Abstract:
Diaphragm valve ( 1 ) comprising a housing upper part ( 2 ), which receives an actuating device ( 4 ) for actuating the valve ( 1 ), and a housing lower part ( 3 ), which has a receiving region ( 9 ) for receiving a diaphragm ( 11 ), wherein in the housing lower part ( 3 ) below the diaphragm ( 11 ) a central region forming a flow channel ( 17 ) is designed, wherein the cross-sectional surface of the flow channel ( 17 ) in the central region ( 51 ) of the housing lower part ( 3 ) is constant when the valve ( 1 ) is in the open state.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a diaphragm valve comprising a housing top part, which receives an actuating device for actuating the valve, and a housing bottom part, which has a receiving region for receiving a diaphragm, wherein in the housing bottom part beneath the diaphragm is configured a central region forming a flow channel. 
     In pipeline construction, diaphragm valves are used to regulate flow rates of different mediums. A diaphragm valve is characterized by few individual parts which come into contact with the medium. When the actual control element of the valve is replaced, only the diaphragm needs to be exchanged. The diaphragm valve tends to be insensitive to dirt contamination. A diaphragm valve is therefore well suited to the regulation of medium flows which contain solids. 
     DE 10 2004 001 045-A1 discloses a diaphragm valve of the generic type, wherein the cross-sectional area, in dependence on the flow path, steadily decreases from the housing inlet to the sealing land and then steadily increases again from the sealing land to the housing outlet. 
     Starting from this prior art, the object of the invention is to define a diaphragm valve wherein the flow through the valve housing is realized as evenly as possible and without obstacles. 
     SUMMARY OF THE INVENTION 
     This object is achieved by a diaphragm valve comprising a housing top part, which receives an actuating device for actuating the valve, and a housing bottom part, which has a receiving region for receiving a diaphragm, wherein in the housing bottom part beneath the diaphragm is configured a central region forming a flow channel, the cross-sectional area of the flow channel in the central region of the housing bottom part being constant in the open state of the valve. 
     It is advantageous for the diaphragm valve to be easily installable in existing pipelines. This is achieved by virtue of the fact that, viewed in the direction of flow, the cross-sectional area of the flow channel has successively a circular shape, an oval shape and a circular shape. The diaphragm valve is configured symmetrically in relation to the centerline of the diaphragm and can be installed in both directions in the piping system. 
     It is also advantageous for the diaphragm to be able to be installed as easily as possible in the valve housing. This is achieved by virtue of the fact that the housing top part has an inner housing and an outer housing, the outer housing being arranged such that it is connected to the receiving region of the housing bottom part. This is achieved by virtue of the fact that the diaphragm is arranged in the receiving region between the base of the receiving region and the bottom edge of the inner housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An illustrative embodiment of the invention is described with reference to the figures, wherein: 
         FIG. 1  shows a perspective view of a diaphragm valve according to the invention, 
         FIG. 2  shows a section through the diaphragm valve of  FIG. 1 , 
         FIG. 3  shows a perspectively sectioned region of the diaphragm valve, 
         FIG. 4  shows a representation of the cross-sectional areas in different portions of the flow channel of an existing diaphragm valve, 
         FIG. 5  shows a representation of the cross-sectional areas in different portions of the flow channel of the diaphragm valve according to the invention, 
         FIG. 6  shows a graph for comparing the change in cross-sectional area as a function of the length of the flow channel, 
         FIG. 7  shows a section through the assembly of diaphragm holder and spindle of the diaphragm valve, and 
         FIG. 8  shows a section through the diaphragm holder of the diaphragm valve. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a diaphragm valve  1  is shown in perspective representation. The diaphragm valve  1  substantially consists of a housing top part  2 , a matching housing bottom part  3 , and an actuating member, here represented as a handwheel  4  having an indicating pin  5 . The housing bottom part  3  has three openings  7 ,  8 ,  9  and a flow channel  17 . A first opening  9  is disposed between the housing top part  2  and the housing bottom part  3  and configured perpendicular to the flow channel  17  and is configured as a receiving region  9  for the diaphragm  11 . The two further openings  7 ,  8  are configured as pipe connecting elements  7 ,  8  for connecting the diaphragm valve  1  to the piping system. 
     In  FIG. 2 , the diaphragm valve  1  of  FIG. 1  is represented sectioned along the pipeline axis L. In  FIG. 3 , the housing bottom part  3  is sectioned along the pipeline axis L and shown in perspective representation. The flow channel  17  has no sharp edges or steps. The pipelines are screwed onto the two pipe connecting elements  7 ,  8 , or, in a corresponding embodiment, connected by another connection method, for example by arc welding or with a flange joint. The diaphragm valve  1  is configured symmetrically and indifferently with respect to the direction of flow. The axis of symmetry is here represented by the centerline of the diaphragm  11 . Both the first pipe connecting element  7  and the second pipe connecting element  8  can be used both as an inflow and as an outflow for the flow channel  17 . The diaphragm valve  1  can be installed in any position without regard to the direction of flow. 
     The receiving region  9  of the housing bottom part  3  is of circular configuration. The receiving region  9  serves not only to receive the diaphragm  11  but also to fasten the housing top part  2 . The housing top part  2  consists of an inner housing  10  and an outer housing  13 . On the outer side of the receiving region  9  is configured, for example, a screw thread  12  for the screw connection to the outer housing  13 . On the inner side of the receiving region  9 , as can be seen in  FIG. 3 , are configured a plurality of axially running recesses  14 ,  15 . The two identical recesses  14  disposed one opposite the other along the centerline of the diaphragm  11  serve for the fixing of the diaphragm  11 . A further four recesses  15  in each case, arranged offset by 90°, serve for the fixing of the inner housing  10 , which on the outer side has four cams which fit with the recesses  15 . The receiving region  9 , the inner housing  10  and the outer housing  13 , arranged concentrically to the inner housing  10 , of the housing top part  2  are of circular configuration. The diaphragm  11  thus has an indexing which is separate from the indexing of the inner housing  10 . The effect of this is that the inner housing  10  can be used turned, with the diaphragm position remaining constant. 
     The diaphragm  11  is arranged clamped in the receiving region  9  between the base  29  of the receiving region  9  and the bottom edge of the inner housing  10 . The clamping of the diaphragm  11  is achieved by the connection of the housing top part  2  to the housing bottom part  3 . The bottom edge of the inner housing  10 , the base  29  of the receiving region  9  and the rim of the diaphragm  11  respectively have beads  30 ,  31  and grooves  32 ,  33  configured complementary to one another, whereby a form closure between the diaphragm  11  and the valve housing and a defined position of the diaphragm  11  is achieved. 
     The new diaphragm valve  1  uses, for assembly, no screws, springs or nuts which bore through the housing bottom part  3  perpendicularly to the direction of flow, as is the case with traditional diaphragm valves. The valve housing hereby acquires a round instead of a square shape, viewed in the direction of the spindle. The diaphragm valve  1  can be produced substantially from plastics parts and can be produced without metallic elements such as screws, springs and nuts. Should the clamping of the diaphragm  11  slacken in the course of its life, then the housing top part  2  can subsequently be further screwed together with the housing bottom part  3  to ensure adequate clamping. Because the clamping of the diaphragm  11  is produced solely by the screwing of the housing top part  2  in the housing bottom part  3 , the clamping is substantially more uniform than with traditional diaphragm valves, where more of a punctiform clamping is achieved by four screws in the corners of the valve housing. 
     The flow channel  17  between the pipe connecting elements  7 ,  8  is configured in the housing bottom part  3  such that the cross-sectional area is constant over the entire length of the flow channel  17  in a central region  51  of the diaphragm valve  1  in the open state. Viewed in the direction of flow, the cross-sectional area assumes successively a circular shape, an oval shape and again a circular shape. The transitions between these shapes are of continuous configuration. 
     In  FIG. 4 , twelve sections through the flow channel of a traditional diaphragm valve are represented. The sections are placed at successive points in the flow channel, from the start of the flow channel by the pipe connecting element to the centerline of the diaphragm. The cross-sectional areas are shown respectively in shaded representation. The shape of the cross-sectional areas changes from circular via bottle-shaped, rectangular with rounded corners, to drip-shaped. 
     In  FIG. 5 , a further twelve sections through the flow channel  17  of the diaphragm valve  1  according to the invention are represented. The sections are likewise made at successive points in the flow channel  17 , from the start of the flow channel  17  by the pipe connecting element  7 ,  8  to the centerline of the diaphragm  11 . The cross-sectional areas are shown respectively in shaded representation. The shape of the cross-sectional areas changes from circular at the start of the housing bottom part  3  to oval in a central region  51  beneath the diaphragm  11 . 
     In  FIG. 6 , the change in cross-sectional area in the flow channel  17  over half the length of the diaphragm valve  1  from the inlet of the housing bottom part  3  to the centerline of the diaphragm  11  is represented. The change is represented related in percentages to the cross-sectional area at the inlet of the housing bottom part  3 . The valve length comprises an inlet region  50  from 0% to around 50% of half the valve length and a central region  51  from around 50% to 100% of half the valve length. In  FIG. 6 , the line A represents the change in cross-sectional area in the flow channel of a traditional diaphragm valve. From the line A in  FIG. 6  can be read that the cross-sectional area in the central region of the diaphragm valve, i.e. beneath the diaphragm, repeatedly drastically changes, which leads to considerable pressure differences and fluctuations in the efficiency of the diaphragm valve. 
     The shaded region B in  FIG. 6  represents the change in cross-sectional area in the flow channel  17  of the diaphragm valve  1  according to the invention. The region B likewise depicts the tolerance limits of the percentage change in the diaphragm valve  1  according to the invention. From the region B in  FIG. 6  can be read that, in the inlet region  50  of the flow channel  17 , the cross-sectional area steadily declines from 100% to around 85% to 75%, and that, in the following central region  51 , the cross-sectional area remains constant at around 75% to 85% of the initial value. 
     In  FIG. 2 , further elements of the valve actuating mechanism are visible in the inner housing  10 : a pressure piece  16 , which serves for the uniform deformation of the diaphragm  11 , the actual spindle  18 , and a spindle nut  19 , which ensures that the rotary motion of the handwheel  4  is converted into an axial motion of the spindle  5  with the pressure piece  16 . In  FIG. 3 , the housing bottom part  3 , the diaphragm  11  and a diaphragm pin  20  are shown in perspective and sectioned representation. 
     In  FIG. 7 , a connecting nut  21  as a connecting member between the diaphragm pin  20  and the spindle arrangement is shown in sectioned representation. The diaphragm pin  20  is a metal pin, which is fastened in the center point of the diaphragm  11  and which has an external thread. The metal pin  20  is screwably connected to a small retaining nut  25 . The retaining nut  25  has a height which is less than the depth of the lower part of the longitudinal bore  22  and lies with play in the axial direction into the connecting nut  21 . The connecting nut  21  itself is configured as a larger nut, which is inserted in a hexagonal hole in the pressure piece  16  likewise with play in the axial direction. In  FIG. 8 , the connecting nut  21  together with the retaining nut  25  is shown in sectioned representation. The connecting nut  21  itself has a longitudinal bore  22  for receiving the spindle  18  and a transverse bore  23  for receiving a transverse pin  24 , the latter likewise being connected to the spindle  18 . 
     In the closing operation, the closing force is transmitted with the connecting nut  21  to the pressure piece  16  and the diaphragm  11 . Upon closure of the diaphragm valve  1 , the retaining nut  25  and the diaphragm pin  20  move freely upward. The effect of this is that the forces for actuating the diaphragm valve  1  are decoupled and the diaphragm  11  is subjected to the least possible load. The spindle  18  is not fixedly connected to the diaphragm  11 . The handwheel  4  turns without axial motion and, during actuation, does not distance itself from the housing top part  2  of the diaphragm valve  1 . The handwheel  4  is connected to the spindle nut  19  by means of a hollow splined shaft. The spindle nut  19  thus does not perform an axial motion. The spindle  18  is engaged with the thread of the spindle nut  19 . The spindle nut  15  thus converts the rotary motion of the handwheel  4  into an axial motion of the connecting nut  21 . Upon opening of the diaphragm valve  1 , the diaphragm  11  is raised with the retaining nut  25  connected to the diaphragm pin  20 . 
     The diaphragm valve  1  is characterized by a compact and round design. It is produced substantially from injection-molded parts. As a result of the particular configuration of the flow channel  17 , the pressure loss in the diaphragm valve is minimal. As a result of the screw connection of the housing top part  2  to the housing bottom part  3 , a subsequent adjustment of the diaphragm fastening is simplified and the diaphragm  11  is clamped more uniformly all the way round. In place of the handwheel  4 , a pneumatic or other remote-controllable drive can also be mounted on the diaphragm valve  1 .