Abstract:
A method and apparatus for controlling fluid flow with a quarter-turn plug valve with seats operated to lift off the sealing surface of the plug prior to plug rotation and to reseat upon completion of plug rotation. One embodiment shown relates to a quarter-turn rotary plug valve having a handle operable through a 90 ° angle and having both upstream and downstream seats which are operated to lift off from the sealing surface of the plug prior to initiation of plug rotation and then reseat upon completion of plug rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of 35 U.S.C. 111(b) Provisional application Ser. No. 60/162,387 filed Oct. 29, 1999, and entitled Quarter-Turn Rotary Plug Valve with Seats Reciprocable During Operation. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention relates in general to a method and apparatus for controlling fluid flow with a quarter-turn plug valve with seats operated to lift off the sealing surface of the plug prior to plug rotation and to reseat upon completion of plug rotation. More particularly, the invention relates to a quarter-turn rotary ball valve having a handle operable through a 90° angle and having both upstream and downstream seats which are operated to lift off from the sealing surface of the ball prior to initiation of ball rotation and then reseat upon completion of ball rotation. 
     BACKGROUND OF THE INVENTION 
     Certain types of on/off valves have severely attenuated lives due to very concentrated flows with non-axial components during the initial stages of valve opening and final stages of valve closing. In particular, the seats of ball valves and rotary plug valves are susceptible to damage from this type of flow. A second problem which impacts valve actuation is high actuation forces and seat wear due to friction from relative motion of the seats and the sealing plug. This type of problem is common to ball valves, rotary plug valves, and gate valves. 
     Numerous attempts have been made to overcome these problems for on/off valves. For example, valves have been designed to overcome such problems by reciprocably separating the valve seat(s) from the sealing plug (e.g., a ball, plug, or gate) prior to actually moving the sealing plug and reseating the valve seat(s) onto the sealing plug when the sealing plug reaches its new position. Unseating the valve seat during movement permits a considerable reduction in valve operating force and provides a temporary flow path during operation which is less susceptible to abrasive and cavitational wear than valves with standard, non-reciprocating seats. 
     U.S. Pat. No. 3,993,136 to Mott discloses a ball valve with lift-off seats configured for operation as a downhole safety valve. This valve operates by means of a linearly reciprocating hydraulic piston concentric with the flow axis of the valve and operating a mechanism which raises the seats from the ball surface prior to rotation and then reseats the valve seats upon completion of rotation. However, this ball valve is unsuitable for operation either manually or by a conventional 90° actuator. 
     U.S. Pat. No. 4,548,384 to Harding discloses a ball valve which has a stationary downstream seat and an eccentrically-mounted ball as a sealing plug. Valve stem rotation causes the valve plug to lift off of the stationary seat due to the eccentricity between the stem and the ball. The opened ball is then reseated by camming into engagement with the upstream seat. The ball only touches one seat at a time, so that trash buildup within the valve is a major problem. In addition, the valve has limited use as it can only seal in one direction. 
     U.S. Pat. No. 5,179,973 to Dickson et al. discloses another downhole valve operable by a piston reciprocating concentrically with the valve flow axis. This valve causes the ball to lift from its seat due to the applied operating force from the piston during operation when opening, while causing the valve to be pulled against its seat during shifting to its closed position. However, like the Harding valve, it will only hold pressure from one direction. 
     U.S. Pat. No. 5,005,805 to Morris et al. discloses a tapered plug valve which separates the valve plug from its seats by reciprocably lifting the plug about its rotational axis which is transverse to the valve flow axis. The valve plug is rotated after the plug is lifted, and then the valve plug is reseated after completion of rotation. A stem rotation of more than 90° and a special actuator are required to operate this valve. Furthermore, while the transverse reciprocation of the tapered plug causes it to disengage/engage with the seats, the spherical configuration of ball valve sealing surfaces are not compatible with this type of actuation. 
     U.S. Pat. No. 4,989,641 to Jones et al. discloses a rotary selector valve which uses a Geneva-wheel to move a reciprocable seal out of and into engagement with a sealing port. This device requires a complete turn of its rotational shaft to effect a shifting from one port to another and is not suitable for operation with a conventional 90° actuator. 
     U.S. Pat. No. 4,340,088 to Giesow discloses a downhole safety valve with a partial ball valve sealing plug which is operated by a flow axis axially reciprocable piston. The sealing plug both rotates and reciprocates away from its seat during actuation to the open position. The actuation motion is produced by a lost-motion rack-and-pinion device. This valve is only single seated, so that it only holds pressure from one side. 
     European Patent EP 0 647 301 B1 to Coufts et al. discloses a ball valve operable by a piston coaxial with the flow axis of the valve. This valve causes the sealing plug to lift off the seat and then rotate during opening. The valve is not reseated in its open position, so trash buildup is likely. Closing reverses the operation. The valve is only seated for holding pressure from one side. 
     Thus, a need exists for a valve that can seal for pressure from either direction that provides a reduced valve operating force, is less susceptible to abrasive and cavitational wear, and is operable with a conventional 90° actuator or manual rotation. 
     SUMMARY OF THE INVENTION 
     The invention contemplates a valve that preserves the 90° actuation rotation of conventional on/off ball valves while providing the separation of the valve seats from the ball sealing plug prior to and following rotation of the valve plug for actuation. The valve of this invention seals for pressure from either direction by using both upstream and downstream seats. 
     The disclosed valve will reciprocably separate the valve seat(s) from the sealing plug (e.g., a ball or plug) prior to actually moving the sealing plug, move the sealing plug to its new position (a 90° rotation for a ball or plug valve), and reseat the valve seat(s) onto the sealing plug. This unseating/reseating of the valve seats is done for both opening and closing operations. The disclosed valve permits a considerable reduction in valve operating force, even under high pressures, and provides a temporary flow path during operation which is less susceptible to abrasive and cavitational wear than standard, non-reciprocating valves. 
     A preferred embodiment of the invention utilizes a planetary gear train to multiply the rotary actuation shaft motion, while a lost motion coupling between the member driven by the multiplied input shaft motion and the ball permits the driven member to operate a rotary barrel cam to actuate the valve seats prior to ball rotation. Alternatively, any other type of suitable motion-multiplying device, such as shown in U.S. Pat. Nos. 5,312,306 or 5,321,988 and incorporated herein by reference, could be used in place of the planetary gear train. 
     A preferred embodiment of a quarter-turn has a tubular body having a bore flow passage; a valve element having a through flow passage and two sealing surfaces, the valve element rotatable through a quarter turn about an axis transverse to the through flow passage, wherein the through flow passage is aligned with the bore flow passage to permit flow when the valve element is positioned at a first end of the quarter turn and is misaligned with the bore flow passage to prevent flow when the valve element is at a second end of the quarter turn; an actuating valve stem selectively operable through a quarter-turn input motion for effecting opening or closing of said valve element to permit or prevent flow; motion multiplication means operated by rotation of the actuating valve stem; barrel cam means coaxial with the bore flow passage, the cam means engaging the motion multiplication means whereby motion is transmitted to the cam means through a direct-drive coupling; reciprocable seat means providing a seal with the sealing surfaces when in a first position and separated from the sealing surfaces when in a second position, the seat means forced between the first and second positions by movement of the cam means; and lost motion means interposed between the motion multiplication means and the valve element; whereby rotation of the actuating valve stem initiates movement of the cam means to move the seat means into the second position prior to the valve element rotation and then back into the first position upon completion of the valve rotation. 
     The disclosed valve has at least the following advantages over existing valves: (a) the preservation of quarter-turn actuation shaft motion, (b) the ability to seal pressure from either direction, (c) the reduction of operating forces, and (d) the reduction of the erosion of the valve ball and seats when the valve is operated under high differential pressures. The preservation of quarter-turn operation is important for compatibility with standard manual valve operating practice and conventional valve actuators. Use of a ball valve in normal industrial service requires that the valve be able to seal for pressures in either direction, as this valve does. The lift-off of the valve seats from the sealing plug greatly reduces the pressure differential across the valve plug, so that the torque necessary to rotate the valve plug is reduced both by eliminating the frictional drag of the valve seats on the plug and by reducing the pressure drop-induced friction of the sealing plug with its rotational journals. These improvements combine to provide a valve suitable for severe operating conditions, including high pressure and abrasive service. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are believed to be characteristic of the invention, both as to its construction and methods of operation, together with the objects and advantages thereof, will be better understood from the following description taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 shows a side view of one embodiment of a quarter-turn plug valve in the open position; 
     FIG. 2 shows a top view of the quarter-turn plug valve illustrated in FIG. 1; 
     FIG. 3 shows a top view of one embodiment of a quarter-turn plug valve in a partially closed position; 
     FIG. 4 shows a top view of one embodiment of a quarter-turn plug valve in a closed position; 
     FIG. 5 shows a cross-sectional view of the quarter-turn plug valve illustrated in FIG. 1; 
     FIG. 6 shows an exploded side view of the rotating internal components of one embodiment of a quarter-turn plug valve; 
     FIG. 7 is blown-up view of the ball valving element shown in FIG. 5; 
     FIG. 8 shows a side view of a partial cross-section of the quarter-turn plug valve in the open position; 
     FIGS. 9-11 show a series of cross-sections of the quarter-turn plug valve illustrated in FIG. 8; 
     FIG. 12 shows a side view of a partial cross-section of the quarter-turn plug valve in a partially closed position; 
     FIGS. 13-15 show a series of cross-sections of the quarter-turn plug valve illustrated in FIG. 12; 
     FIG. 16 shows a side view of a partial cross-section of the quarter-turn plug valve in a closed position; and 
     FIGS. 17-19 show a series of cross-sections of the quarter-turn plug valve illustrated in FIG.  16 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a valve that reciprocably separates the valve seat(s) from the sealing plug (e.g., a ball or plug) prior to actually moving the sealing plug, moves the sealing plug to its new position (a 90° rotation for a ball valve), and reseats the valve seat(s) onto the sealing plug. This unseating/reseating of the valve seats is done for both opening and closing operations. The valve permits a considerable reduction in valve operating force, even under high pressures, and provides a temporary flow path during operation which is less susceptible to abrasive and cavitational wear than standard, non-reciprocating valves. In addition, the valve can seal for pressure from either direction and is operable with conventional 90° actuation. 
     Referring now to the drawings, it is pointed out that like reference characters designate like or similar parts throughout the drawings. The Figures, or drawings, are not intended to be to scale. For example, purely for the sake of greater clarity in the drawings, wall thickness and spacing are not dimensioned as they actually exist in the assembled embodiment. 
     FIGS. 1 and 2 show a ball valve  10  in an open position. Conventional practice has the handle aligned with the flow passage for the open valve and transverse for the closed valve. The internal parts of valve  10  are housed by generally tubular body  11 . End pieces  12  are engaged into the opposed ends of body  11  and retain the internal parts of valve  10  in place within the body  11 . End pieces  12  are typically threadedly engaged with the body  11  and are threaded to engage with upstream and downstream connections to a piping system. Bonnet  14  is bolted or otherwise engaged with a cylindrical neck  25 . Bonnet  14  serves to support the rotatable valve actuation stem  15 , which is in turn connected to operating handle  16 . 
     FIG. 3 shows valve  10  in a partially open position and FIG. 4 shows valve  10  in a closed position. The operation of the valve as it moves from an open to a closed position will be discussed in more detail below. 
     FIG. 5 is a longitudinal section of the valve  10  in FIG.  2 . Tubular body  11  has a symmetrical through passage  20  and an internal transverse bore  22 . The internal transverse bore  22  has a flat bottom  24  at its extreme end intersection with through passage  20  face. Furthermore, the internal transverse bore  22  intersects through passage  20  at the center of the body  11 . The flat bottom  24  is parallel to the longitudinal axis of body  11 . Cylindrical neck  25  provides an extended housing for transverse bore  22 . At its upper transverse, horizontal end  26 , drilled and tapped bolt holes  27  are provided for bolts  28  to engage the holes  27  and retain bonnet  14 . Transverse cylindrical body extension  29  reinforces the body  11  in the vicinity of transverse bore  22 . 
     The symmetrical through passage  20  is provided with internal threads  21  at its outer ends for engaging end pieces  12 . The end pieces  12  have external threads  34  that threadedly engage the internal threads  21  at the outer ends of body  11 . Annular end pieces  12  have through bores  30  with internal pipe threads  31  at their outer ends for attaching the valve into a piping system. 
     Male O-ring grooves  32  carrying O-rings  33  are positioned to seal between the interior of the body  11  and the exterior surface of end piece  12 . The transverse inner ends  36  of end pieces  12  extend sufficiently into the body  11  to permit shouldering and retaining the reciprocating valve seats. The interior ends of end pieces  12  have a first and second stepped counterbore  37  and  38  respectively. 
     First counterbore  37  provides a cylindrical internal sealing surface for engaging the outer seals of the valve seats  101 . First counterbores  37  further provide cavities with transverse back faces for the mounting of seat biasing springs  39 . Seat biasing springs  39  can be Belleville springs as shown, split or radially fingered Belleville springs, coil springs, or wave springs. Multiple springs in series may also be used in order to provide sufficient travel without overstress. Second counterbores  38  provide clearance for spring-shrouding seat extensions which shield springs  39  from flow through the valve. 
     Handle  16  attaches to valve actuation stem  15  by means of comating coaxial keyways and key  17 . Actuation stem  15  is journaled in the central through bore  41  of bonnet  14 . Female O-ring groove  42 , located in the through bore  41  of bonnet  14 , contains O-ring  43  which seals between the bonnet  14  and the cylindrical surface of actuation stem  15 . 
     Bolt holes  44  through the transverse top flange of bonnet  14  permit insertion of bolts  28  for clamping the bonnet to end  26  of the cylindrical neck  25  of body  11 . The lower outer surface of bonnet  14  extends into transverse bore  22  of valve body  11  and has circumferential male O-ring groove  45  located a short distance above the bottom end of the bonnet. O-ring  46  is located in groove  45  and seals between transverse bore  22  and the lower cylindrical surface of bonnet  14 . 
     As seen in FIG. 7, the bottom end of bonnet  14  is step counterbored coaxially with and is adjacent the through bore at its lower end. The smaller counterbore  47  is used to mount thrust bearing  48 , while the larger counterbore  49  provides clearance for upset head  50  of the actuation stem  15 . The upper surface  51  of the upset head  50  of actuation stem  15  provides a reaction surface which bears on thrust bearing  48 . 
     Turning now to FIGS. 6 and 7, the actuation stem  15  is shown wherein the lower side of the upset head  50  of actuation stem  15  is recessed to form an internal ring gear  52 . A counterbore  53 , coaxial with the actuation stem  15 , is in the center of the lower side of the upset head  50  and provides a journal which supports the upper trunnion end  54  of the ball valving element  58 . Coaxial with and immediately below the upper trunnion end  54  of ball valving element  58  is enlarged shaft section  59  which rotationally supports a lost-motion actuator  70 . The lost motion actuator  70  is supported from below by transverse upper flat  61  of ball valving element  58 . Constant radius slot  60  is positioned in the upper flat  61  of ball valving element  58  and has a 90° arc length. The ends of the radius slot  60  are semicylindrical. Spherical surface  63  of ball valving element  58  serves as the sealing surface of the ball valving element. 
     As seen in FIG. 7, the through bore  64  of ball valving element  58  is transverse to the axis of rotation of the ball valving element provided by upper trunnion end  54  and lower trunnion end  65 . Transverse lower flat  66  is symmetric to upper flat  61  about the axis of through bore  64 . Lower trunnion end  65  is journaled for rotation in a short cylindrical bore coaxial with bore  22  and located in the flat bottom  24 . Lower trunnion end  65  serves as a shaft for idler bevel gear  81 , which bears on lower flat  66 . 
     FIGS. 6 and 7 show the lost motion actuator  70  having a downwardly facing bevel gear  71  rotatable about a central hole  72  which is supported by enlarged shaft section  59  of ball valving element  58 . An annular spur sun gear  74  is fixedly mounted coaxial with central hole  72  onto the upper face of lost motion actuator  70  by brazing or other suitable means. Alternatively, a downward-facing boss could be fabricated on sun gear  74  and could be press-fitted into a suitably sized central hole in lost motion actuator  70  so that rotational support for the assembly is provided through the sun gear  74 . Downwardly projecting cylindrical stub shaft  75  is mounted to the lower face of lost motion actuator  70  and eccentric to the axis of sun gear  74  for the purpose of imparting motion to ball valving element  58  by engaging the semicylindrical ends of constant radius slot  60 . 
     Turning now to FIGS. 6 and 9, planet spur gears  76  are interposed in a plane and engage both internal ring gear  52  and spur sun gear  74  to complete the planetary gear set. Planet gears  76  are mounted on stationary vertical shafts  77 . Shafts  77  have axes transverse to and are mounted to annular plate  78  by press fit or spot welding or other suitable means. Annular plate  78  has a central hole to clear sun gear  74  and is mounted horizontally in a gap between the bottom of upset head  50  of actuation shaft  15  and the upper surface of lost motion actuator  70 . Annular plate  78  has radially projecting diametrically-opposed ears  79  which engage comating rectangular slots  80  cut through the downwardly projecting annular wall formed between the lower outer cylindrical section of bonnet  14  and its larger counterbore  49 . The ears  79  prevent the annular plate  78  from rotating whenever ring gear  52  is rotated. The pitch diameters of ring gear  52 , planet gears  76  and sun gear  74  are chosen such that one turn of ring gear  52  provides two output turns of sun gear  74 . In other words, the planetary gear system is a two-to-one motion multiplier. Alternatively, any other type of suitable motion-multiplying device, such as shown in U.S. Pat. Nos. 5,312,306 or 5,321,988 and incorporated herein by reference, can be used in place of the planetary gear train. 
     Turning now to FIGS. 5 and 7, the spherical sealing surface  63  of the ball valving element  58  provides a sealed surface on each side of the ball valving element  58  where identical annular valve seats  101  are biased toward sealing surfaces  63  by the seat biasing springs  39  when the valve  10  is in an open or a closed position. As the valve is initially turned the valve seats  101  are lifted off the sealing surface  63  by the camming rings  85 . The camming rings  85 , as shown in FIGS. 7 and 9, are identical annular rings with bevel gears  86  facing inwardly toward ball valving element  58  with the teeth of bevel gears  86  meshed with the teeth of downwardly facing bevel gear  71  of lost motion actuator  70  and idler bevel gear  81 . Camming rings  85  are coaxial with the through flow passages  20  of the valve  10 . 
     Camming rings  85 , shown in FIG. 9, are journaled on their inside cylindrical surfaces by the comating exterior cylindrical surfaces of the valve seats  101 . The faces  88  of camming rings  85  are on the opposite ends from bevel gears  86  and are transverse to the axes of the rings, but are provided with detents 180° apart and formed by the tapered side cut-outs  89 . Diametrically opposite tapered side cut-outs  89  on camming rings  85  are mirror-image tapered side cut-outs  90  shown on the top in FIG.  17 . Face  88  together with cut-outs  89  and  90  form a barrel camming surface on the outer end of camming ring  85 . The tapered sides of cut-outs  89  and  90  serve as inclined planes for reciprocating abutting surfaces in the axial direction of the camming rings. The degree of taper for these cut-outs may be adjusted in order to reduce the rotational effort necessary to lift the seats from the spherical surface  63  of ball valving element  58 . 
     As shown in FIGS. 5 and 7, identical valve seats  101  are of annular configuration and are mounted coaxially in through bores  20  of body  11 . As shown in this embodiment of the valve, spherical ends  102  are configured to closely mate to spherical surface  63  of ball valving element  58  for metal-to-metal sealing. Use of other types of seating, such as elastomeric seal rings and the like, may also be used. The largest outer diameters of seats  101  are journaled in bores  20  to permit smooth reciprocation therein. It should be noted here that if the journaled lengths of seats  101  were long enough, idler gear  81 , which meshes with the lower side of bevel gears  86  would not be required for maintaining coaxial stability for camming rings  85 . The reduced outer diameters of seats  101  serve to journal the camming rings  85 . On the outer ends opposite the spherical ends  102  of seats  101  are reduced outer diameter sections. 
     The larger pair of these reduced outer diameter sections is provided with male O-ring grooves  103  containing O-rings  104  which seal between seats  101  and stepped bores  37 . The seats are constrained to seal against the ball valving element  58  when they have pressure acting on their side of the ball valving element, due to the differential area between the larger of the reduced outer diameters and the sealing diameter of seat spherical surfaces  102 . The transverse shoulders between these reduced outer diameters serve as reaction surfaces for seat biasing springs  39 , while the small outer diameter sections protect seat biasing springs  39  from flow. 
     The inward transverse faces  109 , shown in FIGS. 9 and 10, on the ball side of seats  101  are provided with tapered-side bosses  111 . These bosses are configured to comate with tapered-side cutouts  89  and  90  of camming rings  85 . Diametrically opposite tapered-side bosses  111  are identical mirror-image bosses  112 , seen in FIG.  17 . Together with transverse faces  109 , tapered-side bosses  111  and  112  form barrel cams to comate and coact with the mating barrel cams of the camming rings  85 . Keys  108  provided on the bottom sides of seats  101  engage with keyways cut parallel to the valve through axis in the bottom of body  11  so that the seats can freely reciprocate, but cannot rotate. Accordingly, rotation of canning rings  85  causes reciprocation of seats  101  through the interaction of the comating barrel cams of both parts. 
     Operation of the Preferred Embodiment 
     The operation of valve closure from an open position is described by a sequential transition from the open state of FIG. 1 to the closed state shown in FIG.  4 . When the ball is in the open state, the handle is parallel to the flow passage as seen in FIGS. 1 and 8. FIGS. 9-11 show sequential cross-sections of the valve  10  in the open state. As seen in FIG. 9, identical camming rings  85  are positioned between bevel gears  71  and  86  and the valve seats  101 . The faces  88  of the camming rings  85  are provided with detents with tapered side cut-outs  89 . The inward face of the valve seats  101  are provided with tapered-side bosses  111 . These bosses  111  are configured to comate with tapered-side cutouts  89  when the valve is open. 
     Initial rotation of handle  16  causes the planetary gear train to rotate, and in the process to double the input motion transferred to the lost motion actuator  70 . The partially open valve  10  illustrated in FIG. 3 is shown in more detail in FIGS. 12-15. As the lost motion actuator  70  rotates away from its position corresponding to the open valve state, its degree of rotary motion is equally imparted to the bevel-geared seat camming rings  85 . Since valve seats  101  cannot rotate due to keys  108 , camming action between faces  88  and detents  89  and  90  of camming rings  85  and faces  109  and bosses  111  and  112  of valve seats  101  initiates virtually as soon as lost motion actuator  70  begins rotation. 
     In the process of closing, the valve transitions through the intermediate state wherein the seats are cammed off the ball surface and the ball is readied to rotate. This camming occurs as seat tapered side bosses  111  and  112  ramp out of camming ring cam detents  89  and  90  respectively. This camming action forces seat spherical sealing surfaces  102  to separate from spherical sealing surface  63  of ball valving element  58 . Following this separation, the pressure differential across the ball is determined by the flow drop across the annular orifices between the seats  101  and the ball valving element  58 ; this pressure differential will always be less than any non-zero pressure retained by the valve prior to opening. As a result, the frictional force exerted to resist valve rotation by the supporting journals is reduced. Further, the frictional resistance to rotation due to forces exerted on the ball valving element  58  by the pressure-biased seats  101  is reduced to zero. Accordingly, seat separation greatly lowers valve rotational resistance. 
     While the actuation stem  15  is rotated 45° or less from the open position, lost motion occurs between stub shaft  75  mounted on lost motion actuator  70  and the 90° arcuate, constant-radius groove  60  on upper flat  61  of ball  58 . However, further rotation of actuation stem  15  past 45° induces more than 90° of motion to the lost motion actuator, so that stub shaft  75  engages the end of groove  60  and causes the ball valving element to rotate as seen in FIGS. 16-19. At the same time, camming rings  85  are rotating at the same rate as the ball valving element  58 , but remain on a flat portion of the cam until the ball valving element rotation to the closed position is nearly complete. For the last portion of the rotation of actuation stem  15 , the separation of seat sealing surfaces  102  from the valve spherical sealing surface  63  is reduced to zero by camming when seat tapered side bosses  111  and  112  reenter the camming ring detents  89  and  90  while simultaneously the valve is reaching its closed position. The mating of the tapered side bosses and detents when in the valve closed position is diametrically opposed to that when in the valve open position. 
     The operation of the valve in opening from the closed position is not the reverse of the closing operation because of the lost motion between the lost motion actuator and the ball. This lost motion ensures that the seats are lifted from the sealing surface of the ball prior to rotation, whichever direction the valve handle is rotated. The valve rotation always occurs during the second 45° half of the 90° actuation stem rotation. Otherwise, the opening of the valve from its closed position is the reverse of the closing operation. 
     It may be seen from the foregoing description that this valve provides a definite improvement in the operation of ball valves, enabling improvements in pressure capability, service life, and economies in actuators. The valve will perform substantially better in abrasive or cavitating service than conventional valves, due to the avoidance of flow concentration during initial valve opening and final valve closing. A particular advantage is the retention of a 90° actuation motion, since this preserves the same operating pattern for both mechanical and manual operation. Further, it may readily be seen that this same mechanism is directly adaptable to rotary plug valves. It is to be understood that this invention is not limited in its application to the details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purposes of description and should not be regarded as limiting.