GB2169333A

GB2169333A - A rotary head

Info

Publication number: GB2169333A
Application number: GB08517815A
Authority: GB
Inventors: Ming Luen Lam
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-01-04
Filing date: 1985-07-15
Publication date: 1986-07-09
Also published as: GB8517815D0; GB8500190D0; JPS61162695A; GB2169333B

Abstract

A rotary head for a drilling machine comprises lower, intermediate and upper means (1, 3 and 61 or 62) for engaging a plurality of drilling tools; means (5) for rotating drilling tools engaged by the engaging means of a speed which is adjustable; and flushing means comprising a plurality of flushing apertures (35, 44, 11 or 52) for supplying flushing fluid to or from drilling tools engaged by the engaging means. <IMAGE>

Description

SPECIFICATiON A rotary head This invention relates to a rotary head for a drilling machine, for example a drilling machine for use in harbour construction, the construction of foundations for bridges or highways or trailways, tunnel drilling and the like.

Most previously proposed rotary heads used in the reverse-circulation drilling method have a flushing outlet at the upper end thereof and a connection device, for example a screw-threaded end, for connection to a drilling tool at the lower end making it necessary to attach a one inch (2.54 centimetres) air pipe fitting outside of the drill pipe or tools and to make sure that every drill rod is in line with the air pipe so that a considerable amount of time required to assemble and disassemble parts such as the drill string and tools for use when necessary. Thus, such a rotary head has a very low efficiency or productivity.

Recently, over-drillng methods have been proposed in which a drill rod and a drill casing can be rotated simultaneously to drill into the ground to be bored. Although, such an arrangement has increased efficiency, the drill rod cannot be seen from the outside and therefore, when the drill casing is unscrewed, the drill rod may easily become unscrewed without being noticed and may therefore drop into the bore.

Furthermore, previously proposed rotary heads normally have a rotation speed below 50 revolution per minute (rpm), the highest speed being approximately 100 rpm, and the efficiency of drilling bits such as roller bits or diamond bits canot be maximised at such low speeds so that such rotary heads have a poor uneconomic performance.

It is an object of the present invention to overcome or at least mitigate the above mentioned problems.

According to one aspect of the present invention there is provided a rotary head for a drilling machine, the rotary head comprising means for engaging a plurality of drilling means; means for rotating drilling means engaged by the engaging means at a speed which is adjustable; and flushing means comprising a plurality of flushing apertures for supplying flushing fluid to or from drilling tools engaged by the engaging means.

In a second aspect, the present invention also provides a rotary head for a drilling machine, the rotary head comprising upper, intermediate and lower engaging means spaced apart on the rotary head for each engaging one or more drilling tools, flushing means comprising three flushing apertures for supplying flushing fluid to or from drilling tools engaged by the engaging means, and means for rotating the drilling tools engaged by the engaging means at a speed which is adjustable.

The present invention also provides a multi-connection, multi-flushing aperture and multi-speed rotary head comprising a gear box, a hydraulic pipe unit, a lower flushing aperture, a lower connection device for engaging a drillng tool, an intermediate flushing aperture, an intermediate connection device for engaging a drilling tool, an upper flushing aperture and an upper connection device for engaging a further drilling tool (paragraph 6).

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a top plan view of a rotary head in accordance with the invention; Figure 2 is a side view of the rotary head of Fig. 1; Figure 3 is a cross-sectional view taken along the line A-A' of Fig. 1; Figure 4 is a cross-sectional view taken along the line B-B' of Fig. 2; Figure 5 is a rear view of the rotary head shown in Fig. 1; Figure 6 is a front view of the rotary head shown in Fig. 1; Figures 7A and B show the structure of a hydraulic jack of the rotary head of Fig. 1; Figure 8 illustrates a previously proposed reverse-circulation drilling method; Figure 9 illustrates a method of reverse-circulation drilling using a rotary head in accordance with the present invention;; Figure 10 illustrates a further method of reverse-circulation drilling using a rotary head in accordance with the present invention; Figure 11 illustrates a method of circulation drilling using a rotary head in accordance with the present invention; Figure 12 illustrates a further method of circulation drilling using a rotary head in accordance with the present invention; Figure 13 illustrates a method of horizontal reverse circulation drilling using a rotary head in accordance with the present invention; Figure 14 illustrates a method of drilling stony or rocky ground using a rotary head in accordance with the present invention; Figure 15 illustrates a method of over-burden drilling using a rotary head in accordance with the present invention; Figure 16 illustrates a further method of over-burden drilling using a rotary head in accordance with the present invention;; Figure 17 illustrates a method of grouting during ground anchoring using a rotary head in accordance with the present invention; Figure 18 is a schematic plan view of a three-stage connection device or adaptor of the rotary head shown in Fig. 1; and Figure 19 is an enlarged view of part of a thread of the adapter as shown in Fig. 18.

Referring now to the drawings, Figs. 1, 2 and 3 show a rotary head in accordance with the invention for use in a drilling machine to rotate drilling tools such as drilling rods, drilling casings etc.

As shown, the rotary head has a first or lower internally screw-threaded end portion or connection device 1 for engaging a drilling means, for example a drilling rod casing to form a joint therewith. A first or lower flushing unit 2 having a flushing aperture 35 is provided adjacent the connection device. A second connection device for engaging a drilling tool comprises a flange adapter which is received in a top end of the rotary head. As shown in Fig. 3, different types of adapters can be used, for example either a three-stage adapter 62 or a single stage adapter 61 as will be described in detail hereinafter. Each of the adapters has a central top flushing channel for supplying flushing fluid to or from a drilling tool.A further connection device in the form of a hydraulic clamp unit 3 is provided intermediate the first and second connection devices and a further or upper flushing aperture 44 is also provided intermediate the lower and top apertures. A main shaft 27 of the rotary head has a gear box 5 mounted thereto. The gear box 5 is a two-speed gear box having a speed-control lever 6 which allows the speed of rotation of the rotary head to be controlled by changing the transmission gear ratio as will be described in detail hereinafter.

The first or lower connection device 1 as an internally screw-threaded cylindrical end section for engaging an externally screw-threaded end section of a drilling tool. In the preferred arrange ment, the screw-thread has two turns per inch (TP1) (0.8 turn per cm) and a four degree taper so that the first connection device can be used to engage either a ten inch (25.4cm) or twelve inch (30cm) drill casing. The screw thread may be either left or right handed as required. The lower flushing aperture 35 (Fig. 3) is preferably of 6 inches (15 cm) internal diameter and can function either as a flushing fluid inlet or a flushing fluid outlet during drilling.

The hydraulic clamp unit 3 comprising the further connection device is located between the gear box 5 and the first connection device and comprises two hydraulic piston and cylinder arrangements or jacks 23 and a clamp system. The structure of each jack 23 can been most clearly in Figs. 7a to 7c. The piston 23a and cylinder 23b of each hydraulic jack 23 are connected by spherical bearings to respective supporting places 24 and 30 (Fig. 3). The supporting plate or member 24 surrounds a main shaft 27 of the rotary head and is keyed thereto so as to be slidable therealong within a distance of 35mm but so that the supporting plate 24 cannot rotate relative to the shaft 27. The upper supporting plate 30 is connected to the bottom of the gear box 5 by 16 screws of M12X1.5.

As shown in Fig. 3, four jaws 21 are mounted inside the supporting member 24 so that the lower part of each jaw 21 extends into a repective elongate slot 27a extending axially of the main shaft 27 so that the jaw can slide along the slot. An upper part of each jaw has an enlarged head portion which is received within an annular groove defined by a deformed end portion 22 a of a bearing sleeve 22 provided between the main shaft 27 and the supporting member 24. Thrust ball bearings 28 and plain bearings 26 are provided between the bearing sleeves 22 and the supporting member 24. An adjusting nut 25 is provided to lock the plain bearings 26 so that the bearing sleeves 22 and supporting member 24 are slidable along the main shaft 27 as a single unit while the bearing sleeve 22 can still rotate relative to the supporting member 24.Blocks or limit means are mounted within the annular groove of the bearing sleeve 22 to limit movement of the jaws 21 relative to the groove so that, when the jaws 21 rotate with the main shaft 27, the bearing sleeve 22 will also rotate.

The hydraulic jacks 23 are provided to slide the supporting member or plate 24 along the main shaft 27 as described above. The cylinder of each hydraulic jack 23 is four inches (10 cm) in internal diameter and so has a cross-sectional area of 12.56 square inches (81.03 cm2) to provide a push force of 25 tonnes when the hydraulic pressure applied thereto is 2,200 pounds per square inch (PSI) (1.52X107Nm 2) so that the resultant force applied to the supporting member 24 by the two cylinders is 25 tonnes. Each of the jaws 21 has an 8" external taper and is provided with hardened teeth to clamp the outside diameter of a drilling tool such as a drill casing or pipe received within the rotary head. A push force of approximately 6 tonnes is applied to each jaw 21 when a force of 25 tonnes is applied to the four jaws by the bearing sleeve 22 when the hydraulic jacks 23 are actuated. As shown in Fig. 3, the 8" tapered outer surfaces of the drawers engage correspondingly tapered inner surfaces of a sleeve 21a which causes the jaws to move together as they are pushed downwardly toward the first connection device so that a pipe placed within the main shaft 27 is gripped by the jaws 21 and thereby clamped tightly. The force supplied to the surface of a pipe or casing gripped by the jaws 21 will be 220 pounds per square inch (1 .52X 106Nm-2) as the four jaws 21 each have a teeth area of 9 square inches (58cm2) and a force of 0.9 tonnes is applied thereto.As the compressive strength of stainless steel pipe is not less thn 2000 PSI (1.37X107Nm the pipe will not be damaged by the jaws 21. Moreover, the hydraulic clamp unit 3 allows the pipe to rotate either in the clockwise or the anti-clockwise direction with the rotary head during drilling.

Referring now to Figs. 3 and 4, the gear box 5 is, as mentioned above, mounted to the main shaft 27.

As shown in Figs. 3 and 4 the gear box 5 has three subsidiary shafts 27b arranged above and in parallel to the main shaft 27. The outermost subsidiary shafts 27' b are connected directly to the drive shafts of respective hydraulic motors 8 while the middle or intermediate shaft 27b transmits power from the hydraulic motors 8 to the main shaft 27 via the gear arrangement which will now be described.

Two large gears 12(Z1) and 13(Z2) are mounted on the main shaft 27 which has an internal diameter of 200mm. The large gear 12 has 52 teeth and has a pitch diameter of 416 mm while the other large gear 13 has 45 teeth and has a pitch diameter of 360mm. Thus each of the large gears 12 and 13 is of module 8. Three gears 14 (Z3) 15(Z4) and 16(Z5) are mounted on the intermediate subsidiary shaft 27b. The speed-control lever or handle 6 is provided so as to move the gears 14 and 15 axially along the intermediate subsidiary shaft 27b so that either the gear 14 engages with the large gear 12 or the gear 15 engages with the large gear 13 to transmit power to the main shaft 27. The gear 14 has 13 teeth and a pitch diameter of 104mm while the gear 15 has 20 teeth and a pitch diameter of 160 mm thus giving each of the gear 14 and 15 a module of 8.

The outermost subsidiary shafts 27'b are gear shafts 17 (Z6) which have 12 teeth and a pitch diameter of 60mm. The gear shafts 17 engage a further gear 16 carried by the intermediate subsidiary shaft 27b, the gear 16 having 48 teeth and a pitch diameter 240mm so that it is of module 5. A respective ring gear 18 having 10 teeth and a pitch diameter of 30mm is mounted to each of the outermost shafts 27'B and engages a respective identical gear 19 mounted on the shaft of the corresponding hydraulic motor 8 to transfer power from the motor 8 to the associated gear shaft 27 b.

When the hydraulic motors are capable of from 0 to 1800 RPM the RPM of the main shaft 27 is: 60 104 First Speed (0-1800) X X --(0-112.5) RPM.

240 416 when the gear 14 engages the large gear 12; and 60 160 Second Speed (0-1800) X X =(0-200) RPM.

240 360 when the gear 15 engages the large gear 13.

If the hydraulic motors 8 are connected in series then the speed of the main shaft 27 will be doubled to a maximum of 400 RPM.

An upper connection element 76 comprising an upper or intermediate flushing unit 9 in which the second connection device or adapter is received is secured to an upper end of the main shaft by means of respective screws passing through 16 screw holes 77 provided in the connection element 76 aligned with corresponding screw holes 41 provided in the end of the main shaft 27 so that the connection element 76 rotates with the main shaft 27. The connection element 76 has two collars 45 one adjacent the main shaft and one adjacent the other end of the connection element, both of the collars 46 being tightened around the connection element by means of screws 78. The upper or intermediate flushing unit has an aperture 44 which is provided between the two collars 46. Bronze flanges 46 are provided on either side of the flushing aperture 44 to support a flushing pipe 44a.U-shaped oil seal rings 47 are provided within the internal diameter of the bronze flanges 26 and are locked in position by means of circlips 79. The internal diameter of the flushing aperture 44 should be large enough to enable the aperture to function either as a flushing inlet or a flushing outlet.

The second connection device or adapter 61 or 62 can be connected, as shown in Figs. 1 to 3 to the upper end of the connection element 76 by means of 16 screw connections 48. Fig. 3 shows a first adapter 62 connected to the connection element 76 and also shows a second alternative adapter 61 separate from the rotary head.

As shown most clearly in Fig. 3, the adapter 61 has a single externally screw-threaded adapter section 50 which has a four degree external taper and two threads per inch (0.79 threads per cm), the screwthread being either left or right handed. The single screwthreaded adapter section 50 is designed to engage a drill casing of large diameter, for a drill casing of five inches, six inches or seven inches (12.7cm, 15.24 cm or 17.8cm) diameter. However as only one diameter of casing may be connected to the single adapter section adapter 61, it will be necessary to provide different sizes of adapter 61 to fit different diameter casings, for example three different adapters 61 for three different diameter casings, if is intended that a single section adapter such as the adapter 61 only be provided.However, the adapter 61 has the advantage of enabling a large central bore 52 to be formed therein to provide a further flushing fluid inlet or outlet. The reference numeral 51 indicates holes for connecting the adapter 61 to the end of the connection element 76.

The other adapter 62 is a three-stage flange adapter which has the advantage of allowing three different diameters of casings or rods to be connected thereto but the disadvantage of providing only a small diameter central flushing bore 11. Thus, typically, the diameter of the flushing bore 11 is only 12 inches (3.8 cm) and the flushing bore 11 can therefore only be used as an inlet for flushing fluid. When the three-stage flange adapter 62 is used, the upper or intermedate flushing pipe 44a should be removed to enable an operator to ensure that drill rods or cases connected to the adapter 62 are not unscrewed inadvertently.

The flange adapter 62 is shown more clearly in Fig. 18. Thus, the flange adapter has three externally screw-threaded adapted sections 10a, 10b, and 10c, which decrease in diameter stepwise from the iargest adapter section 10a to the smallest adapter section 10c. Preferably, the screwthread of the top or smallest adapter section 10a extends in the opposite direction to the screw-threads of the larger adapter sections 10a and 10b and conveniently the adapter section 10a has a left-handed screw-threaded and the other two have a right handed screwthread. This arrangement is designed to prevent a drill rod carried by the smallest adapter section 10a being accidentaly unscrewed when a drill casing carried by one of the other two adapter sections is unscrewed.

Fig. 19 illustrates schematically and on an enlarged scale the profile of the screw-thread of the adapter sections shown in Fig. 18. As shown in Fig. 19, the thread is a 45" or 90" thread having a pitch diameter of 12mm and a depth of 3mm. Such a type of thread can withstand the impact forces and torsion forces which may be applied thereto by a drill rod or other drilling tool during drilling and, moreover, is the same as that of various kinds of drill rods or drill tools to ensure correct connection thereto.

As will be appreciated, the rotary head described above may be used in many drilling methods. However, various examples of the use of the rotary head will now be described with reference to Figs. 8 to 17.

Fig. 8 illustrates a present method of reverse-circulation drilling in a sea or river bed, the surface of the sea or river being indicated by the reference numeral 116. In the present method, when a pile tube 100 has been inserted at the position at which it is intended to form the bore, a specially made reverse-circulation drilling tool 101 of 6 inch or 7 inch (15cm or 18cm) in diameter has to be assembled from specially made flanged sections 101a and inserted into the pile tube 100 making sure that an 1 inch to 0.75 inch (2.5cm to 1.9cm) air pipe 102 running along the drilling tool 101 is in line, is not constricted and is secured in place. Next, the bottom of the reverse circular drilling tool is connected to a specially made drilling bit 101b and an air jet nozzle 104 at the end of the air pipe 102 is inclined upwardly.A specially made connection element or adapter 103 for providing an appropriate flushing inlet for reverse circulation has to be connected to the bottom of the rotary head 5. Then, the reverse-circulation drilling tool 101 must be connected to the adapter 103 ensuring that the flushing inlet 35 is aligned with the air pipe 102. The rotary head 5 is then actuate to rotate the drilling tool 101 to drill downwardly and, at the same time, compressed air is pumped in through the flushing inlet 35 during drilling, drilling debris such as sea sand, mud and sediment and the like is pushed out with flow of river or sea water from the flushing outlet 11.

Fig. 9 shows a method of circulation drilling in a sea or river bed using a rotary head in accordance with the invention.

As shown in Fig. 9, a 12 inch (30cm) drilling casing 111 carrying a ring bit 112 is connected to the first connection device 1. A 7 inch (18cm) drill pipe or casing 113 also carrying a ring bit 14 is then inserted into the 12 inch (30 cm) casing 111 and is clamped into position by the hydraulic clamp unit 3. Approximately 5 feet (150 cm) above the ring bit 114 approximately ten holes 120 of one inch (2.54cm) in diameter are provided. Next, the hole or aperture 44 is blocked off and the hydraulic motor or motors 8 are actuated to rotate the drilling casings 111 and 113 to drill downwardly into, for example the sea bed 119, simultaneously. At the same time, compressed air is supplied via the flushing aperture 35 so that, during drilling, mud, clay and said 115 inside the bottom of the pile tube 100 follow the flow of water-air mixture and are forced out through the flushing aperture 11.

Fig. 10 illustrates a further new method of reverse-circulation drilling on the sea bed in which, as indicated the arrangement shown in Fig. 9, a 12 inch casing (30cm) 111 is first connected to the connection element 1 assuming that the drilling machine carrying the rotary head has been appropriately positioned over the previously inserted pile tube 100. The 12 inch casing 111 carries a ring bit 112 and may also carry a big bold blade bit 11 lea outside of the ring bit. A central bit 11 lib may also be carried by the casing 111. A five inch (13cm) diameter casing 120 carrying a five inch (13cm) ring bit 120a is then inserted inside the 12 inch casing 111. As shown in Fig. 10, approximately 10 holes 120' of one inch (2.5cm) diameter are provided approximately 1 to 2 metres above the ring bit 120a.The flushing aperture 35 is then blocked or closed and the rotary head 5 is rotated using the hydraulic motor(s) 8 to drill downwardly into the sea bed. At the same time, compressed air is fed to the drilling tools via the flushing aperture 44 and, during drilling, clay, mud and sand inside the pile tube follow the water-air mixture and are forced from the flushing aperture 11.

Fig. 11 illustrates a new central circulation flushing method in which a 12 inch (30cm) diameter drill casing 131 carrying a ring bit 131a and possibly a central drilling bit 131b is connected to the first connection device 1 and a three inch (7.6cm) diameter drill rod 137 is inserted into the casing 131 to be engaged by the hydraulic clamp 3 and/or the second connection device at the top of the rotary head. The drill rod 137 carries a full-cone roller bit 133, the top of which is blocked off and is fitted with an upwardly extending 1 inch (2.5cm) internal diameter pipe nozzle 134. A central drilling bit 135 is also fitted on the drilling rod 137.

Next, the flushing aperture 44 is blocked or closed. The rotary head 5 is then rotated to cause the two sets of drill tools to drill down simultaneously. At the same time compressed air is supplied via the top flushing aperture inlet so that, during drilling, sea sand, marine clay, etc. are forced out through the flushing aperture 35 with the flow of air and sea water.

Fig. 12 illustrates another central circulation drilling method in which compressed air is supplied via the top aperture 11. In the method illustrated by Fig. 12, the bottom joint or connection device 1 and flushing unit containing the flushing aperture 44 are removed from the rotary head 5 and a 7 inch (18cm) diameter casing 140 carrying a ring bit 140a is dropped into a pile tube 141 previously inserted at the spot where drilling is desired. Next a three inch (7.6cm) diameter drill rod 142 carrying a three cone rod bit 143 is inserted into the seven inch diameter casing and the top of the bit 143 is blocked so that no compressed air passes therethrough. A one or two pcs VP jet pipe is fitted onto the three cone roller bit 143.Next, the three inch (7.6cm) drill rod 142 is connected to an appropriate section of the three-stage flange adapter 62 and the 7 inch (18cm) diameter casing 140 is clamped by the hydraulic clamp 3. The rotary head 5 is then rotated to cause the two sets of drill tools to drill down simultaneously into the sea bed. At the same time compressed air is supplied via the top flushing aperture 11 and sand and mud inside the pile tube 141 follow the flow of water and air indicated by the arrows and are forced out through the flushing aperture 44.

Although the results obtained by the methods illustrated by Figs. 9, 10 and 12 are very good, the method illustrated in Fig. 11 provides the best results in practice.

Fig. 13 illustrates a new method of horizontal reverse-circulation drilling using a rotary head in accordance with the invention.

As shown in Fig. 13, respective 12 inch (30cm) diameter, 7 inch (18cm) diameter and 5" (13cm) right hand thread drilling tools 146, 145 and 144 are connected to the rotary head, the drilling tool 144 being connected to the single section adapter 161, the drilling tool 145 being clamped by the hydraulic clamp unit 3 and the largest diameter drilling tool 146 engaging the connection device 1. Flushing water is then supplied through the flushing aperture 35 and/or the flushing aperture 44 into the drilling tools and the rotary head 5 is actuated to cause the drilling tools to drill forwardly into the surface in which the bore is required. During the drilling, sand and mud are forced by the flushing water out through the flushing aperture 11.As the bore being drilled gets deeper and deeper, the 12 inch (30cm) casing 146 may be disconnected from the rotary head and used to support the bore. The five inch (13cm) and 7 inch (18cm) drilling tool 144 and 145 can then be used continuously to drill forward, the 7 (18cm) inch drilling tool 145 being a casing which forms a shield to protect the five inch (13cm) drilling tool 144 to prevent the drilled hole from bending or collapsing.

A similar method known as the Shieldrill with reverse circulation method has been used by the Japanse to drill a channel at Shoshidio but using a two-gear box system which is considerably more costly than a rotary head in accordance with the present invention.

Fig. 14 illustrates a new method of drilling in a rocky or stony area of the sea or river bed. In this method, a 12 inch (30cm) drilling case 147 carrying a ring bit 147a is connected to the connection device 1 and a five and a half inch (14cm) diameter size drilling rod 148 is connected to the adapter 161 or 162, the end of the drilling rod carrying a 6 and a half inch (16.5cm) diameter hole hammer 149. Compressed air is supplied via the flushing aperture 11.

Initially, the hammer 149 is pulled up to make sure that the compressed air is passing through to the bit 147a. Next the hammer 149 is lowered so that the bit 147a touches the bottom of the bore and the rotary head is rotated to drill downwardly with two sets of drilling tools, namely the hammer and the drilling bit. Sand, mud and clay are forced out through the lower flushing aperture 35 and the intermediate flushing aperture 44 by the compressed air. When the drilling bit reaches the bolder or rocky area, the speed of rotation of the drilling tools is decreased by using the speed change lever 6. At the same time, the volume and pressure of the compressed air supply is increased so as to facilitate removal of the rock or bolder. The drilling tool should frequently be pulled up to make sure that the drilling is occuring easily.If difficulty occurs in drilling, the 12 inch (30cm) diameter casing 147 should be disconnected and left in the hole and the hammer 19 alone used. When drilling becomes easier again, the 12 inch (30cm) diameter casing 147 may be reconnected and the two sets of drilling tools used again.

When the 12 inch diameter (30cm) casing 147 touches the bed rock, then the drilling is completed. The method illustrated by Fig. 14 is particularly ideal because of the low costs involved and the fact that it is suitable for production of either big or small bores. The ODEX method now used in some countries is more expensive and only small drilling tools are available for use in such a method.

Figs. 15 and 16 illustrate methods of over-burden drilling using the rotary head in accordance with the invention. In the arrangements shown in Figs. 15 and 16, two sets of drilling tools comprising an outer casing 150 carrying a ring bit 151 and an inner drill rod 152 carrying a, for example, hammer 153 are engaged with the rotary head in the manner similar to that described for the arrangement shown in Fig. 14. The two sets of drilling tools are then used to drill to a complicated or difficult area of ground, flushing fluid being supplied to the drilling tools via the flushing inlet 11 and being supplied from the drilling tools via the flushing outlets 44 and 35.

When an easier or a steady area is reached, then the outer drilling tool or casing 150 may be disengaged and left in the hole and drilling continued with the inner tool only, the connection device and the flushing unit 2 having been removed as indicated in Fig. 16.

Fig. 17 illustrates a new method of grouting using a rotary head in accordance with the present invention. In this method, the connection device 1 and flushing aperture carrying unit are removed and a 7 inch (18cm) diameter casing 164 is clamped by the hydraulic clamp unit 3 to the rotary head. The adapter 61 or 62 is also removed and a one inch (2.54cm) diameter grouting pipe 161 is inserted through the rotary head and extends into the bore in which a cement anchor is required. Cement is then pumped into the grouting pipe 161 to the pipe outlet 162 thereof and the bore is filled to a depth of approximately 20 feet (600 cm) to form an adequate anchor 163.The grouting pressure should be carefully observed during the grouting process and if the pressure increases to 200 psi (1.38X106Nm2), the 7 inch (18cm) diameter casing 164 should be pulled up using a back clamp of the rotary head 5 while the casing 164 is being rotated by the rotary head. As soon as the grouting pressure begins decrease, pulling up of the 7 inch (18cm) casing 164 can be stopped. The grouting should be stopped after 5 to 10 bags of cement have been poured into the hole. Then the grouting pipe 161 and the 7 inch (18cm) diameter casing 164 should be removed one by one from the bore.

The quality of the anchor made by this method be particularly good. In other countries, the grouting technique level is lower than in this method because of the lack of a rotary head in accordance with the present invention. Thus, for example, in Italy, a big bore drill head can only perform the grouting operation but cannot extract the casing simultaneously as the rotary head thereof has only one connection device.

As will be appreciated, in the rotary head described above, the second connection device 61 or 62 is provided at the top of the rotary head and the flushing aperture 11 thereof is provided inside the connection device 61 or 62, the hydraulic clamp 3 being provided beneath the connection device 61 or 62 so as to avoid the possibility of a rod being overscrewed or unscrewed from a connection device during, for example, overburden drilling, to prevent a drilling rod or other tool from dropping into the bore. Further, a lower or bottom connection device 1 is located beneath the hydraulic clamp so that up to three sets of drilling tools can be used simultaneously. Also, the rotary head is provided with a hydraulic motor drive which has a twospeed gear box allowing a rotation speed of 200 rpm using a single hydraulic motor and upto 400 rpm when two hydraulic motors are connected in a series to enable full use to be made of the advantageous features of roller bits or diamond bits and therefore to increase efficiency.

Furthermore the rotary head can be used in normal flushing or circulation flushing drilling operations and there is no need to use specially made tools when changing the direction of flushing.

Also, the problems of drilling tools becoming detached and falling into a bore can be prevented or at least mitigated even with two or more drilling tools operating simultaneously.

Claims

1. A rotary head for a drilling machine, the rotary head comprising: means for engaging a plurality of drilling tools; means for rotating drilling tools engaged by the engaging means at a speed which is adjustable; and flushing means comprising a plurality of flushing inlets apertures for supplying flushing fluid to or from drilling tools engaged by the engaging means.

2. A rotary head for a drilling machine, the rotary head comprising upper, intermediate and lower engaging means spaced apart on the rotary head for each engaging one or more drilling tools, flushing means comprising three flushing apertures for supplying flushing fluid to or from drilling tools engaged by the engaging means, and means for rotating the drilling means engaged by the engaging means at a speed which is adjustable.

3. A rotary head according to Claim 1 or 2, wherein the or the upper engaging means comprise an adapter for connecting drilling tools to the rotary head.

4. A rotary head according to Claim 1 or 2, wherein the or the upper engaging means comprises first and second interchangeable adapters for connecting drilling tools to the rotary head.

5. A rotary head according to Claim 3 or 4, wherein the or each adapter is provided with an aperture for supplying flushing fluid to or from drilling tools engaged by the engaging means.

6. A rotary head according to Claim 3, 4 or 5, wherein the or the first adapter comprises a plurality of adapter sections, the adapter sections being of different cross-sectional areas so that the cross sectional area of the adapter decreases in a step-wise manner, each adapter section having a surface formed with a screw-thread for engaging a screw-threaded end of a drilling tool.

7. A rotary head according to Claim 6, wherein at least three adapter sections are provided and the screw-thead of at least two adjacent adapter sections extend in opposite directions.

8. A rotary head according to any one of claim 3 to 7, wherein the or the second adapter has a single screw-threaded adapter section.

9. A rotary head according to Claim 8, wherein the single screw-threaded adapter section has a four degree taper.

10. A rotary head according to any one of claims 3 to 9, wherein the or each adapter section is elongate and a flushing channel extends axially therethrough.

11. A rotary head according to any one of claims 3 to 10 wherein a flushing aperture is provided on the rotary head adjacent the adapter.

12. A rotary head according to Claim 1 or 2, wherein the or the lower engaging means comprises a connection device for engaging a drilling tool, the connection device being provided at an end of a rotary head which in use is lowermost.

13. A rotary head according to any one of claims 3 to 11, wherein the or the lower engaging means comprises a connection device provided at the other end of the rotary head, the connection device being arranged to engage a drill casing for surrounding a drill rod or casing engaged by the adapter.

14. A rotary head according to Claim 12 or 13, wherein the connection device comprises a screw-threaded end section of the rotary head.

15. A rotary head according to Claim 14, wherein the screw-threaded section tapers toward the free end thereof.

16. A rotary head according to Claim 15, wherein the screw-threaded end section has a four degree taper and is arranged to engage a casing having a diameter of approximately ten inches (25.4cm) or twelve inches (30cm).

17. A rotary head according to any one of claims 11 to 16, wherein a flushing outlet or inlet extends obliquely of the connection device.

18. A rotary head according to any preceding claim, wherein the or the intermediate engaging means comprises gripping means for gripping a drilling tool means by the engaging means.

19. A rotary head according to Claim 18, wherein the gripping means comprises a plurality of gripping jaws movable into and out of engagement with a drilling tool.

20. A rotary head according to Claim 19, a rotary head according to Claim 18, wherein the gripping jaws are provided with teeth and are hydraulically actuated.

21. A rotary head according to Claim 19 or 20, wherein the jaws are arranged to rotate with a drilling tool engaged thereby.

22. A rotary head according to any preceding claim, wherein the rotating means comprises a gear arrangement for transmitting rotation from a single motor or motors.

23. A rotary head according to Claim 22, wherein the gear arrangement comprises first and second gears rotatably mounted to a main shaft carrying the engaging means for rotating the main shaft, and third and fourth movable gears movable between a first position in which power is transmitted to the main shaft via the first and third gears and a second position in which power is transmitted via the second and fourth gears to the main shaft.

24. A rotary head substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

25. A method of reverse-circulation drilling using a rotary head according to Claim 2, which method comprises engaging a first drill casing carrying a ring bit with the lowermost engaging means of the rotary head, positioning a drill pipe or second drill casing carrying a ring bit within the first casing and engaging the drill pipe or second casing with the intermediate engaging means which comprise gripping means provided on the rotary head, blocking off the intermediate one of the three flushing apertures provided on the rotary head, actuating the rotating means to rotate the rotary head to cause the drill bits to drill downwardly and supplying flushing fluid through the lowermost flushing aperture of the rotary head whereby drilling debris is flushed outwardly during drilling through the uppermost flushing aperture of the rotary head.

26. A method of reverse-circulation drilling using a rotary head in accordance with Claim 2, which method comprises engaging a first drill casing with the lower engaging means of the rotary head, a free end of the casing carrying a drilling bit, positioning a second drill casing or pipe within the first drill casing and bringing the second drill casing into engagement with the upper engaging means blocking off one of the three flushing apertures provided on the rotary head, actuating the rotary head to rotate the rotary head to cause the drilling bits carried by the first and second casings to drill a bore and supplying flushing fluid through the intermediate flushing aperture of the rotary head, whereby drilling debris is flushed out from the upper flushing aperture.

27. A method of central circulation drilling using a rotary head in accordance with Claim 2, which method comprises engaging a first drill casing with the lower engaging means of the rotary head, positioning a drill rod within the casing, the drill rod carrying a drill bit, closing the intermediate flushing aperture of the rotary head, actuating the rotating means to cause the rotary head to rotate and supplying flushing fluid through the uppermost flushing aperture of the rotary head, whereby drilling debris is flushed out through the lowermost flushing aperture of the rotary head.

28. A method of air central circulation drilling using a rotary head according to Claim 2, which method comprises removing the lower engaging means of the rotary head, positioning a drill rod carrying a drill bit within a drill casing, engaging the drill rod with one adapter section of a three-stage adapter comprising the upper engaging means of the rotary head, gripping the drill casing with gripping means comprising the intermediate engaging means of the rotary heads, actuating the rotating means to rotate the rotary head to drill downwardly and supplying compressed air through the uppermost flushing aperture in the adapter, whereby drilling debris is forced outwardly through the intermediate flushing aperture of the rotary head.

29. A method of horizontal reverse circulation drilling using a rotary head in accordance with Claim 2, which method comprises connecting a respective drilling tool to each of three adapter sections of a three-stage adapter comprising the upper engaging means of the rotary head, flushing fluid through a lower and/or immediate flushing aperture of the rotary head so that drilling debris is flushed out via a flushing aperture provided in the adapter and actuating the rotating means to rotate the drilling tools.

30. A method according to Claim 28, wherein one of the drilling tools comprises a drilling casing surrounding the other two tools and, as the drilling proceeds, the casing is disconnected from the rotary head and left in the bore to protect the other drilling tools.

31. A method of drilling in rocky ground using a rotary head in accordance with Claim 2, which method comprises engaging a drill casing with the lower engaging means of the rotary head, fitting a drill rod within the casing and engaging the drill rod with a single section adapter comprising the upper engaging means of the rotary head, fitting a drilling hammer to the drill rod, supplying flushing fluid through a flushing aperture provided in the adapeter, raising the hammer, lowering the hammer to touch the ground in which a drilling bore is to be formed, actuating the rotating means to cause the rotary head to rotate to drill downwardly, whereby debris is forced outwardly through the lower flushing aperture and the intermedaite flushing aperture, reducing the speed of rotation of the rotary head when rocky ground is reached and increasing the volume and pressure of flushing fluid so as to remove rock debris from the bore.

32. A method of over-burden drilling using a rotary head in accordance with Claim 1, which method comprises engaging two sets of drilling tools with the engaging means and actuating the rotating means to rotate the rotary head to cause the drilling tools to drill until a steady area is reached, disengaging an outermost drilling tool so that the same remains in the drilled bore and actuating the rotating means to drill forwardly with the innermost drilling tool.

33. A method of forming a ground anchor in a bore using a rotary head in accordance with Claim 2, which method comprises removing upper and lower ones of the three engaging means, engaging a pipe casing with the intermediate engaging means, inserting the pipe casing and a grouting pipe into a bore to be grouted, pumping grouting cement into the grouting pipe to form an anchor, removing the grouting pipe and subsequently removing the casing from the hole.

34. A method of drilling using a rotary head in accordance with Claim 1, substantially as hereinbefore described with reference to any one of Figs. 10 to 17 of the accompanying drawings.

35. A rotary head for a drilling machine, the rotary head having an adapter for connecting a drilling tool to the rotary head, the adapter being arranged to supply flushing fluid to a drilling tool connected thereto and the adapter comprising a plurality of adapter sections, the adapter sections being of different cross-sectional area so that the cross-sectional area of the adapter decreases in a step-wise manner, each adapter section having a surface formed with a screwthread for engaging a screw-threaded end of a drilling tool.

36. A rotary head according to Claim 35, wherein at least three adapter sections are provided and the screwthread of at least two adjacent adapter sections extend in opposite directions.

37. Any novel feature or combination of features described herein.