Patent GB-159879-A (GB)
Title: Improvements in valves for regulating the flow of fluids
IPC: F16K1/12
Filed: 1921-03-03
Abstract: 159,879. Larner, C. W. March 9, 1920, [Convention date]. Valves controlled by pilot or relay valves.-A fluid-actuated valve device ,particularly applicable for use in connection with water power plant has the rate of opening and closing controlled by the condition of the fluid in the conduit so as to give a slow motion towards the end of the closing stroke and an arrested motion at the beginning of the opening stroke. In the form shown in the Figures, the main valve 4 is formed integrally with a hollow piston 51 loosely fitting in a cylinder 2 supported by webs 3 so as to form chambers 5, 6 having leakage passages 8a and 14 connecting them to the main conduit 7. These passages may be controlled by valves 9<a>, 15 normally held open by the pressure beneath them but adapted to close against stops 13 when that pressure falls. The chamber 6 is also supplied through a passage 16 in the piston so arranged that it is closed when the valve has moved a short distance from its seat. When using the valve for controlling flowing water the arrangement of auxiliary valves shown in Fig. 2 is employed, these valves being controlled by a handoperated cock 33 and by the condition of the fluid in the conduit. To open the main valve the cock 33 is turned so as to put the pipe 34 to exhaust while sealing the pipe 35. This relieves the pressure above the piston 29 and allows pressure leaking around the piston rod at 30<1> to raise the piston and unseat the pilot valve 28. This permits pressure which has leaked past the piston rod at 22<1> to pass to exhaust and allow the valve 25 to open and relieve the pressure behind the main piston. To prevent the too rapid opening of the main valve the space below the piston 29 is connected by a passage 36 to the neck of the main valve at 36<1> so that a high velocity of discharge reduces the pressure below the piston 29 and so arrests the opening of the main valve. During this operation pressure through leaking around the piston rod at 50<1> and around the piston 49 balances the piston and allows pressure acting on the enlargement 37 to close the valve 48 and permit pressure leaking around the piston rod at 42<1> to close the valve 45 and seal the supply passage 8. To close the main valve the cock 33 is moved to close the passage 34 and open the passage 35 to exhaust. This allows the valve 25 to close and reduces the pressure above pistons 49 and 59. Pressure leaking around the piston rod 57 at 60<1> raises the piston 59, opens the valve 58, and allows the pressure leaking around the piston rod at 52<1> to pass to exhaust and allow the valve 55 to open to connect the chamber 6 to exhaust. At the same time pressure leaking past the piston rod 47 at 50<1> moves the piston 49 to the right, opens the valve 48, and allows pressure leaking past the piston rod at 42<1> to pass to exhaust and allow the valve 45 to open and connect the inlet passage 8 to the chamber 5. To prevent the too rapid closing of the valve, the passage 36 is connected at 38 to the space to the left of the piston so as to close the valve 45 when the velocity past the main valve member is high. The pipe 35 may be connected by a pipe 40 to the turbine casing so that in the event of a breakage the main valve is automatically closed. When using the device to control dead water valves 9<a>, 15, and 45 may be dispensed with.