Patent GB-500574-A (GB)
Title: Improvements in or relating to shock absorber struts for aircraft
IPC: B64C25/22
Filed: 1937-08-12
Abstract: 500,574. Shock absorbers. ONIONS, J. H., and RIBBESFORD CO.. Ltd. Aug. 12, 1937, No. 22209. [Class 108 (iii)] [Also in Group XXXXIII Relates to shock-absorbing struts for aircraft comprising a plunger 12, 14 reciprocable in a cylinder 10 under the control of a spring, vohune of gas or other resilient means for damping out shocks due to landing &c., and having means for supplying fiuid to and extracting fluid from the cylinder and an annular space 21 between the overlapping portions of the cylinder and plunger to vary the length of the strut without affecting the resilient means. According to the invention, a locking valve 32 controls the flow of fluid into or out of the cylinder and is urged automatically e.g. by springs 40, 41 to take up a position preventing such flow, the valve being movable from that position only by the pressure of fluid supplied to effect a change of length of the strut. As shown in Fig. 1, a floating piston 16 in the tube 12 separates the resilient means, from liquid in the remainder of the tube and in the cylinder and shock is damped by flow of fluid past a restricting valve 20 in the plunger head 14. The fluid-pressure system shown for varying the length of the strut comprises a reservoir 60, a pump 26, and a manually-operable control valve 27 the casing of which is connected by pipes 28, 31 to the chamber 30 of the locking valve 32, a branch 23 from pipe 28 leading to the space 21. To shorten the strut the control valve 27 is moved to the position shown and liquid is forced by the pump through the pipes 23, 28 moving the locking valve 32 to the left so that liquid displaced by the upward movement of the plunger head 14 due to the entry of liquid into the space 21, is forced to the reservoir through a port 37 in the upper end of the cylinder, an annular groove 34 in the valve 32, the pipe 31, and valve 27. The control valve is then returned to its neutral position in which it closes the pipes 23, 28 thus locking the plunger in the raised position. To extend the strut the valve 27 is moved to the right and liquid is forced by the pump through pipe 31, valvegroove 34, and a port 38 in the valve 32 to a space 39 in the valve-chamber, moves the valve 32 to the right and then flows through the port 37 into the cylinder 10 forcing out the plunger. The invention is shown in Fig. 3 applied to an undercarriage in which a landing-wheel is retracted backwardly, by means of a jack 53 acting on a folding strut 54, 55, into the space between the front and rear wing spars 51, 62, the distance between which is less than the extended length of the strut. A combined operating system for shortening or lengthening the strut and retracting or lowering the undercarriage respectively is also described, the major part of the system being identical with that shown in Fig. 1, the pipes 28, 31, however, being branched to feed the jack through a control valve by means of which the jack may be locked in position. Means such as the interposition of a restricting valve in the branch from the pipe 28 and the provision of a strong spring acting on the valve 32, or alternatively the provision of a series of interlocking valves, may be provided to ensure shortening or lengthening of the strut before or after respectively the retraction or lowering of the undercarriage. The undercarriage may also be retracted sideways. Fig. 5 shows the invention applied to a non- retracting, cantilever type of undercarriage in which the strut cylinder 10 carries a fairing 58 into which the wheel 50 may be lifted by means of the system previously described. The pump 26, Fig. 1, may be operated manually or it may be driven mechanically or electrically and supplemented by an auxiliary hand-pump. It is also stated that the length of the strut used may be varied by means other than liquid pressure, e.g. by gas pressure, or by atmospheric pressure, a partial vacuum being created in the strut cylinder by a pump &c.