Patent Application
20130101445
The present invention relates to a diaphragm pump having at least one diaphragm.
In diaphragm pumps, the diaphragm delimits a conveying space in which a supply line and a discharge line open. Generally, non-return valves are arranged in the supply and discharge lines in such a manner that, by the diaphragm being moved back and forth, the conveying medium can first be drawn via the supply line into the conveying space and can subsequently be pressed out of the conveying space via the discharge line.
So that a continuous conveying action is possible, in most cases two diaphragm pumps are connected in parallel, the first one drawing in the conveying medium and the other at the same time pressing the conveying medium out of the conveying space thereof.
There are further known dual-diaphragm pumps, in which the diaphragms, which in most cases are constructed as plate diaphragms, are adjusted by means of a common piston/cylinder system or by means of an electrical drive. In spaces in which explosive gases may occur, no electrical pumps must be operated or the strict provisions of Explosion Protection must be taken into consideration. In this instance, pneumatic pumps are generally used, in which a piston, which is mechanically connected to the diaphragms, is moved back and forth in a cylinder by means of compressed air. The compressed air in this instance is switched by means of a main valve in such a manner that the two operating spaces are alternately filled with compressed air. Such a pump is known from U.S. Pat. No. 4,818,191. The spaces which are separated from the conveying space by the diaphragms are connected to the environment by means of channels so that, in the event of a leakage, the conveying medium can be discharged from the pump and does not impede the movement of the diaphragms. The disadvantage of this pump is that the diaphragms, owing to the high pressure in the conveying space and the ambient pressure behind the diaphragm, are subjected to a high differential pressure load, which leads to rapid wear in the diaphragms.
A further developed pneumatically driven dual-diaphragm pump is known from WO 2009/024619. In this pump, the compressed air which drives the piston is directed at the same time into the space behind the diaphragm. At the same time, the diaphragm is supported by means of a plate but the plate completely abuts the diaphragm in a supporting manner only at a dead centre point. The disadvantage of this pump is that, in the event of a defect of the diaphragm, the conveying medium reaches the pneumatic system and disables the valves and consequently the entire pump. The pump can subsequently be restarted, if at all, only with great complexity.
A dual-chamber diaphragm pump without a driven piston is known from DE 32 06 242. The disadvantage of this pump involves the large spaces which must be filled with compressed air after the dead centre point has been reached so that the diaphragms can be moved in the other direction. A very large amount of compressed air is thereby required, which increases the maintenance costs of the pump. A similarly constructed pump with the same disadvantages is known from CA 1172904, WO97/10902 and U.S. Pat. No. 5,368,452. With the pump known from WO2009/024619, a disproportionately large amount of compressed air is required for the operation of the pump. These pumps are also not pressure-boosted so that the conveying pressure is always below the feed pressure.
An object of the present invention is to provide a diaphragm pump in which the diaphragms have a long service-life and are subjected to low differential pressures and which has a good level of efficiency.
This object is achieved according to the invention with a diaphragm pump wherein a fluid moves at least a first piston of a first piston/cylinder system back and forth, the first piston being mechanically connected to at least one other hydraulic piston and the hydraulic piston driving at least one diaphragm (M1, M2) by means of a hydraulic medium, characterised in that the diaphragm pump is a dual-diaphragm pump having at least two diaphragms (M1, M2), a hydraulic medium moving or driving the diaphragms (M1, M2), at least one hydraulic piston moving the hydraulic medium, and in that two diaphragms (M1, M2) are mechanically connected to each other by means of a connection element, in particular a rod or a pipe, respectively.
The notion of the invention is that the diaphragm pump has a first piston/cylinder system whose piston drives at least one hydraulic cylinder. The piston can be driven in this instance by means of a fluid, for example, compressed air or a fluid medium, that is to say, moved back and forth. The at least one hydraulic piston is also thereby moved back and forth. The hydraulic piston is itself arranged in a cylinder and divides it into two operating spaces, a first and a second operating space. At least the first operating space is filled in this instance with a hydraulic medium which acts on the diaphragm of the diaphragm pump.
Advantageously, the diaphragm pump is constructed as a dual-diaphragm pump so that each of the two diaphragms conveys alternately. Advantageously, the first operating space is delimited at the end face by the hydraulic piston and the diaphragm, respectively. However, it is also possible for the operating space to be connected via a connection line to the space separated from the conveying space by the diaphragm and for the hydraulic medium moved by the hydraulic piston thus to act on the diaphragm and adjust it.
The first piston of the first piston/cylinder system is in this instance advantageously driven by means of compressed air so that the diaphragm pump can also be used in explosion-protected spaces.
Owing to the freely selectable surfaces of the first piston and hydraulic piston, any pressure boost between the driving pneumatic pressure and the conveying pressure of the pump can be adjusted.
Regardless of the conveying pressure of the diaphragm pump, the diaphragms are subjected to a maximum differential pressure load (maximum suction power) of one bar, whereby a long service life of the diaphragms is advantageously obtained.
An inert fluid for the conveyed medium is advantageously selected as a hydraulic medium so that, in the event of a defect of the diaphragm, the conveying medium does not become contaminated. Should conveying medium enter the first operating space in the event of a malfunction, this does not influence the pump.
Advantageously, the second operating spaces of the hydraulically acting piston/cylinder systems are connected to each other so that they act as damping members by the medium which is located in these operating spaces and which is advantageously the same inert hydraulic medium as in the first operating spaces being pumped back and forth.
If the pump is constructed as a dual-diaphragm pump, the diaphragms are advantageously connected to each other by means of a connection element which synchronises the movement of the diaphragms. This connection element does not serve to drive the diaphragms. Advantageously, the connection element has at each of the ends thereof a thread by means of which it is screwed into the diaphragms. The screwing can be carried out directly into the material, in particular rubber, or into a threaded socket which is enclosed in the diaphragm. Since the connection element does not transmit any great forces, it is possible in most cases to dispense with a threaded socket.
A small structural form is advantageously achieved when the driving first piston/cylinder system is arranged between the hydraulically acting piston/cylinder systems. In this instance, the first piston is rigidly connected to the two hydraulic pistons by means of piston rods, whereby they are synchronously adjusted therewith. The connection element of the diaphragms may advantageously extend through the tubular piston rods and is displaceably supported therein. That is to say, the connection element extends through the hydraulic pistons, correspondingly arranged seals preventing hydraulic medium from one operating space reaching the other through the piston rods.
Advantageously, the diaphragm pump has at least one device for monitoring the quantity of the hydraulic medium in one and/or more operating space(s) of the hydraulically acting piston/cylinder systems and/or in the connection line thereof. If hydraulic medium escapes and is drawn from a storage container, this is recognised by the device and the pump is stopped and/or an error signal is transmitted to a superordinate control system.
The fluid which moves the first piston of the first piston/cylinder system back and forth, in particular compressed air, is directed by a main valve, which is controlled in particular by the movement of the first piston, alternately into the first and second operating space of the first piston/cylinder system.
In the walls of the first piston/cylinder system that delimit the operating spaces axially or at the end face, there are arranged switching valves, in particular 3/2 way valves, which are mechanically actuated by the first piston before or when the respective dead centre point or switching point is reached. In this instance, the switching valves control the compressed air which switches the main valve. Advantageously, uncontrolled compressed air is used in this instance, that is to say, compressed air which is provided by an external compressed air source. This pressure is generally higher than the pressure with which the diaphragm pumps according to the prior art are operated. It is thereby ensured that the diaphragm pump according to the invention switches in a reliable manner. This is often not the case with diaphragm pumps according to the prior art in which the main valve has only one inlet for controlled air, since the controlled pressure at the first piston/cylinder system is often very low.
The first piston actuates the valve adjustment members of the switching valves mechanically, the switching valves being constructed in particular as cartridge valves, that is to say, so as to be able to be inserted, in particular screwed, from the outer side into the wall of the first piston/cylinder system that delimits at the end face in each case. A particularly favourable construction is thereby achieved since the valves can be replaced without opening the conveying spaces.
The main valve is also advantageously arranged on the housing of the diaphragm pump at the outer side so that the main valve can also be readily cleaned, repaired or replaced.
The main valve is advantageously constructed as a 4/2 way valve or as a 5/2 way valve. That is to say, the valve control element of the main valve moves alternately back and forth between two end positions. It consequently has only two defined positions in the form of the end positions. On the way from one end position to the other end position, that is to say, during the movement, in a central region between the end positions, the two operating spaces of the first piston/cylinder system are connected to each other by means of the valve control element of the main valve and the receiving operating space is consequently prefilled with the compressed air from the transferring operating space. Afterwards, the operating space which has been prefilled is further filled with controlled air. The other operating space is connected to the valve outlet so that the remaining operating air from the operating space can expand via silencers. A better degree of efficiency of the diaphragm pump according to the invention is thereby achieved since less compressed air is required for the operation of the pump.
Advantageously, the main valve has an inlet for uncontrolled compressed air from an external compressed air source, the main valve itself being able to have a pressure control device for producing controlled compressed air of a specific pressure. By means of a valve control element which is displaceably arranged in the housing of the main valve and which is adjusted by the compressed air which is controlled by the switching valves, in particular the uncontrolled compressed air, the controlled compressed air is directed alternately into the operating spaces of the first piston/cylinder system.
So that the remaining operating space in the dead centre points of the first piston is as small as possible, the axial cylinder walls of the cylinder of the first piston/cylinder system may advantageously be adapted to the shape of the axial walls of the first piston. A planar construction of the walls is preferred in this instance.
The switching valves may advantageously have throttles so that the air which is pressed out of the respective operating space is braked by the throttle and a slowed movement of the valve control element of the main valve from the centre region is thereby achieved, whereby the phase of the pressure compensation between the pretensioned operating space and the operating space which is to be emptied next and the operating space which is to be filled next is as long as possible. The throttle does not yet act so strongly at the beginning of the movement of the pneumatic piston so that the valve control element of the main valve is adjusted with high speed from the end position thereof in the direction of the central region, in which the operating spaces of the pneumatic cylinder are bypassed.
Each conveying space may advantageously be connected by means of a supply channel to a common supply line, respectively, and/or by means of an outlet channel to a common pressure line, respectively, the supply line and/or the pressure line being supported in a floating manner on at least one connection region of the pump housing. It is thereby advantageously possible that no alternately occurring loads occur at the connection locations (appearances of mechanical fatigue). Valves, in particular non-return valves, are arranged in the supply channels and in the outlet channels, respectively.
It is of course possible, using the first piston/cylinder system which is driven in particular pneumatically by means of compressed air, for a plurality of hydraulic pistons which are arranged parallel with respect to each other to be able to be driven. It is thereby possible, using a pneumatic drive, to drive or adjust more than two diaphragms, in particular a multiple of two, for drawing and pressing.
One possible embodiment of the diaphragm pump which is constructed as a dual-diaphragm pump is explained in greater detail below with reference to drawings.
In the cylinder 2, 3 of the first piston/cylinder system, there is arranged the first piston 1 which is formed by two discs 1a, 1b and which separates the operating spaces A and B from each other. The discs 1a, 1b are screwed together by means of the screws 4. The cylindrical wall 2 has, at the outer side thereof, ribs for absorbing heat from the ambient air in order to prevent ice forming on the diaphragm pump. The axial walls 3 also have recesses 3b which also serve to better conduct heat and to provide rigidity and save material. The piston 1 has a continuous seal 1c which abuts the inner wall of the cylinder 2 in a sealing manner.
When the piston 1 is assembled, the piston rods 8a, 8b are pushed beforehand through the holes 1d until the collars 8c rest in the corresponding recesses 1e of the piston discs 1a, 1b. Owing to the assembly of the piston discs 1a, 1b, the piston rods 8a, 8b are secured to the piston 1 in a positive-locking manner.
The piston rods 8a, 8b extend through the holes 3a of the axial walls 3, seals 56 ensuring that no compressed air from the operating spaces A, B reaches the hydraulic spaces H2. With the ends 8d thereof, the piston rods 8a, 8b are connected to the hydraulic pistons in a sealing manner by means of screws 60. The piston rods 8a, 8b are constructed as pipes in which the connection element 5 rests in a displaceable manner in the form of a rod. The connection element 5 is screwed with the ends 5a thereof having the outer thread into the diaphragm plate 20. The diaphragm plate 20 is formed in the diaphragm M1 in the centre 21 thereof.
The hydraulic pistons 9 each have a continuous seal 12 which abuts the inner wall of the cylinder wall 10 in a sealing manner and separates the two operating spaces H1, H2 from each other. The two hydraulic spaces H2 of the two hydraulic piston/cylinder systems are connected to each other by means of the connection channels 16, 17 and 18. Differential pressure valves 13 are arranged in each case in the hydraulic pistons 9. If the differential pressure between the operating spaces H1 and H2 exceeds a specific value when the pump is operated, the differential pressure valve 13 opens and the differential pressure can be reduced to a predetermined value. The connection channel 16, 17, 18 can be connected by means of an additional connection line (not illustrated) to a storage container and/or a sensor. If an influx or discharge of hydraulic medium now occurs at the storage container or the connection line, this may signify a breakage of the diaphragm, whereupon an error signal can be sent to a superordinate control system and/or the diaphragm pump is automatically stopped. This can be carried out, for example, by the forced closing of the line which supplies the pump with compressed air.
The supply channels 28 are connected to each other by means of the supply line 36, the supply line 36 forming with the one end 41 thereof the conveying medium inlet of the pump.
The other end of the supply line 36 which is constructed as a pipe is closed by means of a screwed-in plug 34. The supply line 36 rests with the regions 36a thereof in a floating manner in the housing flanges 27, seals 39 ensuring the necessary sealing. The housing flanges 27 have an annular space 40 which surrounds the regions 36a and which is formed by a continuous groove. In the region 36a, the supply line 36 has window-like openings 38 through which the conveying medium is introduced from the inner space 37 of the supply line 36 into the annular space 40 and from there into the supply channel 28.
The outlet channels 26 are connected to each other by means of the pressure line 29, the pressure line 29 forming the conveying medium outlet of the pump with the one end 33 thereof. The other end of the pressure line 29 which is constructed as a pipe is closed by means of a screwed-in plug 34. The pressure line 29 rests with the regions 29a thereof in a floating manner in the housing flanges 25, seals 39 ensuring the necessary fluid-tightness. The housing flanges 25 have an annular space 32 which surrounds the regions 29a and which is formed by a continuous groove. In the regions 29a, the pressure line 29 has window-like openings 31, through which the conveying medium can be introduced from the annular space 32 into the inner space 30 of the pressure line 29.
In the axial walls 3, there are arranged switching valves 14 which extend with an extension 15 of the valve control members thereof into the operating spaces A, B. If the piston 1 reaches its dead centre point, the respective switching valve is actuated, whereby compressed air is directed to the main valve 50 by means of channels which are not illustrated, and the main valve is in turn switched off.
The main valve 50 is arranged at the outer side on the pump housing so that good heat exchange with the ambient air can take place, whereby the risk of formation of ice is reduced.
In so far as the diaphragm plate 20 is adjusted by means of the hydraulic piston 9 in such a manner that the conveying space F1 is reduced, the conveying medium which is located in the conveying space F1 is conveyed by the non-return valve 24 into the outlet channel 26. The non-return valve 23 is closed during this. If enlargement subsequently occurs in the conveying space F1 by the diaphragm M1 being moved back, conveying medium is drawn from the supply line 36 into the conveying space F1 via the non-return valve 23 which is open. During the suction phase, the non-return valve 24 is closed.
The inlet 43 is connected to the switching valves 14 by means of connection lines 48, 49. The switching valves are constructed as 3/2 way valves and are switched by means of the extensions 15 of their valve control members extending into the operating spaces A, B. A spring presses the valve control members into the illustrated position, in which the control lines 52, 53 are not connected to the valve inlet or the connection line 48, 49. As soon as the piston 1 adjusts the respective valve control member 15, the switching valve 14 is switched and the uncontrolled compressed air of the external pressure source switches the main valve 50.
The main valve 50 is constructed as a 5/2 way valve. In the illustrated position, the controlled compressed air reaches the operating space A via the connection line 57. The piston 1 is consequently moved to the right together with the hydraulic pistons 9. Owing to the hydraulic medium which is located in the hydraulic spaces H1, the non-illustrated right-hand diaphragm is moved to the right, whereby the conveying space which is associated therewith is reduced. The right-hand diaphragm consequently conveys. At the same time, the left-hand diaphragm which is also not illustrated in
22 Clamping region of the diaphragm M1
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 013 108.3 | Mar 2010 | DE | national |
This application is the U.S. National Phase Patent Application of PCT International Application No. PCT/EP2011/001360, filed Mar. 18, 2011, which claims priority to German Patent Application No. 10 2010 013 108.3, filed Mar. 26, 2010, the contents of such applications being incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/001360 | 3/18/2011 | WO | 00 | 12/4/2012 |
