Abstract:
A valve arrangement for reciprocating machine, where the arrangement ( 1 ) comprises an in-valve ( 18 ) and an out-valve ( 19 ), each valve ( 18 ), ( 19 ) being a springloaded one-way valve designed to open for flow when the pressure differential in the direction of flow provides a force that exceeds the spring tension, wherein the valves ( 18, 19 ) are mounted in a casing ( 8 ) that forms or is connected to the cylinder head of the reciprocating engine ( 2 ). The in-valve ( 18 ) and the out-valve ( 19 ) are mounted in a sleeve ( 16 ) designed to be fitted in a bore ( 9 ) in the casing ( 8 ), and where fluid may flow to the sleeve ( 16 ) from an inlet ( 11 ) in the casing ( 8 ) and into the sleeve ( 16 ) via the in-valve ( 18 ), and where the sleeve ( 16 ) is provided with at least one perforated area where fluid may flow radially out of or into the sleeve ( 16 ) via holes ( 50, 51 ), thereby flowing to or from a passage ( 14, 15 ) that forms a perpendicular or near perpendicular connection with the bore ( 9 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is the U.S. national stage application of International Application PCT/NO03/00092, filed Mar. 18, 2003, which international application was published on Oct. 2, 2003 as International Publication WO 03/081047. The International Application claims priority of Norwegian Patent Application 20021434, filed Mar. 21, 2002. 
   BACKGROUND OF THE INVENTION 
   The invention regards a valve arrangement for reciprocating machinery such as a pump and a compressor. 
   Reciprocating machinery, or a reciprocating engine, typically has an induction valve and an exhaust valve, hereinafter termed in-valve and out-valve, for each piston. Normally, springloaded one-way valves are used, where a spring closes the valve by forcing a valve body against a valve seat. A valve may be opened for flow either through mechanical action or by pressure in the working medium of the reciprocating engine, hereinafter termed fluid, acting on the valve body to generate a force directed opposite to the force from said spring. 
   If valves of the type in question are arranged so that the direction of flow through the valves is parallel with the cylinder axis of the reciprocating engine, the valves and attached pipework project a relatively long way from the cylinder head of the reciprocating engine. Therefore it is desirable to mount the valves in a manner such that fluid may flow across the cylinder axis immediately outside the cylinder head. If fluid is to flow to and from the cylinder in parallel with the cylinder axis, the direction of fluid flow must change in connection with the valve arrangement. Such a change in direction results in lateral flow forces that act on the valve body and cause misalignment of this. The result is skewed or uneven wear on the valve body and the valve seat, which causes leakage in a closed valve. In the event of such leakage the valve in question must be replaced, or the valve must be disassembled and the worn parts replaced. Changing valves or worn valve components may be time consuming, particularly in the case of large reciprocating machinery such as a reciprocating pump for drill fluid for use in drilling of petroleum wells. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a valve arrangement for reciprocating machinery, where the flow forces cause little or no misalignment of the valve body. It is a further object to simplify the work involved in changing valves. 
   The objects are achieved by the characteristics given in the following description and in the appended claims. 
   According to the invention, two springloaded one-way valves that are known per se, one in-valve and one out-valve, are mounted in a spaced-apart manner in a tubular sleeve, so that the axial direction of flow is the same for both valves. The in-valve is arranged in the sleeve at the first end of this, which forms the inlet end of the sleeve. The out-valve is arranged in the sleeve at the second end of this, the outlet end. 
   The valves divide the sleeve into three chambers; an inlet chamber between the first end of the sleeve and the valve seat of the in-valve, a working chamber between the valve seat of the in-valve and the valve seat of the out-valve, and an outlet chamber between the valve seat of the out-valve and the second end of the sleeve. 
   At the working chamber the sleeve wall is equipped with a first perforated area having through openings for the fluid to flow radially into or out of the sleeve. At the outlet chamber the sleeve wall is equipped with a second perforated area, so as to allow fluid to flow radially out of the sleeves as well. 
   The sleeve with the valves is designed to be installed in a bore in the cylinder head of a reciprocating engine or in a casing that is connected to or forms part of a cylinder head. An external annular gasket at either end of the sleeve and a similar intermediate gasket define two annuli between the sleeve and the bore, the diameter of the bore being enlarged between sealing surfaces against which said gaskets provide a seal. Thus a working annulus is defined between a gasket at the first end of the sleeve and said intermediate gasket. Similarly, an outlet annulus is defined between a gasket at the second end of the sleeve and the intermediate gasket. Advantageously the sleeve has a smaller outside diameter between the gaskets, as this will facilitate the mounting and dismounting of the sleeve. It will also help increase the cross sectional area of the annuli. 
   A first passage in the casing (or the cylinder head) constitutes an inlet for fluid and leads to the first end of the bore, i.e. to the inlet end of the sleeve when the sleeve is installed in the bore. Advantageously the passage is axial with respect to the sleeve and the bore. A second passage in the casing constitutes a working passage and connects said first annulus, the working annulus, with the cylinder of the reciprocating engine. The working passage is typically perpendicular or near perpendicular to the longitudinal axis of the bore. A third passage in the casing forms the outlet for fluid from the second annulus, the outlet annulus. The outlet is typically perpendicular or near perpendicular to the longitudinal axis of the bore. Thus the working passage and the outlet are radially oriented with respect to the bore, and the working passage and the outlet may have different radial orientations. 
   The working annulus is positioned eccentrically with respect to the axis of the bore. The distance between the sleeve and the periphery of the working annulus is at its greatest where the working passage ends, and at its smallest at the diametrically opposite side of the working passage. 
   The outlet annulus exhibits corresponding eccentricity with respect to the axis of the bore. The distance between the sleeve and the periphery of the outlet annulus is at its greatest where the outlet joins the working, and at its smallest at the diametrically opposite side of the outlet. 
   The sleeve is installed in the bore through being inserted into the bore through the second end of this, until it abuts a step in the bore or the bottom of the bore at the first end of the bore, whereupon the second end of the bore is sealed with a cover. The cover may be executed with an abutment that projects into the bore and presses against the second end of the sleeve, keeping the sleeve fixed in the bore. 
   Fluid flows radially between the working chamber of the sleeve and the working annulus outside. The fluid flow is uniformly distributed, so that no lateral forces occur which may misalign the valve body of the in-valve. Similarly, fluid flows out of the outlet chamber to the outlet annulus in a radial and uniformly distributed manner. 
   By the arrangement described, the valves of a reciprocating engine can easily be replaced by dismantling the cover, pulling out the sleeve with the valves, installing a new sleeve with valves and finally fitting the cover. It is also easy to test valves for set pressure and sealing effect in a test installation outside the reciprocating engine, as the sleeve may be arranged in a bore in a casing in which the inlet and the working passage are connected to a pressure source. 
   When a valve arrangement in accordance with the invention is used in a reciprocating engine in which a piston cyclically executes an induction stroke followed by a power stroke, fluid will, upon the induction stroke, flow via the casing inlet to the first end of the sleeve, into the sleeve via the in-valve and radially out of the casing to the working passage and on to the cylinder of the reciprocating engine. On the subsequent power stroke fluid flows from the cylinder via the working passage to the working annulus, and then radially through the first perforated area of the sleeve and into the sleeve, whereupon the fluid then continues axially through the out-valve and then radially out of the sleeve via the openings in the second perforated area to the outlet annulus, and from there to the outlet. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail by means of an example of an embodiment, and reference is made to the attached drawings, in which: 
       FIG. 1  shows a side section of part of a reciprocating engine with a valve arrangement mounted thereon; 
       FIG. 2  shows a side section of a sleeve in the valve arrangement, as well as a side section of a supporting ring, an in-valve with a valve seat and an out-valve with a valve seat; 
       FIG. 2A  shows two cross sections of the sleeve in  FIG. 2 ; 
       FIG. 3  shows a side section of the valve arrangement casing; 
       FIG. 4  shows a cross section of the casing in  FIG. 3 ; 
       FIG. 5  shows another cross section of the casing in  FIG. 3 ; and 
       FIG. 6  is a side view of a cover for the casing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , reference number  1  denotes a valve arrangement mounted on a piston pump  2  and connected to the cylinder  3  of this, in which a reciprocating piston  4  is arranged in a known manner. An assembly plate  5  forms an extension of a flange  6  on the cylinder  3 . The assembly plate  5  and the valve arrangement  1  are attached to the flange  6  and thereby to the cylinder  3  by the use of screws  7 . 
   The valve arrangement  1  comprises a casing  8  in which a bore  9  that is open at one end  10  of the casing  8  ends within the casing  8  and joins an inlet  11  that is open at the other and opposite end of the casing  8 . A cover  13  is designed to cover the bore  9  at the first end  10  of the casing  8 . 
   A working passage  14  in the casing  8  forms an extension of the cylinder  3 , to allow it to communicate with the bore  9 . An outlet  15  leading from the bore and out of the casing  8  is shown in broken lines in  FIG. 1 . The inlet  11  and the outlet  15  are designed to be connected to piping systems (not shown) for incoming and outgoing fluid respectively. 
   In the bore  9  there is arranged a sleeve  16 , the first end of which rests on a supporting ring  17 , which in turn rests on the bottom of the bore  9 . An in-valve  18  is installed in the sleeve  16 , at the first end of this, and an out-valve  19  is installed at the second end of the sleeve  16 . Both the in-valve  18  and the out-valve  19  are springloaded one-way valves, and the valves are mounted so as to open at a predetermined pressure differential acting in the direction from the first end of the sleeve  16  to the second end of the sleeve  16 . 
   Reference is made to  FIG. 2 , which shows the components of the casing  8 , the sleeve  16 , the supporting ring  17 , the in-valve  18  and the out-valve  19  laid out and ready for assembly. Reference is also made to  FIG. 3 , which shows the casing  8 . 
   The sleeve  16  is generally tubular with a circular cross section and a number of internal shoulders for parts that form part of the in-valve  18  and the out-valve  19 , which are both known. 
   The in-valve  18  comprises a valve seat  20 , a valve body  21  designed to move in a valve guide  22 . The valve body  21  is equipped with a sealing element  23 . A valve spring  24  acting between the valve body  21  and the valve guide  22  is designed to force the valve body  21  with the sealing element  23  against the valve seat  20 . The valve seat  20  is designed to receive a centric pin  25  on the valve body  21  in a known manner, thus contributing to the guiding of the valve body  21 . 
   The out-valve  19  similarly comprises a valve seat  26  and a valve body  27  designed to move in a valve guide  28 . The valve body  27  is equipped with a sealing element  29 . A valve spring  30  acting between the valve body  27  and the valve guide  28  is designed to force the valve body  27  with the sealing element  29  against the valve seat  26 . The valve seat  26  is designed to receive a centric pin  31  on the valve body  27  in a known manner, thus contributing to the guiding of the valve body  27 . 
   Approximately half way between the first end  32  and the second end  33  the sleeve  16  is provided with an internal shoulder  34 , where a first annular abutment surface  35  on one side of the shoulder  34  faces the first end  32  of the sleeve  16 , and a second abutment surface  36  on the opposite side of the shoulder  34  faces the second end  33  of the sleeve  16 . 
   The first abutment surface  35  is designed to support the valve guide  22  of the in-valve  18 . The second abutment surface  36  is designed to support the valve seat  26  of the out-valve  19 , which seat is designed with an external collar  37  arranged to rest against the second abutment surface  36 . 
   A third annular abutment surface  38  in the sleeve  16  is designed to support the valve seat  20  of the in-valve  18 . The third abutment surface  38  faces the same direction as the first abutment surface  35 , and is located between the first abutment surface  35  and the first end  32  of the sleeve  16 . 
   Between the first end  32  of the sleeve  16  and the third is abutment surface  38  the sleeve  16  is formed with a cylindrical portion designed to receive the valve seat  20  of the in-valve  18 , and where the wall constitutes the sealing surface for a first annular gasket  40  disposed in a groove in the outer periphery of the valve seat  20 . 
   By the third abutment surface  38  between the second end  33  of the sleeve  16  and the shoulder  34  there is a second internal cylindrical portion  41  designed to receive the valve seat  26  of the out-valve  19 , and where the wall constitutes the sealing surface for a second annular gasket  42  disposed in a groove in the outer periphery of the valve seat  26 . 
   A third internal cylindrical portion  43  is arranged at the second end  33  of the sleeve  16 , which portion  43  is designed to receive a cylindrical stub  44  projecting from the cover  13 , and where the wall constitutes the sealing surface for an annular third gasket  45  fitted in a groove on the stub  44 . The cover  13  with the gasket  45  is shown in  FIG. 6 . 
   A fourth internal cylindrical portion  46  by the first abutment surface  35  is designed to centre the valve guide  22  of the in-valve  18 . 
   A fifth internal cylindrical portion  47  next to the third cylindrical portion  43  for the cover  13  is designed to centre the valve guide  28  of the out-valve  19 . 
   The area between the first and third abutment surfaces  35 ,  38  of the sleeve  16  forms a first sleeve chamber  48  where the wall of the sleeve  16  is perforated with a first set of holes  50 . The area between the second and third cylindrical portions  41 ,  43  of the sleeve  16  forms a second sleeve chamber  49  where the wall of the sleeve  16  is perforated with a second set of holes  51 .  FIG. 2A  shows a section through the perforated wall of the sleeve  16  at the first and second sleeve chambers  48 ,  49 . 
   Reference is made to  FIG. 1  and  FIG. 2 . A fourth annular gasket  52  is disposed in an external groove  53  on the sleeve  16 , by its first end. A fifth annular gasket  54  is disposed in an external groove  55  on the sleeve  16  in an area between the first set of holes  50  and the second set of holes  51 . A sixth annular gasket  56  is disposed in an external groove  57  on the sleeve  16 , in the area at the second end of this. 
     FIG. 3  shows a section through the casing  8  with the bore  9  with axis  58 . The bore  9  consists of areas having different cross sections. At the bottom, the bore  9  is provided with a first cylindrical bore section  59  positioned centrically with respect to the axis  58 , and the wall of the bore  9  forms a sealing surface for the gasket  52  at the first end of the sleeve  16 , see  FIG. 2 . 
   A second cylindrical bore section  60  is positioned eccentrically with respect to the axis  58  and in a way that the bore section  60  is displaced towards the working passage  14 , which ends in the bore section  60 . 
   A third cylindrical bore section  61  is positioned centrically with respect to the axis  58 , and the wall of the bore  9  forms the sealing surface for the gasket  54  of the sleeve  16 , see is  FIG. 2 . 
   A fourth cylindrical bore section  62  is positioned eccentrically with respect to the axis  58  and in a way such that the bore section  62  is displaced towards the outlet  15 , which ends in the bore section  62 . 
   A fifth cylindrical bore section  63  at the free end of the bore  9  is positioned centrically with respect to the axis  58 , and the wall of the bore forms the sealing surface for the gasket  56  of the sleeve  16 , see  FIG. 2 . 
     FIG. 4  shows a cross section of the casing  8  in a plane  25  marked with the letter A in  FIG. 3 , and  FIG. 5  shows a cross section in a plane marked with the letter B in  FIG. 3 . 
   The casing  8  is provided with threaded holes  64  for fixing the casing  8  to the cylinder  3  and to the assembly plate  5  with the screws  7 . Furthermore, the casing  8  is provided with threaded holes  65  for connecting an inlet pipe (not shown) to the casing  8 , so as to allow said inlet pipe to communicate with the inlet  11 . Similarly, the casing  8  is provided with threaded holes (not shown) for connecting an outlet pipe (not shown) to the casing  8 , to allow said outlet pipe to communicate with the outlet  15 . At the free end of the bore  9  the casing  8  is provided with threaded holes  65  for fixing the cover  13  with screws  66 . 
   In order to simplify the installation of the sleeve  16  in the bore  9  and to help avoid damage to the gaskets and sealing surfaces, the first cylindrical section  59  of the bore  9  should have a smaller diameter than the third cylindrical section  61  of the bore  9 , which in turn should have a smaller diameter than the fifth cylindrical section  63  of the bore  9 . 
   The supporting ring  17  and the sleeve  16  with the valves  18 ,  19  are fitted in the bore  9  as shown in  FIG. 1 , and the cover  13  is fitted on the casing  8 , covering the free end of the bore  9 . The stub  44  on the cover  13  projects into the bore  9  and into the sleeve  16 , abutting the valve guide  28  of the out-valve  19  and the second end  33  of the sleeve  16 . Thus the cover  13  forces the sleeve  16  against the supporting ring  17 , which rests against the bottom of the bore  9 . The valve seat  20  of the in-valve  18  is thereby forced against the in-valve body  21 , so as to tension the spring  24 . At the same time, the cover  13  forces the valve guide  28  of the out-valve  19  into the sleeve  16 , so that the valve spring  30  is tensioned against the valve body  27 . 
   When the sleeve  16  with the in-valve  18  and the out-valve  19  is installed in the bore  9  in the casing  8 , as shown in  FIG. 1 , the eccentrically positioned bore sections  60 ,  62  form eccentric annuli outside the sleeve  16 . The largest cross section of the annuli is on the side facing the working passage  14  and the outlet  15  respectively, and the smallest cross section is at the diametrically opposite side of said passages. 
   When the piston pump  2  is operating, fluid at the inlet is transported via the valve arrangement  1  and the cylinder  3  to the outlet  15 , where the fluid is delivered at a higher pressure that of the inlet  11 . The induction stroke of the piston  4  reduces the pressure in the cylinder  3  and thereby also the pressure in the first sleeve chamber  48 , to allow the pressure differential across the valve body  21  of the in-valve  18  to overcome the force from the valve spring  24  and push the valve body  21  away from the valve seat  20 . The out-valve  19  is closed. Fluid flows from the inlet  11  past the valve seat  20 , into the first sleeve chamber  48  and then radially out of the sleeve chamber  48  via the holes  51  to the cylinder  3 . 
   When the piston  4  then executes a power stroke, the in-valve  18  closes and the fluid pressure in the cylinder  3  increases until the pressure differential across the valve body  27  of the out-valve  19  overcomes the force from the valve spring  30 , pushing the valve body  27  away from the valve seat  26  and opening the out-valve  19 . Fluid flows from the cylinder  3  via the holes  50 , radially into the first sleeve chamber  48 , past the valve seat  26  of the out-valve  19  to the second sleeve chamber  49 , and radially out of this via the holes  51  to the outlet  15 . 
   Upon reciprocating movement of the piston  4  the casing  8  and the sleeve  16  are subjected to varying pressure and thereby to a varying load. 
   Thus it can be mentioned that upon the power stroke of the piston  4  the sleeve  16  is subjected to a first axial force against a first annular area defined by the diameter of the sealing surfaces of the first gasket  40  and the fourth gasket  52 , and a second, opposite directed axial force against a second annular area defined by the diameter of the sealing surfaces of the third gasket  45  and the sixth gasket  56 . The sleeve  16  is thereby subjected to an axial tensile force between said annular areas. The dimensions should be selected so as to make the net force, i.e. the difference between the numerical values of the first and second axial forces, push the first end  32  of the sleeve  16  against the supporting ring  17 . The area at the first end  32  of the sleeve  16  is then subjected to a compressive force corresponding to said net force. 
   Upon the induction stroke of the piston  4  only the area between the second gasket  42  and the third/sixth gasket  45 ,  46  is exposed to the operating pressure of the pump  2 . As the force against the valve body  27  of the out-valve  19  is taken up by the sleeve  16 , the area between the second gasket  42  and the third gasket  45  is exposed to tension. The area between the second gasket  42  and the first end  32  of the sleeve  16  is subjected to a compressive force determined by the operating pressure and the diameter of the bore  9  at the sealing surface of the second gasket  42 . 
   The area between the second and third gaskets  42 ,  45  is thereby subjected to a varying tensile force. The area between the first and second gaskets  40 ,  42  alternates between tensile and compressive force. The area between the first gasket  40  and the first end  32  of the sleeve  16  is subjected to a varying compressive force. A person skilled in the art will, based on this, be able to dimension the casing  8 , the supporting ring  8  and the sleeve  16  so as to resist the varying loads.