Patent GB-485467-A (GB)
Title: Improvements in or relating to liquid pressure remote control systems
IPC: F16K31/12
Filed: 1936-11-17
Abstract: 485,467. Aircraft alighting gear. AUTOMOTIVE PRODUCTS CO., Ltd., and PARKER, S. M. Nov. 17, 1936, No. 31469. [Class 4] [Also in Group XXIX] In a liquid-pressure remote-control system having a plurality of double-acting motor units fed from a common source of pressure liquid, valves are provided independently of said motor units but mechanically connected therewith, whereby movement of the motor units in one direction takes place in predetermined automatic sequence, and movement of the motor units in the opposite direction takes place in reverse automatic sequence ; for example, when there are two motor units A and B, forward movement of B takes place automatically when A has completed its forward movement, and the reverse movement of A takes place automatically when B has completed its reverse movement. As applied to aircraft, an undercarriage 10, Fig. 1, is retracted and lowered by a double-acting jack 11, and the door 13 of a compartment 12 formed in the wing or fuselage for accommodating the undercarriage when retracted is operated by a double-acting jack 15; the system includes a reservoir 22, pump 16 and main distributing valve 18. A valve 23 urged to " off " position by a spring is moved to " on " position by the door 13 when the latter is completely open ; similarly, a valve 24 urged to " off " position by a spring is moved to "on" position by the undercarriage 10 when this is completely retracted. When, with the door 13 closed and the undercarriage 10 retracted, the valve 18 is moved to the position shown, pressure liquid from the pump 16 passes by pipe 19 to the upper end of the jack 15 to open the door 13, the lower end of said jack exhausting through valve 24, pipe 20 and valve 18; the valve 23 prevents passage of pressure liquid to the upper end of the jack 11 so that the undercarriage 10 cannot be lowered ; the upper end of the jack 11 is put to exhaust through valves 23 and pipe 29, and the lower end of the jack 11 is put to exhaust through pipe 20 and valve 18. When the door 13 has completely opened, it moves valve 23 to the " on " position, admitting pressure liquid to the upper end of the jack 11 which is simultaneously cut off from the exhaust connection 29, the lower end of the jack remaining to exhaust through 20, 18. The undercarriage thus moves down ; the valve 24 is moved by its spring to the " off " position as soon as the undercarriage releases it; the lower end of the jack 15 now communicates through valve 24 not with exhaust line 20 but with exhaust line 29. When the valve 18 is moved to its opposite position, the carriage 10 is retracted and when fully retracted it moves valve 24 to the " on " position, and then and only then, is the jack 15 operated to close the door 13. In a modification, the compartment for the accommodation of the undercarriage when retracted is fitted with a pair of doors, the arrangement being such that the undercarriage is lowered when, and only when, both doors have completely opened ; the system may be duplicated . so as to operate simultaneously two undercarriages arranged one on each side of the aircraft, each undercarriage folding into a compartment fitted with two doors ; each undercarriage may be actuated by two or more jacks working in parallel. The undercarriage may be retained in retracted position by a hydraulically releasable catch device connected to that pipe line which supplies pressure liquid for lowering the undercarriage. The catch member for the undercarriage may be so arranged as to actuate the valve 24 to ensure that the undercarriage is definitely locked before the compartment door or doors can be closed ; as shown in Fig. 4, the undercarriage member 10 carries a pin 39 which on retraction of the undercarriage acts on a cam face 42 of a lever 40 pivoted at 41 so as to force the lever 40 aside against the restraint of a spring 43, thus allowing the pin 39 to engage a notch in the lever ; a member 44 is freely pivoted on the pin 39 and as the parts assume their locking position, the free limb of this member is engaged by the surface 42 whereby the member 44 is caused to actuate the valve 24 to permit pressure liquid to pass to the jack for closing the compartment door. Where an electrical or other indicating device is used to advise the pilot when the undercarriage is retracted, the switch or equivalent by which the indicating system is worked may conveniently be actuated by the rod of the valve 24.