Patent GB-578738-A (GB)
Title: Improvements in non-return valves
IPC: F16K15/02
Filed: 1941-04-08
Abstract: 578,738. Non-return valves. ANGLOIRANIAN OIL CO., Ltd., STANSFIELD, R., and MUNTZ & CO., Ltd., A. April 8, 1941, No. 4649. [Class 135] A non-return valve assembly particularly adapted for use in high-speed compressors and pumps is provided with a closure member having a dished end to co-operate with the valve seat and a tubular portion adapted to constitute a stiffening flange adapted to slide over a guide member coaxial with the valve seat. The closure member co-operates with the guide to form a chamber communicating, in the open position of the valve, with the. throat of a convergent-divergent passage between the valve member and the surrounding casing. As shown in Fig. 1, a series of six valves are arranged around a single central valve. The entry end of each of the passages 16 in the base 10 converges relatively sharply to a circular port 17 beyond which the wall is shaped as a part-spherical surface 18 merging through a divergent part 19 into a cylindrical wall 20 enclosing the whole series. An upper casing part 11 is secured to the base 10 by bolts 12 and dowel-pins 13 and has three parallel transverse ribs of stream-line section supporting the upper parts of guide-members 22. The guides are extended by parts 23 secured by rivets 24 to the parts 22. The valve members 27 of pressed sheet metal have a cylindrical skirt which is a sliding fit on the lower cylindrical part of the guides which beyond this part are tapered to produce a divergent passage having-such a rate of taper and length that at the exit opening a substantial part of the pressure drop in the convergent part is recovered. A loading spring 28 housed in an annular chamber formed between the head of the rivet and a counterbore in the part 23 acts on the valve member urging it towards its closed position. When the valve is open, the reduced pressure at the throat passes to the back of the valve through the clearance between the valve and guide to hold the valve in contact with the guide and prevent chattering. As the inlet pressure falls, the spring returns the valve to its seat before any reversal of flow takes place. In the form shown in Fig. 4, the dished end of the valve forms part of a sphere with a radius R2 slightly less than that R1 of the spherical part of the seat. The radius R1 is about .8 of the diameter D1 of the port 17 and the axial length of the part 18 is about .3 of the' diameter D1. The frusta-conical part 18 is coned to an angle of 10 degrees, while the angle of slope of the guides S is about 6 degrees and the guides are continued until the effective cross-sectional area is twice the aggregate throat area. The valve skirts have ports 30 adapted during the intermediate part of the travel to communicate through a groove 31 and passages 32 in the guide with the internal chamber so that while the valve member moves quickly over most of its range, its movement is cushioned near the limits of its travel. As shown in Fig. 5, the valve is guided by a tubular stem 33 welded to the valve member at 35 and engaging a socket in the guide. The ends of the guides are recessed at 36 so that when the valve is fully open its outer'surface is flush with the guide. The vent ports 30B are disposed adjacent the dished end of the valve member. According to the Provisional Specification, a tangent to the surface 18 adjacent. the port 17 may intersect the axis of the passage at an angle of 37 degrees and the radius of port may be about 7 of the' radius of the part 18. A tangent to the part-spherical end of the valve member adjacent the shoulder may intersect the axis of the passage at an angle of 39 degrees.