This invention relates to a rock drill comprising a housing, shank adaptor means connectable to a drill stem, the shank adaptor means having a non-circular part and a shoulder, a rotary member having a non-circular portion in axially sliding connection with the said non-circular part of the shank adaptor means for locking the rotary member and the shank adaptor means together rotationwise but permitting axial movement therebetween, rotary bearing means rotatably mounting the rotary member in the housing, a rotary motor coupled to said rotary member for rotating same, percussive means for repeatedly applying longitudinal thrust on to the shank adaptor, a thrust bush means arranged to be in engagement with said shoulder of the shank adaptor means to transmit a feeding force from said housing to said shank adaptor means when such a feeding force is applied to the housing, a pressure chamber operatively coupled between the housing and said thrust bush means, and means for pressurizing said chamber. Such a rotary percussive rock drill is- shown in US-A-4494 614.

It is an object of the invention to provide a rock drill of the kind described above which is capable of acting as a rotary percussion drill and alternatively as a rotary drill. This object is achieved by the features given in the characterizing part of claim 1.

An embodiment of the invention will now be described by way of example with reference to the drawings.

In the drawings: -

Fig 1 is a front view of the drill of the invention.

Fig 2 is a section on line C - C of Fig 1 but with certain parts shown in outside view.

Fig 3 is a section on line A - A of Fig 2, and

Fig 4 is a schematic hydraulic circuit of the drill.

Referrring new to the drawings, there is shewn an hydraulically operated drill 10 for use on a rock drilling rig. The drill 10

comprises a main housing 12 which is substantially rectangular in section at its rear end and which has a smaller substantially square forward portion 14 extending from one half of the side only.

Within the housing 12 there is a main bore 16 which extends through the longer portion of the housing and a smaller chamber 18 which is a parallel thereto and is in the larger part of the housing 12. There is ^" a large rear opening 20 from the bore 18 and within this is received the front end of an hydraulic rotary motor 22, the drive shaft 24 of which is splinedly connected to a drive pinion 26 carried in needle bearings 28. The teeth 30 of the pinion 26 mesh with the teeth 40 on a main rotary gearwheel 42 carried in the bore 16 by means of two sets of taper roller bearings 44. The front end of the bore 18 is closed off by a removable cover 46. A filling opening to the bore 18 is closed by a plate 48 which carries a grease nipple 50.

Spacers 52 each having an inwardly directed rim 54 are provided at each side of the main gear wheel 42, the rims 54 butting against the outer races of the taper roller bearings 44. Sealing rings 56 act between each spacer 52 and the respective housings 12 and 14 thereby providing a substantially sealed space which is packed with lubricating grease.

A shank adapter 58 extends along the bore 16 projecting beyond an opening in a bearing bush 60 at the front end of the drill 10. The shank adaptor 58 has a female threaded drill stem receiver 62 at its front end, a land 64 inwardly of the free end and terminating in a sharp shoulder 66. The rear end of the main part of the shank adaptor 58 is provided with splines 68 and the splined portion leads on to a short anvil 70 of smaller outside diameter. The splines 68 engage the splines in a bush 72 the outer surface of which is generally triangular with rounded sides and radiused corners (best shown in Fig 3) which fits in a correspondingly shaped recess 74 in the main gear wheel 42. This non-circular shape of the bush 72 and the spline connection ensures that the drive from the gear wheel 42 will be passed to the shank adaptor 58.

The bore 16 is of variable diameter throughout the length of the housing 12. At the rear end of the housing it has two stepped cylindrical portions 76 and 78 for the reception therein of the front end of a percussion mechanism 80. Beyond an enlarged portion 82 of the bore 16 which provides the housing for the main gearwheel 42, the bore continues as a throat 84, a bigger diameter portion 86 which increases into an enlarged diameter portion 88, there being a still larger diameter groove 90 between the portions 86 and 88 for the purpose which will become apparent. The enlarged bore portion 88 continues towards the rock drill front with a smaller diameter portion 92 and this leads to a slightly smaller portion 94 and thence to an outlet throat 96.

The percussion mechanism 80 is not described in detail. It comprises a non-illustrated hammer piston that is reciprocably driven to repeatedly impact on the anvil 70. The impact frequency can typically be 50 Hz. The percussion mechanism 80 can for example be of the kind described and shown in US-A-4 494 614.

A water control bush 98 is received within the portion 92 of the bore 16. This bush 98 has a main enlarged internal annular groove 100. Lip seals 101 are contained within grooves in the bush 98 on either side of the main groove 100. The groove 100 connects via a conduit (not shewn) with an annular groove 102 in the wall of the bore part 92. An externally opening water conduit 104 is connected to the groove 102. Internal waterways 105 are provided in the shank adaptor 58 opening into the groove 100 and then leading via an axial bore 106 to the bore 62, 0-ring seals 108a_, 108b and 108 are provided in grooves in the bush 98 on either side of the space which will be open to the groove 102. A bleed port 110 to atmosphere is provided through the housing portion 14 beyond the middle 0-ring seal 108b.

A front end bearing bush 112 is provided in the front end of the groove part 92.

Surrounding the main portion of the shank adaptor 58 is a thrust bush 116 having a flange 118 at its forward end with an enlarged mouth 120 to receive the shoulder 66 of the shank adaptor 58.

The bush 112 has a mouth 113 into which the forward end of the land 64 can be received in substantially sealing engagement to act as a cushion on the forward movement of the shank adaptor. Similarly the mouth 120 of the thrust bush 116 has an inwardly directed lip to seal against the land to provide a cushioning on relative rearward movement between the shank adaptor 58 and the thrust bush 116.

The base 122 of the mouth 120 in the thrust bush 116 serves as an abutment surface that butts against the shoulder 66 on the shank adaptor. The inner end of the shank adaptor 116 has a conical surface 124 that engages a conical surface 126 of identical cone angle formed on a brass thrust bearing 128 which is let into a recess at the forward end of the main gear wheel 42.

Surrounding the thrust bush 116 is a damper bush 132. The damper bush 132 has a smaller diameter rear portion 134 and larger diameter front portion 136 which fit respectively in the bore parts 86 and 88. At its forward end, the larger diameter portion 136 of the damper bush 132 is provided with a socket part 138, the base 140 of which butts against the rear surface 142 of the flange 118 of the thrust bush 116.

Between the smaller and larger diameter portions 134 and 136 of the damper bush 132 is a double inclined conical surface 144 that is located within the groove 90.

Both the damper bush 132 and the thrust bush 116 are capable of axial movement from a rearward position to a forward position.

The groove 90 is (which forms a damper chamber as will be described) connected via bore 147 and through a port 146 to a source of hydraulic fluid under pressure (indicated generally at 148 in Fig 4). This source 148 leads to a selector valve 150 which is

connected alternately to a rotary supply line 152 (hereinafter called the "rotary supply line") and another percussion supply line 154 (hereinafter called the "percussion supply line"). The rotary supply line 152 leads to the rotary motor 22 via a control valve 156. The exhaust line 158 from the rotary motor 22 also passes through the ^' control valve 156. The percussion supply line 154 is conncected via a control valve 160 to the percussion mechanism 80. The exhaust line 162 from the percussion mechanism 80 also passes through the control valve 160. An accumulator 164 is connected in the percussion supply line 154 close to the percussion mechanism 80. Teed off the percussion supply line 154 downstream of the control valve 160 is a connector line 166 that leads via a regulator 168 and a one-way valve 170 to the rotary supply line 152. A damper line 172 leads from the percussion supply line 154 between the connector line 166 and the accumulator 164 to the damper chamber 90 via the port 146.

The drill 10 can be used in either a percussion mode (which is in fact a roto-percussion mode as will be described apparant from the following and this specification must be construed accordingly) or a rotary mode. Which mode it will operate will depend upon the setting of the selector valve 150 by an operator.

In the percussion mode, hydraulic fluid is supplied, under control from the operator using the control valve 160, via percussion supply line 154 to the percussion mechanism 80 and to the chamber formed by the groove 90. Hydraulic fluid is also supplied to the rotary motor 22 via the connector line 166, the regulator 168 and the rotary supply line 154.

The chamber 90 also has hydraulic pressure supplied thereto via the percussion supply line 154 and damper line 172. This pressure acts on the piston surface 144 and moves the damper bush 132 forwardly. In so doing the damper bush 132 moves the thrust bush 116 axially into its forward position and causes the shank adaptor also to move forwardly. In this forward position shown in Fig 2b, the reaction surface 124 of the thrust bush is spaced a substantial distance from

the surface 126 of the thrust bearing 128. The forward position of the damper bush 132 is defined mechanically by the front surface of the damper bush butting against a surface 190 rn the housing 12. When the damper bush 132 is forced into its forward position, the thrust bush 116 has some slideability (about a millimeter or so) in its forward position. This is only a matter of choice; the damper bush 132 and the thrust bush 116 could as well be integral.

The piston of the percussion mechanism will now be caused to reciprocate and to strike the anvil 70 causing repetitive percussive blows to be transmitted via the shank adaptor 58 to the drill stem. At the same time the rotary motor 22 will be rotating the main gear wheel 42 to permit the drill bit to be rotated. It will be noted that due to the provision of the regulator 168, the rotary motor 22 will not rotate at as high a rate as it does in the rotary mode, where, as will be described, all the fluid power is supplied to the rotary motor 22 but will merely cause the drill to turn between impacts.

When during drilling, a feeding force is applied to the housing 12 of the rock drill, a part of the force is used to balance the reaction forces for reciprocating the hammer piston of the percussion mechanism 80. The remaining part of the feeding force applied to the housing 11 is transmitted through the pressurized hydraulic fluid in the chamber 90 to the piston surface 144 of the damper bush 132 and conveyed through the thrust bush 116 to the shoulder 66 of the shank adaptor 58 and ultimately taken up by the contact between the drill bit and the rock. The axial force on the piston surface 144, that is the force transmitted by the chamber formed by the groove 90, should be great enough to prevent the damper bush 132 to yield unless there is a reflected shock wave as will be described.

During rotary drilling, the chamber 90 is depressurized and the shank adaptor 58 is therefore in its rearward position.

The reflected shock waves propagating from the drill bit backwardly through the drill stem will act through the shoulder 66 against the surface 122. These forces then pass to the damper bush 132 via the reaction surface 140 and bush surface 144. The forces will then be dampened by the hydraulic fluid in the chamber formed by groove 90 and by the accumulator 164 to which the damper line 172 is connected as has been described above. As the reaction surfaces 124 and 126 are spaced apart no forces will be applied to the thrust bearing 128 or to the taper roller bearings 44. Because the surfaces 142 and 140 will move slightly apart due to the shock effects between them, air entraining the lubricant can easily pass therebetween to ensure that there is adequate lubrication at this point. The surface 190 is lubricated in the same way and part of the lubricant conduits 182 are formed as grooves in this surface to further improve the lubrication.

In the rotary mode, all the hydraulic fluid is passed to the rotary drive 22, which will thus rotate more quickly that when the drill is operating in the percussive mode. The drill shank will in use be pressed rearwardly due to reaction forces emanating from the contact between the drill bit and the rock. Consequently the rear surface 124 of the thrust bush will butt against the surface 126 of the thrust bearing 128 and will rotate therewith. Because the reaction forces are constant and non-percussive, the tapered roller bearings are able to absorb these forces without failure ever a long working life.

It should also be noted that a bleed line 174 containing a pressure restrictor 176 is provided leading from the seals 178 on either side of the chamber 90 to the bleed line for the rotary motor 22 and hence to drain. This bleed line 174 assists the chamber 90 to cope with pressure peaks ^' and to extend the wearing life of the damper bush 132. The arrangement can be as described in US-A-4 494 614.

An inlet nipple at the rear of the housing 12 permits air having entrained oil lubricant to be supplied to a lubricant path. This path comprises the bore 16, the space between the conical surfaces

124 and 126 and between the thrust and damper bushes 116 and 132. The lubricant conduits 182 are connected to the space between the parts so that the air with entrained lubricating oil can be brought towards the forward end of the shank adaptor 58.

We have found that the rock drill above described is efficient and robust able to withstand the internal shock forces when in the percussive mode and yet able also to operate at high rotational ^' speeds when in the rotary mode.

The invention is not limited to the precise constructional details hereinbefore described and illustrated in the drawings but can be varied within the scope of the claims. For example, although the invention has been described with reference to a hydraulic rock drill, it can also be applied on a pneumatic rock drill. The damper chamber 90 can be pressurized with an hydraulic fluid as described or it can be pressurized with a gas. A gas filled chamber can be used also in an hydarulic rock drill.