GB864519A - Improved annular fluid control valve device - Google Patents

Abstract

864,519. Valves. ROLLS-ROYCE Ltd. July 27, 1959 [Aug. 5, 1958], No. 25119/58. Class 135. [Also in Group XXVI] An annular valve device comprises a cylindrical casing, an annular valve seating associated therewith, a plurality of parallel, substantially axially extending levers which are spaced from each other round the casing and are mounted for rotation about axes extending substantially radially of the casing, an annular valve member mounted on the easing for movement into and out of sealing engagement with the seating, and joints interconnecting the levers and the valve member so that pivotal movement imparted to one or more of the levers produces circumferential and slight axial movement of the valve member relative to the casing to open and close the valve. In an embodiment applied as an air bleed valve for a gas turbine compressor, one stage 11a is provided with air bleed openings into an annular valve chamber 15 and flow out of this chamber into a by-pass duet is controlled by an annular valve member 16 having closure flanges 17, 18 co-operating with seat flanges 13, 14 constituting walls of the chamber. The valve member provides a baffle 20 angled in the direction of the by-pass air flow, and is carried by a number of levers 23, e.g. six, spaced round the casing, one end of each lever being pivoted on the casing at 30 and the other end being forked over a boss 28 of the valve member, this boss having a spherically seated bush 24 on a pin 25. One of the levers as shown is provided with an operating shaft 31 which extends across and to the outer side of the by-pass duct, and is rotatable through a lever 33 by an hydraulic ram 35. The valve member is thus partly rotated and at the same time moved axially away from the seats 13, 14 to open the valve. The closure flanges 17, 18 have unequal effective areas so that fluid pressure tends to urge the valve member towards the closed position. Boss 28 in mean position fits with equal clearance 29 on opposite sides between the forked ends 26, 27 of lever 23 to allow for relative radial movement as illustrated in Fig. 4, wherein the circle 36 represents the compressor casing, radial line 38 the mean position of boss 28, and lines 37, 39 parallel to line 38 the positions of the boss in closed and open positions respectively of the valve member. Line 37 also represents the pivotal axis of the operating shaft 31 or the fixed pivot 30. A small residual clearance " B " in closed position and " A " in open position is allowed for between boss 28 and the forked ends 26, 27. In modifications, the flange 17 of the valve member may be provided with a resilient sealing ring (Figs. 6 and 7, not shown) ; or this flange may have a thin resilient section 17b so as to seat resiliently (Fig. 8, not shown). In another modification, Fig. 10, the valve member 124 has three flanges 125, 126, 127 co-operating with the. two seat flanges 13<SP>1</SP>, 141 so that in open position bleed air can escape only to the downstream side of the deflector 20, through a gap 128 between the flanges 127, 13<SP>1</SP>. A diametrically opposite pair of the levers 23 may be operated to balance the forces. In Figs. 5 and 9 (not shown) the air bleed valve is incorporated respectively in a compound by-pass gas turbine having a duet by-passing the H.P. compressor, and in a single-stage gas turbine with an air bleed manifold replacing the by-pass duct (see Group XXVI].