GB615341A - Improvements in or relating to a tappet - Google Patents

Abstract

615,341. Self-adjusting tappets. WEATHERHEAD CO. April 29, 1946, No. 12823. Convention date, May 3, 1945. [Class 80 (iii)] [Also in Group XXVII] A self-adjusting compression link or tappet for automatically taking up slack in a mechanism and particularly applicable to tappets for the cam-operated valves of internal-combustion engines comprises a hollow cylindrical member 22 with a head 18 co-operating with a cam 17 and a plunger member 23 slidable within the bore of the member 22. A differential piston 26 also operates within the said bore and a smaller bore of the plunger to define chambers 24 and 25 which are filled with hydraulic fluid and are in communication through a restricted passage 31. The piston 26 is urged by a spring 36 to force the fluid from chamber 24 to chamber 25 to take up any slack or clearance developing when the compression forces are removed. When the tappet is actuated to lift the valve 12, fluid in chamber 25 is trapped by the restricted passage 31, which may also be controlled by a non-return valve 45, to act as a solid link to transmit the thrust. No appreciable contraction of the tappet due to leak-back through the passage 31 occurs owing to the normally short operating period. With the addition of a non- return valve as in Fig. 2, a small leak passage 47 is still provided to ensure that the length of the tappet is not maintained too long on expansion of the valve rod so that it prevents the valve seating properly.