Activated Rock Cutting Assembly

This invention relates to an activated or radially vibratable rock cutting assembly or tool for use with a machine which is capable of rotating it for the purpose of rock cutting.

In this specification the term rock cutting is to be taken to include any rock breaking or comminution process which will result in the cutting of rock.

An activated rock cutting assembly according to the invention includes a rock cutting roller which is eccentrically mounted on a drive arrangement and means for varying the mass of the assembly about the drive axis of the drive arrangement so that the balance of the assembly may be variable about the drive axis.

In a preferred form of the invention the assembly includes two of the rock cutting rollers which are located on a common drive axis with the axis of each roller being eccentrically displaced by a common distance and in opposite direction from the drive axis.

Further according to the invention the or each rock cutting roller is composed of a hub portion to which the drive arrangement is attached and an annulus which is rotatable about the hub and carries rock cutting formations.

Conveniently the rock cutting formations are buttons, bits, teeth, picks and the like.

Further according to the invention the hub portions of the rollers are integral with each other and the hub portions of the outer rollers of the assembly each carry a support shaft the axis of which lies on the drive axis of the assembly.

In one form of the invention the mass varying means is at least one cavity in the hub portion of the assembly and the assembly includes means for introducing a fluid into and extracting it from the or each cavity to cause the required degree of imbalance of the assembly.

In another form of the invention the mass varying means is a weight which is movable relatively to the common axis to vary the degree of imbalance of the assembly.

The invention is now described by way of example only with reference to the drawings in which:

FIGS. 1 and 2 are respectively a cross-sectioned end elevation and a side elevation of one embodiment of the rock cutting assembly of the invention;

FIGS. 3 and 4 are similar views to that of FIGS. 1 and 2 of a second embodiment of the assembly which in turn illustrates two versions of cutters for use with the assembly; and

FIGS. 5 and 6 illustrate yet a further embodiment of a rock cutting assembly according to the invention.

The roller assembly of the invention is shown in FIGS. 1 and 2 of the drawings to include a shaft 10 and two rollers 12 and 14, the axes of which are eccentrically displaced by equal distances from and on opposite sides of the shaft axis.

The rollers are shown to consist of hub portions 16 and 18 which are integral with the shaft 10 and peripheral annuli 20 and 22 which are freely journalled for rotation on the hubs on suitable bearings 24.

A chamber 26 is located in the hub portion of the rollers on one side of the shaft axis. A port 28 leads from the shaft to the chamber and another port 30 from the chamber to the opposite end of the shaft. Small water passages 32 lead from the chamber 26 on to the outer surfaces of the shaft.

A counter-weight 34 of suitable mass is located in the hub portion of the assembly opposite the chamber 26 to balance the chamber when it is water filled.

In this embodiment of the invention the outer surfaces of the annuli 20 and 22 carry rock cutting studs 36 (shown only in FIGS. 4 and 6) which are suitable for cutting the type of rock on which the cutter is to be used. The rock cutting formations on the annuli are, however, not limited to the buttons 36 but could consist of teeth, rock picks, cutting bits, roller discs and the like. The formations could be arranged in the annuli so that they are abraided away progressively and could even consist of a layer or ring of hard or highly abrasive material.

When the shaft 10 is driven with the annuli pressed to a rock face the reaction forces on the annuli will tend to rotate the annuli in a direction counter to the shaft.

In use, the shaft 10 is mounted in and driven by a suitable machine. Preferably the shaft bearings are resiliently mounted. The machine is adapted to introduce water into and extract it from the chamber 26 in a controlled fashion so that when the chamber is water filled the water and the counter-weights balance each other and the machine is subjected to minimal vibration. To vary the amplitude of vibration or activation of the cutter water is withdrawn from the chamber 26 until the required degree of activation is achieved with maximum activation being reached when the chamber is empty of water.

While the chamber is filled with water under pressure small jets of water are emitted under pressure from the passages 32 to minimise the ingress of dust and other dirt into the shaft bearings. When the chamber 26 is empty pressure air could be fed to the chamber for the same purpose.

This embodiment of the invention is not limited to the precise details as herein described. For example, the chamber 26 could be counter-balanced by a second substantially identical chamber in place of the counter-weight 34. In this event the assembly would be unbalanced or activated by introducing water into one of the chambers.

In FIGS. 3 to 6 like reference numbers denote like components to those illustrated and described with reference to FIGS. 1 and 2.

In normal use each of the assembly annuli 20 and 22 would carry the same type of rock cutting formations and the different types illustrated in the FIG. 3 and 4 embodiment of the assembly are by way of illustrative example only.

The annulus 22 of the roller 18 in FIG. 3 is shown to consist of a ring 38 which carries three hard metal saw blades 40, two spacer rings and a lock ring 42 which is fastened in any suitable manner to the ring 38. The blades 40 and the spacer rings which separate them are preferably keyed against relative rotation in any suitable manner to the ring 38.

In practice the blades 40 would be of a larger diameter than those shown in the drawing for their teeth to be well clear of the remainder of the assembly. The teeth of the blades are preferably provided with hard metal cutting tips.

In this embodiment of the invention the activation of the assembly is achieved by movable heavy metal holed plates 44 which are locked to the hubs 16 and 18 of the rollers over the shaft 10 by bolts 46. The bolts pass through slots 48 in the plates so that the plates may be movable relatively to the shaft 10 in the direction of the arrows in FIG. 4. With the plates concentrically located about the shaft 10, as shown in the drawings, the assembly is balanced about the shaft axis with the required degree of activation being achieved by moving the plates in one way or the other in the direction of the arrows. The plates are moved by releasing the bolts and again tightening them in the required position over the slots 48. The plates 44 could carry index marks adjacent the slots to ensure that both plates are moved by equal distances relative to the bolts 46.

In the FIG. 5 and 6 embodiment the hubs 16 and 18 of the assembly carry annular grooves 50 which have spaced bolt holes 52 in their bases. This assembly is activated by repositioning, adding or subtracting weights 54 from the grooves 50 in a desired relationship on either side of the assembly. The weights are made from heavy metal, are holed and held in the grooves 50 by bolts 56 which engage in the holes 52.

Although only double roller assemblies have been illustrated and described in this specification, single roller assemblies are included in the scope of the invention. The single roller assemblies could include any one of the rollers described above and could be driven from one side only.

The invention is not limited to the precise constructional details as herein described. For example, the rollers 12 and 14 could be separate from and rotatably mounted on the shaft 10 which would then pass through them with any suitable means being employed to drive the roller hubs on the shaft. Additionally the assembly could, in the case of multiple rollers, include three or even more offset rollers to increase the impact frequency of the assembly rock cutting formations on the rock being cut. It is essential, however, that the axes of the eccentric rollers are so arranged around the shaft axis that the rollers counter-balance each other in the assembly.