BACKGROUND OF THE INVENTION
THIS invention relates to a rotary rock drill.
Rotary screw feed diamond drills are used widely for drilling rock in underground mines. A typical example of a known screw feed diamond drill is illustrated in Figures 1 and 2 of the accompanying drawings. The drill has a hollow feedscrew 10 carrying a chuck 12. A drill rod 14 with a diamond bit 16 at its leading end passes through the feedscrew 10 and is gripped by the chuck 12. An air motor 18, typically a vane-type pneumatic motor, is mounted on a casing 19 and is driven by compressed air. The motor drives a gear 20 which meshes with a gear 22. The gear 22 is fast on a shaft 24 which also carries another gear 26. The gear 22 meshes with a gear 28 mounted on a quill 30 which has inwardly directed splines or keys 32 that engage in grooves or keyways 34 in the feedscrew 10, allowing the feedscrew to slide forwardly, in the direction indicated by the arrow 35, relative to the quill. The gear 26 meshes with a gear 38 carried by a feednut 40 through which the feedscrew is threaded.
Rotation of the gear 20 drives the gears 22 and 26. The gear 22 in turn drives the gear 28 and, with it, the quill 30 and the feedscrew 10, while the gear 26 in turn drives the gear 38 and, with it, the feednut 40. If the feedscrew 10 and the feednut 40 have a right hand thread, the gear ratios are selected, for a clockwise drive, such that the feednut rotates slower than die feedscrew to effect forward movement of the feedscrew, as indicated by the numeral 35. In the more common arrangement, the feedscrew and feednut have a left hand thread. In mis case the gear ratios are selected such that, for a clockwise drive, the feednut rotates faster than the feedscrew to cause the necessary forward movement of the feedscrew. The forward and accompanying rotational movement of the feedscrew 10 is transferred to the drill rod 14 which accordingly rotates and moves forwardly at the same linear and angular speed as the feedscrew, thereby to drill a hole 42 into a rock formation 44.
In a typical case, the feedscrew 10 is 1,5m long to enable a hole of corresponding depth to be drilled The lengtn or me feedscrew can nowever be problematical if the drill is situated in a mine working, such as a tunnel or passage, which has a limited width of 1,5m. If, for instance, the width of the mine working is 1,5m it is not possible to drill, because it is necessary for the feedscrew to move forwardly during drilling. Also, it is not possible to add a further drill rod at the rear of the drill rod 14 because the feedscrew already occupies the full width of the working. One solution to the problem would be to make the feedscrew 10 shorter, thereby allowing a further drill rod to be added. This reduces the available feed length and requires frequent re-chucking, which is generally impractical. Thus it will be appreciated that the conventional rock drill as described above and as illustrated in Figures 1 and 2 is unsuitable for use in mine workings of restricted width.
SUMMARY OF THE INVENTION
According to the present invention there is provided a rotary rock drill comprising a rotatable, axially immobilised leadscrew, a feednut through which the leadscrew is threaded, drive and gearing means operable to rotate the leadscrew relative to the feednut so that the feednut advances linearly on the leadscrew, linear drive transfer means operating in use to transfer the linear advance of the feednut to a drill rod parallel to and spaced apart from the leadscrew, and rotary drive transfer means operating in use to transfer rotation of the leadscrew to the drill rod during linear advance of the mill rod.
In the preferred embodiment, the linear drive transfer means comprises, a drillhead to which are connected both the feednut and a spindle to which the drill rod can be chucked.
In this embodiment, the rotary drive transfer means comprises a quill which is rotationally fast with the leadscrew and a gear train, including gears fast with the quill and with the spindle respectively, for transferring rotation from the leadscrew to the spindle, and hence to a drill rod chucked in use to the spindle.
The drive and gearing means may comprise a more dring diffenteis speens so that there is relative rotation between the leadscrew and the feednut which causes the feednut to advance on the leadscrew.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail, with reference to the accompanying drawings in which:
Figure 1 shows a diagrammatic, partly sectioned side view of
a conventional rock drill;
Figure 2 shows a cross-section at the line 2-2 in Figure 1; and
Figure 3 shows a diagrammatic, partly sectioned side view of
a rock drill according to the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
As described above, Figures 1 and 2 illustrate a conventional rock drill which suffers from the disadvantage that it is unsuitable for use in mine workings of restricted width.
This drawback of the conventional rock drill is addressed by the rock drill proposed by the present invention and a preferred embodiment of which is illustrated in Figure 3. In this embodiment, the feedscrew 10 of Figure 1 is replaced by a solid leadscrew 100 which is mounted for rotation in bearings 102 carried by a cradle 104. An air motor 106, conveniently of the same type as is used in conventional drills, is mounted to the cradle and drives a gear 108 which meshes with a gear 110 fast on the leadscrew 100.
Thus the leadscrew 100 rotates at a speed dependent on the output speed of the motor and the ratio of the gears 108 and 110. The leadscrew passes through a quill 112 which, like the quill 30 in Figure 1, has inwardly directed splines or keys which engage in grooves or keyways 114 in the leadscrew. Thus rotation of the leadscrew causes corresponding rotation of the quill.
The quill carries a gear 115 which meshes with a gear 116 on a shaft 118 which also carries a gear 120. The gear 120 meshes with a gear 122 carried by a feednut 124 through which the leadscrew is threaded. The gear 116 meshes with a gear 126 on a spindle 128 through which a drill rod 130 passes. The drill rod 130 is chucked to the spindle by a chuck 132.
The spindle 128 is connected to a drillhead 134 which is also connected to the feednut 124. The ratio of the gear train consisting of the gears 115, 116, 120 and 122 is chosen so that there is relative rotation between the leadscrew 100 and the feednut 124 which causes the feednut to screw forwardly on the leadscrew. The forward movement of the feednut 124 is transferred to the drillhead 134, spindle 128 and drill rod 130, as indicated by the arrow 136. Thus the drill rod is driven forwardly at the same linear speed as the feednut and is rotated at a speed determined by the output speed of the air motor 106 and the relative ratios of the gear trains consisting of the gears 108,110 and 115, 116 and 126.
Referring again to the prior art configuration of Figures 1 and 2, re-chucking of the drill can be effect by disconnecting the drive to the feednut 40. The feednut is then held stationary by means of a lever engaged with a hole in the feednut
The motor 18 is driven in a direction opposite to that used for drilling, i.e. anticlockwise. This retracts the feedscrew. The retraction takes place at high speed because the feednut 40 is stationary and there is accordingly substantial relative movement between the feednut and the feedscrew. Prior to retraction of the feedscrew 10, the chuck 12 is loosened. After retraction a new drill rod is fitted and the chuck 12 is re-tightened.
In the embodiment of Figure 3, a similar procedure can be carried out during re-chucking. In this case, The drive to the feednut 124 is disconnected, the feednut is held stationary and the motor 106 is reversed to retract the drillhcad 134 at a rapid rate.
It will be appreciated that this method of re-chucking requires a bidirectional motor 18, 106. The necessity for a bidirectional motor 18, 106 can be avoided in cases where the feednut 40, 124 and feedscrew 10 or Ieadscrew 100 have a left hand thread. During drilling, the gear ratios are selected such that, for a clockwise drive, the feednut 40, 124 rotates faster than the feedscrew 10/leadscrew 100, thereby to generate forward movement of the feedscrew 10 or drillhcad 134. When re-chucking is to take place, the feednut 40. 124 is held stationary so that the clockwise drive applied to the feedscrew 10/leadscrew 100 causes the feedscrew or drillhead to retract rapidly.
The configuration illustrated in Figure 3 has an important advantage when compared to the conventional configuration of Figure 1. The spindle 128 can much shorter than the feedscrew 10, because the feed length is not determined by the spindle, but by the feed length of the Ieadscrew 100.
The length of the spindle 128 together with the chuck 132 may, for instance, be as little as 0,5m as opposed to the typical 1,5m feedscrew employed in the conventional arrangement This in turn means that, in a mine working having a restricted width of, say, 1,5m, another drill rod of l,0ra length can be added behind the drill rod 130. The feed length which is attainable in each instance is determined by the distance that the feednut can advance on the leadscrew 100. However the length of the leadscrew may be only slightly less than the width of the mine working, because it does not move axially as in the conventional system, thereby allowing a substantial feed length to be obtained.

We Claim:-
1.
A rotary rock drill'comprising a rotatable, axially immobilised leadscrew, a feednut through which the leadscrew is threaded, drive and gearing means operable to rotate the leadscrew relative to the feednut so that the feednut advances linearly on the leadscrew, linear drive transfer means operating in use to transfer the linear advance of the feednut to a drill rod parallel to and spaced apart from the leadscrew, and rotary drive transfer means operating in use to transfer rotation of the leadscrew to the drill rod during linear advance of the drill rod.
2. A rotary rock drill according to claim 1 wherein the linear drive transfer
means comprises a drillhead to which are connected both the feednut and a spindle to which the drill rod can be chucked.
3. A rotary rock drill according to either one of the preceding claims wherein the rotary drive transfer means comprises a quill which is rotationally fast with the leadscrew and gears, including gears fast with the quill and with the spindle respectively, for transferring rotation from the leadscrew to the spindle, and hence to a drill rod chucked in use to the spindle.
4. A rotary rock drill according to any one of the preceding claims wherein the drive and gearing means comprises a motor driving gears which operate to rotate the Ieadscrew and feednut at different rotational speeds so that there is relative rotation between the Ieadscrew and the feednut which causes the feednut to advance on the Ieadscrew.
5. A rotary rock drill substantially as herein described with reference to Figure
3 of the accompanying drawings.