blind hole thread, on the inside of the lateral surface of its cylindrical section, wherein the pressure ring (5) - has a cylindrical portion arranged coaxially with the cylindrical portion of the threaded connector, and - on the inside of the lateral surface of its cylindrical section, has a pressure ring internal thread (6) which is designed as a counter thread to the socket external thread (3) of the threaded socket (2), wherein the pressure plate (8) - has a cylindrical section which is arranged coaxially to the cylindrical section of the threaded connector (2), - on the outside of the lateral surface of its cylindrical section, has a pressure plate external thread (9) which is designed as a counter thread to the socket internal thread (4) of the threaded socket (2), and - on the inside of the lateral surface of its cylindrical section, has a pressure plate internal thread (10) which is designed for connection to the external thread on an end section of a drive shaft of a diaphragm pump, wherein the pressure plate external thread (9) of the pressure plate (8) and the socket internal thread (4) of the threaded socket (2) designed as a counter thread thereto have a different thread pitch, a different thread rotation direction or both a different thread pitch and a different thread rotation direction than the pressure ring internal thread (6) of the pressure ring (5) and the socket external thread (3) of the threaded socket (2) designed as a counter thread thereto, and wherein the pressure plate (8) can be or is connected to the pressure ring (5) in a torque-resistant manner via a connecting section (11). [2] Membrane system according to claim 1, wherein the pressure plate (8) has at least one connecting portion (11) extending radially outwardly from the end of its cylindrical portion facing away from the membrane (1), which connecting portion extends at least as far as the pressure ring or beyond its end facing away from the membrane (1). [3] Membrane system according to one of the preceding claims, wherein on the pressure plate (8) - a connecting section (11) is provided which extends radially outwards from the cylindrical section of the pressure plate in the shape of a circular disk, or - two or more connecting sections are provided which are formed as webs or tabs extending radially outward from the cylindrical section of the pressure plate. [4] Membrane system according to one of the preceding claims, wherein the torque-resistant connection of the pressure plate (8) to the pressure ring (5) is an adhesive connection, a welded connection, a bolted connection, a positive connection, a snap-in connection or a combination of two or more of the aforementioned connections. [5] Membrane system according to one of the preceding claims, wherein the pressure ring (5) has at least one recess or groove open in the direction of the pressure plate. [6] Membrane system according to one of the preceding claims, wherein the threaded connector (2) is made in one piece with the membrane (1) from the same material. [7] Membrane system according to one of the preceding claims, wherein the membrane (1) is made of polytetrafluoroethylene (PTFE) and / or the threaded connector (2) is made of polytetrafluoroethylene (PTFE) and / or the pressure ring (5) is made of polyphenyl ether (PPE) or a derivative thereof or of a polymer blend containing polyphenyl ether (PPE) or a derivative thereof or of a polymer alloy containing polyphenyl ether (PPE) or a derivative thereof, wherein the polymer, the polymer blend or the polymer alloy is preferably glass fiber reinforced, and / or the pressure plate (8) is made of metal or a metal alloy, preferably of brass. [8] Membrane system according to one of the preceding claims, wherein the membrane system further comprises at least one bolt or locking pin which extends through the connecting portion (11) of the pressure plate (8), preferably through through openings in the connecting portion (11) of the pressure plate (8), into the cylindrical portion of the threaded connector (2). [9] Diaphragm pump for conveying a fluid, which has a diaphragm system according to one of the preceding claims and a drive shaft which is designed for an oscillating translational movement perpendicular to the diaphragm plane during operation of the diaphragm pump and has an external thread at one end portion for engagement with the diaphragm system by screwing.

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