GB1036352A - Improvements in viscous type dampers - Google Patents

Abstract

1,036,352. Hydraulic dampers. WESTLAND AIRCRAFT Ltd. March 18, 1965 [April 24, 1964], No. 17001/64. Heading F2S. A viscous damper, e.g. for helicopter rotor systems, comprises a cylindrical casing 1 in which works a piston assembly consisting of an inner plug 11 with a tapered shoulder 27 and an outer sleeve 12 with a skirt 24 which, with the shoulder 27, provides an annular gap 26 the clearance of which can be controlled by relative axial positions of the plug 11 and the shoulder 27. Rotation of the plug 11 within the sleeve 12 to alter the relative positions of the two parts is possible due to the screw-threaded engagement between a shoulder 25 on the plug 11 and the bore of the skirt 24, flats 19, 20 being provided respectively at the upper ends of the parts 11, 12 to facilitate this adjustment. The upper and lower ends of the gap 26 communicate respectively with chambers 29, 31 in the piston rod assembly which are connected by ports 28, 30 to the upper and lower fluid compartments 9, 10 in the cylinder 1. Fluid transfer ports 32 conduct fluid from the gap 26 to an annular chamber 33 formed between the skirt 24 and the cylinder 1 to provide a counterpressure within the chamber 33 so that the wall of the skirt 24 does not distort and the crosssectional area of the annular gap 26 remains constant throughout its length. The two chambers 29, 31 are connected by oppositelyacting pressure relief valves 36, 37, the chambers 9, 10 having ports 38, 39 leading through a non- return ball valve arrangement 41, 42, 43 to a fluid reservoir 40 closed by a cap 44.