DE29505354U1 - Diaphragm piston pump - Google Patents

Description

Diaphragm piston pump

The subject of the invention is a diaphragm piston pump according to the preamble of claim 1.

Diaphragm pumps are used to pump mechanically abrasive and chemically aggressive media (e.g. suspensions and acids). In these pumps, a displacement effect is generated by the movement of a diaphragm clamped into a housing. The diaphragm material can be adapted to the pumped medium.

The membrane can have a hydraulic, pneumatic or mechanical drive. In the case of a hydraulic

Patent Attorneys · Burorjaan Batest Attorney-at-Law, European Patent Attorney Representative at the European Patent Office

,•liecJpsMMvaft: zj^las _t sen tiei the Wanibur^er courts

Deutsche Bank AG Hamburg, No. 28 42 206 (bank code 200 500 20)
Dresdner Bank AG Hamburg, No. 933 60 35 (bank code 200 800 00)

In a diaphragm pump, the displacement effect of a piston is transferred to one side of the diaphragm using an auxiliary fluid (water, oil). These hydraulic diaphragm piston pumps have a relatively good level of efficiency. Their diaphragm is designed as a disc or flat diaphragm or as a spherical diaphragm in the form of a cylindrical tube. The diaphragm movement is linked to an inward or outward curvature and is limited by the elastic stretchability of the diaphragm. The throughput requirements for hydraulic diaphragm piston pumps must be met by appropriate dimensioning of the diaphragm. Spherical diaphragms enable smaller sizes. Nevertheless, a further reduction in pump sizes seems desirable.

Rigid support devices can be provided for a defined vibration path of the membranes. With flat membranes, a dome-shaped support surface can be arranged at least on the drive side. On the other side of the membrane, a support surface is only possible with suitable conveying media due to the required permeability. With the spherical membrane, the support device has the form of a curved support cylinder. These support devices increase the design effort, are only partially functional and can place additional stress on the membrane. This applies in particular if the auxiliary fluid

quantity on the drive side of the pump fluctuates.

To compensate for leaks and to maintain a certain amount of auxiliary fluid, diaphragm piston pumps have compensation systems that connect the hydraulic system to an equalization tank. On the hydraulic side of the diaphragm there is a button that detects the diaphragm movement during the piston's suction stroke and controls a compensation valve to the equalization tank. Excess fluid can be drained into the storage tank via a throttle device during the piston's pressure stroke. This automatic system is also known as "diaphragm system control". The piston drive and the diaphragm position control are particularly sensitive and can easily be damaged by the pumped medium penetrating the diaphragm if the diaphragm is destroyed. These systems are therefore often equipped with monitoring devices that monitor the condition of the diaphragm or the auxiliary fluid.

In pneumatically driven diaphragm pumps, the displacement effect of the diaphragm is generated by compressed air. They can have a compressed air-driven piston that acts on the diaphragm via a piston rod. This can be a pre-formed diaphragm that can move back and forth without stretching in relation to its clamping plane.

This diaphragm has a relatively large displacement volume, which means that the pump can be constructed in a small volume. However, the displacement volume is reduced by the rigid action of the piston rod. In addition, the piston rod action can impair the strength of the preformed diaphragm, the material of which is already subject to particular stresses due to the constant action of being pulled in opposite directions. In addition, the efficiency of pneumatically driven diaphragm pumps is relatively low.

However, diaphragm pumps with a preformed diaphragm and mechanical drive have also become known. These pumps have a high level of efficiency. However, as a result of the mechanical attack on the diaphragm, the displacement volume and the strength of the diaphragm are impaired. In addition, the complex mechanical drive is particularly susceptible to wear, so that destruction of the diaphragm can have significant cost consequences.

Membrane pumps are usually designed as double-acting or, for smaller flow rates, as single-acting diaphragm pumps. In double-acting pumps, the two diaphragms alternately perform a suction stroke and a

Pressure stroke, whereby a uniform flow rate is achieved in the common pressure line. To further even out the flow rate, an equalizing vessel can be arranged on the pressure line. The equalizing vessel also has a clamped membrane that separates a primary chamber pre-pressurized with a gas from a secondary chamber filled with the material to be conveyed. The low mobility of disc membranes is also a disadvantage in equalizing vessels. The usability of pre-formed membranes is impaired by their easy destructibility.

Based on this, the invention is based on the object of creating a diaphragm piston pump with a relatively high level of efficiency and low construction costs as well as high operational reliability. Furthermore, a pump with a smaller volume expansion tank and greater operational reliability is to be created.

The basic problem is solved by claim 1, the further problem by claim 2. Advantageous embodiments are contained in the subclaims.

According to the invention, a hydraulic diaphragm piston pump is combined for the first time with a preformed diaphragm. The

The membrane can be driven by the auxiliary fluid at its freely movable preforming, which is arranged within the edge-side clamping. The hydraulic drive ensures a high level of efficiency. The preforming of the membrane ensures considerable deformability and a large displacement volume. Compared to the previously known applications of preformed membranes, the displacement volume is increased even further because the rigid attack of a mechanical system is eliminated. In addition, the uniform loading of the membrane with auxiliary fluid can have a positive effect on its stress and service life. This means that the advantages of the hydraulic drive, in particular its relatively high efficiency with a relatively simple and reliable design, are combined for the first time with the advantages of a preformed membrane, in particular a large displacement volume and thus a small design. A corresponding membrane is preferably used in an expansion tank, which is connected to the pump outlet to even out the flow rate. This allows small expansion tank sizes to be achieved with sufficient operational safety. This in turn has a positive effect on the design of a unit that combines a diaphragm piston pump and an expansion tank.

The preforming of the membrane preferably has a dome

or a double S. On the outer edge of the dome or the double S, the preform can have a connection area to a flat edge for clamping the membrane. The connection area is curved in the opposite direction to the dome or the double S and preferably has a much smaller radius of curvature than the dome.

The preformed membrane is preferably designed with a special fabric layer so that it can withstand the stresses for a long time. The fabric layer prevents the preformed membrane from being destroyed as a result of high flexing work, the separation between the primary chamber and the secondary chamber being eliminated and product from entering the hydraulic area of the pump over a considerable period of operation. The fabric layer can also ensure that the membrane reaches defined end positions and does not tear in these despite considerable stresses. To reduce the stresses and to reach defined end positions, the membrane can be deformed without stretching. The fabric layer is preferably dimensioned in such a way that it limits the movement of the membrane to a range between two end positions at the pressures that occur in the primary and secondary chambers during operation. The fabric membrane then does not require any support devices, which are complex, have only limited functionality and impair functionality. The membrane

However, the membrane can also be deformed in such a way that it does not reach any end positions. The material stress is then lower and the membrane's service life is longer. In this operating mode in particular, the use of a membrane without a fabric layer is considered.

An impermeable membrane layer can be arranged on both sides of a fabric layer so that the fabric layer is protected and the membrane is smooth on the outside. Its material can be selected according to the strength and flexibility requirements. For example, it can be a fabric layer made of polyester or polyamide. At least one further membrane layer can consist of an elastomer, in particular a natural or synthetic rubber (neoprene, Perbunan, etc.). In general, soft-elastic plastics are considered for the further membrane layer, e.g. the particularly resistant materials Viton or Teflon.

To protect the diaphragm from excessive differential pressures between the primary chamber and secondary chamber, these can be connected to a safety valve and devices for determining the differential pressure can cause the safety valve to open if the permissible differential pressure is exceeded. This reduces the risk of diaphragm damage.

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Damage is reduced even further. Additional diaphragm monitoring in the conventional manner is generally not necessary due to the considerable operational reliability of the diaphragm piston pump.

The diaphragm piston pump according to the invention is also suitable for adjusting the amount of auxiliary fluid by controlling the diaphragm position. For this purpose, the primary chamber can be connected to a reservoir containing auxiliary fluid via a valve device and a throttle device, a button can be arranged in the primary chamber, which the diaphragm actuates on the way to its end position during the piston's suction stroke, with a control device opening the valve device when the button is actuated and there is a fluid deficit in the primary chamber.

Further details and advantages of the invention emerge from the following description of the associated drawings of a preferred embodiment. In the drawings:

Fig. 1 a double diaphragm piston pump in section;
Fig. 2 Diaphragm of the same pump in plan view;
Fig. 3 the same membrane in an enlarged section;

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Fig. 4 another membrane for use in the same pump in plan view;

Fig. 5 the same membrane in an enlarged section; Fig. 6 expansion vessel for the pump of Fig. 1 in section; Fig. 7 the same expansion vessel in plan view.

The double diaphragm piston pump according to Fig. 1 has a piston 1 in a cylinder 2. The piston 1 is doubly effective, so that piston working chambers 3, 4 are arranged on both sides. The piston 1 is connected via a piston rod 5 to a piston drive 6, which moves the piston 1 back and forth in the cylinder 2.

The pump has a symmetrical housing 7 in which primary chambers 8, 9 are arranged. The primary chamber 8 is connected to the piston working chamber 3 and the primary chamber 9 to the piston working chamber 4. Both primary chambers 8, 9 are delimited by a membrane 10, 11 clamped into the edge of the housing 7. The structure of the membranes 10, 11 is explained below.

The primary chambers 8, 9 and the piston working chambers 3, 4

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and the connections between them are filled with an auxiliary liquid, for example water.

The membranes 10, 11 also delimit a secondary chamber 12, 13 in the housing 7 for a medium to be conveyed. The secondary chambers 12, 13 are designed as flow channels, with the membranes 10, 11 forming a side wall section. A ball check valve 14, 15, 16, 17 is formed at the two ends of each secondary chamber 12, 13. All ball check valves open by moving the ball upwards in the conveying direction F.

The ball check valves 14, 16 are fed from a common suction line 18 and the ball check valves 15, 17 open into a common pressure line 19.

The primary chambers 8, 9 each have a membrane position control. These are each provided in a known design with a button 20, 21 that is spring-loaded in the direction of the membrane 10, 11. Each button 20, 21 is assigned a valve device 22, 23. If a button 20, 21 is pressed against its spring preload, it in turn pushes a valve plate 24, 25 of the associated valve device 22, 23 upwards. In addition,

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A spring-loaded ball 26, 27 is provided between each valve plate 24, 25 and an upper opening of the valve device 22, 23. At the top, each valve device 22, 23 opens into a reservoir 28 with auxiliary fluid.

Finally, each primary chamber 8, 9 is connected to the storage tank 28 via a throttle plug 29, 30.

This double-acting diaphragm piston pump works as follows:

The piston working chambers 3, 4 are alternately reduced or enlarged by the back and forth movement of the piston 1. The auxiliary fluid is pressed from the decreasing piston working chamber 3, 4 into the connected primary chamber 8, 9 and sucked from the other primary chamber 9, 8 into the increasing piston working chamber 4, 3. This creates an overpressure in one primary chamber 8, 9, which bulges the associated membrane 10, 11, and a negative pressure in the other primary chamber 9, 8, which bulges the associated membrane 11, 10 inwards. According to Fig. 1, the piston working chamber 4 has its minimum volume and the membrane 11 is maximally bulged. At the same time, the piston working chamber 3 has its maximum volume and the membrane 10 is maximally bulged.

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Driven by the piston 1, the membranes 10, 11 are thus curved inwards and outwards in constant alternation in opposite directions. The curvature of a membrane 10, 11 in the adjacent secondary chamber 12, 13 causes a negative pressure, which causes the ball check valve 15, 16 on the suction side to open and the conveying medium to be sucked in through the suction line 18. A curvature of a membrane 11, 10, on the other hand, causes the ball check valve 16, 14 to close and the ball check valve 17, 16 to open at the same time, expelling conveying medium into the pressure line 19. According to Fig. 1, conveying medium is sucked from the suction line 18 into the secondary chamber 12 and expelled from the secondary chamber 13 into the pressure line 19. In constant alternation, the secondary chambers 12, 13 suck in conveying medium from the suction line 18 and expel it into the pressure line 19. This achieves a relatively uniform conveying flow.

The diaphragm system control is intended to ensure a constant amount of auxiliary fluid in the drive system. If a diaphragm 10, 11 is curved inwards as a result of a suction stroke of the piston 1 in relation to the associated piston working chamber 3, 4, it comes into contact with the button 20, 21 before the piston reaches its rear dead center. The piston 1 continues its movement until it reaches its rear dead center.

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dead point. If there is a fluid deficit, a negative pressure is created in the primary chamber 8, 9. The membrane 10, 11 pushes the valve plate 24, 25 up via the button 20, 21 and the pressure difference between the storage tank 28 and primary chamber pushes the check ball 26, 27 downwards. Hydraulic fluid can then flow from the storage tank 28 through the valve device 22, 23 into the primary chamber 8, 9 and compensate for the fluid deficit.

During a pressure stroke of the piston 1 in relation to the piston working chamber 4, 3 in question, hydraulic fluid is fed into the supply tank 28 through the throttle 30, 29 of the connected primary chamber 9, 8. At the same time, the valve plate 25, 24 is raised as a result of the fluid pressure in the primary chamber 9, 8. However, the check ball 27, 26 is closed so that no hydraulic fluid flows back from the supply tank 28 into the primary chamber 9, 8.

Thus, with each suction or pressure stroke, missing hydraulic fluid is replenished from the storage tank 28 or excess hydraulic fluid is returned to it.

According to Fig. 2 and 3, the preformed membranes 10, 11

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each have an edge region 31 in the form of a flat disk, which is provided with holes 32 for flange fastening. The edge region 31 merges into a curved connecting region 33 on the inside, to which an oppositely curved dome 34 is connected.

The membrane 10, 11 has a three-layer structure. It has an inner layer 35 and an outer layer 36, each made of neoprene, and a fabric layer 37 made of polyester in between. The multi-layer structure is vulcanized in a mold in the shape shown and is thus preformed.

When the pump is in operation, the pre-forming of the membrane 10, 11 made up of the connecting section 33 and the cap 34, as shown in Fig. 2 and 3, is constantly pushed back and forth through the plane of the edge region 31. The composite construction results in a significant increase in strength, particularly in the connecting region 33, which is particularly subject to membrane deformation.

The flat disk-shaped edge region 31 of the membrane 10, 11 has a mean diameter of 295 mm and an outer diameter of 330 mm in the exemplary embodiment. The radius of curvature of the connecting region is 12.7 mm

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compared to a radius of curvature of the cap of 128 mm. The ratio of these radii is therefore about 1:10. In the example, the cap has an inner diameter of 235 mm. This inner diameter and the radius of curvature are decisive for the displacement volume. A flat membrane with a corresponding displacement volume would have a diameter of about 425 mm and would result in a considerably larger pump.

Fig. 4 and 5 show another preformed membrane which can be used in the same double membrane piston pump instead of the one described above and is therefore identified by the reference numbers 10', 11'. This membrane also has an edge region 31' in the form of a flat disk, which is provided with holes 32 ' for flange fastening. The edge region 31' merges internally into a curved connecting region 33', which, however, has a considerably larger radius of curvature than the membrane of Fig. 2 and 3. Between the connecting regions 33', the membrane 10', II ⁷ has a central region 34' which - in diagonal sections according to Fig. 5 - has a double S shape. The central region 34' has a central curved region 34" and an outer curved region 34''' which surrounds it and is curved in the opposite direction and smoothly merges into the connecting region 33'. The curved region

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The connection radii of the areas 34'', 34'" correspond to that of the connection area 33'.

The membrane 10', 11' also has a three-layer structure. It has an inner layer 35' and an outer layer 36' and a fabric layer 37' in between. Materials that combine enormous strength with low stretch are particularly suitable for the fabric layers of the membranes. The multi-layer structure is vulcanized in a mold in the shape shown and is thus preformed.

When operating in a pump according to Fig. 1, the pre-forming of the membrane 10', 11', which can be seen in Figs. 4 and 5, consisting of the connecting section 33' and the central section 34', is constantly moved back and forth with respect to the edge region 31'. When the membrane moves forward (upwards in Fig. 5), essentially only the central curved region 24'' is curved upwards against its curvature. When it moves forward (downwards in Fig. 5), essentially the central curved region 34'' is curved in the opposite direction and the outer curved region 34''' is curved downwards against its curvature. The stress on the membrane can only be reduced by deformation in part of its large deformation region. In addition,

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the stress due to the double-S preforming is more evenly distributed across the membrane than with the dome shape. The connecting area 33' in particular is subject to less stress because it has a significantly reduced curvature. The increase in strength due to the composite construction is very well utilized by the double-S preforming. The considerable deformability of this double-S membrane with reduced stress makes it advisable to design it in a single layer, in contrast to Fig. 4 and 5.

The flat disk-shaped edge region 31' of the membrane 10', 11' has a mean diameter of 295 mm and an outer diameter of 327 mm in the embodiment. The radius of curvature of the connecting region is 48 mm. The same radius of curvature is present in the central region 34'' and in the edge region 34'''. In the example, the flat disk-shaped edge region 31 ' has an inner diameter of 250 mm. The diameter of the outer curved region 34''' - measured between the points of its maximum bulge - is 142.5 mm. The central curved region 34'' protrudes (downwards) by approximately 15 mm over the underside of the edge region 31' and the outer curved region 34'" protrudes by approximately 21.5 mm in the opposite direction over the underside. The displacement

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The displacement volume is defined by the dimensions of the central region 34 ' and is considerably larger than the displacement volume of a flat membrane with the same diameter.

Fig. 6 and 7 show the use of the membrane 10, 11 according to Fig. 2 and 3 in an expansion tank 38. This has a housing 39 in which the membrane 10, 11 separates a primary chamber 40 from a secondary chamber 41.

Two pressure pipes 42, 43 open into the secondary chamber 41 and can be connected to the outlets of the ball check valves 15, 17 of the pump in Fig. 1. The outlets of the two pumps in Fig. 1 are thus brought together in the primary chamber 40. The common pressure line 19 is led out of the housing 39 at the side.

The primary chamber 40 is closed by a dome-like cover 44, which has a connection piece 45 for compressed air. A constant compressed air source is connected there, the pressure of which exceeds the delivery pressure of the pump.

Pressure fluctuations at the pump outlet are communicated to the compressed air reservoir 41 via the diaphragm 10, 11 and

dampened. Due to the pre-formed membrane, the expansion vessel requires a relatively small primary volume 40. The fabric insert of the membrane 10, 11 promotes a high level of wear resistance.

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Summary Diaphragm piston pump

Diaphragm piston pump, single or double acting in one, two or three cylinder design with a movable diaphragm clamped at the edge in a housing that separates a primary chamber from a secondary chamber, a piston in a cylinder, a piston drive for a back and forth movement of the piston in the cylinder while changing a piston working chamber, whereby the primary chamber and the piston working chamber are connected and filled with an auxiliary fluid, a suction valve between the secondary chamber and a suction line and a pressure valve between the secondary chamber and a pressure line, whereby the diaphragm has a freely movable pre-forming that can be actuated by the auxiliary fluid.

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Claims (12)

- 21 claims 1. Diaphragm piston pump, single or double acting in one, two or three cylinder design with a movable diaphragm (10, 11) clamped in the edge of a housing (7) which separates a primary chamber (8, 9) from a secondary chamber (12, 13), a piston (1) in a cylinder (2), a piston drive (6) for a back and forth movement of the piston in the cylinder while changing a piston working chamber (3, 4), whereby the primary chamber (8, 9) and the piston working chamber (3, 4) have a connection and are filled with an auxiliary liquid, a suction valve (14, 16) between the secondary chamber (12, 13) and a suction line (18) and a pressure valve (15, 17) between the secondary chamber (12, 13) and a pressure line (19), characterized in that the diaphragm (10, 11) has a freely movable, Auxiliary fluid-operated preforming (33, 34). 2. Pump, in particular according to claim 1, in which a compensation vessel (38) with a movable membrane (10, 11) clamped at the edge in a housing (39) is provided, which separates a compensation primary chamber (40) from a compensation secondary chamber (41), which .../22 The primary compensation chamber (40) is filled with a prestressed medium and the secondary compensation chamber (40) is connected to the pressure line (19), characterized in that the membrane (10, 11) has a freely movable preform (33, 34) acted upon by the prestressed medium. 3. Pump according to claim 1 or 2, characterized in that the preforming has a dome (34) or a double S-shape. 4. Pump according to claim 3, characterized in that the preforming on the outer edge of the dome (34) or double S-shape has a connecting region (33) curved in the opposite direction to this to a flat edge region (31) of the membrane. 5. Pump according to one of claims 1 to 4, characterized in that the membrane (10, 11) is designed in multiple layers with a fabric layer (37). 6. Pump according to one of claims 1 to 5, characterized in that the membrane (10, 11) is movable without stretching. .../23 7. Pump according to one of claims 5 to 6, characterized in that the fabric layer (37) limits the movement of the membrane (10, 11) at the operating pressures in the primary and secondary chambers (8, 9; 12, 13) to a range between two end positions due to its dimensioning. 8. Pump according to one of claims 5 to 7, characterized in that an impermeable membrane layer (35, 36) is arranged on both sides of the fabric layer (37). 9. Pump according to one of claims 5 to 8, characterized in that the fabric layer (37) is made of polyester or polyamide. 10. Pump according to one of claims 1 to 9, characterized in that at least one further membrane layer (35, 36) is made of an elastomer, in particular a synthetic or natural rubber. 11. Pump according to one of claims 1 to 10, characterized in that the primary chamber (8, 9) or secondary chamber (12, 13) is connected to a safety valve and devices for determining the differential .../24 - 24 - pressure of the primary chamber and secondary chamber and opening of the safety valve when a permissible differential pressure is exceeded, 12. Pump according to one of claims 1 to 11, characterized in that the primary chamber (8, 9) is connected to a reservoir (28) with auxiliary fluid via a valve device (22, 23), a button (20, 21) is arranged in the primary chamber (8, 9), the membrane (10, 11) actuating the button (20, 21) during the suction stroke of the piston (1) on the way to its end position and a control device (24, 26) opening the valve device (20, 23) when the button is actuated and there is a fluid deficit in the primary chamber (8, 9). .../25 ·