U.S. patent application number 11/585436 was filed with the patent office on 2007-10-18 for udd dragline bucket.
This patent application is currently assigned to ESCO Corporation. Invention is credited to Allison M. Daus, Steven D. Hyde, Aaron B. Lian.
Application Number | 20070240340 11/585436 |
Document ID | / |
Family ID | 41091721 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070240340 |
Kind Code |
A1 |
Hyde; Steven D. ; et
al. |
October 18, 2007 |
UDD dragline bucket
Abstract
A UDD bucket for a UDD mining operation provided with multiple
hoist connection points that alternative couple to the front and/or
rear hoist lines. The UDD mining machine includes a control system
that directs the movement of the bucket within a prescribed carry
envelope to limit unequal wearing of the hoist lines or minimize
the magnitude of rope loads. In one construction, the control
system directs the movement of the bucket with a range of motion
where the loads on the hoist lines are kept within a prescribed
variance of each other during the carry phase or most of the carry
phase of a digging cycle. The bucket will be moved by the mining
machine with the inventive control system so that, in the carry
phase, the loads applied to the front hoist line are within, for
example, 5%, 10% or 15% of the loads applied to the rear hoist
lines. This general equaling of the loads in the hoist lines
results in longer wear life for the front hoist lines, and
generally equal wearing of the front and rear hoist lines to enable
simultaneous replacement. The alternative connection points enables
the carry envelope to be altered.
Inventors: |
Hyde; Steven D.; (Portland,
OR) ; Lian; Aaron B.; (Portland, OR) ; Daus;
Allison M.; (Portland, OR) |
Correspondence
Address: |
ESCO CORPORATION
2141 NW 25TH AVENUE, P.O. BOX 10123
PORTLAND
OR
97210
US
|
Assignee: |
ESCO Corporation
Portland
OR
|
Family ID: |
41091721 |
Appl. No.: |
11/585436 |
Filed: |
October 23, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60791717 |
Apr 12, 2006 |
|
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|
Current U.S.
Class: |
37/398 |
Current CPC
Class: |
E02F 3/60 20130101 |
Class at
Publication: |
37/398 |
International
Class: |
E02F 3/60 20060101
E02F003/60 |
Claims
1. A UDD bucket comprising a cavity for receiving earthen material
therein, a front portion having a front digging edge, and a rear
portion opposite to the front portion, a front hoist connection in
the front portion of the bucket to connect a front hoist line to
the bucket to independently lift and lower the front portion of the
bucket, a first rear hoist connection in the rear portion of the
bucket to connect a rear hoist line to the bucket to independently
lift and lower the rear portion of the bucket, a second rear hoist
connection in the rear portion of the bucket to alternatively
connect the rear hoist line to the bucket so as to alter relative
loading between the front and rear hoist lines for operation in a
mine, and a drag connection for connecting a drag line to the
bucket for pulling the bucket in a digging operation.
2. A UDD bucket in accordance with claim 1 further comprising a
second front hoist connection in the front portion of the bucket to
alternatively connect the front hoist line to the bucket so as to
alter relative loading between the first and second hoist lines for
operation in a mine.
3. A UDD bucket in accordance with claim 2 which further includes a
bottom wall, a rear wall and sidewalls to define the cavity, and
wherein the first rear hoist connection is positioned forward of
the rear wall.
4. A UDD bucket in accordance with claim 3 wherein the second rear
hoist connection is positioned forward of the rear wall.
5. A UDD bucket in accordance with claim 1 which further includes a
bottom wall, a rear wall and sidewalls to define the cavity, and
wherein the first rear hoist connection is positioned forward of
the rear wall.
6. A UDD bucket in accordance with claim 5 wherein the second rear
hoist connection is positioned forward of the rear wall.
7. A UDD bucket in accordance with claim 1 which further includes a
pair of opposite sides, each said side including one said first
rear hoist connection and a one said second rear hoist
connection.
8. A UDD bucket in accordance with claim 1 wherein the rear portion
of the bucket includes two said first rear hoist line connections
each connecting to a separate rear hoist line, and two said second
rear hoist line connections alternatively connecting to the
separate rear hoist lines.
9. A UDD bucket comprising a cavity for receiving earthen material
therein, a front portion having a front digging edge, and a rear
portion opposite to the front portion, a first front hoist
connection in the front portion of the bucket to connect a front
hoist line to the bucket to independently lift and lower the front
portion of the bucket, a rear hoist connection in the rear portion
of the bucket to connect a rear hoist line to the bucket to
independently lift and lower the rear portion of the bucket, a
second front hoist connection in the front portion of the bucket to
alternatively connect the front hoist line to the bucket so as to
alter relative loading between the first and second hoist lines for
operation in a mine, and a drag connection for connecting a drag
line to the bucket for pulling the bucket in a digging
operation.
10. A UDD bucket in accordance with claim 9 which further includes
a pair of opposite sides, each said side including one said rear
hoist connection.
11. A UDD bucket in accordance with claim 10 wherein each said side
includes a second rear hoist connection in the rear portion of the
bucket to alternatively connect the rear hoist line to the bucket
so as to alter relative loading between the first and second hoist
lines for operation in a mine.
12. A UDD bucket in accordance with claim 1 wherein the front
portion of the bucket includes two said first front hoist line
connections each connecting to a separate front hoist line, and two
said second front hoist line connections alternatively connecting
to the separate front hoist lines.
13. A UDD bucket comprising a bottom wall, a rear wall and
sidewalls to define a cavity for receiving earthen material
therein, a front portion having a front digging edge and a rear
portion opposite to the front portion, a front hoist connection in
the front portion of the bucket to connect a front hoist line to
the bucket to independently lift and lower the front portion of the
bucket, a rear hoist connection in the rear portion of the bucket
forward of the rear wall to connect a rear hoist line to the bucket
to independently lift and lower the rear portion of the bucket, and
a drag connection for connecting a drag line to the bucket for
pulling the bucket in a digging operation.
14. A UDD bucket in accordance with claim 13 which further includes
a pair of opposite sides, each said side including one said rear
hoist connection.
15. A UDD bucket in accordance with claim 14 wherein each said side
includes a second rear hoist connection in the rear portion of the
bucket to alternatively connect the rear hoist line to the bucket
so as to alter relative loading between the first and second hoist
lines for operation in a mine.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to a bucket for a universal
dig and dump mining operation.
BACKGROUND OF THE PRESENT INVENTION
[0002] Universal dig and dump (UDD) mining operations involve the
use of dragline buckets that are controlled by UDD mining machines
having front hoist lines, rear hoist lines and drag lines, such as
disclosed in U.S. Pat. Nos. 6,705,031 and 6,826,466. While these
operations have provided benefits, they have been particularly hard
on the front hoist lines; i.e., the front hoist lines tend be
damaged or to wear much faster than the rear hoist lines. Such
wearing requires frequent replacement of the front hoist lines,
which results in the use of more hoist line and in frequent
downtime of the equipment. Moreover, the front hoist lines
frequently wear at unequal intervals from the rear hoist lines
resulting in even increased equipment downtime as the hoist lines
are replaced separately. The front hoist motors also have more
power, which can further lead to front hoist rope problems.
SUMMARY OF THE INVENTION
[0003] The present invention pertains to a UDD mining machine that
moves the bucket during the carry phase of a digging operation
within a range of motion that is predetermined at least in part by
the expected relative loads on the hoist lines.
[0004] In one aspect of the present invention, the bucket is moved
through a carry envelope for an improved UDD mining operation that
reduces the loading on the front hoist line and enhances the
efficiency of the mine.
[0005] In one aspect of the invention, a control system for a UDD
mining machine directs the movement of a loaded bucket within a
prescribed carry envelope to limit unequal loading of the hoist
lines. The control system directs the operator to move the UDD
bucket within the prescribed carry envelope or, alternatively, move
it directly under computer control. In one preferred construction,
the control system directs the bucket to be moved within a range of
motion where the loads on the hoist lines are kept within a
prescribed variance of each other during the carry phase or most of
the carry phase of a digging cycle. For example, movement of the
bucket will be directed by the inventive control system so that the
loads applied to the front hoist line are within, for example, 5%,
10% or 15% of the loads applied to the rear hoist line. This
general equaling of the loads in the hoist lines results in longer
wear life for the front hoist line, and generally equal wearing of
the front and rear hoist lines to enable simultaneous
replacement.
[0006] In another aspect of the invention, the control system for a
UDD mining machine directs the movement of the bucket within a
carry envelope defined by borders that widen, and which preferably
widen generally at an increasing rate, in a direction opposite to
the pulling of the drag line.
[0007] In another aspect of the invention, the control system for a
UDD mining machine directs the movement of the bucket in the carry
phase of a digging cycle to predominantly move under a prescribed
datum having a generally bell-shaped curve.
[0008] In another aspect of the invention, the control system for a
UDD mining machine directs movement of the bucket in the carry
phase of a digging cycle to move under a prescribed datum having a
slope that generally increases in a direction opposite the pulling
of the bucket during the digging phase.
[0009] In another aspect of the invention, the control system
directs the bucket during the carry phase to be moved predominantly
below an upper datum where the variation between the loads on the
hoist lines is at predetermined level.
[0010] In another aspect of the invention, the control system
directs the bucket to be predominantly moved during the carry phase
in a range of motion which on average loads the front hoist line at
a predetermined higher level than the loads on the rear hoist lines
to control the replacement time for the front hoist line.
[0011] In another aspect of the invention, the control system
directs the bucket to be moved during the carry phase in a range of
motion that depends on the expected relative loads on the hoist
lines.
[0012] In another aspect of the invention, the control system
directs the movement of the bucket in a carry envelope where the
overall magnitude of the loads on the hoist lines is reduced rather
than equalizing the hoist line loads.
[0013] In another aspect of the invention, a UDD machine commonly
has more motors supporting the front hoist lines than the rear
hoist lines. The control system can direct the bucket through a
carry envelope that maximizes the carrying power of the additional
motors. For example, the prescribed carry envelope may equalize the
loads carried by each motor rather than in each hoist line.
[0014] In another aspect of the invention, the bucket for a UDD
mining operation is provided with a plurality of pairs of
connection points for either or both of the front and rear hoist
lines. In this way, the carry envelope for a particular bucket can
be adjusted for a particular mining operation to maximize the
equaling of the hoist line wear. Multiple connection points can
also provide flexibility in accommodating and maximizing
performance.
[0015] In another aspect of the invention, the bucket for a UDD
mining operation is formed with a bottom wall, a rear wall and a
pair of sidewalls that are connected to define a front digging edge
and a bucket cavity. The bucket is provided with connection points
to facilitate the connection of front and rear hoist lines to the
bucket. At least one of the connection points for coupling the rear
hoist line to the bucket is located forward of the rear wall to
provide improved carrying of the bucket during use for certain
mining operations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic illustration of a UDD mining
operation.
[0017] FIG. 2 is a side view of a UDD bucket.
[0018] FIG. 3 is an enlarged side view of a trunnion for the UDD
bucket.
[0019] FIGS. 4-6 are graphs illustrating the operation of the
control system of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The present invention pertains to a UDD mining machine
wherein the bucket is controlled by independently operated front
and rear hoist lines as well as a drag line, such as disclosed in
U.S. Pat. Nos. 6,705,031 and 6,826,466, both of which are
incorporated herein by reference. Briefly, a UDD operation is a
dragline mining operation wherein the bucket is controlled solely
by the attachment of flaccid lines, such as ropes, cables or
chains. With reference to FIG. 1, a UDD operation 10 includes a
machine 12 situated at a base location that is typically at or near
ground level. The machine includes an elongate boom 14 that extends
over the mining site, which typically is a large pit. One or more
rear hoist line 16 extends downward generally from a free end 18 of
the boom to engage a rear portion of bucket 20. Similarly, one or
more front hoist line 22 extends downward from boom 14 to connect
to a front portion of bucket 20. Hoist lines 16, 22 operate
independently to carry and dump the bucket through each digging
cycle. One or more drag line 24 connects to a front portion of
bucket 20 to pull the bucket along the ground in order to fill the
bucket. The UDD machine 12 further includes a control system with
the appropriate motors, operator controls and computer for
controlling the movement of the bucket via the hoist and drag
lines. Ordinarily, other than the attitude of the bucket which is
automatically controlled by the computer, the operator manually
controls the movement of the bucket in a digging operation. For
convenience, this application will discuss an operation that
includes a single rear hoist line, front hoist line and drag line,
though operations with a plurality of each kind of line or a mixed
operation of single and multiple lines is possible.
[0021] In one common digging cycle, the bucket is first set on the
ground at the beginning of a pulling or digging phase in which the
drag line pulls the bucket along the ground to fill it. Once the
bucket is loaded, it is hoisted off the ground by the hoist line
and moved from the terminus end of the digging phase to the dumping
location, which is the carry phase of the digging cycle. The carry
phase is followed by a dumping phase where the front hoist line is
lowered relative to the rear hoist line to dump the earthen
material out of the bucket via its open front end. The bucket is
then returned, in a return phase, to the beginning of another
digging phase. In the present invention, the operation of the hoist
and drag lines in a UDD operation is directed by a computer 25 for
the control system. Of course, the computer may be the same unit
controlling the attitude of the bucket or a different unit.
[0022] While UDD operations provide better control of the bucket
than conventional dragline operations, they tend to suffer from
undue damage, loading and wearing of the front hoist line. As a
result, the front hoist line wears more quickly than the rear hoist
line and, in some cases, as much as three to four times as fast.
Premature wearing of the front hoist line results in increased
usage of hoist line and in excessive downtime for the mining
equipment. Moreover, the front and rear hoist lines frequently wear
at uneven intervals requiring separate replacement of the front and
rear hoist lines and even more equipment downtime.
[0023] It has been determined that such excessive and unequal
wearing of the front hoist line is caused primarily by unequal
loading of the hoist lines during the carry phase of a digging
cycle. Ordinarily, during the carry phase, the load on the rear
hoist line tends to be relatively constant. In many potential
positions during the carry phase, the pull of the drag line 24 will
tend to generate high loads on the front hoist line 22,
particularly as the bucket nears boom 14. When the bucket is at
lower positions within the mine, the loads on front hoist lines 22
tend to be less as compared to many positions when the bucket is
high in the mine. The pull of drag line 24 on front hoist 22 is
reduced in some positions and in others actually bears some of the
hoisting load to reduce the load on the front hoist line. While it
is preferable to maintain generally equal loading of the front and
rear hoist lines throughout the carry phase of the digging cycle,
it is typically more important to do so in the higher reaches of
the mine because of these higher loads.
[0024] It has been determined that loading of the front and rear
hoist lines, and particularly the front hoist line, is dependent on
several factors including the position of the bucket under boom 14,
the center of gravity of the loaded bucket (i.e., the loaded center
of gravity), and the location of the front and rear connection
points relative to the loaded center of gravity. A change of any of
these factors will result in more or less loading of the front
hoist line. As noted above, the loads on the rear hoist line,
though changing, generally tend to remain relatively constant
through most carry positions.
[0025] In one example, bucket 20 includes a bottom wall 26, a rear
wall 28, and a pair of sidewalls 30 coupled together to define a
front digging edge 32 and an inner bucket cavity. The digging edge
includes a series of spaced apart teeth 34 for penetrating the
ground and facilitating loading of the bucket when pulled along the
ground by the drag line 24. The drag line usually branches forward
of the bucket to connect to each side of the bucket. An arch 36
couples the upper front ends of sidewalls 30; although an arch is
not required. Front hoist line 22 is coupled to arch 36 via front
connection point 38. Rear hoist line 16, which usually branches
above the bucket, attaches to each sidewall 30 via rear connection
points 40. Nevertheless, connection points 38, 40 could be fixed to
other parts of the bucket, and buckets having other designs could
be used. As examples only, front connection points could be fixed
to sidewalls 30, such as disclosed in U.S. Pat. No. 6,705,301,
and/or the rear connection points could be fixed to the rear wall
28. In any event, the front connection point(s) 38 is fixed to a
front portion 44 of bucket 20 and rear connection points 40 are
fixed to a rear portion 46 of the bucket. Drag line 24 is coupled
to the front edges 48 of sidewalls 30 via drag connection points
50.
[0026] During use, the bucket is loaded with earthen material in
each digging phase. While the loaded center of gravity may shift
slightly from load to load, an average loaded center of gravity 52
can be determined for each particular bucket. The loaded center of
gravity 52 is also a factor of the density of the material to be
gathered as denser loads will tend to shift the center of gravity
rearward. The location of connection points 38, 40 can be
determined in a two-dimensional format (i.e., height and length)
relative to the loaded center of gravity 52. With these three known
location points 38, 40, 52, the loads carried by each hoist line
16, 22 can be determined and mapped for all carry positions (i.e.,
positions where the bucket may be in a carry phase of a digging
cycle) within the mine site. It has been determined that relatively
equal loading of hoist lines 16, 22 can be achieved when the bucket
is maintained within a prescribed carry envelope 54.
[0027] In one example, front hoist line 22 is coupled to front
connection point 38 and rear hoist line 16 is coupled to rear
connection points 40a. In the carry phase of a loaded bucket, hoist
lines 16, 22 will carry generally the same load (i.e., within about
5% of each other) if the bucket's loaded center of gravity 52 is
kept within a carry envelope 54a defined by an upper datum or
border 56a and a lower datum or border 58a. With reference to FIG.
4, the zero point of the plot is the base position of boom 14,
i.e., where boom 14 is coupled to the base 13 of machine 12. The
vertical and horizontal axes in the plot represent the vertical and
horizontal distances the bucket may be relative to the zero point.
As can be seen (FIG. 4), in this case, upper border 56b has a
curved, generally bell-shaped configuration. In this example, the
slope of the curve generally increases as the border extends away
from the zero point and toward free end 18 of boom 14. Further,
carry envelope 54a generally widens and, in this example, generally
at an increasing rate as it extends away from machine 12 base 13.
Borders 56, 58 extend into and out of the paper of the plot in FIG.
4 to control the lift of the bucket irrespective of the lateral
swinging of boom 14.
[0028] As one illustration, if the terminus of the digging phase
locates bucket 20 at point 60, bucket 20 will be directed by
computer 25 for the control system to follow a carry path to the
dump site 61 that stays beneath upper border 56a to ensure that the
loads in each of the front and rear hoist lines remain relatively
equal; i.e., the control system would direct the operator to move
the UDD bucket within the prescribed carry envelope (e.g., with a
light indicator or other indication of when the bucket is outside
of the prescribed carry envelope). Alternatively, the bucket could
be moved directly under computer control. As can be appreciated,
this carry path 62 from point 60 to the dump site 61 (one example
illustrated in FIG. 4) will have an axial configuration (lateral
motion of bucket 20 is not shown in the plot) that is generally
bell shaped so that the bucket generally moves more horizontally in
the earlier portion of the carry phase and generally more vertical
in the later stages of the carry phase. The actual path may vary
from what is shown depending on various factors such as the swing
speed and swing angle. In the past, it was common for the bucket to
generally follow a carry path 64 from point 60 to dump site 61 that
was axially linear to reduce the overall length of travel. While
the distance to the dump site is lessened, it causes the bucket to
move outside of carry envelope 54a, i.e., above upper border 56a,
and to thereby apply higher loads to front hoist line 22 as
compared to rear hoist line 16. This repeated additional loading
causes front hoist line 22 to wear out more quickly than rear hoist
line 16.
[0029] The position of carry envelope 54 can be adjusted in the
mine site by changing the position of one or more of the connection
points 38, 40. In one example, front connection point 38 remains
unchanged, and rear connection point 40 is moved rearward from
location 40a to location 40b. As seen in FIG. 3, connector 66 can
be attached via a pin 68 to hole 70 to define a first connection
point 40a or to hole 72 to define a second connection point 40b
rearward of the first connection point. Of course, other ways of
connecting or changing the connection points could be used. By
moving rear connection point 40 rearward to location 40b, the carry
envelope 54 drops relative to the zero point so that upper and
lower borders 56, 58 are lower relative to boom 14 and lower into a
mining pit (FIG. 5). As with the first connection points 38, 40a,
these second connection points 38, 40b define a carry envelope 54b
with an upper border 56b and a lower border 58b. Further, the carry
envelope 54b generally widens, and in this example, generally at an
increasing rate as it extends axially away from machine 12. The
carry path for bucket 20 with this second set of connection points
38, 40b is directed by the control system to stay between borders
56b, 58b so that the loads on hoist lines 16, 22 remain within
about 5% of each other. This connection arrangement for this bucket
may be preferred in a deeper mine site. Moreover, the connection
points could be selectively chosen for a bucket that is designed
for a particular mine in order to maximize the ability of the
bucket to travel within the preferred carry envelope for that mine
or mine plan. When designing the connection points for a bucket to
be used in a particular mine site, greater attention will
preferably be paid to the expected movement of the bucket through
the higher regions of the mine. In a preferred embodiment for many
mines, the rear connection points 40 are located forward of the
rear wall 28 of the bucket to provide a more optimal carry
envelope. Nevertheless, rear connections could be along rear wall
28.
[0030] As can be appreciated, the position of the carry envelope 54
can be adjusted up or down within the mine or its shape changed to
narrow or widen depending on whether connection points 38, 40 are
moved rearward/forward or up/down relative to the loaded center of
gravity 52. Irrespective of these changes, computer 25 for the
control system, with the proper input of data, will direct the
movement of the bucket for the carry phase to stay within the
prescribed carry envelope to the dump site. The carry envelope will
generally be defined by upper and lower borders 56, 58 that diverge
generally at an increasing rate as the carry envelope extends away
from machine 12. Upper border 56 in many cases will generally have
a configuration that resembles a bell shape (i.e., that flares
upward at the outer range of the bucket's motion). The control
system will often direct the bucket to move primarily in a
horizontal direction in early portions of the carry phase and
primarily in a vertical direction in later phases of the carry
phase. Additional connection points can also be added to bucket 20
to provide further variations in the carry envelope. These
additional connection points may be front and/or rear connection
points.
[0031] At times, however, a mine will have a certain layout that
precludes the bucket from moving solely within a carry envelope
wherein the loads on the hoist lines 16, 22 are kept generally
equal (i.e., within about 5% of each other). This may occur, for
example, when the mine pit is deeper than the operating carry
envelope 54 so that the bucket ends its digging phase below lower
border 58. It may also occur, for example, when the dump site is
higher than carry envelope 54 so that the bucket must travel above
the upper border 56 to dump its load. In these cases, the control
system directs the bucket to move predominantly within the desired
carry envelope 54 so that the application of higher loads on the
front hoist line is minimized. Under such circumstances, if the
bucket included multiple connection points, the hoist lines would
preferably be set to enable movement of the bucket beneath the
upper datum 56 even if it meant substantial movement below the
lower datum because of the difference in the magnitudes of the
loads on the front hoist line at these different positions in the
mines.
[0032] Moreover, due to higher loads on the front hoist line in
certain higher regions of a mine as compared to the lower regions,
the control system can be set to direct the movement of the bucket
along a carry path that is kept predominantly beneath an upper
datum 56 without regard to a lower datum 58. Under these
parameters, the upper datum is defined in the same way, i.e., the
boundary where the load on the front hoist line is within a
predetermined load differential (e.g., within 5%, 10%, etc.) as
compared to the load expected on the rear hoist line.
[0033] Operation outside of a carry envelope that ensures generally
equal loading of hoist lines 16, 22 may also occur, for example,
when a bucket has only a single set of connection points that may
not be able to maximize efficiency for a particular mine. In these
cases, it may be necessary to operate the bucket for substantial
periods outside of this desired carry envelope. In such cases, the
control system can be set to direct the movement of the bucket
within or at least predominantly within a carry envelope where the
front and rear hoist lines are kept within a prescribed load
percentage of each other which may be greater than a 5%
difference.
[0034] For instance, with reference to FIG. 6, carry envelope 54c
for a particular bucket, with borders 56c, 58c, defines a range of
motion for the bucket where the loads on hoist lines 16, 22 remain
within about 5% of each other. The particularities of the mine may
dictate that for a particular bucket substantial portions of the
carry phase may need to occur outside of carry envelope 54c. In
such cases, the control system can be set to direct the movement of
the bucket within or predominantly within a carry envelope 54d with
borders 56d, 58d where the loads on hoist lines 16, 22 are kept
with a range of about 10% of each other. Alternatively, the control
system could be set to direct the movement of the bucket within a
carry envelope 54e with borders 56e, 58e where the loads on hoist
lines 16, 22 are kept within 15% of each other. As can be
appreciated, the control system can be set to dictate that the
hoist lines stay within a certain prescribed load percentage of
each other or as closely as possible to the desired variance to
keep hoist line loads as close as possible. Such control alleviates
as much as possible under the given circumstances unequal loading
of the hoist lines and the premature wearing of the front hoist
line.
[0035] There are times also when it may be desirable to operate the
UDD machine to balance the speed of the digging operation against
the frequency of replacing the front hoist line. For instance, the
digging cycle may be lengthened by having the control system direct
the bucket to move in a range of motion where the loads in the
front and rear hoist lines are predominantly within 5% of each
other during the carry phase. As an alternative, the operator may
set the control system to direct the movement of the bucket along a
path where the loads in the front hoist line are within a
predetermined difference of the loads in the rear hoist line by
more than 5% in order to shorten the digging cycle and increase the
production of the machine even if not required by the mine
layout.
[0036] In one example, the bucket is directed to move predominantly
(at least in the upper regions of the mine) along a carry path
where the load on the front hoist line is about 15% higher than the
load on the rear hoist line. Further, the control system can be set
so that the load on the front hoist line is kept within a certain
variation of the carry path that approximates a 15% difference in
the front and rear hoist line loads. For instance, the bucket can
be moved within a range of motion wherein the hoist line loads vary
upward or downward 5% (or other value) from the prescribed
path--that is, the bucket predominantly moves within a range of
motion where the load on the front hoist line is 10-20% higher than
the loads on the rear hoist line. In this way, the operator can
balance the downtime caused by replacing the front hoist line with
the speed of the digging cycle in an effort to maximize the overall
production of the mine.
[0037] In another example, the control system can be set to permit
even higher variations in hoist line loads (i.e., more than 15%)
provided sufficient shortening of the digging cycle is gained. In
other words, the overall production of the UDD machine mining can
be maximized in some operations by accepting more frequent
replacements of the front hoist lines and achieving a shorter
digging cycle. The control system can achieve optimum bucket
movement during the carry phase by factoring the duration of the
digging cycle, the output production of each digging cycle, the
variations in loads between the hoist lines, and the downtime
caused by replacement of the front hoist line.
[0038] Also, in certain mines, the front hoist line suffers
abrasion wear near connection point 38 so that the terminal end of
the front hoist becomes unacceptably worn even though the remainder
of the hoist line has not worn as a result of the hoist loads. In
such cases, the worn end of the front hoist line can be cut off and
the front hoist line reattached in order to lengthen the use of the
front hoist line, i.e., until the overall length of the front hoist
line becomes too short to be used. Under these circumstances, the
control system may be set to direct bucket movement along a path
where the wearing of the hoist line due to uneven loading of the
front hoist line corresponds with the time in which the front hoist
line needs to be replaced due to shortening caused by abrasion
wear. In this way, the operator may be able to shorten the time for
the digging cycle and control front hoist line wear caused by hoist
loads to correspond to the time when the front hoist line would
need to be replaced for other reasons such as shortening caused by
abrasion wear.
[0039] As discussed above, the operation of the drag line affects
the loads on the hoist lines. In another alternative, the bucket
may be moved along a carry envelope to minimize the overall loads
on the hoist ropes rather than equalizing the loads in the front
and rear hoist lines.
[0040] Also, as discussed above, it is common for UDD machines to
have more motors supporting the front hoist lines than the rear
hoist lines. As an alternative, the bucket can be directed to move
through a carry envelope that generally equalizes the loads carried
by each motor rather than in each line.
[0041] Also, in a mixed line operation, e.g., where two front hoist
lines are used but only one rear hoist line, the bucket can be
moved through a carry envelope where the loads in each line are
generally equal (i.e., where the overall load on the front hoist
lines is twice the load in the single rear hoist line).
[0042] Various other embodiments as well as many changes may be
made without departing from the spirit and broader aspects of the
invention as defined in the claims.
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