A DRILL ASSEMBLY FOR PERCUSSIVE DRILLING

Abstract

A drill assembly for percussive drilling, comprising a drill bit and a percussion device. The drill assembly further includes a hollow cylindrical foot valve partially received within a first central flushing channel thereof and extending therefrom in the uphole direction, such that the foot valve is also partially received within a central recess of an impact piston of the percussion device, at least when the impact piston is in a lowermost position of its reciprocation cycle, and such that the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle. The foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve.

Claims

1-9. (canceled)

10. A drill assembly for percussive drilling, the drill assembly comprising: a drill bit extending along a longitudinal direction and including: a distal portion having an end surface equipped with inserts configured for transferring percussive impact to points of contact with a borehole during operation; a shank portion extending from the distal portion in an uphole direction, the shank portion being equipped with a male coupling configuration and, on a longitudinal uphole end of the shank portion, a first impact surface; and a first central flushing channel for conducting a flushing fluid flow to an end surface of the distal portion, said central flushing channel extending through at least the shank portion and being open towards the longitudinal uphole end of the shank portion, such that the first impact surface is formed annularly around the first central flushing channel; a percussion device extending along a longitudinal direction and including: on a downhole side end thereof, a female coupling configuration for coupling with the male coupling configuration of the drill bit; and an impact piston arranged within a housing and configured to reciprocate in the longitudinal direction when a flushing fluid flow is conducted through the percussion device, the impact piston having, on the downhole end of the piston, a central recess and a second impact surface annularly surrounding the central recess for impacting against the first impact surface of the drill bit when the impact piston is reciprocated during a reciprocation cycle; and a hollow cylindrical foot valve attached to the drill bit and partially received within the first central flushing channel and extending therefrom in an uphole direction, such that: the foot valve is also partially received within the central recess, at least when the impact piston is in a lowermost position of its reciprocation cycle; and the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle; wherein the foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve; and wherein the internal stiffener is formed as an integral part of the foot valve, as one or more internal walls of the foot valve.

11. The drill assembly according to claim 10, wherein the internal stiffener extends along a longitudinal length of the foot valve.

12. The drill assembly according to claim 10, wherein the internal stiffener is formed as a plurality of internal walls of the foot valve such that at least two of the internal walls coincide with each other, as seen along a cross-sectional profile of the foot valve perpendicular to a longitudinal direction thereof.

13. The drill assembly according to claim 10, wherein the internal stiffener is formed as a plurality of internal walls of the foot valve such that at least two of the internal walls intersect with each other, as seen along a cross-sectional profile of the foot valve perpendicular to a longitudinal direction thereof.

14. The drill assembly according to claim 10, wherein the internal stiffener extends longitudinally for a first distance from an uphole side end of the foot valve, the first distance being more than or equal to a distance for which the foot valve projects from the drill bit.

15. The drill assembly according to claim 10, wherein the internal stiffener extends longitudinally for a first distance from an uphole side end of the foot valve, the first distance being less than or equal to a distance for which the foot valve projects from the drill bit.

16. The drill assembly according to claim 10, comprising: a cut-out extending radially through foot valve, extending axially for a second distance from a downhole side end of the foot valve, wherein the second distance is less than or equal to a length at which the foot valve is received within the drill bit.

17. The drill assembly according to claim 16, wherein a projection of the cut-out on a plane parallel with the longitudinal direction is a differentiable curvature opening towards a downhole side end of the foot valve.

18. The drill assembly according to claim 10, wherein the foot valve is provided with a section of increased outer diameter at a portion of the foot valve received within the drill bit.

19. The drill assembly according to claim 11, wherein the internal stiffener is formed as a plurality of internal walls of the foot valve such that at least two of the internal walls coincide with each other, as seen along a cross-sectional profile of the foot valve perpendicular to a longitudinal direction thereof.

20. The drill assembly according to claim 11, wherein the internal stiffener is formed as a plurality of internal walls of the foot valve such that at least two of the internal walls intersect with each other, as seen along a cross-sectional profile of the foot valve perpendicular to a longitudinal direction thereof.

21. The drill assembly according to claim 11, wherein the internal stiffener extends longitudinally for a first distance from an uphole side end of the foot valve, the first distance being more than or equal to a distance for which the foot valve projects from the drill bit.

22. The drill assembly according to claim 11, wherein the internal stiffener extends longitudinally for a first distance from an uphole side end of the foot valve, the first distance being less than or equal to a distance for which the foot valve projects from the drill bit.

23. The drill assembly according to claim 11, comprising: a cut-out extending radially through foot valve, extending axially for a second distance from a downhole side end of the foot valve, wherein the second distance is less than or equal to a length at which the foot valve is received within the drill bit.

24. The drill assembly according to claim 23, wherein a projection of the cut-out on a plane parallel with the longitudinal direction is a differentiable curvature opening towards a downhole side end of the foot valve.

25. The drill assembly according to claim 11, wherein the foot valve is provided with a section of increased outer diameter at a portion of the foot valve received within the drill bit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

[0042] FIG. 1 and FIG. 2 illustrate longitudinal cut view of a drill assembly according to the present disclosure.

[0043] FIG. 3a-FIG. 8c illustrate various embodiments of a foot valve according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0044] FIG. 1 illustrates a longitudinal cut view of a drill assembly 1 according to the present disclosure. The drill assembly 1 comprises a drill bit 2 having a distal portion (3) at the downhole end side of the drill bit. The distal portion 3 is equipped, at an end surface thereof, with inserts 3a for cutting and/or crushing the ground at the bottom of the borehole. A shank portion 4 extends from the distal portion towards an uphole direction, and has a first impact surface 4a on a longitudinal uphole end thereof. A first central flushing channel 5 extends at least through the shank portion 4 so as to conduct a flushing fluid flow to the end surface of the distal portion 3. Particularly the first impact surface 4a is formed annularly around the first central flushing channel 5.

[0045] The drill assembly further comprises a percussion device 6, generally known as a DTH-hammer. The percussion device is coupled to the shank portion of the drill bit with mutual engaging surfaces, such as a male and female splined surfaces on the shank portion and on the downhole side end of the percussion device, respectively.

[0046] Particularly, the percussion device 6 has an impact piston arranged within a housing, which is configured to reciprocate in the longitudinal direction, when a flushing fluid flow is conducted through the percussion device. The impact piston 7 has a central recess 8 provided as a second central flushing channel for conducting a flushing fluid flow through the impact piston 7. A second impact surface 7a of the impact piston annularly surrounds the second central flushing channel 8.

[0047] FIG. 1 also illustrates a hollow cylindrical foot valve 9 attached to the drill bit 2 and partially received within the first central flushing channel 5 and extending therefrom in the uphole direction.

[0048] Particularly, FIG. 1 illustrates the drill assembly in situation in which the impact piston 7 is in an uppermost positions of its reciprocation cycle, wherein the second impact surface 7a is distanced from the first impact surface 4a and the foot valve 9 is not received within the second central flushing channel 8

[0049] FIG. 2, in turn, illustrates the drill assembly of FIG. 1 when the impact piston is in a lowermost position of its reciprocation cycle, wherein the first and second impact surfaces 4a, 7a abut each other, and the foot valve 9 partially received also within the second central flushing channel.

[0050] FIG. 3a-FIG. 3c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan vie, longitudinally cut view and a side view, respectively. Particularly, the stiffener 10 has been provided as a single linear internal wall 10a extending between opposing point of internal surface of the foot valve 9, through a cross-sectional centre point thereof.

[0051] As best illustrated in FIG. 3a, the material thickness of the internal wall 10a is increased where the internal wall 10a adjoins the internal surface of the foot valve 9. Moreover, the internal wall 10a extends for distance from the uphole side ned of the foot valve 9 such that it does not extend up to the opposing downhole side end of the foot valve 9. Additionally, the foot valve 9 is provided with a section of increased outer diameter 9b at a distance from the downhole side end of the foot valve 9. Notably, the section of increased outer diameter 9b is provided at a portion of the foot valve 9 where the stiffener 10 is not exhibited. In use, the section of increased diameter 9b resides within the first central flushing channel 5.

[0052] FIG. 4a-FIG. 4c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan view, longitudinally cut view and a side view, respectively. The embodiment of FIGS. 4a-4c is similar to that illustrated in FIG. 3a-FIG. 3c with the exception that the stiffener 10 is provided as curved internal wall 10a which does not run through the cross-sectional centre point of the foot valve 9, and extends along the whole length of the foot valve 9.

[0053] FIG. 5a-FIG. 5c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan view, longitudinally cut view and a side view, respectively. The embodiment of FIGS. 5a-5c is similar to that illustrated in FIG. 3a-FIG. 3c with the exception that the stiffener 10 is provided as two intersecting internal walls 10a forming a cross-like cross-sectional profile, in which the internal walls coincide at the cross-sectional centre point of the foot valve 9.

[0054] FIG. 6a-FIG. 6c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan view, longitudinally cut view and a side view, respectively. The embodiment of FIGS. 6a-6c is similar to that illustrated in FIG. 3a-FIG. 3c with the exception that the stiffener 10 is provided as a plurality of coinciding internal walls 10a forming a central tubular cross-sectional profile, from which radially extending spokes extend between the central tubular portion and the internal wall of the foot valve 9.

[0055] FIG. 7a-FIG. 7c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan view, longitudinally cut view and a side view, respectively. The embodiment of FIGS. 7a-7c is similar to that illustrated in FIG. 3a-FIG. 3c with the exception that the stiffener 10 is provided as a plurality of intersecting internal walls 10a forming cross-sectional rectangular grid-like pattern, in which rectangular cavities are formed between the internal walls 10a, and the stiffener 10 extends along the whole length of the foot valve 9.

[0056] FIG. 8a-FIG. 8c illustrate an embodiment of the foot valve 9 according to the present disclosure as seen as plan view, longitudinally cut view and a side view, respectively. The embodiment of FIGS. 8a-8c is similar to that illustrated in FIG. 3a-FIG. 3c with the exception that the stiffener 10 is provided as a plurality of intersecting internal walls 10a forming cross-sectional tubular grid-like pattern, in which tubular cavities are formed between the internal walls 10a.

[0057] It should be noted that the appended drawings illustrate exemplary embodiments of the present disclosure, and that other, non-illustrated embodiments are also encompassed by the present disclosure. For example, the stiffener may alternatively be provided as internal splines, i.e. axially extending radial bulges, at which the material thickness of the foot valve is increased.