Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid-flushed rock drill having a drilling
head axially movable, within predetermined limits, relative to a drill rod and
used,
advantageously, for drilling blast bores in mining industry.
2. Description of the Prior Art
U.S. Patent No. 6,021,855 discloses a water-flushed rock drill having a
water-flushed, pot-shaped drilling head axially movable, within predetermined
limits,
io relative to a drill rod, which permits to achieve a high output. The freely
axially
movable, within predetermined limits, drilling head impacts, at an idle or
blank impact,
without being damped, a drive side axial stop, which results in an excessive
material
fatigue.
An object of the present invention is to provide a rock drill with a drilling
head axial movable, within predetermined limits, relative to a drill rod and
with a
reduced material fatigue even during idle impacts.
SUMMARY OF THE INVENTION
This and other objects of the present invention, which will become
apparent hereinafter, are achieved by providing a rock drill including a drill
rod, a liquid-
2o flushed, pot-shaped, drilling head axially movable, within predetermined
limits, relative
to the drill rod with the drill rod forming a piston that defines, together
with an inner
surface of the drilling head, a variable volume filling chamber, and at least
one
hydrodynamical narrow opening for filling the filling chamber with fluid.
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During blank impacts of the drilling head, the free movement with large
oscillation amplitudes is damped as result of hydrodynamic resistance which is
caused
by flow of a substantially incompressible fluid under pressure through the
hydrodynamical narrow opening from the variable volume filling chamber. During
the
operational stage, when the drilling head contacts the worked stone, the
oscillation
amplitude, which is rather small in this case, is absorbed due to the
elasticity of the fluid
in the filling chamber, and damping hardly takes place.
Advantageously, the at least one hydrodynamical narrow opening is
formed as a hydrodynamical narrow gap, which permits to avoid arrangement of
sealing
io means between the drill rod and the drilling head.
Advantageously, the drilling head has a drive side, axial stop element for
the drill rod and which closes the filling chamber from the drive side. This
provides for
an easy mounting and dismounting of the drilling head.
Advantageously, the axial stop is formed as a multi-piece nut which is
arranged in the radially narrowing region of the drill rod. This likewise
facilitate
assembly of the drilling head.
Advantageously, both the drilling head and the drill rod have associated
rotation transmitting elements, such as polygons, which formlockingly
cooperate with
each other. This provides for transmission of a torque from the drill rod to
the drilling
2o head.
Advantageously, the drive side stop element forms part of the rotation-
transmitting element, e.g., an inner polygon or an arcuate feather key which
transmits a
torque from the drill rod to the drilling head during its axial movement. The
axial stop
element is formed as a replaceable part with a low wear-resistance.
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The novel feature of the present invention, which are considered as
characteristic for the invention, are set forth in the appended claims. The
invention
itself, however both as to its construction and its mode of operation,
together with
additional advantages and objects thereof, will be best understood from the
following
detailed description of preferred embodiments, when read with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS:
The drawings show:
Fig. 1 a longitudinal cross-section view of a rock drill
Io according to the present invention in an operational
position of the drilling head;
Fig. 2 a cross-sectional view along line I I-II in Fig. 1; and
Fig. 3 a longitudinal cross-sectional view of the rock drill
shown in Fig. 1 with a condition of the drilling head
during a blank impact.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A liquid-flushed rock drill 1 according to the present invention, which is
shown in Figs. 1-3, has a drilling rod 3, a pot-shaped drilling head 4 movable
axially,
within predetermined limits, relative to the drill rod 3, and an insert 2
which is formed of
2o a hard material and is received in the drilling head 4. The drill rod 3
forms a piston 6
which defines, together with an inner surface 5 of the drilling head 4, a
filling chamber 8
the volume of which is changed during movement of the piston 6 relative to the
inner
surface 5 of the drilling head 4 and which is equal to nil in an end position
of the
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piston 6 adjacent to the tool with which the rock drill 1 is used. The filling
chamber 8 is
filled with fluid or is discharged through several hydrodynamic narrow
openings 7a, 7b,
7c, 7d.
The openings 7a, 7b, 7c, 7d are formed, respectively of radial bores in the
drill rod 3 and the drilling head 4 and annular gaps formed between the inner
surface 5
of the drilling head 4 and the drill rod 3.
The drilling head 4 has axial stop means 9 for the piston 6 of the drill rod 3
and which is provided at a drive side of the drilling head 4. The axial stop
means 9 is
formed as a two-piece ring nut the two pieces of which are arranged in the
radially
1o narrowing region of the drill rod 3. The ring nut closes the filling
chamber 8 from the
tool side. Upon the piston 6 reaching the axial stop means 9, the volume of
the filling
chamber 8 becomes equal to nil (see Fig. 3). The axial stop means 9 is formed
of a
softer steel than the drilling head 4 is formed of and is less wear-resistant
than the
drilling head 4 which is formed of a fully hardened steel. The axial stop
means 9 forms
part of rotation transmitting means 10 that is formed as a chamfered
tetrahedron
corresponding to the outer profile 11 of the drill rod 3 (see Fig. 2).
Though the present invention was shown and described with references
to the preferred embodiment, such is merely illustrative of the present
invention and is
not to be construed as a limitation thereof and various modifications of the
present
2o invention will be apparent to those skilled in the art. It is therefore not
intended that the
present invention be limited to the disclosed embodiment of details thereof,
and the
present invention includes all variations and/or alternative embodiments
within the spirit
and scope of the present invention as defined by the appended claims.
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