Note: Descriptions are shown in the official language in which they were submitted.
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Feeding device for feeding a wire in a rock bolting
equipment
The invention relates to a feeding device for
feeding a wire in a rock bolting equipment, the feeding
device comprising at least one pair of feed wheels between
which the wire is arranged to pass during its feeding, and
a feed motor for rotating the feed wheels during the
feeding of the wire.
During rock bolting, longer holes require the use
of wire bolting wherein a wire provided on a reel is
pushed into a drilled hole and soldered thereto. The most
common manner is to push the wire into the hole manually
and to thereafter supply a soldering material to the hole.
This technique is rather unreliable, laborious and
dangerous. Wire bolting devices are further known for
example from US Patent 4,728,219. In these devices, the
soldering material is first fed into the hole, whereafter
the wire is pushed mechanically into the soldering
material.
Finnish Published Specification 831,481 discloses
a feeding device where the feeding takes place by means of
three feed wheels such that they are positioned
triangularly with respect to each other and a bolt is fed
from between them. In this arrangement, the bolt is bent
by feeding two of the feed wheels towards the third feed
wheel that is situated in the middle thereof on the other
side of the wire, so that the bolt bends. During normal
feeding, the wheels are in a fixed position with respect
to each other.
Such mechanical feeding can be implemented in a
rather simple manner when the wire thickness is constant
at all times. On the other hand, with a so-called bulb-
anchor wire such a device cannot be used. A bulb-anchor
wire comprises at regular intervals points where the wire
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strands have been spread into a sparse section that is
thicker than the rest of the wire, so that the soldering
material can penetrate between the wire strands and it
locks the wire in place effectively. Sections that have
been widened with a conventional mechanical feeding device
would be compressed and would not therefore be useful:
The purpose of the present invention is to
provide a feeding device that can also be used to feed
this kind of bulb-anchor wires such that they
substantially maintain their shape. The device according
to the invention is characterized in that at least one of
the feed wheels of the pair of feed wheels is mounted
movably with respect to the body of the device in the
transverse direction of the wire, and that a loading means
is connected to act on the feed wheel, which presses the
wire placed between the pair of feed wheels with the
desired force by the action of the loading means while the
wheel may move transversely to the wire to be fed
according to the wire thickness.
The basic idea of the invention is that one feed
wheel or, if desired, both feed wheels of a pair of feed
wheels are connected to a loading means that keeps the
pressure between the feed wheels substantially constant.
Therefore, the feed wheels press the wire situated between
them with a suitable predetermined force that does not
damage the wire while the wheels may move further apart
from each other as the wire thickness changes, but the
loading still remains substantially unchanged. The basic
idea of a preferred embodiment of the invention is that it
comprises two pairs of feed wheels, and the wire passes
between each pair of wheels during the feeding. Another
essential feature of the invention is that the feed wheels
of the wheel pair situated on the other side of the wire
are mounted on a bogie assembly that may turn around the
mounting shaft between the wheels such that when the
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expanded section reaches the pair of wheels, the wheels
may move further away from each other. Yet another basic
idea is that the bogie assembly is connected from its
central shaft to the loading means that is operated by a
pressure medium and that contains a pressure that keeps
the feed force acting against the wire substantially
constant and allows the bogie assembly to move away from
the wire when the expanded section passes between the feed
wheels and, correspondingly, to return so that the feed
force remains substantially constant. According to
another preferred embodiment of the invention, each pair
of feed wheels comprises one drive wheel and one freely
rotating wheel, in which case both pairs of wheels feed the
wire in a substantially similar manner. According to yet
another preferred embodiment, one of the freely rotating
wheels is a measuring wheel the rotation of which
produces a measurement signal that is proportional to the
feed length of the wire, so that the exact wire feed
length can be measured in a simple and easy manner.
It is an aspect of the present invention to
provide a feeding device for feeding a wire in a rock
bolting equipment, the feeding device comprising at least
one pair of feed wheels between which the wire is arranged
to pass during its feeding, loading means for pressing said
pair of feed wheels towards each other, and a feed motor
for rotating the feed wheels during the feeding of the
wire, characterized in that at least one of the feed
wheels of the pair of feed wheels is movably mounted with
respect to a body of the device in a transverse direction
of the wire, and that said loading means is connected to
act on the at least one movably mounted feed wheel with a
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desired force so that the at least one movably mounted
wheel is moved transversely to the wire to be fed
according to the wire thickness.
The invention will be described in greater
detail in the accompanying drawings, in which
Figure 1 is a schematic side view of a device
according to the invention,
Figure 2 shows schematically a simplified
hydraulic diagram of a device according to the invention,
and
Figure 3 is a schematic side view of another
embodiment of a device according to the invention.
Figure 1 shows schematically a wire feeding
device according to the inventiori. The device comprises a
body 1. It also comprises two pairs of feed wheels the
first of which consists of feed wheels 2a and 2b and the
second of which consists of feed wheels 3a and 3b. One
wheel of each pair of feed wheels, in this case wheels 2a
and 3a, is mounted on the body 1 rotatably but otherwise
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immovably with respect to it. Further, the other feed
wheel of each pair of feed wheels, i.e. wheels 2b and 3b,
is mounted on a separate bogie assembly comprising a bogie
frame 4. The feed wheels 2b and 3b are connected to the
bogie frame 4 rotatably but otherwise immovably with
respect to it. The bogie frame 4 is in turn connected
movably with respect to the body 1 so that it can move
substantially perpendicularly to the axes of the feed
wheels towards or away from the feed wheels 2a and 3a
connected to the body. For this purpose, the bogie frame 4
is attached from the middle of the feed wheels 2b and 3b
mounted thereon to a loading means 6, which in this case
is a pressure medium cylinder connected to the body 1,
such that the frame can turn around the shaft S. The bogie
frame 4 is attached to the piston rod of the pressure
medium cylinder such that the frame can turn with respect
to the rod around the shaft 5 that is parallel to the axes
of the feed wheels. For the purpose of feeding, a wire 7
is arranged to pass between the pairs of feed wheels, i.e.
feed wheels 2a and 2b, and 3a and 3b, respectively, so
that it is pressed between them. The pressure medium in
the pressure medium cylinder acting as the loading means 6
is provided with such a pressure that the feed wheels 2a
and 2b, and 3a and 3b, respectively, are pressed together
with a force that makes the wire 7 move ahead in the
desired manner also when it is pushed into a hole filled
with soldering material.
When a so-called bulb-anchor wire shown in Figure
1 is used, the forward movement of the wire makes the
expanded wire sections 7a push the feed wheels belonging
to the same pair of wheels away from each other. In such a
situation, a feed wheel, such as feed wheel 3a, that is
mounted on the bogie frame 4 may move away from the other
feed wheel 3a so that the expanded section is not damaged
but a sufficient feed force is maintained due to the
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active pressure medium. Since the other pair of feed
wheels is not normally forced to change its distance at
the same time, the bogie frame 4 naturally turns around
its shaft S. When the expanded section 7a has passed the
5 pair of feed wheels, the feed wheel 3b moves back towards
the other feed wheel 3a along the surface of the wire 7 by
the action of the pressure of the pressure medium, and a
corresponding movement also occurs with the feed wheels 2a
and 2b when the expanded section 7a reaches them.
In order to provide a feed force, the pairs of
feed wheels are provided with feed motors such that one of
the wheels in each pair is equipped with a motor and the
other wheel rotates freely. In the embodiment shown in the
figure, the feed motors 8a and 8b are placed such that the
feed motor 8a rotates the feed wheel 2a and the feed motor
8b rotates the feed wheel 3b. The feed wheel 2b rotates
freely with respect to the bogie frame 4 and,
correspondingly, the feed wheel 3a rotates freely with
respect to the body 1. The feed wheel 3a is preferably
formed into a measuring wheel that provides signals to a
sensor 9 when it rotates, so that the feed length of the
wire 7 can be measured accurately and the feeding of the
wire into the hole can therefore be monitored easily.
The feed wheel 3a is provided through machining
with recesses 3a' at regular intervals around it. The body
1 is correspondingly provided with a sensor 9, which
produces an electric pulse whenever a recess reaches it.
The sensor 9 is preferably an inductive sensor which also
operates reliably under difficult circumstances. Some
other kind of sensor arrangement known per se can
naturally also be used to measure the rotation of the
measuring wheel 3a and thus to measure the feed length of
the wire.
Figure 2 shows schematically the hydraulic
coupling of the feeding device of Figure 1 as regards the
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operation of the device. When a wire is fed, a pressure
fluid is supplied to the loading means 6 along a duct l0a,
so that the piston 6a of the hydraulic cylinder acting as
the loading means comes out and pushes the bogie frame 4
shown in Figure 1 and the feed wheels 2b and 3b that are
connected to the frame and that are shown above in Figure
1 towards the feed wheels 2a and 3a mounted on the body 1
and shown below in the figure. The pressure in the duct
10a is adjusted such that the pressure acting on the wire
between the feed wheels is suitable and it does not
compress the expanded sections of the wire when for
example bulb-anchor wires are used. In order to keep the
loading substantially constant, the duct l0a is connected
to a pressure accumulator 11 having a pressure of 50 bar,
for example. When the piston 6a moves as the expanded wire
sections pass between the feed wheels, the pressure fluid
flows from the duct l0a to the pressure accumulator 11 and
back, so that the pressure remains substantially
unchanged. The pressure medium is discharged along the
duct l0a when the piston 6a is moved forward and it is
also possible to feed the pressure medium along this duct
when the piston 6a is to be moved to its rearmost position
when a new wire is placed between the feed wheels, for
example, or for some other reason. Figure 2 further shows
the feed motors 8a and 8b that are connected hydraulically
in parallel such that a pressure fluid is fed
simultaneously into each motor along a duct 12a and the
pressure fluid that has flown through the motors is
discharged along a duct 12b. The pressure fluid that
arrives along the duct 12a ends in a control circuit 13
where it is distributed to pass along different ducts 14a
and 14b to feed motors 8a and 8b, respectively. In order
that both motors would rotate at the same speed, the
control circuit 13 comprises pressure-controlled throttles
15a and 15b that are guided by the pressure of the
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pressure fluid passing to the other motor. In this manner,
the control circuit 13 distributes the flow of the
pressure fluid in exactly equal amounts to each motor so
that their speeds of rotation are also the same. As a
result, both pairs of feed wheels constantly pull the wire
at the same speed and no skidding or idle rotation occurs.
Figure 3 is a schematic side view of another
embodiment of a device according to the invention. The
device shown in the figure corresponds otherwise to the
one shown in Figure 1 and like reference numerals refer to
corresponding parts. The difference is that instead of a
bogie assembly, each upper feed wheel 2b and 3b is
provided with a separate loading means 6' and 611,
respectively. In this embodiment, the feed wheels 2b and
3b are placed movably in a manner known per se, such as by
means of a slide structure, so that they can move with
respect to the body 1 either towards their pair of drive
wheels 2a and 3a, respectively, or away from them. The
loading means 6' and 6" of each upper drive wheel 2b and
3b are for example hydraulic cylinders connected to the
pressure accumulator as shown in Figure 2, or pneumatic
cylinders that are provided beforehand with a sufficient
pressure. Air or gas contained in the pneumatic cylinder
allows the drive wheels 2b and 3b to move back and forth
depending on the wire thickness without a need for
additional pressure fluid ducts or other extra components.
The invention is described above in the
specification and in the drawings by way of example only,
and it is not restricted thereto in any way. The feed
motors can be placed in different ways and they can be
connected hydraulically in different manners for example
= in series so that the same pressure fluid flows through
each motor. The measurement of the wire feeding can also
be implemented with different measuring devices known per
se, and a separate feed motor can also be used in each
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feed wheel, if desired. The loading means 6 may be a
pressure medium cylinder connected directly to the bogie
frame as shown in the figure, or it may be attached
thereto indirectly by means of different mechanical
transmission means. Further, even though the figure shows
a preferred structure of the invention where two of-the
II feed wheels are fixedly mounted on the body 1 and the
other two wheels 2b and 3b are attached movably and
rotatably to the bogie frame, it is also possible to
connect the fixedly placed feed wheels 2a and 3a to a
bogie frame of their own. In practice, this arrangement is
not usually necessary, but the embodiment shown in Figure
1 is very advantageous in use. It is also possible to
attach the feed motors for example to three feed wheels or
to all of the wheels. When only one pair of feed wheels is
used, the loading means can be connected to act on one of
the wheels, and correspondingly when two pairs of feed
wheels are used, one or both wheels of each pair of feed
wheels can be provided with separate loading means that
keep the compression force substantially constant on a
predetermined level and that allow the feed wheels to move
towards and away from each other as the wire thickness
changes without a substantial change in the compression
force.
