A radial piston machine includes a piston having a base which is provided with a roller. The roller is held secure by a bearing shell that is inserted in the piston base.

The invention relates to a radial piston hydraulic motor. The radial piston hydraulic motor comprises a cam ring provided, with a wave-shaped inner surface and radial cylinders provided in the inner part inside the cam ring and pistons that move therein as well as rollers coupled to the pistons so as to follow the inner surface of the cam ring. By the effect of the working pressure of hydraulic oil conveyed to the cylinders, the rollers that are pressed against the inner surface of the cam ring provide a rotating movement of the cam ring and the inner part relative to each other. The hydraulic motor is provided with disengaging members disengaging the rollers coupled to the pistons from contact to the inner surface of the cam ring when the working pressure stops acting in the cylinders for bringing the hydraulic motor into freewheeling. The hydraulic motor is provided with a control coupling which, when the prevailing pressure of hydraulic oil in the working pressure line that leads to the cylinders drops below a specific level, automatically disengages the cylinders from the working pressure line and couples the hydraulic motor into freewheeling.

A gas supply pump for a ship dual fuel engine is described. The gas supply pump includes a rotatable camshaft, a plurality of cam noses arranged at regular intervals along a lengthwise direction of the camshaft, a cam roller in close contact with each cam nose, a drive shaft and a piston adjacent to each other on one side of the cam roller, a liquefied gas compression device to compress and discharge liquefied gas by a linear reciprocating motion of the piston, a coupling case at a coupled part of the drive shaft and the piston, a rack member connected to the drive shaft, or connected and fixed to both the drive shaft and the piston in an internal space of the coupling case, and a pinion engaged with a teeth-shaped rack on an outer surface of the rack member.