Diaphragm pump

Abstract

The invention relates to a diaphragm pump comprising a pump housing (2) which has a hydraulic chamber (6), and comprising a pump cover (3) which has a delivery chamber (7). A diaphragm (8) is clamped between the pump cover (3) and the pump housing (2) in a clamping region (10) in such a way that the hydraulic chamber (6) and the delivery chamber (7) are separated from one another. In the region of the centre of the delivery chamber (7), the pump cover (3) has an at least partially convex bulge (12) into the delivery chamber (7).

Description

[0001] DIAPHRAGM PUMP

[0002] The present invention relates to a diaphragm pump with a pump housing and a pump cover, wherein a diaphragm is clamped between the pump housing and the pump cover in a clamping area.

[0003] Diaphragm pumps of this type are available in a wide variety of configurations and can be driven in various ways, such as mechanically, pneumatically, or hydraulically. Diaphragm pumps are also used in a wide variety of applications and for conveying a variety of media, from gases and liquids to highly viscous fluids such as oils or butter. They can also be used as metering pumps.

[0004] For this purpose, the pump housing has a hydraulic chamber, and the pump cover has a discharge chamber. The diaphragm is clamped between the pump housing and the pump cover in the clamping area so that the hydraulic chamber is separated from the discharge chamber. Therefore, the diaphragm's primary function is to seal the discharge chamber from the hydraulic chamber, protecting both the hydraulic chamber and the discharge chamber from any harmful influences of the fluid being pumped, or the hydraulic fluid.

[0005] The diaphragm also serves to drive the medium to be pumped. For this purpose, the diaphragm can be designed as a flexible pressure diaphragm so that it can be deflected from its rest position by pressure. To do this, it is pressurized by a working medium in the hydraulic chamber. This can be done, for example, by means of a piston that is moved towards the hydraulic chamber by a drive such as a motor. To direct the diaphragm back into the hydraulic chamber, the piston is moved in the other direction so that the working medium is sucked in by the piston and a negative pressure is created in the hydraulic chamber. In other words, the negative pressure sucks the diaphragm into the hydraulic chamber.

[0006] Typical materials such a membrane can be made of include metals, such as stainless steel sheets, and plastics such as polytetrafluoroethylene (PTFE). However, the use of mixtures of different materials, such as composite materials, is also conceivable.

[0007] Since very high operating pressures are required for pumping highly viscous fluids, such as butter, metal diaphragms have typically been used. These have proven particularly reliable, especially with regard to leak tightness in the clamping area at very high pressures. This is due, among other things, to the fact that a PTFE diaphragm cannot be clamped with as much force and cannot be subjected to as high operating pressures as a sheet steel diaphragm.

[0008] This is because both the pump cover and the pump housing are repeatedly elastically deformed by the oscillating pressure fluctuations. The internal pressure in the delivery chamber as well as in the hydraulic chamber pushes the pump cover and the pump housing apart and away from the diaphragm, resulting in a gap between the pump cover and the diaphragm in the delivery chamber and a gap between the pump housing and the diaphragm in the hydraulic chamber. The pressurised working medium and also the pumped medium can infiltrate the clamping area through this gap. It has been shown that this leads to leaks along the diaphragm and expansion of the pump cover and pump housing in the clamping area. The higher the working pressure, the more pronounced this effect. In addition, the oscillating deformation in the clamping area can also lead to fatigue of the material.This limits the maximum operating pressure, especially for conventional diaphragm pumps with polytetrafluoroethylene (PTFE) diaphragms.

[0009] On the other hand, plastic diaphragms offer certain cost advantages over metal diaphragms. It is therefore desirable that plastic diaphragms can be used at higher operating pressures than before without compromising the pump's tightness.

[0010] The present invention is therefore based on the object of providing a diaphragm pump with improved sealing and reducing manufacturing costs.

[0011] The object is achieved according to the invention with a diaphragm pump according to claim 1. Advantageous developments of the invention emerge from the dependent claims 2 to 9.

[0012] The diaphragm pump according to the invention thus differs from a diaphragm pump of the generic type in that the pump cover in the region of the middle of the pumping chamber has an at least partially convex bulge into the pumping chamber.

[0013] The convex curvature of the pump cover, at least in some areas, offers particular advantages. For example, studies by the applicant have shown that the shape of the pump cover in the area of ​​the pumping chamber is of great importance. Conventional pump covers are flat in the center of the pumping chamber, and the inlet and outlet to the pumping chamber are angled. In the area of ​​the angle, high pressures can occur, which interact with the clamping area of ​​the diaphragm and promote the pressing of the pumped medium into the gap. The convex curvature according to the invention increases the rigidity of the pump cover, since deformation is greatest in the center of the pump cover. Although more material is required at this point, this disadvantage is more than compensated for by the increased tightness in the clamping area of ​​the diaphragm.

[0014] A further advantageous effect of the bulge is the change in the direction of pressure in the pumping chamber. Especially when the diaphragm is deflected into the pumping chamber to force the pumped medium out of the pumping chamber, the internal pressure on the pump cover is increased. The bulge at the edges ensures that the pumped medium flows towards the clamping area at almost a right angle and presses it against it. In this way, the pressure there is specifically increased so that elastic movement in the clamping area of ​​the diaphragm is reduced. This prevents the potential formation of a gap between the diaphragm and the pump cover in the clamping area and thus also prevents the pumped medium from seeping under through the gap. This in turn leads to greater tightness of the diaphragm in the clamping area. This design leads to an increase in the operating pressure when PTFE diaphragms are used in diaphragm pumps, even when the dimensions of the diaphragm pump remain the same.This results in cost advantages in production compared to diaphragm pumps with metal diaphragms.

[0015] In a further development, the convex bulge of the pump cover is spherical in shape, at least in some areas. "Spherical" specifically means that the radius of the spatial bulge is constant. The bulge in the pump cover is thus directed more radially outward. This further improves the flexural rigidity of the pump cover, especially when the diaphragm is deflected into the pumping chamber to force the pumped medium out of the chamber. The curves of the bulge toward the outlet, in particular, ensure better flow of the pumped medium and reduce the back pressure on the pump cover.

[0016] Advantageously, the convex bulge of the pump cover is centered toward the center of the pumping chamber. In this case, it should be understood that, in the top view of the pump cover, the convex bulge of the pump cover is centered toward the center of the pumping chamber. This advantageously ensures a particularly even distribution of the internal pressure across the circumference of the pumping chamber. Local pressure increases, which lead to local expansion or elastic movements of the pump cover in the clamping area, are reduced.

[0017] Preferably, the pumping chamber has a widened portion on the side of the diaphragm clamping area. The widened portion is directly connected to the inlet and outlet openings of the pumping chamber. Furthermore, the widened portion is tangentially connected to the convex bulge. The widened portion advantageously changes the internal pressure distribution in the clamping area such that the prevailing internal pressure in the pumping chamber serves to support the tightness of the diaphragm in the clamping area. This is achieved by the internal pressure reducing the elastic movement of the pump cover in the clamping area. This enables the use of PTFE diaphragms in diaphragm pumps at very high operating pressures.

[0018] In a further development, the widened portion is designed circumferentially and centered on the center of the pumping chamber. In this case, it should be understood that, in the top view of the pump cover, the widened portion is centered on the center of the pumping chamber. This advantageously achieves a particularly uniform pressure distribution across the circumference of the pumping chamber.

[0019] Preferably, the widened portion is designed such that a wall of the conveying chamber in the clamping area of ​​the diaphragm runs at a right angle to the diaphragm in its undeformed state. This right-angled design makes the clamping area thicker and more solid. This results in greater stability at the edge of the clamping area compared to a wall that tapers at an acute angle to the diaphragm.

[0020] Advantageously, the widened portion is arranged relative to an inlet and / or outlet channel of the pump cover such that an incoming and / or outgoing pumped medium flows at least partially at right angles toward or away from the diaphragm. The term "partially at right angles" is understood here to mean that a portion of the pumped medium flows at right angles toward or away from the diaphragm. This achieves improved pressure distribution at the edges of the clamping area in the pumping chamber, preventing local gap formation and thus infiltration of the pumped medium. This improves the tightness of the diaphragm in the clamping area.

[0021] Preferably, the delivery chamber in the clamping area of ​​the diaphragm has a diameter that corresponds to the diameter of the hydraulic chamber in the clamping area of ​​the diaphragm. This advantageously achieves uniform clamping of the diaphragm on both sides. Due to the identical diameters in the hydraulic chamber and the delivery chamber, the deflected area of ​​the diaphragm is the same in both directions, thereby preventing excessive deformation of the diaphragm in either direction. Furthermore, the formation of a gap between the diaphragm and the pump cover or housing is prevented, thus preventing infiltration of the conveying or hydraulic medium and the associated expansion.

[0022] The diaphragm is expediently made of a material that includes at least one metal and / or one plastic, in particular polytetrafluoroethylene (PTFE). If the diaphragm is made of a metallic material, higher pressures can be achieved with the diaphragm pump. However, if the diaphragm is made of a plastic material, the diameter of the hydraulic chamber can be smaller due to the greater deformability of the plastic material, which also reduces the external dimensions of the diaphragm pump.

[0023] The invention is explained in more detail below using an exemplary embodiment illustrated in the drawings. The drawings show schematically:

[0024] Fig. 1 is a three-dimensional view of a pump head of a diaphragm pump according to the invention;

[0025] Fig. 2 is a front view of the pump head of Fig. 1;

[0026] Fig. 3 is a cross-sectional view of the pump head of Fig. 2 along the section plane AA;

[0027] Fig. 4 is a front view of a pump cover;

[0028] Fig. 5 is a cross-sectional view of the pump cover of Fig. 4 along the section plane BB;

[0029] Fig. 6 is a rear view of the pump cover shown in Fig. 4; and

[0030] Fig. 7 is a spatial cross-sectional view of the pump cover from Fig. 6.

[0031] Fig. 1 shows a perspective view of an embodiment of a pump head 1 of a diaphragm pump according to the invention. The pump head 1 comprises a pump housing 2 and a pump cover 3 attached to the pump housing 2. The pump cover 3 has an inlet 4 and an outlet 5 for conveying a pumped medium.

[0032] Fig. 2 shows a front view of the pump head 1 with a top view of the pump cover 3. Indicated therein is a sectional plane AA through the center of the pump head 1 and the inlet and outlet 4, 5. The corresponding cross-sectional view of the pump head 1 along the sectional plane AA is shown in Fig. 3.

[0033] As can be seen in particular from the sectional view in Fig. 3, the pump housing 2 has a hydraulic chamber 6 which, in the operating state, is filled with a working medium, such as a suitable hydraulic fluid. The pump cover 3 has a delivery chamber 7 in which, in the operating state, the pumped medium is delivered from the inlet 4 to the outlet 5. The pump head 1 further has a diaphragm 8 which separates the hydraulic chamber 6 from the delivery chamber 7. The diaphragm 8 is positioned on the pump cover 3 with a pin 9 and fastened with fastening means 19 such that the diaphragm 8 is clamped between the pump housing 2 and the pump cover 3 in a clamping area 10. This will be explained in more detail later.

[0034] The diaphragm 8 is designed so that it can be deflected back and forth into the delivery chamber 7 and into the hydraulic chamber 6. In order to push the pumped medium out of the delivery chamber 7, the diaphragm 8 is pressurized by the working medium, so that the diaphragm 8 is deflected into the delivery chamber 7 and the pressure on the pumped medium pumps the medium through the outlet 5. The working medium is pressurized by a piston 11, which is mounted in the pump housing 2 so that it can move linearly and transversely to the diaphragm 8. If the piston 11 is moved towards the diaphragm 8, the working medium is pressurized, so that the diaphragm 8 is deflected into the delivery chamber 7. If the piston 11 is moved away from the diaphragm 8, the working medium is sucked in by the piston 11, so that the diaphragm 8 is deflected into the hydraulic chamber 6.Due to the oscillating deflections of the membrane 8, the conveying medium is sucked into the conveying chamber 7 and pushed out of the conveying chamber 7 again in the next working step.

[0035] The pump cover 3 is described in more detail below. Fig. 4 shows a top view of the pump cover 3. Fig. 5 shows a cross-sectional view along the section plane BB, which runs through the center of the pump cover 3, as can be seen in Fig. 4. For a better understanding of the design of the pump cover 3, it is shown in Fig. 5 without the membrane 8.

[0036] As can be seen from Fig. 5, the pump cover 3 has a convex bulge 12 in the area of ​​the center of the delivery chamber 7. The bulge 12 is circular in plan view, as can be seen better in Fig. 7. It extends into the delivery chamber 7 and is centered towards the center of the delivery chamber 7, so that the distance between the bulge 12 and the diaphragm 8 is smallest in the center of the pump cover 3 in the undeformed state. The bulge 12 of the pump cover 3 increases the flexural rigidity of the pump cover 3. This is because the oscillating deflection movements of the diaphragm 8 also result in pressure fluctuations in the delivery chamber, which lead to oscillating elastic movements of the pump cover 3. The increased flexural rigidity of the pump cover 3 compared to conventional pumps leads to better overall tightness and enables the use of PTFE as a material for the diaphragm at significantly higher operating pressures.

[0037] The inlet 4 has an inlet channel 13 and the outlet 5 has an outlet channel 14 in the pump cover 3. The inlet and outlet channels 13, 14 each open into the pumping chamber 7. The radius R of the bulge 12 is selected such that the bulge 12 merges tangentially into the inlet and outlet channels 13, 14. This improves the flow behavior of the pumped medium in the inlet and outlet directions. Compared to a variant in which the pumping chamber 7 has a flat surface that is parallel to the diaphragm 8, the bulge 12 and the tangential transition result in a better internal pressure distribution on the pump cover 3, since the pumped medium can flow out of the pumping chamber 7 more easily at the edges of the bulge 12.

[0038] As can further be seen from Fig. 5, the delivery chamber 7 has a widening 15 on the side of the clamping area 10 of the diaphragm 8, so that the distance between the bulge 12 and the clamping area 10 increases towards the diaphragm 8. The widening 15 is designed circumferentially between the bulge 12 and the clamping area 10 and is centered towards the middle of the delivery chamber 7, as can be seen from Fig. 7. This advantageously achieves the most uniform internal pressure distribution possible in the circumferential direction. The widening 15 has the effect that the incoming or outgoing pumped medium increases the internal pressure on the clamping area 10. This reduces the widening of the clamping area 10 and the formation of a gap between the diaphragm 8 and the clamping area 10 in the pump cover 3.Due to the higher internal pressure on the clamping area 10, elastic movements of the clamping area 10 are also reduced, which contributes to increasing the tightness but also the operating pressure of the pump.

[0039] In Fig. 5, it can be seen that the widened portion 15 is designed such that a wall 16 of the conveying chamber 7 in the clamping region 10 of the diaphragm 8 runs perpendicular to the diaphragm 8 in the undeformed state. The wall 16 is formed circumferentially around the clamping region 10. The clamping region 10 further has a circumferential angled surface 17, which lies opposite the bulge 12 and, together with the bulge 12, forms the widened portion 15.

[0040] The wall 16 and the surface 17 form an obtuse angle a. The angle a is selected such that at least a portion of the pumped medium flowing through the inlet channel 13 into the pumping chamber 7 is deflected by the angle a and flows at a right angle directly onto the diaphragm 8. Analogous to the inlet 4, the widened portion 15 at the outlet 5 is arranged relative to the outlet channel 14 such that outflowing pumped medium flows at least partially at a right angle away from the diaphragm 8. Due to the wall 16 projecting perpendicular to the diaphragm 8, the clamping area on the side of the pump cover 3 is designed to be more rigid, so that the elastic movements of the clamping area 10 and widenings between the diaphragm and the clamping area 10 are advantageously reduced.

[0041] As can be seen in Fig. 5, the delivery chamber 7 in the clamping area 10 of the diaphragm 8 has a diameter D1, which is formed by the circumferential wall 16. The hydraulic chamber 6 in the pump housing 2 also has a diameter D2 in the clamping area 10 of the diaphragm 8, as can be seen in Fig. 3. For a balanced pressure distribution in the clamping area between the pump cover 3 and the pump housing 2 and for an equal deformed area of ​​the diaphragm 8 both in the delivery chamber 7 and in the hydraulic chamber 6, the diameter D1 corresponds to the diameter D2. Further advantages arise from the fact that the clamping area 10 is loaded equally on both sides.

[0042] Fig. 6 shows a spatial rear view of the pump cover 3, i.e. the side that rests against the pump housing 2, and Fig. 7 shows a spatial cross-sectional view of the pump cover 3, which is cut through the inlet and outlet 4, 5.

[0043] In order to better hold the diaphragm 8 under pressure in the clamping area 10 of the pump cover 3 and the pump housing 2, a comb profile 18 is provided on the clamping area 10 of the pump cover 3 and the pump housing 2. The diaphragm 8 is clamped by fastening the pump cover 3 to the pump housing 2 and is positively pressed with the comb profile 18 to prevent the diaphragm 8 from slipping in the clamping area 10 and to prevent the pumped and working medium from penetrating and infiltrating into the clamping area 10.

[0044] In this case, the diaphragm 8 is made of polytetrafluoroethylene (PTFE). However, it can alternatively or additionally be made of a metallic material to achieve even higher operating pressures in the diaphragm pump. Furthermore, the diaphragm 8 is designed as a two-layer diaphragm to increase the leak resistance and operational reliability of the diaphragm pump.

[0045] REFERENCE SYMBOL

[0046] 1 Pump head Pump housing Pump cover Inlet Outlet Hydraulic chamber Delivery chamber

[0047] 8 Membran

[0048] 9 pin

[0049] 10 Clamping area

[0050] 11 pistons

[0051] 12 bulge

[0052] 13 Inlet channel

[0053] 14 Exhaust channel

[0054] 15 Widening

[0055] 16 Wall

[0056] 17 angled surface

[0057] 18 Kammprofile

[0058] 19 Fasteners a Angle

[0059] D1 diameter

[0060] D2 diameter

[0061] R radius

Claims

PATENT CLAIMS 1 . Diaphragm pump with a pump housing (2) which has a hydraulic chamber (6), and a pump cover (3) which has a delivery chamber (7), wherein a diaphragm (8) is clamped between the pump housing (2) and the pump cover (3) in a clamping area (10) such that the hydraulic chamber (6) and the delivery chamber (7) are separated from one another, characterized in that the pump cover (3) has, in the area of ​​the middle of the delivery chamber (7), an at least partially convex bulge (12) into the delivery chamber (7).

2. Diaphragm pump according to claim 1, characterized in that the convex bulge (12) of the pump cover (3) is at least partially spherical.

3. Diaphragm pump according to claim 1 or 2, characterized in that the convex bulge (12) of the pump cover (3) is centered towards the center of the pumping chamber (7).

4. Diaphragm pump according to one of the preceding claims, characterized in that the delivery chamber (7) has an expansion (15) on the side of the clamping area (10) of the diaphragm (8).

5. Diaphragm pump according to claim 4, characterized in that the widening (15) is circumferential and centered towards the center of the conveying chamber (7).

6. Diaphragm pump according to claim 4 or 5, characterized in that the widening (15) is designed such that a wall (16) of the conveying chamber (7) in the clamping area (10) of the diaphragm (8) runs at right angles to the diaphragm (8) in the undeformed state.

7. Diaphragm pump according to one of claims 4 to 6, characterized in that the widened portion (15) is arranged relative to an inlet and / or outlet channel (13, 14) of the pump cover (3) in such a way that inflowing and / or outflowing conveying medium flows at least partially at right angles to or away from the diaphragm (8).

8. Diaphragm pump according to one of claims 4 to 7, characterized in that the delivery chamber (7) in the clamping area (10) of the diaphragm (8) has a diameter (D1) which corresponds to the diameter (D2) of the hydraulic chamber (6) in the clamping area (10) of the diaphragm (8).

9. Diaphragm pump according to one of the preceding claims, characterized in that the diaphragm (8) consists of a material which comprises at least one metal and / or one plastic, in particular a polytetrafluoroethylene (PTFE).

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