Patent GB-712321-A (GB)
Title: Improvements in or relating to flutter damper for aircraft
IPC: B64C13/00
Filed: 1951-06-15
Abstract: 712,321. Rotary dashpots. HOUDAILLE-HERSHEY CORPORATION. June 15, 1951 [Feb 5. 1951]. No. 14212/51. Class 108(3) A rotary dashpot comprises a housing 17, Figs. 2 and 5, having a cylindrical chamber A into which project abutments or partitions 31, 31. a rotary shaft 23 having wing-like pistons 29. 29. a replenishing chamber 79 in the housing 17 axially beyond one end of the shaft 23, a check-valved passageway between the chambers 79 and A, and means for impressing pressure on the fluid in the chamber 79. In the construction.,shown in Figs. 2. 5, the partitions 31 are held by pins 38, 39 relative to the housing 17. The dashpot is adapted to fit within, and is in alignment with. the pivot axis of. an aircraft aileron, elevator, flap &c. Brackets 20 rigid with the housing 17, are bolted to the aileron &c., and a lug rigid with a boss 25 splined to the shaft 23. is bolted to the end-surface of the wing or tailplane. The wings 29 and partitions 31 define pairs of opposed working chambers 32, 32 and 33, 33. A chordal-shaped damping orifice 64 is formed in a hollow cylindrical member 60 which is retained against an abutment 62 within the bore of the shaft 23 by means of a threaded plug 53. The orifice 64 opens into a wider chordal slot 65, which itself opens into an annular peripheral recess 67 in the member 60. Ports 51 in the wall of the shaft 23 -connect the recess 67 with the chambers 33. Similar ports 50 in the shaft 23 connect the chambers 32 with the interior of the bore in the member 60. A rotary valve 68 disposed within the member 60, has a wider chordal slot 70 which connects the interior of the member 60 (via a bored-out portion 69 of the valve 68) with the orifice 64. The valve 68 may be rotated by a spindle 71 in order to cut-off the orifice 64 and so vary its damping effect. Acting in series between the valve 68 and spindle 71 is a thermostatic element 71a. The replenishing chamber 79 is connected by ports 30 and ball valves 81, with the working chambers 32, 33. Pressure in the chamber 79 is maintained by the action of a piston 85 loaded by a spring 87, in a further chamber 82. Liquid may be forced under pressure into the chamber 82 via a rubber check valve 97, spring-loaded on to a convex seating 98, formed in a plug 92 screwthreaded within the rod of the piston 85. Normally the outer end of the plug 92 is closed by a screw plug 101 and sealing ring 102. The position of a flat 99 in relation to the face of the end plate 84 of the housing 17, indicates the amount of liquid in the chamber 82. The chamber 79 may be charged direct, through a valve assembly (not shown) consisting of a plug and rubber check valve similar to the plug 92 and valve 97. The space between the rubber check valve and a screw plug in the wall of the housing 17, is connected by a port (not shown} with the space 82. A plug 124 having a rubber sealing tip may be screwed in order to bleed air from the shock absorber and normally seals ports 122, 123 (123 not visible in Fig. 2) connected with the chambers 79, 82 respectively. Air which collects in the working chambers may pass via ducts 128, 129 and 130 to the space 79. In the modification shown in Fig. 11 (part), liquid in the replenishing chamber 79 is directly under pressure from a spring-loaded piston 192. The piston rod 201 is grooved at 203, in order to indicate by reference to the housing end-wall 200, the volume of liquid in the chamber 79. Air collecting in the working chambers passes via ducts 209, 210 to a plug 208. The duct 210 may be opened out to a larger diameter, and may then be plugged by means of a pin 211 formed with a suitable air-bleed groove.