Background of the Invention
1. Field of the Invention
The present invention relates to a down-the-hole hammer for
excavating a pile hole for a foundation work in the building or civil-engineering
field.
2. Description of the Related Art
The down-the-hole hammer which moves a hammer up and down in
association with the motion of a piston, as well-known, in order to
carry out excavation through hitting, has a construction shown in
Figs. 15 and 16 in which reference numeral 1 denotes a piston casing
incorporating a piston 2, 3 denotes a hammer bit, a drive sub 5 in
which the upper end part of the hammer bit 3 is extendably received,
being coupled with the lower end part of the piston casing 1 through
the intermediary of a thread structure.
The middle part of the above-mentioned hammer bit 3 is formed
into a spline shaft which is fitted in a drive sub 5 having an inner
peripheral wall in which concave and convex engaging grooves are
formed. In the figures, reference numeral 6, 7, 8 and 9 denote a foot
valve, O-ring, a bit retainer ring and a piston retainer ring,
respectively.
In the upper part of the piston 2, there are arranged a rigid
valve 11 fitted at its outer periphery with an O-ring 10 and holding
at its center a choke 14, a make-up ring 12, a valve guide 13, a
valve spring 15 and a check valve 16, and a top sub 17 serving as a
valve seat for the check valve 16 is screwed in the upper part of the
casing 1.
Further, the top sub 17 is formed at its center with a thread
hole in which a truncated conical shape thread part formed in the
lower part of a joint adapter 18 for coupling to an auger shaft is
screwed.
That is, the joint adapter 18 and the top sub 17, the top sub
17 and the piston casing 1, and the piston casing 1 and the drive sub
5 are joined by means of threads.
The down-the-hole hammer is connected to the front end part of
an auger shaft such as a screw shaft, serving as an excavator,
through the intermediary of the above-mentioned joint adapter 18, and
excavates the ground while it is rotated together with the auger shaft.
This rotation is made mainly in the clockwise direction for
excavation, and an earth pressure is applied to the peripheral surface
of the excavator in a weak stratum of the ground. Accordingly, the
outer periphery of the down-the-hole hammer would possibly be caught.
In such a case, the rotation is made not only in the clockwise
direction but also in the counterclockwise direction so as to repeat
the clockwise and counterclockwise directions in order to overcome the
friction at the outer periphery of the hammer.
Should the above-mentioned counterclockwise rotation be taken,
the parts joined through the above-mentioned threads would be
loosened so as to come off from one another.
Further, should excavation under the counterclockwise rotation
be continued for a long time due to a long time use, the threads
would be inadvertently tightly fastened. As a result, the replacement
of the hammer bit 3 to be replaced with another cannot be made in a
job-site without no special tool. Thus, special exclusive removing and
attaching jigs (hydraulic chuck and the like) are required therefor,
that is, the replacement in the job site cannot be made, the hammer
has to be brought into its maker's firm in order to replace them.
One object of the present invention is to provide a down-the-hole
hammer which can eliminate the above-mentioned disadvantages
inherent to the prior art, so as to eliminate such a risk that the
coupling between components are loosened even though the normal and
reverse rotations are made, and in which components are simply
connected with one another or disconnected from each other without
using special jigs even during replacement of the components.
Summary of the Invention
To the end, according to the present invention, there is
provided a down-the-hole hammer in which a piston casing
incorporating a piston is connected thereto at its upper end with a
top sub coupled to a joint adapter, and at its lower end with a drive
sub extendably receiving therein a hammer bit, characterized in that
the joint adapter and the top sub coupled to the former are formed as
one unit body, the coupling between the piston casing and the top sub,
and the coupling between the piston casing the drive sub is made such
that the connection on the top sub or drive sub side is formed into a
polygonal shaft or a spline shaft, and the connection on the piston
casing side is formed into a recess in which the polygonal shaft or
the spline shaft is fitted so as to fit them each other, and a pin
hole is formed in the boundary zone of the fitting, bridging
therebetween, and a pin serving as a key is removably inserted in the
pin hole.
Second, the pin hole is formed horizontally, third, stop rings
are arranged in front and rear of the inserted pin in order to
prevent the pin from coming off or the front end of a bolt is pressed
against the side part of the inserted pin in order to prevent the pin
from coming off, and fourth, four in total of pin holes are formed in
two groups each consisting of two upper and lower pin holes arranged
in parallel with each other so that the locking is made by four pins
inserted in these pin holes.
According to the invention stated in claim 1, the joint
adapter and the top sub coupled to the former are integrally formed,
and accordingly, they are never loosened from each other since it is
not the case of thread engagement therebetween as in the conventional
case. Further, the connection between the piston casing and the top
sub and connection between the piston casing and the drive sub are
made such that the polygonal shaft or the spline shaft is fitted in
the complementary recess, the locking is made by a pin hole formed in
the boundary zone of the fitting and bridging therebetween and a pin
serving as a key, and accordingly, they are never loosened since it is
not the case of thread connection as in the conventional case.
Further, in the case of replacement of components, when the
pin is removed from the pin hole, the polygonal shaft or the spline
shaft fitted in the recess, can be directly pulled out therefrom,
thereby the replacement can be made simply and rapidly in a job side
without using special jigs.
According to the invention stated in claim 2, in addiction to
the above-mentioned technical effects and advantages, since the pin
hole is horizontally formed and the pin serving as a key is
horizontally inserted, the length of the pin can be effectively used
for surely and firmly locking the components together in a horizontal
direction.
According to the invention stated in claim 3, the coming-off
of the pin can be simply prevented by the stop rings, and according
to the invention stated in claim 4, the coming-off of the pin can be
simply prevented by pressing the front end of the bolt against the
side part of the inserted pin.
According to the invention stated in claim 5, four, in total,
of the pin arranged up and down and accordingly, the locking can be
surely and firmly made.
Brief Description of the Drawings
Fig. 1 is a partly cut-off front view illustrating an
embodiment of a down-the-hole hammer according to the present
invention;
Fig. 2 is a sectional view along line A-A in Fig. 1;
Fig. 3 is a sectional view along line B-B in Fig. 1;
Fig. 4 is a cross-sectioned plan view illustrating another
example of the coupling between a top sub and a piston casing;
Fig. 5 is a cross-sectioned plan view illustrating another
example of the coupling between the top sub and the piston casing;
Fig. 6 is a transverse sectioned view illustrating such a case
that a hammer cover is provided;
Fig. 7 is a sectional view along line C-C in Fig. 6:
Fig. 8 is a plan view illustrating a pin used in the first
embodiment;
Fig. 9 is a plan view illustrating a stop ring used in the
first embodiment;
Fig. 10 is a plan view illustrating a pin used in a second
embodiment;
Fig. 11 is a cross-sectioned plan view illustrating an
essential part used in the second embodiment;
Fig. 12 is a plan view illustrating a pin used in a third
embodiment;
Fig. 13 is a cross-sectioned plan view illustrating essential
part shown in the third embodiment;
Fig. 14 is a transverse sectioned side view illustrating an
essential part shown in a fourth embodiment;
Fig. 15 is a transverse sectional side view illustrating a
conventional down-the-hole hammer; and
Fig. 16 is an exploded perspective view illustrating the
conventional down-the-hole hammer.
Detailed Description of the Preferred Embodiments
Detailed explanation will be hereinbelow made of embodiments
of the invention with reference to the drawings. Fig. 1 is a partly
broken front view illustrating an embodiment of a down-the-hole
hammer according to the present invention, Fig. 2 is a sectional view
along line A-A in Fig. 1, and Fig. 3 is a sectional view illustrating
line B-B as mentioned above. In these figures, like reference
numerals are used to denote like parts shown in Figs. 15 and 16 which
show the conventional example.
In the down-the-hole hammer according to the present invention,
as is similar to the conventional example, a top sub 17 coupled to a
joint adapter 18 is connected to the upper end of a piston casing 1
incorporating a piston, and a drive sub 5 in which a hammer bit 3 is
extendably received is connected to the lower end of the piston casing
1.
At first, the connection part (joint) of the top sub 17 is
formed into a polygonal shaft 19 (a hexagonal shaft in this example
as shown in the figures), and the connection part of the piston
casing 1 is formed into a polygonal recess 20 in which the polygonal
shaft 19 is fitted, and which is complementary with the latter. In the
figure, reference numeral 35 denotes an O-ring serving as a seal laid
under the polygonal shaft 19 of the above-mentioned top sub 17.
Further, the boundary zones of the fitting between the
polygonal shaft 19 and the recess 20 are formed therein with two
horizontal grooves having a semi-circular shape, which are mated with
each other so as to define circular pin holes 21 bridging between the
top sub 17 and the piston casing 1 in a horizontal direction.
This pin holes are opened externally, and pins 22 serving as
keys are removably inserted in the pin holes 21 through the openings
of the latter.
Grooves are formed in the peripheral direction of the pin
holes at positions in front and rear of the inserted pins 22, and stop
rings having outer peripheral edge parts fitted in the grooves are
arranged so as to prevent the pins 22 from coming off. Referring to
Figs. 8 and 9 which show the pin 22 and the stop ring 23, the pin 22
has no heads at its opposite ends, the stop rings 23 has a partly
cut-off shape and is a doughnut ring which can be pressed so as to
reduce its diameter.
The connection part (join) in the upper part of the top sub 5
is also formed into a polygonal shaft 19 (a hexagonal shaft in this
example as shown) , the connection part on the stop ring 23 side is
formed into a recess 20 in which the polygonal shaft 19 is fitted, and
which is complementary with the latter. Further, circular pin holes
21 similar to the pin holesas mentioned above are horizontally formed
in the boundary zones of the fitting of the both components, and pins
22 serving as keys are removably inserted in the pin hole 21. Further,
stop rings 23 for preventing the pins 22 from coming off are arranged
at positions in front and rear of the inserted pins 22. Reference
numeral 33 in the figures denotes a packing, and 34 denotes a bit
receiving ring composed of two half-split members which are assembled
together so as to form a ring shape.
The connection between the drive sub 5 and the hammer bit 3 is
similar to that of the conventional one, the center part of the
hammer bit 3 is formed into a spline shaft which is fitted in a
recess 24 formed in the drive sub 5 and having the inner peripheral
wall in which concave and convex engaging grooves are formed.
Thus, the connection between the top sub 17 and the piston
casing 1 and the connection between the piston casing 1 and the drive
sub 5 hold its integrity against either counterclockwise or clockwise
rotation due to the fitting between the polygonal shaft 19 and the
complementary polygonal recess 20, and further, they can be prevented
from being disengaged from each other by means of the pins 22 serving
as keys.
Further, when the disconnection between them is made in order
to replace a component, the stop rings 23 are removed so that the pin
22 can be removed, and accordingly, the polygonal shafts 19 of the top
sub 17 and the drive sub 5 are pulled from the piston casing 1 after
the pins 22 are pulled off, the disconnection can be simply made.
It is noted that the connection part (joint) of the top sub 17
and the drive sub 5 is formed into a spline shaft 25 as shown in Figs.
4 and 5, instead of the polygonal shape, and spline grooves are formed
in the recess 26 on the piston casing 1 side so that the spline shaft
can be fitted thereinto.
Further, in a second embodiment of the present invention, the
pin 22 has a head 22a, as shown in Figs. 10 and 11, for preventing
coming-off of the pin 22, and a recess 22b having a flat contact
surface is formed in the side part of the intermediate part of the pin.
Further, a stop bolt 27 is inserted from the outside so that the front
end of the bolt 27 is pressed against the recess 22b.
In second embodiment of the present invention, a pin 22 having
a head 22a to which spring steel 32 is provided and having a type
which has been use in general in an earth auger or the like is used.
Further, although a set of left and right parallel pin holes
21 is used in the above-mentioned embodiments, in a fourth embodiment,
upper and lower groups each composed of left and right parallel pin
holes 21 are formed up and down, and accordingly, four, in total, of
the pin holes are provided so that the upper pin holes are orthogonal
to the lower pin holes. Further, four, in total, of pins 22 are
inserted into the pin holes 21 so as to effect the locking.
With this arrangement in which several pins are used for the
locking, the locking can be made to be more surely and firmly.
Referring to Fig. 6 which shows a case such that the down-the-hole
hammer is covered with a hammer cover 28 which is adapted to be
replaced with another in accordance with an excavating diameter, and
in the upper part of which a casing 29 or a screw shaft 31 in one
configuration of an auger shaft is located. Vertical ridges 30 are
formed on the hammer cover 28 at suitable intervals so as to ensure
vertical grooves defining gaps through which air can flow, at the
outer periphery of the hammer cover 28 on rotation.
It is noted that the excavator may have such a type that a
rod itself is slid while the rod is chucked at its outer periphery by
a drive shaft, in addition to an earth auger type in which a drive
device is moved up and down along a leader mast. Accordingly, it is
possible to provide such a method that the connection to the upper
part of the down-the-hole hammer is made by using an auger shaft
formed into a polygonal rod, instead of the above-mentioned upper
casing 29 or the screw shaft 31, as a clutch adapted to be rotated.
Industrial Availability
As mentioned above, the down-the-hole hammer according to the
present invention, can prevent occurrence of such a risk that the
connection between components are loosened, even though it is normally
and reversely rotated, and can simply connect and disconnect
components to and from each other without using special jigs in the
case of replacement of a component.