Title: Disc cutting unit for use on rock boring machines

Description: This invention relates broadly to rock boring machines of the type in which a plurality of disc cutting units are mounted on the front face of a rotatable headplate. Such machines are primarily used for cutting through rock formations.

Conventionally each disc cutting unit comprises a base which is adapted to be secured to the headplate, a bearing shaft mounted in saddles or the like formed in the base and a cutting disc journalled for rotation on the shaft.

The cutting edge of the disc is generally a hardened steel member and when tungsten carbide is used this is in the form of separate segments not forming a continuous cutting edge.

It is accepted that, for optimum cutting efficiency, the cutting segments should be closely spaced to one another as possible. In other words, the outer edges of the cutting segments should, as closely as possible, approach a continuous surface. In the conventional disc cutting unit this is difficult to achieve as the cutting segments are generally located in individual recesses formed in the rotatable annular body.

It is an object of the present invention to provide a new and improved disc cutting unit in which the outer edges of the individual cutting segments provide a substantially continuous cutting surface.

According to the invention a disc cutting unit of the type described comprises a base adapted to be secured to the front face of a rotatable headplate of a rock boring machine, a bearing shaft mounted on the base, an annular body journalled for rotation on the bearing shaft, a continuous recess extending around the periphery of the body, a plurality of cutting segments located in the recess to extend around the periphery of the body, and removable clamping means adapted to secure the segments in the recess.

To illustrate the invention an embodiment thereof will now be described with reference to the accompanying drawings, in which

FIG. 1 is an axial view of a rotatable headplate of a rock boring machine comprising the environment of the present invention and

FIG. 2 is an enlarged elevational view partly in cross section of the disc cutting unit of the invention.

In the drawings the disc cutting unit 10 comprises a bearing shaft 11, which is adapted to be secured to a base or saddle 8 on the front face of a headplate 9 of a rock boring machine, an annular body 12 journalled for rotation on the bearing shaft, and a plurality of cutting segments 13 arranged around the periphery of the body 12. The cutting segments are made of some suitable hard metal such as tungsten carbide.

The cutting segments 13 are located on the bed of a continuous recess 14 which extends around the periphery of the annular body. The recess 14 is actually divided into two distinct parts: a first part having a substantially horizontal bed 15 on which the cutting segments rest, and a second portion having a lower bed 16.

The cutting segments are held in the recess by means of a plurality of clamping blocks 17 each of which rests on the bed 16 and bears against one side of the cutting segments. The clamping blocks are held by means of bolts 18 which pass through the blocks and screw into the annular body.

The segments 13 are preferably tapered in cross-section, and the side of the recess (against which the segments bear) and the clamping blocks 17 are complementally undercut so that the segments are wedged between the side of the recess and the blocks.

In the manner described above the cutting segments can be spaced very closely to one another thus enabling a substantially continuous periphery of the segments to be obtained. Furthermore the cutting segments can by this arrangement be put under considerable compressive stress in two directions which will substantially reduce any tendency toward breakage under loads applied to the cutting edge.