Abstract:
A diaphragm pump, in which 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 by a hydraulic medium.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    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. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a diaphragm pump having at least one diaphragm. 
       BACKGROUND OF THE INVENTION 
       [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
       SUMMARY OF THE INVENTION 
       [0008]    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. 
         [0009]    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 (M 1 , M 2 ) by means of a hydraulic medium, characterised in that the diaphragm pump is a dual-diaphragm pump having at least two diaphragms (M 1 , M 2 ), a hydraulic medium moving or driving the diaphragms (M 1 , M 2 ), at least one hydraulic piston moving the hydraulic medium, and in that two diaphragms (M 1 , M 2 ) are mechanically connected to each other by means of a connection element, in particular a rod or a pipe, respectively. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]    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. 
         [0019]    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. 
         [0020]    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. 
         [0021]    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. 
         [0022]    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. 
         [0023]    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. 
         [0024]    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. 
         [0025]    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. 
         [0026]    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. 
         [0027]    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. 
         [0028]    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. 
         [0029]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    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. 
           [0031]      FIG. 1 : is a perspective view of the diaphragm pump according to the invention in the form of a dual-diaphragm pump; 
           [0032]      FIG. 2 : is a sectioned illustration of the diaphragm pump according to  FIG. 1 ; 
           [0033]      FIG. 3 : is a sectioned illustration through the dual-diaphragm pump according to  FIGS. 1 and 2 ; 
           [0034]      FIG. 4 : is a partial cutout from  FIG. 3 ; 
           [0035]      FIG. 5 : is a pneumatic diagram for a diaphragm pump according to the invention having a 5/2 way valve as a main valve; 
           [0036]      FIG. 6 : is a pneumatic diagram for a diaphragm pump according to the invention having a 4/2 way valve as a main valve. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]      FIGS. 1 and 2  are perspective views of the diaphragm pump according to the invention in the form of a dual-diaphragm pump. The dual-diaphragm pump has a housing cover  19  and a housing portion  11  which receives the cylinder  10  of the hydraulically acting piston/cylinder system  9 ,  10 . The housing portion  11 , as illustrated in  FIG. 2 , is secured by means of coaxial screws  11   a  to the axial cylinder wall  3  of the first piston/cylinder system. The diaphragm M is clamped at  22  by the housing cover  19  and the housing portion  11  (see  FIGS. 3 and 4 ). The housing cover  19  and housing portion  11  are connected to each other by means of the screws  19   a  and fix the diaphragm M in position. The housing cover  19  forms at the top and bottom a receiving member for a non-return valve  24 , respectively. The non-return valves  23 ,  24  are inserted before the housing flanges  25 ,  27  are screwed to the housing cover  19  into the corresponding recesses of the housing cover  19 . Additional seals prevent conveying medium from being able to be introduced around the housing of the non-return valves  23 ,  24 . The axial walls  3  of the first piston/cylinder system are retained with spacing by means of spacer sleeves  7  and connected to each other by means of the screws  6 . The cylindrical wall sleeve  2  which forms the cylinder is further arranged between the walls  3  in a pressure-tight manner, additional seals ensuring the tightness. The screws  6  have a screw head  6   a  and at the end thereof a thread  6   b  with which they are screwed to the first axial wall  3 . 
         [0038]    In the cylinder  2 ,  3  of the first piston/cylinder system, there is arranged the first piston  1  which is formed by two discs  1   a ,  1   b  and which separates the operating spaces A and B from each other. The discs  1   a ,  1   b  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  3   b  which also serve to better conduct heat and to provide rigidity and save material. The piston  1  has a continuous seal  1   c  which abuts the inner wall of the cylinder  2  in a sealing manner. 
         [0039]    When the piston  1  is assembled, the piston rods  8   a,    8   b  are pushed beforehand through the holes  1   d  until the collars  8   c  rest in the corresponding recesses  1   e  of the piston discs  1   a ,  1   b . Owing to the assembly of the piston discs  1   a ,  1   b , the piston rods  8   a,    8   b  are secured to the piston  1  in a positive-locking manner. 
         [0040]    The piston rods  8   a,    8   b  extend through the holes  3   a  of the axial walls  3 , seals  56  ensuring that no compressed air from the operating spaces A, B reaches the hydraulic spaces H 2 . With the ends  8   d  thereof, the piston rods  8   a,    8   b  are connected to the hydraulic pistons in a sealing manner by means of screws  60 . The piston rods  8   a,    8   b  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  5   a  thereof having the outer thread into the diaphragm plate  20 . The diaphragm plate  20  is formed in the diaphragm M 1  in the centre  21  thereof. 
         [0041]    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 H 1 , H 2  from each other. The two hydraulic spaces H 2  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 H 1  and H 2  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. 
         [0042]    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. 
         [0043]    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  36   a  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  36   a  and which is formed by a continuous groove. In the region  36   a,  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 . 
         [0044]    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  29   a  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  29   a  and which is formed by a continuous groove. In the regions  29   a,  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 . 
         [0045]    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. 
         [0046]    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. 
         [0047]    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 F 1  is reduced, the conveying medium which is located in the conveying space F 1  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 F 1  by the diaphragm M 1  being moved back, conveying medium is drawn from the supply line  36  into the conveying space F 1  via the non-return valve  23  which is open. During the suction phase, the non-return valve  24  is closed. 
         [0048]      FIG. 5  shows a pneumatic diagram of the diaphragm pump according to  FIGS. 1 to 4 . The diaphragm pump which is operated with compressed air has a compressed air inlet  43  which is advantageously arranged on the main valve  50 . In or on the main valve  50  there may be arranged the pressure control device  45  which is connected to the inlet  43  by means of the input line  44 . The pressure control device  45  may be a proportional valve which may have an adjustment mechanism, for example, in the form of an adjustment screw, by means of which a spring can be pretensioned for pressure adjustment. If, by means of the external compressed air source (not illustrated), uncontrolled pressure of 7 bar is provided, controlled compressed air of, for example, 5.5 bar can be supplied to the main valve  50  by means of the pressure control device  45  via the connection line. 
         [0049]    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 . 
         [0050]    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 H 1 , 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  FIG. 5  draws conveying medium from the supply line into the conveying space thereof. When the right-hand dead centre point is reached, the right-hand switching valve  14  is switched via the extension  15  so that the main valve  50  is also switched. On the way to the left, the connection of the operating space A to the connection line  47  is first interrupted. Afterwards, the two operating spaces are bypassed with respect to each other so that the pretensioned compressed air located in the operating space B can expand into the operating space A. A specific time period is available for this until the main valve  50  has ultimately completely switched through and compressed air which is controlled via the connection line  47  is directed into the operating space B, whereby the piston  1  is moved to the left. The remaining compressed air which has not yet been expanded in the pressure space B subsequently expands via the valve outlets  51  via the silencers  35  into the environment. 
         [0051]      FIG. 6  illustrates an alternative embodiment in which the main valve  50  is constructed as a 4/2 way valve. The main valve  50  differs from the main valve illustrated in  FIG. 5  simply in that only one outlet  51  is provided. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         A, B Operating space of the first piston/cylinder system 
         M 1 , M 2  Diaphragm 
           1  First piston of the first piston/cylinder system 
           1   a ,  1   b  Piston discs 
           1   c  Seal 
           1   d  Hole 
           1   e  Recess for collar  8   c    
           2  Cylinder of the first piston/cylinder system 
           2   a  Outer cooling rib of the cylinder  2   
           3  Axial cylinder wall of the first piston/cylinder system 
           4  Screws 
           5  Connection element 
           5   a  Thread of the connection element  5   
           6  Connection screw 
           7  Spacing sleeve 
           8   a,    8   b  Piston rod 
           8   c  Collar 
           9  Hydraulic piston 
           10  Cylinder of the hydraulically acting piston/cylinder system 
           11  Housing portion 
           12  Seal 
           13  Differential pressure valve (p H1 &gt;P H2 ) 
           14  Switching valve 
           15  Valve control member 
           16 ,  17 ,  18  Channel/connection line 
           19  Housing cover 
           20  Diaphragm plate 
           21  Diaphragm region, in which the diaphragm plate  20  is arranged 
       
     
         [0080]      22  Clamping region of the diaphragm M 1  
     23  Non-return valve in the supply channel (only illustrated in the left chamber)     24  Non-return valve in the outlet channel (only illustrated in the left chamber)     25  Housing flange having an outlet channel  26  (outlet housing)     26  Outlet channel     27  Housing flange with supply channel  28  (inlet housing)     28  Supply channel     29  Pressure line     30  Inner space of the pressure line  29       31  Through-opening in the wall of the pressure line  29       32  Annular space which surrounds the pressure line  29       33  Pump outlet for conveying medium     34  Plug having a screw-in thread     35  Silencer for discharging the expanding compressed air     36  Supply line     37  Inner space of the supply line  36       38  Through-opening in the wall of the supply line  36       39  Sealing rings     40  Annular space which surrounds the supply line  36       41  Pump inlet for conveying medium     42  Base     43  Inlet for uncontrolled compressed air of an external compressed air source     44  Connection line     45  Pressure control device in the form of a proportional valve     46  Adjustment mechanism for controlled outlet pressure of the pressure control device  46       47  Connection line, guides controlled compressed air to the main valve  50       48 ,  49  Connection line for uncontrolled compressed air     50  Main valve     51  Outlets of the main valve, which are connected to the silencers  35       52 ,  53  Control line of the switching valve  14  to the main valve  50       54 ,  55  Outlet to the outer side     56  Seal     57  Connection line to the operating space A     58  Connection line to the operating space B     66  Throttle in the switching valve  14