GB595670A - Improvements in means for starting reciprocating internal combustion engines of freepiston type - Google Patents

Abstract

595.670. Free-piston gas generators. ENGLISH ELECTRIC CO., Ltd., WELSH, R. J., and COX, G. W. May 31, 1943, Nos. 8649 and 15288. [Classes 7 (i) and 7 (v)] In starting an internal-combustion engine of free piston type such as a gas generator for supplying a turbine, automatic means are provided for admitting compressed air to a cylinder of the engine in a number of separate impulses until the piston assembly is reciprocating with its full stroke. whereupon the fuel supply is started. The working cylinder 1, Fig. 1, is associated with compressor cylinders 5 and buffer cylinders 3. Air enters the compressor cylinders from suction inlets 14 and compressed air passes to the engine by way of conduits 15. The piston units are synchronized by links 7, 8 and the fuel pump 10 may be operated by a cam 11 connected by linkage to a point on the link 7. Air may pass to the buffer cylinders from a reservoir 17 through a master starting valve 18, regulator 30, pipes 29, 23, and valves 22. The, buffer cylinders may be vented by valves 27 which may be opened by fluid pressure from a source 51. The same force also moves the barring piston 24 to set the opposed piston assemblies in 'a starting position hear outer dead centre. In one' form of regulator, Fig. 2, a cam 33 oscillated by linkage connecting it to the link 7 operates a lever 34 which is urged upwards by a spring 36. The lever 34 carries tappets coacting with a cut-off valve 38 and, through a spring connection 43, an auxiliary valve 41. The valve 38 may be reset by a fluid-pressure plunger 45. In operation, before starting, the valve 27 is opened and the barring device set by fluid pressure from source 51. Valve 18 is then opened and air passes through valve 41 and pipe 29 to the buffer pistons, moving the piston units inwards. The lever mechanism actuated by link 7 then lowers the lever 34 and allows air pressure to close valve 41. This imparts a small inward movement to the piston units which then rebound whereupon cam 33 opens valve 41 and allows a second pulse of air to flow to the buffer cylinders. This action continues until the amplitude becomes such that the cam 11 is effective to operate the fuel pump whereupon the engine starts. The increased outward piston movements so produced causes the stem 38a of the cut-off valve to be actuated to lift the valve head 38 into the air stream and cause it to snap upwards into a closed position. Subsequently the master valve 18 is closed. The invention may be combined with that described in Specification 595,547, the master valve 18 being controlled by a starting relay. The closing pressure exerted on valve 41 by the air and the lost motion provided by the spring connection 43 ensure that there is a longer opening to the air pressure on the impulse stroke than on the return stroke. The fluid pressure which opens the master starting valve 18 and which may also reset the cut-off valve 38 through tappet 45 may be cut off by a running indicator actuated by the free piston units preferably after delay. In a modification, the spindle 32 carries a ratchet sector coacting with a' pawl on a lever 56 operating a starting air valve 55a. The starting position wherein air flows to pipe 29 is shown in Fig.3. Air pressure tends to close valve 55a and so engages the pawl with the sector 54. The piston movement resulting from the first pulse of air rocks the pawl 59 to a position; in which the valve is closed after which the pawl, now clear of the sector, returns to its Fig. 3 position. During the return stroke the pawl is moved to a position wherein it trails over the sector, the valve remaining closed. As the pistons again move forward the pawl is tilted by the ratchet to open the valve and another pulse of air admitted, the action continuing until the fuel is turned on and starting occurs. The full stroke which now follows causes the part 54b of the sector to lift the pawl on to a catch 62 which retains the pawl and prevents further operation of the starting valve.