Patent GB-353175-A (GB)
Title: Improvements in or relating to regulating valve apparatus for locomotive or other steam engines
IPC: B61C17/12
Filed: 1930-06-06
Abstract: 353,175. Regulating-valves. SUPERHEATER CO., Ltd., Bush House, Aldwych, London.-(Kimberley, R. E.; Los Talleres, Junin, Argentine.) June 6, 1930, No. 17672. [Class 135.] . Lift valves ; actuating mechanism.-In regulating valves for steam locomotives and engines, such as are described in Specifications 248,239 and 296,513, [both in Class 135, Valves &c.], wherein the supply of steam is controlled by one or more poppet valves 6, 7 which may open in predetermined order, and are each provided with a balancing piston 8, 9, there being a pilot valve 10 to supply steam to a balancing chamber 3, valve chatter due to cyclicly varying steam demand is eliminated by exhausting steam from the balancing chamber when a predetermined lift of the main valves has been effected. The balancing pressure is thereby reduced, and the higher steam pressure in the supply 1 maintains the valve steady against its operating cam. The main valves which may be four in number are operated from a rock shaft by cam fingers which fit with lost motion between a hardened steel washer 36 and a spaced nut 37 on the valve stem. The pilot valve may be operated from the same rock shaft or from a separate trigger on the regulating lever. The balancing chamber is exhausted by means of a valve 17 having a lost motion connection with a part 16 of the pilot valve stem having three flats 25 to permit passage of steam. After a predetermined lift of the main valves a piston 13 on the pilot valve covers ports 12 to isolate the balancing chamber except for a small leak past the piston 13, whereafter the valve 17 lifts and permits steam to reach the underside 32 of a differential piston 26, the upperside of which communicates with the delivery chamber 2. The piston 26 controls a relief valve 28, the arrangement being such that when the balance pressure exceeds a value given by a predetermined ratio between the balancing and delivery pressures the piston opens the valve 28 and puts the balancing chamber into communication with the atmosphere. Instead of this arrangement the balancing chamber may exhaust at a fixed pressure determined by a spring-loaded relief valve on the exhaust pipe 33. The valve 16, 17 may be replaced by one comprising a piston fixed on the pilot valve stem and having a circumferential groove provided with radial ducts leading through an axial duct to the pipe 33. The piston slides in a screw plug in the lower wall of the balancing chamber, the plug having radial ducts communicating with the piston groove so that initially the balancing chamber is in communication with the exhaust pipe 33, such communication being cut off on preliminary operation of the pilot valve and re-established after a predetermined lift of the main valve when the piston groove emerges from the plug. The main valves may be operated in a predetermined order either by providing cams of different profile or by varying the thickness of the washers 36. The [main valve seats 41, which have upper cylindrical parts with ports 43, may be extended downwards to form liners for the balancing pistons which may each be of a diameter less than, equal to, or greater than, that of the valve seat. The Provisional Specification states also that when the diameter of the balancing piston is greater than that of the main valve, the piston body may be of such diameter that it will pass through the main valve seat and be then equipped with spring packing rings which expand into the bore in which the piston works and increase its effective area.