Essential safety device on wood processing machines for the lengthwise processing of solid wood, which is intended to prevent the uncontrolled reversing of workpieces in the direction of the operator. Use e.g. with thickness planing machines, moulders and multiblade saws.

Technical principle explained on the basis of the multiblade saw

The workpiece to be processed is drawn into the multiblade saw by means of a feeding chain. The saw blades generally function in the up-cut, i.e. the cutting forces act against the feed direction. If a splitting off of wood pieces occurs, or parts of the workpiece are not clamped firmly between the feeding chain and the upper pressure element then an uncontrolled reversing of the workpiece parts can result. This brings with it a high risk of accidents and injuries. Wood processing machines of this type must therefore be equipped with anti-kickback safety devices, which reliably prevent kickback automatically and independently of other machine functions.

Customarily, wedge-shaped metal parts are arranged on a round axis across the entire working width. Due to their shape (use of gravity) these are always positioned tight to the workpiece and their wedge- shaped tips key directly into the wood with a reverse motion, thereby safely preventing kickback/reverse movements.