CA1071947A - Pneumatic hammer drill - Google Patents
Pneumatic hammer drillInfo
- Publication number
- CA1071947A CA1071947A CA263,063A CA263063A CA1071947A CA 1071947 A CA1071947 A CA 1071947A CA 263063 A CA263063 A CA 263063A CA 1071947 A CA1071947 A CA 1071947A
- Authority
- CA
- Canada
- Prior art keywords
- piston
- casing
- chamber
- length
- valve assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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- Earth Drilling (AREA)
- Percussive Tools And Related Accessories (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The specification describes a piston and a method of reciprocating the piston in the casing of a pneumatic percussion machine. The method involves providing a chamber at or towards each end of the casing, locating a piston in such casing with a piston face operating in each of such chambers, and introducing compressed air alterna-tively into the chambers to cause reciprocation of the piston in the chambers, the compressed air being introduced to one chamber through a duct formed in the piston and exhausted from the other chamber through a passage extending for part of its length between the casing wall and the piston.
ABSTRACT OF THE DISCLOSURE
.... . . _,
The specification describes a piston and a method of reciprocating the piston in the casing of a pneumatic percussion machine. The method involves providing a chamber at or towards each end of the casing, locating a piston in such casing with a piston face operating in each of such chambers, and introducing compressed air alterna-tively into the chambers to cause reciprocation of the piston in the chambers, the compressed air being introduced to one chamber through a duct formed in the piston and exhausted from the other chamber through a passage extending for part of its length between the casing wall and the piston.
ABSTRACT OF THE DISCLOSURE
.... . . _,
Description
~ 0 7 1 9 ~
THIS INVENTION relates to pneumatic percussion machines.
Such machines include, for 'nstance, pneumatic drills, hammers and the like.
Generally, pneumatic percussion machines comprise a hollow steel casing or cylinder in which a piston is adapted to be reciprocated. One end of the cylinder is closed off with a valve assembly through which compressed air is supplied to the piston face while the other end is closed off with a bit assembly.
Various arrangements have been proposed for bringing about reciprocation of the piston in the casin~. One such arrangement is described in the complete specification to our South African patent application no 73/7904.
In the preferred form of the arrangement described in such complete specification there is provided a projecting member which extends from the valve assembly through the hollow steel casing into a bore provided in the piston. Such projecting member includes longitudinally extending two paths, one path being adapted to introduce compressed air from the valve assembly through the piston to a chamber located at or towards the lower end of the piston. The other path extends From a chamber Formed between the top of the piston and the valve assembly, to the bore of the piston, the arrangement being such that For particular positions of the -piston relative to the hollow steel casing, air is discharged from this chamber through the projecting member into the bore of the piston from where it can escape to the atmosphere.
In the case of the abovemented pneumatic percussion machine, there are thereFore two paths that pass through the projecting member, one path being intended for introduci:nn compressed air to one of the charnbers and ~ -the other path being intended for exhausting air from the other chamber 107i9~
....
to the atmosphere. While no difficulty is encountered, from the engineering point of view, in providing a pro~
jec~ing member having two passages, it is believed that by eliminating one of the passages in the projecting member, the cost of manufacturing such pneumatic percussion machine can be lowered.
An object of the present invention is the provision of a pneumatic percussion machine in which the need for two longi~udinally passages in the projecting member is dis-pensed with.
According to the present invention there is provided a pneumatic percussion machine having a hollow casing with ~ valve a~sembly at one end of the casing and a bit assembly at tho other end of the casing. A piston is provided for reciprocation in the casing between a first position in which it is in contact with the bit assembly and a second position in which it is removed from the first position, the piston being stepped along its length. A first chamber is formed between an end of the piston in the valve assembly and a second chamber is formed inwardly from the other end o~ the piston about such stepped portion of the pist~n. A
first fluid supply path is provided through the valve assembly to a first chamber, and a second fluid supply path is provided through the valve assembly to the second chamber, the second fluid supplying path passing for at least a part of its length through the piston. A first fluid discharge path is provided ~rom a first chamber passing for at least part of its length between the wall of the casing and the piston and then for the remainder of its length through the piston~
such fluid discharge path being open in particular posit:ions to the piston along the length of the hollow casing. The
THIS INVENTION relates to pneumatic percussion machines.
Such machines include, for 'nstance, pneumatic drills, hammers and the like.
Generally, pneumatic percussion machines comprise a hollow steel casing or cylinder in which a piston is adapted to be reciprocated. One end of the cylinder is closed off with a valve assembly through which compressed air is supplied to the piston face while the other end is closed off with a bit assembly.
Various arrangements have been proposed for bringing about reciprocation of the piston in the casin~. One such arrangement is described in the complete specification to our South African patent application no 73/7904.
In the preferred form of the arrangement described in such complete specification there is provided a projecting member which extends from the valve assembly through the hollow steel casing into a bore provided in the piston. Such projecting member includes longitudinally extending two paths, one path being adapted to introduce compressed air from the valve assembly through the piston to a chamber located at or towards the lower end of the piston. The other path extends From a chamber Formed between the top of the piston and the valve assembly, to the bore of the piston, the arrangement being such that For particular positions of the -piston relative to the hollow steel casing, air is discharged from this chamber through the projecting member into the bore of the piston from where it can escape to the atmosphere.
In the case of the abovemented pneumatic percussion machine, there are thereFore two paths that pass through the projecting member, one path being intended for introduci:nn compressed air to one of the charnbers and ~ -the other path being intended for exhausting air from the other chamber 107i9~
....
to the atmosphere. While no difficulty is encountered, from the engineering point of view, in providing a pro~
jec~ing member having two passages, it is believed that by eliminating one of the passages in the projecting member, the cost of manufacturing such pneumatic percussion machine can be lowered.
An object of the present invention is the provision of a pneumatic percussion machine in which the need for two longi~udinally passages in the projecting member is dis-pensed with.
According to the present invention there is provided a pneumatic percussion machine having a hollow casing with ~ valve a~sembly at one end of the casing and a bit assembly at tho other end of the casing. A piston is provided for reciprocation in the casing between a first position in which it is in contact with the bit assembly and a second position in which it is removed from the first position, the piston being stepped along its length. A first chamber is formed between an end of the piston in the valve assembly and a second chamber is formed inwardly from the other end o~ the piston about such stepped portion of the pist~n. A
first fluid supply path is provided through the valve assembly to a first chamber, and a second fluid supply path is provided through the valve assembly to the second chamber, the second fluid supplying path passing for at least a part of its length through the piston. A first fluid discharge path is provided ~rom a first chamber passing for at least part of its length between the wall of the casing and the piston and then for the remainder of its length through the piston~
such fluid discharge path being open in particular posit:ions to the piston along the length of the hollow casing. The
-2-cbr~
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arrangement is one in which the valve assembly is adapted, on operation of the machine, to open alternately the fluid supply paths.
In a specific embodiment of the invention the stepped portion of the piston is received in a stem bearing for forming the -second chamber between the step in the piston and ends of the stem bearing corresponding to the step.
Also in a specific embodiment of the.invention, the axial length of the stepped portion of the .piston is such that with the bit assembly projecting in its further most position from the casing, the step of the piston can rest on the corresponding edge of the stem bearing, the axial length of the piston is furthest such that in this position both the fluid supply paths are open to the atmosphere.
_3_ cbr~0 ~` 1~7~9~7 By way of example only, preferred forms of the invention will now be described with reference to the accompanying drawings, in which:-FIGURE 1 is a section through one form of the pneumaticpercussion drill with a bit assembly of such drill in its operative position, and the piston in contact with such -bit assembly;
FIGURE 2 is a section through the axis of the piston of - -Figure l;
FIGURE 3 is a section at right angles to the section o Figure 2 and through the axis oE the piston; and .. , ' ;','.
FIGUR~ 4 is a section through part of a second form of the pneumatic percussion machine.
The pneumatic percussion drill shown in Figures l to 3 comprises a ho~low casing l which is internally tapped at both its extremities. At one end of the casing there is ~ :
fitted a bit assembly. In the form of the invention shown in the accompanying drawings, such bit assembly includes a bit 2, withdrawal of which is prevented by two retaining half rings 3. These half rings are held in position by a threaded chuck 4 that engages in a tapped end portion of ~:
the casing l. The upper end kh~
.. ' ' ~.
~ ~7 ~ 9 4~
of the bit is formed into a suitable striking head 5.
The bit assembly also includes a stem bearing 6, which prov;des a 130 guide for a stepped portion 7 of the piston 8. As will be seen from the accompanying drawings, the stem bearing 6 is stepped to bear against a complementary internal step 9 in the casing as the chuck 4 is tightened.
The other end of the casing 1 is fitted with a back head 10 which engages the casing end in a screw fit. The back head is fitted with a spring-biased check valve 11 located about a projecting stem of the valve chest 12. The check valve 11 is adapted automatically to close off the drill interior during non-operation of the drill.
The casing is stepped internally, at the end thereof fitted with the 140 back head assembly, such step 13 being provided at a point inwardly from the tapped section of the casing end. Against such step 13 there bears a valve seat 14 having two ducts 15 and 16 passing through it The valve seat 14 is fitted with a projecting member 17 which passes through A hole provided in the seat to extend into the confines of the casing. A peripheral flange 18 is provided towards one end of the projecting member so that on tightening the back head 10 in the casing end, the projecting member 17 is held tight by the valve chest 12 - -against the valve seat 14 while the valve seat 14 is pressed firmly against the step 13 of the casing.
.
150 The projecting member 17 comprises a tuhular section, closed at one end, which has a bore that extends from one end thereof along the l;ength ~ 2 ~ ~
1 ~ ~ 1 9 4~
towards the closed end. A hole l9 is drilled through the wall of the projecting member 17 at a position in proximi~y to the inner end of the bore. This hole l9 lines up with the duct 15 in the va1ve seat 14 and provides communication between such duct and the interior of the .
projecting member 17.
The ducts 15,16 in the valve seat are opened alternately by a conventional .
clapper valve arrangement 20 pivotally mounted on an end of the projecting member 17 and constituting, with the valve seat 14, a valve assembly. `
160 The casing is fitted with a piston 8 provided wlth axial bores 22, 23 wh;ch extend inwardly from the end faces of the piston, the length oF
the bores being such that they do not meet. Thepiston has two stepped sections 28,29 which are positioned radially with respect to the bores 22,23 of the piston.
The casing is further stepped at 32 to provide a wider bore in which the piston oscillates. ~`
In Figure l of the accompanying drawings, the piston 8 is shown in contact with the striking heacl 5 of the bit 2. The clapper valve 20 is shown in position with the duct 15 open. In this position of the 170 valve, compressed air passes in through the back head lO into the duct 15, from there into the interior of the projecting member 17. From the projecting member the compressed air passes down the bore 22, duct 27 in the piston 8 and then into the second chamber 30.
As a result, the piston is forced up towards the valve assembly. ~nce the piston has moved sufficiently far for the stepped section 7 of the piston 8 to move out from the stem bearing 6, air escapes from the ., ~
..
~ 9 4 7 second chamber 30 along passages 33 past the bjt assembly to atmosphere~
At this stage, there is a sudden increase in flow of compressed air through the drill causing the clapper valve 20 to flip over and the duct l80 15 to be closed. Compressed air is now introduced throu~h duct 16 into the first chamber 31 as a result of which the piston is forced down towards the bit assembly to a stage where the piston end strikes the striking -head 5 of bit 2. At this point, air in the second chamber is free to pass through the passage formed between the casing l and ~he piston 8 into the duct 26 from where it can escape past the bit assembly to atmosphere. As a result, there is an increase in flow of compressed air through the drill causing the clapper valve to close off duct 16 and for ~ -duct 15 to be opened, thereby feeding air through to the second chamber.
In this way, the reciprocating cycle of the piston is set up.
190 During non-operative periods of the drill, the drill is raised o~F the drill bit to cause the striking head of the drill bit to drop onto the half rings 3. In this position of the drill, the projecting member 17 is withdrawn from the bore of the piston and air can either pass through duct 16 to the first chamber and then through duct 26 and bore 23 to the atmosphere or through duct 15 into the interior of the projecting member and from there to the second chamber from where it passes along duct 27 and bore 22 to the first chamber and then through duct 26 and bore 23 to atmosphere.
A second form of the invention is shown in Figure 4. In this form of the 200 invention the step of the piston does not extend to the extremity of the piston but is in the form of a radially extending recess. This piston operates as described above.
-~ .
,-~'' :
....: :-. ,, ~, .; , .. .. . ~ ~
1 ~ 7 1 94 7 Other forms of the invention exist. The striking head and the bithead may be separate members.
In this latter instance, the striking head and the bit head may interlock releasibly for easy replacement of the bit, The bit head need not therefore form part of the bit assembly. The term !'~it assembly" must therefore be interpretted in the sense in which it may or may not include a bit head. ' 210 The invention incorporates many advanta~es It comprises a min;mum number of working parts, thereby lessening the effect of wear. By '' eliminating the inner sleeve of a sliding valve employed in some conventional machines, a piston oF larger diameter,for the same overall diameter of the machine, can be obtained. This in turn allows ~or a machine having a larger piston face and permits the machine to operate at lower fluid pressure than would normally be the case.
The machine also has the advantage that when it is raised to lift the bit off the work face, the fluid exhaust path is automatically opened' to allow compressed air to escape to the atmosphere and thereby stop 220 reciprocation of the piston in the casing.
By virtue of the increased diameter, and hence, mass of the piston, there is an increase in the intensity of the blow imparted by the piston to the striking head. The impact of the blow is also transmitted directly to the bit head.
At the same time, the extra cost of providing two longitudinally extending passages in the projecting member is done away with 'leadin9 to a reduction in manufacturing costs.
... . . . . ..
, , . . , .. :, , ~0~194~
arrangement is one in which the valve assembly is adapted, on operation of the machine, to open alternately the fluid supply paths.
In a specific embodiment of the invention the stepped portion of the piston is received in a stem bearing for forming the -second chamber between the step in the piston and ends of the stem bearing corresponding to the step.
Also in a specific embodiment of the.invention, the axial length of the stepped portion of the .piston is such that with the bit assembly projecting in its further most position from the casing, the step of the piston can rest on the corresponding edge of the stem bearing, the axial length of the piston is furthest such that in this position both the fluid supply paths are open to the atmosphere.
_3_ cbr~0 ~` 1~7~9~7 By way of example only, preferred forms of the invention will now be described with reference to the accompanying drawings, in which:-FIGURE 1 is a section through one form of the pneumaticpercussion drill with a bit assembly of such drill in its operative position, and the piston in contact with such -bit assembly;
FIGURE 2 is a section through the axis of the piston of - -Figure l;
FIGURE 3 is a section at right angles to the section o Figure 2 and through the axis oE the piston; and .. , ' ;','.
FIGUR~ 4 is a section through part of a second form of the pneumatic percussion machine.
The pneumatic percussion drill shown in Figures l to 3 comprises a ho~low casing l which is internally tapped at both its extremities. At one end of the casing there is ~ :
fitted a bit assembly. In the form of the invention shown in the accompanying drawings, such bit assembly includes a bit 2, withdrawal of which is prevented by two retaining half rings 3. These half rings are held in position by a threaded chuck 4 that engages in a tapped end portion of ~:
the casing l. The upper end kh~
.. ' ' ~.
~ ~7 ~ 9 4~
of the bit is formed into a suitable striking head 5.
The bit assembly also includes a stem bearing 6, which prov;des a 130 guide for a stepped portion 7 of the piston 8. As will be seen from the accompanying drawings, the stem bearing 6 is stepped to bear against a complementary internal step 9 in the casing as the chuck 4 is tightened.
The other end of the casing 1 is fitted with a back head 10 which engages the casing end in a screw fit. The back head is fitted with a spring-biased check valve 11 located about a projecting stem of the valve chest 12. The check valve 11 is adapted automatically to close off the drill interior during non-operation of the drill.
The casing is stepped internally, at the end thereof fitted with the 140 back head assembly, such step 13 being provided at a point inwardly from the tapped section of the casing end. Against such step 13 there bears a valve seat 14 having two ducts 15 and 16 passing through it The valve seat 14 is fitted with a projecting member 17 which passes through A hole provided in the seat to extend into the confines of the casing. A peripheral flange 18 is provided towards one end of the projecting member so that on tightening the back head 10 in the casing end, the projecting member 17 is held tight by the valve chest 12 - -against the valve seat 14 while the valve seat 14 is pressed firmly against the step 13 of the casing.
.
150 The projecting member 17 comprises a tuhular section, closed at one end, which has a bore that extends from one end thereof along the l;ength ~ 2 ~ ~
1 ~ ~ 1 9 4~
towards the closed end. A hole l9 is drilled through the wall of the projecting member 17 at a position in proximi~y to the inner end of the bore. This hole l9 lines up with the duct 15 in the va1ve seat 14 and provides communication between such duct and the interior of the .
projecting member 17.
The ducts 15,16 in the valve seat are opened alternately by a conventional .
clapper valve arrangement 20 pivotally mounted on an end of the projecting member 17 and constituting, with the valve seat 14, a valve assembly. `
160 The casing is fitted with a piston 8 provided wlth axial bores 22, 23 wh;ch extend inwardly from the end faces of the piston, the length oF
the bores being such that they do not meet. Thepiston has two stepped sections 28,29 which are positioned radially with respect to the bores 22,23 of the piston.
The casing is further stepped at 32 to provide a wider bore in which the piston oscillates. ~`
In Figure l of the accompanying drawings, the piston 8 is shown in contact with the striking heacl 5 of the bit 2. The clapper valve 20 is shown in position with the duct 15 open. In this position of the 170 valve, compressed air passes in through the back head lO into the duct 15, from there into the interior of the projecting member 17. From the projecting member the compressed air passes down the bore 22, duct 27 in the piston 8 and then into the second chamber 30.
As a result, the piston is forced up towards the valve assembly. ~nce the piston has moved sufficiently far for the stepped section 7 of the piston 8 to move out from the stem bearing 6, air escapes from the ., ~
..
~ 9 4 7 second chamber 30 along passages 33 past the bjt assembly to atmosphere~
At this stage, there is a sudden increase in flow of compressed air through the drill causing the clapper valve 20 to flip over and the duct l80 15 to be closed. Compressed air is now introduced throu~h duct 16 into the first chamber 31 as a result of which the piston is forced down towards the bit assembly to a stage where the piston end strikes the striking -head 5 of bit 2. At this point, air in the second chamber is free to pass through the passage formed between the casing l and ~he piston 8 into the duct 26 from where it can escape past the bit assembly to atmosphere. As a result, there is an increase in flow of compressed air through the drill causing the clapper valve to close off duct 16 and for ~ -duct 15 to be opened, thereby feeding air through to the second chamber.
In this way, the reciprocating cycle of the piston is set up.
190 During non-operative periods of the drill, the drill is raised o~F the drill bit to cause the striking head of the drill bit to drop onto the half rings 3. In this position of the drill, the projecting member 17 is withdrawn from the bore of the piston and air can either pass through duct 16 to the first chamber and then through duct 26 and bore 23 to the atmosphere or through duct 15 into the interior of the projecting member and from there to the second chamber from where it passes along duct 27 and bore 22 to the first chamber and then through duct 26 and bore 23 to atmosphere.
A second form of the invention is shown in Figure 4. In this form of the 200 invention the step of the piston does not extend to the extremity of the piston but is in the form of a radially extending recess. This piston operates as described above.
-~ .
,-~'' :
....: :-. ,, ~, .; , .. .. . ~ ~
1 ~ 7 1 94 7 Other forms of the invention exist. The striking head and the bithead may be separate members.
In this latter instance, the striking head and the bit head may interlock releasibly for easy replacement of the bit, The bit head need not therefore form part of the bit assembly. The term !'~it assembly" must therefore be interpretted in the sense in which it may or may not include a bit head. ' 210 The invention incorporates many advanta~es It comprises a min;mum number of working parts, thereby lessening the effect of wear. By '' eliminating the inner sleeve of a sliding valve employed in some conventional machines, a piston oF larger diameter,for the same overall diameter of the machine, can be obtained. This in turn allows ~or a machine having a larger piston face and permits the machine to operate at lower fluid pressure than would normally be the case.
The machine also has the advantage that when it is raised to lift the bit off the work face, the fluid exhaust path is automatically opened' to allow compressed air to escape to the atmosphere and thereby stop 220 reciprocation of the piston in the casing.
By virtue of the increased diameter, and hence, mass of the piston, there is an increase in the intensity of the blow imparted by the piston to the striking head. The impact of the blow is also transmitted directly to the bit head.
At the same time, the extra cost of providing two longitudinally extending passages in the projecting member is done away with 'leadin9 to a reduction in manufacturing costs.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A pneumatic percussion machine including:
a hollow casing:
a valve assembly at one end of the casing;
a bit assembly at the other end of the casing;
a piston for reciprocation in the casing between a first position in which it is in contact with the bit assembly and a second position in which it is removed from such first position, the piston being stepped along its length;
a first chamber formed between an end of the piston and the valve assembly;
a second chamber formed inwardly from the other end of the piston about such stepped portion of the piston;
a first fluid supply path through the valve assembly to the first chamber;
a second fluid supply path through the valve assembly to the second chamber, such second fluid supply path passing, for at least part of its length through the piston;
a first fluid discharge path from the first chamber passing for at least part of its length between the wall of the casing and the piston and then for the remainder of its length through the piston, such fluid discharge path being open in particular positions of the piston along the length of the hollow casing;
the arrangement being one in which the valve assembly is adapted, on operation of the machine, to open alternately the fluid supply paths.
a hollow casing:
a valve assembly at one end of the casing;
a bit assembly at the other end of the casing;
a piston for reciprocation in the casing between a first position in which it is in contact with the bit assembly and a second position in which it is removed from such first position, the piston being stepped along its length;
a first chamber formed between an end of the piston and the valve assembly;
a second chamber formed inwardly from the other end of the piston about such stepped portion of the piston;
a first fluid supply path through the valve assembly to the first chamber;
a second fluid supply path through the valve assembly to the second chamber, such second fluid supply path passing, for at least part of its length through the piston;
a first fluid discharge path from the first chamber passing for at least part of its length between the wall of the casing and the piston and then for the remainder of its length through the piston, such fluid discharge path being open in particular positions of the piston along the length of the hollow casing;
the arrangement being one in which the valve assembly is adapted, on operation of the machine, to open alternately the fluid supply paths.
2. A pneumatic percussion machine as claimed in claim 1 in which the stepped portion of the piston is received in a stem bearing for forming the second chamber between the step in the piston and ends of the stem bearing corre-ponding to the said step.
3. A pneumatic percussion machine as claimed in claim 2 in which the axial length of the stepped portion of the piston is such that with the bit assembly projecting in its furthermost position from the casing, the step of piston can rest on the corresponding edge of the stem bearing, the axial length of the piston further being such that in this position both the fluid supply paths are open to the atmosphere.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,063A CA1071947A (en) | 1976-10-08 | 1976-10-08 | Pneumatic hammer drill |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,063A CA1071947A (en) | 1976-10-08 | 1976-10-08 | Pneumatic hammer drill |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071947A true CA1071947A (en) | 1980-02-19 |
Family
ID=4107030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA263,063A Expired CA1071947A (en) | 1976-10-08 | 1976-10-08 | Pneumatic hammer drill |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1071947A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103998706A (en) * | 2011-08-19 | 2014-08-20 | 翰美吉公司 | High frequency fluid driven drill hammer percussion drilling in hard formations |
-
1976
- 1976-10-08 CA CA263,063A patent/CA1071947A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103998706A (en) * | 2011-08-19 | 2014-08-20 | 翰美吉公司 | High frequency fluid driven drill hammer percussion drilling in hard formations |
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