394,147. Engine valve gear. TOLKIEN, F., 18, Lister Kirchweg, Hanover, Germany. July 16, 1932, No. 20236. [Class 122 (ii).] The main valve control is effected bv differential pistons at both ends ; smaller differential pistons are loosely connected to the main valve with lost motion and function as auxiliary valves controlling the supply to the larger pistons formed on the ends of the main valve. The main valve under fluid-pressure at one end moves free of the auxiliary valve at that end until past the central reversing position to ensure the reversal of fluid in the main cylinder. During this motion, the opposite end of the main valve is put to exhaust or reduced pressure. In the construction shown in Fig. 1, the steam passages a<1>, a<2> have small branches a<3>, a4 leading to the cylinder ends. The main valve d has three heads ; a central distributing-head d<1> and actuating heads e<1>, e<2>. The valve-chest has ports p<1> p<2> connected to the cylinder, a port p to the supply E and ports p<3>, p<4> to the exhaust A. Auxiliary casings c<1>, c<2> have hollow auxiliary valves e, e<3>. Rods e<4>, e<5> attached to to the main valve have heads e<6>, e' movable in the valves e, e<3>. The auxiliary valve chambers have working spaces f, f<3> respectively, and the main valve chamber has working spaces f<1>, f<2>. 'Branches n, n<1> with branches n2, n<3> lead from the cylinder passages to the spaces f, f<3> respectively. Passages h<1>, h<2> permanently connect the spaces f<1>, f<2> with grooves g<1>, g<2> in the auxiliary valves respectively which grooves may also communicate with main-piston controlled passages m, m<1>. In the position shown in Fig. 1 with piston moving downward, steam in space f holds the valve downward and chambers f<1>, f<2> communicate with the exhaust. When the piston b passes the passage m<1>, steam passes to the chamber f<2> and acts upwardly upon the valve d and the head e<7>, and downwardly on the auxiliary valve e<3>. The main valve d rises unimpeded until, when past its middle position, the heads e<6>, e<7> engage the valve e, e<3>. When the supply of steam to the lower end of the cylinder a begins, the upper end begins to exhaust and also the steam in the auxiliary valve space f. The chamber f<1> remains open to exhaust and steam is supplied to the space f<3> so that both ends of the valve e<3> are subject to steam pressure. The valve d. continues its upward movement taking the valve e<3> with it. When the auxiliary passage o<1> is closed, the passage m is opened so that the space f<1> continues open to exhaust through the main cylinder. The auxiliary valve e<3> closes the passage m<1> thereby cutting off steam to the space f<2> and afterwards puts it into communication with the exhaust by opening port o<2> so that the expanded steam in space f<2> escapes. This slows down the valve, which moves in virtue of its kinetic energy. When chamber f<2> is put to exhaust, the steam pressure in space f<3> moves the valve e<3> up to engage the main valve and complete its motion. The valve is held up until the reverse action begins. The application of the gear to a compound, tandem cylinder engine is shown in Fig. 3. The main valve d has three distributing heads d2, d<3>, d<4> and is hollow, the spaces between the upper and lower heads being connected. The exhaust pipe A and port p<7> are towards the lower end of the valve casing c. Ports p<5>, p<6> are connected to the upper and lower ends of the low pressure cylinder a<n>. The main valvechest ends f<1>, f<2> are vented by pipes o<3>, o<4> connected to the passages a<5>, a<6> and are filled with intermediate steam with the piston rising from the position shown. The upper auxiliary slide valve e is also acted upon by intermediate steam from the passage a<1> in opposition to the pressure of the main steam acting in the valve e<3> holding it up. On the upward-moving, highpressure piston passing the passage m, steam is passed to space f<1>. The main valve is moved down in opposition to the steam acting in the space f<3> until the head e<6> strikes the valve e. Steam is supplied to the upper end of the highpressure cylinder and to space f, and exhausts from the bottom of the low-pressure cylinder through passage a<5>, the hollow main valve and the outlet A. The chamber f<2> is put to exhaust through the passage h<2>, the groove in the valve e<3>, and the passages o<4>, a<5>. The exhaust from beneath the high-pressure cylinder passes to the top of the low-pressure cylinder. Intermediate steam is supplied to space f<3> from the pipe a<2>. The intermediate pressure now in the space f<1> acts upon the lower end of the valve e, the upper end of which is acted upon by highpressure steam. Valve e moves down, completes the movement of the valve d and holds it down. Further modifications are described wherein the auxiliary slide valves are constructed as differential pistons with guide pistons of smaller diameter which slide on rods on the main slide valve.