Patent GB-579733-A (GB)
Title: Improvements in or relating to direct-acting internal-combustion-operated motive-gas generators of the free-piston type
IPC: F02B71/00
Filed: 1942-06-25
Abstract: 579,733. Combustion-product plant; regulating. MUNTZ & CO., Ltd., A., and BEALE, E. S. L. June 25, 1942, No. 8763. [Classes 7 (i) and 7 (vi)] [Also in Group XXIX] A motive-gas generator is of the type in which free pistons 10 operating in a two-stroke internal-combustion cylinder 11 are integral with or directly connected to pistons 14 compressing air in cylinders 15 arranged to charge the cylinder 11, the movement of the pistons being cushioned by air compressed in the outer ends of the cylinders 15. The quantity of air in the cushioning spaces is controlled conjointly from a dead-point follower 25 responsive to changes in the inner dead-point of the free-piston assembly and from a device 24 responsive to changes in the delivery pressure of the gas generator, in such a manner as to reduce changes in the overall compression ratio. In one form, Fig. 1, which is designed to maintain a constant compression ratio, the compressor pistons 14 deliver compressed air through valves 17 to a receiver 18 communicating with the scavenge ports 12 in the cylinder 11, the two piston assemblies being connected by linkage so as to operate in synchronism. The cushioning spaces in the cylinders 15 are connected by a balance pipe 19 connected to the receiver 18 through non- return valves 21A, 21B opening in opposite directions and normally shut off by a transfer valve 22 controlled in dependence on the dead-point followers 25 and on the pressure in the delivery pipe 34 of the gas generator. The control means comprises a floating lever 23 pivoted upon a slide block 27 moving in a fixed vertical guide 28. At one end the lever 23 has a slot in which is adjustably fixed a roller 36 engaging a crosshead 31 on the dead-point follower 25, which is connected by a member 26 to one of the pistons 14. The other end of the lever 23 is connected by a link 35 to the member 30 of a pressure-responsive bellows 24 in a chamber 32 connected to the delivery pipe 34. The pivot of the lever 23 is connected by links 29, 43 and a lever 38 to the restorer lever 42 of a hydraulic servo-motor 39. This comprises a double-acting piston 44 on the rod 45 of the transfer-valve 22, and the slide valve 40 of the servo-motor is linked to an intermediate point 41 on the lever 42. The dead-point follower 25 may be that described in Specification 579,734, and the effect of the control is that variations in the inner dead-point of the pistons 10 or in the discharge pressure in the pipe 34 cause movement of the valve 22 to allow transfer of air from the cushion spaces 15, past the valve 21B, to the receiver 18, or vice versa past the valve 21A. A modified form of generator, Fig. 3, is designed to vary the compression ratio in such a manner as to reduce the ratio for low delivery pressure, in order to give better combustion and to enable the generator to give a low minimum output; stabilizing means are also provided to reduce the sensitivity of the control means under conditions tending to cause instability. The intermediate point of the floating lever 23A is connected by a link 29A to the lever 38A, which turns on a fixed pivot 50 and is pivoted at 57 to a stabilizer level 52. A tail on the lever 38A has a slot 53 engaged by a pin 54 fixed to the lever 52 and linked tc a leaf spring 55 which normally pulls the pir to the upper end of the slot. A stabilizer collar 56 on a slipper 57 on a fixed guide 58 bears upor the lever 52 and is linked to a pin 61 moving in an angular slot 62 in a bell-crank 59 pivotec at 60 and actuated from the crosshead 31A of the dead-point follower 25A. While the pin is in the arcuate part of the slot 62, the roller 56 is above the fulcrum 50 of the lever 38A and is ineffective; but in the vertical part of the slo is adjusts the roller 56 along the lever 52 anc thus reduces the movement of the left-hand enc of the lever. Adjustment of the sensitivity o the control device is effected by moving the pin of the link 29A in a slot 63 in the lever 38A Adjustment of the overall compression ratio is effected by means of a control rod 64 sliding in guides 67 and arranged to displace the roller 36A by means of a link 68 connected to the bearing pin 66, which is mounted on a block 65 sliding in a slot 37A in the lever 23A. The connecting member 30A of the pressure-responsive bellows 24A includes a double-acting preloaded spring link for accommodating excessive displacements. The moving element 71 comprises a tube 70, the widened upper end of which forms annular abutments 72. 73 for a cross pin 74 engaging vertical slots 76 in the tubular connecting member 30A. The pin 74 is normally held against the abutment 73 by a spring 75. A bolt 77 is held by a spring 78 against the member 71 and carries a cross pin 79 engaging vertical slots 80 in the member 30A. On compression of the link, the bolt 77 and cross pins do not move relative to the tube 70 and the spring 78 is further compressed; on extension, the member 30A, cross pins and bolt 77 move as a unit relatively to the tube and the spring 75 is compressed. In a further modification, the floating lever 23 is adjustable bodily with respect to its connection with the link 29. Each end of the lever is provided with a roller such as 36, Fig. 1, engaging a crosshead such as 31 on the dead-point follower 25 and a similar crosshead on the pressureresponsive member 30, and a slot in the lever engages a slide block such as 27 movable in the vertical guide 28. The adjustment is effected by means of a control link connected to a bracket on the lever 23 and to a bell-crank adapted to actuate a control rack for a fuel pump in order to increase the fuel delivery concurrently with the compression ratio. Specification 556,454 also is referred to.