Abstract: The invention relates to a piston engine comprising one or more air/gas-compressing cylinder-piston units, a crank mechanism connected to the piston in the said cylinder or cylinders for movement of the piston in the cylinder, which crank mechanism is drivingly connected to a rotor in an electric motor. The invention also relates to a coupling and a simple connection for a counterweight.

Abstract: The invention relates to a cooling device for a compressor 100 which is provided with an intermediate heat exchanger 112 and an output heat exchanger 102 for cooling of compressed gas. The cooling device is enclosed by a jacket 200. The jacket has an air intake opening 202, connected to a radial fan 105 which provides an overpressure inside the jacket 200. The heat exchangers 102, 112 are mounted in air outlet openings 204, 206 in the jacket, with the result that the overpressure in the jacket 200 leads to cooling of the heat exchangers 102, 112. The jacket further comprises an additional outlet opening 208 for discharge of air used for cooling other elements of the compressor, such as cylinder walls, covers/tops and crankcases. The relationship between the different cooling processes can be influenced by the design of the openings 204, 206, 208 in the jacket 200.