Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Arrangement for controlling boom for rock drilling unit
This invention relates to an arrangement for
limiting the swing angle of a boom for a rock drilling
unit when the boom is being vertically lifted and
lowered, wherein the rock drilling unit comprises a
boom, pivotally connected, relative to a frame, about
vertical and horizontal shafts, and a swing cylinder and
a tilt cylinder between the frame and the boom, in whose
cylinder sgaces hydraulic fluid may be fed for turning
the boom relative to the frame.
A problem with booms for rock drilling units
is that the swing angle of a boom changes When the angle
of elevation of the boom changes, causing significant
widening of the swing angle of the boom at its extreme
height values and excessive lateral movement of the
boom. Consequently, in known solutions, the swing angles
of a boom are defined narrow enough for preventing
excessive turning of the boom. This again results in the
operating range of a boom being in some cases far too
narrow as the whole available width area cannot be
utilized in the mid-part of the boom because of problems
with the upper and lower angles.
The object of the present invention is to
provide an arrangement for eliminating the drawbacks of
known solutions and allowing optimal utilization of the
operating range of a boom. The arrangement of the
invention is characterized in that it comprises control
means for indicating the widest permissible swing angle
of a boom, that the control means are coupled to control
' a swing cylinder so that if the boom, when being lifted
or lowered, tends to turn outside the widest permissible
' swing angle, the control means let hydraulic fluid flow
into the cylinder spaces of the swing cylinder for
turning the boom to a reverse direction with respect to
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the turning movement caused by the lifting or lowering
movements, thereby preventing the boam from exceeding .
the widest permissible swing angle.
It is an essential idea of the invention that
the control means are coupled to the boom movably there
with and a relief valve is coupled to be controlled by
the control means, whereat, with the boom turning to a
predetermined swing angle, the control means control the
relief valve so that it feeds hydraulic fluid into the
swing cylinder of the boom and, correspondingly,
discharges hydraulic fluid therefrom for maintaining the
boom in this widest permissible position of the swing
angle when it 3s lifted or lowered farther into the same
direction, upward or downward, respectively.
It is an advantage of the invention that the
widest possible operating range may be defined for a
boom when it is essentially in the horizontal plane,
whereat, with the arrangement of the invention, the same
operating width is maintained for a boom both in its
upper and lower positions without the joints or other
parts of boom cylinders ending up in an unusual or
operationally impossible position. This allows maximum
boom coverage without problems of known solutions.
The invention will be described in greater
detail in the accompanying drawings, in which
Figures la and lb are s schematic top and side
view of a boom for a rock drilling unit, and the
arrangement of the invention mounted on a boom
structure,
Figure 2 schematically :shows a hydraulic
coupiingof the arrangement of the invention,
Figures 3a and 3b schematically show some other
applications of the arrangement of the invention.
Figures la and lb schematically show a boom 1
for a rock drilling unit, pivotally connected to a frame
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2 about a vertical shaft 3. The side of the boom 1
comprises a swing cylinder 4, connected at its ends by
joints 5 and 6 to the boom and, correspondingly, to the
frame 2 for changing the direction of the boom relative
to the frame 2 in a manner known per se. The other end
of the boom comprises a feed beam 7, connected by a
second vertical shaft 8 to the end of the boom for
turning the feed beam relative to the end of the boom
1. A swing cylinder 9, between the feed beam 7 and the
boom 1, is pivotally connected at its ends by joints 10
and 11. The swing cylinder 9 may be connected at its
feed beam 7 end either direct to the feed beam, to a
cradle of the feed beam, or in any other manner known
per se to operate between the feed beam and the boom.
By means of the swing cylinder 9, the direction
of the feed beam 7 relative to the boom 1 may be changed
about the shaft 8 in a manner known per se. The boom 1
is pivotally connected about a horizontal shaft 3'
relative to the frame 2 in a manner known per se, and
a tilt cylinder 4' between the boom 1 and the frame 2
is connected at its ends by joints 5' and 6' to the boom
and to the frame 2. At the other end of the boom 1, the
feed beam 7 is pivotally cougled about a second
horizontal shaft 8', and a tilt cylinder'9', between the
feed beam 7 and the boom 1, is pivotally coupled at its
ends by joints 10' and 11' for vertical turning of the
feed beam 7 by means of the cylinder, relative to the
boom 1, in a manner known per se. A control member 12
is coupled to turn with the boom 1 about the shaft 3 for
controlling the lateral adjustment of the boom when the
' boom 1 is turned vertically. Figure 2 describes in
greater detail the structure and operation of the
control member 12.
Figure 2 schematically shows the control member
12, essentially of a circular sector shape, coupled to
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turn with the boom 1 about the shaft 3. The control
member 12 comprises a slot I3 comprising a dowel pin 14.
The dowel pin 14 is coupled e.g. by a shank 15 to a
relief valve 16 utilized for controlling the lateral
position of the boom if the boom tends to turn into a
wider angle than the predetermined swing angle. The
relief valve comprises a hydraulic fluid line 17 and an
exhaust line 18 leading to a hydraulic fluid tank. The
swing cylinder 4 of the boom comprises over-center
valves 4a, which lock the swing cylinder hydraulically
immovable unless hydraulic fluid is fed into it and, in
case of overload, let the excess pressure out of the
cylinder space. Hydraulic fluid is fed into the swing
cylinder 4 via turning pressure lines 19a and 19b. The
turning pressure lines 19a and 19b are separately
connected via control valves 20a and 20b to the cylinder
spaces of the swing cylinder 4. With the boom 1 in a
normal position within permissi'bl'e swing angles, the
control valves 20a and 20b are in a position shown by
the Figures. The control lines of the control valves are
connected via shuttle valves 21a and 21b to control
pressure lines 22a and 22b, respectively, emanating from
the relief valve 16.
With the boom 1 within permissible swing
limits, it may be turned in a desired manner by feeding
hydraulic fluid into either of the turning pressure
lines 19a and 19b, whereat, when hydraulic fluid flows
via the control valve 20a or 20b to the second cylinder
space of the swing cylinder 4, hydraulic fluid is
correspondingly discharged from the other cylinder space
via the second turning pressure line. If the boom 1 '
reaches Sts widest permissible swing angle, the dowel
pi'n 14 comes into contact with tha edge of the slot 13,
and the relief valve 16 shifts so as to couple the
hydraulic fluid channel and correspondingly the exhaust
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line to the control pressure lines 22a and 22b for
preventing input of hydraulic fluid via the normal route
to the swing cylinder 4, and the swing cylinder 4 stays
at the widest permissible swing angle. When the boom 1
5 is at the widest permissible swing angle, it tends to
turn outward as the geometric position formed by the
cylinders changes when the boom is lifted or lowered,
and the boom tends to turn laterally because of the
lifting or lowering movements. In this situation, with
the control member l2 turning with the boom 1, the dowel
pin 14 comes into contact with the edge of the slot 13
thus causing the relief valve 16 to change its position.
If the boom is e.g. lifted upward so that it tends to
turn to the right as shown by arrow A in Figure 2, the
boom simultaneously pulls the control member I2 along
to the direction of arrow B. This causes the relief
valve 16 to move from the position shown in the Figure
to a position where hydraulic fluid from line 17 is
allowed to flow to the control pressure line 22a and
correspondingly the control pressure line 22b is coupled
to the exhaust line 18. This causes the hydraulic fluid
in the line 22a to direct the control valves 20a and ZOb
from the position shown in the Figure to the right so
that the control pressure line 22a is coupled via the
control valve 20a to the right cylinder space of the
swing cylinder 4 as shown in the Figure and to push the
piston to the left as shown by arrow C in the Figure for
compensating for the turning of the boom 1 to the
direction of the arrow A. As long as the swing angle of
the boom 1 causes the control member 12 to shift the
relief valve 16, hydraulic fluid is fed to the swing
cylinder 4. Correspondingly, hydraulic fluid from the
second cylinder space of the swing cylinder 4 is allowed
to flow via the control valve 20b to the control
pressure line and further via the exhaust line 18 to a
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hydraulic fluid tank. Correspondingly, if the boom 1
turns to the opposite direction thus reaching its swing
limit, the relief valve moves to the opposite direction
and leads the hydraulic pressure of the hydraulic fluid
line 17 via the control valve 20b to the swing cylinder
4 and the hydraulic fluid discharging therefrom
correspondingly via the control valve 20a to the exhaust
line 1$.
Figures 3a and 3b show an application where the
invention is electrically controlled_ In both Figures
a boom awing valve 23 is connected to the turning
pressure lines 19a and 19b, for controlling the turning
of the boom either manually or, automatically .in a
manner known per se, by feeding hydraulic fluid to one
'of the lines 19a or 19b and correspondingly by allowing
hydraulic fluid to flow from the other. In these
applications an electrical limit sensor is utilised for
indicating the swing angle of the boom 1, said sensor
being a switch or similar electrical sensor indicating
the specific permissible extreme angle of the boom.
Figure 3a shows a limit sensor 24, utilized for indic-
ating the turning of the boom to either lateral direc-
tion when it reaches the permissible swing angle. The
valve 23 is an electrically controlled valve, and when
the limit sensor 24 indicates the extreme angle of the
boom it starts to control the valve 23 so that it either
stops the hydraulic fluid flow or, with status quo
preserved, feeds hydraulic fluid to the swing cylinder
for turning the boom 1 to the opposite direction. With
the boom I turning to the reverse direction, the limit
sensor 24 stops controlling the valve 23. Figure 3b
shows a solution where two electrical limit sensors 24a
arid 24b are utilized, both of which indicate their
specific lateral direction. In case the boem turns to
either direction reaching the widest permissible swing
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angle, the limit sensor on that side indicates the swing
angle and directs the electrically controlled valve 23
to the reverse direction as long as the boom attempts
to turn to a lateral direction. Functionally the
solutions of Figures 3a and 3b are similar and the valve
23 is also functionally and structurally similar.
In the above description and in the drawings
the invention has been described only by way of example,
and it is by no means to be so restricted. The structure
of the control member and its coupling to the boom 1 may
be realized in several different manners; the member may
be simply e.g, a peg or a slot controlling the relief
valve in a desired manner. Other manners for the
coupling may also be used. E.g. instead of a mechanical
connection, an electrical connection may be utilized so
that the swing positions of the boom, or each position
separately, is indicated by an electrical sensor, which
also controls the functioning of the relief valve 16.
Similarly, different normal regulating valves and safety
and security components may be added to the cougling
without affecting the essential idea of the invention.
For the same reason obvious components known per se have
not been added to the Figures for clarity.
