There are many different down the hole (DTH) drill hammers available for drilling in mining, civil works and in the construction of water, oil and gas and geothermal wells. These hammers are powered by pressurized fluid that is alternatively directed by different means into a lifting chamber and a drive chamber, which are located at opposite ends of the hammer piston. As one chamber is being filled with pressurized fluid, the other is being emptied and the difference in pressure between the lifting and drive chambers causes the reciprocating movement of the piston and the impact of the same on the drill bit with each working stroke of the piston.
Most of the known DTH drill hammers have only one drive chamber and one lifting chamber. In such cases, the piston has only one drive area and one lifting area. However, for increasing the effective thrust areas (i.e. drive area and lifting area) a number of DTH drill hammers make use of more than two chambers for moving the piston, three examples of which are described below.
U.S. Pat. No. 5,915,483
The normal circulation drill hammer design described in this patent has a centrally-bored piston shaped to provide an additional drive chamber and an additional lifting chamber between the piston and the inner wall of the outer casing of the hammer. These two additional chambers are created by recesses on the outer diameter of the piston and separated by a partition member.
For controlling the flow of pressurized fluid in and out of the chambers, a control rod is provided that extends from the backhead or rear sub of the hammer axially down the central bore of the piston, the control rod having one longitudinally extending supply passage and one longitudinally extending discharge passage. Ports in the control rod and piston respectively connect these passages with the lifting and drive chambers when the ports in the control rod are aligned with the ports in the piston during the reciprocating movement of the latter.
The main drive chamber is continuously connected to the source of pressurized fluid and from there the pressurized fluid is conveyed to the longitudinal supply passage of the control rod for alternately supplying the additional lifting and drive chambers with pressurized fluid, controlled by the relative position of the piston with the control rod.
The discharge of pressurized fluid from the main lifting chamber is controlled by the relative position between the piston and either a foot valve or an extended control rod, while the discharge from the additional lifting and drive chambers is controlled by the relative position of the piston and the control rod.
One disadvantage of this design is that the pressure in the main drive chamber is equal in average to the supply pressure of the working fluid, which means that the work exerted by the pressurized fluid over this region of the piston is null, so that the power of the hammer is negatively affected. Another disadvantage is the cross-sectional area occupied by the control rod, resulting in reduced front and rear thrust areas.
U.S. Pat. No. 5,992,545
This patent describes a normal circulation drill hammer design where the piston comprises a forward piston head, a rearward piston head provided with a main drive area, and a waist between the piston heads. An intermediate wall is arranged around the waist of the piston so that two chambers are formed on each side of the intermediate wall between the piston's waist and front and rear linings disposed in the housing of the hammer. A pin is arranged through the intermediate wall in order to lock the linings in fixed angular positions relative to the intermediate wall.
In between the front and rear linings and the housing there are disposed respective channels. The first of these channels is connected through radial holes in the rear lining with a room rearward of the piston which is continuously connected to the source of pressurized fluid. The second of these channels is connected with a space in the front end of the piston where the forward piston head is located and a main lifting area is defined.
The chamber formed between the forward piston head and the intermediate wall is continuously connected with the channel between the rear lining and the housing via a first channel in the intermediate wall and holes in the rear lining, thus said chamber being continuously filled with pressurized fluid from the source of such fluid. The chamber between the rearward piston head and the intermediate wall is connected via a second channel in the intermediate wall to the channel between the front lining and the housing and therefrom with the space in the front end of the piston.
The supply of pressurized fluid to the room where the main drive area is located, inside the rearward piston head, is controlled by a valve part arranged on a tube that is connected to the hammer string, said tube having holes open to the room. The discharge of said room is controlled by the overlap of the inner surface of the piston with radial holes in said tube, said radial holes conveying the pressurized fluid through the a central channel in the piston to a flushing hole of the drill bit. A foot valve is used for controlling the discharge of the space in the front end of the piston.
The supply of pressurized fluid to the space in the front end of the piston is controlled by the relative position of the outer surface of the piston and the inner surface of the front lining.
Since in this design the chamber formed between the forward piston head and the intermediate wall is continuously connected to the source of pressurized fluid, work exerted by this region of the piston is null.
U.S. Pat. No. 9,016,403
This patent describes a normal circulation drill hammer that has multiple chambers that exert work on a centrally bored piston, specifically one or more auxiliary drive and lifting chambers besides two main chambers located at opposite ends of the piston.
For controlling the supply of pressurized fluid to the chambers, the piston and a control tube coaxially arranged within the central bore of the piston cooperate to channel the pressurized fluid from internal chambers defined by recesses in the inner surfaces of the piston to the auxiliary chambers through ports machined in the piston and to the main chambers through passageways formed at each end of the piston between the control tube and the same piston.
For controlling the discharge of pressurized fluid from the chambers, the piston and a set of cylinders cooperate to channel the pressurized fluid from the drive and lifting chambers to discharge chambers through discharge ports machined in the cylinders.
Despite the drill hammer described in this patent has the advantage of provided multiple drive and lifting chambers, this design has drawbacks. The ports and internal chambers machined in the piston affect its reliability.
Besides, the presence of a control tube reduces the effective thrust area that can be added, makes the piston slender and can cause alignment related problems as excessive friction; all these issues reduce the performance and reliability of the hammer.
The DTH drill hammers of the prior art described above have the drawback that they do not make an efficient use of the space inside the hammer to create additional drive and lifting chambers that actually exert work on the piston. Additionally, the pistons described therein have features that make them unreliable.
Therefore, due to the high costs of operating drilling equipment and the greater depths of the wells needed in some applications such as oil & gas, geothermal energy and minerals exploration, it would be desirable to have a pressurized fluid flow system for a DTH drill hammer that could incorporate the following improvements without affecting the useful life of the hammer:
It would also be desirable that, in terms of control of the state of the lifting and drive chambers, the pressurized fluid flow system of the invention could have application in both normal circulation DTH drill hammers and reverse circulation DTH drill hammers.
In a first aspect of the invention, an improved pressurized fluid flow system for a down the hole drill hammer is provided, characterized by the presence of a plurality of chambers that exert work on the piston, namely, one or more auxiliary drive chambers and one or more auxiliary lifting chambers besides two main chambers located at opposite ends of the piston. These auxiliary chambers are each formed around respective waists machined around the piston and are externally delimited by respective cylinders, including at least one rearmost cylinder and one forwardmost cylinder. The cylinders are arranged longitudinally in series and coaxially disposed in between the outer casing of the hammer and the piston, the cylinders being separated from each other by seals and supported on the outer casing.
The pressurized fluid flow system of the invention is further characterized by having a set of supply chambers defined by annular recesses in the external surface of the piston, all the supply chambers being in fluid communication with the source of pressurized fluid and permanently filled with the same, for supplying the multiple drive and lifting chambers with said fluid.
The supply of pressurized fluid into said chambers is controlled in the invention in a cooperative way by the piston and the cylinders, specifically by the outer sliding surfaces of the piston and the inner surfaces of the cylinders.
A set of pressurized fluid intake ports is provided in the rearmost cylinder for allowing the pressurized fluid coming from said source of pressurized fluid flow into one or more supply channels formed in between the outer casing and the cylinders and to flow from there into the supply chambers through respective sets of exit ports in the cylinders.
In the invention, each of the cylinders has a front set of recesses and a rear set of recesses on its inner surface for connecting the supply chambers with the lifting chambers and with the drive chambers when these must be supplied with pressurized fluid.
The pressurized fluid flow system of the invention is also characterized by having one or more discharge channels formed in between the outer casing and the cylinders, the discharge channels being in fluid communication with the bottom of the hole drilled by the hammer for discharging pressurized fluid from the multiple drive and lifting chambers. For this purpose, sets of rear discharge ports and front discharge ports are provided in the cylinders for connecting the drive and lifting chambers with the discharge channels. In this manner, the discharge of pressurized fluid from the drive and lifting chambers is also controlled in a cooperative way by the piston and the cylinders, specifically by the outer sliding surfaces of the piston and the inner surfaces of the cylinders.
In a second aspect of the invention, a normal circulation DTH drill hammer is provided that is characterized by comprising the improved pressurized fluid flow system herein described and a drill bit guide with one or more apertures that connect the discharge channels with channels formed between the splines of the drill bit, the drill bit having flushing passages which connect these channels between the splines of the drill bit with the bottom of the hole.
To facilitate the understanding of the precedent ideas, the invention is hereinafter described making reference to the attached drawings.
In the drawings:
The pressurized fluid flow system of the invention has been depicted in
Referring to
a cylindrical outer casing (1) having a rear end and a front end;
a driver sub (110), mounted to said front end of the outer casing (1), and having an inner surface (113) with splines (112) machined thereon;
a rear sub (20) affixed to said rear end of the outer casing (1) for connecting the hammer to the source of pressurized fluid;
a piston (60) which is slidably and coaxially disposed to exert a reciprocating movement inside the outer casing (1); and
a drill bit (90) slidably mounted on the driver sub (110), the sliding movement of the drill bit (90) limited by the drill bit retainer (210) and the drill bit supporting face (111) of the driver sub (110), the drill bit (90) comprised of a drill bit shank (95) at the rear end of the drill bit and a drill bit head (96) at the front end of the drill bit, the drill bit head (96) being of bigger diameter than the drill bit shank (95) and having a front face (99), the drill bit shank (95) having an outer surface (98) with splines (93) machined thereon, wherein the drill bit (90) is aligned with the outer casing (1) by means of a drill bit guide (150) disposed inside said outer casing (1).
As shown in these figures, the pressurized fluid flow system of the invention further comprises the following components:
a main lifting chamber (240) and a main drive chamber (230) located at opposites ends of the piston (60) for causing the reciprocating movement of the piston (60) due to the changes in pressure of the pressurized fluid contained therein;
a set of cylinders (40a, 40b, 40c), in this case three cylinders and including at least one rearmost cylinder and one forwardmost cylinder, that are arranged longitudinally in series and are coaxially disposed between the outer casing (1) and the piston (60), the cylinders (40a, 40b, 40c) being supported on the outer casing (1) and separated from each other by seals (290a, 290b), in this case two of them, the cylinders (40a, 40b, 40c) having respectively inner (47a, 47b, 47c) and an outer surfaces (48a, 48b, 48c);
a set of auxiliary lifting chambers (241, 242) and auxiliary drive chambers (231, 232), in this case two of each, respectively located at each side of said seals (290a, 290b) and respectively formed by rear (74a) and front (74b) waists machined around the piston (60), for likewise causing the reciprocating movement of the piston (60) in conjunction with the main lifting and drive chambers (240, 230), due to the changes in pressure of the pressurized fluid contained therein;
a set of supply chambers (68a, 68b, 68c) defined by annular recesses in the external surface (65) of the piston (60) in cooperation with the inner surfaces (47a, 47b, 47c) of the cylinders (40a, 40b, 40c), the supply chambers (68a, 68b, 68c) being in permanent fluid communication with the source of pressurized fluid and filled with the same;
one or more supply channels (2) formed in between the outer casing (1) and the cylinders (40a, 40b, 40c) by a set of recesses in the outer surface of the cylinders (40a, 40b, 40c), the supply channels (2) being in permanent fluid communication with the source of pressurized fluid;
one or more discharge channels (3) formed in between the outer casing (1) and the cylinders (40a, 40b, 40c) by a set of recesses in the outer surface of the cylinders (40a, 40b, 40c), the discharge channels (3) being in permanent fluid communication with the bottom of the hole; and
channels (97) cooperatively formed between the splines (112) on the inner surface (113) of the driver sub (110) and the splines (93) on the outer surface (98) of the drill bit shank (95).
As can be noted, each of the cylinders (40a, 40b, 40c) has respectively, a front set of recesses (45a, 45b, 45c), and a rear set of recesses (46a, 46b, 46c) on its inner surface for respectively connecting the supply chambers (68a, 68b, 68c) with the lifting chambers (241, 242, 240) and with the drive chambers (230, 231, 232) when these must be supplied with pressurized fluid; a set of front discharge ports (44a, 44b, 44c), and a set of rear discharge ports (43a, 43b, 43c) bored therethrough for respectively discharging pressurized fluid from the lifting chambers (241, 242, 240) and drive chambers (230, 231, 232) to the discharge channels (3); a set of exit ports (42a, 42b, 42c) for connecting the supply channels (2) with the supply chambers (68a, 68b, 68c).
The precise boundaries of the different drive and lifting chambers are as follows:
When in the hammer cycle the impact face (61) of the piston (60), which is part of the main lifting surface (63c), is in contact with the impact face (91) of the drill bit (90) and the drill bit (90) is at the rearmost point of its stroke, i.e. the hammer is at impact position (see
This flow of pressurized fluid to the lifting chambers (241, 242, 240) will stop when the piston (60) has traveled in the front end to rear end direction of its stroke until the point where the front outer supply edges (72a, 72b, 72c) of piston (60) respectively reaches the rear limit of the front set of recesses (45a, 45b, 45c) of the cylinders (40a, 40b, 40c). As the movement of the piston (60) continues further in the front end to rear end direction of its stroke, a point will be reached where the front outer discharge edges (73a, 73b, 73c) of the piston (60) will respectively match the front limit of the sets of front discharge ports (44a, 44b, 44c) of the cylinders (40a, 40b, 40c). As the movement of the piston (60) continues even further, the lifting chambers (241, 242, 240) of the hammer will respectively become fluidly communicated with the set of discharge channels (3) through the sets of front discharge ports (44a, 44b, 44c) of the cylinders (40a, 40b, 40c) (see
Normally, the drill bit (90) is aligned to the outer casing (1) of the hammer by a drill bit guide (150) having discharge grooves (151) as shown in the Figures (see particularly
Control of the State of the Drive Chambers (230, 231, 232)
When in the hammer cycle the impact face (61) of the piston (60), which is part of the main lifting surface (63c), is in contact with the impact face (91) of the drill bit (90) and the drill bit (90) is at the rearmost point of its stroke, i.e. the hammer is at impact position (see
This flow of pressurized fluid will stop when the piston (60) has traveled in the front end to rear end direction of its stroke until the rear outer discharge edges (70a, 70b, 70c) of piston (60) reaches respectively the rear limit of the sets of rear discharge ports (43a, 43b, 43c) of the cylinders (40a, 40b, 40c). As the movement of the piston (60) continues further in the front end to rear end direction of its stroke, a point will be reached where the rear outer supply edges (71a, 71b, 71c) of the piston (60) matches respectively the front limit of the rear sets of recesses (46a, 46b, 46c) of the cylinders (40a, 40b, 40c) (see
Flushing Mode Operation
If the hammer is lifted in such a way that the drill bit (90) stops being in contact with the rock being drilled and the drill bit's retainer supporting shoulder (94) rests on the drill bit retainer (210), the drill bit (90) will reach the front end of its stroke and then the hammer switches to its flushing mode. In this position the percussion of the hammer stops, hence leaving the impact face (61) of the piston (60) resting on the impact face (91) of the drill bit (90) (see
Filing Document | Filing Date | Country | Kind |
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PCT/CL2017/050076 | 12/13/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2018/107305 | 6/21/2018 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4583601 | Freres | Jan 1986 | A |
5407021 | Kane | Apr 1995 | A |
5915483 | Gien | Jun 1999 | A |
5992545 | Ekwall | Nov 1999 | A |
8640794 | Aros | Feb 2014 | B2 |
9016403 | Aros | Apr 2015 | B2 |
10316586 | Aros | Jun 2019 | B1 |
20020014354 | Patterson | Feb 2002 | A1 |
20090188723 | Aros | Jul 2009 | A1 |
20100012380 | Swadi | Jan 2010 | A1 |
20110209919 | Aros | Sep 2011 | A1 |
20130233626 | Aros | Sep 2013 | A1 |
20140076638 | Aros | Mar 2014 | A1 |
20150129316 | Harrington et al. | May 2015 | A1 |
20160340983 | Bruandet | Nov 2016 | A1 |
20200190906 | Bruandet | Jun 2020 | A1 |
20200370373 | Aros | Nov 2020 | A1 |
Number | Date | Country |
---|---|---|
2014207163 | Dec 2014 | WO |
Number | Date | Country | |
---|---|---|---|
20200370373 A1 | Nov 2020 | US |