GB560048A - Improvements relating to shock absorbers - Google Patents

Abstract

560,048. Shock-absorbers. DOWTY, G. H. Jan. 17, 1939, Nos. 26719, 26720, 26721 and 26722. Divided out of 560,047. [Class 108 (iii)] Means for affording damped resilience comprise a pressure-tight chamber 5, a plunger 7 slidably extending into the chamber to afford resilience due to the elastic restoring forces of liquid filling the chamber and compressible by plunger movement under load, a head 12 fixed to the plunger and slidable within the chamber, and flow resistance means such as 16, included entirely within the headed plunger and movable therewith to afford energy dissipation by passage of liquid therethrough during plunger movement. In the construction shown in Figs. 1 and 2 applied to an aircraft undercarriage, the chamber or cylinder 5 is pivoted at 6 to a leg or strut 1, and the plunger 7 is pivoted at 11 to an arm 2 which carries the landing wheel 4 and is pivoted at 3 to the leg 1. When the plunger is forced into the chamber by increasing load on the wheel, the liquid in the chamber is compressed and exerts a resilient restoring force on the plunger ; at the same time the movement is damped by the flow of the liquid through apertures 15, 13 in the plunger head ,12, this flow being controlled by a shuttle valve 16 having a limited annular clearance in a recess 14 in the head. During the upward movement of the plunger and head, the liquid is forced past this annular clearance and the movement is damped accordingly. On the rebound stroke, when the head is moving downwardly, the valve 16 is carried upwards until it seats itself on a plug 15A with its stem 16A within an aperture 15 in the plug. More resistance to flow is provided on this rebound stroke, but a complete sealing of the passage is prevented by the provision of ducts 15B on the valve seating of the plug ; alternatively, or additionally, ducts may be provided on the upper face of the valve 16. The pressure, when the liquid is fully compressed, may be of the order of 40,000 to 50,000 lbs. per square inch. In a modification, Fig. 3 (not shown), the plunger is a differential one and has two slightly different diameters fitting in the two ends of the chamber 5, the head 12 being situated at the junction of the two diameters of the plunger. According to the first Provisional Specification, a relatively small volume of gas may be used with the liquid, the chamber may contain or be lined with rubber or the like, a series of shock-absorbers may be used, the piston of one forming the chamber of the next and the chamber may be reinforced by wire wrapping ; and according to the third Provisional Specification, the plunger operates against a compression spring and is hollow so as to form a second chamber in which liquid is compressed during the latter part of its stroke.