Patent GB-456897-A (GB)
Title: Improvements relating to shock absorbers
IPC: B64C25/60
Filed: 1935-04-17
Abstract: 456,897. Shock-absorbers. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. April 17, 1935, No. 11884. Convention date, April 26, 1934. [Class 108 (iii)] A combined hydraulic and pneumatic shockabsorbing strut for aircraft comprises telescoping cylindrical members 212, 220, the former of which is provided with a tapered metering pin 232 co-operating with an orifice 230 formed in a piston member 228 secured by a threaded collar 224 to the inner member 220. Mounted above the orifice 230 is a chamber 234 clamped between the cylinder 220 and the piston 228 and provided at its opposite end 248 with a flap valve constituted by a plate 246 sliding on headed pins 244. During the compression stroke of the strut liquid passes through the decreasing orifice 230, opens the valve 242 and is forced into the outer cylinder against the pressure of the air above the liquid. During the rebound or extension stroke, the valve 242 closes and liquid passes through bleed holes 250 into the metering-pin chamber and through the orifice 230. The extension movement is limited by the engagement of a collar 268 on the inner cylinder 220 with a rubber ring 270 mounted near the end of the outer cylinder 212 by means of a collar 272 and flanged nut 276. Packing mounted between the inner and outer cylinders is held in position by a ring 264 engaged by an unthreaded overhanging extension 262 of a sleeve 258. In a modification of Fig. 1, Fig. 2 (not shown), the extension movement is limited by a slidable sleeve member located between members corresponding to those denoted by 264, 272 in Fig. 1, the resilient effect of the rubber ring 270 at the end of the extension being achieved in the modified construction by the compression of the packing material disposed between the cylinders. The Specification as open to inspection under Sect. 91 describes an arrangement in which the metering pin is shaped so that initially the resistance to motion is quickly built up and as the piston velocity increases the area between the metering pin and the orifice is gradually increased to maintain a substantially constant resisting force. After the maximum velocity of the piston has been attained, the cross-sectional area of the pin is gradually increased to maintain an approximately constant pressure on the piston, and during the final portion of the stroke, the fluid-resistance arrangement is supplemented by a compression spring. In a modification the packing chamber is formed by the upper portion of the cylinder carrying the metering pin and moves with it. In a further modi. fication Fig. 8 (Cancelled), the cylinder 456, in which the metering pin 462 is mounted, slides over the orificed member 436 on which the scrubbing chamber 446 is supported and the packing chamber 418 is formed between the cylinder 456 and an enlarged end-portion of a fixed concentric tube 410, the packing being compressed between rings 422, 424. The extensional movement of the cylinder 456 is limited by a nut 458 which engages the packing ring 422. In a further modification of Fig. 8 (Cancelled), the packing is held between rings secured to the cylindrical member carrying the metering pin. In a further construction, Fig. 12 (Cancelled), the outer cylindrical casing is formed by two cylinders 610, 646, threaded on flanges 626, 630 of the orificed member 632 The metering pin 664 is mounted on a piston 662 sliding in the lower cylinder 646 and having a skirt 666 which forms the inner wall of a packing chamber 668. The packing 670 which is retained by a ring 672 held by a threaded member 674, moves with the piston 662. This subject-matter does not appear in the Specification as accepted.