Image Number 2 for United States Patent #4683931.
A machine for automatically engraving the groove in tire treads provided with a first rotary tire-carrying shaft and with a second tool-holding shaft axially movable in a reciprocating manner parallelly to the first shaft, by way of an appropriate motion transmitting gear cascade. The motion transmitting gear cascade is interchangeable, and actuates a cam. A cam follower is driven by the cam and is fastened to a rack. A gear wheel engages the rack and carries as rocker along one of its diameters. A connecting rod pivots on the second shaft and on a slider, which is engageable along the rocker in an adjustable manner.