Fluid operated drilling device and a method for drilling a hole using a fluid operated drilling device

Abstract

A fluid operated drilling device for drilling a hole said device having a hammer, a rotation device and a drill rod. The hammer includes a tubular main body, a back head, a cylindrical piston housing, a reciprocating piston, a space, a valve unit and a fluid pressure supply unit. A hollow portion of the piston is open to lead pressurized operating fluid directly to the hollow portion from the fluid pressure supply passage. The hammer includes an axial exhaust passage formed between the main body and the piston housing. The valve unit includes a valve exhaust passage and the piston has a lower part and an upper part detachably connected to each other. The invention also relates to a method for drilling a hole using the fluid operated drilling device.

Claims

1. A fluid operated drilling device for drilling a hole, the drilling device comprising: a hammer for creating the hole with a rotating and percussive motion; a rotation device for rotating the hammer; and a drill rod connecting the rotation device to the hammer and transporting pressurized operating fluid to the hammer for creating the percussive motion of the hammer, wherein the hammer comprises: a tubular main body having a hollow interior; a back head, for connecting the hammer to the drill rod, coupled to an upper end of the main body and having a fluid pressure supply passage; a cylindrical piston housing connected to the main body inside the main body; a reciprocating piston slidably installed in the piston housing, for impacting a drill bit of a bit unit installed at a lower end of the main body, the drill bit being movable for a predetermined length longitudinally relative to the main body, the piston having: a first end and a second end, the first end being closer to the drill rod, a lower part and an upper part detachably connected to each other, a hollow portion, a first communication hole connected to the hollow portion and an annular pressurizing portion protruding on an outer circumferential surface of the piston, the hollow portion being open to lead pressurized operating fluid directly to the hollow portion of the piston from the fluid pressure supply passage; a space between the piston and the piston housing divided by the annular pressurizing portion in a radial direction of the piston into a first space portion for elevating the piston and a second space portion for pressurized operating fluid when striking the piston, the first space portion and the second space portion being connected to the hollow portion of the piston via the first communication hole; a second space in the hollow interior of the main body between the piston and the main body in the radial direction of the piston and between the piston housing and the bit unit in the axial direction of the piston; a second hollow portion in the piston for leading discharged fluid through the piston to the drill bit and out of the hammer; first communication channels formed in the piston connecting the second space to the second hollow portion for leading discharged fluid from between the piston and the main body back inside the piston to the second hollow portion; a valve unit for controlling fluid discharge from the second space portion, the valve unit including a valve exhaust passage for discharging fluid from the second space portion; a fluid pressure supply unit for supplying high pressure fluid delivered to the fluid pressure supply passage of the back head to the first space portion and the second space portion; and an axial exhaust passage formed between the main body and the piston housing for discharging fluid outside the piston housing; wherein the fluid discharged from the second space portion is led through the valve exhaust passage and the axial exhaust passage, and the rotation device rotates the bit unit using the drill rod and the main body.

2. The drilling device according to claim 1, wherein the piston has at least a first diameter over a first length of the piston between the piston housing and the bit unit outside a partial length of the piston housing and a second diameter over the partial length of the housing for limiting the space, wherein a portion of the piston with the first diameter is larger in diameter than the second diameter.

3. The drilling device according to claim 2, wherein the first space portion for elevating the piston and second space portion for pressurized operating fluid when striking the piston form piston reciprocating equipment which are located outside the first length of the piston, which first length is at the second end of the piston.

4. The drilling device according to claim 2, wherein a diameter of the hollow portion is smaller than a diameter of the valve exhaust passage and the diameter of the valve exhaust passage is smaller than a diameter of the axial exhaust passage in order to reduce back pressure created by the hammer.

5. The drilling device according to claim 1, wherein the piston comprises a male piston connection member and a female piston connection member of which one is a part of the lower part of the piston and other is a part of the upper part of the piston.

6. The drilling device according to claim 1, wherein the upper part of the piston comprises the hollow portion, the first communication hole and the annular pressurizing portion, and the lower part comprises the second hollow portion and the first communication channels.

7. The drilling device according to claim 1, wherein the piston housing is a single uniform part.

8. The drilling device according to claim 1, wherein the lower part and the upper part of the piston are made of different materials.

9. The drilling device according to claim 1, wherein the hammer comprises a piston guide bearing in connection with the bit unit for supporting the piston, and second communication channels arranged in the piston guide bearing to provide discharged fluid between the piston and the drill bit at least when the piston is elevated.

10. The drilling device according to claim 1, wherein the hollow portion and the second hollow portion are separated from each other by a solid portion belonging to the piston.

11. The drilling device according to claim 1, wherein the axial exhaust passage is located in the axial direction of the hammer between a lower end of the piston housing and lower end of the back head and in a radial direction between the piston housing and the main body.

12. The drilling device according to claim 1, wherein a diameter of the hollow portion of the piston is 80-120% of a diameter of the fluid pressure supply passage.

13. The drilling device according to claim 1, wherein the hammer comprises a piston upper hat having a second fluid pressure supply passage for guiding pressurized operating fluid into the hollow portion of the piston and a third fluid pressure passage for guiding pressurized operating fluid behind the valve unit into a chamber.

14. The drilling device according to claim 1, wherein the hammer comprises a piston seal between the piston housing and the upper part of the piston, which piston seal is a continuous circular seal.

15. The drilling device according to claim 1, wherein the drill bit comprises a drill bit exhaust passage which is parallel to a direction of the axis of rotation of the drill rod.

16. A method for drilling a hole using a fluid operated drilling device, the method comprising steps of: pressurizing operating fluid with a fluid pressure supply unit to produce pressurized operating fluid; rotating a drill rod and a percussive hammer attached to the drill rod with a rotation device; leading the pressurized operating fluid to a percussive hammer through the drill rod; guiding the pressurized operating fluid from a back head through a fluid pressure supply passage directly to a hollow portion of the piston; using the pressurized operating fluid in the percussive hammer to alternately elevate and impact a percussive piston by pressurizing a first space portion inside a piston housing to elevate the piston and a second space portion inside the piston housing to impact the piston to cause the percussive motion of a drill bit installed axially movably on the piston, the piston having a lower part and an upper part detachably connected to each other; discharging fluid from the first space portion and the second space portion outside the piston housing through a valve exhaust passage and an axial exhaust passage to flush and lubricate a hollow interior of a main body between the piston and the main body of the hammer outside the piston housing; and guiding the discharged fluid back inside the piston from the hollow interior through first communication channels to a second hollow portion of the piston for leading the discharged fluid outside the hammer through the bit unit.

17. The method according to claim 16, wherein said operating fluid includes additives to increase the viscosity of operating fluid above viscosity of water.

18. The method according to claim 16, wherein said operating fluid is oil or mud.

19. The method according to claim 16, wherein the operating fluid has a viscosity of 0.01-20 Pas at a temperature of 20° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described below in detail by referring to the appended drawings that illustrate some of the embodiments of the invention, in which

(2) FIG. 1 is a side view of the drilling device according to a first embodiment of the invention,

(3) FIG. 2 is a cross-section of the hammer according to the first embodiment,

(4) FIG. 3a is an enlargement of the lower end of hammer of FIG. 2,

(5) FIG. 3b is an enlargement of the upper end of hammer of FIG. 2,

(6) FIGS. 4a-4p are cross-section views of the hammer according to the first embodiment in different stages of drilling,

(7) FIG. 5a is an enlargement of a second embodiment taken from location of the hammer indicated by the section B-B of FIG. 4d,

(8) FIG. 5b is a cross-section of section B-B of the second embodiment shown in FIG. 5a,

(9) FIG. 6a is an enlargement of a second embodiment taken from a location of the hammer indicated by the section E-E of FIG. 4d,

(10) FIG. 6b is a cross-section of section E-E of the second embodiment shown in FIG. 6a.

(11) In the drawings the following reference numbers are used to indicate features illustrated in the drawings

(12) 1 drilling device

(13) 9 percussive hammer

(14) 10 main body

(15) 12 hollow interior

(16) 14 back head

(17) 16 upper end of the main body

(18) 18 fluid pressure supply passage

(19) 20 piston housing

(20) 21 braking chamber

(21) 22 piston

(22) 23 second fluid pressure supply passage

(23) 24 drill bit

(24) 25 third fluid pressure supply passage

(25) 26 bit unit

(26) 28 lower end of the main body

(27) 30 hollow portion of the piston

(28) 32 annular pressurizing portion

(29) 33 valve exhaust passage

(30) 34 first communication hole

(31) 35 axial exhaust passage

(32) 36 piston's outer circumferential surface

(33) 37 second hollow portion of the piston

(34) 38 space

(35) 39 valve pressure passage

(36) 40 first space portion

(37) 42 second space portion

(38) 44 fluid pressure supply unit

(39) 46 drill rod

(40) 48 first communication channels

(41) 50 rotation device

(42) 52 second communication channels

(43) 54 drill bit nut

(44) 56 male piston connection member

(45) 58 female piston connection member

(46) 60 lower part of the piston

(47) 62 upper part of the piston

(48) 64 bearing hold

(49) 66 piston upper hat

(50) 68 adapter

(51) 70 valve housing

(52) 72 main chamber of the valve unit

(53) 74 hydraulic braking shoulder

(54) 76 valve unit

(55) 77 chamber

(56) 78 first end of the piston

(57) 79 second end of the piston

(58) 80 jacket pipe

(59) 82 lock pin

(60) 84 second space

(61) 86 piston guide bearing

(62) 88 drill bit exhaust passage

(63) 90 solid portion

(64) 92 third communication channel

(65) 94 piston reciprocating means

(66) 96 thread

(67) 98 piston seal

(68) 100 hole

(69) 102 ground

DETAILED DESCRIPTION OF THE INVENTION

(70) According to FIG. 1, the drilling device 1 according to the invention includes as main parts a hammer 9 for creating a hole 100 in the ground 102, a fluid operated rotation device 50 for rotating the hammer 9 and a drill rod 46 connecting the rotation device 50 to the hammer 9. Fluid pressure may be used to lubricate parts of the hammer, flush the hole and flush out any debris from inside the hammer. The rotation device may be rotated by an electrical motor or it may also be fluid operated. An insertion pipe is normally led behind the drill rod inside the hole. In the drilling device 1 according to FIG. 1 the rotation device 50 rotates the drill rod 46, which then rotates the main body 10 of the hammer. The main body 10 then rotates the drill bit while a piston of the hammer causes a reciprocating movement of the drill bit 24.

(71) FIG. 2 illustrates an embodiment of the hammer 9 that can be used in the drilling device 1 according to the invention. The hammer 9 comprises a tubular main body 10 having a hollow interior 12, a back head 14 coupled to an upper end 16 of the main body 10 and having a fluid pressure supply passage 18 as well as a cylindrical piston housing 20 connected to the main body 10, preferably inside the main body 10. The fluid pressure supply passage 18 is arranged straight through the back head 14 to guide pressurized fluid flow straight through a piston upper hat 66 into a hollow portion 30 of the piston 22. In addition, the piston 22 is installed in the piston housing 20 for striking a drill bit 24 of a bit unit 26 installed at a lower end 28 of the main body 10. The piston 22 is preferably installed and supported slidably inside the piston housing 20. The piston 22 has a hollow portion 30, a first communication hole 34 connected to the hollow portion 30 and an annular pressurizing portion 32 protruding on piston's outer circumferential surface 36. The hollow portion 30 is not continuous axially through the piston 22 as in prior art hammers, but rather there are separate passages inside the piston, i.e. the hollow portion 30 and a second hollow portion 37. The hollow portion 30 is affected by the pressurized operating fluid whereas the second hollow portion 37 is affected by only discharged fluid.

(72) In the hammer 9 there is a space 38 between the piston 22 and the piston housing 20 divided into first space portion 40 for elevating the piston 22 and second space portion 42 for striking the piston 22, along the length of the piston 22, the first space portions 40 and the second space portion 42 being preferably connected to the hollow portion 30 of the piston 22 via the first communication hole 34. In the embodiment disclosed in FIGS. 2-4p there are two first communication holes 34. The movement of the piston 22 and location of the annular pressurizing portion 32 in relation to the first space portion 40 and the second space portion 42 guides the elevation and impact motions of the piston 22.

(73) The piston housing 20 preferably extends only over a partial length L1 of the piston 22. Axial exhaust passages 35 are arranged on the outer circumference of the piston housing 22 in order to discharge fluid from the second space portion 42. The piston 22 preferably further includes first communication channels 48 between the second hollow portion 37 of the piston 22 and the main body 10 on the first length L2 of the piston 22 between the piston housing 20 and the bit unit 26 outside partial length L1 leading the discharged fluid back inside the piston 22. The invention can be implemented also without these first communication channels. The axial direction of the first communication channels 48 may be at an angle α in relation to the axial direction of the piston 22, which angle is 30-60°, preferably 40-50°, in order to decrease pressure losses caused by the change of direction of the fluid flow.

(74) The hammer also includes a valve unit 76 for discharging fluid from the second space portion 42 and a fluid pressure supply unit 44 for supplying pressurized operating fluid to the hollow portion 30 of the piston 22 and preferably also behind the valve unit 76. The pressurized operating fluid is delivered from the fluid pressure supply unit 44 through the drill rod 46, fluid pressure supply passage 18 of the back head 14 and through a second fluid pressure supply passage 23 of the piston upper hat 66 fitted at an end of the piston 22 straight to the hollow portion 30 of the piston 22. Alternatively, part of the pressurized operating fluid is led through a third fluid pressure supply passage 25 of the piston upper hat 66 to a chamber 77 behind the valve unit 76 and from that chamber 77 through a valve pressure passage 39 to a space behind the valve unit 76. In the embodiment of FIG. 3a the valve pressure passage 39 is formed differently. The valve unit may be a valve unit known from prior art. Preferably, fluid used in the drilling device and method according to the invention is fluid with high viscosity, most preferably oil or mud. Water may be used as well.

(75) Piston 22 shown in FIG. 2, also known as a percussive piston, has in its upper part 62 at least part of the first space portion 40, which can also be called a lifting chamfer area, and at least part of the second space portion 42, which can also be called the striking area. The annular pressurizing portion 32, also known as a chamfer dividing area, is used to separate the first space portion 40 from the second space portion 42. The drilling device according to the invention may also incorporate a valve unit 76 elongating the annular pressurizing portion 32 shown in FIGS. 2, 3a and 4a-4c, or alternatively a pilot pressure controlling member connecting to a main valve unit controlling the main flow of the mentioned piston axially by means of effecting the mentioned first space portion and second space portion in order to create a percussive motion of said percussive piston. The piston 22 may include two consecutive parts, a lower part 60 having preferably the first communication channels 48 and the upper part 62 having the annular pressurizing portion 32.

(76) In the invention the size of the first space portion or the second space portion is not limited as they can be elongated. The first space portion can be elongated towards the drill bit and the second space portion towards the main body. However, the annular pressurizing portion is located substantially at the top part of the piston at the piston's operation attitude.

(77) Second diameter D2 in the middle section of the piston 22 makes it possible for the first space portion 40 to lift the piston 22 because the lifting diameter on the annular pressurizing portion 32 is larger than diameter D2, which diameter difference together with pressurized operating fluid causes a force that lifts the piston 22 up to its striking position. According to one embodiment shown in FIG. 2, the hammer 9 includes a hydraulic braking shoulder 74 which causes a braking effect for the piston 22 when the piston 22 is going forward during an impact motion and hydraulic braking shoulder 74 enters into the area of smaller diameter of the piston housing 20, i.e. braking chamber 21. The smaller diameter of the piston housing effectively reduces the power of the lifting force needed when hammer is lifted from its bottom position after the impact motion has ended. The hydraulic braking shoulder could also be situated in the piston in such way that the hydraulic braking shoulder would provide a braking effect also when elevating the piston thus avoiding any contact between the annular pressurizing portion and the valve unit.

(78) The piston may also have a first diameter D1 which is preferably larger than second diameter D2. Since the piston 22 is supported only on the second diameter D2, the piston 22 may have a larger first diameter D1 increasing the mass of the piston and a third diameter D3 that may also be equal to or larger than second diameter D2. The hollow portion 30 of the piston 22 may have a diameter D4 which is 80-120% of a diameter D5 of the fluid pressure supply passage 18. This means that the speed of the fluid flow does not increase considerably or even decreases when pressurized operating fluid enters the hollow portion 30 of the piston 22. Although FIGS. 2-4p illustrate that the axial exhaust passage 35 is smaller than valve exhaust passage 33 and that valve exhaust passage 33 is smaller than diameter of the hollow portion 30, it should be understood that preferably the diameter of the hollow portion 30 is smaller than diameter of the valve exhaust passage 33 and the diameter of the valve exhaust passage 33 is smaller than diameter of axial exhaust passage 35 in order to reduce back pressure created by the hammer 9.

(79) The percussive piston 22 is configured to strike the percussive drill bit 24 of the drill bit unit 26 shown in FIGS. 3a and 3b. The drill bit unit 26 is attached to the main body 10 of the hammer 9 which is then connected to the drill rod 46 using a back head 14 attached to the hammer 9. The flow of the pressurized fluid is led through the drill rod 46 via the fluid pressure supply passage 18 of the back head 14 inside the hammer 9 to create the pressure of fluid to effect the percussive motion of the percussive piston 22 against percussive drill bit 24. As shown in FIGS. 2-4c the piston 22 comprises the lower part 60 assembled to transmit the percussive force to the drill bit 24 and upper part 62 assembled to effect reciprocating action of the percussive piston 22.

(80) The first space portion 40, also known as the lifting chamfer, inside the piston housing 20 is limited by piston housing 20 which is sealing and centralizing the piston 22. The piston housing 20 effectively limits the first space portion 40 towards the drill bit 24. The piston housing may include a second piston bearing as well as a sealing portion. Fluid is discharged through a valve exhaust passage 33 located in the valve unit 76 and then led to axial exhaust passages 35 located radially outside the piston housing 20. Discharged fluid passing the axial exhaust passage 35 is then led to the outside diameter of the piston 22, i.e. into a second space 84 in the hollow interior 12 of the main body 10. According to one preferred embodiment, part of the discharged fluid is transferred at least partially back inside piston 22 to the second hollow portion 37 or at least partially through a second communication channel 52 of the piston guide bearing 86, also known as the piston centralizing element. When piston 22 is elevated backwards after an impact motion, discharged fluid fills up the void created by the lifting piston 22 by leading fluid through the second hollow portion 37 as well as through the second communication channels 52 reducing the suction effect of the large piston 22. The second communication channels are not a compulsory part of the hammer but a preferable feature.

(81) In the present invention the pressurized area containing the pressurized operating fluid is only between the piston housing 20 and the valve housing 70 shown in FIG. 3a in the longitudinal direction of the piston 22 as well as in the hollow portion 30 of the piston 22. This makes it possible to use large piston diameters below the piston housing even almost as large as the main body's inner diameter if the piston is grooved in its axial direction. The impact force created by the piston is defined by the relation between the diameter of the piston inside the piston housing and the diameter of the piston at the annular pressurizing portion. The hollow portion 30 of the piston 22 is not continuous through the piston 22 from upper end of the piston 22 to the lower end but divided into two separate parts, i.e. the hollow portion 30 and the second hollow portion 37, by a solid portion 90.

(82) The flow path of fluid is disclosed in FIGS. 3a and 3b with dotted lines whereas FIGS. 4a-4p show different stages of percussive motion of the hammer. In FIG. 4a the hammer 9 is with the drill bit 24 in hang position. In this position, there is no resultant flow to drive the piston 22 of FIG. 4b upwards, therefore no movement of the piston 22. According to FIG. 4c the drill bit 24 makes contact with the deface to be drilled and moves upwards. In turn, the piston 22 shown in FIG. 4d also moves upwards and the annular pressurizing portion 32 of the piston 22 moves into the valve unit 76 in the circled area. Fluid flows down the fluid pressure supply passage 18 of the back head 14 and the second fluid pressure supply passage 23 of the piston upper hat 66 and then to the hollow portion 30 of the piston 22. This fluid flows out of the first communication holes 34 in the piston 22 and fills the first space portion 40. Now there is a build-up of pressure behind the annular pressurizing portion 32 in the first space portion 40. On the other side of the annular pressurizing portion 32, inside the second space portion 42, fluid is free to flow through the valve exhaust passage 33 to the axial exhaust passage 35. This pressure differential leads the piston 22 starting to be driven upwards against the force of gravity. There is also a residual flow of fluid flowing through the third fluid pressure supply passages 25 of the piston upper hat 66 towards the valve unit 76 via chamber 77 and valve pressure passage 39. This flow helps to keep the valve unit 76 in the closed position, aided by gravity.

(83) In FIGS. 4e and 4f the piston 22 moves upwards and away from the drill bit 24. The shoulder 75 of piston 22 starts to move into the smaller bore of the valve unit 76 in the area circled, preventing fluid within the second space portion 42 being able to flow through to valve exhaust passage 33. Now fluid within the second space portion 42 has nowhere to go, leading to a build-up of pressure. In FIGS. 4g and 4h the combination of this pressure build-up within the valve unit 76 and in the second space portion 42 forces the valve unit 76 to move upwards with the piston 22 against the force of gravity. In FIGS. 4i and 4j the upward momentum of the piston 22 allows the annular pressurizing portion 32 to pass through into the second space portion 42. This in turn, along with gravity, relieves the pressure inside the second space portion 42 and the piston 22 starts to decelerate. Also, the hydraulic braking shoulder 74 at the first space portion 40 passes into the smaller bore of the piston housing 20, as shown where circled, reducing the pressure below this and creating a greater pressure differential at the top end. This starts to drive the piston 22 downwards, accompanied by the gravitational force acting on it.

(84) In FIGS. 4k and 4l the piston 22 moves downwards towards the drill bit 24. The annular pressurizing portion 32 of the piston 22 moves back into the circled area of the valve unit 76. The downward momentum of the piston 22 brings the annular pressurizing portion 32 of the piston 22 outside the smaller bore of the valve unit 76, which allows any fluid in the second space portion 42 to flow to valve exhaust passage 33. In FIGS. 4m and 4n the piston 22 continues to move downwards towards the drill bit 24. Due to fluid in the second space portion 42 now being able to flow to the valve exhaust passage 33, the valve unit 76 moves downwards along with the piston 22 and aided by gravity. The valve exhaust passage 33 and the third fluid pressure passage 25 allow fluid to flow into a chamber 77 above the valve unit 76, helping the valve unit 76 to drop back down. In FIGS. 4o and 4p the hydraulic braking shoulder 74 moves close to small diameter in circled area in the first space portion 40 inside the piston housing 20. This movement has a cushioning effect and decelerates the piston 22. Downward motion of piston 22 continues through its momentum and gravitational pull and strikes the drill bit 24.

(85) The cycle of the percussive motion repeats from the stage wherein the piston is in contact with the drill bit onwards until the hammer is withdrawn, and then the drill bit goes down back into its hang position, resulting in the fluid freely flowing to through the first communication hole into the hollow portion of the piston, stopping the shuttling action.