Abstract:
A diaphragm pump for conveying liquids for application in a sterile environment includes passageways for conduction of a liquid, and check valves for controlling a flow of liquid through the passageways. The diaphragm pump is constructed in such a way that all surfaces of the passageways in contact with the liquid being conveyed are disposed at a slant. In addition, all transitions between liquid-conducting surfaces have a gradual configuration. For drainage of the diaphragm pump, the shutoff elements of the check valves are lifted off their valve seat through temporary generation of a magnetic field.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of International PCT Application No. PCT/EP2005/010018, filed Sep. 16, 2005, pursuant to 35 U.S.C. 119(a)-(d). This application also claims the benefit of prior filed U.S. provisional Application Ser. No. 60/725,943, filed Oct. 12, 2005, pursuant to 35 U.S.C. 119(e). 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a diaphragm pump for the transport of liquids.  
         [0003]     Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.  
         [0004]     German utility model DE 33 10 131 A1 describes a diaphragm pump in the form of a double-diaphragm pump, having a pump housing which includes two product chambers and two pressure chambers which are respectively separated from one another by a diaphragm. The diaphragms are connected together by a common coupling rod which is guided through the two pressure chambers. When the pump is operated, compressed air is conducted alternatingly into one of the two pressure chambers, whereby the diaphragm of the pressure chamber being acted upon executes a discharge stroke into the adjacent product chamber, and the second diaphragm executes a suction stroke as a consequence of the linkage via the coupling rod. The pressure chambers are alternatingly acted upon and exhausted through provision of a control valve device which is disposed in parallel relationship to the coupling rod and cyclically clears individual control orifices.  
         [0005]     When using diaphragm pumps in a sterile environment, for example in the pharmaceutical field or in biochemistry, stringent standards must be met. A precondition is that the pump can be completely emptied of any liquid before shutdown to prevent any residues of liquid, and the pump can be thoroughly purged with a flushing liquid.  
         [0006]     It would therefore be desirable and advantageous to provide an improved diaphragm pump to obviate prior art shortcomings and to allow a complete drainage and purging of the pump.  
       SUMMARY OF THE INVENTION  
       [0007]     According to one aspect of the present invention, a diaphragm pump includes passageways for conduction of a liquid, and check valves for controlling a flow of liquid through the passageways, wherein the passageways have liquid-conducting surfaces which are all of slanted configuration.  
         [0008]     According to another aspect of the present invention, a diaphragm pump includes passageways for conduction of a liquid, and check valves for controlling a flow of liquid through the passageways, wherein the passageways have liquid-conducting surfaces, with all neighboring liquid-conducting surfaces being at least partially connected to one another in a gradual manner.  
         [0009]     According to still another aspect of the present invention, a diaphragm pump includes a check valve having a shutoff element for controlling a flow of liquid through a valve seat, and a device for random lifting of the shutoff element off the valve seat independently of a pressure state of the pump, with the device being constructed to generate a magnetic field for interaction with the shutoff element.  
         [0010]     According to yet another aspect of the present invention, a diaphragm pump includes at least one pumping chamber intended for a liquid to be conveyed and fluidly communicating with an inlet and an outlet for intake and discharge of liquid, a pressure chamber, and a diaphragm which separates the pumping chamber from the pressure chamber, wherein the inlet and/or the outlet is/are shaped in such a manner as to produce a direct contact flow upon at least one portion of the diaphragm and/or a marginal zone of the pumping chamber.  
         [0011]     To ensure clarity, it is necessary to establish the definition of several important terms and expressions that will be used throughout this disclosure.  
         [0012]     The term “all” in connection with the surfaces is to be understood as relating to at least those surfaces which come into contact with the liquid.  
         [0013]     The term “slanted” relates, when the pump is operative, to a surface disposition which is not perpendicular to the direction of the gravitational force or a force resulting from the gravitational force and a further force.  
         [0014]     The term “liquid-conducting surface” relates to a surface which comes into contact with the liquid as a result of the gravitational force or a force resulting from the gravitational force and a further force, and thus represents the lower boundary surface or the lower surface segment (when a circular cross section is involved for example) of a chamber or line conducting the liquid.  
         [0015]     The term “gradual” relates in particular to even transitions without any recognizable abutting edges; still, this term may also cover any bump that does not require a movement by the liquid in opposition to the gravitational force as the liquid flows through the pump. As a result of the provision of a gradual transition, residual liquid is prevented from settling upon any steps or elevations during drainage of the pump and from remaining in the pump. Valve seats of check valves in conventional pumps typically exhibit such steps where liquid is able to settle.  
         [0016]     According to another feature of the present invention, not only the liquid-conducting surfaces of the diaphragm pump may be constructed slanted but any surface that comes into contact with the liquid.  
         [0017]     Furthermore, the liquid being conveyed can flow against the product chamber(s) from the inlet and/or outlet of the respective product chamber in such a manner that a direct contact flow is generated upon at least one portion of the diaphragm and/or a marginal zone of the product chamber. In this way, the effectiveness of the purging process with flushing liquid can be improved during operation of the pump.  
         [0018]     The term “direct contact flow” as used in the following description relates to a liquid flow which is targeted within the product chamber in particular upon certain areas which undergo little liquid exchange during purging. These areas are oftentimes encountered in the marginal zones of the product chamber(s) and in particular at the connection areas where the diaphragm is clamped to the housing of the product chamber(s).  
         [0019]     The direct contact flow is thus different from a tangential flow in which the liquid is conducted at an acute angle in relation to a diaphragm surface from the inlet and/or outlet into the pumping chamber. A tangential flow is unsuitable to reach all areas. In contrast thereto, a direct contact flow in accordance with the present invention allows a routing of any cleansing medium (flushing agent) in a targeted manner to reach all areas.  
         [0020]     According to another feature of the present invention, all areas within a product chamber can be contacted by inflowing liquid at an angle of 90°±20°, preferably of 90°÷10°, and currently preferred of 90°±5°, (relating to the entire area). This provides for an especially effective purging of these areas by generating turbulences within the liquid flow to positively affect the liquid exchange.  
         [0021]     According to yet another aspect of the present invention, a check valve for application in a pump includes a valve housing having a first housing portion and a second housing portion, with the first housing portion being defined by an inside dimension which is smaller than an inside dimension of the second housing portion, with the valve housing forming a valve seat at a contact area of the housing portions, wherein the housing portions are disposed in offset relationship such that a transition between the housing portions is gradual in a region of the valve seat, and a shutoff element movably supported in the valve housing for cooperation with the valve seat.  
         [0022]     According to another feature of the present invention, the housing portions of the valve housing may each have an inner cross section of circular configuration, with the shutoff element configured in the shape of a ball.  
         [0023]     According to another feature of the present invention, the transition may be positioned on a gravity side of the check valve. Drainage of the entire liquid during emptying of the pump is ensured as a result of the gradual configuration of the valve seat on the one side of the check valve on which the liquid flows off as a result of the gravitational force (gravity side).  
         [0024]     According to still another aspect of the present invention, a check valve for application in a pump includes a valve housing, a shutoff element movably supported in the valve housing and having at least one portion exhibiting a magnetic property, and a device for applying a magnetic field for lifting the shutoff element off a valve seat in opposition to a closing force. In this way, a magnetic field can be used to lift the shutoff elements of the check valve from the valve seat, independently of the pressure conditions produced by the pump. Suitably, the at least one portion of the shutoff element may be made of ferromagnetic material.  
         [0025]     Opening of the check valve, when needed, through application of a magnetic force is beneficial because of the absence of any mechanical valve lifters which oftentimes are routed from outside through the valve housing to the shutoff body and thus have the disadvantage of constituting further (moving) structures inside the pump and requiring also an additional seal in the valve housing.  
         [0026]     According to another feature of the present invention, the shutoff element may be implemented as a ball. Suitably, the ball includes an iron core. Ball check valves are characterized by a reliable closing so that the need for a particular guidance of the shutoff element can be eliminated. The ferromagnetic portion of the ball check valve may be designed in particular as ball core. As a result, the material of the ball jacket can be selected according to need, for example according to the liquid being conveyed. In addition, the use of elastic materials for the jacket can improve the sealing action of the ball in its valve seat. PTFE is currently a preferred material for the ball jacket. Ferromagnetic materials (in particular iron) are especially useful for the construction of the ball core. The provision of an iron core is also beneficial because of the increase in specific weight of the ball which may result, i.a., in an improvement of the suction effect. This can be influenced through dimensioning of the iron core.  
         [0027]     According to another feature of the present invention, the device may include a permanent magnet for temporary attachment onto the check valve for application of the magnetic field. In other words, the permanent magnet is attached only for opening the check valve, regardless of the pressure conditions. When metallic valve housings with magnetic properties are involved, the permanent magnet normally adheres to the intended site automatically so that the need for further holding devices can oftentimes be eliminated.  
         [0028]     The use of permanent magnets is also beneficial because the need for electricity is eliminated so that the check valves according to the invention are useful for the transport of inflammable liquids for example.  
         [0029]     According to still another aspect of the present invention, a check valve for application in a pump includes a valve housing, and a shutoff element movably supported in the valve housing, wherein the valve housing forms a two-dimensional valve seat having a shape in conformity to a contour of the shutoff element in a contact zone between the valve seat and the shutoff element.  
         [0030]     Suitably, the shutoff element is a ball. Thus, the valve seat has a ring surface which is formed two-dimensionally concave with a radius in correspondence to the ball radius. By matching the ring surface of the valve seat to the contour of the shutoff element, an increase in the effective sealing surface and thus of the sealing action is realized. In contrast thereto, conventional ball valves typically have only a valve seat in the form of a (sealing) edge.  
         [0031]     According to yet another aspect of the present invention, a method of draining a pump with at least two check valves includes the step of lifting the check valves off their valve seat through temporary generation of a magnetic field. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0032]     Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:  
         [0033]      FIG. 1  is a cross section of a first embodiment of a double-diaphragm pump according to the present invention;  
         [0034]      FIG. 2  is a side elevational view of the double-diaphragm pump of  FIG. 1 ;  
         [0035]      FIG. 3  is a cross section of a second embodiment of a double-diaphragm pump according to the present invention;  
         [0036]      FIG. 4  is a perspective illustration, on an enlarged scale, of a housing of a check valve for incorporation in a double-diaphragm pump according to the invention;  
         [0037]      FIG. 5  is a cross section of a third embodiment of a double-diaphragm pump according to the invention;  
         [0038]      FIG. 6  is a side elevational view of the double-diaphragm pump of  FIG. 5 ;  
         [0039]      FIG. 7  is a cross section of a fourth embodiment of a double-diaphragm pump according to the invention; and  
         [0040]      FIG. 8  is a cross section of a fifth embodiment of a double-diaphragm pump according to the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0041]     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.  
         [0042]     Turning now to the drawing, and in particular to  FIG. 1 , there is shown a cross section of a first embodiment of a double-diaphragm pump according to the present invention, including a pump housing  1  with two product (pumping or working) chambers  2 ,  3  located in outer zones of the pump housing  1  for conveying a liquid via feed lines  4  disposed outside of the pump housing  1 , as also shown in  FIG. 2 . The product chambers  2 ,  3  are separated by respective diaphragms  5 ,  6  from respective pressure chambers  7 ,  8 . The diaphragms  5 ,  6  are completely smooth, continuous, and made, for example, of PTFE or EPDM or other suitable material, in the absence of diaphragm disk and further seals.  
         [0043]     In operation, compressed air is fed to the pump via a (not shown) feed line and alternatingly supplied by a control valve device, generally designated by reference numeral  9  either to the left pressure chamber  8  or to the right pressure chamber  7 . While one pressure chamber is acted upon, the other pressure chamber is respectively exhausted.  
         [0044]     As compressed air is admitted into one of the pressure chambers  7 ,  8 , a working stroke is executed by the respective diaphragm  5 ,  6  into the product chamber  2 ,  3  (the right chamber  2  in  FIG. 1 ). The working stroke of the right diaphragm  5  thus decreases the effective volume of the product chamber  2  and pumps the liquid through a right outlet valve  10  in an area of a top pump outlet  11 .  
         [0045]     At the same time, the left diaphragm  6  is drawn back into and exhausts the respective pressure chamber  8  as a consequence of a linkage between the two diaphragms  5 ,  6  by a coupling rod  12 . As a result of the suction stroke, carried out by the diaphragm  6 , the effective volume of the left product chamber  3  is increased and liquid is drawn on an inlet side  22  on the bottom of the pump through a check valve  13  having a shutoff body in the form of a ball  14  which is thus lifted off a valve seat  15  to clear a passage. At the same time, the ball  14  of a check valve  17  on the outlet side is pulled into the valve seat  15  to close the outlet.  
         [0046]     Suitably, the movement of the balls  14  of each check valve  10 ,  13 ,  17  is restricted by a stroke limiter  16 .  
         [0047]     As soon as the right diaphragm  5  concludes its working stroke, compressed air is routed into the left pressure chamber  8 . The left diaphragm  6  thus commences its working stroke, whereas the right diaphragm  5  executes a suction stroke.  
         [0048]     Oftentimes it is necessary to drain the pump before shutdown or change of the liquid being pumped. For this purpose, permanent magnets  18  are temporarily placed upon all valves  10 ,  13 ,  17 . For sake of simplicity,  FIG. 1  show the attachment of a permanent magnet  18  only for the check valves  10   13  on the right-hand side of the double-diaphragm pump. The permanent magnets  18  generate a magnetic field to lift the balls  14  of the check valves  10 ,  13 ,  17 , which have a (not shown) ferromagnetic iron core, from their valve seats  15 . Thus, all supply lines and discharge lines are open regardless of the stroke position of the diaphragms  5 ,  6 . Liquid can be bled from the pump—in the direction of the gravity in opposition to the pump direction.  
         [0049]     A continuous operation of the pump at possibly reduced stroke number may hereby assist the emptying of the pump.  
         [0050]     To prevent retention of liquid residues, all surfaces of the double-diaphragm pump in contact with the liquid have a slanted configuration. In other words, the double-diaphragm pump according to the present invention is devoid of any horizontal liquid-contact surfaces. Drainage of liquid may also be enhanced by reducing the mean surface depth of roughness. In addition, the double-diaphragm pump according to the present invention is devoid of any bumps between the liquid-conducting surfaces so the flow of liquid does not need to overcome any areas in opposition to the gravity during drainage.  
         [0051]     The check valves  10 ,  13 ,  17  have each a valve housing which is configured in such a way that the draining liquid is not required to overcome a bump. The valve housing is hereby composed of two circular valve housing portions of different diameter and disposed in offset relationship so as to connect smoothly along a straight line in a lower region thereof.  
         [0052]     In order to ensure a reliable and tight seat of the balls  14 , the ring-shaped valve seat  15 , i.e. the hereby formed plane, is not arranged perpendicular to the center axes of the two housing portions but assumes a slanted disposition.  
         [0053]     Furthermore, the valve seats  15  are of two-dimensionally concave configuration at a radius in substantial correspondence with the radius of the ball. As a result, as shown in  FIG. 4 , sealing surfaces are established between the valve seats  15  and the balls  14  which are able to improve the sealing action in comparison to sealing edges of conventional pumps. The valve seats  15  can be produced by a spherical miller which would be positioned in the present exemplified embodiment in parallel, slightly offset relationship to a longitudinal center axis of the smaller valve housing portion on this valve housing portion and impose the concave shape onto the valve seat  15  which has been formed already by the penetration of the two valve housing portions.  
         [0054]     Turning now to  FIG. 3 , there is shown a second embodiment of a double-diaphragm pump according to the invention. Parts corresponding with those in  FIG. 1  are denoted by identical reference numerals and not explained again. The description below will center on the differences between the embodiments. In this embodiment, provision is made for tandem diaphragms  5   a ,  5   b ,  6   a ,  6   b . As a consequence, blocking chambers  19 ,  20  are defined within the tandem diaphragms  5   a ,  5   b ,  6   a ,  6   b . This type of double-diaphragm is able to meet even extreme safety requirements.  
         [0055]     In view of the modular structure, a double-diaphragm pump according to the invention may be retrofitted in a simple manner to a tandem pump.  
         [0056]     FIGS.  5  show a cross section and a side view of a third embodiment of a double-diaphragm pump according to the invention. In the following description, parts corresponding with those in  FIG. 1  will be identified, where appropriate for the understanding of the invention, by corresponding reference numerals each increased by “100”. The description below will center on the differences between the embodiments. The diaphragm pump according to  FIG. 5  differs from the previously described embodiments in particular by the shape of the product chambers  102 ,  103  as well as the course of the feed lines  104 . While the double-diaphragm pumps of  FIGS. 1 and 3  have feed lines (inlet/outlet)  4  implemented as continuous duct which is provided with a connection to the product chambers  2 ,  3  only on one side so as to realize a rectilinear, essentially laminar flow of liquid between inlet  22  and outlet  11  to effect enhanced flow resistance, the feed lines  104  of the double-diaphragm pump of  FIG. 5  (like also in the double-diaphragm pumps of  FIGS. 7 and 8 ) enter with their full cross section into the product chambers  102 ,  103 . Furthermore, the feed lines  104  are bent shy of the entry into the product chambers  102 ,  103  so that the flow of liquid is established at a relatively great, almost perpendicular angle in relation to the vertical planes of the diaphragms  105 ,  106 . As a result, turbulences are generated within the liquid flows and a good liquid exchange is realized in the area of the ports of the product chambers  102 ,  103 .  
         [0057]      FIG. 5  shows that the flow in the lower feed line  104  of a product chamber  102 ,  103  is deflected to a greater extent than the upper feed line  104 . As the risk of liquid deposits during drainage of the pump is greater in the area of the bottom inlet  22 , as viewed in gravity direction, the deflection of the upper feed line  104 , as viewed in gravity direction, can be made slighter, accompanied by reduced development of turbulences, so that the flow resistance of the pump can be positively affected.  
         [0058]     The lower feed line  104  is deflected by about 89°. A feed line at an angle of not equal 90° (in relation to the horizontal) ensures that also the entry portion of the feed line  104  is (slightly) slanted to assist a drainage of liquid during emptying of the pump.  
         [0059]      FIG. 7  shows a cross section of a fourth embodiment of a double-diaphragm pump according to the invention. Parts corresponding with those in  FIG. 5  will be identified, where appropriate for the understanding of the invention, by corresponding reference numerals increased by “100”. The description below will center on the differences between the embodiments. In this embodiment, provision is made a lower feed line  204  which is angled in a same way as the upper feed line  204 . Thus, selection of different flow deflections can result in different generation of turbulences. In other words, the size of the flow deflection as well as the flow contact angle upon the respective areas within the product chambers  202 ,  203  can be randomly selected and suited to the demanded purging effect and accompanying increase in flow resistance.  
         [0060]      FIG. 8  shows a cross section of a fourth embodiment of a double-diaphragm pump according to the invention. Parts corresponding with those in  FIG. 5  are denoted by identical reference numerals and not explained again. The description below will center on the differences between the embodiments. In this embodiment, provision is made for a tandem diaphragm  105   a ,  105   b ,  106   a ,  106   b  so as to define enclosed blocking chamber  119 ,  120  adjacent to each product chamber  102 ,  103 .  
         [0061]     A double-diaphragm pump in accordance with the invention is suitable for pumping liquids also in a sterile environment, for example in the pharmaceutical field or in the field of biochemistry. These fields of application employed exclusively rotary pumps heretofore.  
         [0062]     While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.  
         [0063]     What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: