Patent GB-844860-A (GB)
Title: Improvements in or relating to valve lapping apparatus
Inventor: CROFT CHARLES THOMAS
IPC: B24B15/02
Filed: 1956-10-31
Abstract: 844,860. Lapping valve seats. DEWRANCE & CO. Ltd. Aug. 20, 1957 [Oct. 31, 1956], No. 33310/56. Class 60. An apparatus for lapping opposed valve seats comprises a pair of laps which are connected to supports carried by a mounting such that one lap is movable towards and away from the other and is spring-controlled for movement to an inactive position to facilitate location of the apparatus between the valve seats and removal therefrom, the mounting being adapted to be connected with actuating means to effect movement thereof relative to the valve seats to effect lapping of the seats and with a source of fluid pressure to urge and maintain the laps in such lapping relation. In the embodiment shown in Fig. 1, lapping discs 1, 2 are provided with abrasive element 23, the disc 1 being mounted on a square-sectioned projection 8 formed on the cover 9 of a cylinder 7 within which a piston 14 is movable under fluid pressure to force the disc 2, mounted on a square-sectioned rod 10, away from the disc 1 thereby compressing a spring 13 which moves the disc inward when the pressure is relieved. The discs 1 and 2 carry rollers 24 to locate the discs within the valve bodies ; the diameter of the roller pitchcircle is such that a clearance is left between the peripheries of the rollers and the interior of the valve seats so that in operation the laps are capable of limited gyratopy movement over the seats during the lapping action, which is effected by a ratchet device. This device comprises teeth 18 engaged by a pawl 19 attached to a member 20 which is oscillated by an adjustable rod 22 either manually or by an eccentric pin 27, Fig. 4, carried by a disc 28 which is driven by a pneumatic drill 29, rigidly mounted on the valve body flange 30. The fluid pressure to actuate the piston 14 is supplied through a connection 15 from a compressed air source a manually-operable regulator 26 and gauge 25 are provided for pressure adjustment. In the embodiment shown in Fig. 5, the fluid pressure to urge the laps into contact with the valve seats 3, 4 is supplied through a tubular connecting rod 15a which is rigidly connected to the lap carrier at its lower end and to a source of fluid pressure at its upper end. A gyratory motion is imparted to the lap by the member 15a which is actuated by a motordriven eccentric housing 35 and pin 37. The vertical movement of the laps may be varied by adjusting the angular position of an eccentric bush 36 within the housing 35, whilst the extent of lateral movement can be adjusted by the location of a pivot-bush 42 lengthwise in a slot 43 in a bracket 32 on which the driving gear 33, 34 of the housing 35 is mounted. The apparatus shown in Fig. 7 is adapted for manual operation by a handwheel 44 which can be fitted at will either to a shaft 34a or a sub-shaft 45 corrected by gears 46, 47 to the shaft 34a. An hydraulic pump 48 serving as the source of fluid pressure to move the laps to operative position is operated by a cam 49 on the shaft 34a. In a further modification, the piston operating in the fluid cylinder consists of an asbestos packing washer clamped between the piston body and a cap, in place of the cap leather piston shown in Fig. 5.