Patent GB-612422-A (GB)
Title: Improvements in and relating to shock absorbers
IPC: B64C25/60
Filed: 1945-08-24
Abstract: 612,422. Hydro-pneumatic shock-absorbers. KATZ, M. Aug. 24, 1945, No. 21813. Convention date, Oct. 24, 1944. [Class 108 (iii)] In a telescopic hydraulic shock-absorber for aircraft of the kind described in Specification 599,859, comprising three chambers, two 61, 34 of which are filled with liquid and communicate with one another through the valve-controlled ports 17 of a piston 15, while they communicate with a third chamber 1<SP>1</SP> which contains liquid and an elastic device tending to expand.the shockabsoiber, on the one' hand through calibrated damping orifices, and on the other hand through additional orifices 49 of wide section which are adapted to be automatically masked or uncovered by a closing sleeve 20, displacement of which is produced by relative movement of the telescopic elements 1, 6 of the shock-absorber, the closing sleeve is maintained in orifice-closing position by mechanical locking means controlled by relative movement of the elements 1, 6, and under the action of a return spring uncovers the orifices 19 after absorption of the landing shock, only when the locking means have been retracted. In the construction described, the elastic device comprises compressed air above the liquid in the chamber 1<SP>1</SP> and the damping orifices are formed by a splined rod 25 secured to the base of the cylinder 6 forming the lower of the telescopic elements in conjunction with an orifice 18 in the piston 15. The mechanical locking means comprises balls 13 located in apertures in an extension 11 of the piston 15 and engageable with recesses 23 in the sleeve 20. A ring 32, having apertures 33, is slidable in the bore of the cylinder 6 and has an inclined inner surface engageable with the balls 13. The sleeve 20 is mounted within the extension 11 and is upwardly urged into an orifice-opening position by a spring 22. The sleeve 11 is adapted to be drawn into the closing position by means of an abutment 29 on the rod 25 which is engageable with projections 24 on the sleeve 11 on complete extension of the shock-absorber. The abutment 29 is slidable upwards on the rod 35 against a spring 27 which is of greater strength than the spring 22. Operation.-Following take-off, the shockabsorber expands fully and the abutment 29 engages the projections 24, thus drawing down the sleeve 11 to cover the orifices 19. At the moment of landing, damping occurs by flow through the orifice 18 and to a certain extent by flow from the chamber 34 through orifices 35 formed in the wall of the space 1<SP>1</SP>. On upward movement of the cylinder 6 the ring 32 is carried upwardly by friction and drives the balls 13 into the recesses 23, thus locking the sleeve 20 in the closing position. During this action the sleeve is maintained in position by the abutment 29 since the spring 27 expands on contraction of the elements 1, 6 before the weaker spring 22 commences to expand. On expansion, when the landing shock has been absorbed 20 are released. Flow then can take place through the orifices 19. Due to closing of the valve 31, damping on expansion movements occurs through the orifices 35. The ring 32 may alternatively be displaced by inertia or by hydraulic pressure instead of by friction and the sleeve 20 may be urged upwardly by gravity or other means in lieu of the spring 22.