Note: Descriptions are shown in the official language in which they were submitted.
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ROCK DRILLING DEVICE
Field of the invention
The invention concerns a drill string guide device according
to the preamble of claim 1. The invention also concerns a rock
drilling device including such a drill string guide device.
Background of the invention
During rock drilling, straightness of the holes is very
important, since straight drill holes increase the possibility
of influencing how the rock is disintegrated during blasting
compared to situations with unintentionally curved drill
holes. Further, the contour of a tunnel etc. can be controlled
more accurately.
For guiding the drill string, drill string guide devices
are used, whereof a known drill string guide device is
attached at the distal end of a feed beam and assists during
directing the drill string in order to achieve enhanced
collaring and increased straightness of the hole.
US-B2-6 860 343 describes a pair of grip tongs for
mounting on a support for clamping action against a drill
string. A first and a second jaw are manoeuvrable with the aid
of a fluid cylinder device to a position where they are in
engagement with, and a position where they release a drill
string. The device is provided with an arrangement with
floating suspension on a support, which has a fixed distance
to the centre of the drill string and thus to the jaws when
they are pressed against each other, as well as when they are
pressed from each other. The jaws are controlled for movement
on a set of guide axes.
A problem with today's drill string guides is that they
consist of many mutually movable parts which are subjected to
wear. The wear is considerable because of the very abrasive
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environment, which often prevails where the drill string guides
is used. Worn parts result in turn in deteriorated guiding of
the drill string and thereby deteriorated hole linearity. The
wear also results in shortened service intervals and even
unplanned production breaks. Because the drill string guide is
one of the components on a drill rig which is most subjected to
wear, it is important for the productivity and accuracy of the
entire drill rig to have this component well functioning.
Alm and most important features of the invention
It is an aim of some embodiments of the present invention to
provide a drill string guide device of the kind mentioned above
which solves or at least reduces the above problems of the
prior art, and at the same time provides a component with high
precision which can be produced with good economy.
Drill string guide device for mounting to a feed beam
of a rock drill rig and for the support of a drill string,
including a housing wherein is arranged a piston cylinder
device for manoeuvring of a first jaw and a second jaw, wherein
each one of the jaws is movable between an engagement position
in the direction towards a position of the drill string, for
engagement therewith, and a releasing position in the direction
from the position of the drill string for releasing thereof;
wherein, the piston cylinder device includes a first fluid
cylinder with a first piston unit for manoeuvring of the first
jaw, wherein the first jaw is supported by the first piston
unit, and wherein the piston cylinder device includes a second
fluid cylinder with a second piston unit for manoeuvring of the
second jaw, wherein the second jaw is supported by the second
piston unit, which is guided in the first piston unit.
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By the jaws being directly carried by the respective
piston units, it is achieved that no particular separate
guiding device or guide units are necessary for controlling the
movements of the jaws. This is an important advantage, since
this aspect makes it possible to construct a robust drill
string guide that in principle has only two movable parts,
firstly the unit including the first jaw and the first piston
unit, secondly a unit including the second jaw and the second
piston unit. Hereby is achieved, in an effective manner, that
the number of parts that are subjected to wear is reduced to a
minimum.
The invention makes it possible to construct the
drill string guide device with large bearing surfaces, and this
together with minimized number of movable parts, results in
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that the working lift will be longer than in respect of known
drill string guide devices. In particular, this is true in a
position for guiding of the drill string during rock drilling
in progress, wherein the jaws are moved inwardly a smaller
distance than in the engagement position itself.
A consequence of the invention, is that only two slits
between movable parts have to be sealed, namely between the
housing and the first piston unit and between the first and
the second piston unit. Protection for these slits can be
obtained by means of well-known, simple and effective means.
This also contributes to an increased working life of the
device.
It is preferred that the first piston unit is guided in
the first cylinder with the aid of bearing means for taking up
sideward forces occurring on the first jaw. In particular this
means that a piston rod means, being part of the piston unit,
at its exit from the cylinder through the housing, is
supported by suitable bearing surfaces such as bearing rings
or the like.
A corresponding advantage is obtained with respect of the
guiding of the second piston unit inside the first piston
unit. By the second unit being guided inside the first piston
unit, a compact device is obtained and a preferred movement
pattern for the jaws.
By the second cylinder being fully enclosed inside the
first piston unit, a particularly compact unit is achieved,
and the number of parts/surfaces with requirements for strict
tolerances is minimized. Further it is achieved that the
clamping force acts substantially only between the piston
units. This force therefore will not affect the other
structures of the device, wherefore the force for positioning
the jaw package can be set relatively small and in reality
independent of the clamping force.
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By the first jaw having an inwardly curved, shallow, U-
shaped engagement surface, adaptation to the outside
dimensions of a drill string to be gripped by the device is
allowed. In particular it is preferred that the engagement
surface has portions with two different radiuses of curvature,
for engagement on differently sized objects, as for example on
the one hand the drill string itself, on the other hand a
joining sleeve between two drill string units.
The piston rod chamber in the first cylinder and the end
wall chamber of the second cylinder are preferably possible to
pressurize simultaneously, for initiating of said engagement
position, by being interconnected through a channel.
Further, the piston rod chamber of the second cylinder
and the end wall chamber of the first cylinder can preferably
be pressurized simultaneously, for initiating of said
releasing position, by being interconnected through a channel.
When a guide unit for a drill string including a fix
guide sleeve which is aligned with the jaws is arranged on the
housing, preferably distally with respect to it, that is in
the drilling direction, guiding of the drill string during
drilling is obtained and it is avoided that the jaws and the
associated piston units are subjected to stressing shocks. In
particular it is preferred that the guide unit is positioned
such that a rotation preventing portion controls the first jaw
against undesired rotation around an axis through the first
piston unit.
Further advantages of different features of the invention
will be explained below. The invention also concerns a rock
drilling machine including a drill string guide device
according to the above.
Brief description of drawings
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The invention will now be described in greater detail by way
of an embodiment and with reference to the annexed drawings,
wherein:
Fig. 1 shows a drill string guide device in a
perspective view,
Fig. 2 shows an axial section through the drill
string guide device according to Fig. 1,
Fig. 3 shows diagrammatically a rock drilling
device including a drill string guide device according to the
invention, and
Figs 4a and b show the drill string guide device with
the jaws in different positions.
Description of embodiment
In Fig. 1 is shown a drill string guide device 1 including a
gripping unit 2 for engagement with and releasing,
respectively, a drill string which extends (not shown) through
the drill string guide device. Distally of the drill string
guide device, that is in the drilling direction as seen in
respect of the gripping unit 2, is attached a guide unit 3,
which has guiding means in order to control, to a certain
extent, the position of a drill string during drilling.
The gripping unit 2 includes a jaw ring 4, which is
supported movably with respect of a housing 6 of the drill
string guide device 1. A fastening surface indicated with 5
has on a flanged portion through-holes F for receiving screws,
which are intended to be screw-fastened into the end area of a
feed-beam of a drill rig. Pi - P4 indicate inlet/outlet ports
of channels, which are drawn to a fluid cylinder device in a
manner which is explained below. According to the shown
embodiment, only two of these ports have to be used in
operation. With a "fluid cylinder" is intended a cylinder
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which is manoeuvrable with gas as well as liquid under
pressure.
With reference to Fig. 2, the grip unit 2 inside the jaw
ring 4 includes a first jaw 7 and a second jaw 8 which are
arranged to be moved towards each other for engagement with,
and from each other for release of, a drill string. The jaw
ring 4 is, via screws 12, carried by a first piston unit 9
which includes a first piston 10 and first piston rod means
11. The first piston unit 9 is movable up and down, as seen in
the figure, inside a first cylinder 13, after pressurizing of
a first end wall chamber 19 and a first piston rod chamber 20,
respectively.
Pressurizing of the first end wall chamber 19 moves the
first jaw from a drill string position, for releasing action
and pressurizing of the first piston rod chamber 20 results in
pulling down the first jaw 7 for engagement with said drill
string.
The second jaw 8 is directly carried by a second piston
unit 14 which includes a second piston 15 and second piston
rod means 16. The second piston 15 is movable inside a second
cylinder 35, which in the shown embodiment as a whole is
received inside the first piston unit 9. Pressurizing a second
end wall chamber 21, results in pressing out the second jaw 8
and a gripping action against the drill string, whereas
pressurizing a second piston rod chamber 22, results in
pulling in of the second jaw 8 and releasing the drill string.
The stroke of the second piston is shown a little more than
twice as great as the stroke of the first piston, i.a. in
order to compensate for jaw wear and because of the second one
being carried by the first one respectively.
The drawing of channels is such in the shown embodiment,
that the first end wall chamber 19 and the second piston rod
chamber 22 are possible to pressurize simultaneously through a
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second pressurizing channel 24, such that said releasing
position is obtained, that is the position which is shown on
Fig. 2. Through the first piston rod means 11, in the area of
the second piston rod chamber 22, is arranged through-going
channel means 25 in order to let in pressure medium from the
second pressurizing channel 24 to the second piston rod
chamber 22. Pressure in the chamber 21 creates a clamping
force between the pistons. Pressure at 20 positions the force
couple.
When pressurizing the first piston rod chamber over a
first pressurizing channel 23, the second end wall chamber 21
will be pressurized simultaneously over through-going channel
means 26 through the first piston rod means 11, which will
press down the first piston unit with the first jaw and at the
same time press out the second piston unit with the second jaw
for engagement with a drill string.
The first cylinder 13 is sealed by a first cylinder end
wall 17 and the second cylinder by a second cylinder end wall
18. The housing is made rigid so as to take up side forces
from the jaws in operation of the device. In particular, the
respective piston rod side through-holes from the respective
cylinders have bearing means in the form of bearing rings 27
and 28, respectively, and the respective pistons have
corresponding bearing rings for ensuring good bearing support
for the mutually movable parts.
The respective slits which are formed at the piston rod
means are outmost provided with wipers for minimizing
introduction of abrasive material to the bearing surfaces.
Seals are arranged at suitable positions in a manner known per
se, which is not discussed further here.
The guide unit 3 has a guide sleeve 31 which is intended
to guide the drill string during drilling and thereby, during
drilling, take up shocks and forces resulting from movements
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of the drill string from it's ideal position. Between the rear
portion of the guide unit 3 and the jaw ring 4 is arranged a
minor slot 32 which is measured such that the movement of the
first jaw 7 up and down is not prevented at the same time as
the rear surface of the guide unit 3 provides a rotation stop
which prevents rotation of the jaw ring 4 about the axis of
the first cylinder. In the guide sleeve 31 is arranged a
cavity, wherein a drill bit can be received.
The second jaw is stud-shaped and convex and rotation
symmetrical, wherefore in this embodiment it does not need to
be secured against rotation.
With 33 are indicated two engagement spikes which are
engaged against the rock during collaring and during drilling.
In Fig. 3 is diagrammatically shown a rock drilling
device for the inclusion in a drill rig, said rock drilling
device including a rock drilling machine 36, a drill sting 38,
a feed beam 37 and a feed-slide 39 for carrying the drilling
machine 36. Distally on the feed-beam 37 is arranged a drill
string guide device according to the invention.
In Figs 4a and b are shown, as seen in the axial
direction of a drill string to be gripped, the drill string
guide device 1 with the jaws in a releasing position and an
engagement position, respectively. The engagement surface of
the first jaw 7 has a first portion 40 with a radius of
curvature r adapted for gripping a drill string, and a second
portion 41 being comprised of two engagement areas at the
sides of the first portion, with a greater radius of curvature
R which is adapted so as to grip a joining sleeve.
The invention can be modified in the scope of the
following claims. The jaws can thus be shaped otherwise with,
as an example, a jaw ring 4 which can be opened sideways in
order to allow sideways introduction of a drill string. The
second jaw can also be non-rotational symmetrical, for example
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have a shape which is similar to or the same as the first jaw
7 and be partly surrounding a drill string. In that case a
rotation stop must be arranged, which can be made as is per se
well-known.
The drill string guide device can be without the guide
unit 3 even if the shown arrangement is preferred for the sake
of wear and maintenance. The cylinders can be arranged
otherwise, for example such that the second cylinder is
received in the housing axially following, or outside, the
first cylinder and thus is not received inside the first
piston unit. The cylinders can be made single-acting, for
example by positioning a spring of some kind, mechanic or
pneumatic or/and synthetic for actuation of the respective
piston in one of the directions. A simple solution is thereby
to position a metal pressure spring in the second end wall
chamber for action between the lower part of the second piston
and the upper portion of the second cylinder end wall.
