Tham khảo tài liệu 'mechanism of steam engines part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 104 MECHANISM OF STEAM ENGINES of the cylinder. The latch A is released at some point in the opening movement of the rocker D toward the right. This is accomplished when the rise 0 of the cam lever passes between the cam rolls J J. It is obvious that the length of the cut-off depends upon the position of the cut-off lever K as controlled by the governor. The further to the left the lever K the earlier the cut-off. Fig. 122 shows the rocker D at the extreme right of its motion. Release has taken place and the valve is about to be closed by the pull of Fig. 121. Fig. 122. the dash-pot. The valve closes promptly and the lever B turns to the position shown in Fig. 121. The cut-off lever K is here shown in the position giving nearly the latest cut-off which is about three-quarter stroke of the piston. On the return movement of the rocker D the cam rolls J J raise the cam lever i and the toe c to the engaging position. At the latter part of the movement of the rocker D to the left as the toe c passes lakh J the latter is raised by the toe sufficiently he la Lcli Chen drops by gravity in front of the toe to the n O Hh gear is shown by Fig. 123. The link is interim rod bell crank and the exhaust lever to allow t die time the pressure upon it is heaviest thus MULTIPLE-VALVE ENGINES 105 minimizing the friction loss and giving rapid motion at the time of opening and closing the ports. Separate eccentrics are used for operating the steam and exhaust valves permitting a long range of cut-off and satisfactory adjustment of release and compression. Fig. 123. It is claimed that this gear can be used with satisfactory results on an engine running as high as two hundred or more revolutions per minute 80. Fitchburg Four-valve Engine Fig. 124 shows the head-end steam and exhaust valves and the valve gear for the Fitchburg engine. Fig. 124. Valve Mechanism of the Fitchburg Engine. The stems of the steam valves are attached to sliders having cam grooves. Each slider is moved by a rocker
