Image Number 3 for United States Patent #4145086.
Disclosed is a method and machine for digging a ditch for use in, for example, duct disposition therein. In the floors and walls of a concrete structure, for example, three preparatory ditches or channels are dug by means of rotary blades. By inserting a breaking rod into a central one of the channels and causing it to vibrate substantially perpendicular to the channel to strike partition walls between the channels, the partition walls are readily broken or fractured, at which time the outermost channels serve as escapement spaces for permitting reception therein of the partition walls about to be bent or broken. Thereafter, the resultant partition wall pieces are removed, whereby a desired form of ditch is obtained. The partition wall fracturing steps may be carried out simultaneously with the channel digging or cutting step, or may alternatively be carried out independently after completion of the latter step.