Patent GB-347114-A (GB)
Title: Improvements in or relating to valve gear for fluid pressure engines, pumps and the like
IPC: F01L31/16
Filed: 1930-01-21
Abstract: 347,114. Engine valve gear. HOLMES, V. W., Rahoy, Lenzie, near Glasgow. Jan. 21, 1930, No. 2018. [Class 122 (ii).] A cam gear for engines, pumps, compressers and adapted to vary the period of the valve opening, while ensuring the time of opening and closing in accordance with requirements, comprises a rotary cam which imparts motion to a lever adapted to oscillate a cam to actuate a valve. The lever fulcrum is adjustable to vary the valve action. In the diagram, Fig. 1, a rotary, constant-velocity cam 1 actuates a bell-crank 2a, 2b, the fulcrum 5 of which is adjustable along an arc a. The arm 2b oscillates through a pin-and-slot connection a, a cam 3 on the axis of a shaft 4 which cam engages a roller 10 to operate a valve 9. The shaft 4 rotates at half crank-shaft speed. Moving the fulcrum to the left delays the cut-off, the admission remaining the same. Reversal is effected by displacing the fulcrum clockwise, the opposite end of the cam surface then becoming effective. The use of two rollers 6 obviates the use of a spring to maintain contact between the roller and cam. The arms 2a may be off-set and engage side-by-side rotary cams with slightly-different profiles to ensure continuous roller contact, a construction suitable for double-acting engines necessitating two levers and two inlet valves. Adjacent arms may be adapted to engage one roller. In the embodiment shown in Figs 6 and 7, a rotary cam 11 and two oscillating cams 12, 13 are used. An arm 14 on a shaft 15 carries a roller engaging cam 11 ; the shaft 15 carries an arm 16 which actuates the cam 12 to operate the valve tappet 21. The cam shaft 22 rotates at half speed, has an extension carrying the cam 13, and is supported by sleeves 24, 26 mounted in the gear-case 25. Counterbalanced arms 31, 32 support the shaft 15, the arm 31 is integral with the sleeve 26, and the arm 32 with a sleeve 29. The arms 31, 32 carry a second shaft 33 provided with arms 34, 35. The cam 11 operates the arm 34 and the arm 35 operates the cam 13, which actuates a valve tappet 40 set at 90‹ to the tappet 21. The shaft 33 also carries an arm 41 carrying a spring-pressed member 42 which engages the arm 14 and keeps the rollers 17, 36 on the cam 11. The end of the arm 14 may be shaped to dispense with the spring 43. The sleeve 26 is angularly adjusted to effect control from a locomotive cab by a shaft 45, worm gearing 46a, 46b, and toothed gearing 48, 49. The engine has two exhaust valves operated by a cam 50 the timing of which is altered for reversal. The cam 50 has helical splinings 56 engaging a sleeve 55 which is also splined to engage grooves on the shaft 22. The sleeve 55 is longitudinally moved by a member 58 which is constrained from turning by pins 59 which also engage slots in the sleeve 26. A modification is described to permit coasting. The exhaust valves are operated by levers which are moved by a second lever operated by a cam on the sleeve 26 to hold the valves open. The levers operating the oscillating cams may be slotted and the cam shaft extend from end to end of the gear case. In a modification a single lift cam rotating at engine speed is provided. The rotary and oscillating cams need not be concentric.