GB301534A - Improvements in automatic self-closing valves - Google Patents

Abstract

301,534. Glenfield & Kennedy, Ltd., and Price., O. A. Sept. 1, 1927. Addition to 254,870. Fluid-actuated valves.-An automatic selfclosing valve of the kind described in the parent Specification in which the valve is carried by a plunger subject on its front and rear faces to the pressures existing at constricted and full bore sections of the main conduit and provided with an external piston, has equal pressures maintained on opposite sides of the piston during normal flow and the plunger and piston arranged to form parts of a stream line body spaced from the wall of the conduit. In the form shown in Fig. 1 (22949/27 Prov.) the front of the plunger 1 is arranged close to the constriction 8 and the piston 11 has a skirt arranged to slide over the fixed members 2, 3 and provided at its forward end with a valve face 9 adapted to co-aperate with a seat 10. The chambers 12, 13 on each side of the piston are connected by a loop of piping 14, 15 fitted with a throttle valve 21 connected by an arm 22 and link 23 to the weighted lever 17 coupled to the main valve. Each of the pipes 14, 15 is fitted with a handactuated two-way valve whereby pressure may be exhausted from either of the chambers 12 or 13 to open or close the valve. The pipe 14 is connected through a valve controlled pipe S with the main conduit down stream and the pipe 15 through a valve controlled pipe R with the main conduit upstream. A valved byepass 29 to the main valve may be fitted. The closing of the main valve is at first rapid being afterwards retarded by the action of the throttle valve 21. Further devices may be fitted to cause the final closing movement to be dead slow. Fig. 1 (33946/27) shows one device for accomplishing this. A valve a<4> adapted to admit full conduit pressure to the chamber 13 is actuated by a spring loaded diaphragm a subject on one side to full bore pressure admitted through a pipe a<1> and on the other side to the pressure at a point adjacent the valve seat which pressure approximates to the full bore pressure when the, valve is fully open or fully closed but is reduced as the main valve approaches its seat. A second valve b<4> may be arranged to admit reduced bore pressure to the chamber 12 at the same time as full bore pressure is admitted to the chamber 13. In the arrangement shown in Fig. 2 (33946/27) the valves controlling the supplies to the chambers 12, 13 are actuated by a floating lever e coupled on the one hand to the loading lever 17 and on the other to a dashpot piston c. The weight c<4> loading the dashpot is normally held in its raised position by the end h of the lever e engaging a fixed catch plate f and the rate of its descent is regulated by a cock c<3> which may be interconnected with the piston. The connection between the link g and lever e may be made detachable so that the retarding gear may be put out of action. To reduce the weight of the plunger the rear half of the piston skirt may be dispensed with, the front portion working between the members 2, 3. The rear wall of the plunger may also be renewed to allow it to work over a tubular projection on the member 2.