| 摘要 |
1473653 Cam followers BRITISH LEYLAND UK Ltd 1 Aug 1974 [18 Aug 1973] 39137/73 Heading F2K In a valve operating mechanism, for an overhead cam-shaft I.C. engine, a tappet 5, between a cam 4 and valve 1, is in two nested parts 10, 15, the upper, i.e. foot part 15 engaging the cam 4 and being in screwed engagement at 7 on the valve stem 1 and the lower, i.e. spring retainer part 10 slidably and non-rotatably mounted on the valve stem 1, the clearance between the cam 4 and valve stem 1 being adjustable by rotating the foot 15 relative the spring retainer 10. To effect such adjustment, complementary radially interengaging teeth 14, 19 on the foot 15 and retainer 10 respectively are first disengaged by axially downwardly depressing the spring retainer 10 against the valve spring 6 by a tool such as a screw-driver blade inserted in one of a number of slots 11a on the retainer 10 (Fig. 4, not shown) whereby the foot 15 may be freely rotatably adjusted on the valve stem 1 relative the retainer 10, the foot 15 and retainer 10 being marked with a datum arrow and scale graduations respectively corresponding to a given axial adjustment of the foot 15 on the valve stem 1, after which, on release of the screw-driver blade, the radial teeth 14, 19 are re-engaged by the valve spring 6 to lock the two-part adjustable tappet 5 in its new adjusted setting on the valve 1. To relieve the radial locking teeth 14, 19 of unnecessary stress in preventing rotation of the tappet unit on the valve stem, the threaded portion 23 of the foot 15 may be axially split at 24 and externally tapered at 21 to seat in a complementary tapered seat in the spring retainer 10 so that it can radially grip the thread of the valve stem 1 under the action of the valve return spring 6. Alternatively, Figs. 3 and 4 (not shown), the threaded stem portion (32) of the foot 15 may be cylindrical and transversely split at (33) to allow for axial compression of the stem portion (32) against a shoulder (31) in the retainer, under the action of the valve spring 6, so that it can axially grip the thread of the valve stem 1, i.e. by reduction in the pitch of the internal teeth 16 on the foot 15. |
