1. Technical Field
[0001] This invention relates to a hydraulically driven down-the-hole drill, and more particularly
to a kind of drill wherein construction of the hydraulic passages in a drill head
and a connecting rod is simplified so as to facilitate both connection and disengagement
of said passages and said rod and at the same time to prevent leakage of pressurized
oil as well as to enable easy mounting of a pressure compensation device.
2. Background Art
[0002] 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.
[0003] 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.
[0004] 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.
[0005] Moreover, construction of the connection between the drill head and the connecting
rod are complicate and there also found such drawbacks'as their pressure compensation
device could not function efficiently.
3. Disclosure of the Invention
[0006] The present invention aims to eliminate above-mentioned drawbacks. Accordingly, an
object of the present invention is to provide a hydraulic down-the-hole drill comprising
a drill head of compact and simplified construction and yet firmly actuate its reciprocating
piston.
[0007] Another object of the present invention is to arrange within the rod both the hydraulic
passages and the passage for air or fluid for discharging sludge in a steady and efficient
manner thereby to simplify the construction of the passages and to improve economy
in consumption of power and material.
[0008] Further object of the present invention is to simplify the passage arrangement at
the junction of the drill head and the rod.
[0009] A still further object of the present invention is to facilitate ready and rapid
connection and disconnection of the connecting rod segments.
[0010] A yet further object of the present invention is to prevent any oil leakage at the
time of connection and disconnection of the rod.
[0011] And further object of the present invention is to provide a down-the-hole hydraulic
drill comprising a built-in pressure compensation device having superior response.
[0012] And a still further object of this invention is to remarkably improve drilling efficiency
by using both a drill head of high percussive force and a rod capable of ready connection
and disconnection.
[0013] In the present application as shown by the preferred embodiments and depicted in
the drawings, the first invention is directed to a down-the-hole hydraulic drill of
the type having a drill rod in which a piston slidably housed in a cylinder is reciprocated
by a pressurized oil through a directional control valve means housed in said cylinder,
and being capable of letting pressurized air or hydraulic fluid for discharging sludges
to flow through the central axial bore of said piston, and further which a rotary
head, being interposed by a rod, is connected to, so as to be rotatable about the
central axis:
characterized in that said rod consists of pipes, which define a high pressure oil
passage formed on said central axis, a low pressure oil passage and a passage for
pressurized air or hydraulic fluid for discharging sludge located and formed radially
outwardly and concentrically one after another around said high pressure oil passage;
and that the hydraulic drill further comprises a drill connection having fluid passages
arranged therein to change the location of the flows of the fluids so as to be interposed
to connect said rod and said drill rod such that each of the passages in said rod
can be communicated to each of the corresponding passages in said drill rod.
[0014] Further, the second invention of this application is directed to a down-the-hole
hydraulic drill of the type having a drill rod in which a piston slidably housed in
a cylinder is reciprocated by a pressurized oil through a directional control valve
means housed in said cylinder, and being capable of letting pressurized air or hydraulic
fluid for discharging sludge to flow through the central axial bore of said piston,
'and further which a rotary head, being interposed by a rod, in connected to, so as
to be rotable about the central axis;
characterized in that said rod consists of pipes, which defines a high pressure oil
passage formed on said central axis, a low pressure oil passage and a passage for
pressurized air or hydraulic fluid for discharging sludge formed radially outwardly
and concentrically one after another around said high pressure oil passage; and
that the hydraulic drill further comprises a pressure compensation device interposed
between said drilling head and said rod or between the conjunction of said rod.
[0015] 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.
[0016] 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.
[0017] 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 are formed around the high pressure oil passage and the passage for pressurized
air or fluid is positioned further around the low pressure oil passage.
[0018] Accordingly, operation of the pressurized oil is performed very reasonably within
the limitaion of allowable strength of the rod.
[0019] 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.
[0020] 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.
[0021] Furthermore, pressure compensation device can be mounted adjacent to the drill head
so that drillin operation in a deep well can be performed by maintaining required
percussive force and with high efficiency.
4. Brief Description of the Drawing
[0022] Accompanying drawings shows prefferred 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.
5. Preferred Embodiments
[0023] A preferred embodiment of this invention will be explained by refering to the accompanying
drawings.
[0024] In a 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 diamenter 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] Stroke of the directional control valve 20 is restricted at the forward_end portion
20a, by abuttment with a stepped portion 2i of said cylinder 2, while at its rear
end portion by abuttment with a stepped portion 7b of the plunger 7.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] Sectional dimension of said grooves 23 can be decided depending upon the nature of
the hydraulic oil and the characteristic of the percussion means.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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 in normal operation.
[0044] 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 29.
[0045] The piston 8 and the directional control valve 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.
[0046] 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.
[0047] As the piston 8 travels backward, pressurized oil within the second hydraulic pressure
chamber 18 is drained through said passage 28 into the low pressure oil passage 40.
[0048] Upon abutment of the rear pressure surface 16 on the stepped portion 22 of said directional
control valve 20, the control valve 20 retracts.
[0049] 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
[0050] 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.
[0051] The directional control-valve 20, however, firmly retracts as the pressure in the
rear chamber 18b decreases.
[0052] Due to the retraction of the directional control valve 20, the annular grooves 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.
[0053] 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.
[0054] As the surface area of said rear pressure surface 16 is larger than that of the front
pressure surface 15, the piston 8 changes its movement into advancing stroke due to
further introduction of pressurized oil into forward chamber 18a.
[0055] 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.
[0056] 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 againstsaid stepped
portion, 21 thereby the annular groove 25 is closed to prevent the pressurized oil
from flowing into the forward chamber 18a.
[0057] 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.
[0058] A drill bit 33 is slidably held in the front head 32 and is also fitted with the
chuck 31 by spline engagement.
[0059] A rear end of the drill rod confronts with the percussion hammer portion 13 of said
piston 8.
[0060] A stepped face 34 is formed at the forward part of the front head 32 defined by an
undercut recess 35.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] A high pressure oil passage 30 is bored along the long-. itudinal 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.
[0071] 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.
[0072] 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.
[0073] Fig. 4 shows the construction of a connecting section of the connecting rod 60 in
an enlarged scale.
[0074] 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.
[0075] In the drawing, the connecting rod 60 is role of partition being in layers within
an outer pipe 61 into seperate layers such that a first inner pipe 61a and a second
inner pipe 61b are concentrically positioned within said outer pipe 61.
[0076] An annular cavity defined between the outer pipe 61 and said first inner pipe 61a
is used as is passage for the pressurized air or fluid for discharging sludge or cuttings.
[0077] Annular cavity defined between the first inner pipe 61a and the second inner pipe
61b and a hollow bore drilled within said second inner pipe 61b, respectively, constitute
a low pressure oil passage 40 and a high pressure oil passage 30.
[0078] 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 61a and those of the second inner pipe
61b, respectively, are connected by means of faucet joint at 63a and 63b. Numeral
64 denotes an 0-ring.
[0079] 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.
[0080] 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.
[0081] 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 61a and the second inner
pipe 61b such that two mating pieces oppose each other.
[0082] At the inner axial end of the first inner pipe 61a 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 61b at the side of the rod 60b.
[0083] These valve seats 66a and 66b.project radially from the inner periphery of said first
inner pipes 61a and 61b toward the center to constitute a tapered surface.
[0084] 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 61b in such a manner that
said stoppers 67a and 67b do not prevent opening of the low pressure oil passage 40.
[0085] In the drawing, 68a and 68b denote lock rings for retaining the stoppers 67a and
67b.
[0086] Annular valve bodies 65a and 65b are slidably fitted around the outer periphery of
the second inner pipes 61
b, 61b such that their outer peripheral faces project radially and outwardly to constitute
a tapered face opposing said valve seats 66a and 66b.
[0087] In the drawing, 69a and 69b are seal packings attached to the valve bodies 65 and
65b, respectively.
[0088] 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.
[0089] 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.
[0090] At the axial end and along the inner periphery of the second inner pipe 61b of the
rod 60a, an annular valve seat 71a is threadedly attached, and similarly, a valve
seat 71b of the same configuration is attached at the inner periphery of the second
inner pipe 61b of the rod 60b.
[0091] These valve seats 71a and 71b project from the inner periphery of said second inner
pipes 61b, 61b toward the center to constitute a tapered annular face.
[0092] At each interior side with respect to the valve seats 71a and 71b, 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.
[0093] 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 71a and
71b.
[0094] Said stoppers 73a and 73b are fixed and extend diametrically within the second inner
pipes 61b, 61b but it is constructed so as not to prevent fluid communication of the
high pressure oil passage 30.
[0095] In the drawing, 75a and 75b denote seal packings and 76a and 76b denote lock rings
for retaining said stoppers 73a and 73b, respectively.
[0096] 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.
[0097] 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 71a and 71b .thereby to close the
high pressure oil passage 30.
[0098] 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 71a and 71b to allow communication of the high pressure oil passage
30.
[0099] In this manner, the connecting rod 60 having been equipped with the automatic valve
means 65 can be readily coupled or disassembled.
[0100] 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.
[0101] 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.
[0102] As shown in Fig. 2, this joint portion is constructed such that said inner pipes
61b and 61a 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.
[0103] Figs. 5 and 6 show the construction of a roatary head 80 which consists of a rotary
actuating means 81 and a shank rod-82 rotatably mounted on said rotary actuating means
81.
[0104] 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.
[0105] 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 deiven
gear 89 each of which is fixedly attached to driving shaft 87 of the driving means
and said deiven shaft 86, respectively.
[0106] The deiven 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.
[0107] 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 61b, the first inner pipe
61a and outer pipe 61, respectively, of the rod 60.
[0108] 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.
[0109] 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.
[0110] 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.
[0111] Accordingly, when the shank rod 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.
[0112] 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.
[0113] Figs. 7 and 8 show a pressure compensation means 100.
[0114] This pressure compensation device 100 comprises a coaxially disposed core tube 101
at both axial ends of which are fitted with auxiliary joints 102 and 103.
[0115] These auxiliary joints 102 and 103 are both annular or tubular shape which communicate
to the core tube 101.
[0116] Inside bore of the core tube 101 constitutes a high pressure oil passage 30 which
further extends through the auxiliary joints 102 and 103.
[0117] 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.
[0118] 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.
[0119] 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.
[0120] 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.
[0121] 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.
[0122] A plurality of orifices 117 are formed on the periphery of the core tube 101.
[0123] Diameter and number of the orifices can be suitably selected as desired.
[0124] The core tube 101 is connected through said auxiliary tubes 102 and 103 to joints
118 and 119, respectively.
[0125] 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.
[0126] Said joint 119 is fitted about the sleeve 113.
[0127] The joint 118 threadedly engages with the drilling head 1 at the forward end of its
flange 120.
[0128] Rear part of said joint 118 is formed to become stepwisely smaller in diameter defined
by stepped faces 121, 122 and 123.
[0129] 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.
[0130] The low pressure oil passage 40 opens at the periphery between the end face of the
flange 120 and the auxiliary joint 102.
[0131] 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.
[0132] 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.
[0133] A tube proper 133 within which a bladder 132 is fixed is secured by screw thread
to the auxiliary joints 102 and 103.
[0134] The core tube 101 is connected to both the auxiliary joints 102 and 103.
[0135] Diaphragm fabricated of flexible synthetic resinous : sheet or metallic foil can
be used for said bladder 132.
[0136] 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.
[0137] The fluid chamber 134 communicates to the high pressure oil passage 30 within the
core tube 101 through said orifices 117.
[0138] 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.
[0139] 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.
[0140] Said gas supply valve 114 is exposed to the outside when the auxiliary joint 103
is removed from the joint 1
19 thereby permitting adjustment of the supplied gas.
[0141] 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.
[0142] 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 lead to those formed in the joints 118 and 119.
[0143] 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 joints
118 and 119.
[0144] 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
ba y pressure imparted 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.
[0145] 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.
[0146] Gas pressure within the gas chamber 135 changed (lowered) by repeated operation can
be adjusted by the gas supply valve 114.
[0147] 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.
[0148] In this embodiment explained above, an example where connection 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.