Patent GB-507233-A (GB)
Title: Improvements in valve gears for reversible reciprocating fluid-pressure engines, especially for locomotives
IPC: F01L31/16
Filed: 1937-09-07
Abstract: 507,233. Engine valve-gear. LENTZ, H. J. Sept. 7, 1937, No. 21806. [Classes 122 (ii) and 122 (iii)] A poppet valve-gear for reversible, fluidpressure engines, especially locomotive steamengines with rotating-cam valve-gear for admission and exhaust, has one or more adjustable cam-shafts, each of which has in its circumference partly helically and, if desired, partly axially extending control grooves in which coupling elements engage and are guided, which elements by suitable transmission means adjust the cams when the shaft is shifted axially. The cam-shaft 15 is arranged transversely of the cylinder 1 and operates separate admission and exhaust valves on each side thereof. The steam enters at 5 and passes the valve 3 to the end of the cylinder shown, and through the valve-chest, passage 8 to the admission valve at the other end of the cylinder. Similarly, the exhaust from the right-hand end of the cylinder passes through a passage in the chest to the outlet 7. Alternatively, the chest may have admission and exhaust openings at both ends. The double-beat valves 3 are mounted in bushes 10, and have packing grooves. The admission and exhaust cams are housed in two chests 11, 12 respectively. Two cams E<1>, E<2> are mounted on the shaft 15 and are angularly moved by balls in the cams engaging grooves in the shaft 15 which is longitudinally movable. A cradle 20 which is pivoted on a lever 22 mounted at 23 in the chest, engages both cams. The lever 22 operates the admission valve 3. The cradle comprises two curved arms W<1>, W<2> which slide on the cams E<1>, E<2> respectively. The exhaust cam A is coupled to the shaft 15 by a ball 18a which engages the groove 19, and operates the valves through lever 28 carrying domed contact pieces 27. The valves are closed by steam or air pressure. The valve spindles pass through the covers 31 and are acted upon by pistons 33 in cylinders 32. A bolt 13a is inserted into a bore 36 of the spindle and is acted upon by the pressure fluid in cylinder 38 to maintain the arms W<1>, W<2> in contact with the cams. In the position of the cam shown in Fig. 5, with the arm W<1> on the base circle of the cam and the arm W<2> on the raised portion of cam E<2>, the lever 22 just touches the admission valve spindle. When cam E<1> raises arm W<1>, admission takes place. When cam E<2> lowers arm W<2>, cut-off takes place. Adjusting cam E<2> alters the charge. The control groove 34, Fig. 2, affects cam E<2>. During the control, the cam E<1> is controlled by the axial groove c: During reverse running, the part g of the groove 34 controls the cam E<2>, the part d of groove 19, which is spirally arranged to control admission, controls cam E<1>, and the part c of groove 19 actuates the exhaust valve. A modification is described wherein the two grooves 19, g are replaced by a single groove. A modification is also described wherein the valves are in the cylinder, and the cam operates through bell-crank levers which are substituted for the levers 28, 22. The exhaust lead and compression may be varied for different charges. The grooves a, c controlling the forward and reverse exhaust are made to deviate from straight lines. The compression begins sooner and the exhaust lead later with larger charges. The exhaust, valve-operating lever may carry exchangeable shoes 24 with domed running-on faces 27, Fig. 10. The levers and cradles may be mounted on eccentric pins to effect further adjustments. The exhaust control cam may comprise two parts relatively adjustable. The axial shifting of the cam-shaft 15, 15a may be effected by elements having inclined teeth and relatively movable at right-angles, or a fluidpressure servomotor may be used. In a further modification, .the control chest has two parallel cam-shafts 45a, 45b connected by a strap to a rod for simultaneous adjustment by a transverse rod with oblique teeth which engage similar teeth in the rod. The shafts are driven by worm and spur gearing 51, 52, 56. The camshaft 45b engages by means of a serrated head, grooves in the hollow' hub 53 of the wheel 52. The spur wheels are connected to the shafts 45a, 45b by keys. Bushes K', K<2> are loosely mounted on shafts 45a, 45b, and carry admission lead and cut-off cam respectively. The cam E<1> is adjustably mounted. Bushes L<1>, L<2> as the shafts carry cams A<1>, A<2> controlling the exhaust lead and compression respectively. Levers with pivoted cradles, engage the cams, or the cradles may be mounted on bell-cranks or on spindles operating the valves. Reference has been directed by the Comptroller to Specificaton 491,729.