Patent GB-452047-A (GB)
Title: Improvements in or relating to hydraulically actuated apparatus and controls, particularly for aircraft
IPC: B64C25/22
Filed: 1935-02-16
Abstract: 452,047. Aeroplane wing spar locking system. AUTOMOTIVE PRODUCTS CO., Ltd., and BROWN, F. V., Brock House, Langham Street, London. Feb. 16, 1935, No. 5107. [Class 4] [See also Groups XXV and XXIX] A hydraulic controlling system of an aircraft comprises a master cylinder unit, a slave cylinder unit, and a valve interposed between the master cylinder and slave cylinder and spring influenced so as normally to assume a position in which operation of the master cylinder tends to actuate the slave cylinder in a preferred or " safe direction, positive adjustment of the valve being required for otherwise actuating the slave cylinder. As applied to the actuation of an aircraft spar locking pin, the master cylinder unit comprises a horizontally arranged cylinder barrel 10, Fig. 1, secured in the lower part of a reservoir casting 11 and protruding therefrom, the barrel 10 being enclosed in a cover 12 attached at one end to reservoir 11 and closed at the other to form a cylinder head 13. Cylinder head 13 comprises an outer shell 30 of light metal and an interior block 31 of phosphor bronze transversely bored at 16 to receive a conical plug 17 forming a change-over valve. Plug 17 is spring-loaded by a spring 18, Fig. 2, and a ball thrust bearing 19. Plug 17 is formed with tangential grooves 20, 21, of which 20 serves to connect a main delivery passage 22, communicating with cylinder 10, to either one of a pair of outlet pipes 23, 24 and groove 21 to connect the other pipe to the reservoir via a passage 25 and an annular space 26 between cylinder 10 and cover 12. A passage 29, Fig. 2, is formed in the cylinder head whereby valve plug 17 is urged against its seating by pressure produced in the master cylinder. Wall 32 of reservoir 11 is formed with a bore 33 coaxial with cylinder 10 and accommodating an auxiliary piston 34 connected to main piston 38 by a hollow sleeve 35 adapted to provide a seating for actuating push rod 37. Piston 34 is provided with a resilient packing ring 39 and piston 38 with a flexible cup 40 normally held in position by a spring 41 bearing on a cupshaped thrust member 42. Piston 38 is formed with a number of liquid passages 43 communicating with a V-shaped annular groove in rear of the cup 40, the groove accommodating a valve ring 45. Thrust member 42 is shaped as shown to permit ready collapse of the cup 40 on the return stroke of.piston 38, and thus to provide room for release of valve ring 45 whereby the cylinder may refill with fluid from reservoir 11 through passage 46. A breather hole or holes 47 is or are formed in the wall of the master cylinder immediately in advance of the rim of cup 40 thus serving to equalize the pressure in master cylinder 10 and reservoir 11 when the piston is completely retracted. Spring 41 bears at its other end upon a differential delivery valve 48 adapted to maintain a slight pressure in the slave cylinder or cylinders. Reservoir 11 is fitted with an air inlet valve 51. The master cylinder is shown as installed in the leading edge of an aircraft wing 52, push rod 37 being actuated by a curved lever 53 pivotally carried by the reservoir casting. Downward movement of lever 53 is limited by a toggle linkage 57 fitted with a tension spring 58 adapted to raise the lever automatically to the position in which piston 38 is completely retracted. Control valve 17 is operated by a push rod 62, Fig. 2, which is urged by a compression spring 63 to the position in which valve 17 is in the "safe" position, i.e. that position in which actuation of lever 53 tends to move the plunger of the slave unit to the spar locking position. The master cylinder may actuate more than one slave unit in which case the delivery pipes are branched as shown. The spar pin unit comprises a barrel 70 in which is slidable a pin bolt 71, one end of which constitutes a plunger 59 fitting in a bore 74 formed in a flange 75 securing barrel 70 to a fixed part 73 of the wing, and serves in the position shown to secure the folding part 72 of the wing. Bolt 71 is provided at its other end with a squared portion 76 screw-threaded at 77 to coact with a manually operated emergency retracting nut 78 normally held against rotation by a cotter pin 102. The adjacent end of barrel 70 is closed by a screwed cap 79 having a squared hole for the passage of bolt end 76 and providing a bearing for a compression spring 85, the other end of which bears on a "tail" piston collar 86 secured to pin 71. A "head" piston collar 89 is attached to bolt 71 immediately adjacent the plunger portion 59. The fluid space between the two pistons is divided into chambers 91, 92 by a collar 93 slidably mounted both with respect to barrel 70 and bolt 71, its axial movement being limited by engagement of locking screws 95 with the sides of an annular groove 94 formed in its periphery. Collars 86, 89 and 93 are provided with resilient annular cupwashers of Y-shaped cross-section as shown. Chambers 91, 92 communicate with pipes 23 and 24 respectively. Owing to the axial play of collar 93 the first part of the stroke of the master cylinder is effected at low pressure, this stage lasting at least until the rim of cun 40 has passed the breathing aperture or apertures 47. The spar pin unit is provided with dirtexcluding means comprising an extensible boot 83 clipped at one end to barrel 70 and at the other secured to a collar 81 engaging the screwed end 76 of the spar bolt by means of a square hole. Collar 81 is located axially by a ring 82 connecting it to nut 78.