Abstract: The invention relates to a multi-piston hydraulic pump for a free-piston engine, comprising two engine pistons (2) mounted on a common piston rod (1) which is also fitted with pin-shaped pistons (5a, 5b) of the hydraulic pump at a radial distance from the piston rod (1). Mounting blocks (6a,6b) for the hydralic punp pistos (5a, 5b) extend from the engine piston rod (1) crosswise relative to each other at an axial distance from each other. The hydraulic pistons (5a and 5b) fastened to different mounting blocks (6 and 6b and 6b) are located for the most part side by side over the same section of the axial length of the engine piston rod and the free ends thereof point in opposite directions.

Abstract: The invention relates to a method for absorbing the vibration of a five-piston engine and to a vibration-absorbed five-piston engine. At least two separate piston units are synchronized to operate in a counter action such that a certain position of one piston unit actuates forcibly and simultaneously the operation of fuel pumps and injection nozzles intended for the two piston units. Operation of the fuel pumps can be effected mechanically by means of the actions of the piston unit.

Abstract: A method of starting a free piston combustion engine is described in which the free piston unit consisting of the combustion pistons and the piston rod connecting them is set in motion by alternately pressurizing the hydraulic cylinder spaces of a double-acting piston and cylinder arrangement whose piston or piston is or are connected to the piston rod. For this purpose pressure from a hydraulic accumulator used for starting the engine is supplied as a control pressure to the check valve members of the one way outlet check valves of the hydraulic cylinder spaces to keep those check valves closed during starting of the engine. This control pressure supplements the spring pressure supplied by springs in the check valves biasing the check valve members towards their closed positions. Simultaneously a directional valve is used to channel hydraulic fluid from the hydraulic accumulator directly to the cylinder spaces in turn, thereby bypassing the one way inlet check valves to the cylinder spaces.