Patent GB-474079-A (GB)
Title: Improvements in landing gears for aeroplanes and other shock-absorbers
IPC: B64C25/60
Filed: 1936-03-19
Abstract: 474,079. Shock-absorbers. MERCIER, J. March 19, 1936, No. 8215. Convention date, March 3, 1936. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 21, 1936.] [Class 108 (iii)] Relates to a shock-absorbing device particularly for aeroplane landing-gear in which at least one communicating channel 41, 40, 39, 38, Fig. 2, between two cylinder chambers 27, 37 separated by a piston 22, is closed by an obturating-device when the piston is displaced relatively to the cylinder 20 through a distance less than the maximum relative displacement and is opened during the return of the piston to the initial position and before the piston passes through the position in which the channel was closed. According to the invention, the obturating-device comprises an annular disc 35 which frictionally engages the cylinder 20 and through which the piston-rod or an extension 31 of the piston-rod slides, the disc being displaced in opposite directions by the piston and by a driving surface 32 secured to the piston and situated on the opposite side of the disc. The disc 34 divides the upper end of the cylinder into the chambers 36, 37 normally communicating through apertures 33 in the disc. Normally, the conduit 39 is closed by a spring- pressed check-valve 42. On the occurrence of slight shocks, upward movements of the piston cause fluid to flow freely from the chambers 36, 37 to the chamber 27 past the valve 42, while downward movements are resisted by the passage of fluid through a restricting orifice 43 in the valve 42. On upward movements of the piston caused by heavy shocks, fluid in the chambers 36, 37 is forced into chamber 27 until the piston contacts with the disc 34 and closes the apertures 33 therein after which the piston pushes the disc upwardly and compresses the fluid in the chamber 36. A valve 47 prevents excessive pressure. On the return movement the piston separates immediately from the disc 34 and the fluid in chamber 36 expands into chamber 37, while the fluid in chamber 27 flows gradually into chamber 37 through the orifice 43 to damp the movement. A second construction somewhat similar to that shown in Fig. 2 is illustrated in which the check-valve is formed as a slide-valve. In a further construction, the valve 42, Fig. 2, is omitted, the chamber 27 being connected by a valveless conduit to the space below the excess pressure valve 47. Specification 438,998 is referred to. The Specification as open to inspection under Sect. 91 comprises also the construction shown in Fig. 1 (Cancelled), in which a cylinder 1 having an end wall 2 and partition 3 is divided into chambers 7, 8, 9 by pistons 4, 5 connected by a hollow rod 6, an aperture in the piston 4 being frictionally engaged by an obturating tube 11 containing a restricting orifice 12 and carrying the check-valve 13. On compression of the device, fluid flows freely from the chambers 7, 9 into the chamber 8 until the upper end of the tube 11 abuts the wall 2 when the flow ceases and shock is absorbed, as the piston 4 slides frictionally over the tube 11, by the compression of fluid in the chambers 7, 9. On the return movement the tube 11 separates immediately from the wall 2 and the fluid in the chambers 7, 9 expands into the chamber 8 to prevent rebound. On expansion of the device, the valve 13 closes and fluid flows from the chamber 8 through the orifice 12 into the chambers 7, 9 until the orifice is covered by the piston 4, due to the piston sliding frictionally over the tube as the tube abuts the partition 3. The fluid in the chamber 8 is then compressed. On the return movement fluid returns to the chamber 8 through the valve 13. When the aeroplane carrying the shock-absorber leaves the ground, the weight of the landing-wheels causes the piston 4 to move towards the partition 3, the movement being cushioned by closure of the valve 13. This subject-matter does not appear in the Specification as accepted.