Viscosity responsive fluid flow control valve

摘要

966,358. Fluid-pressure servomotor systems. T. F. LEWIS. March 19, 1963 [March 28, 1962], No.10903/63. Heading G3P. [Also in Division F2] A valve arrangement 10 has an inlet port 16 connected to an hydraulic pump and an outlet port 17 open to a reservoir. When the hydraulic system is idle, gravity pressure from the reservoir traverses a passage 21 and urges a ball 27 on to a seat 23 of plastic material e.g. P.T.F.E. in the inlet 16. When the system becomes operative the accumulated air at the inlet 16 firstly urges the ball 27 on to a seat 26 in an outer piston 25 and then presses both members 25, 27 against a spring 43 until the ball 27 abuts a stop 34 on an inner piston 30; the outer piston 25 continues to move until the air can flow around the ball 27 to the outlet 17 through the passage 21 and is permitted to escape at the reservoir. A by-pass route for the air is also formed by a channel 50 in the outer piston, holes 40 in the inner piston opening 37 around a spring-loaded tube 35 in the main piston, and port 51 in the latter leading to the passage 21. An auxiliary ball 36 is associated with the outer end of the tube 35. After most of the air has been removed oil flows through the channel 50 and port 51 urges the ball 36 on to a seat 36a in the inner piston so closing the by-pass route whereupon the pressure builds up behind the outer piston 25 which moves leftwards until the seat 26 engages the ball 27. Air bubbles bleed around the ball 27 through the seat 26 which does not form a perfect seal but is such as to prevent the flow of heavier fluid.