Fluid operated drilling device and a method for drilling a hole

Abstract

A fluid operated drilling device for drilling a hole includes a hammer connected to a drill rod, and a rotation device to rotate the drill rod and the hammer. The hammer includes a tubular main body, a back head, a cylindrical piston housing, a reciprocating piston and a space between the piston. The piston housing is divided by an annular pressurizing portion into first and second space portions for elevating and striking the piston. First communication channels from a hollow portion of the piston into a second space between the piston and the main body discharge fluid between the piston and the main body. A method for drilling a hole using the fluid operated drilling device is also disclosed.

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 drill rod connected to the hammer; and a rotation device connected to the drill rod for rotating drill rod and the hammer, and transporting operating pressurized drill fluid through the drill rod to the hammer for creating the percussive motion of the hammer, the hammer comprising: a tubular main body having a hollow interior and an upper end and a lower end; a back head, for connecting the hammer the drill rod, coupled to the upper end of the main body and having a fluid pressure supply passage; a cylindrical piston housing; connected to the main body; a reciprocating piston slidably installed in the piston housing for impacting a drill bit of a bit unit installed at the lower end of the main body, the drill bit being movable for a predetermined length longitudinally relatively to the main body, the piston having a first end a second end, the first end being closer to the drill rod than the second end, a hollow portion through which operating fluid is discharged, a first communication hole connected to the hollow portion and an annular pressurizing portion protruding on an outer circumferential surface of the piston; a space between the piston and the piston housing divided by the annular pressurizing portion extending in a radial direction of the piston into a first space portion for elevating the piston and a second space portion for striking the piston; 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 axial direction of the piston; first communication channels from the hollow portion of the piston into the second space for discharging the fluid between the piston and the main body; a valve unit for controlling fluid discharge from the second space portion through the first communication hole to the hollow portion and; a fluid pressure supply unit for supplying high pressure fluid delivered to the fluid pressure supply passage of the back head alternately to the first space portion and the second space portion; wherein 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 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 length of the piston is 40-65% of the total length of the piston and the partial length is 10-25% of the total length of the piston.

4. The drilling device according to claim 2, wherein the first space portion for elevating the piston and the second space portion for striking the piston form piston reciprocating which is located outside the first length of the piston which first length is at the second end of the piston.

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

6. The drilling device according to claim 1, wherein the piston comprises a lower part and an upper part detachably connected to each other.

7. The drilling device according to claim 6, wherein both the lower part and the upper part include the hollow portion, and the upper part has the first communication hole and the annular pressurizing portion and the lower part has the first communication channels connected to the hollow portion for leading discharged fluid between the piston and the main body and back inside the piston.

8. The drilling device according to claim 6, 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 first communication channels have an axial direction at an angle in relation to the hollow portion, the angle being 30-60° relative to longitudinal direction of the piston.

10. 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 allow a flow of discharged fluid between the piston and the drill bit when the piston is elevated.

11. The drilling device according to claim 2, wherein a majority of a mass of the piston is located on the first length of the piston between the piston housing and the bit unit outside the partial length.

12. The drilling device according to claim 1, wherein the drill bit comprises shoulders or inserts arranged in the drill bit for impacting ground during drilling.

13. The drilling device according to claim 1, wherein the piston is arranged to cooperate with the valve unit for indicating the axial position of the piston relative to the valve unit.

14. The drilling device according to claim 1, wherein the hollow portion is discontinuous through the piston and includes two consecutive parts comprising an upper flow channel and a lower exhaust channel separated by a solid portion belonging to the piston.

15. The drilling device according to claim 14, wherein each part of the hollow portion has first communication channels for guiding discharged fluid into the second space from the upper flow channel and back inside the piston in the lower exhaust channel closer to the bit unit for leading the discharged fluid to the bit unit.

16. The drilling device according to claim 14, wherein the lower exhaust channel is open to the bit unit.

17. The drilling device according to claim 1, wherein a longitudinal length of the first space portion is 10-30% of a length of the piston.

18. The drilling device according to claim 2, wherein the piston housing extends only over the partial length of the piston forming the second space in the hollow interior of the main body.

19. The drilling device according to claim 1, wherein the first communication channels include upper communication channels from the hollow portion of the piston into the second space for discharging fluid between the piston and the main body and lower communication channels from the second space into the hollow portion of the piston for discharging fluid from the piston through the bit unit.

20. A method for drilling a hole using a fluid operated drilling device, which method includes steps of pressurizing pressurized operating fluid with a fluid pressure supply unit; rotating a drill rod and a percussive hammer attached to the drill rod with a rotation device, leading pressurized operating fluid to a percussive hammer through the drill rod; using 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 second space portion inside the piston housing to impact the piston to cause the percussive motion of a drill bit axially movably on the piston; guiding operating fluid discharged from the first space portion and the second space portion outside the piston 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 operating fluid discharged to the hollow interior back inside the piston before guiding the operating fluid through a bit unit.

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 the invention,

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

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

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

(6) FIGS. 4a-4c are cross-sectional views of the hammer according to an embodiment in different stages of drilling,

(7) FIG. 5 is a cross section I-I shown in FIG. 3a,

(8) FIG. 6 is a cross section G-G shown in FIG. 3b,

(9) FIG. 7 is a cross section H-H shown in FIG. 3b.

(10) In the drawings the following reference numbers are used to indicate features illustrated in the drawings: 1 drilling device 9 percussive hammer 10 main tube 12 hollow interior 14 back head 16 upper end of the main body 18 fluid pressure supply passage 20 piston housing 21 braking chamber 22 piston 24 drill bit 26 bit unit 28 lower end of the main tube 30 hollow portion of the piston 32 annular pressurizing portion 34 first communication hole 36 piston's outer circumferential surface 38 space 40 first space portion 42 second space portion 44 fluid pressure supply unit 46 drill rod 48 first communication channels 49.1 upper first communication channels 49.2 lower first communication channels 50 rotation device 52 second communication channels 54 drill bit nut 56 male piston connection member 58 female piston connection member 60 lower part of the piston 62 upper part of the piston 64 bearing hold 66 piston upper seal 68 adapter 70 valve housing 72 main chamber of the valve unit 74 hydraulic braking shoulder 76 valve unit 78 jacket pipe 80 piston plug 82 first end of the piston 84 second end of the piston 85 upper flow channel 86 piston guide bearing 87 lower exhaust channel 88 parts of hollow portion of the piston 90 solid portion 92 third communication channel 94 second fluid pressure supply passage 96 thread 98 part of valve unit 100 hole 102 ground

DETAILED DESCRIPTION OF THE INVENTION

(11) 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.

(12) 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. In addition, the hammer 9 includes a piston 22 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 through which fluid is discharged, 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. In the hammer 9 there is a space 38 between the piston 22 and the piston housing 20 divided into a 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 portion 40 and the second space portion 42 being alternately connected to the hollow portion 30 of the piston 22 via the first communication hole 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.

(13) The piston housing 20 extends only over a partial length L1 of the piston 22. The piston 22 further includes first communication channels 48 between hollow portion 30 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 for discharging fluid between the piston 22 and the main body 10. To be more precise the first communication channels 48 include upper first communication channels 49.1 for leading the operating fluid from inside the piston 22 to the hollow interior 12 and lower first communication channels 49.2 for leading the operating fluid from hollow interior 12 back inside the piston 22 before the fluid is discharged from the hammer through the bit unit 26. 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.

(14) The hammer also includes a valve unit 76 for distributing fluid pressure supply to either the first space portion 40 or the second space portion 42 and a fluid pressure supply unit 44 (see FIG. 1) for supplying high pressure fluid delivered to the fluid pressure supply passage 18 of the back head 14 to the first space portion 40 and the second space portion 42. The valve unit 76 may be a valve unit known from prior art. Preferably fluid used in the drilling device and method according to the invention is water since it is widely available. Fluid used may also be oil, mud or such.

(15) 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 the piston causes the reciprocating movement of the drill bit 24.

(16) Piston 22 shown in FIG. 2, also known as percussive piston, has in its upper part 62 at least part of the first space portion 40, which can also be called the 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 incorporate the valve unit 76 elongating the annular pressurizing portion 32 shown in FIGS. 2, 3a, 4a-4c and 5 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 alternately 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 the first communication channels 48 and an upper part 62 having the annular pressurizing portion 32.

(17) 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 32 is located substantially at the top part of the piston at the piston's operation attitude.

(18) A 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 second diameter D2, which diameter difference together with the pressurized operating fluid causes force that lifts the piston 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 impact motion and hydraulic braking shoulder 74 enters into the area of smaller diameter of the piston housing 20. The smaller diameter of the piston housing 20 effectively reduces the power of the lifting force needed when the hammer is lifted from its bottom position after the impact motion has ended.

(19) 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.

(20) 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 reciprocative action of the percussive piston 22.

(21) The first space portion 40, also known as the lifting chamfer, inside the piston housing 20 is limited by piston housing 20 which seals and centralizes 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. Discharged fluid is diverted to the outside diameter of the piston 22, i.e. into the hollow interior of the main body 10 somewhere along the piston 22 between piston housing 20 and percussive drill bit 24. According to one preferred embodiment, part of the discharged fluid is transferred at least partially back inside piston 22 to the hollow portion 30 or at least partially through a second communication channel 52 of a piston guide bearing 86, also known as the piston centralizing element. When piston 22 is being elevated backwards after impact motion, discharged fluid fills up a void created by the lifting piston 22 by leading the fluid through the first communication channels 48 and the part of the hollow portion 30 closer to the drill bit 24 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 are a preferable feature.

(22) In the present invention the pressurized area containing the pressurized operating fluid is only between the piston housing and a valve housing 70 (see FIG. 3a) in the longitudinal direction 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. Preferably the hollow portion 30 of the piston 22 is not continuous through the piston from upper end of the piston 22 to the lower end, but divided into two separate parts 88 by a solid portion 90.

(23) The flow path of fluid is disclosed in FIGS. 3a and 3b with dotted lines whereas FIGS. 4a-4c show different stages of percussive motion of the hammer. In FIG. 4a the hammer 9 is with the drill bit 24 in hang position. All fluid is free to flow through the first communication hole 34 into the hollow portion 30 of the piston 22, so there is no pressure differential and therefore no movement of the piston 22. In FIG. 4b the drill bit 24 is in contact with the face of the ground to be drilled and moves upwards. In turn, the piston 22 also moves upwards and the annular pressurizing portion 32 of the piston 22 moves into part 98 of the valve unit 76. Fluid within the valve unit 76 can still flow through the first communication hole 34 into the hollow portion 30 of the piston 22 but now there is a build-up of pressure behind the annular pressurizing portion 32 between the annular pressurizing portion 32 and the hydraulic braking shoulder 74 of the piston 22, driving the piston 22 upwards.

(24) The piston 22 moves upwards and away from the drill bit 24. The piston's 22 first communication hole 34 starts to move into the smaller bore of the valve unit 76 shown in FIG. 4c, which in turn stops any fluid within the valve unit 76 going through the first communication hole 34 into the hollow portion 30 of the piston 22, leading to a build-up of pressure inside the valve unit 76. A combination of this pressure build-up within the valve unit 76 and the pressure build-up at the base of the valve unit 76 forces the valve unit 76 to move upwards with the piston 22. The upward momentum of the piston 22 allows the annular pressurizing portion 32 to pass through into the main chamber 72 of the valve unit 76. This in turn relieves the pressure inside the valve unit and the piston 22 starts to decelerate. Also, the hydraulic braking shoulder 74 of the piston 22 passes into the small bore of the piston housing 20 reducing the pressure below this and creating a greater pressure differential at the top end, which starts to drive the piston 22 downwards.

(25) The piston 22 moves downwards towards the drill bit 24. The annular pressurizing portion 32 of the piston 22 moves back into the part 98 of the valve unit 76 shown in FIG. 4b. The downward momentum of the piston 22 brings the first communication hole 34 into the main chamber 72 of the valve unit 76, which allows any fluid in the main chamber 72 to flow through the first communication hole 34 into the hollow portion 30 of the piston 22. The piston 22 continues to move downwards towards the drill bit 24. Due to the fluid in the valve unit 76 now being able to flow through the first communication hole 34 into the hollow portion 30 of the piston 22, the valve unit 76 moves downwards along with the piston 22. The hydraulic braking shoulder 74 of the piston 22 moves close to a small diameter of a braking chamber 21 of the piston housing 20 shown in FIG. 4b, which has a cushioning effect and decelerates the piston 22. At the end of the cycle the piston 22 strikes the drill bit 24.

(26) 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 through the first communication hole 34 into the hollow portion 30 of the piston, stopping the shuttling action.