Patent GB-798811-A (GB)
Title: Improvements in or relating to vehicle suspensions
Inventor: MARTIN GAVIN PATRICK BLANDY
IPC: F16F9/096
Filed: 1955-08-25
Abstract: 798,811. Hydro pneumatic sliock absorbers. WOODHEAD & SONS, Ltd., J. Aug. 1, 1956 [Aug. 25, 1955], No. 24487/55. Class 108(3) A telescopic suspension unit for a vehicle comprises a working chamber a containing a floating piston, diaphragm, or similar pressure responsive member 41, to one side of which a pneumatic fluid is supplied, means whereby relative movement between the sprung and unsprung vehicle parts (not shown) will result in an hydraulic fluid being pumped into the chamber a at the other side of the floating piston &c. thus tending to effect extension of the unit, and means adapted to permit excess hydraulic fluid to escape from the chamber a to a reserve chamber b when the unit is extended to a predetermined degree the hydraulic fluid then being available for re-circulation. As shown, the member 41 comprises a flexible diaphragm. A piston 20 carried by a piston rod 19 rigid with a cylinder 10 which defines the chamber a, is reciprocable in a cylinder 21. The latter is closed at its upper end by a head 22 which is slidable around the piston rod 19 and within the cylinder 10, and is closed at its other end by a head 27. The chamber b is defined by an outer cylinder 25 concentric with the cylinder 21 and rigid with both of the closure heads 22 and 27. Three non-return valves 30, 31, 32, are formed respectively in the piston 20, the head 22, and the head 27. A tube 46 concentric with the cylinder 21 is also concentric with, and slidable within, a bore 44 formed concentrically within the piston rod 19. The tube 46 is obturated to a greater or less extent by a tapered metering rod 45 rigid with an apertured head 17 disposed with the chamber a. The suspension effect of the pneumatic fluid above the diaphragm 41 is supplemented the action of a coiled suspension spring 52. In operation, when the vehicle starts from rest, due to leakage of oil while the unit has not been reciprocating, the unit is in its fully compressed condition. Reciprocation due to suspension movements causes liquid to be pumped successively through the valves 32, 30, and 31, into the chamber a to cause the unit to be progressively extended. When the extension reaches a predetermined degree, the metering rod 45 is sufficiently extended from the tube 46 to permit liquid to enter the tube 46 from the chamber a and flow back to the chamber b, and no further extension takes place. In a modification (Fig. 2, not shown), the piston rod 19 is solid, and the metering rod 45 is disposed externally to, and parallel with, the piston rod 19, and obturates a port in the head 22 which directly connects the chamber a with the chamber b. In a further modification (Fig. 4, not shown), the diaphragm 41 is replaced by a floating piston (which may be of plastics) sliding in a cylindrical extension of the chamber a. The metering rod 44, instead of being fixed in relation to the chamber a, may be rigid with the floating piston. In a further modification, (Fig. 1, not shown), instead of the metering rod 44, a series of ports are formed in the wall of the cylinder 10. These are so positioned that when the predetermined degree of extension is reached, they are progressively uncovered by the sliding movement of the head 22 relative to the cylinder 10, the liquid thus being permitted to pass back to the chamber b. The pneumatic chambers defined by the respective diaphragms 41 of a plurality of the units on a vehicle, may be connected to a centrally disposed pneumatic reservoir. The spring 52 may alternatively be disposed internally of the unit.