GB489618A - Improvements in hydraulic vibration dampers mounted on aircraft - Google Patents

Abstract

489,618. Hydraulic vibration - dampers; stuffing-boxes. BECHEREAU, L., and CARROUEE, R. Jan. 28, 1937, No. 2556. Convention date, Jan. 30; 1936. [Class 108 (iii)] [Also in Group XXVI] In a hydraulic vibration-damper, particularly for use on aircraft, comprising one or more closed chambers completely filled with liquid, a part or parts formed in the wall or walls of the chamber or chambers, or the surrounding wall or walls of the chamber or chambers, is or are constituted by flexible or elastic material for compensating for the variations in volume, due to the variations in temperature, of the liquid enclosed in the damper. The vibration-damper shown in Fig. 1, of the type described in Specification 461,353, comprises a reservoir 1 with end stuffing- boxes through which passes the rod 2 of a piston reciprocable in a cylinder 4 housed in the reservoir, the cylinder being slidable .on the rod 2 between two stops 16 which it engages alternately to establish communication between the reservoir and one of the two working chambers of the cylinder. Vibrations are damped by restricted flow of liquid past the piston. The liquid-expansion compensating device comprises a flexible sleeve 30 surrounding, and fixed at its edges to, a part of the reservoir having one or more orifices 31. A metal sheath 32 may protect the sleeve. In another construction, Fig. 2, the reservoir 1 communicates through end orifices 23 with flexible chambers 24, 25, e.g. of corrugated rubber tubing. The reservoir may be dispensed with and the expansible chambers connected by a single conduit. For damping vibrations of an aircraft aileron, the arrangements of a vibration-damper or dampers according to the invention are similar to the vibrationdamper arrangements shown in Figs. 11, 12 of Specification 461,353. The Specification as open to inspection under Sect. 91 comprises also the vibrationdamper construction shown in Fig. 1 (Cancelled) which is similar to that described above with reference to Fig. 1, vibrations being damped, however, in addition to a restricted liquid flow past the piston, by flow through an auxiliary conduit 5 regulated by a thermostatically-controlled valve 6 by which changes in the viscosity of the liquid due to changes in temperature are compensated for. The reservoir communicates through orifices 8 with the piston-rod stuffing-boxes which contain rubber &c. packing-rings 10, 11 pressed against the rod by a spring 13 acting through a sleeve 14 on metallic annular members 12 bearing on the rings., On expansion of the liquid in the damper the rings 10, 11 yield against the action of the spring 13, the pressure of which is adjustable by means of a cap 15 which screws on the end of the reservoir and maintains the parts in alignment. In modifications, (a) the rings are enclosed in an annular member formed integral with the sleeve 14; (b) another spring acts on the rings in opposition to or in conjunction with the spring 13; and (c) an annular, flexible membrane is provided inside the cap 15 to prevent leakage and to assist in absorbing excessive expansion of the liquid. In the construction shown in Fig. 5 (Cancelled) the membrane 21 only is adapted to compensate for liquid expansion and for this purpose is in communication with the reservoir through channels 22 and the orifices 8. Another construction, without liquid-expansion compensating means, is also described in which the working cylinder is stationary and spring pressed annular valves effect communication between the cylinder working chambers and the 'reservoir. This subject-matter does not appear in the Specification as accepted.