Technical Field

[0001] The present disclosure relates to replaceable wear components subject to sliding friction abrasion in down-the-hole tools, such as piston actuated drilling tools, although not exclusively, to percussion tools for downhole drilling.

Background

[0002] Drilling in rock can be performed by percussive drilling, which is a combination of percussion and rotation. Percussive drilling and down-the-hole drilling (DTH) present difficulties with regard to repair and maintenance.

[0003] Percussive drilling and DTH tools use a piston assembly that slidably oscillates against, or relative to, non-moving components. The tool components create wear at specific locations. Over time this wear causes internal clearances to increase such that leakages increase, which reduce pressure and, therefore, operational efficiency of the piston system. In the above-described drilling tool, individual parts may be worn, but to replace such worn parts the entire assembly must be replaced.

[0004] Customarily, with percussive drilling and DTH hammer assemblies, the parts are inspected and when necessary replaced, which often involves rebuild. This process is time consuming and increases EHS risks, shipping, and inventory.

Summary

[0005] The present disclosure provides a system of replaceable components at high wear areas in a percussion tool. In order to reduce costs and increase turnaround time, the components in the high wear areas can be replaced improving percussion efficiency closer to design standard. The components are low cost and light weight reducing service costs and effort supporting tool maintenance. The replaceable components can be designed into the system so that only those components are replaced during service. [0006] Further improvements are made by use of sliding wear bushing components that slightly increases pressure thereby offsetting ongoing losses due to increasing clearances.

[0007] One area of wear requires sliding and impact protection. This can be achieved by a replaceable sleeve held in place by friction or other mechanical fastening methods.

[0008] The sleeve may be combined with surface lubrication/corrosion protection and/or coated with modified surface properties.

[0009] An alternate embodiment includes a sleeve that may slide with respect to the guide sleeve in order to alter pressure and/or timing events of the piston, as wear in all locations allows additional leakage and thereby reducing designed power. Slight vertical axial movement of the replaceable sleeve will alter pressure and timing on the up and down strokes. Sleeve material may be polymer, ferrous, and non-ferrous.

[0010] Another wear area requires sliding protection without additional drag or scraping against the casing wall. This is most economically achieved by use of rings fitted to special grooves pre-machined into the piston outer diameter. The rings are specially designed to improve sealing of the worn faces while not increasing drag resistance of the ring to casing wall, which cannot be 100% prevented, decreases power by decreasing velocity of the piston. Multiple rings may be used on a single piston. Ring material may be polymer, ferrous, and non-ferrous.

[0011] In order to reduce cost and increase turn-around time the areas mentioned above can be repaired sufficiently and quickly by using replaceable elements specifically designed for these locations.

[0012] Accordingly, in one embodiment the present piston actuated drilling tool includes a casing having opposed top and bottom ends and an inner surface. A guide sleeve is disposed within the casing in proximity to the top end of the casing. The guide sleeve has an inner surface and an outer surface, the outer surface of the guide sleeve contacting the inner surface of the casing. A piston slidably is disposed within the casing for reciprocating movement therein, the piston having a nose end arranged to reciprocate within the guide sleeve, wherein a first wear area of the tool occurs between the piston nose end and the guide sleeve. A replaceable wear bushing assembly is located within the guide sleeve at the first wear area. [0013] In one embodiment, the wear bushing assembly includes a static wear bushing, with the nose end of the piston reciprocating within the static bushing.

[0014] In one embodiment, the static wear bushing is a solid piece.

[0015] In one embodiment, the static wear bushing is a split ring.

[0016] In one embodiment, the static wear bushing is a polymer, ferrous, or nonferrous material, wherein the inner and outer surfaces of the wear bushing are coated or heat treated.

[0017] In one embodiment, the wear bushing assembly includes a sliding wear bushing arranged to move within the guide sleeve, with the nose end of the piston reciprocating within the sliding wear bushing.

[0018] In one embodiment, a position of the sliding wear bushing within the guide sleeve can be inverted to change the sliding wear bushing to a static bushing. [0019] In one embodiment, the sliding wear bushing is a polymer, ferrous, or non-ferrous material, and the inner and outer surfaces of the sliding wear bushing are coated or heat treated.

[0020] In one embodiment, the wear bushing assembly includes a gland seal located at one end of the sliding wear bushing and a spring mechanism located at another end of the sliding wear bushing, both the sliding gland seal and the spring mechanism being disposed between an outer surface of the sliding wear bushing and the inner surface of the guide sleeve, wherein the gland seal is made of a flexible material such as polymer, elastomer, rubber or ferrous or non-ferrous metals, wherein the gland seal includes a pair of legs.

[0021] In one embodiment, the wear bushing assembly includes a split ring located at one end of the sliding wear bushing, the split ring being disposed between an outer surface of the sliding wear bushing and the inner surface of the guide sleeve. [0022] In one embodiment, a spacer ring is positioned between the split ring and a shoulder of the sliding bushing, the spacer ring being arranged as a retention ring to keep the sliding wear bushing in a static position.

[0023] In one embodiment, the spacer ring and split ring are made of polymer, elastomer, rubber or ferrous or non-ferrous metals.

[0024] In one embodiment, a second wear area (WA2) of the tool occurs between the inner surface of the casing and the outer surface of the piston, the outer surface of the piston including at least one groove and a piston ring provided in the at least one groove and arranged to protect the piston from wear in the second wear area. [0025] In one embodiment, the at least one piston ring has overlapping ends. [0026] In one embodiment, a piston actuated drilling tool comprises a casing having opposed top and bottom ends and an inner surface, a guide sleeve disposed within the casing in proximity to the top end of the casing, the guide sleeve having an inner surface and an outer surface, the outer surface of the guide sleeve contacting the inner surface of the casing, a piston slidably disposed within casing for reciprocating movement therein, the piston having a nose end arranged to reciprocate within the guide sleeve, wherein a first wear area of the tool occurs between the piston nose end and the guide sleeve, a replaceable wear bushing assembly located within the guide sleeve at the first wear area, the replaceable wear bushing assembly comprising a sliding wear bushing arranged to move within the guide sleeve, a gland seal located at one end of the sliding wear bushing and a spring mechanism located at another end of the sliding wear bushing.

[0027] The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown.

Brief Description Of The Drawings

[0028] Fig. 1A is a longitudinal cross-section of a rotary percussion tool.

[0029] Fig. IB is an enlarged section of the tool of Fig. 1A. [0030] Fig 2 is a front view of a solid static bushing according to the present disclosure.

[0031] Fig. 3 is a perspective view of a split static bushing according to the present disclosure.

[0032] Fig. 4 is a front view of a static gland seal according to the present disclosure.

[0033] Fig. 5 is a cross-sectional view of the replaceable wear bushing assembly according to the present disclosure.

[0034] Fig. 6 is a cross-sectional view of a drilling tool incorporating the replaceable wear bushing assembly of Fig. 5.

[0035] Fig. 7 is a cross-sectional view of another embodiment of a replaceable wear bushing assembly of the present disclosure incorporating a sliding wear bushing.

[0036] Fig. 8 is an enlarged view of the bushing assembly of Fig. 7.

[0037] Fig. 9 is an enlarged cross-sectional view of another bushing assembly having a split ring seal.

[0038] Fig. 10 is a perspective view of the split ring of Fig. 9.

[0039] Fig. 11 is an enlarged view of a split ring and spacer ring incorporated in another embodiment of a sliding wear bushing of the present disclosure.

[0040] Fig. 12 is a cross-sectional view of the sliding wear bushing assembly of Fig. 11.

[0041] Fig. 13 is a perspective view of a piston having sealing rings according to the present disclosure.

[0042] Fig. 14 is an enlarged cross-section of the piston of Fig. 13 positioned within a drilling tool.

[0043] Fig. 15 is a perspective view of the piston ring of Figs. 13 and 14.

[0044] Fig. 16 is an enlarged cross-section of the ends of the ring.

[0045] Fig. 17 is another embodiment of the piston ring having overlapping ends.

[0046] Fig. 18 is an enlarged side view of the overlapping ends of the ring of Fig.

17. Detailed Description

[0047] Referring to Fig. 1A, a piston actuated DTH drilling tool 10 includes a casing or housing 12 having opposed top and bottom ends. A drive sub 14 is threadedly mounted to the bottom/drive end 11 of the casing 12. A top sub 16 is threadedly coupled to the top end 9 of the casing 12. A piston 20 is movably disposed within casing 12. Piston 20 includes a choke 30 and a nose end 21. As is well known, the movement of piston 20 is regulated by the timing of pressure between fluid chambers formed in the casing. The drive sub 14 includes one or more annularly shaped drive lugs 26 that are stacked on top of one another and a portion of a mandrel 22. The mandrel 22 is a substantially solid component to which a drill bit (not shown)can be attached to. The mandrel 22 is axially moveable with respect to both the casing 12 and the drive sub 14, a portion of the mandrel 22 being inserted and housed within the casing 12. The top sub 16 is threadedly connected to a drill string (not shown), which is connected to a rotation motor on a drilling rig at the surface. Rotational torque is then applied through the rotating assembly including casing 12, drive sub 14, drive lugs 26, and mandrel 22.

[0048] Fig. IB illustrates two areas of wear, wear area 1 (WAi) and wear area 2 (WA2). WAi occurs between the head 36 of the piston and shoulder 38 of guide sleeve 18. WA2 occurs between inner surface 13 of casing 12 and an outer surface of 23 of piston 20. Guide sleeve 18 has inner surface 17 and outer surface 19.

[0049] Wear primarily occurs along these two areas for separate reasons. At area WAi the piston is slidably entering the guide sleeve, repeatably, along with any entrainments in the motive force and lubrication causing both sliding wear and contact wear as the piston moves about its central axis. At area WA2 the large diameter of the piston is sliding against the large diameter casing along with any entrainments in the motive force and lubrication exciting wear on both surfaces. [0050] Figs 2 -5 refer to a replaceable wear bushing assembly 50 (Fig. 5).

Assembly 50 includes a solid static annular/ring-shaped bushing 52 and a static gland seal 60, which can be provided to provide protection at WAi (Fig. IB). As shown in Fig. 2, bushing 52 can be a solid static bushing made of a ferrous or non- ferrous metal. Bushing 52 can be a drop in replaceable insert that is also reversible.

[0051] Alternatively, as shown in Fig. 3, the bushing can be a split static bushing 52’ that is split at cut 48. Splitting the static bushing eases installation. Often rust can occur at the interface between bushing 52 and the guide sleeve 18, so splitting the bushing can also ease removal. Bushing 52 can include indents or holes 51, which snap ring pliers or another tool can fit with to assist with installation or removal. It should be appreciated that solid static bushing 52 can also include the indents or holes to assist with install/removal.

[0052] Outer and inner surfaces 53, 55 of static bushing 50, 50’ can be coated or treated with a secondary heat treatment process to increase wear resistance, hardness, lubricity, modify properties or a combination of any/all.

[0053] Referring again to Figs. 2 and 3, static bushing 52, 52’ includes an upper portion 56, upper shoulder 58, lower portion 54 and a lower shoulder 59. As will be explained further herein, upper shoulder 58 is arranged to support and retain static gland seal 60 and lower shoulder 59 is provided to locate the bushing in guide sleeve 18. Gland seal 60 prevents bushing 52. 52’ from interfering with the top sub assembly due to it retaining bushing position. Seal 60 also provides some amount of sealing by preventing water from seeping between the bushing and guide sleeve’ It should be appreciated that the bushing can be held in place by friction or other mechanical fastening methods.

[0054] Referring to Figs. 4 and 5, static gland seal 60 is ring shaped and has an inner diameter 62 that corresponds to the outer diameter of upper portion 56 of static bushing 52, 52’. Gland seal 60 can be a ferrous, nonferrous, elastomer or rubber element that holds bushing 52, 52’in place. Upper shoulder 58 supports gland seal 60. Due to bushing having both shoulders 58, 59, as set forth above, the bushing is reversible, i.e., lower portion 54 would become an upper portion and lower shoulder 59 would support seal 60. [0055] Gland seal 60 includes a rib 64 that provides sealing for the interface gaps between bushing 52, 52’ and guide sleeve 18. Gland seal 60 further aids installation effectiveness by visual and tactile reinforcement.

[0056] As shown in Fig. 5, static bushing 52 has a height H. Height H is critical as the bushing cannot extend above the guide sleeve. Bushing 52 come in differing sectional length/heights to compensate for low to heavy wear conditions.

[0057] Height H cannot interfere with the top sub 16, when installed, and simultaneously provide the timing event as the piston moves up and down. The timing event is controlled at the inside edge of bushing 54 (or 56 when reversed as described further herein). These edges are controlled by H and located by the shoulders 58/59 and held in place by friction, gland seal 60, or other mechanical retention.

[0058] As shown in Fig. 6, static bushing 52 is positioned such that guide sleeve 18 is protected from wear by piston head 36 at WAi. Thus, bushing assembly 50 provides sliding and impact protection. Outer surface 17 contacts inner surface 53 of guide sleeve 18.

[0059] An alternate embodiment of the bushing assembly is shown in Figs. 7 and 8, wherein the bushing may slide with respect to the guide sleeve 18 in order to alter timing and pressure at that point and to prevent wear in all locations that would allow additional leakage and thereby reducing designed power.

[0060] Sliding wear bushing 70 includes a gland seal 80 in the shape of a wiper having legs 82, 84, and a spring mechanism 90. Sliding bushing 70 may be polymer, ferrous, and non-ferrous material. Sliding bushing 70 includes an upper portion 72 with an upper shoulder 74 and a lower portion 76 having a lower shoulder 78.

[0061] Gland seal 80 is supported by upper shoulder 74 of sliding bushing 70 and extends into indentation 66 formed in guide sleeve 18 such that legs 82,84 of seal 80 are delimitated by indentation 66 and shoulder 74. Gland seal 80 can be made of a flexible material such as polymer, elastomer, or ferrous or non-ferrous metals. [0062] Spring mechanism 90 is arranged at the lower portion 76 of sliding bushing 70 and extends between a shoulder 68 of guide sleeve 18 and lower shoulder 78. Spring mechanism 90 can be a ring of polymer, elastomer, or soft ferrous or non-ferrous metals.

[0063] As will be described further herein, sliding bushing 70 can also be reversible within guide sleeve 18. In the reversed position bushing 70 is used without spring 90 and hence becomes a static bushing.

[0064] Spring mechanism 90 provides enough force to compensate for piston pressure to allow sliding bushing 70 to move within the guide sleeve 18.

[0065] Due to components 80 and 90, bushing 70 can slide within guide sleeve 18. Slight vertical axial movement of the replaceable bushing will alter timing events on the up and down strokes providing an increase in pressure to offset leakage.

[0066] In another embodiment, in lieu of gland seal 80, a split ring 98 can be used. Referring to Figs 9 and 10, a split ring 98 can be positioned within indentation 66 of guide sleeve 18. Split ring 98 can be made of a polymer, ferrous or nonferrous metal.

[0067] In another embodiment as shown in Figs. 11 and 12, split ring 98 and sliding wear bushing 70 can be used in conjunction with a spacer ring 100. Spacer ring 100 acts as a retention ring to keep bushing 70 in a static position, i.e, bushing 70 is prevented from sliding. Spacer ring 100 can be an elastomer, polymer, ferrous or non-ferrous material. Additionally, as described above, spacer ring 100 can be coated or treated with secondary heat treatment processes] to increase wear resistance, hardness, lubricity or a combination of all or some.

[0068] As shown in Fig. 11 and 12, sliding bushing 70 can be disposed in guide sleeve 18 in an inverted position from that as shown in Figs. 7 and 8. In other words, lower portion 76 of the bushing is now at the upper side at indentation 66 of guide sleeve 18 and upper portion 78 is now located at the lower side at shoulder 68 of guide sleeve 18. Spacer ring 100 in positioned between split ring 98 and shoulder 74 of bushing 70. [0069] By inverting bushing 70 as described above, the timing point is now static. Inverting also provides a new surface for the timing points as wear occurs during use. When the dynamic bushing is used (either installed new from manufacturing or during repair) and depending on the amount of wear on the piston surfaces it may be desirable to use the dynamic bush in the static position first for a period of operating hours and then flip the bushing into dynamic mode. Flipping the bushing in either direction provides a new wear surface with decreased clearance between piston and bushing.

[0070] Accordingly, sliding wear bushing 70 can be turned into a static bushing by i) inverting/ turning the bushing upside down, and ii) adding spacer ring 100. [0071] Wear area 2 requires sliding protection without additional drag or scraping against the case wall. This is most economically achieved by use of rings fitted to special grooves pre-machined into the piston outer diameter. The rings are specially designed to improve sealing of the worn faces while not increasing drag resistance of the ring to casing wall, which cannot be 100% prevented, decreases power by decreasing velocity of the piston. Multiple rings may be used one a single piston. Ring material may be polymer, ferrous, and non-ferrous.

[0072] However, as set forth above, wear area 2 (WA2) (Fig. IB) also requires sliding protection without additional drag or scraping against the case wall. As will be described further below, this is most economically achieved by use of rings fitted to special grooves pre-machined into the piston outer diameter. The rings are specially designed to improve sealing of the worn faces while not increasing drag resistance of the ring to casing wall, which cannot be 100% prevented, decreases power by decreasing velocity of the piston. Multiple rings may be used one a single piston.

[0073] Referring to Figs. 13-18, a plurality of piston sealing rings 110 are provided to protect the piston 20 from wear in area (WA2) (Fig. IB). Piston sealing rings 110 are located in grooves 104 formed in an outer surface 102 of piston 20. Referring to Fig. 14, piston sealing rings make up the gap between the body of piston 20 and the inner surface of casing 12 to minimize leakage. Piston sealing ring material can be an elastomer, polymer, ferrous, nonferrous materials and may be coated or secondary heat treatment to improve hardness, lubricity, or wear resistance.

[0074] As shown in Fig. 15, piston sealing rings 110 are split for aiding installation during assembly. However, it should be appreciated that the fit of rings 110, piston 20 and casing 12 must be tightly controlled to minimize movement while ensuring a proper outer diameter of the piston. A fitment allowing for slight decreases in the outer diameter of the piston 20, as the inner wall of casing 12 may not have even wear along piston travel, is tolerable, though not preferred.

[0075] Ends 112, 114 of piston sealing ring 110 can be overlapping as shown in Fig. 16. Alternatively, ends 112, 114 can overlap as shown in Figs. 17 and 18. [0076] It is also desirable that piston sealing rings 110 do not exert force on the inner surface of the bore of casing 12, as such may impede piston travel and velocity. The size of piston sealing rings 110 are designed to add sealing diameter to the piston bringing it back to design tolerances.

[0077] As the piston and case wear during use the clearance between the piston outer diameter and case wall 12 will increase and at times may be substantial. It may not be desirable or economical to replace either component in remote locations, lack of inventory, or if tool end of life is expected soon. The rings are designed to predict and fill the amount of clearance that might occur during use. Material selection should be made to balance rigidity, abrasion resistance, and flexibility. The material must be flexible enough to allow installation around the piston and slight movement perpendicular to the piston axis as the piston travels up and down. Commonly purchased off the shelf O-rings are not the correct size to fill the close clearance gap between piston and case plus the elastomer friction coefficient is too high when it contacts the case wall. The standard O-ring also stretches in the installed position and the actual OD of a stretched O-ring will be too large/small depending on the molding tolerance of the O-ring.

[0078] Rings 110 are replaceable with varying cross-sectional size to custom fit the worn piston body as piston wear in service may vary. [0079] Cross-sectional geometry of rings 110 may vary for commonly available materials. Rings have a mainly semi-circular cross section to locate on the piston and remain in place during operation. The flat side of the semi-circle will slide in close proximity to the case wall.

[0080] Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.