GB1143871A - - Google Patents

Abstract

1,143,871. Constant-force hydraulic springs. ZENTRALE ENTWICKLUNG UND KONSTRUKTION ZEK HYDRAULIK VEB. 3 Jan., 1967, No. 329/67. Heading F2S. A substantially constant-force hydraulic spring comprises a liquid-filled chamber 1 which is closed by a member 2 having a tubular extension 2a, and a piston 6a which has extensions 5, 6 which extend through upper and lower guide bushes 3, 8 in the extension 2a and against which a high pressure seal 7 bears, the bore of the extension 2a tapering conically inwards along the whole, or part, of its length and communicating, through a bore 2b, with the space within the chamber 1. The piston extension 6 passes through a screw cap 4 which secures a stripper ring 5 to the guide bush 3, the lower bush 8 being secured to the tubular extension 2a by a screw cap 9. The effective cross-section of the seal upon which the fluid pressure acts decreases as the piston is moved progressively inwards. In a modification, Fig. 2 not shown, a guide tube (13) is secure between the end plates (11, 12) of liquid-filled housing (10) and a piston (20b) has an upper extension (20a) which passes through a seal in the end plate (11), and a lower extension (20c), upon which are secured a high pressure seal (22) and a bearing bush (23) by means of a nut (24), the bush (23) sliding in the lower part of the guide tube (13) which is of cylindrical shape. The piston (20b) with a high pressure seal (21) works in a downwardly tapering part of the guide tube. The housing (10) is sealed by high pressure seals (15, 16) which are backed respectively by supporting rings (17, 18). The effective cross-section for the spring force is equal to the area of the incoming seal 21 minus the area of the outgoing seal (22) which is constant. Only a slight change in the area of the seal (21) is effective to cause a considerable change in the spring force which can be arranged to have a horizontal or even descending characteristic. Bores (13a) connect the tube space between the seals (21, 22) with the space (14) within housing (10), and the space within the guide tube (13) around the upper end (20a) of the piston and the lower tube space may be interconnected e.g. to equalize the pressure.