Abstract:
A hydraulic cylinder is provided with pistons to provide both rotary and a linear motions; utilization of a built in check valve traps fluid pressure to sustain piston in a desired operating position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to movable valves and more particularly to a hydralic actuator for providing both rotary and linear motion to the valve in an opening and closing operation. 
     With operating conditions changing wherein pressure through valves increases, larger size of valves are required. The increase in size of the valve requires more powerful actuators than the automatic actuators now available. 
     SUMMARY OF THE INVENTION 
     A hydraulic actuator for operating the plug of a valve between open and closed positions as fast as required. Prior to rotation of the plug into the open position the plug is moved along the axis of the plug to effect the disengagement of the plug from its seat. Thus, in an initial opening movement the hydraulic actuator imparts a lifting motion to the plug followed by rotation of the plug to open position to align the plug passageway with the flow passageway of the valve body. In a closing movement the valve plug is rotated to block the flow passageway an then lowered into sealed engagement with the seat. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic showing of a valve with the hydraulic actuator connected to the valve plug; and the valve plug in elevated open position; 
     FIG. 2 is a showing similar to FIG. 1 with the valve plug in full closed position and in its lowered sealed position; and, 
     FIG. 3 is an enlarged view in elevation of the actuator with parts broken away to show the operating components of the actuator. 
    
    
     DESCRIPTION OF THE INVENTION 
     A line valve 10, FIG. 1, includes a valve body 11 in which a valve plug 12 is operably disposed. The valve plug 12 is depicted in FIG. 1 in full open position wherein a fluid passage 14 is aligned with connected pipes to allow free flow through the valve. In full open position the valve plug 12 is in an elevated position within the valve body wherein spaced apart circular seats 16 and 17 on the valve plug 12 are not in sealing engagement but are in close proximity with associated circular seats 18 and 19 secured to the internal surface of the valve body. To move the valve plug 12 to a closed position the plug is rotated 90 degrees from the position depicted in FIG. 1 and thereafter lowered to effect sealing engagement of the seats 16-17 with the seats 18-19 as depicted in FIG. 2. 
     The rotational movement of the valve plug 12 between open and closed positions and the axial movement of the valve plug to an elevated or lowered position is difficult and requires special complex mechanical devices to accomplish the required movements. 
     To this end there is provided a fluid actuator 20 which is operably connected to a valve stem 15 associated with the valve plug 12. As shown in detail in FIG. 3, the actuator 20 includes a body portion 21 provided with an axial bore within which a lift piston 22 is axially movable within a first cylinder or chamber 23 formed in lower portion of the bore of the body 21. The lower end of the piston 22 is formed with a depending stem 24. The piston stem 24 extends through a suitable axial aligned opening formed in a base plate 26. An axial bore 27 in the piston stem 24 receives the extending end of the valve plug stem 15. A pin 28 establishes an operative connection between the cooperating engaged parts. Extending upwardly from the lifting piston 22 is a piston rod member or motion translation means 29 having an axial passage 31. Spaced from the upper surface of the lift piston 22, the rod 29 is provided with an enlarged portion having axial extending splines 35 which have engagement with internal splines 33 formed on the depending end of a stem 34 of a rotation drive piston 36. The outer surface of the depending stem 34 is provided with an acme threaded portion 37 which is in operative engagement with a cooperative threaded portion 38 formed in an internal bore portion 39 of the actuator body 21 and constituting a first rotational drive means. The rotation piston 36 is displaceably axially within a cylinder or chamber portion 41 formed within the housing bore above the threaded bore 39. Thus, fluid under pressure applied to one side or the other of the piston 36 will effect axial movement of the piston in a selected direction. For example, fluid pressure to the cylinder 41 at the head side of the piston 36 will operate to force the piston downwardly. In moving downwardly a rotational movement is imparted to the piston 36 and its associated stem member 34 by reason of the threaded engagement between the stem and the bore 39. This rotation movement is transmitted to the piston rod member 29 by operation of the spline drive connection established between the enlarged portion and the rotating piston stem 34. This rotation is, in turn, imparted to the valve plug 12 via the connected stem 15. 
     Fluid pressure to operate the actuator 20 in a line valve closing movement is admitted from a controlled source (not shown) to the actuator via a port B. The fluid pressure enters the cylinder 41 on the stem side of the rotating piston 36 via a passage 46. Pressure applied to the stem side of piston 36 will effect an upward movement of the piston to the position it occupies as depicted in FIG. 3. The piston 36 in moving upwardly will rotate by operation of the threaded engagement effected between the piston stem 34 and the bore 39 of the actuator body 21. The rotation of the piston 36 will effect rotation of the lift piston rod 29 by operation of the spline drive connection between the rod 29 and the stem 34. This rotation will rotate the valve stem 15 and thereby the valve plug 12 to rotate 90 degrees from its open position depicted in FIG. 1 to a closed position depicted in FIG. 2. 
     When the rotation piston 36 is in a full upward position it will engage a spring loaded pin 49 associated with an internal check valve 51 to unseat a check valve ball 52. With the check valve ball 52 unseated fluid pressure in a chamber 54 below the lift piston 22 will exhaust via a radial passage 53 in the stem member 24. The fluid will exhaust upwardly through the vertical passage 31 to a chamber 55 and thence by means of communicating passages 56 to 57 to a passage 58 in the cylinder head closure 59. With the ball 52 of the check valve 51 unseated, the fluid in passage 58 will exhaust through the check valve to a chamber 61 and flow out of the actuator through a port A to a system reservoir (not shown). With the fluid chamber 54 below the lift piston 22 connected to exhaust, fluid pressure in the cylinder 41 on the stem side of the piston 36 will flow through a radial passage 63 into a chamber 64 formed by the piston rod 29 and the bore of the rotating piston stem 34 and thence through the splines 33 and 35 into the chamber 66. Fluid will also flow downwardly through the threads 37 and 38 into a chamber 66 combining with the fluid flowing through the splines 33 and 35 will act on the top side of the lift piston 22 to force the piston downwardly thereby effecting the lowering movement of the line valve plug 12 from an elevated position to effect sealing engagement between the seats 16-18 and 17-19. With this condition obtained the valve plug 12 is in a closed position and sealed to prevent fluid flow through and around the valve plug 12. The pressure at port B sustains this condition until there is a signal to open the line valve 10. 
     Upon a signal to open the line valve 10 port B is connected to the reservoir or exhaust and fluid under pressure is supplied to port A. Fluid pressure flows into the chamber 61. Since the ball side of the check valve 51 has been relieved of pressurized fluid, as previously described, the fluid under pressure in the chamber 61 will move through the check valve 51 into the passage 58. From the passage 58 fluid under pressure will flow into the chamber 55 via connecting passages 57 and 56. From the chamber 55 the fluid under pressure will flow through a metering valve 68 which is sized according to the size of the line valve to be operated. The fluid continues through the metering valve 68 and the rod passage 31 into the radial passage 53 and thence to the chamber 54. Fluid under pressure in the chamber 54 will act on the under surface of the lift piston 22 causing the piston to move axially upwardly. This action effects axial upward movement of the stem 24 thereby effecting upward movement of the valve plug 12 to disengage the plug seats 16-17 from the valve body seats 18-19. The check valve operates to maintain the piston 22 and the associated rod 29 in uppermost position assuring that the line valve plug 12 will be maintained in an elevated position when in open condition. 
     With the valve plug 12 in an elevated position, it is free to be rotated from the closed position it occupies as depicted in FIG. 2 to its open position as depicted in FIG. 1. To this end the rod 29 upon reaching its uppermost limit of travel effects an upard displacement of a shaft ring 71 from its seat 72 by means of a shoulder 73 which engages and lifts the ring. Thus, the fluid under pressure in chamber 61 will flow into a chamber 74. From the chamber 74 fluid under pressure will flow through a communicating passage 76 to a chamber 77 above the rotating piston 36. The fluid pressure in chamber 77 will act on the piston 36 to force it downwardly. The downward movement of the piston 36 will effect its rotation by operation of the threaded connection between the piston stem 34 and the threads of the bore 39. This rotation effects rotation of the rod 29 by operation of the spline drive 33-35 thereby effecting the rotation of the valve plug 12 from a closed position as depicted in FIG. 2 to its open position as depicted in FIG. 1.