Patent GB-697937-A (GB)
Title: Improvements in self-centering means for aircraft castorable landing wheel mountings
IPC: B64C25/50
Filed: 1951-09-27
Abstract: 697,937. Springs. DOWTY EQUIPMENT, Ltd. Sept. 27, 1951 [June 22, 1951], No. 22613/51. Class 108 (iii). [Also in Group XXXIII] An aircraft castorable landing wheel mounting comprises a castor shaft carrying the wheel, fixed journal means supporting and guiding said shaft for rotation continuously through a 360 degrees range, crank means fixed to said shaft eccentrically thereof for rotation conjointly therewith, means reciprocable transversely of the castor shaft axis and engageable with said crank means throughout a predetermined angular turning of the same to either side of a central position at which the wheel is in fore and aft alignment and disengageable from said crank means throughout the remainder of its turning range, and centring spring means reacting oppositely upon the reciprocable means to return the same to an initial position corresponding to the centre position of the crank means and hence to the fore and aft position of the wheel. In an application to a castoring nose-wheel wherein the Figure shown is a horizontal section through the upper part of the leg, the castor shaft 15 is apertured to receive a tubular casing 28 within which is slidably mounted a plunger or crank 27 loaded by springs 28a. An axial slot is provided in the wall of the plunger 27 for engagement by a peg (not shown) to prevent rotation of the plunger about its own axis. The casing 11, wherein the castor shaft 15 is rotatably mounted, comprises a housing for a centring spring box 25 wherein a reciprocable forked member 31 and a partition member 32 are bolted to a tube 34 slidably mounted at its ends in fixed cylindrical guides 35. Springs 36 are positioned between the ends of the guides 35 and the partition member 32, the inner end of each spring seating on a cup-shaped member 38 which may be adjusted to vary the loading of the spring by means of a bolt 39 and adjusting nut 41. The forked member 31, which is external of the tube 34, is formed with a vertical groove 42 flanked on either side by a concave cam surface 43 and the plunger 27 is formed with a radiused head that seats within the groove 42. In operation, when the wheel and shaft 15 castor, the end of the plunger 27 will act on the member 31 and the spring box mechanism to compress one or the other of springs 36 so that when the load is removed from the wheel, as after take-off of the aircraft, the spring box will return the axle and wheel to its normal fore and aft position. This action will take place over a limited range of angular movement only and when this is exceeded, as during manoeuvring of the aircraft on the ground, the plunger 27 will become disengaged from the groove 42 leaving the wheel to castor freely to one side of its central fore and aft position. When the wheel is forcibly returned to this central position the head of the plunger 27 will ride up the appropriate track 43 against the action of the springs 28a which will automatically re-engage the plunger with the groove 42 when they become re-aligned. In an alternative embodiment, Fig. 3 (not shown), the cup-shaped members 38 are dispensed with and the springs 36 seat on a disc secured to the head of the bolt 39 and secured to the disc is a shock-absorbing buffer which seals the disc with respect to the tube 34 so that air trapped between the disc and the partition member 32 cushions the centring movement.