Patent GB-1003602-A (GB)
Title: Improvements in or relating to a free piston engine
IPC: F02B71/00
Filed: 1961-12-12
Abstract: 1,003,602. Free piston engines. H. KOSOFF. Dec. 12, 1961 [Dec. 19, 1960], No. 44493/61. Heading F1B. An I.C. engine of the free piston type comprises: a power cylinder; a power piston reciprocable within the cylinder; a rebounce chamber having elastic fluid therein; means operatively associated with the piston for compressing the elastic fluid on the combustion stroke of the piston, the energy of the compressed elastic fluid driving the power piston on the compression stroke; and pneumatic control means responsive to the location of the terminal point of the piston substantially at the end of its compression stroke and start of its combustion stroke, the control means being operatively associated with the piston for varying a pneumatic force acting axially on the piston in response to the displacement of the terminal point from a specified point. The difference between the energy released by expansion of the combustion products and that required to compress the fluid in the combustion chamber is available for useful work. In an engine which may have two or more piston-cylinder units, each unit is provided with a variable force, which may be the rebounce force, to synchronize the oscillation of the pistons and to maintain the nominal compression ratio. A combustion chamber O, Fig. 2, has a inlet 15, an exhaust 14 and a pressure responsive fuel injector 13 connected through a conduit 25 to a compression chamber 16 provided with a suction port 20 and an outlet port 21. An elastic fluid is supplied from a source 31, through a restricted orifice 26 to a rebounce chamber 22 which is vented to a receiver 30 at the end of each compression stroke through a vent 29, which vent is uncovered to an extent depending on the variation of the compression ratio from its nominal value. If the compression ratio is low or high more or less fluid will remain in the chamber 22 to provide a greater or less rebounce force respectively. The nominal compression ratio may be changed by alteration of the source or receiver pressure, orifice or vent area or vent position. The fluid source and receiver may be operative parts of the engine. The engine may be used for pumping an unspecified fluid if the compressed air charge is provided by other sources. In the embodiment of Fig. 3 a compression chamber 40 functions as the rebounce chamber and fluid in a chamber 42 provides the variable force for adjusting the compression ratio. A restricted orifice 43 leads to a receiver 44. Communication with a fluid source 49 occurs when a vent 46 is uncovered. An arbitrary number of piston-cylinder units may be arranged around a common combustion chamber, a common compression chamber, a common rebounce device, or any combination thereof. In another embodiment (not shown), two horizontally opposed piston-cylinder units having a common combustion chamber are each similar to the unit shown in Fig. 2, but each has a vent to atmosphere in its cylinder wall instead of the vent 29 and receiver 30, the vent being further exposed by the trailing end of the piston at the end of its compression stroke during greater than nominal motion, the supply to the rebounce chambers being taken from the engine scavenge box through a conduit interconnecting both of them; the two compression chambers are interconnected by a conduit which branches to the fuel injector. The maintenance of the nominal compression ratio synchronizes the motion of the pistons. In a further embodiment (not shown) three angularly spaced units have a common combustion chamber, each unit being similar to that shown in Fig. 3, but having a vent to atmosphere instead of to a receiver 44 and having the compression rebounce chamber interconnected by a conduit to the corresponding chambers of the other units; the combustion chamber has two exhaust ports controlled by two of the pistons and one inlet port controlled by the third piston. The cylinders may be of any shape, for example a toroid or a sphere, generated by rotating, by 2# or less, an arbitrary curve about an axis.