Abstract: A tubular drive assembly including two or more polygonal tubes one inside the other. While being rotational loaded, to at least one direction, the tubular drive assembly delivers torque to that direction, maintains straightness, prevents lateral movements between the two said tubes, and allows longitudinal force as much as the friction between the tubes. The tubes may be provided with mutually cooperating coupling members for providing mutual fixation in longitudinal direction. Mutual rotation of two successive tubes in one direction will bring the coupling members into engagement to prevent relative longitudinal displacement. Mutual rotation in the opposite direction will disengage the coupling members to allow relative longitudinal displacement.

Abstract: A tubular drive assembly including two or more polygonal tubes one inside the other. While being rotational loaded, to at least one direction, the tubular drive assembly delivers torque to that direction, maintains straightness, prevents lateral movements between the two said tubes, and allows longitudinal force as much as the friction between the tubes. The tubes may be provided with mutually cooperating coupling members for providing mutual fixation in longitudinal direction. Mutual rotation of two successive tubes in one direction will bring the coupling members into engagement to prevent relative longitudinal displacement. Mutual rotation in the opposite direction will disengage the coupling members to allow relative longitudinal displacement.

Abstract: A mallet is described that has at least one cleft, in such a structure that the stress wave created during impact has longer travel way than the length of the mallet as measured along the impact line. This mallet induces longer-lasting and weaker stress wave(s) in the anvil as compared to a solid mallet having the same outer dimensions and more or less the same weight. The Cleft-Mallet increases the effectiveness of the strike, while decreasing the stresses in the anvil.

Abstract: The Force-Barrier is a very fast force applier and remover on or from a reciprocating body. The Force-Barrier is a completely passive device. It needs no control, and switches the force always at the same location regardless the orientation and gravity. In case the reciprocating body is driven by pressurized liquid or compressed gas, the Force-barrier is a substitute to a directional valve, or on-off valve, but faster, consuming less energy, and not being in need of control. The Force-Barrier enables the use of at least one spring and/or at least one electro motor in rebound-effectors and other reciprocating devices. The Force-Barrier may be implemented as a disk placed in between a cylinder and a piston, wherein the cylinder has two internal diameters, and the piston has two external diameters, and wherein there is a step between the two diameters of the piston and the two diameters of the cylinder.