GB454546A - Improvements in or relating to shut-off valves - Google Patents

Abstract

454,546. Valve closure members. BUCKHAM, F., Bridge Wharf, Chalk Farm Road, London. April 8, 1936, No. 10375. [Class 135] In a stop valve having a shut-off piston provided with an expansible sealing-ring 32 located between piston members 29, 38 loose on the valve spindle 23, the longitudinal movement of the spindle to move the piston from the shut-off to the open position is also utilized to impart relative axial movement to the piston members 29, 38 whereby the sealing- ring is expanded in both end positions of the piston. The shut-off piston comprises a head having a nose piece 30 and a reduced portion 29 embraced by the sealing-ring 32, which is of resilient material such as compressed fibre. A pressure-cap 38 surmounts the end face of the ring 32. The piston head 29 and the cap 38 are capable of movement relative to the threaded valve-actuating spindle 23, a reduced portion 23<a> of which has two fixed collars 34, 35 between which the spindle is engaged by two radially slotted thrust plates 36, 39 secured by screws to the head 29 and cap 38 respectively. In closing the valve, the nose 30 is arrested by a ledge 31 in the valve casing, the ring 32, which then occupies the throat 12, being expanded into sealing engagement therewith by the cap 38 pressed inwardly by the spindle 23 acting through the collar 35 and the plate 39. When the valve is opened, the pressure on the cap 38 and hence on the ring 32 is immediately relieved and remains so relieved until the plate 39 abuts a rib 43 under the cover 19, whereupon the collar 34 acts on the head 29 through the thrust plate 36 to expand the sealing-ring against the throat 22 and so seal off the chamber 20 containing the stuffing box 27, from the controlled fluid. The cap 38 has a vertical slot engaged by a radial screw in the plate 36 to prevent it rotating relative to the head 29. The passage 16 in which the shut-off piston travels is shown inclined to the main fluid passage, but it may be perpendicular thereto. The throats 12, 22 may be separate rings of gunmetal or other substantially non-corrodible alloy, or they may be integral with the valve casing. The leading edge 44 of the piston part 29 scrapes any deposit from the throat 12.