Patent GB-769323-A (GB)
Title: Improvements in or relating to valves
Inventor: FRASER JOHN
IPC: F16K1/12
Filed: 1954-05-04
Abstract: 769,323. Slow-closing valves. AVERYHARDOLL, Ltd. April 21, 1955 [May 4, 1954], No. 12980/54. Class 135. Construction.-In a valve comprising a body 29, Fig. 3, having a through passage in which is an annular seat 32, a valve closure member 36 co-operating with the seat to close the passage and movable away from the seat 32 into a chamber 55 having a permanently open restricted communication with the flow passage on the upstream side of the seat 32, a pilot valve 48 to connect the chamber 55 with the flow passage on the downstream side of the seat 32, and manually operated means, such as an arm 27, for opening first the pilot valve and then the valve closure 36, a latch, for example a pawl 84, Fig. 7, is provided to hold the closure member 36 in the open position. The valve in a branch of a pressure fuel main such as is used for refuelling aircraft is disposed below ground level and comprises the hollow bulbous body 29, Fig. 3, having a cup-shaped member 34 intermediate its ends supported on radial webs 35; the upper end of member 34 serves as a guide for the closure member 36 provided with a lower cylindrical part 37, slidable in a non- fluid-tight manner in the member 34, and an upper conical part 38. A resilient packing ring 39 abutting the seat 32 in the valve closed position shown is secured between the member 36 and a cap 41 thereon, which latter has lugs 42 engaging slots 43 in the seat 32 to guide the member 36. The cap 41 is positioned by a cage 44 incorporating a depending valve seat for the frusto-conical head 49 of the pilot valve 48 formed with a stem 47 slidable in the member 36; with the pilot valve 48 open a flow path through the member 36 is afforded by the orifice 52. The pilot valve 48 and the closure member 36 are urged on to their seats by a spring 53, one end of which abuts a sleeve 54 in the chamber 55 comprised by the interior of the member 34; liquid pressure in the chamber 55 assists the closing action of the spring. The lower end of the stem 47 which passes through a partition 58 into a cylinder 59 threaded to the lower end of the member 34, has a piston 61 thereon that is slidable in the cylinder 59, the piston movement being limited by a shoulder 63 and a nut 64 both on the stem 47; internal axial grooves 65 in the piston 61 open into radial ports 66 in its upper surface so that when abutting shoulder 63 liquid can pass the piston by traversing grooves 65 and ports 66 whilst when it engages the nut 64 the grooves 65 are closed thereby. The lower end of the stem 47 is axially bored 67 and via radial holes 68 and 70 interconnects the lower end of the cylinder 59 with the chamber 55 when the valve is closed. According to the Provisional Specification the lower part of the closure element is provided with a guide rod, that passes through the cup-shaped member and a pilot valve stem which is connected by a diametral pin to a flanged collar around the element. A horizontal shaft passes through the valve body and with a fork engages the flange as well as having two arms, one of which is movable to open the valve and the other is arranged to engage a latch. Latching mechanism.-A collar 72 on the stem 47 is engaged by a finger 73 on a spindle 74 having a plate 77, Fig. 7, fixed thereto comprising two graduated portions 78 and 79, the portion 78 co-operating with stops 81 and 82 to limit the rotation of the spindle; the portion 79 is notched 83 for engagement by the spring- loaded pawl, 84 which holds the valve in the open position. A sleeve 86 loose on the spindle 74 carries a bell crank lever 87 and the operating lever 27, Fig. 3, one arm of the lever carrying a pawl 88, Fig. 7, loaded by a spring 91 cooperating with a lug 89 on the portion 78; the lever 27 and lever 87 are spring urged in a clockwise direction, their movement being limited by a stop 94 on the portion 78. With the parts in the positions shown, and upon pulling a tension member 26 thus moving the arm 27 anti-clockwise, the pawl 88 engages the lug 89 and the plate 77 is moved with the arm 27 to open the valve; after traversing a given angle the spring 91 moves through dead-centre and on further movement tends to swing the pawl 88 away from lug 89 but is prevented from doing so by undercutting of the latter. The portion 78 engages the stop 82 and upon releasing the chain attached to the arm 27 the pawl 88 clears the lug 89 and the lever 87 swings back against the stop 94, under the influence of the spring 91 and a further spring loading the arm 27, leaving the plate 77 latched in the valve open position. To close the valve the chain is again pulled to turn the arm 27 and lever 87 in an anti-clockwise direction; the latter engages a projection 95 on the pawl 84 and rocks it clear of the notch 83 so that the plate 77 is free to turn clockwise and the spring 53 closes the valve; movement of the arm 27 is limited by a stop 96. Operation.-Liquid in the body 29, Fig. 3, enters the chamber 55 between the members 34 and 36 and upon rotating the arm 27 to open the valve the finger 73 moves the stem 47 downwardly unseating the pilot valve 48 so relieving the pressure in chamber 55; the valve then abuts the closure member 36 and moves it away from the seat 32. The hole 68 passes through the partition 58 and permits free flow of liquid from the upper end of the cylinder 59 to the chamber 55; at the same time liquid also passes from the lower to the upper part of the cylinder via the grooves 65 and ports 66. Upon rotating the arm 27 to close the valve and after the unlatching operation the spring 53 urges the stem 47 and hence the element 36 upwardly whereupon the grooves 65 are closed and liquid cannot pass through the piston; until the hole 68 is obturated by the partition 58 liquid can flow from the upper part of the cylinder 59 to the chamber 55 but thereafter such flow is prevented and liquid can only escape into the chamber by way of an adjustable orifice 69 controlled by a needle 71 whereby the rate of valve closure can be set as required.