File member

Abstract

Metering diaphragm for use in a metering diaphragm pump, comprising an outer section designed to be clamped and an inner section movable relative to the outer section, wherein the metering diaphragm has a first side designed to come into contact with a metering fluid and a second side designed not to come into contact with a metering fluid, characterized in that the first side is made at least partially of polyethylene, and preferably the first side is made entirely of polyethylene.

Description

[0001] The present invention relates to a metering diaphragm for use in a metering diaphragm pump.

[0002] Metering diaphragm pumps are well known. In metering diaphragm pumps, the metering diaphragm defines a metering chamber, which has an inlet and an outlet, which can usually be opened and closed using a check valve. By moving the metering diaphragm during pumping operation, the volume of the metering chamber can be alternately reduced or increased, so that the inlet and outlet are alternately opened and closed, respectively, to draw metering fluid into the metering chamber via the inlet and expel it from the metering chamber via the outlet.

[0003] The metering diaphragm is often clamped with an outer section between two elements of the metering diaphragm pump. The inner section, which is not clamped, is then movable relative to the outer section.

[0004] The dosing diaphragm is usually flat, so it has a first and a second side. The first side is intended to come into contact with a dosing fluid. The opposite side, the second side, does not come into contact with a dosing fluid.

[0005] Composite membranes consisting of several layers are often used as metering membranes. Membranes made of metal, PTFE, and PTFE-coated membranes are also common.

[0006] Composite diaphragms cannot be used for all dosing fluids. Especially with outgassing media, these diaphragms must be replaced after a short period of time. They are also prone to breakage, so additional diaphragm indicators are required. PTFE coatings are difficult to produce.

[0007] Metal diaphragms are generally only suitable for small dosing volumes. Furthermore, they are completely unsuitable for pumping some media.

[0008] Based on the described prior art, it is therefore an object of the present invention to provide a metering membrane which at least reduces the described disadvantages.

[0009] According to the invention, this object is achieved in that the first side of the metering membrane, i.e., the side intended to come into contact with the metering fluid, is made at least in sections of polyethylene. At least those sections that come into contact with the metering fluid are advantageously made of polyethylene. In particular, the outer section, which is clamped, could also be made of a different material. In a preferred embodiment, the first side is made entirely of polyethylene.

[0010] Polyethylene is one of the most widely used plastics. It is typically used in packaging materials and films.

[0011] Its mechanical properties are rather poor compared to other plastics. However, it has been shown that polyethylene is ideally suited for the operation of a metering diaphragm pump, due in part to its high chemical resistance. Polyethylene is easy to process and compatible with almost all types of metering fluids. While its strength, hardness, and stiffness are comparatively low, its extensibility is high.

[0012] There are various types of polyethylene, which differ in density, length, and degree of branching. The right type of polyethylene can be selected depending on the application. Polyethylene therefore also includes the corresponding types such as PE-LD, PE-MD, PE-HD, or even PE-1000 or PE-UHMW.

[0013] In a preferred embodiment, the second side is also made of polyethylene, at least in sections, with at least the inner section and particularly preferably also the outer section of the second side being made of polyethylene. Constructing the second side with polyethylene increases the durability of the metering membrane.

[0014] In particular, if the outer sections on both the first and second sides are made of polyethylene, the metering diaphragm can usually be removed from the pump head almost undamaged and reused if necessary.

[0015] The metering diaphragm can be moved in a variety of ways. For example, the metering diaphragm can be moved toward the metering chamber using hydraulic oil. However, to ensure the metering diaphragm can be moved back in the opposite direction quickly enough, a spring is often used to preload the diaphragm in a direction where the volume of the metering chamber is maximized.

[0016] Therefore, in the preferred embodiment, a fastening means is provided on the second side of the metering diaphragm. For example, this can be a bore with an internal thread, allowing a corresponding threaded rod to be screwed in, which can be used to move the metering diaphragm.

[0017] In a particularly preferred embodiment, the fastening means is made of polyethylene, into which, for example, a corresponding threaded hole has been introduced. Due to the good processability of polyethylene, it can be machined, allowing structures to be drilled or milled, for example. Alternatively, an insert made of plastic or metal (e.g., brass) with a threaded bushing can be inserted into the second side. For example, the metering diaphragm could be manufactured at least on its second side using an injection molding process, and the insert could simply be overmolded.

[0018] In principle, it is possible to use a composite membrane and apply a polyethylene coating to the first and / or second side. To coat composite membranes using a PE film, the surface of the film is plasma-activated or plasma-etched. An adhesive layer, such as double-sided tape or liquid adhesive, can then be applied. To apply the PE film to a substrate, it should be cleaned and then coated with an adhesion promoter. The prepared film can then be applied to the substrate, such as EPDM or FKM, to create the finished composite membrane.

[0019] However, an embodiment in which the metering membrane is made entirely or substantially entirely of polyethylene is particularly preferred. For example, an insert element made of a different material could be inserted into a metering membrane otherwise made of polyethylene.

[0020] In a preferred embodiment, the inner section has a central section and a flexed section surrounding the central section. The flexed section connects to both the outer section, which is clamped, and the central section. The actual deformation of the membrane occurs in the flexed section. The central section remains largely undeformed, but can move relative to the outer section due to the connection via the flexed section.

[0021] Preferably, the flexed section has a thickness that is less than the thickness of the central section. The thickness of the flexed section can also be less than the thickness of the outer section that is clamped.

[0022] In a preferred embodiment, the thickness of the central section is greater than the thickness of the outer section.

[0023] The central portion may have a substantially cylindrical projection on the second side of the metering diaphragm. The fastening means, such as a threaded bushing, can be attached in or to this cylindrical projection.

[0024] In a further preferred embodiment, the central section comprises a central part and a pressure ring. The central section is thus constructed in two parts, which simplifies production. The central section can also consist of more than two parts.

[0025] For example, the central part can have an external thread and the pressure ring an internal thread, so that the pressure ring can be screwed or screwed onto the central part.

[0026] The central part can be designed in a stepped manner, so that the central part has a smaller width in the area in which the external thread is arranged than in the area which is connected to the flexed section.

[0027] Furthermore, in a preferred embodiment, the pressure ring can have an extension in the width direction that is greater than the width of the central part. Preferably, the pressure ring has a support surface facing away from the second side of the membrane, and the flexed section has a first and a second segment, wherein the first segment is arranged closer to the outer section than the second segment, wherein the second segment is in contact with the support surface or can be brought into contact with it.

[0028] In other words, in a specific diaphragm position, the second segment can come into contact with the support surface and be supported by it. The metering diaphragm is advantageously dimensioned such that when the metering diaphragm is clamped with the outer section and the central section is moved towards the first side, the second segment comes into contact with the support surface, and when the metering diaphragm is clamped with the outer section and the central section is moved towards the second side, the second segment comes out of contact with the support surface. As a result, the second segment only takes part in the flexing movement in one direction of movement, i.e. when it is not in contact with the support surface. This design relieves the load on the connection point between the flexing section and the central section, thereby extending the service life of the diaphragm.

[0029] In the case of the multi-part design of the central section, the pressure ring can be made of any material, although the use of polyethylene is preferred here too.

[0030] The metering diaphragm, including the cylindrical protrusion of the central section, can be manufactured by injection molding. A threaded bushing as a fastening element, made of brass or a plastic such as PPE + GF or PA + GF, can be overmolded. GF stands for a glass fiber component, which is added to reinforce the plastic. To simplify the injection molding process, the cylindrical projection of the central section can have one or more recesses. For example, the recesses can extend coaxially to the cylinder axis of the cylindrical projection in a partially circular shape, so that the cylindrical projection is formed by a plurality of hollow cylinders whose wall thickness approximately corresponds to the wall thickness of the metering diaphragm in the flexion area or in the outer section.

[0031] In the multi-part design of the central section, both the central part and the thrust ring can be manufactured by injection molding. The thrust ring can also have correspondingly shaped recesses.

[0032] On the opposite first side, the flexed section can form a plane, with the central section and preferably also the outer section projecting beyond this plane. It has been shown that this design can improve the movement of the metering membrane according to the invention.

[0033] The dosing membrane can also be manufactured using 3D printing or machining.

[0034] Further advantages, features, and possible applications of the present invention will become clear from the following description of two preferred embodiments and the accompanying figures. They show: Fig. 1a to 1e show various views of a first embodiment of the invention, Fig. 2a to 2d show various views of a second embodiment of the invention and Fig. 3a to 3e different views of a third embodiment of the invention.

[0035] In the Fig. Figures 1a to 1e show a first embodiment of a metering membrane 1 according to the invention, which is made entirely of polyethylene. This metering membrane was manufactured by machining.

[0036] The Fig. 1a and Fig. 1b show two perspective views of this embodiment. In Fig. 1a shows the first side 2 of the dosing membrane 1, which is intended to come into contact with a dosing fluid, while in Fig. 1b the second side 3, which should not come into contact with the dosing fluid, can be seen.

[0037] In the Fig. 1c shows a view of the second side 3 of the metering membrane. Fig. 1d shows a side view of the metering membrane of the first embodiment. Fig. Figure 1e shows a sectional view along the line AA (in Fig. 1c).

[0038] A threaded bushing 4 is inserted into the second side 3 of the dosing diaphragm 1, into which, for example, a push rod can be screwed in order to move the dosing diaphragm 1 to carry out the pumping process.

[0039] The metering membrane 1 has an outer section 5, which is intended to be clamped, and an inner section 6,7, which is movable relative to the outer section 5. The inner section 6,7 in turn consists of a central section 7 and a flexed section 6 surrounding the central section. The outer section 5 is essentially circular with a ring width a. The central section is essentially cylindrical with a diameter c. Between the central section 7 and the outer section 5, the flexed section 6 is arranged, which is also circular with a ring width b. In the sectional view of Fig. 1e it can be seen that the flexed section 6 has a thickness which is much smaller than the thickness of the central section 7 and also smaller than the thickness of the outer section 5. Fig. 1e, the flexed section 6 is in one plane, and both the central section 7 and the outer section 5 protrude beyond this plane on the first side 2. In other words, the flexed section 6 is formed as a groove on the first side 2. The central section 7 and the flexed section 6 are connected to each other on both the first side 2 and the second side 3 via curved surface sections. These curved surface sections should have a radius of curvature of more than 1 mm, preferably more than 1.5 mm, and most preferably between 1.6 mm and 3 mm.

[0040] In the Fig. 2a to 2d show various views of a second embodiment of a metering membrane 11 according to the invention, which has been manufactured by injection molding.

[0041] The Fig. Figure 2a shows a perspective view of this embodiment. Fig. 2a shows the second side 13, which should not come into contact with the dosing fluid.

[0042] In the Fig. 2b shows a plan view of the second side 13 of the metering membrane 11. In the Fig. 2c and Fig. 2d are sectional views along lines AA (in Fig. 2b) or BB (in Fig. 2b) is shown.

[0043] A threaded bushing 14 is inserted into the second side 13 of the dosing diaphragm 11, into which, for example, a push rod can be screwed in order to move the dosing diaphragm 11 to effect the pumping process.

[0044] The metering diaphragm 11 has an outer section 15, which is intended to be clamped, and an inner section 6, 7, which is movable relative to the outer section 15. The inner section 16, 17 in turn consists of a central section 17 and a flexed section 16 enclosing the central section. The outer section 15 is essentially circular with a ring width a. The central section 17 is essentially cylindrical with a diameter c. Arranged between the central section 17 and the outer section 15 is the flexed section 16, which is also circular with a ring width b.

[0045] In the sectional view of Fig. 2c it can be seen that the flexed section 16 has a thickness which is much smaller than the thickness of the central section 17 and also smaller than the thickness of the outer section 15. Fig. 2c, the flexed section 16 is in one plane, and both the central section 17 and the outer section 15 protrude beyond this plane on the first side 12. In other words, the flexed section 16 is formed as a groove on the first side 12.

[0046] The central section 17 has a plurality of recesses 18 arranged such that the central section 17 essentially consists of a plurality of hollow cylinders closed on the first side 12 and connected to one another by radially extending webs. The recesses save material and facilitate injection molding. The recesses 18 are formed such that the remaining sections of the central section 17 have wall thicknesses that are of the same order of magnitude as the thickness of the outer section 15.

[0047] In the Fig. Figures 3a to 3e show a third embodiment of a metering membrane 21 according to the invention, which is made entirely of polyethylene. This metering membrane was manufactured by injection molding.

[0048] The Fig. 3a and Fig. 3b show two perspective views of this embodiment. In Fig. 3a shows the first side 22 of the dosing membrane 21, which is intended to come into contact with a dosing fluid, while in Fig. 3b the second side 23, which is not intended to come into contact with the dosing fluid, can be seen.

[0049] In the Fig. 3c shows a view of the second side 23 of the metering membrane. Fig. 3d shows a side view of the metering membrane 21 of the third embodiment. Fig. 3e shows a sectional view (as in Fig. 1e).

[0050] Here too, a threaded bushing 24 is introduced into the second side 23 of the metering diaphragm 21, into which, for example, a push rod can be screwed in order to move the metering diaphragm 21 to effect the pumping process.

[0051] The metering diaphragm 21 has an outer section 25, which is intended to be clamped, and an inner section 26, 27, which is movable relative to the outer section 5. The inner section 26, 27 in turn consists of a central section 27 and a milled section 26 enclosing the central section. The outer section 25 is essentially circular with a ring width a. The central section 27 is stepped here. On the first side, the central section 27 has a diameter c. On the second side, the central section 27 has a diameter e which is larger than the diameter c. Arranged between the central section 27 and the outer section 25 is the milled section 26, which is also circular with a ring width b.

[0052] In the sectional view of Fig. 3e it can be seen that the flexed section 26 has a thickness which is much smaller than the thickness of the central section 27 and also smaller than the thickness of the outer section 25. Fig. 3e the fulling section 26 is in one plane and both the central section 27 and the outer section 25 project beyond this plane on the first side 2.

[0053] In other words, the flexed section 26 on the first side 22 is formed as a groove. The central section 27 and the flexed section 26 are connected to each other on the first side 22 via curved surface sections. These curved surface sections should have a radius of curvature of more than 1 mm, preferably more than 1.5 mm, and most preferably between 1.6 mm and 3 mm.

[0054] In contrast to the first and second embodiments, the central section 27 is formed in two parts here and consists of the central part 31 and the pressure ring 30. The central part 31 is almost cylindrical and has a diameter d which is smaller than the diameter c of the central section 27 on the first side 22.

[0055] The central part 31 has an external thread. The thrust ring 30 is almost hollow-cylindrical in shape with an internal thread, so that the thrust ring 30 can be screwed onto the central part, as can be seen in the figures.

[0056] When the pressure ring 30 is screwed on, the width or diameter e of the central section 27 on the second side 23 is greater than the width or diameter c of the central section 27 on the first side 22.

[0057] The pressure ring 30 is connected to the central part 31 only via the thread, so that in the position shown in the figures, the pressure ring 30 rests with its side facing the flexion section 26 on its support surface 32 on the flexion section.

[0058] During operation, the membrane is clamped at its outer section 25 and the central section 27 is Fig. 3e is moved alternately to the right and left via a pressure rod (not shown) which is screwed into the threaded bushing 24. Since the outer section 25 is clamped, the flexion section 26 must manage the relative movement between the outer section 25 and the central section 27. During the compression stroke movement, ie the movement of the central section 27 in Fig. 3e to the left, a part of the flexed section 26 lies on the support surface 32 and does not participate in the deformation of the flexed section 26.

[0059] During the suction stroke movement, ie during the movement of the central section 27 in Fig. 3e to the right, the flexion section 26 detaches from the support surface 32 and fully participates in the deformation of the.

[0060] In the example shown, the thrust ring 30 is designed as a hollow cylinder. The walls of the hollow cylinder can have recesses that are identical to or similar to the recesses 28 in the central part 31.

[0061] To prevent the thrust ring 30 from detaching from the central part 31 during operation, it must be firmly connected to the central part 31. To apply the necessary torque, actuating openings 29 are provided in the thrust ring 30, into which an appropriate tool (not shown) can engage to rotate the thrust ring 30 relative to the central part 31. The resulting minimal gap between the inner surface of the thrust ring 30 and the outer surface of the central part can be welded, e.g., by ultrasonic welding. List of reference symbols 1,11,21 Dosing membrane 2,12,22 first side of the dosing membrane 3,13,23 second side of the dosing membrane 4,14,24 threaded bushing 5,15,25 outer section 6,16,26 walking section 7,17,27 Central section 18.28 recess 29 Operating hole 30 pressure ring 31 Central part 32 support surface

Claims

[1] Dosing diaphragm for use in a dosing diaphragm pump having an outer portion intended to be clamped and an inner portion movable relative to the outer portion, wherein the dosing diaphragm has a first side intended to come into contact with a dosing fluid and a second side intended not to come into contact with a dosing fluid, characterized by that the first side consists at least in sections of polyethylene, wherein preferably the first side consists entirely of polyethylene. [2] Dosing membrane according to one of the preceding claims, characterized by that the second side consists at least in sections of polyethylene, wherein preferably at least the inner section and particularly preferably also the outer section of the second side consists of polyethylene. [3] Dosing membrane according to one of the preceding claims, characterized bythat a fastening means, preferably a bore with an internal thread, is provided on the second side of the dosing membrane. [4] Dosing membrane according to claim 3, characterized by that the fastening means is made of polyethylene or an insert part which forms or has a threaded bushing is inserted into the second side. [5] Dosing membrane according to one of the preceding claims, characterized by that the first side has a polyethylene coating. [6] Dosing membrane according to one of claims 1 to 4, characterized by that the dosing membrane is made entirely of polyethylene. [7] Dosing membrane according to one of the preceding claims, characterized by that the inner section consists of a central section and a fulling section enclosing the central section, wherein the fulling section adjoins both the outer section and the central section. [8] Dosing membrane according to claim 7, characterized bythat the flexed section has a thickness which is less than the thickness of the central section and preferably also less than the thickness of the outer section. [9] Dosing membrane according to one of claims 7 or 8, characterized by that on the second side the central portion has a substantially cylindrical projection. [10] Dosing membrane according to one of claims 7 to 9, characterized by that the central section has a central part and a pressure ring, wherein preferably the central part has an external thread and the pressure ring has an internal thread, so that the pressure ring is screwed or can be screwed onto the central part. [11] Dosing membrane according to claim 10, characterized byin that the pressure ring has a support surface facing away from the second side of the membrane and the flexed section has a first and a second segment, the first segment being arranged closer to the outer section than the second segment, the second segment being in contact with the support surface or being able to be brought into contact, the metering membrane being dimensioned such that when the metering membrane is clamped to the outer section and the central section is moved in the direction of the first side, the second segment comes into contact with the support surface, and when the metering membrane is clamped to the outer section and the central section is moved in the direction of the second side, the second segment comes out of contact with the support surface. [12] Dosing membrane according to one of the preceding claims, characterized bythat the metering membrane is produced by injection molding, wherein preferably the cylindrical projection of the central portion has one or more recesses. [13] Dosing membrane according to one of the preceding claims, characterized by that the fulling section forms a plane on the first side, with the central section and preferably also the outer section projecting beyond this plane. [14] Dosing membrane according to one of the preceding claims, characterized by that the dosing membrane was manufactured using 3D printing. [15] Dosing membrane according to one of the preceding claims, characterized by that the dosing diaphragm was manufactured by machining.

Images