Abstract:
A high torque rotating actuator is disclosed. The high torque rotating actuator has a variable helix angle that allows the actuator to generate greater torque near the end of its travel when it is needed to close a valve or operate a choke. The high torque rotating actuator is designed for use with valves and chokes. In a second embodiment, a high torque rotating actuator is configured to give a shorter overall assembly. As in the preferred embodiment, a variable helix angle is used to generate greater torque near the end of its travel when it is needed to close a valve or operate a choke.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a rotating actuator for use with valves and chokes that features a driving member with a variable helix angle. This variable helix angle allows the actuator to generate greater torque near the end of its travel when it is needed to close a valve or operate a choke. The high torque rotating actuator lends itself to use with a subsea drilling and production system used in offshore oil and gas wells. This system uses an extension spool between the standard wellhead and production flow package. Flow control valves are positioned in the extension spool. These valves are ball type valves requiring a 90 degree rotation of the valve between the open and closed positions. Since these valves are being used subsea at water depths beyond the access of divers, remote actuation of the valves is required. The high torque rotating actuator of the present invention allows remote operation of the valve and provides additional torque required to operate the valve when it is needed most. 
     2. Description of the Related Art 
     U.S. Pat. No. 4,925,154 to G. S. Baker shows a gate valve with a supplemental actuator. The supplemental actuator uses a series of roller cams with the actuator spring to increase the closing force of the actuator during the last portion of its stroke. 
     A helically shaped cam for operating a gate valve is shown in the brochure entitled “The Cameron ½ 10,000 psi WP Half-Turn Manual Gate Valve”. The assignee of the current invention manufactures and sells this valve. 
     SUMMARY OF THE INVENTION 
     This invention relates to a rotating actuator for use with valves and chokes that features a driving member with a variable helix angle. This variable helix angle allows the actuator to generate greater torque near the end of its travel when it is needed to close a valve or operate a choke. The high torque rotating actuator is designed for use with valves and chokes and includes a generally cylindrical housing with a valve actuation stem centrally located within the housing. A cylindrical drive bushing has a plurality of helical grooves formed on its exterior and is internally splined to mate with matching splines on the exterior of the stem. An intermediate head is axially adjacent the drive bushing with a central bore through which the stem extends and includes a plurality of longitudinal grooves on its exterior. An annular piston is between the drive bushing and housing. The annular piston is reciprocable within the housing by hydraulic pressure with a series of belleville springs providing a fail safe close power source. The helical grooves on the exterior of the drive bushing have a variable helix angle to provide a greater torque to the stem at the end of the belleville springs travel. The annular piston has two sets of cam rollers on its interior. One set engages the helical grooves of the drive bushing and the second set engages the longitudinal grooves in the intermediate head. When the annular piston is reciprocated by hydraulic force or spring force, the axial motion of the piston is converted to rotary motion by virtue of the helical grooves in the drive bushing. The stem includes an end configuration to mate with a valve and choke and impart the stems rotary motion to the valve or choke. 
     In a second embodiment, the high torque rotary actuator is configured with the drive bushing inside the intermediate head to give a shorter overall configuration. As in the preferred embodiment, the high torque rotary actuator includes a generally cylindrical housing with a stem coaxially positioned within the housing. The drive bushing is axially adjacent the stem and includes a bore for receiving the stem. An intermediate head is annularly positioned between the drive bushing and the housing with the intermediate head including a plurality of longitudinal grooves. A pressure responsive piston is formed on the stem with the piston reciprocable within a bore formed in the intermediate housing. The drive bushing includes a plurality of helical grooves with a variable helix angle. The stem has two sets of cam rollers on its end. One set engages the helical grooves of the drive bushing and the second set engages the longitudinal grooves in the intermediate head. When the piston is reciprocated by hydraulic force or spring force, the axial motion of the piston is converted to rotary motion by virtue of the helical grooves in the drive bushing. The stem includes an end configuration to mate with a valve or choke and impart the stems rotary motion to the valve or choke. 
     A principal object of the present invention is to provide a high torque rotating actuator that can generate a higher output torque nearer the ends of its travel than at the beginning. 
     Another object of the present invention is to provide a high torque rotating actuator that is compact and can be used on tightly spaced subsea tree valve configurations. 
     A final object of the present invention is to provide a high torque rotating actuator that can be used with valves or chokes. 
     These with other objects and advantages of the present invention are pointed out with specificness in the claims annexed hereto and form a part of this disclosure. A full and complete understanding of the invention may be had by reference to the accompanying drawings and description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention are set forth below and further made clear by reference to the drawings, wherein: 
     FIG. 1 is an isometric view of an extension spool used in subsea oil and gas drilling operations with high torque rotating actuators of the present invention installed. 
     FIG. 2 is an isometric view of the high torque rotating actuator removed from an extension spool. 
     FIGS. 3A-3D are a sectional view of the high torque rotating actuator connected to a ball valve in the open position. 
     FIGS. 4A-4D are a sectional view of the high torque rotating actuator connected to a ball valve in the closed position. 
     FIG. 5 is a sectional view taken along lines  5 — 5  of FIG. 3 showing the details of the release rods and intermediate head. 
     FIG. 6 is a sectional view taken along lines  6 — 6  of FIG. 3 showing the details of the release rods and intermediate head. 
     FIG. 7 is an isometric view of the drive bushing showing the variable helix angle grooves. 
     FIG. 8 is a sectional view of the second embodiment of the high torque rotating actuator with the piston in the open position. 
     FIG. 9 is a sectional view of the second embodiment of the high torque rotating actuator with the piston in the closed position. 
     FIG. 10 is an isometric view of the drive bushing of the second embodiment of the high torque rotating actuator showing the variable helix angle grooves. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, and particularly to FIG. 1, high torque rotating actuators  10  of the present invention installed on extension spool  12  are shown in an isometric view. Extension spool  12  is a thick walled tubular member with lower clamp hub end connection  14  and upper clamp hub end connection  16  as shown. In its typical intended use, extension spool  12  would be connected to a wellhead body (not shown) with lower clamp hub end connection  14 . Pressure controlling ball valves, not shown, are positioned within extension spool  12 . The opening and dosing of these ball valves is done by high torque rotating actuators  10  positioned on the exterior of extension spool  12 . 
     FIG. 2 is an enlarged isometric view of high torque rotating actuator  10  removed from extension spool  12  to show its overall construction. High torque rotating actuator  10  includes housing  18 , intermediate head  20 , lower head  22 , release rods  24  and release cap  26 . Lower head end flange  28  provides a means for connecting high torque rotating actuator  10  to extension spool  12 . 
     FIGS. 3A-3D are a sectional view of high torque rotating actuator  10  attached to extension spool  12 . Referring to FIG. 3A, extension spool  12  is shown partially in section with vertical well bore  30  extending therethrough. Cartridge ball valve assembly  32  is positioned in vertical well bore  30 . Cartridge ball valve assembly  32  has vertical bore  34  therethrough with ball  36  positioned therein in the open position allowing flow through vertical bore  34 . High torque rotating actuator  10  is secured to extension spool  12  by bolts  38  and flange  40  formed on the end of lower head  22 . Seal ring  42  seals the connection between flange  40  and extension spool  12 . Stem  44  of high torque rotating actuator  10  extends from lower head  22  and has a keyed end connection  46  to transmit the torque generated by the rotation of stem  44  by high torque rotating actuator  10  in a manner to be described hereinafter. Keyed end connection  46  engages valve stem  48  which in turn is splined to ball  36  to allow rotation of ball  36 . Bearing sleeve  50  is retained on stem  44  by ball bearings  52  which are installed through port  54 . Ball bearings  52  allow stem  44  to rotate within bearing sleeve  50  which extends into cartridge valve assembly  32  and retains cartridge valve assembly  32  in well bore  30 . 
     Referring to FIGS. 3B-3D, intermediate head  56  is a generally cylindrical member with upper flange  58  and end flange  60  formed thereon. Retainer ring halves  62 , which are L shaped in cross section, secures intermediate head  56  to lower head  22  with studs  64  and nuts  66 . Seal recess  68  is formed in the end of lower head  22  with seal element  70  positioned to seal between lower head  22  and stem  44 . Upper flange  58  of intermediate head  56  is shaped to receive housing  18  in close fitting engagement. Retainer ring segments  72  secure housing  18  to upper flange  58  and seal element  74  seals the annulus therebetween. Intermediate head  56  includes a plurality of longitudinal slots  76  formed on its exterior for purposes to be explained hereinafter. The opposite end of intermediate head  56  includes seal element  78  on its exterior sealing against annular piston  80 . Thrust bearing assembly  82  is positioned in recess  84  on the end of intermediate head  56 . 
     Annular piston  80  has end flange  86  formed on one end that fits closely within bore  88  of housing  18  and the exterior of intermediate head  56 . Seal element  90  seals the annulus between end flange  86  of annular piston  80  and bore  88  of housing  18 . End flange  86  receives a radially disposed first engaging means such as cam roller assemblies  92  which extend into longitudinal slots  76  in intermediate head  56 . The opposite end of annular piston  80  includes a radially disposed second engaging means such as cam roller assemblies  94  which extend into helically formed slots  96  on drive bushing  98 . Drive bushing  98  includes splines  99  (seen more clearly in FIG. 7) which engage mating splines  101  on stem  44 . 
     Housing  18  is a generally cylindrical member with end flange  100  formed on its outer end. Bore  102  on the interior of end flange  100  closely fits about stem  44  that extends therethrough. Seal element  104  seals the annulus between bore  102  of end flange  100  and stem  44 . Recess  106  is formed on the interior of end flange  100  and receives thrust bearing assembly  108 . Thus, drive bushing  98  is captured between thrust bearing assemblies  82  and  108  and is able to rotate. Housing  18  includes hydraulic ports  110  and  112  to allow hydraulic pressure to be applied to opening chamber  114  and closing chamber  116  for purposes to be explained hereinafter. Closing chamber  116  has an urging means such as belleville springs  118  positioned therein to urge annular piston  80  to its closed position. End flange  100  of housing  18  includes a plurality of set screws  120  equally spaced circumferentially thereabout with a pipe plug  122  at the outer end of each set screw hole  124  for purposes to be explained hereinafter. 
     Release cap  26  is a generally cylindrical member with inner flange  126  at one end and inner recess  128  extending from inner flange  126  to end cap  130  with bore  132  extending therethrough. Release cap  26  is secured to end flange  100  of housing  18  with studs  134  and nuts  136  with seal ring  138  disposed therebetween. Stem  44  extends through bore  132  with seal ring  140  sealing the annulus therebetween. Release assembly  142  is positioned on stem  44  and locks into inner recess  128 . Release assembly  142  includes body  144  closely fitting in the annulus between stem  44  and inner recess  128 . Body  144  has a reduced diameter lower section  146  with lock ring  148  disposed in the annulus between body  144  and inner recess  128 . Snap ring  150  is positioned on body  144  and is biased to lock into groove  152  on inner recess  128 . Split ring  154  is positioned in groove  156  on stem  44  and bearing  158  positioned against split ring  154 . Seal ring  160  is positioned on the inner bore of body  144  to seal against stem  44 . Bearing  162  is positioned on the opposite end of body  144  and retained by split ring  164 , keeper ring  166  and snap ring  168 . Lock ring  148  has seal rings  170  and  172  disposed on its exterior and interior, respectively, for purposes to be explained hereinafter and is retained on body  144  by snap ring  174 . Pressure ports  176  and  178  supply hydraulic pressure to the interior of release assembly  142  to allow axial movement of stem  44 . 
     Referring to FIG. 5, a sectional view through high torque rotating actuator  10  shows the interaction of lower head  22 , release rods  24 , stem  44  and intermediate head  56 . Retaining ears  180  are formed on the exterior of intermediate head  56  with an elongated hole  182  therein. Release rods  24  pass through elongated holes  182  and are threaded into lower head  22 , as best seen in FIG.  2 . Retaining ears  180  are drilled and tapped to receive set screws  184 . After attachment of high torque rotating actuator  10  to extension spool  12  and valve  36 , high torque rotating actuator  10  is rotated to allow the opening and closing positions of valve  36  to be adjusted. Once the desired adjustments have been made, set screws  184  are locked against release rods  24  to maintain the opening and closing positions of valve  36 . Referring to FIG. 6, a sectional view through high torque rotating actuator  10  shows the relative position of stem  44 , intermediate head  56  and longitudinal slots  76 . 
     A typical sequence of operations for using the high torque rotating actuator  10  of the present invention is as follows. As noted previously, once the high torque rotating actuator  10  is assembled the relative position of retaining ears  180  and release rods  24  is adjusted. The high torque rotating actuator  10  is then attached by extension spool  12  by bolts  38  and flange  40 , making sure the keyed end connection  46  is properly connected to valve stem  48 . The next step is setting the open and closed stop positions of ball  36 . Hydraulic pressure is slowly applied to valve open port  110  until the ball  36  is fully open and will pass a drift bar. Set screws  120  in end flange  100  are screwed into contact with annular piston  80 , preventing further stroking of annular piston  80 . In this position the ball  36  is fully open with belleville springs  118  compressed. 
     When it is desired to close the ball  36  in cartridge ball valve assembly  32 , pressure is released from port  110  allowing belleville springs  118  to expand. This expansion force is exerted on annular piston  80  causing cam roller assemblies  92  to travel along longitudinal slots  76 . Simultaneously, cam roller assemblies  94  are traveling along helical slots  96  of drive bushing  98  which rotates on thrust bearing assemblies  82  and  108 . The rotation of drive bushing  98  is transmitted through splines  99  and  101  to stem  44  and hence to ball  36  thereby closing the valve. Helical slots  96  typically will have two helix angles. The initial angle will be shallow, allowing drive bushing  98  to rotate rapidly with minimal torque for the first 80 degrees of ball rotation. It is envisioned and within the scope of the current invention that helical slots  96  could have several different helix angles that would allow drive bushing  98  to generate a greater torque at a plurality of intervals during its rotation. The cam roller assemblies  94  will then enter the steep portion of helical slots  96 , which will increase the torque generated dramatically to close the valve completely, using only the force of belleville springs  118 . 
     In the event of an actuator failure, a remotely operated vehicle (“ROV”), well known to those of ordinary skill in the art, will be used in one of two ways to dose the cartridge ball valve assembly  32 . The first and easiest method to ensure closing of cartridge ball valve assembly  32  is to have the ROV “hot stab” pressure port  112  to pressure closing chamber  116  and assist belleville springs  118  in closing the cartridge ball valve assembly  32 . In the unlikely event drive bushing  98  is damaged and unable to rotate, the ROV can be used to unscrew release rods  24  from lower head  22 . The ROV can then be used to rotate stem  44  and the entire high torque rotating actuator  10 . This will allow the stem  44  to rotate ball  36  and close the cartridge ball valve assembly  32 . 
     Should the aforementioned procedures fail to close ball  36 , a final resort is to retract stem  44  from cartridge ball valve assembly  32 , allowing cartridge ball valve assembly  32  to be retrieved from vertical well bore  30 . This is accomplished using either release assembly  142  or release cap  26 . Preferably, an ROV “hot stabs” pressure port  176  which causes locking ring  148  to slide onto snap ring  150  thereby disengaging snap ring  150  from groove  152  in release cap  26 . Continued application of hydraulic pressure across the annulus sealed by seal rings  104 ,  160 ,  170  and  172  causes stem  44  to shift outwardly thereby disengaging from valve stem  48  and allow cartridge ball valve assembly  32  to be retrieved. In the event release assembly  142  fails to function, an ROV can remove nuts  136  securing release cap  26  to housing  18 . The ROV can then pull on stem  44  to release cartridge ball assembly  32 . 
     A second embodiment using the principles of the subject invention is shown in FIGS. 8-10. Rotating actuator  200  is shown in a sectional view and includes housing  210 , intermediate head  212 , drive bushing  214 , and piston  216  formed on stem  218 . Housing  210  includes end flange  220  on one end for securing rotating actuator  200  to a valve or choke to be operated. The opposite end of housing  210  has inner recess  222  which receives intermediate head  212  in close fitting engagement. Suitable securing means, such as bolts  223 , secure intermediate head  212  to housing  210  and prevent relative rotation therebetween. Intermediate head  212  is a generally tubular member with inner flange  224  formed therein. Intermediate head  212  has end flange  226  positioned at its outer end with seal ring  227  sealing therebetween. End flange  226  is secured to intermediate head  212  by studs  228  and nuts  230 . End flange  226  has a bore  232  fitting closely about stem  218  with seal ring  234  sealing the annulus therebetween. 
     The outer end of intermediate head  212  has inner recess  236  which receives piston  216  in sliding close fitting engagement. Seal ring  238  on the outside of piston  216  seals the annulus between inner recess  236  of intermediate  212  and piston  216 . Inner flange  224  has a bore  240  fitting closely about stem  218  with seal ring  242  sealing the annulus therebetween. Inner flange  224  of intermediate head  212  has recess  244  formed on its inner face with thrust bearing  246  positioned therein. A plurality of longitudinal slots  248  are formed on the inner end of intermediate head  212 . 
     Inner recess  222  of housing  210  has a recess  250  formed on its inner face with thrust bearing  252  positioned therein. Housing  210  has bore  254  at its inner end through which valve stem adapter  256  of drive bushing  214  extends. Drive bushing  214  has helical slots  258  (best seen in FIG. 10) cut radially through it. The inner end of stem  218  has a pair of engaging means in the form of cam rollers  260  and  262  attached with cam axle  264 . Cam rollers  260  and  262  engage longitudinal slots  248  of intermediate head  212  and helical slots  258  of drive bushing  214 , respectively. Pressure ports  266  and  268  provide hydraulic pressure to piston  216  to shift rotating actuator  200  between open and closed positions. 
     A typical sequence of operations for using rotating actuator  200  of the present invention is as follows. Rotating actuator  200  is moved to the open position by applying hydraulic pressure valve open port  266  which moves piston  218  to the position shown in FIG.  8 . When it is desired to close the valve attached to rotating actuator  200  pressure is released from port  266  and pressure is applied to dosing port  268 . This force is exerted on piston  216  causing cam roller assemblies  260  and  262  to travel along longitudinal slots  248  and helical slots  258 , simultaneously. As cam rollers  260  are restrained in longitudinal slots  248  of intermediate head  212  which is connected to housing  210 , cam roller assemblies  262  travel along helical slots  258  of drive bushing  214  causing drive bushing  214  to rotate on thrust bearings  252  and  246 . The rotation of drive bushing  214  and valve stem adapter  256  thus causes the valve connected to stem adapter  256  to close. As in the preferred embodiment, helical slots  258  typically will have two or more helix angles to produce the appropriate amount of torque at the appropriate point in the closing of the valve. Similarly, as in the preferred embodiment, it is envisioned and within the scope of the current invention that helical slots  258  could have several different helix angles that would allow drive bushing  214  to generate a greater torque at a plurality of intervals during its rotation. 
     The construction of our high torque rotating actuator will be readily understood from the foregoing description and it will be seen that we have provided a high torque rotating actuator that is compact and reliable and delivers a higher amount of torque when required to ensure the valve being actuated will fail safe dose. Furthermore, while the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalent alterations and modifications, and is limited only by the scope of the appended claims.