Patent GB-728905-A (GB)
Title: Improvements in and relating to the starting of free piston compressors and gas generators
Inventor: KHOLUCY RALPH HAMED
IPC: F02B75/02
Filed: 1951-12-28
Abstract: 728,905. Free piston compressors and gas generators ; starting. MUNTZ & CO., Ltd:, A Dec. 8, 1952 [Dec. 28, 1951], No. 30368/51. Classes 7(1) and 7(5). Starting control equipment for compression ignition internal-combustion operated free piston air compressor or gas generator of the type having a pair of opposed free pistons rigidly connected by two piston rods to two further pistons at least one of which further pistons is a compressor piston serving for scavenging the internal combustion cylinder as well as for delivering air under pressure comprises a rotary member adapted to assume a plurality of predetermined angularly spaced positions about its axis of rotation at least one of the succession of operations involved in starting the machine being initiated upon movement of the rotary member from each predetermined position to the next succeeding predetermined position and means whereby the member is temporarily locked against movement from each one of the positions onwards to the next succeeding position until the corresponding operation or operations of the succession has or have been completed. Fig. 2 shows one half of an opposed piston free piston compressor arranged for starting in accordance with the invention. Referring to the drawings generally, when a lever 74 is moved away from a handwheel 61 and disc 62 a locking pin 45 (Fig. 2) is withdrawn from a groove 46 in a manoeuvring piston rod 36 and at the same time a head member 87 passes through an enlarged end 90 (Fig. 14) of a slot 88 in the disc 62 thus restricting rotation of the handwheel. A pin 80 is also disengaged from a hole 81 in the disc 62 so that the handwheel can be turned. The handwheel is then turned in a clockwise direction as seen in Fig. 14 through a quarter of a turn. In this position of the handwheel a compressed air inlet valve 63 is opened so that air is fed to a manoeuvring cylinder 35 via passage 101 port 105 port 107 and pipe 53. Also valve 65 is opened so as to exhaust air from a cushion space 56 (Fig. 2) via a pipe 55 the valve 65 exhaust passage 102 and exhaust opening 103. This produces manoeuvring of the opposed piston assemblies of the compressor to their outer position. The handwheel is then turned through a further quarter turn. In this position the valve 63 is closed and air is exhausted from the manoeuvring-cylinder 35 via pipe 53 port 110 and passage 108 (Fig. 5) so that the manoeuvring piston 34 can be returned by its spring. In this position of spindle 60 cam 111 presses rocker arm 70 so as to open valve 67 to vent chamber 33 to atmosphere via pipe 125 valve 67 passage 104 and exhaust opening 103. A block 91 at the end of the slot 88 is then in engagement with the head member 87 and prevents further rotation of the handwheel. The next step is the charging of the starting gear. For this purpose the lever 74 is moved towards the handwheel 61. This can only be effected when the manoeuvring piston 34 has returned so that the locking pin 45 can enter the groove 46. When the lever 74 has been moved towards the handwheel 61 a stop pin 86 will be withdrawn from the locking plate 62 so that the handwheel can be moved further in the same direction. It is then moved through a further quarter turn. The valve 63 is then opened again to effect the supply of compressed air-to the starting chamber 33 via the pipe 57 (Fig. 6). The handwheel is then turned through a further quarter turn (starting position). The valve 63 is closed and the air is rapidly exhausted from the space 58 via pipe 57 union 64 port 110 and cavity 108. When pressure in a space 58 (Fig. 2) has fallen sufficiently the compressed air in the chamber 33 urges the piston 39 to the left and opens a valve 37 so that compressed air is permitted to pass rapidly into the cushion space 56 and effect a starting stroke. When the handwheel is moved to the last mentioned position the pin 80 enters the hole 81 thereby preventing further movement of the handwheel 61 until the lever 74 is again moved away from the handwheel. If the lever 74 is moved while the engine is running the handwheel 61 cannot be moved because as soon as pressure builds up in an air receiver 29, Fig. 1, compressed air is fed therefrom to a cylinder 95 to move a pin 93 outwardly into engagement with a hole 112. Alternatively as shown in dotted lines at the top of Fig. 13 the pin is moved into the path of an arm 124 on the lever 74 to prevent movement of the lever while the engine is running. A pawl and ratchet mechanism not shown prevents the handwheel 61 from being rotated backwards when in these positions but it is possible for the handwheel to be turned back from the position corresponding to charging of the starting chamber if in an emergency it should be necessary to vent the space 58. In the absence of the head member 87 the manoeuvring cylinder 35 could be charged with air with the locking pin 45 in its locking position and this could cause the pin to be damaged. If the handwheel is turned prematurely from the charge manoeuvring cylinder position (i.e. the position after having received its first quarter turn) before the parts are in the appropriate positions for starting damage may be caused. In order to avoid this risk a pin 114 is provided to co-operate with a notch 113 of the disc 62. The pin prevents turning of the handwheel until the manoeuvring piston has moved the opposed pistons into the starting position. When this has occurred the piston 35 has moved beyond a port 117 and compressed air is fed to a cylinder 116 to withdraw the pin 114. Also to prevent the handwheel being moved quickly without dwelling at the charge starting chamber position (i.e. the position in which the chamber 33 is charged) a further stop in the form of a pin 119 is provided. A spring 123 of such strength that until the starting cylinder 31 is fully charged the pressure on a piston 120 is insufficient to move it against the spring so that the pin projects into the path of the notch 113. The valve 65 is opened during manoeuvring as stated previously and it remains open until the handwheel has moved slightly beyond the charging position to ensure venting to exhaust of any air which leaks into the cushion during charging. A relief valve (not shown) may be provided for the cylinder 31. Alternatively means may be provided whereby the handwheel is automatically turned to the starting position as soon as a predetermined air pressure obtains in the chamber 33. Fig. 1 shows an opposed free piston compressor before the invention is applied thereto. Air is drawn in through a filter 12 by a compressor piston 6. The left hand side of the piston 6 supplies air through a pipe 15 and intercooler 16 to a high pressure compressor 7. After further compression the air passes from the compressor 7 to a cooler 27 and a reservoir 29. A cooling fan 44 is driven by an exhaust turbine 41. The right hand side of the piston 6 supplies air for scavenging to a space 20.