Patent GB-530446-A (GB)
Title: Improvements in or relating to valve gear for fluid pressure engines, such as locomotive engines
IPC: B61C17/12
Filed: 1939-06-09
Abstract: 530,446. Engine valve gear. WOODARD, W. E. June 9, 1939, No. 16945. [Class 122 (ii)] Valve gear for a reciprocating engine, particularly a locomotive engine, having two cylinders each provided with separate admission and exhaust valves, is provided with separate connections for actuating the admission and exhaust valves respectively of each cylinder, each connection being operated by a member receiving a movement compounded of a movement derived from moving parts, e.g. the crossheads, of the two cylinders, one of these movements being progressively variable, and, for the exhaust valve connection, being at a different rate from that for the corresponding valve connection. By this means the timing of the release and compression relatively to the point of cut-off can be suitably related. The gear box 20, Fig. 8LR and 10, may be mounted as described in Specification 487,686 and supports rock shafts RR, LR operated respectively by connections from the crossheads of the right. hand and left hand cylinders, and carrying yokes 84R, 84L to which are pivoted independent levers 90ER, 90AR, 90AL, 90EL connected respectively by links 111ER, 111AR, 111AL, 111EL to rock shafts operating the cams controlling the movements of the exhaust and admission valves of the right and left hand cylinders. The levers 90ER, 90AR for the right hand cylinders are connected by radius rods 108ER, 108AR to link blocks in a pair of side by side links fixed to a bracket 103R rocked on trunnions 104R by connections from an arm 91L on the yoke 84L actuated by the left hand engine and similarly, the levers 90AL, 90EL are connected to a pair of links actuated from an arm 91R on the yoke 84R of the right hand cylinder. The movement of each lever is thus compounded of a movement due to its carrying yoke and a movement of its link. The exhaust radius rods 108ER, 108LR, one of which 108ER, is shown in Fig. 14, are connected by links 127ER to arms 126ER fixed to a rock shaft 124E, one arm being connected through linkage shown either directly or through a power relay to a reversing lever in the cab of the locomotive, and the other arm being connected by a rod 132, Fig. 155, to the upper end of an arm 134, Figs. 15, 15S, the lower end of which is connected by a pin 135 to a rod 152 connected to the piston rod 150 of a piston 149 working in a pneumatic cylinder 148. The pin 135 forms a fulcrum about which the arm 134 can turn when the shaft 124E is turned, and can be held in either of two positions according to which end of the cyilnder 148, the piston 149 is held. A pin 136 carried by the arm 134 connects the arm to a yoke member 142 pivoted by hollow trunnions 139 in fixed bearings and connected by a rod 144 to an arm 146 fixed to a sleeve 124A freely mounted upon the shaft 124E and having arms 126AL connected by links to the admission radius rods, one of which 108AL is shown in Fig. 15. When the reversing lever is in full gear forward position, all the link blocks are at the upper ends of their links, the piston 149 is at the left hand end of the cylinder 148 and the axes of the pins 135, 136 and trunnions 139 are in line, As the reversing lever is moved over to neutral position, the link blocks move in the slots of their links but by means of the mechanism shown in Fig. 15S, the movement of the rod 144 is more rapid than that of the rod 132 so that the rate of advance of the time of cut-off is greater than that of release and compression. During the passage of the reversing lever through its neutral position, a cam on the end of the shaft 124E actuates valves to move the piston 149 to the opposite end of its cylinder. This throws the fulcrum pin 135 forward causing a reversal of the relative positions of the arm 134 and yoke 142 so that during the further movement of the reversing lever to full gear reverse, the rate of retardation of the time of release and compression is less than that of the time of cut-off. When the reversing lever is in its neutral zone, the cam on the shaft 124E actuates a valve to operate a pneumatic cylinder and piston which operates to open the admission valves at both ends of the cylinder to allow " drifting " of the locomotive. The arm 134 is provided with a hole which. when the parts are in the position shown in Fig. 15 is in line with the trunnions 139 of the yoke. A pin 170 in one of the trunnions is normally held in a retracted position against the action of a spring by a small pneumatic cylinder. If the air supply fails, the spring moves the pin 170 into the hole in the arm 134 so that the movements of the yoke and arm take place in unison and the differential advance of the times of cut-off, release and compression is cut out. Specification 504,056 also is referred to.