A lift assembly includes a base, a platform coupled to the base and moveable between a lowered state and an elevated state, a first pair of scissor arms including a first arm and a second arm pivotably connected to one another, and a second pair of scissor arms including a third arm and a fourth arm pivotably connected to one another. The lift assembly also includes a carriage coupled to the first pair of scissor arms and to the second pair of scissor arms. The carriage includes a shaft extending transverse to the first arm, the second arm, the third arm, and the fourth arm, and a centering wheel rotatably coupled to the shaft. The first arm includes a cam surface engageable with the centering wheel to guide travel of the platform between the lowered state and the elevated state.

A power transmission device includes a first pulley driven by a first drive source; a second pulley driven by a second drive source; a first power transmission belt that is wound around the first pulley and an object to be driven and that transmits power from the first pulley to the object to be driven; a second power transmission belt that is wound around the second pulley and the object to be driven and that transmits power from the second pulley to the object to be driven; a first tension applying section that applies tension to the first power transmission belt; a second tension applying section that applies tension to the second power transmission belt; and a load applying section that applies a load to the first tension applying section and applies a load to the second tension applying section.

The invention relates to a belt-tensioning device comprising a tensioning device for generating a force for tensioning a belt in a belt drive; a measuring device for measuring a belt tension or a measurement variable corresponding to the belt tension; and an adjustment device for adjusting the force generated by the tensioning device based on signals of the measuring device.

Various embodiments provide a timing belt tensioner for a 3D printer and the 3D printer. In those embodiments, the timing belt tensioner includes: a mounting frame, an idler and an elastic member, where the idler is connected to the mounting frame, and a timing belt of the 3D printer is wound around the idler, and is configured to drive a movement mechanism of the 3D printer to move on an XY plane; and the elastic member is configured to connect the mounting frame and a base of the 3D printer such that the mounting frame drives the idler to slide to a balance position relative to the base under an elastic force of the elastic member. When at the balance position, a balance is reached between the elastic force of the elastic member and a tensile force of the timing belt acting on the idler.

A shuttling mechanical tensioner for control of chain drives with alternating tight and slack chain strands. The shuttling mechanical tensioner allows for chain control on an outside face of the chain strand or an inside face of the chain strand.