GB540083A - Improvements in adjustable distance pieces, tappets and like adjustable members - Google Patents

Abstract

540,083. Valve gear. BUCKLEY, A. B. Jan. 17, 1941. No. 1007/40. [Class 7 (vi)] [Also in Group XXIV] Consists in an hydraulically adjustable distance piece, tappet and like member. As applied to the actuation of a valve stem 25, Fig. 1, by a cam 24, a cylindrical body 10 has a closed end 11 engaged by the cam. Within the body a piston 12 is slidable, the piston and body being urged apart by a spring 23. A narrow neck 14 on the piston carries a closure member 13 between which and the piston is an annular reservoir 15 for liquid e.g. oil. The piston has an axial bore 16 coned at 21 to form a seating for a, non-return valve 19 loaded by a spring 20. The springs 20, 23 bear against the end of an apertured abutment member 17 screwed into the piston and having its aperture in open communication with the bore 16. The reservoir 15 communicates with the bore 16 through apertures 22 and with the atmosphere through an orifice 31. The piston 12 fits the body 10 loosely to provide a restricted passage for the liquid from the pressure chamber 66 to the reservoir 15 when the tappet is under compression. In a modification, the neck 14 on the piston is dispensed with, the closure member 13 being integral with the extended cylindrical wall of the piston. In a further modification, Fig. 3, the piston 34 movable in the body 32 has a piston-rod 35, axial passages 43 in which place the reservoir in communication with the bore 16. The upper end of the rod is screwed into a cover 36 having a cup 37 to engage a pushrod 38. To prevent undue movement of the piston, due to bouncing of the valve, a locking sleeve 40 is provided made of a material having a greater co-efficient of expansion than that of the body 32. Excessive heating of the tappet causes the sleeve to seize in the body. A cup member 41, forming an abutment for the springs 20, 23, clamps a packing ring 42 and surrounds a thimble-shaped member 44 communicating with the pressure chamber 66 through passages 46 and forming an air pocket. The piston may be held against undesired movement by a split pin 47. In a still further modification, (1) the air pocket is formed in the piston-rod, (2) the axial bore in the piston communicates with a plurality of passages each provided with a non- return valve, (3) the restricted passage from pressure chamber to reservoir is provided by a small bore nozzle in the piston and (4) the locking sleeve is extended to near the upper end of the body 32, where it may be clamped by a screw.