GB834434A - Improvements in lubricated rotary plug valves - Google Patents

Abstract

834,434. Valves. ROCKWELL MANUFACTURING CO. Aug. 13, 1956 [Aug. 18, 1965], No. 24670/56. Class 135. In a lubricated rotary plug valve in which a tapered plug is urged towards a corresponding seat by spring means and in which stop means independent of the spring means are provided for positively limiting the axial movement of the valve plug away from its seat in response to an hydraulic jacking force produced by the operation of lubricant supply means, the spring means have a deflection range in which the biasing force they exert is substantially constant. A plug 23, Fig. 1, with a through port 21 is urged against conical seating surfaces 15, 17 in a casing 11 by a conically dished spring washer 73 acting between the base of a stub stem 26 and the floor of a recess 66 in a cover-plate 67. The cover-plate 67 is secured to the casing 11 by bolts 69, a skin or gasket 71 of selected thickness being interposed. This thickness is such that the load exerted by the washer 73 is independent of its deflection over the range of deflections from the seated position of the plug to the position in which the washer is flattened against the floor of the recess 66. The plug has an upper stem 25 with a square head 27 and a threaded bore 35. The bore 35 contains a check valve assembly 41 and a lubricant jack screw 43, and communicates by cross-bores 37, 38 with a lubricant chamber 39.. An annular groove 50 and four longitudinal grooves such as 46, 47 in the plug surface together with upper and lower dwarf grooves such as 54, 55 and 50<SP>1</SP> are arranged to be in mutual communication when the plug is in the open or closed position. The chamber 39 is sealed by an L-section low-friction plastic ring 59 backed by a resilient 0-ring 61. A ring 64 of felt or leather arranged beneath a flanged stop collar 29 prevents the entrance of dirt into the clearance space 56. A small passage 77 admits line pressure to a space 78 below the plug and a bore 79 vents the recess 66. In Fig. 6, the stub stem 26 is dispensed with and the resilient plug biasing means comprise a pair of spring discs 97, 98 engaging peripherally a shoulder 110 surrounding a shallow recess 100 in the plug base. The centre of the discs 97, 98 engages a bearing insert 95 which is either of predetermined size or is adjustable by a screw 104 in the cover-plate 87. The downward movement of the plug is arrested when the centre of the disc 97 engages the floor of the recess 100. A gasket 90 and sheet metal or other thin diaphragms are clamped between the cover-plate 87 and the valve casing. In Fig. 7, the smaller end of the plug enters a closed chamber 128 and the plug 125 is urged to its seat by a dished spring 129 in a recess 131 formed in a cover-plate 121. The spring 129 acts at its inner periphery through a rigid metal washer 133 and the adjacent portion of an asbestos sealing gasket 135 clamped with a flexible steel diaphragm 136 between the coverplate 121 and the valve casing. Axial movement of the plug in this case is limited by the spring being flattened against the floor of the recess 131. In further modifications, the spring 129 is replaced by a stack of annular dish-shaped springs and additional sealing means similar to the rings 59, 61, Fig. 1, are provided in the clearances around the plug stem. Also the rigid metal washer such as 133 is surrounded by a further rigid washer to support the diaphragm against resistance or being pulled out peripherally. In one form, the further rigid washer is itself clamped peripherally with the diaphragm. Specification 802,497 is referred to.