GB1305311A - - Google Patents

Abstract

1305311 Shock absorbers JONAS WOODHEAD Ltd 13 April 1970 17450/70 Addition to 1267508 Heading F2S The main piston 8 of the shock absorber of Specification 1,267,508 is provided with a passage 13a and a valve element 61 which maintains the passage 13a closed or substantially closed except when, during movement of the main piston 8 in the direction out of the main cylinder 1, the pressure across the main piston 8 exceeds a predetermined value whereupon the valve opens. The main piston 8 is connected to a subsidiary piston 9 which slides in a subsidiary cylinder 25 at the beginning of the contraction stroke and at the end of the extension stroke, providing a threshold resistance to initial inward movement of the main piston 8 which is greater than the resistance to its final outward movement. When the main piston 8 begins to move into the cylinder (R.H.S. of Fig. 2) the 0-ring 38 seats against the upper part 34 of the subsidiary piston 9 and so fluid between the pistons can only escape to the back of the piston 9 by way of bleed notches 44 (optional). When the subsidiary piston 9 reaches the end of the cylinder 25, the threshold resistance is eliminated, and further inward movement of the piston 8 is regulated by valve elements 15, 16. Outward movement of the piston 8 is controlled by the blow-off valve element 61 and bleed notches 17 until the subsidiary piston 9 enters the subsidiary cylinder 25 (L.H.S. of Fig. 2), where the 0-ring 38 allows substantially free flow of fluid past the piston 9 and out of the subsidiary cylinder. The working fluid is an emulsion of liquid and gas under pressure.