The present disclosure relates to a piston actuated drilling tool, although not exclusively, to percussion tools for downhole drilling.
Piston actuated drilling tools, such as rotary percussion tools (RTP) employ the efficient application of compressed air energy in combination with rotary drilling forces to achieve a high rate of penetration and drilling performance.
Known rotary percussion tools contain a retaining system, for example, in the form of a split retaining ring to prevent the mandrel and the bit from disengaging from the remaining components of the percussion tool, such as the casing.
In some percussion tools there is also a guide bushing provided or a foot valve, to co-operate with the piston nose and regulate the flow around it.
The retaining system and the guide bushing have completely different functions, but are often placed in close proximity to one another, this is shown for example in U.S. Pat. No. 7,757,779 and CN209115038.
The problem with this is that to ensure proper assembly and to maintain their position during operation, it is necessary to very tightly and carefully control the tolerances of the parts, which requires complex machining, which adds further costs and time to achieve the required dimensions.
It is an objective of the present disclosure to provide a novel and improved assembly for a piston actuated drilling tool for down the hole drilling.
The objective is achieved by providing a piston actuated drilling tool including a housing, a top sub, a piston and a drive sub; the piston having a nose at its forward end that is slidably mounted for reciprocating movement within the housing and which strikes a mandrel located at the forward end of the housing; wherein there is an integrated retaining and bushing system that comprises a retaining ring for preventing the mandrel from detaching from the rest of the tool encasing a bushing for co-operation with the piston nose to stabilise and guide the piston and provide a timing event for the percussion.
The integration of the retaining ring and the bushing means that it is not necessary to maintain such tight tolerances to achieve proper assembly and to maintain the correct positioning of the parts during operation, therefore easing and reducing the cost of the manufacturing process. The integration means that there is no longer the need for complex machining of the housing or the retaining rings. Further, the internal air volume is controlled and so the efficiency of the drilling assembly is improved.
Optionally, the retaining ring is split into at least two parts. This makes it easier to replace the bushing as the retaining ring can just be split apart to remove a worn or damaged bushing and then a new bushing of standard geometry can be inserted.
One or more O-rings are used to hold the multiple sections of the retaining ring together. This provides a simple and reliable method of holding the retaining ring together if it has been split into multiple sections. It is important that the retaining ring is securely held together to prevent the leakage of air which would result in a loss of power or misalignment which would result in excessive wear or broken components.
Alternatively, the retaining ring is a one-piece body. If the retaining ring is a one-piece body, it is easier to manufacture.
The retainer ring can be made of a different material than the bushing. Typically, the retaining ring is made of a stronger material compared to the bushing. Advantageously, this adds structural strength to the integrated retaining and bushing system.
The bushing can be made of a polymer, a glass filled polymer, a non-ferrous metal, a heat treated or coated steel. These materials provide a low friction surface, therefore allowing the piston to be able to freely slide in and out of the bushing whilst minimising wear.
Optionally, at a mating surface within the integrated retaining and bushing system, a radially inner surface of the retaining ring and a radially outer surface of the bushing are both cylindrically flat and parallel to one another. Advantageously, this enables ease of construction.
Alternatively, at a mating surface within the integrated retaining and bushing system, a radially inner surface of the retaining ring and a radially outer surface of the bushing each comprise one of at least one notch and at least one protrusion to form a retention lock within the system. Advantageously, the interlocking geometries means that the two parts of the integrated system are securely held together.
Optionally, the top half and the bottom half of the bushing is asymmetrical, so that the same bushing can be inserted into the retaining ring in a first position for normal operation modes and in a second position for altered timing characteristics, wherein the bushing extends further towards the piston nose in the second position compared the first position. Advantageously, the same bushing can be used in either operational position thus making it is easy and convenient to swap between the two modes, without the need to have to have a second different type of bushing available.
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.
The tool further includes an annularly shaped piston 8 moveably positioned within the housing 4. The piston 8, which is typically a cylinder although other configurations could be envisaged, optionally includes an air distributor tube 50 extending substantially centrally therethrough for providing air flow to drive the piston 8 and regulate the timing event. Once the tool 2 is assembled, a top pressure fluid chamber 52 and a bottom pressure fluid chamber 54 are formed within the housing 4.
The drive sub 10 houses one or more annularly shaped drive lugs 24 that are stacked on top of one another and a portion of a mandrel 12. The mandrel 12 is a substantially solid component to which a drill bit (not shown), that is provided with a plurality of inserts which are typically made from tungsten carbide, can be attached to. The mandrel 12 is axially moveable with respect to both the housing 4 and the drive sub 10, a portion of the mandrel 12 being inserted and housed within the housing 4. The top sub 6 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 housing 4, drive sub 10, drive lugs 24, and mandrel 12. For DTH hammers the drive lugs 24 are normally replaced by interlocking splines for the transmission of torque. The drive lugs 10 could also be replaced by low friction drive pins to prevent galling.
As the piston 8 slidably moves upward towards the top sub 6, the volume of the top pressure fluid chamber 52 decreases, while the volume of the bottom pressure fluid chamber 54 increases. Conversely, as the piston 8 slidably moves downward towards the mandrel 12, the volume in the top pressure fluid chamber 52 increases and the volume in the bottom fluid chamber 54 decreases.
The piston 8 is used to deliver a downward force to onto the mandrel 12 when the bottom end of the piston 8 contacts the mandrel 12. The piston 8 is then forced back up and then the cycle continues.
The integrated retaining and bushing system 14 are stacked on top of the drive sub 10 and has a dual function.
It should be appreciated that the bushing 20 described in the present application performs a similar function as an exhauster used in a RPS system or a foot valve used in a DTH drill or the geometry of a valveless DTH hammer.
Firstly, the retaining ring 22 part of the system 14 functions to prevent the mandrel 12 and the bit (not shown) from disengaging from the remaining components of the piston actuated drilling tool 2, such as the housing 4. This is achieved through engagement cooperation between a radial protrusion 28 of the upper end of the mandrel 12 and a shoulder 30 on the lower end of the retaining ring 22. The mandrel 12 slidably engages with the retaining ring 22 part of the system 14. When an upward force is placed onto the bottom of the bit, the mandrel 12 slidably moves toward the top sub 6 such that the top portion of the mandrel 12 and the retaining ring 22 are not adjacent and/or in contact with one another. Conversely, when an upward force is not placed onto the bottom of the bit, the mandrel 12 slidably moves away the top sub 6 such that the top portion of the mandrel 12 and the retaining ring 22 are adjacent and/or in contact with one another.
The retaining ring 22 is optionally split as shown in the
Secondly, the bushing 20, which is used in place of a foot valve, is arranged to co-operate with a nose 26 of the piston 8. A purpose of the bushing 20 is to align the top of the mandrel 12 with the piston nose 26 to help stabilise and guide and provide a timing event for the piston 8. A lower annular volume is formed between the piston 8 and the bushing 20 in the bottom pressure fluid chamber 54. When the piston 8 rises out of the bushing 20, the piston 8 exhausts the volume of air. Further, the bushing 20 acts as a seal to prevent the lower annular volume of air that pushes the piston 8 from escaping. This is important because any loss of air volume would reduce the efficiency of the tool 2. The bushing 20 is typically a one-piece body, i.e. not split. Further, the bushing 20 can be made from a low friction material such as a polymer, a glass filled or reinforced polymer, non-ferrous metal, a heat treated or coated steel.
Optionally, the mating surfaces between a radially inner surface 40 of the retaining ring 22 a radially outer surface 42 of the bushing 20 are both cylindrically flat and parallel to one another. Alternatively (as shown in
It should be appreciated that the piston actuated drilling tool 2 described hereinabove could be a rotary percussion tool wherein a tri-cone bit is attached to the mandrel 12 or it could be a down the hole (DTH) hammer having a fixed face bit. The integrated retaining and bushing system 14 would function in the same way in a rotary percussion tool or a DTH hammer or indeed any other pneumatically or hydraulically operated hammer.
While the forgoing examples are illustrative of the principles in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the present disclosure. Accordingly, it is not intended that the present disclosure be limited, except as by the claims set forth below.
This application claims priority of U.S. Provisional Application No. 63/051,438, filed Jul. 14, 2020, which the entirety thereof is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
4044844 | Harris et al. | Aug 1977 | A |
6062322 | Beccu | May 2000 | A |
7757779 | Jacobsson et al. | Jul 2010 | B2 |
8651202 | Swadi | Feb 2014 | B2 |
20040140131 | Susman | Jul 2004 | A1 |
20050173158 | Jacobsson | Aug 2005 | A1 |
20060000646 | Purcell | Jan 2006 | A1 |
Number | Date | Country |
---|---|---|
209115038 | Jul 2019 | CN |
2012049331 | Apr 2012 | WO |
2019043295 | Mar 2019 | WO |
Number | Date | Country | |
---|---|---|---|
20220018386 A1 | Jan 2022 | US |
Number | Date | Country | |
---|---|---|---|
63051438 | Jul 2020 | US |