Abstract: The device comprises at least one flap member (3) having a rear flap portion that runs in a plate plane, and a forward portion, as seen in the direction of motion (F). The forward portion (8) is connected to the object (2) in such manner that the flap portion (17) can be moved in the fluid transverse to the plate plane and between two positions which are on their respective sides of a neutral place (P). Furthermore, the device comprises an actuating means (8, 9) which allows a freely oscillating motion of the flap member (3; 61, 62), and a drive unit (6) for actuating the flap member (3; 61, 62) when the valve of an oscillation amplitude of the flap member (3; 61, 62) is less than a predetermined threshold value.

Abstract: The device comprises at least one flap member (3) having a rear flap portion that runs in a plate plane, and a forward portion, as seen in the direction of motion (F). The forward portion (8) is connected to the object (2) in such manner that the flap portion (17) can be moved in the fluid transverse to the plate plane and between two positions which are on their respective sides of a neutral place (P). Furthermore, the device comprises an actuating means (8, 9) which allows a freely oscillating motion of the flap member (3; 61, 62), and a drive unit (6) for actuating the flap member (3; 61, 62) when the valve of an oscillation amplitude of the flap member (3; 61, 62) is less than a predetermined threshold value.

Abstract: An energy converter comprising a free piston engine with a cylinder (2), a piston (3), a body connected to the piston such as an armature (11) of a linear electric generator (10). The energy converter comprises a spring device (15), via which the armature (11) is springingly connected to the housing (1), and which is arranged to permit an oscillation of the armature (11) in the piston's (3) direction of movement with a natural frequency fc relative to the stator (12).

Abstract: A method for propulsion of water-going vessels (1) comprising a plate (9), which is located in the water (2) and extends across a desired direction of motion for the vessel (1), where the plate (9) is moved from a first position (P1) to a second position (P2) and back. Under the influence of a motive force the extent of which varies sinusoidally, the plate (9) is brought into translatory and rectilinear oscillation about a neutral position (N2) between the first and the second position (P1 and P2 respectively), the neutral position (N2) being determined by a static equilibrium between spring forces influencing the plate (9). The plate (9) is controlled in such a manner that its plate plane extends perpendicularly to the vessel's (1) direction of motion, and a greater resistance is exerted by the plate (9) against the water when it is moved opposite to the vessel's desired direction of motion than when it is moved in this direction. A device for performing the method.