EP0022865B1

EP0022865B1 - Hydraulically-driven downhole drill

Info

Publication number: EP0022865B1
Application number: EP19790900104
Authority: EP
Inventors: Yoshikazu Mikami
Original assignee: Furukawakogyo Coltd
Current assignee: Furukawakogyo Coltd
Priority date: 1978-12-15
Filing date: 1980-07-01
Publication date: 1984-08-01
Also published as: EP0022865A4; EP0022865A1

Abstract

A hydraulically driven downhole drill is provided with a drill connector (51) for simplifying both hydraulic circuits of a drill head (1) and a connecting rod (60) and adapting the hydraulic circuit arrangement of the drill head (1) with the other hydraulic circuit arrangement of the connecting rod (60). Use of this drill connector results in simplification of the circuit arrangement at the connecting portion between the drill head and connecting head. This downhole drill is further provided with an automatically-operated hydraulic pressure shut-off valve (65) at a connecting portion between the connecting rods (60) to prevent oil from leaking upon engagement and disengagement of the rods (60). The drill head (1) has a mechanism for reciprocating hydraulically a piston (8) controlled by a control valve (20) in the cylinder, and the piston (8) has a hydraulic circuit (50) for removing chips. The connecting rods (60) each have therein a high pressure hydraulic circuit (30) formed along the central axis, a low pressure hydraulic circuit (40) formed coaxially with the hydraulic circuit (30) around the outer periphery thereof, and pipes (61, 61a, 61b) including the hydraulic circuit (50) for removing chips. A pressure compensator can be mounted at the connecting portion of the drill head with the connecting rod and at the connecting portions of the connecting rods with each other.

Description

The invention relates to a down-the-hole hydraulic drill comprising a down-the-hole hammer drill having a cylinder in which a piston is slidably housed, the piston being reciprocated by means of pressurized oil controlled by a directional control valve housed in said cylinder, said piston having a central axial bore for pressurized air or hydraulic flushing fluid for discharging the cuttings; a drill rod connecting said hammer drill to a rotary drill head, said drill rod consisting of a plurality of segments in the form of pipes which define a high pressure oil passage along the central axis and a low 'pressure oil passage and a passage for said flushing fluid located radially outwardly and concentrically to each other around said high pressure oil passage; a rotary head disposed outside the borehole and being connected to the drill rod said rotary head comprising a shank rod having passages which communicate with respective swivels and with said high pressure oil passage, low pressure oil passage and passage for flushing fluid provided in the rod; and a driving means for rotating said shank rod, the drill rod and the hammer drill.
Generally, drills of the type utilizing pressurized air for a percussion mechanism of the piston are inferior in efficiency, and much in power loss and yet there has been a certain limitation in the power and the number of repetition of blows or percussive actions.
In view of this, percussion devices utilizing hydraulic pressure have been developed, however, down-the-hole drills of the conventional type are complicated in construction of the hydraulic passages and directional control valve means thus resulting in uncertain operation.
Also, hydraulic passages and the passage for introducing pressurized air or fluid for discharging sludge have been provided by inserting hoses or the like, consequently, connection of these passages have been very troublesome and yet not free from the leakage of oil.
Moreover, construction of the connection between the drill head and the connecting rod is complicated and there are also found such drawbacks as their pressure compensation device does not function effectively.
From JP-U-157501/76 there is already known a down-the-hole hydraulic drill comprising a cylinder, in which a piston is slidably housed, which is reciprocated by pressurized oil through a directional control valve means. Said piston has on its central axis a passage for pressurized fluid or hydraulic air for discharging sludge. Furthermore, the already known down-the-hole hydraulic drill comprises a rotary head, which is connected with the drill head via an interconnected drill rod. This known down-the-hole hydraulic drill shows the drawback that the piston is not directly operated by hydraulic oil, but that there is provided a spring for operating the piston, by means of said spring no sufficiently sure reciprocating movement of the piston is achieved. The passages for pressurized oil and return oil as well as for pressurized air are arranged in the directional control valve so that the construction of said valve is expensive and complicated. From JP-A-52801/77 there is known a drill connection to connect the drill rod with the drill head, by means of said drill connection the direction of the passages for the fluid flows can be changed in such a way that the passage for hydraulic air for discharging sludge is to be found on the central axis. This hydraulic drilling device comprises already a compensator for hydraulic pressure interposed between the last drill rod and the drill hammer.
The problem of the invention is to prevent the disadvantages of the down-the-hole hydraulic drill and to provide a down-the-hole hydraulic drill with a simplified construction and in which the piston is operated in a faster and safer way so that an improvement in drill efficiency can be achieved.
The problem underlying the invention is solved in that said cylinder of the hammer drill has a high pressure oil passage and low pressure oil passage, that said piston within the cylinder has a front pressure surface and a rear pressure surface each having different areas so that said cylinder is divided into a first hydraulic chamber and a second hydraulic chamber by said piston, that said high pressure oil passage in the cylinder is communicated with both said first hydraulic chamber and second hydraulic chamber, and said low pressure oil passage in the cylinder is communicated with said second hydraulic pressur chamber; that the directional control valve has a front end surface and rear end surface with different areas and is housed slidably in said second hydraulic chamber thus allowing change of action of the hydraulic oil under pressure on said pressure surfaces of the piston, that the hydraulic drill further comprises a drill connection interposed between the last of said rods and said hammer drill such that each of the passages in said rod can be communicated to each of the corresponding passages in said hammer drill, said drill connection comprising a passage for pressurized air or fluid for discharging sludge located and formed on the longitudinal central axis of the body portion thereof, a plurality of high pressure oil passages and low pressure oil passages located and formed radially and outwardly around said passage for pressurized air or hydraulic fluid and extending up to the one end portion of the connection and a recessed portion located and formed at said end portion of the connection, the bottom of which defines the opening of said passage for pressurized air or fluid, said high pressure oil passages and low pressure oil passages opening at the outer periphery of said body portion thereof of the connection, the other end of the drill connection being formed to have a reduced diameter portion, an intermediate diameter portion and an enlarged diameter portion from its tip end one after another and a high pressure oil passage formed on the central axis of said reduced diameter portion is bend radially and outwardly so as to be communicated with said high pressure oil passage in said body portion; and ports and slits communicated with said low pressure oil passage and said passage for pressurized air or hydraulic fluid in said body portion are formed at the outer periphery of said intermediate diameter portion.
This invention includes a preferred embodiment which comprises an automatic valve or valves which opens both said high pressure oil passage and low pressure oil passage only when another rod segment is connected to its connecting end.
Down-the-hole hydraulic drill of the present invention is simplified in designing the fluid passages and can be housed in a small space by providing both the directional control valve means and fluid passages for actuating reciprocal movement of the piston in the cylinder constituting the drilling head. Also the piston action can be performed very firmly.
The rod portion is composed of a plurality of concentrically disposed pipes wherein the high pressure oil passage is formed on the central axis and the low pressure oil passage is formed around the high pressure oil passage and the passage for pressurized air or fluid is positioned further around the low pressure oil passage.
Accordingly, operation of the pressurized oil is performed very reasonably within the limitation of allowable strength of the rod.
Also the provision of the automatic oil shutting valve or stop valve at the connecting end ensure complete prevention of oil leaking during the connecting or disconnecting operation of the rod and thereby the connection and disconnection can be done readily and rapidly, thus this invention contributes to improve economical use of both power and material.
Further due to the connection by interposing the drill connection which enables to leads the fluids under pressure from the rod to the drill head having differently positioned fluid passages from the former and to establish correct communication to each corresponding passages, both, the pressurized oil, and the air or hydraulic fluid for discharging the sludge can be done very smoothly.
Furthermore, pressure compensation device can be mounted adjacent to the drill head so that drilling operation in a deep well can be performed by maintaining required percussive force and with high efficiency.
Accompanying drawings shows preferred embodiments of the invention. Fig. 1 is a cross sectional elevation of a drilling head. Fig. 2 is a cross sectional elevation of a drill connection. Fig. 3 is a stepped vertical cross sectional view of the drill connection taken along line A-A of Fig. 2. Fig. 4 is an enlarged cross sectional elevation of the junction of a rod. Fig. 5 is a cross section elevation of a rotary head. Fig. 6 is a cross section plan view taken along line B-B of Fig. 5. Fig. 7 is a cross sectional elevational view of a pressure compensation device. Fig. 8 is a cross sectional view taken along line D-D of Fig. 7.

Preferred embodiments

A preferred embodiment of this invention will be explained by refering to the accompanying drawings.
In a hammer drill or drilling head 1 shown in Fig. 1, a cylinder 2 having circular cross section comprises an axially extending passing-through bore consisting of a reduced diameter portion 3. Main or intermediate diameter portion 4 and two enlarged diameter portions 5 and 6. At the rear part (upper part in the drawing) of said enlarged diameter portion 6, a plug 7 being provided therewith a valve seat is inserted therein.
A piston 8 consists of an intermediate diameter portion 9, a first enlarged portion 10, a second enlarged portion 11, a reduced diameter portion 12, each of which slidably fits with the reduced diameter portion 3, main or intermediate diameter portion 4 of the cylinder 2 and said plug 7, respectively, and a percussion head 13 at the forward end of the intermediate diameter portion 9.
An interconnecting portion 14 having a diameter slightly smaller than that of intermediate portions 10 and 11 is formed between the intermediate portions 10 and 11.
A hydraulic or pneumatic passage 50 for discharging sludge formed by drilling operation is bored on the central and longitudinal axis of said piston 8.
The piston 8 comprises an annular front pressure surface 15 and an annular rear pressure surface 16, on which surfaces a hydraulic oil under pressure acts.
The pressure surface 15 has a surface area defined by a stepped portion between the intermediate portion 9 and the first enlarged diameter portion 11, while said pressure surface 16 has a surface area defined by the second enlarged diameter portion 11 and the reduced diameter portion 12.
As the diameter of the intermediate diameter portion 9 is larger than that of the reduced diameter portion 12, the surface area of said rear pressure surface 16 is larger than that of the front pressure surface 15.
Said front pressure surface 15 and said intermediate diameter portion 9 of the piston 8 defines a first hydraulic pressure chamber 17 with the main or intermediate diameter portion 4 of the cylinder 2.
The rear pressure surface 16 and the reduced diameter portion 12 of the piston 8 define a second hydraulic pressure chamber 18 with both of the cylinder 2 and the plug 7.
A directional control valve 20 is provided slidably disposed within said second hydraulic pressure chamber 18 and is concentric with the piston 8 so as to annularly surround the reduced diameter portion 12 of the piston 8, whereby the second hydraulic pressure chamber is divided by the directional control valve 20 into a front chamber 18a and rear chamber 18b.
Said directional control valve 20 is slidably fitted around the enlarged diameter portions 5, 6 of the cylinder and the valve seat 7a of said plug 7, and rearward end 20b of which has a larger area than that of a forward end 20a.
Stroke of the directional control valve 20 is restricted at the forward end portion 20a, by abutment with a stepped portion 21 of said cylinder 2, while at its rear end portion by abutment with a stepped portion 7b of the plunger 7.
A stepped portion 22 projecting radially and inwardly toward the longitudinal axial center is formed at the middle part of said directional control valve 20, inside diameter of said stepped portion is slightly larger than the diameter of the reduced portion 12 of said piston 8.
Inside diameter of the forward portion 20c of said directional control valve 20 is made slightly larger than the diameter of the main diameter portion 4 of said cylinder 2.
A plurality of longitudinal small grooves 23 are formed between the rear end portion 20d of the directional control valve 20, whereby a suitable amount of hydraulic oil can be communicated from the front chamber 18a to the rear chamber 18b.
Sectional dimension of said grooves 23 can be decided depending upon the nature of the hydraulic oil and the characteristic of the percussion means.
Annular grooves 24 and 25 are formed, respectively, at the main diameter portion 4 and the enlarged diameter portion 5 of said cylinder 2 such that the grooves 24 and 25 communicate, respectively, with a high pressure oil passage 30 formed in said cylinder 2.
Also an annular groove 26 and an annular groove 27, each formed in the main diameter portion 4 and the enlarged diameter portion 5, respectively, communicate with a low pressure hydraulic oil passage 40 formed in said cylinder 2.
The annular groove 27 communicates said low pressure hydraulic oil passage 40 to the second hydraulic fluid chamber 18 through a passage 28 and an annular groove 29 both formed in said stepped portion 22, when the directional control valve 20 takes its advanced position.
The annular groove 24 is positioned at a location where there occurs no closing thereof by said piston 8 when piston 8 takes its position for percussion, and said first hydraulic chamber 17 usually communicates with a hydraulic oil pressure source ion normal operation.
The front chamber 18a and rear chamber 18b of said second hydraulic pressure chamber 18 communicate with each other by a passage 41. The annular groove 28 is formed adjacent to said annular groove 26 thereby these two grooves communicate with each other through the interconnecting portion 14 of the piston 8. 29a is a supplementary passage for effecting smooth sliding of said directional control valve 20.
The piston 8 and the directional control valve 20 in Fig. 1 shows a state where said piston 8 is immediately before starting its backward stroke after it has finished its advancing stroke, while the directional control valve 20 is kept to abut against the stepped portion 21 caused by a pressure difference due to difference of area between the forward end 20a and rear end 20b.
The first hydraulic pressure chamber 17 communicates to the high pressure oil passage 30, thereby the piston 8 starts its backward stroke by an oil under pressure acting upon said front pressure surface 15 of the piston 8.
As the piston 8 travels backward, pres-, surized oil within the second hydraulic pressure chamber 18 is drained through said passage 28 into the low pressure oil passage 40.
Upon abutment of the rear pressure surface 16 on the stepped portion 22 of said directional control valve 20, the control valve 20 retracts.
If communication between the passage 28 of the directional control valve 20 and the low, pressure oil passage 40 is interrupted due to retraction of the control valve 20, interconnecting portion 14 of said piston 8 still allows communication between the annular groove 26 and 28 such that the pressurized oil in the second hydraulic pressure chamber is discharged through said passage 41 into the low pressure oil passage 40.
In this way, all the oil in the forward chamber 18a flows into said rear chamber 18b through the longitudinal small grooves 23, and at this time, there arises pressure difference between the forward chamber 18a and the rear chamber 18b due to an orifice restriction effect caused by said small groove 23.
The directional control valve 20, however, firmly retracts as the pressure in the rear chamber 18b descreases.
Due to the retraction of the directional control valve 20, the annular groove 25 is uncovered so as to allow the pressurized oil to flow into the forward chamber 18a, thereby the control valve 20 still retracts even after it is released from engagement with said piston 8 until it abuts against the stepped face 7b of said plug 7.
The piston 8 is also acted on by a pressurized oil on its rear pressure surface 16 having larger pressure surface area than that of the front pressure surface 15, accordingly, the speed of the piston 8 gradually decreases until it finally stops to complete its backward stroke.
As the surface area of said rear pressure surface 16 is larger than that of the front pressure surface 15, the piston 8 changes it movement into advancing stroke due to further introduction of pressurized oil into forward chamber 18a.
Due to advancing movement of the piston 8, communication between the annular grooves 26 and 28 is interrupted, then the forward chamber 18a communicates with the annular groove 28 when the rear pressure surface 16 passes over the annular groove 28, thereby the pressurized oil flows into said rear chamber 18b through the passage 41.
The directional control valve 20 advances due to pressure difference caused by the difference in surface area between the forward end face 20a' and the rear end face 20b thereof, then it stops when the forward end face 20a abuts against said stepped portion 21 thereby the annular groove 25 is closed to prevent the pressurized oil from flowing into the forward chamber 18a.
A front head 32 into the tip end of which a chuck 31 is inserted, is threadedly attached to the front end (lower side of the drawing) of the cylinder 2.
A drill bit 33 is slidably held in the front head 32 and is also fitted with the chuck 31 by spline engagement.
A rear end of the drill rod confronts with the percussion hammer portion 13 of said portion 8.
A stepped face 34 is formed at the forward part of the front head 32 defined by an undercut recess 35.
A resilient member 36 is inserted into a space between the stepped face 34 and the rear end of said chuck 31 and a set of beveled spring 37 is resiliently interposed within said resilient member 36 such that a flange 38 of the drill bit 33 abuts thereon so as to restrict the stroke thereof as well as to absorb and cushion the shock imparted to the percussion head caused by the percussive action of said drill bit 33.
At the rear part of the cylinder 2 (upper side of the drawing), there is constituted a portion for connecting a drill connection 51 which will be explained hereinafter.
Figs. 2 and 3 show the drill connection 51 in which a passage 50 for pressurized air or fluid for discharging drilled sludge is bored along a body portion 52 having an outside diameter about the same as inside diameter of said cylinder 2.
A plurality of high pressure oil passages 30 and low pressure oil passages 40 are formed radially and outwardly around and on the same concentric circle with respect to said passage for pressurized air or fluid.
In the drawings, three passages each are shown, but the number of these passages can be suitably selected by taking the amount and .pressure of the oil into consideration.
At the axial forward end portion (lower side of the drawings) of the body portion 52, there are formed a reduced diameter portion 54 formed with a recessed portion 53 having an inside diameter the same as that of the plug 7 inserted in the cylinder 2 of said drilling head 1 and an intermediate diameter portion 55 between the body portion and the reduced diameter portion.
The reduced diameter portion 54 has an outside diameter so as to be inserted into the rear end of the cylinder 2 of the drilling head 1 and is threadably fixed to said cylinder 2 by the screw threads formed on said intermediate diameter portion 55.
Fluid passages in the body portion 52 extend to the reduced diameter portion 54 and the air or fluid passage 50 has its opening at the bottom of the recessed portion 53, while the high pressure oil passage 30 and the low pressure oil passage 40 have openings at the outer periphery of the reduced diameter portion 54 and are communicated with respective oil passages formed in the cylinder 2 of said drilling head 1.
Rear end portion (upper part in the drawing) of the body member has, from its upper tip end to its lower part, a reduced diameter portion 56, an intermediate diameter portion 57 and an enlarged diameter portion 58, respectively, and constitutes a portion for connection with a rod 60 which will be explained later.
A high pressure oil passage 30 is bored along the longitudinal axis of said reduced diameter portion. Said oil passage 30 is radially bent such that it is communicated with the high pressure oil passages 30 formed in the body portion 52.
On the surface of the intermediate diameter portion, inlet ports 59 and a slit are formed to permit fluid communication with said low pressure oil passage and the passage 50 for pressurized air or fluid, respectively.
Accordingly, the high pressure oil passage 30, low pressure oil passage 40 and the passage 50 for pressurized air or fluid of the drill connection 51 communicates, respectively with each of such passages formed in the drilling head 1, when said drill connection 51 is connected with said drilling head 1.
Fig. 4 shows the construction of a connecting section of the connecting rod 60 in an enlarged scale.
The connecting rod 60 consists of a rod 60a and a rod 60b both having tubular configuration and almost the equal diameter and are jointed together with each other.
In the drawing, the connecting rod 60 comprises an outer pipe 61, a first inner pipe 61 a and a second inner pipe 61 b, the latter being concentrically positioned within said outer pipe 61.
An annular cavity defined between the outer pipe 61 and said first inner pipe 61 a is used as is passage for the pressurized air or fluid for discharging sludge or cuttings.
Annular cavity defined between the first inner pipe 61 a and the second inner pipe 61 b and a hollow bore drilled within said second inner pipe 61 b, respectively, constitute a low pressure oil passage 40 and a high pressure oil passage 30.
The connecting rod 60 of such construction is assembled with respect to its outer pipe 61 by jointing said rod 60a and 60b by tightning mating taper screws 62, while upper and lower half of the first inner pipe 61 a and those of the second inner pipe 61b, respectively, are connected by means of faucet joint at 63a and 63b. Numeral 64 denotes an O-ring.
At the joints, particularly, at the joints of the high pressure oil passage 30 and the low pressure oil passage 40, there is provided a set of valve means 65 which automatically opens upon assembly of said connecting rod.
The valve means shown in the drawing is of mechanical type but any other means such as electrical one or mechanical type of different construct can be used where occasion demands.
The valve means shown in the drawing are attached at the joint ends of the 60a and 60b, namely, at each butt joint ends of the first inner pipe 61 a and the second inner pipe 61 b such that two mating pieces oppose each other.
At the inner axial end of the first inner pipe 61 a of the rod 60a, an annular valve seat 66a is threadedly attached along the inner periphery of the inner pipe. Similarly, an annular valve seat 66b of the same configuration is threadedly attached to the inner axial end of the first inner pipe 61 b at the side of the rod 60b.
These valve seats 66a and 66b project radially from the inner periphery of said first inner pipes 61 a and 61 b toward the center to constitute a tapered surface.
Stoppers 67a and 67b each faces with the valve seats 66a and 66b are fixed being fitted with the outer periphery of the second inner pipes 61 b in such a manner that said stoppers 67a and 67b do not prevent opening of the low pressure oil passage 40.
In the drawing, 68a and 68b denote lock rings for retaining the stoppers 67a and 67b.
Annular valve bodies 65a and 65b are slidably fitted around the outer periphery of the second inner pipes 61b, 61 b such that their outer peripheral faces project radially and outwardly to constitute a tapered face opposing said valve seats 66a and 66b.
In the drawing, 69a and 69b are seal packings attached to the valve bodies 65 and 65b, respectively.
Springs 70a and 70b are resiliently interposed between the stoppers 67a, 67b and valve bodies 65a and 65b such that said valve bodies are advanced so as to be contacted each other.
The valve bodies 65 and 65b, when said connecting rod 60 is not jointed together, are tightly contacted with the valve seats 66 and 66b, respectively, to block the low pressure oil passage 40. When the connecting rod 60 is joined as shown in the drawing, valve bodies 65a and 65b are pushed one another such that their opposing end portion move away from the mating contact with valve seat 66a and 66b to allow communication between the two low pressure oil passages 40.
At the axial end and along the inner periphery of the second inner pipe 61 b of the rod 60a, an annular valve seat 71 a is threadedly attached, and similarly, a valve seat 71 b of the same configuration is attached at the inner periphery of the second inner pipe 61 b of the rod 60b.
These valve seats 71 a and 71 b project from the inner periphery of said second inner pipes 61b, 61 b toward the center to constitute a tapered annular face.
At each interior side with respect to the valve seats 71 a and 71 b, a pair of stoppers 73a and 73b each having axially extending integral sleeve portion 72a and 72b, within each of which a valve body 74a and 74b each consisting of a shaft and a bevelled head is received being detachable in the axial direction.
A tip end portion of each of said valve body 74a and 74b is positioned at such a location that it slidably advances and engages with each of said valve seat 71 a and 71 b.
Said stoppers 73a and 73b are fixed and extend diametrically within the second inner pipes 61 b, 61 b but it is constructed so as not to prevent fluid communication of the high pressure oil passage 30.
In the drawing, 75a and 75b denote seal packings and 76a and 76b denote lock rings for retaining said stoppers 73a and 73b, respectively.
A pair of springs 77a and 77b are resiliently interposed between the rear face of each head of said valve body 74a and 74b and the stoppers 73a and 73b such that the valve bodies are urged advanced and opposedly contacted with each other.
When the connecting rod 60 has not yet been jointed into a single piece, the valve bodies 74a and 74b engage with said valve seats 71 a and 71 b thereby to close the high pressure oil passage 30.
While, at a location where the connecting rod 60 is jointed as shown in the drawing, the valve bodies 74a and 74b push one another to move tip end of each valve body away from the valve seats 71 a and 71 b to allow communication of the high pressure oil passage 30.
In this manner, the connecting rod 60 having been equipped with the automatic valve means 65 can be readily coupled or disassembled.
At the time of coupling, the valve means 65 automatically opens to pass flow of the actuating oil, whereas it automatically closes to shut down flowing of the actuating oil.
At one tip end of at least one of the rod of the connecting rod 60, a joint portion is formed so as to be connected with the drill connection 51.
As shown in Fig. 2, this joint portion is constructed such that said inner pipes 61 b and 61 a threadably engages with the reduced diameter portion 56 and the intermediate diameter portion 57, respectively, both formed on the rear (upper) end of the drill connection 51, and the outer pipe 61 is also threadedly fitted to the enlarged diameter portion 58.
Figs. 5 and 6 show the construction of a rotary head 80 which consists of a rotary actuating means 81 and a shank rod 82 rotatably mounted on said rotary actuating means 81.
The rotary actuating means 81 consists of a driving means 84 fixed on a base 83 and a driven shaft 86 rotably journalled by a bearing 85 mounted on said base 83.
The driven shaft 86 can be rotated by rotating said driving means 84 by a power supplied by any suitable power source (not shown) as a drive gear 88 is meshed with driven gear 89 each of which is fixedly attached to driving shaft 87 of the driving means and said driven shaft 86, respectively.
The driven shaft 86 is a hollow shaft body, to the inner periphery of which the rear end of said shank rod 82 is fitted and engaged by a spline, thereby the shank rod 82 can be rotated about its longitudinal axis and also can be moved at a certain distance in axial direction.
At the front (lower side of the drawing) portion there formed a reduced diameter portion 90, an intermediate diameter portion 91 and an enlarged diameter portion 92 each of which threadedly engages with the second inner pipe 61 b, the first inner pipe 61 a and outer pipe 61, respectively, of the rod 60.
A high pressure oil passage 30 is formed within and along the central axis of the shank rod 82 and a plurality of low pressure oil passages 40 and a passage 50 for pressurized air or fluid are formed at radially and outwardly and coaxially spaced positions from said centrally located high pressure oil passage 30.
The high pressure oil passage 30 has its end opening at the end face of the reduced diameter portion 90, while each of the low pressure oil passage 40 and pressurized air or fluid passage 50 has openings at the end face of the intermediate diameter portion 91 and the enlarged diameter portion 92, respectively.
A swivel 96 provided with inlet port 93 for high pressure oil, inlet port 94 for low pressure oil and inlet port 95 for pressurized fluid is fitted around the outer periphery of the shank rod 82, thereby allow communication of each fluid under pressure to respective fluid passage.
Accordingly, when the shank rod 82 is connected to the rod 60, each of said high pressure oil passage 30, low pressure oil passage 40 and pressurized air or fluid passage 50 communicate with respective passage formed in the rod 60.
The base 83 of the rotary head 80 is carried by a guide shell, not shown, in such a manner as capable of moving forward and backward and also is constructed to be imparted with suitable thrust force by a feeding device, not shown.
Figs. 7 and 8 show a pressure compensation device 100.
This pressure compensation device 100 comprises a coaxially disposed core tube 101 at both axial ends of which are fitted with auxilary joints 102 and 103.
These auxiliary joints 102 and 103 are both annular or tubular shape which communicate to the core tube 101.
Inside bore of the core tube 101 constitutes a high pressure oil passage 30 which further extends through the auxiliary joints 102 and 103.
One end of each auxiliary joint 102 and 103 fitted with the core tube has a plug fitting end face 104 and 105 and each of the other end is formed to have flange 106 and 107.
On the inner periphery of the auxiliary tube 102 is formed a rib 108 having a height equal to the wall thickness of the core tube 101 both axial end of which are shaped to constitute thrust faces 109 and 110 and said core tube 101 is supported by said thrust face 109.
Inside of the auxiliary joint 103 is formed to have a recessed bore 111 with a large inside diameter to receive said core tube 101 and a bore 112 with a small inside diameter defined by a thrust face 111 by which said core tube is supported.
At the axial end opposite to the plug-fitting end face 105, a protruding sleeve 113 is integrally formed for faucet joint member, while the flange 107 is partly undercut to attach there a gas supply pipe 114.
Within said flange 107 a gas vent 116 is formed, which opens at an annular groove 115 formed on the periphery of said auxiliary joint 103.
A plurality of orifices 117 are formed on the periphery of the core tube 101.
Diameter and number of the orifices can be suitably selected as desired.
The core tube 101 is connected through said auxiliary joints 102 and 103 to joints 118 and 119, respectively.
As shown in the drawing, joint 118 is inserted into said auxiliary joint 102 up to the thrust face 110 thereof so as to be supported by said auxiliary joint 102.
Said joint 119 is fitted about the sleeve 113.
The joint 118 threadedly engages with the drilling head 1 at the forward end of its flange 120.
Rear part of said joint 118 is formed to become stepwisely smaller in diameter defined by stepped faces 121, 122 and 123.
Within the joint 118, there are formed a high pressure oil passage 30, a low pressure oil passage 40 and a passage 50 for pressurized air or fluid. The passage 50 for pressurized air or fluid opens at the periphery of the joint 118 between the stepped faces 122 and 123.
The low pressure oil passage 40 opens at the periphery between the end face of the flange 120 and the auxiliary joint 102.
The joint 119 is formed at one end of its flange 124 to become stepwisely smaller in diameter defined by stepped faces 125, 126 and 127, while the other end of which is formed to become stepwisely smaller in diameter defined by stepped faces 128, 129, 130 and 131 so as to be used for connection with the rod 60.
Within the joint 119 also formed a high pressure oil passage 30, low pressure oil passage 40 and a passage 50 for pressurized air or fluid.
A tube proper 133 within which a bladder 132 is fixed is secured by screw thread to the auxiJiary joints 102 and 103.
The core tube 101 is connected to both the auxiliary joints 102 and 103.
Diaphragm fabricated of flexible synthetic resinous sheet or metallic foil can be used for said bladder 132.
By virtue of the bladder 132, fluid chambers 134 are formed between the core tube 101 and the bladder 132, similarly, gas chambers 135 are formed adjacent to said fluid chamber 134 between the bladder 132 and the tube proper 133.
The fluid chamber 134 communicates to the high pressure oil passage 30 within the core tube 101 through said orifices 117.
Rear part of the tube proper 133 is formed to have a thick wall portion within which a gas vent 136 is formed which communicates with the gas vent 116 and further to said gas chamber 135.
And therefore, the gas chamber 135 is rendered in communication with the gas supply valve 114 when the tube proper 133 is assembled with the auxiliary joints 102 and 103.
Said gas supply valve 114 is exposed to the outside when the auxiliary joint 103 is removed from the joint 119 thereby permitting adjustment of the supplied gas.
An intermediate tube body 137 is faucet jointed to the stepped face 123 and peripheral surface between the stepped face and the end face of the joint 118 as well as to the stepped face 127 and the peripheral surface between the stepped face and the end face of the joint 119.
Between the inner periphery of the intermediate tube body 137 and a series of outer periphery including those of the joints 118 and 119 and auxiliary joints 102, 103 and the tube proper 133 interposed between said two joints, a low oil passage 40 is extendedly defined, which leads to those formed in the joints 118 and 119.
Around the joints 118 and 119, outer tube bodies 138 having outside diameter equal to the outside diameter of the flange portion 120 and 124 are threadedly fitted. Between the outer periphery of the intermediate tube body 137 and the inner periphery of the outer tube body 138, a passage 50 for pressurized air or fluid for discharging formed sludges are extendedly defined and communicate with those passages formed in the jionts 118 and 119.
Accordingly, if the fluid pressure in the high pressure oil passage 30 drops during the advancing stroke of the piston 8 of the drilling head, fluid chamber 134 is acted by a pressure imparted by a gas filled in the gas chamber 135, thereby the fluid pressure in the high pressure oil passage 30 can be compensated through the orifices 117.
Excessive energy generated due to retraction of the piston 8 of the drilling head or switching of the valve can be stored within the pressurized fluid chamber 134 through the orifices 117.
Gas pressure within the gas chamber 135 changed (lowered by repeated operation can be adjusted by the gas supply valve 114.
In this manner, under a condition where the pressure compensation device 100 is connected to both the rod 60 and the drilling head 1, the high pressure oil passage 30, the low pressure oil passage 40 and the passage 50 for pressurized air or fluid in the pressure compensation device 100 extend and communicate with those provided in the rod 60 and the drilling head 1.
In this embodiment explained above, an example where connction with drill rod is performed by the joint 118, however, this kind of joint means can be interposed between the drill connection 51 and 60 as well as between the two segments of the rod.

Claims

1. A down-the-hole hydraulic drill comprising: a down-the-hole hammer drill (1) having a cylinder (2) in which a piston (8) is slidably housed, the piston being reciprocated by means of pressurized oil controlled by a directional control valve (20) housed in said cylinder, said piston having a central axial bore (50) for pressurized air or hydraulic flushing fluid for discharging the cuttings; a drill rod (60) connecting said hammer drill (1) to a rotary drill head (80), said drill rod (60) consisting of a plurality of segments in the form of pipes which define a high pressure oil passage (30) along the central axis and a low pressure oil passage (40) and a passage (50) for said flushing fluid located radially outwardly and concentrically to each other around said high pressure oil passage (30); a rotary head (80) disposed outside the borehole and being connected to the drill rod (60) said rotary head comprising a shank rod (82) having passages (30, 40, 50) which communicate with respective swivels (93, 94, 95) and with said high pressure oil passage (30), low pressure oil passage (40) and passage (50) for flushing fluid provided in the rod (60); and a driving means (81) for rotating said shank rod (82), the drill rod (60) and the hammer drill (1), characterized in that said cylinder (2) of the hammer drill (1) has a high pressure oil passage (30) and low pressure oil passage (40), that said piston (8) within the cylinder (2) has a front pressure surface (15) and a rear pressure surface (16) each having different areas so that said cylinder (2) is divided into a first hydraulic chamber (17) and a second hydraulic chamber (18) by said piston, that said high pressure oil passage (30) in the cylinder (2) is communicated with both said first hydraulic chamber (17) and second hydraulic chamber (18), and said low pressure oil passage (40) in the cylinder (2) is communicated with said second hydraulic pressure chamber (18); that the directional control valve (20) has a front end surface (20a) and rear end surface (20b) with different areas and is housed slidably in said second hydraulic chamber (18) thus allowing change of action of the hydraulic oil under pressure on said pressure surfaces (15; 16) of the piston (8), that the hydraulic drill further comprises a drill connection (51) interposed between the last of said rods (60) and said hammer drill such that each of the passages in said rod (60) can be communicated to each of the corresponding passages in said hammer drill, said drill connection (51) comprising a passage (50) for pressurized air or fluid for discharging sludge located and formed on the longitudinal central axis of the body portion thereof, a plurality of high pressure oil passages (30) and low pressure oil passages (40) located and formed radially and outwardly around said passge (50) for pressurized air or hydrulic fluid and extending up to the one end portion of the connection (51) and a recessed portion located and formed at said end portion of the connection (51), the bottom of which defines the opening of said passage (50) for pressurized air or fluid, said high pressure oil passages (30) and low pressure oil passages (40) opening at the outer periphery of said body portion thereof of the connection (51), the other end of the drill connection (51) being formed to have a reduced diameter portion, an intermediate diameter portion and an enlarged diameter portion from its tip end one after another and a high pressure oil passage formed on the central axis of said reduced diameter portion is bent radially and outwardly so as to be communicated with said high pressure oil passage (30) in said body portion; and ports and slits communicated with said low pressure oil passage (40) and said passage (50) for pressurized air or hydraulic fluid in said body portion are formed at the outer periphery of said intermediate diameter portion.

2. A drill according to claim 1, characterized in that the segments of the drill rod (60) are provided with automatic stop valves (65) at the junction of each axial end face thereof so that both the high pressure oil passage (30) and the low pressure oil passage (40) can be opened when the mating segment of the rod (60) is connected.

3. A drill according to claims 1 or 2, characterized in that the drill further comprises a pressure compensating device (100) interposed between said hammer drill (1) and said rod (60) or between the segments of said rod.