Abstract:
A control or shutoff valve with a housing includes a valve seat arranged within housing between feed and a discharge, and a shutoff element arranged to be moveable relative to the valve seat in the housing. At least one feed channel leading to the valve seat is arranged in the housing to supply a pressure medium to reduce cavitation phenomena.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention concerns a control or shutoff valve. 
       BACKGROUND 
       [0002]    Such a control or shutoff valve is known from U.S. Pat. No. 2,679,856 A. It has a housing, a valve seat arranged within the housing and a closure element arranged within the housing to be adjustable relative to the valve seat to form a throttling site. A feed channel leading to the valve seat to supply a pressure medium is also provided in the housing. The feed channel formed by a longitudinal groove and a radial channel in an inner housing part leads to a single opening that discharges downstream of the valve seat. 
         [0003]    A valve with a valve seat arranged in a housing and a closure element arranged within the housing to be adjustable relative to the valve seat is disclosed in published patent application GB 520 647 A. The valve is formed here by two annular components, between which an annular space is delimited. Water can be introduced into the annular space via a feed line in the housing and via an annular channel  18  and radial holes  19 . However, this annular space discharges downstream of the valve seat for the closure element situated in a closed position. 
         [0004]    The valve seat in a steam converting valve disclosed in published application DE 1 269 136 A has steam removal openings positioned concentric to a valve closure element, which is connected via auxiliary steam lines to injection nozzles positioned on the valve outflow side. 
         [0005]    DE 1 020 642 A discloses a pressure-reducing control valve in which several channels distributed around the periphery are provided for injection of cooling water at a constriction site of a housing. 
         [0006]    A ring nozzle is arranged behind the throttling site in a pressure-reducing valve known from DE 919 570 B. 
         [0007]    A valve with a double-walled outflow channel is disclosed in DE 73 25 078 U. The main stream here is enclosed by an oppositely running secondary stream via the annular cavity formed thereby. 
         [0008]    A valve in which fine, oblique atomization channels are arranged in the valve seat to form an atomizer is known from DE  712   163 . 
         [0009]    In the control valves used in the bottom outlets of dams, air is drawn into the pipeline arranged downstream to reduce cavitation. This is made possible by mounting ventilation parts at the outlet of the control valve. Air, which increases the pressure in the throttling gap and reduces the tendency toward cavitation, is drawn in via the partial vacuum on the throttling gap. However, this is only applicable in short pipelines downstream. As soon as the backpressure rises too strongly on the valve, air is no longer drawn in and cavitation is therefore no longer suppressed. 
         [0010]    The drawing in of air is not applicable in closed pipeline systems with low backpressure, since the air here leads to undesired pressure fluctuations. In order to reduce cavitation in closed pipeline systems, various control inserts are incorporated in the control valves, which reduce the pressure, reduce the flow rate within the control valve and thereby minimize the development of cavitation. However, the pressure differential often cannot be reduced completely free of cavitation by means of the control insert. 
       SUMMARY 
       [0011]    One aspect of the disclosure relates to a control or shutoff valve which permits improved cavitation reduction. 
         [0012]    Expedient embodiments and advantageous modifications are also disclosed. 
         [0013]    At least one feed channel leading to the valve seat to supply a pressure medium is arranged in the housing in the control or shutoff valve according to the invention. Water or another pressure medium with higher pressure can be supplied to the throttling gap on the valve seat via the feed channel. The pressure can therefore be raised in the throttling gap and the tendency toward cavitation reduced. The at least one feed channel leads to a valve seat ring provided with outlet openings on the housing, the outlet openings of the valve seat ring being arranged so that they discharge upstream of a closure seal in a closed position of the shutoff element. 
         [0014]    The valve seat ring expediently has a distributor channel connected to the outlet openings and to the at least one feed channel. 
         [0015]    The closure seal can be arranged on the housing or the shutoff element. 
         [0016]    The outlet openings can expediently discharge in the flow direction or at an angle to the flow direction of the medium flowing through the housing. The outlet openings can be arranged symmetrically or asymmetrically relative to the valve seat ring. 
         [0017]    The at least one feed channel is preferably connected via a line to a branch opening of the housing on the feed side. The medium flowing through the control or shutoff valve can be taken off at a location of higher pressure and sent via the line to a zone of low pressure. The line can be a separate component fastenable via screw connections or similar connections on the housing in the manner of a branch line. The line can thereby be simply maintained and replaced as required. However, the line can also be integrated in the housing. 
         [0018]    The control or shutoff valve according to the invention can be designed both in the basic form a “slide” or also in the form of a “valve” according to DIN EN  734 - 1 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Additional details and advantages of the invention are apparent from the following description of a preferred embodiment example with reference to the drawings. In the drawings: 
           [0020]      FIG. 1  shows a longitudinal section through a control valve designed as a plunger valve in an opened position; 
           [0021]      FIG. 2  shows a longitudinal section through the plunger valve depicted in  FIG. 1  in a closed position; 
           [0022]      FIG. 3  shows a detail view of a valve seat of the plunger valve depicted in  FIG. 1  in a cross section; 
           [0023]      FIG. 4  shows a detail view of the valve seat of  FIG. 3  in a perspective view; 
           [0024]      FIG. 5  shows another embodiment example of a control valve in a perspective view; 
           [0025]      FIG. 6  shows the control valve of  FIG. 5  in a cross section and 
           [0026]      FIG. 7  shows a detail view of a valve seat of the control valve depicted in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    A longitudinal cross section through a control valve designed here as a plunger valve to control water flow or to control water pressure is shown in different views in  FIGS. 1 and 2 . The depicted plunger valve contains a housing  1  preferably consisting of ductile cast iron, which has an outer part  3  provided with connection flanges  2  and an inner guide part  5  supported on the inside of outer part  3  via holding ribs  4 . An annular channel  6  is delimited between the outer part  3  and the inner guide part  5  of housing  1 , through which water or another medium can flow from a feed  7  to a discharge  8  of housing  1 . 
         [0028]    As follows from  FIGS. 1 and 2 , a closure element  9  designed here as a closure piston is guided to move axially in the inner guide part  5  of housing  1  open toward discharge  8 . The passage through annular channel  6  can be controlled by axial displacement of the piston-like closure element  9 . The piston-like closure element  9  in the depicted embodiment has a closure bushing  10 , a connecting rod bearing  11  and a retaining ring  12  to fasten the connecting rod bearing  11  to the closure bushing  10 . The closure bushing  10  can be moved axially within the guide part  5  via piston guide strips  13  and guided in sealed fashion radially relative to guide part  5  via a seal  14  designed here as a four-lip seal (quad-ring). 
         [0029]    The closure element  9  is driven in its longitudinal movement by a crank mechanism with a drive crank  16  fastened to a drive shaft  15  and a connecting rod  17  articulated with the drive crank  16 . The connecting rod  17  is articulated on one end via a crank pin  18  to the drive crank  16  and on its other end via a crank pin  19  to the connecting rod bearing  11 . By rotation of drive shaft  15 , the piston-like closure element  9  can be moved between a retracted, open position depicted in  FIG. 1  and a closed position depicted in  FIG. 2 . 
         [0030]    The housing  1  of the plunger valve depicted in  FIGS. 1 and 2  contains a valve seat  20 , shown enlarged in  FIG. 3 , against which the closure bushing  10  of closure element  9  stops in sealed fashion in the closed position via a closure seal  21  In the closed position of closure element  9  the outer end of the closure bushing  10  pointing to outlet  8  lies against the closure seal  21 . The annular closure seal  21  designed as a profile seal in the depicted valve seat  20  is tightened between a valve seat ring  22  and a retaining ring  23  fastened in the connection flange  2  of housing  1  on the discharge side. The valve seat ring  22  arranged in the flow direction in front of the closure seal  21  has a distributor channel  24  running as an annular groove on its outside, from which several outlet openings  25  distributed on the periphery of valve seat ring  22  and discharging on the inside of valve seat ring  22  branch off. Several feed channels  26  designed here as holes are arranged in the outer part  3  of housing  1  to supply liquid to distributor channel  24  of valve seat ring  22 . However, only one feed channel  26  can also be provided. Lines  27  that branch off from branch openings  28  on the feed side are connected to the outer ends of feed channels  26 . The branch openings  28  can be arranged in the vicinity of the connection flange  2  on the inflow side. 
         [0031]    Another embodiment example of a control valve is depicted in  FIGS. 5 to 7 . The housing  1  provided with the connection flanges  2  in this control valve has a cover  30  fastened on its top by means of screws  29 . A drive spindle  31  depicted in  FIG. 6  is mounted to rotate via a spindle bearing  34  and is sealed radially in cover  30  for displacement of a closure element  32  relative to a valve seat  33  arranged on housing  1 . The drive spindle  31  in the depicted embodiment can be rotated via a hand wheel  35 , which is mounted in an attachment sleeve  36  fastened to cover  30  and connected to drive spindle  31 . Displacement of the drive spindle  31 , however, can also occur via other drives. The housing  1  also has a feed  7  arranged here upstream of valve seat  33  and a discharge  8  arranged downstream of valve seat  33 . In contrast to the plunger valve depicted in  FIGS. 1 to 3 , however, the closure element  32  in this control valve cannot be moved in the axial direction of the inlet and outlet openings in the two connection flanges  2  but across the axial directions of the inlet and outlet openings in the two connection flanges  2 . 
         [0032]    The closure element  32  depicted in  FIG. 6  has a sleeve-like guide part  37  and a disk-like closure plate  38  with a slotted sleeve  39  fastened to its bottom. The closure element  32  can be moved via the sleeve-like guide part  37  in a corresponding opening  40  of cover  30  and guided radially sealed via a seal  41 . The valve seat  32  is formed here by a valve seat ring  42 , which is inserted into a corresponding recess  43  of housing  1 . In contrast to the embodiment of  FIGS. 1 to 3 , the valve seat ring  42  here is not arranged parallel to the connection flanges  2  of housing  1  but at right angles to them. Another difference relative to the embodiment of  FIGS. 1 to 3  is that the closure seal  44  provided here is not fastened to housing  1 , but to the closure plate  38  of closure element  32 . The closure seal  44 , however, could also be fastened to the valve seat ring  42 . 
         [0033]    It follows from  FIG. 7  that this valve seat ring  42  also contains on its outside a distributor channel  45  running as an annular groove and several outlet openings  46  branching off from distributor channel  45 . The outlet openings  46  are also arranged here so that they discharge upstream of the closure seal  44  in the depicted closed position of the shutoff element  9 . At least one feed channel  47  connected to distributor channel  45  is also provided here in housing  1  to supply a pressure medium to the distributor channel  45 . A line  48  depicted in  FIG. 5  is also connected to the outer ends of the feed channel  47 , which branches off from a branch opening  49  of housing  2  on the feed side. The branch opening  49  is arranged in the vicinity of the connection flange  2  on the feed side.