GB905091A - Improvements relating to fluid flow control valves - Google Patents

Abstract

905,091. Valves. COMPAGNIA ITALIANA WESTINGHOUSE FRENI E SEGNALI. June 21, 1960 [June 22, 1959], No. 21667/60. Class 135. A pneumatically or manually-operable fluidflow control valve, such as a gate valve, comprises two coaxially aligned rods 13, 5, one rotatable but restrained from axial movement and the other movable axially, a closure member 2 attached to the rod 5, a combination of a non-rotatable piston 7 and piston stem 7a mounted on the rods within a cylinder 9 and operably associated with the rods for pneumatic operation of the closure member, screw means 13a, 40 for translating the manual rotary movement in the rotatable rod into axial movement in the axially-movable rod, and a locking means 10, 12, 18, 20 for maintaining the closure member in the open or closed position. The rod 5 has secured thereto a sleeve-like member 11 which is located in a chamber 31 formed in the stem 7a the threaded rod 13 being arranged to move within the sleeve when the latter is rotated. Pegs 12 extend from each side of the sleeve and pass through elongated slots 32 in the step, the pegs engaging in the closed position shown, with the ends of a fork 18, Fig. 2, mounted on a spring-loaded member 38 and forming part of the locking means. In manual operation, when the rod 13 is rotated by a hand wheel 16 in an anticlockwise direction, the step 7a, together with the piston 7, lifts since the latter is prevented from rotation by a pin 8. Due to a clearance space between the end 24 of the chamber 31 and the end 23 of the sleeve 11, the first part of the movement of the stem 7a causes the fork 18 to be withdrawn out of engagement with the pins 12 by the contact of a roller 20 with the side of the stem. Continued rotation of the rod 13 then lifts the stem until the ends 23, 24 abut and thereby lifts both the rod 5 and closure member 2 to the open position; the closure member is locked in this position by the engagement of the fork 18 with the pins 10. In pneumatic operation, with the closure member in the position shown, compressed-air is fed through a connection in the bottom of the cylinder, thereby lifting the piston and the stem, and due to the angle of the helix of the thread 13a, causes the rod 13 to rotate, the action of the locking means being the same as previously described. The valve is closed by feeding compressedair through a connection b in the top of the cylinder.