Patent GB-892036-A (GB)
Title: Control valve having a movable member containing combination check and relief valve unit
IPC: F16K17/168
Filed: 1960-03-07
Abstract: 892,036. Fluid-pressure servomotor-control systems; valves. NEW YORK AIR BRAKE CO. March 7, 1960 [April 22, 1959], No. 7932/60. Class 135. The housing 11 of a three-position axially-slidable control valve embodies an inlet port 12, an exhaust port 13 and a valve bore 14 encircled by seven spaced annular chambers; chambers 15, 15<SP>1</SP>, 18 open into an exhaust manifold 19 whilst chambers 17, 17<SP>1</SP> lead to inlet port 12 via a manifold 21 with a relief valve 22, and chambers 16, 16<SP>1</SP> are connected to a fluid-pressure motor. Slidable in bore 14 is a plunger 23 with lands 26, 26<SP>1</SP>, 27, 27<SP>1</SP> and 28, the plunger mounting two combined check and relief valves 36, 36<SP>1</SP>. With the plunger 23 in the neutral position, shown, fluid entering the port 12 passes freely to port 13 through manifold 21, chambers 17, 17<SP>1</SP>, plunger grooves 25, 25<SP>1</SP>, chamber 18 and manifold 19; the motor pressure in chamber 16 is transmitted via a groove 39 around valve 36 and a restricted passage 48 to a chamber 49, the pressures in groove 39 and chamber 49 being equal, and since the rear end face 52 of valve 36 is of greater area than a shoulder area 47, the net pressure force on these areas together with the action of a spring 42 maintains the closure head 41 of valve 36 on its seat 37. Head 41<SP>1</SP> of valve 36 is similarly seated. A shock load on the motor will cause a pressure rise in chamber 16 and hence chamber 49, which will open a relief valve 45 seated in valve 36 and connect chamber 49 to the exhaust manifold 19 by radial passages 46, 33 ; since passage 48 is restricted a pressure difference will occur between chamber 49 and groove 39 which unseats the head 41, whereupon groove 39 communicates directly with radial passages 33 to permit a larger relief flow from chamber 16 to the exhaust manifold 19. When the pressure rise has ben relieved the valve 45 closes and brings about seating of the closure head 41. A pressure rise in chamber 16<SP>1</SP> is relieved by valve 36<SP>1</SP> in the same manner. Upon moving plunger 23 to the right against its centering spring 53 the passages 33 are closed by a fixed land 54, whilst lands 27, 28 interrupt communication between chambers 17, 17<SP>1</SP> and 18, whereby the fluid in manifold 21 flows via chamber 17 to act against and unseat the head 41, thereby admitting this fluid to chamber 17. Closure of passages 33 causes valve 45 to remain closed and the pressure in chamber 49 and groove 39 to be equal. Fluid from the other side of the motor exhausts from chamber 16<SP>1</SP> through chamber 15<SP>1</SP> to the manifold 19, a parallel path being established via a bore 43<SP>1</SP>, in which is valve 45<SP>1</SP>, and radial passages 46<SP>1</SP>, 33<SP>1</SP>; the valve 361 remains closed. The reverse operation of the motor and valves 36, 36<SP>1</SP> occurs when the plunger is shifted leftwardly. The valves 36, 36<SP>1</SP> prevent movement of the motor under the action of external loads during the time between moving the plunger from its neutral position until the inlet (pump) pressure has built up to operating value.