Patent GB-793447-A (GB)
Title: Improvements relating to releasable locking mechanism for securing telescopically slidable members
Inventor: KNIGHTS RICHARD NORTHAM
IPC: B66F3/30
Filed: 1954-11-16
Abstract: 793,447. Locking jacks. DOWTY EQUIPMENT CO. Nov. 16,1954, No. 33190/54. Class 69 (2). [Also in Group XXIV] A telescopic strut for an aircraft undercarriage comprises inner and outer tubular members 11, 10, Fig. 2, which are locked in the extended condition shown by a circumferential series of radially-movable headed members 38 floatingly located in rectangular apertures in the member 11, said members 28 being held in a groove 32 in the outer member 10 to lock the strut against thrust by means of an hydraulically-actuated plunger 12. The plunger 12 is slidable on a piston 13 which is fixed relatively to the member 10 and which divides the interior of the plunger into two chambers, one or other of which is supplied with liquid via the piston stem 14. In the retracted position of the plunger a small-diameter portion 49 allows inward radial movement of the heads 38 on contraction of the strut. The members 38 have tails 41 pivotally seated in an inner slide bearing 29 which is secured to the member 11. The member 10 has a stepped bore in which are clamped rings 23 and 24, and an outer bearing 25, the extension of the strut being limited by abutment of a flange 31 against the ring 24. The ring 23 has at each end frusto-conical sur. faces which co-operate with inclined surfaces on the heads 38 so that as long as the plunger 12 is in the retracted position the member 11 may be moved from the extended position shown to a contracted position and vice versa, the heads 38 being deflected inwardly during these movements against the action of a rubber ring 45. The tails 41 are of such length that when the strut is locked the compressive load is taken entirely by the heads 38, flange 31, plunger 12 and ring 23. In a modification, the hydraulically-actuated plunger is replaced by a collar 82, Fig. 5, which slides on the outer telescopic member 63 and is actuated by a link 84, while the headed locking members 76 float in rectangular apertures in the outer member 63 and are resiliently urged by a rubber ring into a groove in the inner telescopic member 61. The collar 82 is urged by springs (not shown) to the locking position shown. To unlock the strut, the collar 82 is moved until a recess therein registers with the heads 76 allowing them to move radially outward on contraction of the strut. In a further modification an hydraulic jack comprising a cylinder 101, Fig. 8, and piston-rod 105 is automatically locked in the extended position by a number of headed members 119 which are located in apertures in the piston-rod and are locked in a groove 113 in the cylinder by a spring-loaded plunger 124, the plunger being moved to unlock the jack by the same fluid used in contracting the jack. In the contracted position shown, the heads 119 are retained against outward movement by a spring-loaded sleeve 132. As the jack is extended (by fluid-pressure on the piston 104) the retaining sleeve 132 abuts a sleeve 111 causing the retaining sleeve to release the members 119 and, as extension proceeds, allow the plunger 124 to expand and push the members 119 into the locking groove 113. To unlock and contract the jack fluid is admitted through a port 103, said fluid acting both to depress the plunger 124 and to shift the piston 104. Specification 743,799 is referred to.