Patent Publication Number: US-6220272-B1

Title: In-line control valves

Description:
This is a division of application Ser. No. 09/051,712, filed Jul. 8, 1998, now U.S. Pat. No. 6,029,691, which, in turn, is the national stage of International Application PCT/IL96/00109 filed Sep. 12, 1996. 
    
    
     The present invention relates to valves for controlling the flow of a fluid (liquids or gasses) through a pipe. The invention is particularly useful with respect to the type of in-line control valve described in our prior U.S. Pat. No. 4,681,130, and is therefore described below with respect to that type of control valve. 
     The above-cited patent discloses an in-line control valve which is normally open and which is actuated to a closed position by applying a fluid pressure, e.g., the inlet pressure, to two control chambers within the valve both acting together to produce a combined closing force substantially greater than the opening force produced by the inlet pressure applied to the upstream face of the valve member, thereby better assuring fast and safe closure of the valve against the inlet pressure. 
     An object of the present invention is to provide in-line control valves which may be of similar construction to that of the above-cited patent but which include a number of improvements and variations enabling valves to be constructed for a wide variety of different applications. 
     According to one aspect of the present invention, there is provided an in-line control valve comprising: a housing having an inlet port, an outlet port downstream of the inlet port, and a valve seat between the two ports; and a valve assembly within the housing; the valve assembly including: a valve member movable towards and away from the valve seat and having an upstream face facing the valve seat and a downstream face facing the outlet port; a valve stem fixed to the valve member and extending downstream thereof; a piston head carried by the valve stem at the downstream end thereof and having a downstream face defining a first control chamber with a first surface of the housing; a cylindrical skirt fixed to and extending downstream of the valve member and enclosing the valve stem but terminating short of the piston head to define a second control chamber with the valve member, the valve stem and a second surface of the housing; a fluid flow passageway through the housing to permit fluid flow therethrough in the open condition of the valve member, a pressure-control passageway through the valve stem establishing communication between the first and second control chambers such that the fluid pressure in the first chamber acts on the downstream face of the piston heat tending to move it and the valve member towards the valve seat, and the fluid pressure in the second chamber acts on the upstream face of the valve member and tends to move it and the valve member also towards the valve seat; the upstream face of the piston head and a third surface of the housing defining a third control chamber such that the fluid pressure therein acts on the upstream face of the piston heat tending to move it and the valve member towards the open position of the valve member away from the valve seat; and a control port communicating with the third control chamber for applying fluid therein to move the valve member towards its open position away from the valve seat. 
     According to another aspect of the invention, there is provided a control valve comprising: a housing having an inlet port, an outlet port downstream of the inlet port, and a valve seat between the two ports; and a valve assembly movable within the housing; the valve assembly including a valve member movable towards and away from the valve seat; the valve member having an upstream face facing the valve seat and a downstream face facing the outlet port; the valve seat being of conical configuration increasing in diameter in the downstream direction; the valve member carrying an annular resilient seal engageable with the conical valve seat in the closed position of the valve member; the valve member including an upstream conical valve cover and a downstream valve body of complementary conical configuration; the annular resilient seal including a conical skirt clamped between the conical valve cover and valve body; the annular resilient seal further including a thickened outer periphery having an inner section received within an annular recess formed in the outer periphery of the valve body, and an outer section having an annular face exposed by the conical valve cover for sealing engagement with the conical valve seat. 
     According to a still further aspect of the invention, there is provided an in-line control valve for controlling the flow of a pressurized fluid, comprising: a housing having an inlet port, an outlet port downstream of the inlet port, and a valve seat between the two ports; a valve member movable to open and close positions with respect to the valve seat and having an upstream face facing the valve seat, and a downstream face facing the outlet port; the housing including surfaces defining, with downstream surfaces of the valve member, control chamber means downstream of the valve member; a passageway through the valve member from its upstream face through its downstream face and communicating with the control chamber means such that the inlet pressure of the fluid at the inlet port is applied to the control chamber means to produce a closing force tending to move the valve member to its closed position and opposed to the opening force, tending to move the valve member to its open position, produced by the inlet pressure applied to the upstream face of the valve member; and an actuator for actuating the valve member to its open and closed positions. 
     Further features of the invention will be apparent from the description below. 
     The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
     FIG. 1 is a longitudinal sectional view illustrating one form of normally-open control valve constructed in accordance with the present invention, the valve member being shown in its normally-open position which it assumes in the presence of a fluid inlet pressure; 
     FIG. 2 is a view similar to that of FIG. 1 but illustrating the valve member in its closed position when a control pressure is applied to its control port; 
     FIG. 3 is a similar cross-sectional view as FIG. 2 but along a section line rotated 45° to better show internal structure; 
     FIG. 4 is an enlarged fragmentary view illustrating the construction of the one-way vent of the cushioning chamber in the control valve of FIGS. 1-3; 
     FIG. 5 diagrammatically illustrates a battery of control valves according to FIG.  1  and one manner in which the valves may be controlled. 
     FIG. 6 is a longitudinal sectional view illustrating one form of normally-closed control valve constructed in accordance with the present invention; 
     FIG. 6 a  is a transverse-sectional view along line  6   a — 6   a  of FIG. 6; 
     FIG. 7 is a similar view as FIG. 6 but along a section line rotated 45° to better show internal structure; 
     FIG. 8 illustrates the control valve of FIGS. 6 and 7 in its open condition; 
     FIG. 9 is a longitudinal sectional view illustrating another form of normally-closed control valve constructed in accordance with the present invention; 
     FIG. 10 illustrates the valve of FIG. 9 in its actuated open condition; 
     FIG. 11 is an enlarged fragmentary view more particularly illustrating the construction of the resilient seal in the valve assembly; 
     FIGS. 11 a - 11   c  illustrate various conditions of the resilient seal of FIG. 11; 
     FIG. 12 is a three-dimensional view, partly broken away to show internal structure, illustrating an internal-motor actuated control valve constructed in accordance with the invention; 
     FIG. 13 is a longitudinal sectional view of the control valve of FIG. 12 showing the valve in its closed condition; 
     FIG. 14 is a similar view as FIG. 13, but showing the valve in its open condition; 
     FIG. 15 is a longitudinal sectional view, similar to that of FIG. 14, but taken along a sectional line rotated 45° with respect to that of FIG. 14; 
     FIG. 16 is a longitudinal sectional view illustrating an external-motor actuated control valve constructed in accordance with the invention and showing the valve in its closed condition; and 
     FIG. 17 is a view similar to that of FIG. 16 but showing the valve in its open condition. 
    
    
     The normally-open control valve illustrated in FIGS. 1-4 comprises a housing, generally designated  10 , including an outer cylindrical section  11 , preferably of metal, an inner cylindrical section  12 , preferably of plastic, an inlet coupling duet  13  at the upstream end of the housing, and an outlet coupling duct  14  at the downstream end of the housing. The two coupling ducts  13 ,  14 , also preferably of metal, are of conical configuration and are welded to the outer metal side wall  11 . Flange assemblies  15  reinforce the welded junctures of the two coupling ducts  13 ,  14  to the outer cylindrical section  11 , and seals  16  seal the inner cylindrical section  12  with respect to the coupling ducts  13 ,  14 . 
     The inlet coupling duct  13  includes an inlet port  17  for inletting the fluid into the housing, and the outlet coupling duct  14  includes an outlet port  18  for outletting the fluid. The inlet coupling duct  13  is formed on its inner surface with a conical valve seat  19  cooperable with the valve assembly within the housing for controlling the flow of the fluid from the inlet port  17  to the outlet port  18 . 
     The valve assembly within housing  10  is generally designated  20 . It includes a hydrodynamically-shaped valve member  21 , constituted of a conical valve cover  21   a  and valve body  21   b , securing an annular resilient seal  22  around the outer periphery of the valve cover and movable towards and away from the conical valve seat  19 . Valve member  21  is connected to an actuator which includes a valve stem  23  threadedly attached to valve member  21  and extending downstream thereof. The downstream end of valve stem  23  carries a piston head  24  having a sealing ring  24   a  movable within a cylinder  25 , in the form of a cylindrical liner, within housing section  12 . 
     Valve member  21  is urged to the valve-closed condition illustrated in FIG. 1 by a spring  26  between piston head  24  and a radial wall, defined by a rear cap  27 , at the downstream end of housing  10  adjacent to its outlet port  18 . Cap  27  is of a spider-configuration, being formed with a plurality of radially-extending ribs  27   a  (FIG. 1) to define between them a plurality of axially-extending passageways  27   b  (FIG. 3) to the outlet port  18 . The outer surfaces of ribs  27   a  are shaped complimentarily to the inner conical face  14   a  of the outlet coupling duct  14  such that spring  26  firmly presses cap  27  against coupling duct  14  while the passageways  27   b  between the ribs  27   a  define large axial passageways for the flow of the fluid to the outlet port  18 . 
     Housing section  12  is similarly formed with a plurality of radially-extending ribs  12   a  (FIG. 1) aligned with ribs  27   a  of cap  27  and defining a plurality of axially-extending passageways  12   b  (FIG. 3) aligned with passageways  27   b  of cap  27  for the flow of the fluid through the control valve when the valve assembly  20  is in its open position (FIG.  3 ). 
     Valve assembly  20  further includes a cylindrical skirt  28  integrally formed with body  21   b  of valve member  21  and extending downstream thereof to enclose the respective part of valve stem  23 . Cylindrical skirt  28  is movable within a cylindrical recess  29  formed axially through ribs  12   a  of housing section  12 . The inner surface of cylindrical skirt  28  is sealed with respect to the housing by a sealing ring  30 , whereas the outer surface of the skirt is unsealed and permits the free flow of the fluid through the axial passageways  12   b  in housing section  12 . 
     Valve stem  23  is formed with an upstream section  23   a  enclosed by skirt  28  of valve member  21 , and a downstream section  23   b  adjacent to piston head  24 . The downstream section  23   b  is of larger outer diameter than the upstream section  23   a , to define an annular wall  23   c  between the two sections. The upstream section  23   a  is sealed with respect to the housing by a sealing ring  31 , and the downstream section  23   b  is sealed with respect to the housing by a sealing ring  32 . Sealing rings  30  and  31  are carried by a radially-extending wall  12   c  of housing section  12  and are retained in place by a retainer plate  33  secured thereto by fasteners  34 . 
     It will be seen that the construction of the control valve, insofar as described above, defines several chambers with housing  10 , particularly housing section  12 , as follows: 
     (1) Chamber C 1  is defined by the downstream face of piston head  24 , surface  10   a  of housing cylinder  25 , and the confronting face of cap  27 . As will be described more particularly below, chamber C 1  serves as a first control chamber, and produces a force tending to move valve member  21  from its normally-open position to a closed position when pressurized fluid is applied via a control port CP 1  communicating with chamber C 1  via passageway in one of the housing ribs  12   a . Chamber C 1  includes a drain  35  to the atmosphere, but this drain is plugged so that it is not effective in the normally-open construction of FIGS. 1-3. 
     (2) Chamber C 2  is defined by the downstream face of valve body  21   b  including the inner face of its cylindrical skirt  28 , surface  10   b  (on retainer plate  33  of radial wall  12   c ) of housing section  12 , and the outer surface of valve stem  23 . Chamber C 2  communicates with chamber C 1  via an axial passageway  36   a  and a radial passageway  36   b  in valve stem  23 . Chamber C 2  thus also serves as a control chamber producing a force intensifying that produced in chamber C 1  to move valve member  21  from its normally-open position to its closed position when a control pressure is applied via control port CP 1 . 
     (3) Chamber C 3  is defined by the upstream face of piston head  24 , the adjacent portions of valve stem  23 , and surface  10   c  of housing cylinder  25 . Chamber C 3  communicates with a second control port CP 2  via a passageway in one of the housing ribs  12   a  such that when valve member  21  is closed and pressurized fluid is applied to the control port CP 2 , valve member  21  is moved to its open position, as will be described more particularly below. 
     (4) Chamber C 4  is defined by annular wall  23   c  of valve stem  23  and surface  10   d  on radial wall  12   c  of housing section  12 . Chamber C 4  serves as a cushioning chamber for cushioning the movement of valve member  21  to its final closing position in order to prevent sudden impacting of the valve member against the valve seat  19 . Cushioning chamber C 4  is sealed by sealing ring  32  on valve stem  23  and sealing ring  31  on radial wall  12   c  of the housing. 
     To vent the fluid from cushioning chamber C 4 , valve stem  23  is formed with a small-diameter vent, which includes an axial bore  37  communicating with an annular groove  38 , at a location in piston stem  23  slightly downwardly of its sealing ring  32 . As shown particularly in FIG. 4, annular groove  38  has an inner end  38   a  closed by a sealing ring  39 . The vent so-produced is a one-way vent, permitting fluid flow only from cushioning chambers C 4  in the direction of control port CP 2 . 
     Housing section  12  is further formed with a plurality of axially-extending slots  40  from control port CP 2  but terminating short of radial wall  12   c.    
     As will be described more particularly below, the construction is such that the cushioning chamber C 4  is effective to retard or cushion the closing movement of the valve assembly  20  only at the final movements to its closed position in order to cushion the impact of the valve member  21  against valve seat  19 . The force produced in chamber C 4  is also effective to intensify the final opening movement of the valve assembly. 
     The control valve illustrated in FIGS. 1-4 operates as follows: 
     When the control valve is not connected to the line, or if connected, the line is not yet pressurized, the valve assembly will be in the closed position illustrated in FIG. 2 under the influence of spring  26 . However, when the control valve is connected into the line and the line is pressurized, the inlet pressure is applied to the upstream face of valve member  21 , thereby moving the valve assembly  20  to its open condition as illustrated in FIG.  1 . Thus, the illustrated valve is in a normal open condition when the line is pressurized. 
     In the event of a failure of the inlet pressure, the force applied by the downstream pressure against surface  28   a  of the valve skirt  28 , and also the force applied by spring  26 , move valve assembly  20  to its closed condition (FIG.  1 ), thereby preventing backflow of fluid from the downstream pipe (not shown) via the outlet port  18 , the inlet port  17 , and the upstream pipe (not shown) connected to the inlet port. 
     When it is desired to close the valve, pressurized fluid is applied to control port CP 1 . Normally this is done by using a pilot valve (e.g. pilot valve  45  in FIG. 5) which connects control port CP 1  to the inlet pressure. When this occurs, the inlet pressure is applied to control chamber C 1  and also, via passageway  36   a  and  36   b  through valve stem  23 , to control chamber C 2 . 
     The pressure within control chamber C 1  produces a force against piston head  24  tending to move the valve assembly  20  towards its closed position (i.e., rightwardly in FIG.  3 ), the magnitude of this force being equal to the pressure within chamber C 1  multiplied by the area of the outer diameter (D 1 ) of piston head  24 . The pressure within chamber C 2  produces a force also acting in the direction to move valve assembly  20  towards its closed condition, i.e., boosting the force produced in chamber C 1 . The force produced in chamber C 2 , however, acts on the downstream face of valve member  21  and is of a magnitude corresponding to the inner diameter (D 2 ) of the cylindrical skirt  28 , less the outer diameter (D 3 ) of valve stem section  23   a.    
     When the valve assembly is in its open condition as illustrated in FIG. 1, the force acting to maintain the valve assembly in its open condition is equal to the inlet pressure multiplied by the area corresponding to the outer diameter (D 4 ) of the cylindrical sleeve  28 . This force acting to maintain the valve open is less than the sum of the forces produced by the pressure applied via control port CP 1  to chambers C 1  and C 2 , and by the downstream pressure applied to surface  28   a  of skirt  28 , all acting to close the valve assembly. Therefore the valve assembly, will start to move towards its closed condition. 
     During the initial movement of the valve assembly  20  towards its closed condition, chamber C 4  communicates with the atmosphere via slots  40  and control port CP 2  so that there is no buildup of pressure within chamber C 4  which may retard the movement of the valve assembly towards its closed position. As the valve assembly approaches its closed position, wherein its seal  32  passes the end (right end) of slots  40 , chamber C 4  becomes a sealed chamber and therefore acts to cushion the closing movements of the valve assembly. The degree of cushioning, particularly when controlling the flow of a liquid (non-compressible) depends on the flow-rate allowed by venting bore  37  and annular groove  38 . 
     Surface  28   a  of skirt  28  also acts to cushion the final closing movement of the valve assembly. As indicated earlier, the downstream pressure acts against skirt surface  28   a in the direction tending to move the valve assembly to its closed position. As the valve assembly approaches its closed position, the differential pressure across the valve assembly increase, because of the higher flow resistance, thereby reducing the outlet pressure applied to skirt surface  28   a  as the valve assembly approaches its final closing position. 
     Reopening of the control valve may be effected by merely discontinuing the pressure to the control port CP 1 , in which case the inlet pressure applied to valve member  21  will move the valve assembly to the open position illustrated in FIG.  1 . 
     The valve may also be reopened by discontinuing the pressure to control port CP 1 , and applying pressure to control port CP 2 . When this is done, the pressurized fluid within chamber C 3  produces an opening force against the upstream face of piston head  24 , which, together with the opening force produced by the inlet pressure against valve member  21 , moves the valve assembly to its open condition as illustrated in FIG.  3 . 
     Control port CP 2  may be used alone to reopen the valve when the inlet pressure is low or when a vacuum is applied to the inlet. This control port may also be used, together with control port CP 1 , to regulate or dampen the movements of the valve assembly. 
     When the valve is closed and pressurized fluid is applied to control port CP 2  to open the valve, sealing ring  39  prevents this pressurized fluid from passing through the venting bore  37  and annular groove  38  into the cushioning chamber C 4 . Thus, at the start of valve opening only the surface area of chamber C 3  (defined by diameter D 1  minus D 5 ), together with the inlet pressure applied to the valve member  21 , is effective to open the valve assembly. However, as soon as seal  32  of valve stem  23  passes the right end of slots  40 , the pressure within chamber C 3  is also applied to chamber C 4 , thereby increasing the opening force. 
     The pressure of sealing ring  39  also permits a battery of valves to be selectively controlled in a simpler manner when the valves are all closed. Thus, as shown in FIG. 5, a battery of valves  41 - 43  connected in parallel to a common supply pipe  44  may be individually controlled by a separate pilot valve  45 - 47  each connected to the control port CP 1  of its respective valve, and a common pilot valve  48  connected to the control port CP 2  of all the valves. Thus, by applying pressure (e.g., the inlet pressure) to all the control ports CP 2  via the common pilot valve  48 , each of the valves  41 - 43  may be selectively closed, with respect to the downstream pipe  49 , by discontinuing the application of pressurized fluid to the respective control port CP 1  via the respective pilot valve  45 - 47 . 
     FIGS. 6-8 illustrate a valve of generally the same construction as that described above with respect to FIGS. 1-4, but including several modifications to make it a normally-closed valve (when the inlet pressure is applied to it), rather than a normally-open valve as in the construction of FIG. 1-4. An important advantage of a normally-closed valve is that it provides a fail-safe closure of the valve should there be a failure of the control pressure system. To facilitate understanding, those elements which are generally the same as in the valve of FIGS. 1-4 are identified by the same reference numerals. 
     One change in the construction is that the normally-closed valve of FIGS. 6-8 is formed with axial passageway  50  through its valve member  21  establishing communication with axial passageway  36   a  in the valve stem such that the inlet pressure is also applied to chamber C 1  acting on the downstream face of the piston head  24 , and to chamber C 2  acting on the downstream face of the valve body  21   b , both producing forces tending to move the valve assembly  20  to its closed condition as illustrated in FIGS. 6 and 7. Another change is that is does not require the control port CP 1  through the housing section  12  communicating with chambers C 1  and C 2 , and therefore control port CP 1  is plugged, leaving a single control port CP 2  communicating with chamber C 3 . A further change is that chamber C 3  is in continuous communication with chamber C 4  via slot  40  and a bore  51  of larger diameter than venting bore  37  in the FIGS. 1-3 construction, the sealing rings  32  and  39  of the FIGS. 1-3 construction also be omitted. 
     The FIGS. 6-8 construction includes a piston  52  formed with a plurality of radially-extending mounting tabs  53  spaced around its circumference for mounting to the downstream end of piston  24 . Piston  52  is closed at its upstream end by end wall  55 . Its downstream end is slidably received within a cylindrical cavity  56  in cap  27  and includes a sealing ring  56   a  to thereby define a further chamber C 5 . The latter chamber includes the spring  26  and is vented to the atmosphere via drain  35 . Therefore, drain  35  in the FIGS. 6-8 construction is not plugged as it is in the FIGS. 1-3 construction. 
     End wall  55  of piston  52  is spaced from axial passageway  36   a  through the valve stem  23  so as not to block this axial passageway. This space  57  communicates with chamber C 1  via the spaces  58  (FIGS. 6 a ,  7 ) between the mounting tabs  53 . Thus, the inlet pressure is applied to chamber C 1  via axial passageways  50  and  36   a , and spaces  57  and  58 . As in the FIGS. 1-3 construction, the pressure produced in chamber C 1  is also applied to chamber C 2 , and the forces produced in both chambers tend to close the valve as opposed to the force produced by the inlet pressure against valve member  21  tending to open the valve. As distinguished from the construction in FIGS. 1-3, however, the closing force produced in chamber C 1  is reduced by the outer cross-sectional area of piston  52  (since chamber C 5  is vented to the atmosphere). The closing force is opposed by the opening force produced in chambers C 3  and C 4  when a control pressure is applied via control port CP 2 . 
     When the control valve illustrated in FIGS. 6-8 is connected to a water supply pipe, the inlet pressure is applied to the upstream face of valve member  21 , thereby producing a force tending to open the valve. However, the inlet pressure is also applied via passageways  50  and  36   a  to chamber C 1 , and via passageway  36   b  to chamber C 2 , both producing forces tending to close the valve. The latter forces, together with the force produced by the downstream pressure (when the valve is not closed) against surface  28   a , and the force produced by spring  26 , are sufficiently greater than the opening force so that the valve is in a normally-closed condition as illustrated in FIG.  6 . 
     When the valve of FIGS. 6-8 is to be opened, a control pressure (e.g., the inlet pressure) is applied to control port CP 2 . This control pressure is applied to both chambers C 3  and C 4  (the latter being via slots  40  and bore  51 ), producing an opening force, which, together with the opening force applied by the inlet pressure against the upstream face of valve member  21 , is sufficient to move the valve assembly to its open condition as illustrated in FIG.  8 . When the pressure is removed from control port CP 2 , the valve will return to its normally closed condition. 
     In all other respects, the control valve illustrated in FIGS. 6-8 is constructed and operates in substantially the same manner as described above. 
     FIGS. 9 and 10 illustrate a normally-closed valve construction similar to that of FIGS. 6-8. In this case, however, the axial passageways  50  through valve member  21  and its valve stem  23  extends via axial passageway  36   a  to chamber C 5  between the downstream end of valve stem  23  and the rear cap  27 . Whereas in the construction of FIGS. 6-8 chamber C 5  is vented to the atmosphere, in the construction of FIGS. 9 and 10 chamber C 5  is not so vented, but rather is sealed by a sealing ring  60  between the outer surface of the downstream end of valve stem  23  and the inner surface of cavity  61  in the rear cap  27 . In this construction, therefore, drain  35  (FIG. 8) is plugged, but control port CP 1  (e.g., FIG. 1) is vented to the atmosphere. 
     Also, the outer surface of valve skirt  28  carries a sealing ring  62 , and the surface of housing section  12  formed with annular recess  29  for the valve skirt is formed with a plurality of axially-extending slots  63 , thereby establishing communication between chambers C 6  and C 2 . 
     It will be seen that in the construction of FIGS. 9 and 10, the inlet pressure applied to the upstream face of valve member  21  produces an opening force which is substantially balanced by the sum of the closing forces produced by the inlet pressure in chambers C 5 , C 2  and C 6 . The closing force produced by spring  26  will, therefore, be sufficient to move the valve assembly to its normally closed condition. 
     When it is desired to open the valve, a control pressure is applied to control port CP 2  (FIG.  8 ), this usually being the inlet pressure. When pressure is applied to port CP 2 , an opening force is produced in chambers C 3  and C 4 , which, when added to the opening force produced by the inlet pressure against the upstream face of valve member  21 , is sufficient to open the valve. 
     In all other respects, the normally-closed valve illustrated in FIGS. 9 and 10 may be constructed and operated in substantially the same manner as described above with respect to FIGS. 6-8. 
     FIG. 11 illustrates a preferred construction that may be used in any of the above-described control valves for the valve member  21  and its annular resilient seal  22  engageable with the conical seat  19  of the inlet coupling duct  13 . FIG. 11 a  illustrates the annular resilient seal in its initial closing position; FIG. 11 b  illustrates it in its final closing position, and FIG. 11 c  schematically illustrates how the valve member substantially eliminates the chattering phenomenon. 
     The annular resilient seal, generally designated  22  in FIG. 11, includes a conical skirt  70  formed with a thickened outer periphery  71  which engages the conical valve seat  19  in the closed condition of the valve assembly. The conical skirt  70  is clamped by a bolt  72  between the conical valve cover  21   a  on the upstream side, and the valve body  21   b  on the downstream side bearing against an abutment ring  73 , and is of complementary conical configuration as these two parts of valve member  21 . 
     The upstream face of valve body  21   b  is formed with an annular slot  75  receiving the downstream face of the thickened annular periphery  71  of the resilient seal  22 . Slot  75  is of trapezoidal cross-section, being formed with a bottom face  75   a  substantially parallel to the upstream face of conical valve member  21 , and opposed side faces  75   b ,  75   c  substantially parallel to the longitudinal axis of the valve assembly  20 . 
     An anchoring member  77  is received within slot  75  and is of complementary configuration to that slot. In addition, it is formed with an annular dovetail rib  76  received within a complementary dovetail groove  78  formed in the downstream face of the thickened annular periphery  71  of the sealing ring  22 . 
     The upstream face of the thickened outer periphery  71  of sealing ring  22  is formed with an outer annular section  79  of tapering thickness, the thickness decreasing in the outward direction. Annular section  79  is defined by an inner annular wall  79   a  at an obtuse angle to the upstream face of the conical valve member  21 , and an outer annular wall  79   b  at a smaller obtuse angle to the upstream face of the conical valve member  21 . The outer face  79   c  of annular section  79 , which comes into sealing contact with the conical valve seat  19 , is of a curved configuration. 
     The outer end of the valve cover  21   a  terminates at face  79   a  of the resilient seal  22  and is of complementary configuration to that face. The outer end of the outer annular section  79  of the resilient seal  22 , as defined by face  79   b , is normally spaced from face  21   c  at the outer end of the valve body  21   b.    
     As the valve member  21  approaches the conical valve seat  19 , face  79   c  of the resilient seal  22  first engages the conical seat  19  (FIG. 11 a ), and this section of the resilient seal is deformed against face  21   c  of valve body  21   b  in the final closing position (FIG. 11 b ) of the valve member  12 . Thus, as shown in FIG. 11 b  face  79   b  of the resilient seal  22  is pressed against face  21   c  of valve body  21   b  to produce a firm seal with respect to conical seat  19  in the closed position of the valve. 
     The construction of the valve seal  22  as illustrated in FIG. 11 has been found to firmly secure the seal  22  to valve member  21  against very high forces tending to unseat the seal from the valve member, particularly in the event of a reverse flow of the fluid through the valve. Also, as shown particularly in FIG. 11 c , the outer periphery of seal  22  is sufficiently flexible such that, when the valve is only slightly open, this outer periphery oscillates by the flow, with respect to conical valve seat  19  to effect regulation of the flow. Such a construction has also been found to substantially eliminate chattering as the valve member approaches its final closing position. 
     The in-line control valve illustrated in FIGS. 12-14 comprise a housing, generally designated  110 , having a main cylindrical section  112 , an inlet coupling duct  113  at the upstream end, and an outlet coupling duct  114  at the downstream end. The two coupling ducts  113 ,  114  are of conical configuration and are secured to the main housing section  112  by a pair of threaded coupling steps  115 ,  116 . 
     Inlet coupling duct  113  includes an inlet port  117 , and outlet coupling duct  114  includes an outlet port  118 . Inlet coupling duct  113  is formed on its inner surface with a conical valve seat  119  cooperable with the valve member, generally designated  120 , for controlling the flow of the fluid from inlet port  117  to outlet port  118 . 
     Valve member  120  is hydrodynamically shaped. It includes a conical valve cover  121  and an annular resilient seat  122  around its outer periphery movable towards and away from conical valve seat  119 . Valve member  120  further includes a stem  123  threadedly attached to the downstream face of valve cover  121 , and a valve body  124  at the downstream face of the valve cover  121 . Valve body  124  is engageable with an abutting ring  125  such that when stem  123  is threadedly attached to valve cover  121 , the resilient annular seal  122  is firmly clamped between the valve cover  121  and the valve body  124 . 
     Valve stem  123  extends downstream of valve cover  121  and is received within a cylindrical cavity  126  formed in cap  127  engaging the outlet coupling duct  114  and constituting a rear wall of housing  110 . 
     Valve member  120  further includes a cylindrical skirt  128  integrally formed with valve body  124  and extending downstream of the valve member. Cylindrical skirt  128  is received within a cylindrical slot  129  formed axially in housing  112 . 
     Housing  112  includes a radially-extending wall  130  at the upstream end of cylindrical recess  129 . Wall  130  is formed with a central opening for receiving the valve stem  123 . 
     The main housing section  112  is formed with a plurality of radially-extending ribs  112   a  (FIGS. 13,  14 ) circumferentially-spaced from each other to define axially-extending passageways  112   b  (FIG.  15 ). Cap  127  is similarly formed with a plurality of radially-extending spider arms  127   a  circumferentially spaced with each other to define passageways  127   b . Spider arms  127   a  of cap  127  are aligned with radial ribs  112   a  of housing  112  so that the axial passageways  112   b  through the housing and  127   b  through the cap are aligned with each other to permit the fluid flow from the inlet port  117  to the outlet port  118  when the valve member  120  is in its open position. The inner surface of the outlet coupling duct  114  is of conical shape, and the outer surface of the spider arms  127   b  are of complementary conical shape as shown at  127   c , so that the spider arms firmly engage the outlet coupling duct  114  just upstream of the outlet port  118 . 
     The illustrated control valve includes the following seals: sealing rings  131  and  132  between the housing  112  and its inlet coupling duct  113  and outlet coupling duct  114 , respectively, sealing ring  133  between housing wall  130  and valve stem  123 ; sealing ring  134  between cap  127  and valve stem  123 ; sealing ring  135  between cap  127  and housing section  112 ; and sealing ring  136  between the outer surface of valve skirt  128  and the corresponding surface of housing section  112  formed with slot  129  receiving the valve skirt. 
     The foregoing seals define the following chambers: (1) control chamber C 1  between the downstream face  123   a  of valve stem  123  and the walls of the cylindrical cavity  126  formed in cap  127 ; (2) control chamber C 2  defined by the downstream face of valve body  124 , the inner face of valve skirt  128 , the upstream face of housing wall  130 , and the portion of valve stem  123  between housing wall  130  and valve body  124  and enclosed by valve skirt  128 ; (3) control chamber C 3  defined by the downstream face  128   a  of valve skirt  128  and the walls of cylindrical slot  129  formed in housing section  112 ; and (4) a chamber C 4  defined by the inner surface of housing section  112 , the downstream face of its radial wall  130 , the upstream face of its cap  127 , and the outer surface of valve stem  123  between wall  130  and cap  127 . 
     An axial passageway  140  is formed through valve member  120 , including its cover  121 , valve body  124 , and valve stem  123 , leading to chamber C 1  at the downstream end of the valve stem. The inlet pressure is thus applied via axial passageway  140  to control chamber C 1  producing a first force in the direction to move valve member  20  to its closed position. 
     A radial passageway  141  is formed through valve stem  123  leading from axial passageway  140  to chamber C 2 . Thus, the inlet pressure applied via axial passageway  140  to chamber C 1  is also applied via radial passageway  141  to chamber C 2 , to produce a second force acting in the same direction as that produced in chamber C 1  to move valve member  120  to its closed position. 
     Chamber C 3  is connected to chamber C 2  by means of a plurality of longitudinally-extending slots  142  formed in housing section  112  along the inner face of valve skirt  128 . Thus, the inlet pressure applied to chamber C 2  is also applied via slots  142  to chamber C 3  to produce a third force, acting in the same direction as those produced in chambers C 1  and C 2 , to move valve member  120  to its closed position. 
     Chamber C 4  is vented to the atmosphere via a vent  143  formed through one of the ribs  112   a  in the main housing section  112 . Therefore, it does not produce a force applied to the valve member. 
     Chamber C 4 , however, includes an actuator for actuating the valve member to either its open position or its closed position. In the example illustrated in FIGS. 12-14, the actuator, generally designated  150 , is in the form of an electrical rotary motor formed on its inner surface with thread  151  mating with threads  152  formed on the outer surface of valve stem  123  such that, when motor  150  is rotated, stem  123 , and thereby valve member  121 , are moved either to the open position or to the closed position, depending on the direction of rotation of the motor. 
     The valve illustrated in FIGS. 12-14 operates as follows: Assuming the valve member is in its closed position, as illustrated in FIGS. 12 and 13, when the inlet pressure is applied to the inlet duct  117 , the inlet pressure will produce an opening force equal to the inlet pressure multiplied by the surface area of the upstream face of valve member  120 . 
     On the other hand, the inlet pressure is also applied (1) via axial passageway  140  to control chamber C 1 , (2) via radial passageway  141  to control chamber C 2 , and (3) via slots  142  to control chamber C 3 . Therefore, a first force will be produced in control chamber C 1  equal to the inlet pressure multiplied by the surface area of downstream face  123   a  of valve stem  123 ; a second force will be produced in chamber C 2  equal to the inlet pressure multiplied by the surface area defined by the inner surface of skirt  128  and the outer surface of valve stem  123 ; and a third force will be produced in chamber C 3  equal to the inlet pressure multiplied by the surface area of downstream face  128   a  of skirt  128 . As can be seen in FIG. 13, for example, the sum of the effective surface areas in chambers C 1 , C 2  and C 3 , are substantially equal to the surface area at the upstream face of valve member  120 , so that the closing forces produced in the three control chambers will be substantially equal to, and will balance, the opening force produced at the inlet face of valve member  120 . 
     Accordingly, the valve will be open and closed only by the operation of the actuator  150 . Because of the foregoing balance of forces, the operation of actuator  150  will require relatively little energy to move the valve member  120  either to its closed position (FIGS. 12,  13 ) or to its open position (FIGS. 14,  15 ). 
     FIGS. 16 and 17 illustrate a valve constructed substantially as described above with respect to FIGS. 12-15, and therefore the same reference numerals have been used to identify corresponding parts. The main difference in the valve illustrated in FIGS. 16 and 17 is that, instead of being actuated by an internal electric motor, it is actuated by an external electric motor having a mechanical coupling extending through the valve housing to the valve member. 
     Thus, as shown in FIGS. 16 and 17, the rotary drive within chamber C 4  is in the form of a gear unit  160  having internal threads  161  mating with external threads  162  formed in valve stem  123 . Gear  160  is in turn formed with bevel teeth  163  meshing with a bevel gear  164  in chamber C 4  and coupled by a drive shaft  165  extending through housing section  112  and driven by an electrical motor  166  externally of the housing. Gear  160  may be further supported for rotation by a rotary bearings  167 ,  168  between the outer surface of gear  160  and corresponding surfaces of the housing section  112 . 
     In all other respects, the control valve illustrated in FIGS. 16 and 17 is constructed and operates in substantially the same manner as described above with respect to FIGS. 12-15. Thus, as described above, the inlet pressure applied to chambers C 1 , C 2  and C 3  all act in the same direction to produce a closing force balancing the opening force produced by the inlet pressure applied to the upstream face of valve member  120 , such that little energy is required by the electric motor  166  to move the valve member either to its open position or to its closed position. 
     While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many variations may be made. For example, the valve seal construction illustrated in FIG. 11 may be used in any one of the in-line valve constructions described herein, but also in other valve constructions. Many other modifications and applications of the invention will be apparent.