U.S. patent number 3,763,939 [Application Number 05/194,300] was granted by the patent office on 1973-10-09 for reversible impact device for driving holes in earth.
Invention is credited to Konstantin Stepanovich Gurkov, Vladimir Vasilievich Klimashko, Alexander Dmitrievich Kostylev, Vladimir Dmitrievich Plavskikh, Boris Vasileivich Sudnishnikov, Konstantin Konstantinovich Tupitsyn.
United States Patent |
3,763,939 |
Sudnishnikov , et
al. |
October 9, 1973 |
REVERSIBLE IMPACT DEVICE FOR DRIVING HOLES IN EARTH
Abstract
A pneumatically operated impact action self-propelled reversible
device for driving holes in the earth by compacting the soil around
the hole being made includes a housing having a pointed driving end
portion and a rear end portion. The impact member is reciprocated
interiorly of the housing in operation of the mechanism under the
action of compressed air to deliver successive impacts upon the
housing. An air distributing mechanism including an air supply
sleeve associated with the impact member and connected with an air
conduit member is provided to control the supply of air to front
and rear working chambers within the housing.
Inventors: |
Sudnishnikov; Boris Vasileivich
(Novosibirsk, SU), Kostylev; Alexander Dmitrievich
(Novosibirsk, SU), Gurkov; Konstantin Stepanovich
(Novosibirsk, SU), Tupitsyn; Konstantin
Konstantinovich (Novosibirsk, SU), Klimashko;
Vladimir Vasilievich (Novosibirsk, SU), Plavskikh;
Vladimir Dmitrievich (Novosibirsk, SU) |
Family
ID: |
26731596 |
Appl.
No.: |
05/194,300 |
Filed: |
November 1, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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12208 |
Feb 19, 1970 |
|
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53216 |
Jul 8, 1970 |
3651874 |
Mar 28, 1972 |
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Current U.S.
Class: |
173/91;
173/135 |
Current CPC
Class: |
E21B
4/145 (20130101) |
Current International
Class: |
E21B
4/14 (20060101); E21B 4/00 (20060101); E21b
001/08 () |
Field of
Search: |
;173/91,92,135
;175/19 |
References Cited
[Referenced By]
U.S. Patent Documents
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3137483 |
June 1964 |
Zinkiewicz |
3407884 |
October 1968 |
Zygmunt et al. |
3410354 |
November 1968 |
Sudnishnikov et al. |
3465834 |
September 1969 |
Southworth, Jr. |
3474873 |
October 1969 |
Zygmunt |
3616865 |
November 1971 |
Sudnishnikov et al. |
|
Primary Examiner: Leppink; James A.
Parent Case Text
This application is a continuation-in-part of our co-pending U. S.
Pat. application Ser. No. 12,208, entitled PNEUMATIC PERCUSSION
DEVICE FOR MAKING HOLES IN THE GROUND BY PACKING THE LATTER, filed
Feb. 19, 1970, and our co-pending U. S. Pat. application Ser. No.
53,216, entitled PNEUMATICALLY OPERATED IMPACT-ACTION
SELF-PROPELLED REVERSIBLE MECHANISM, filed July 8, 1970 now U. S.
Pat. No. 3,651,874 dated Mar. 28, 1972.
Claims
We claim:
1. A pneumatically operated impact-action self-propelled device for
driving holes in the earth, comprising:
a housing having a driving end portion and a rear end portion;
an impact member mounted for reciprocation within said housing and
defining therewith working chambers of variable volume, said impact
member adapted to reciprocate and deliver impacts to one of the
ends of said housing during a distribution of compressed air to
said working chambers;
air supply means rotatably mounted and threadably connected to said
housing for longitudinal movement therein, said longitudinal
movement adapted to effect a modification in the distribution of
compressed air to said working chambers and thereby change the
delivery of impacts to the other end of said housing; and air
delivering passages connecting said air supply means to said
working chambers of variable volume.
2. In a pneumatically operated impact-action self-propelled device
for driving holes in the earth having a housing with a driving end
portion and a rear end portion, an impact member adapted for
reciprocation within the interior of said housing for deliverying
impacts at one end thereof during operation of the device and
defining there with working chambers of variable volume, air
delivering passages connecting said working chambers of variable
volume to air conduit means; wherein the improvement comprises:
air distribution means adapted to modify the distribution pattern
of compressed air to said working chambers and thereby change the
delivery of impacts at one end of said housing to said other end,
said air distribution means including an air supply sleeve fixedly
secured to said air conduit means to prevent relative rotational
movement therebetween, said air supply sleeve cooperating with said
impact member to supply reciprocation of said impact member, the
distribution pattern of compressed air depending on the relative
positions of said impact member and said air supply sleeve, said
air supply sleeve being rotatably and threadably mounted to said
housing for axial displacement therein whereby the position of said
air supply sleeve with respect to said impact member can be changed
by rotating said air conduit means at a remote position from said
housing.
3. A pneumatically operated impact-action self-propelled reversible
device for driving holes in the earth, comprising:
a housing having a generally pointed driving end portion, and a
rear end portion;
an impact member adapted for reciprocation interiorly of said
housing and defining therewith working chambers of variable volume,
said impact member delivering upon said housing repeating impacts,
as said impact member is reciprocated there-inside in operation of
said device;
air conduit means;
a sleeve connected with said air conduit means in a manner to
prevent a relative rotational movement therebetween, said sleeve
cooperating with said impact member and being adapted to supply
compressed air into said chambers for effecting reciprocation of
said impact member;
passage means in said impact member for communication of air to
certain of said chambers, the opening and closing of said passage
means determining a forward or rearward direction of movement of
the device and depending on the relative positions of said impact
member and said sleeve;
said compressed air supply sleeve being threadably secured to said
housing proximate said rear end portion for axial displacement
within said housing when said air conduit means is rotated whereby
the position of said sleeve with respect to said impact member can
be changed to effect a reversal in the direction of the mechanism.
Description
The present invention relates to a pneumatically operated
impact-action self-propelled device for driving holes in the earth
by compacting the soil around the hole being made and more
particularly relates a device of this type which is reversible.
These impact devices, as shown in the above mentioned U. S. Pat.
applications, and U. S. Pat. No. 3,410,354, entitled IMPACT DEVICE
FOR DRIVING HORIZONTAL HOLES IN SOFT GROUND, issued Nov. 12, 1968,
are particularly useful for the trenchless laying of underground
communication conduits. Typically such devices comprise a housing
with a pointed driving end which receives thereinside a movable
impact member. The interior of the housing is divided by the impact
member into front and rear working chambers to which compressed air
is supplied by an air distributing mechanism. The impact member is
reciprocated in the housing under the action of the compressed air
supplied into the abovementioned working chambers and delivers
successive impacts upon the housing. The impacts imparted by the
impact member on the housing propel the device along a course in
the earth to produce the desired hole.
Often it is desirable to extract the mechanism from the hole it has
already made back to the surface, such is the case when the
mechanism meets along its course an insurmountable obstacle, such
as a boulder or the remnants of a foundation, or when the mechanism
has completed its course and driven a blind hole of a particular
length. Therefore, it is a primary object of the present invention
to provide a pneumatically operated impact-action self-propelled
device for driving holes in the earth which is reversible.
It is a further object of this invention to provide a pneumatically
operated impact device of the type hereinbefore described having a
novel air distributing mechanism which controls the supply of
compressed air to the working chambers of the device and thereby
effects a particular direction of movement of the device in the
earth.
In accordance with these and other objects, the present invention
is directed to a pneumatically operated impact-action
self-propelled mechanism of the type described above including a
novel air distributing mechanism. In the present invention the air
distributing mechanism briefly comprises an air supply sleeve
threadably connected to a rear end portion of the housing for axial
displacement therein and cooperating with passages or ports in a
shank portion of the impact member for control of the supply of
compressed air to the working chambers. The air supply sleeve is
secured to the air supply hose and rotates therewith. Rotation of
the air supply hose thereby causes the air supply sleeve to be
displaced axially within said housing which in turn changes the
relative positions of the sleeve and the passages. This change
leads to a change in the pattern of the operative distribution of
the compressed air between the abovementioned working chambers of
the mechanism and, therefore, to a reverse of the direction of the
impact delivered by the impact member, and, hence to a reverse of
the direction of movement of the device as a whole.
It is a further object of this invention to provide a simple but
effective means for reversing the driving direction of the
self-propelled device.
These and other objects and advantages of this invention will be
made readily apparent by the following detailed description and the
accompanying drawings, wherein:
FIG. 1 is a schematic sectional side view of a pneumatically
operated impact-action self-propelled device having an air
distributing mechanism for accomplishing a reversal in the
direction of movement of the device in accordance with the present
invention;
FIG. 2 shows a pneumatically operated impact-action self-propelled
device with an alternative form of air distributing mechanism
having the proposed reversing means and illustrating the position
of the impact member prior to the beginning of its forward stroke
during a forward advance of the device;
FIG. 3 is identical to FIG. 2 except the impact member is shown in
the position prior to its rearward stroke;
FIG. 4 is identical to FIGS. 2 and 3 except the impact member is
shown in the position of delivering an impact upon the rear end
portion of the housing during a retreat of the device;
FIG. 5 shows another alternative embodiment of the pneumatically
operated impact-action self-propelled device having the proposed
reversing means;
FIG. 6 is an exploded view illustrating the reversing means of the
air distributing mechanism of FIG. 5.
Referring now in detail to the drawings and in particular to FIG.
1, there is disposed inside a hollow cylindrical housing 10 an
impact member 12 engaging the internal cylindrical wall of the
housing by a pair of annular projections 14 and 16,
respectively.
The space inside the housing 10 defined by the internal surface of
the housing and by the external surface of the impact member 12
constitutes a front working chamber 18. Formed within the rear or
shank portion of the impact member 12 is a space 20 which
constitutes the rear working chamber of the herein disclosed
device. The wall of the impact member 12 has made therein passages
or ports 24 for fluid communication between the chambers 18 and
20.
The air distribution mechanism, generally designated 21, controls
the supply of compressed air to the working chambers 18 and 20 and
includes a compressed air supply sleeve 22, the head or greater
diameter portion being received by the space 20. The compressed air
supply sleeve 22 has its stem (that is the smaller diameter
portion) provided with annular abutments 26 and 28, this stem being
threadably secured in the threaded passage of a nut 30, the forward
face of which forms an end wall 31. This nut 30 in turn is
threadably secured to the housing 10 by means of the external
cylindrical thread of the nut 30 engaging the internal thread of
the housing 10. The nut 30 is provided with outlet passages 32 for
exhaust of air there-through. The rear end portion of the
compressed air supply sleeve 22 non-rotatively receives thereabout
the end portion of an air supply conduit or hose 34.
When the compressed air is supplied from an appropriate source (not
shown) into the supply hose 34, the compressed air finds it way
through the axial passage 36 and the sleeve 22 into the rear
working chamber 20, whereby the impact member (of which the
communication passages are in this position cut off the rear
chamber 20 by the head of the sleeve 22) is driven forward into the
chamber 18 inside the housing 10 and strikes the latter in the
forward direction, and thus the housing 10 is driven forward
relative to the sleeve 7.
When the impact member 12 thus moves toward its extreme forward
position, that is, the position in which it strikes the housing 10,
at a certain point immediately preceding this position (the point
being defined by the disposition of the communication ports or
passages 24 in the body of the impact member 12) the communication
passages 24 establish communication between the front working
chamber 18 and the compressed air source through the chamber 20,
the passage 36 and the hose 34.
The rebound of the impact member 12 together with the action of the
compressed air in the front chamber 18 are responsible for the
return stroke of the impact member 12 in the rearward direction. In
this return stroke the working surface of the impact member 12
subjected to the action of the compressed air in the front chamber
18 is greater than the working surface of the same impact member
subjected to the action of the compressed air in the rear chamber
20 which is continuously communicating with the source of the
compressed air.
During the return stroke of the impact member 12, the communication
passages or ports 24 at a certain point become closed by the
cylindrical external wall of the head portion of the sleeve 22, but
the continuing pressure inside the chamber 18 and the momentum
gained by the impact member 12 make the latter move on against the
action of the pressure of the compressed air in the chamber 20.
During the return stroke of the impact member 12 the volume of the
chamber 18 expands.
The end of the return stroke of the impact member 12 is defined by
the communication passages or ports 24 thereof passing in the
rearward direction beyond the head portion of the compressed air
supply sleeve 22, whereby there is established communication
between the front chamber 18 and the ambient atmosphere through the
exhaust passages 32 in the end wall 30. In this manner the used up
compressed air is exhausted. If the supply of compressed air into
the supply hose 34 is continued, the above described operating
cycle repeats itself.
The reaction force produced by the return stroke of the impact
member 12 in operation of the herein disclosed device, which acts
upon the housing 10 in the direction opposite to the desired
direction of the progress of the latter, is taken up, or
counterbalanced by the friction between the housing 10 and the
surrounding earth, brought about by the resilient properties of the
earth.
When the herein disclosed device encounters an insurmountable
obstacle (a boulder, the remnants of a foundation, etc.) or when a
blind hole of a desired length has been made, the direction of
movement of the device can be reversed to permit the device to
retreat under the action of the compressed air back to the surface
along the hole or course it has already made. In order to reverse
the direction of movement of the device, the compressed air supply
hose 34 is temporarily disconnected from the compressed air source
(not shown) and is rotated to transmit the torque to the air supply
sleeve 22 of the air distribution mechanism 21 with which the hose
34 is connected non-rotatively. In this manner the sleeve 22 is
rotated in the unscrewing direction, that is, is unscrewed from the
nut 30 into the rearmost position of the sleeve 22, in which the
abutment 26 thereof engages the face of the rear end wall 31. This
changes the relative positions of the sleeve 22 and the ports 24
during operation of the device.
With the compressed air supply sleeve 22 being set in the last
mentioned position, the supply of the compressed air to the working
chamber 18 during the forward stroke of the impact member occurs
earlier and its forward stroke is thereby stopped by the pressure
of the compressed air in the front chamber 18 before it reaches the
internal front end wall of the housing 10, and thus delivers no
impact upon the housing 10 in the forward direction. Moreover, the
now increased initial volume of the front chamber 18 and the
rearmost position of the head of the sleeve 22 are responsible for
the impact member 12 reaching the front face of the rear end wall
31 during the return stroke thereof and thus delivering a
rearwardly directed blow upon the end wall. These repeated impacts
of the impact member 12 upon the end wall 31 drive the entire
device for the retreating motion.
The reaction force produced by the forward strokes of the impact
member 12 and acting upon the housing 10 in the direction opposing
its retreating motion is taken up or counter-balanced (as it has
been already described in connection with the forward motion of the
device) by the friction between the earth and the housing 10.
Referring now to FIGS. 2 through 4, there is shown a pneumatically
operated impact-action self-propelled mechanism similar to the
mechanism of FIG. 1 in many respects but provided with a different
air distributing mechanism. In FIGS. 2 through 4, there is shown a
cylindrical housing 40 pointed in its front portion, accommodating
a striker or impact member 42 which divides the inside of the
housing 40 into front, 44, and rear, 46, working chambers to which
compressed air is intermittently supplied for imparting
reciprocation to the impact member 42 which is delivering impacts
upon the housing 40.
The impact member 42 in its rear or shank portion has space 48 open
from the butt end side, a space 50 of smaller diameter and radial
openings or passages 52, while in the shank portion of the housing
40 is secured an air supply sleeve 54 connected to an air supply
hose 56. During the movement of the striker or impact member 42,
its radial openings or passages 52 are intermittently overlapped by
the sleeve 54 entering the space 50, whereby intermittent air
supply is attained to the front 44 and rear 46 chambers.
In the side wall of the sleeve 54 provision is made for an aperture
58 serving to connect the rear chamber 46 with an air conduit 60 of
the sleeve 54. This latter aperture can only be overlapped during
the movement of the impact member 42 toward the front chamber 44 by
an outer sleeve or cover member 62 mounted outside the air supply
sleeve 54 and connected with the impact member 42 so as to be
movable with respect to the impact member and air supply sleeve
54.
To this end, the outer sleeve 62 is provided with two ribs 64 and
66 spaced from each other, between which there is arranged a pin 68
of the impact member 42, said pin alternately cooperating with the
ribs 64 and 66 during the reciprocation of the impact member,
whereby the sleeve 62 is caused to move and close or open the
aperture 58.
Thus, the air supply sleeve 54, the outer sleeve 62, the openings
or passages 52 and the aperture 58, when taken in combination, form
the air distributing mechanism. Because of the provision of the
aperture 58, compressed air acts through the total cross-sectional
area of the impact member 42 from the side of the rear chamber 46,
which results in an increase of the percussion energy of the impact
member during the forward stroke.
According to the embodiment of this form of the invention shown in
FIGS. 2 through 4, the abovementioned air supply sleeve 54 is
provided with a channel 70 for removal of exhaust air to the
atmosphere and alternately communicating, during the movement of
the impact member 42, with the chambers 44 and 46 via exhaust hole
72 provided in the air supply sleeve 54.
As seen from FIGS. 2 and 4, the skin portion of air supply sleeve
54 includes abutments 71 and 73 and is secured in the shank or rear
end portion of the housing 40 by means of a nut 74, the forward
face of which forms an interior rear end wall 75, relative to which
it can be moved along thread 76. By moving the air supply sleeve 54
relative the nut 74 until the abutment 71 contacts the rear end
wall 75 and thereby displacing the air supply sleeve 54 axially
within the housing 40, the relative positions of the passages and
the air supply sleeve will change during operation of the device
and the moment of air supply to the working chamber 44 will occur
sooner during the forward stroke of the impact member so that the
impact member 42 will strike against the rear end wall thereby
causing the retreat of the mechanism.
Presented herein below is a description of the principles of
operation of the proposed device during the forward and reverse
strokes. Considering first the forward stroke of the device from
the moment the impact member 42 and the sleeve 62 are in the
extreme rear position, the aperture 58 of the air supply sleeve 54
is open, and the openings or passages 52 of the impact member 42
are overlapped by the air supply sleeve 54 as shown in FIG. 2.
The chamber 44 is communicated with the atmosphere via the openings
52 of the impact member 42, exhaust hole 72 in the air supply
sleeve and the air discharge channel 70 of the latter. Under the
action of compressed air supplied via the conduit 60 into the
spaces 48 and 50 of the impact member 42 and through the aperture
58 into the chamber 46, the impact member 42 moves forward. When so
doing, the pin 68 of the impact member 42 acts upon the rib 64 of
the sleeve 62, displacing the latter along the air supply sleeve 54
so as to overlap the aperture 58, thereby ceasing the supply of air
into the chamber 46. Further advance of the impact member 42 takes
place under the effect of air expanded in the chamber 46. At the
end of the stroke the impact member 42 delivers an impact upon the
front portion of the housing 40, causing the latter to intrude into
the ground.
Almost simultaneously with the impact, the exhaust hole 72 gets
connected with the space 48 of the impact member 42, as shown in
FIG. 3, as a result of which exhausted air is discharged into the
air from the chamber 46 via the channel 70 of the air supply sleeve
54, while the openings 52 get opened, and compressed air from the
space 50 enters the chamber 44, causing a rearward movement of the
impact member 42.
The sleeve 62 remains in the extreme front position, that is, the
aperture 58 is overlapped by this sleeve. During further movement
of the impact member 42 its openings 52 are overlapped by the air
supply sleeve 54 entering the space 50, and the supply of air to
the chamber 44 is ceased. The impact member 42 moves on owning to
the energy of air expanding in the chamber 44.
As soon as the openings 52 of the impact member 42 coincide with
the exhaust hole 72, there takes place the discharge of exhausted
air to the atmosphere from the chamber 44 via the channel 70 of the
air supply sleeve 54. The striker or impact member 42 moving on by
inertia, acts with its pin 68 upon the rib 66 of the sleeve 62
which displaces to its initial position leaving the aperture 58
open for the subsequent air intake to the chamber 46. Thereupon,
the cycle is repeated.
In order to switch the device over to the reverse stroke, the air
supply sleeve 54 is displaced axially within the housing from a
front to a rear position, both positions being determined by the
abutments 71 and 73, by turning the air conduit or hose 56 until
the air supply sleeve is screwed into the nut 74 up to where the
abutment 71 engages the end wall 75, as shown in FIG. 4.
With the new position of the air supply sleeve, the openings 52 of
the impact member 42 during the latter's advance will open earlier
and, consequently, the intake of compressed air to the chamber 44
will take place earlier, therefore, the striker or impact member 42
will brake without having struck against the front portion of the
housing 40 and will start moving in the opposite direction. During
this latter movement of the impact member 42, the exhaust hole 72
and the aperture 58 will open later, that is, the exhaust of
exhaust air from the chamber 44 and the intake of compressed air to
the chamber 46 will take place later, and the impact member 42,
having no time for braking, will deliver an impact upon the rear
end wall 75, as a result of which the housing 40 of the device will
move in the opposite direction.
FIGS. 5 and 6 disclose a still further embodiment of a pneumatic
percussion device having an air distribution mechanism with
reversible means in accordance with the present invention.
Referring to these figures, the hollow cylindrical housing 80 of
the herein disclosed mechanism has a generally pointed,
replaceable, driving forward end 82 and receives therein an axially
reciprocable impact member 84 engaging the internal cylindrical
wall of the housing 80 with an interrupted annular shoulder 86 and
a continuous annular shoulder 88. The space defined by the internal
wall of the housing 80 and the external surface of the impact
member 84 constitutes a front working chamber 90. The rear of shank
portion of the impact member 84 has formed there in a cavity 92
which constitutes the rear working chamber of the herein disclosed
device, responsible for forward displacement of the impact member
84 during operation of the device. Passages or ports 96 are made
through the cylindrical wall of the impact member 84, in the area
of the rear cavity 92 therein, these passages or ports establishing
communication between the chambers 90 and 92.
The air distribution mechanism, generally designated 91, controls
the supply of compressed air to the working chambers and includes
an air supply sleeve 94, the head portion of which is received by
the cavity 92. The sleeve 94, which is of a stepped diameter, is
supported along its reduced diameter portion or stem inside a nut
assembly 100 at the rear end portion of the housing 80. The nut
assembly 100 is integrally molded together and comprises an outer
sleeve 101 with external threads 102, and inner sleeve 103 with
internal threads 104, and a shock-damping bush 105 molded
therebetween. The bush 105 is made of an elastically deformable
material and includes a plurality of passageways extending
longitudinally the length thereof thorugh which the used air can be
exhausted into the atmosphere.
The nut assembly 101 is secured by the external thread 102 to the
housing 80 of which the corresponding portion of the internal wall
is provided with a matching internal thread. The sleeve 94 is
secured to the internal threads 104 for axial displacement within
the housing 80. Movement of the sleeve 94 between a forward and
rear position is determined by the stop or abutment 106 on one side
of the nut assembly 100 and the stop or abutment 107 on the other
side of the nut assembly 100. The stop 107 is formed by a clamp
member 108 which non-rotatably secures the rear end portion or stem
portion of the sleeve 94 to the end portion of an air supply hose
110. A flapper valve member 111 adjacent the outlet end of the
exhaust passageways 109 prevents dirt from entering the
passageways.
Operation of the device shown in FIGS. 5 and 6 and the control of
the supply of compressed air to the working chamber by the air
distribution mechanism during the forward driving movement of the
device is substantially identically to that disclosed hereinabove
with regard to the device shown in FIG. 1 and a repeat of that
discussion is not felt necessary. However, it should be noted that
the device of FIGS. 5 and 6 is a refined embodiment of the device
of FIG. 1 and its additional features generally provide for a
better performance in the field.
When the herein disclosed device of FIGS. 5 and 6 encounters an
insurmountable obstacle or when it is desired for other reasons to
reverse the motion of the device whereby the device can be
retreated under the action of the compressed air back to the
surface, the compressed air supply hose 110 is temporarily
disconnected from the compressed air source (not shown) and is
rotated to transmit the torque to the compressed air supply sleeve
94 with which the hose 110 is connected non-rotatively. In this
manner the sleeve 94 is rotated in the unscrewing direction, that
is, it is unscrewed from the nut assembly 100 into the rearmost
position of the sleeve 94, in which the abutment 106 thereof
engages the front fact of the nut 100.
With the compressed air supply sleeve 94 being set in the last
mentioned position, the impact member during its forward stroke is
stopped by the pressure of the compressed air in the front chamber
90 before it reaches the internal end wall of the housing 80, and
thus delivers no impact upon the housing 80 in the forward
direction. Moreover, the now increased initial volume of the front
chamber 90 and the rearmost position of the head of the sleeve 94
are responsible for the impact member 84 reaching the front face of
the nut 100 during the return stroke thereof and thus delivering a
rearwardly directed blow upon the nut. These repeated impacts of
the impact member 84 upon the nut 100 drive the entire mechanism
for the retreating motion.
The present invention provides an improved impact device for
driving holes into the earth having reversing means which permit
the device to be retreated from the hole. The device includes novel
air distribution means which adjust the supply of compressed air to
the working chambers according to the direction of the device
desired.
Having fully described our invention, it is to be understood that
we do not wish to be limited to the details herein set forth, but
our invention is of the full scope of the appended claims.
* * * * *