Patent GB-707424-A (GB)
Title: Improvements in or relating to valve gear mechanisms for reciprocating engines
IPC: F01L25/04
Filed: 1951-10-03
Abstract: 707,424. Engine vatve-gear. SYKES, H. W. Jan. 5, 1953 [Oct. 3, 1951], No. 23068/51. Class 122(2)  The valve gear of a steam or other fiuid-pressure reciprocating engine comprises a valve-actuating member actuated by a reciprocating part of the engine to rotate, during normal running, in one direction only irrespective of the direction of movement of the reciprocating part. An arm 103 attached to the crosshead 4 of a reciprocating steam engine carries a slider ring 104 having attached thereto four slippers which engage in intersecting spiral grooves 101, 102 of opposite pitch formed in a shaft 100. Each slipper is mounted on the inner end of a pin 106 journaled in the slider 104 and carrying on its outer end a tumbler 107 which, when the slider is at either end of its stroke, engages the surface of a spring- loaded ramp 108 whereby the slipper is turned so as to leave the groove in which it was engaged and enter a groove of opposite pitch, the shaft 100 thus being rotated in one direction only. If the engine is reversed when the slider is between the areas of its stroke the shaft 100 will rotate in the opposite direction until the slider reaches the end of its stroke but will then resume its normal direction when the slider returns, the slippers remaining in the same grooves. The shaft 100 drives a shaft 65 of a rotary control valve comprising two coaxial cells 41, 42 both in permanent communication with a steam chest 21 through passages 43, 44 respectively. The cells are identical and each has in its end walls 45, 46 arcuate upper and lower grooves 81, 82, 88, 89 co-operating with ports 83, 84. 90, 91 in a pair of port plates 49, 50 journaled on shafts 65, 66 respectively and angularly adjustable thereon by control members 61, 62. Between the port plates 49, 50 and co-operating therewith are valve discs 53, 54 secured to the shafts 65, 66 and having mutually interengaging projections so that they are driven together. The end wall 45 has an annular groove 80 connected to exhaust by a passage 80a and cooperating with ports 85, 86 in the port plate 49. The valve disc 53 is formed with a single exhaust cavity 87 to periodically connect ports 83, 85 and 84, 86 and exhaust the arcuate grooves 81. 82, and the valve disc 54 has a single port 92 that registers in turn with ports 90, 91 to admit steam to the arcuate grooves 88. 89. The upper arcuate grooves 81, 88 and the lower arcuate grooves 82, 89 are respectively connected in pairs by passages 93, 94 and each pair of grooves and the two similar pairs from the celt 42 are connected individually to a. reversing valve 95 provided with through ports and passages such that the engine valve events may be transposed to reverse the engine by turning the valve through 90 degrees. The engine cylinder is provided at each end with one inlet 6 and one exhaust 7 double-beat poppet valve operated by servomotors comprising pistons 17, 18 attached to the valve rods and actuated by steam distributed to the cylinders 19, 20 by the rotary control valve. Steam is supplied to the tail rod casing 23 of the inlet valve 6 through a port 28 covered by the tail rod 22 soon after the valve opens, the steam being thereby trapped to damp the valve movement and subsequently close the valve when the servo-cylinder 19 is operated to exhaust. The exhaust valve 7 may be similarly arranged or, alternatively, it may be spring- loaded. In a modification the valve rod of a piston type slide valve and two pairs of servomotors actuated by steam controlled by the rotary control valve are connected to a rocker arm, one pair of servomotors being connected at each end of the rocker arm and the valve rod being connected at a point displaced from the mid-point of the rocker arm so that by selective operation of the servomotors the valve rod can be moved into any of four positions. In a further modification an expansion valve is superimposed on a flat slide valve and both valves are separately operated by two oppositely acting servomotors controlled by the rotary control valve.