Note: Descriptions are shown in the official language in which they were submitted.
CA 02824580 2013-08-23
WORK VEHICLE BOOM ASSEMBLY PROVIDING IMPROVED VISIBILITY
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] Not applicable.
STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
FIELD OF THE DISCLOSURE
[0003] This disclosure relates to work vehicles and booms for work vehicles
that
support and position implements attached thereto.
BACKGROUND OF THE DISCLOSURE
[0004] Work vehicles known as skidders are heavy-duty vehicles used in the
forestry
industry to gather and clear logs. Cable skidders use a winch line to wrap
around and
winch the logs together so that the skidder can drag them to the landing area.
Grapple skidders have a grapple mounted on a boom at the rear of the vehicle
that
the vehicle operator controls, using onboard controls and actuation systems,
to raise,
lower, and rotate the grapple as well as open and close the grapple tongs as
needed
to clamp around the logs that are to be dragged away by the skidder.
[0005] Grapple skidders generally come in one of three types based on the type
of
boom employed. The booms of grapple skidders are considered single function
booms if they have a single degree of freedom, in which the boom pivots about
a
single axis, typically parallel with the vehicle axles, to raise and lower the
grapple
above the ground. Dual function booms provide a second degree of freedom. Dual
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function booms have a boom support pivotally mounted to the vehicle chassis,
typically in parallel with the vehicle axles, to which the boom is pivotally
connected
about a second parallel axis that is raised above the vehicle chassis. Dual
function
booms give the operator the additional ability to control the reach of the
grapple
behind the vehicle. Swing booms pivot about a vertical axis so that the boom
can
swing from one side of the skidder to the other and thereby position the
grapple to the
sides of the vehicle.
[0006] A common concern with work vehicles having boom-mounted work
implements, including single function, dual function and swing booms, is the
ability of
the vehicle operator to see the implement and the work area behind the
vehicle, such
as in order to clamp the grapple tongs around the logs. As mentioned, the boom
and
grapple are typically mounted at the rear of the machine such that the
operator must
look over his shoulder or readjust the seat to even face the grapple. Yet even
then, in
conventional fixed boom assemblies the boom interferes with, if not almost
entirely
blocks, the operator's line of sight to the implement. The mounting position
and
height of the boom and the large, heavy-duty construction required for the
boom and
boom support components further exacerbate the problem of poor operator
visibility
to the area being worked. Furthermore, the additional elevated pivot
connection often
found in dual function booms creates another obstacle in the sightline between
the
vehicle cabin and the implement.
[0007] This disclosure addresses the aforementioned problems.
SUMMARY OF THE DISCLOSURE
[0008] An improved boom construction, and work vehicle having an improved
boom,
is disclosed that affords the vehicle operator a better line of sight to the
work tool
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implement and the area being worked. The boom mounts the implement at one end
and has a split end in which two branches angle outwardly away from each other
leaving an open space between the branches. The boom is mounted such that the
pivotal connection is located at the branches of the boom and the opening
extends
beyond the pivot axis of the boom. This arrangement creates a window for a
sightline
between the vehicle and the implement such that the vehicle operator can view
the
implement and work area behind the vehicle.
[0009] In one form, the boom can generally take a generally Y-shaped or
wishbone
configuration. However, other configurations which include an elongated body
and
widened end with a window opening are envisioned. The open space between the
branches of the boom creates a generally triangular area at least in part
forming the
window, which can have a greater dimension in the direction of the boom pivot
axis
than does the elongated body of the boom itself and can extend in the
direction of the
boom axis closer to the elongated body than the boom pivots.
[0010] The wishbone configuration also allows the pivots of the boom to be
spaced
apart in the dimension of the boom pivot axis greater than the corresponding
dimension of the elongated body of the boom. The boom pivots can be lugs in
which
each lug has a flange segment that is substantially parallel to the boom axis
along
which the elongated body extends and one more flange segments that are
substantially parallel to, and located near, an edge of the associated branch
section
of the boom.
[0011] Moreover, the boom can be of a hollow box construction or in any event
define
an interior passage extending down the elongated body of the boom to the
implement
attachment location. Similarly, the boom support can be of a hollow box
construction
having an interior passage such that a working line (e.g., electrical wires or
working
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fluid plumbing lines) can be routed through the interior passages of the boom
support
and the boom. The boom or the boom support can also have a bulkhead for
coupling
shorter working lines together. In this way electrical and plumbing lines can
be kept
free from entanglement and obstructing the operator's line of sight. The
shorter lines
are also easier to service and replace.
[0012] The boom can also mount a work light to illuminate the implement and
work
area. For example, the light can be located at an underside of the elongated
body of
the boom between the boom pivot axis and where the implement is attached. The
on-boom light thus further improves the operator's view of the implement and
work
area, particularly in no or low ambient light conditions.
[0013] Thus, in one aspect this disclosure provides a boom assembly for a work
vehicle which includes: a boom support providing a boom mount with spaced
apart
pivots defining a boom pivot axis; a boom having a with an elongated body
section
extending along a boom axis and first and second branch sections extending
from the
body section at acute angles on each side of the boom axis defining an open
space
therebetween, the branch sections having pivots pivotally coupled to the
pivots of the
boom mount along the boom pivot axis; and a boom actuator including a pair of
cylinders coupled to the branch sections of the boom at a side of the boom
pivot axis
opposite the body section to pivot the boom with respect to the boom support.
[0014] Another aspect this disclosure provides in a work vehicle having a boom
for a
work implement, a boom assembly which includes: a boom support arch providing
an
elevated boom mount with spaced apart pivots defining a boom pivot axis; a
boom
having a Y-shaped configuration with an elongated body section extending along
a
boom axis to a distal end where the work implement is attachable and first and
second branch segments extending from the body section at acute angles on each
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side of the boom axis defining an open space therebetween, the branch segments
having pivots pivotally coupled to the pivots of the boom mount along the boom
pivot
axis; and a boom actuator including a pair of cylinders coupled to the branch
sections
of the boom at a side of the boom pivot axis opposite the body section of the
boom to
pivot the boom with respect to the boom support arch.
[0015] Yet another aspect of the disclosure provides a work vehicle having a
dual
function boom assembly for a work implement in which the boom assembly
includes:
a boom support arch providing an elevated boom mount with spaced apart pivots
defining a boom pivot axis, the boom support arch having a pivotal mounting
connection to the work vehicle; a boom support actuator including a pair of
cylinders
to pivot the boom support arch about the pivot connection; a boom having a Y-
shaped
configuration with an elongated body section extending along a boom axis to a
distal
end where the work implement is attachable and first and second branch
sections
extending from the body section at acute angles on each side of the boom axis
defining an open space therebetween, the branch sections having pivots
pivotally
coupled to the pivots of the boom mount along the boom pivot axis; and a boom
actuator including a pair of cylinders coupled to the branch sections of the
boom at a
side of the boom pivot axis opposite the body section of the boom to pivot the
boom
with respect to the boom support arch.
[0016] Still other features of the improved boom will be apparent from the
following
description and accompanying drawings.
CA 02824580 2013-08-23
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1 and 2 are front and rear perspective views showing a work
vehicle in
the form of a grapple skidder having an example boom assembly according to
this
disclosure;
[0018] FIG. 3 is rear view thereof;
[0019] FIG. 4 is a left side view thereof;
[0020] FIG. 5 is an enlarged partial left side view thereof superimposed with
operator
sightlines shown in dot-dash and dashed lines;
[0021] FIGS. 6-10 illustrate the example boom in isolation, shown from the
bottom,
top, left side, rear and front views, respectively;
[0022] FIGS. 11-14 illustrate the example boom assembly mounted on the rear
chassis of the work vehicle, shown from the front perspective, left side, top,
and rear
views, respectively;
[0023] FIGS. 15-16 are front and rear views thereof with the example boom
assembly
in respective fully retracted and horizontal boom positions;
[0024] FIGS. 17-20 are partial left side views similar to FIG. 5 albeit
showing the
boom assembly in different pivotal positions and superimposed with a
consistent
horizontal sightline in dashed line and operator sightlines shown in dot-dash
lines;
[0025] FIG. 21 is an enlarged partial perspective view of the pivot
connections
between the boom and the boom support arch; and
[0026] FIG. 22 is a sectional view through line 22-22 of FIG. 21 showing one
of the
pivot connections between the boom and the boom support arch.
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DETAILED DESCRIPTION
[0027] The following describes one or more example constructions of a boom
assembly 30 and work vehicle 32, as shown in the accompanying figures of the
drawings described briefly above. Various modifications to the example
construction(s) may be contemplated by one of skill in the art.
[0028] Figures 11-14 show an example application of the boom assembly 30
incorporated into the work vehicle 32 which powers and controls an implement
attachment 34 through a bundle of electric and hydraulic working lines 36. In
the
example shown in FIGS. 1-5 and described herein, the work vehicle 32 is a
skidder
and the implement attachment 34 is a grapple. For simplicity a single machine
and
attachment are described herein as an example application. However, the boom
assembly 30 can be utilized with various work vehicles and implements,
including
with tractors and other agricultural, forestry or construction vehicles with
any
applicable implement attachment. As such, the terms "work vehicle" and
"implement"
are not limited to the skidder and grapple described herein.
[0029] Turning now to the example embodiment, the skidder 32 generally has an
articulating chassis 40 on a front end of which is mounted a cabin 42, engine
compartment 44 and front implement 46, shown as a stacking or decking blade,
and
on a rear end of which is mounted the boom assembly 30 which suspends the
grapple 34. The vehicle drive train is configured to couple power from the
engine to
,
the front and rear axles 50 to rotate the wheels 52. It should be noted that
any type of
suitable drive train can be used, including direct drive and final drive
systems, with
any suitable number of axles, and further that the wheels could drive tracks
rather
than mount tires as shown. The chassis 40 supports all other electric,
pneumatic or
hydraulic power subsystems, all engine cooling and exhaust subsystems, all
operator
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controls in the cabin 42 and all vehicle lighting subsystems. For example, the
chassis
40 mounts a hydraulic system, including a hydraulic reservoir and pump (not
shown),
that drives the boom assembly 30 and grapple 34 via hydraulic pressure
communicated to the associated actuator components via the working lines 36.
[0030] This disclosure pertains to the construction and operation of the boom
assembly 30, and in particular to the unique construction of the boom 60,
which gives
the operator in the cabin 42 a better sightline to the grapple 34 and the work
area
behind the skidder 32 as well as provides for additional benefits discussed
below.
Accordingly, the following will describe in detail the boom assembly 30
without also
describing the remainder of the skidder 32 or the construction of the grapple
34,
which will be generally understood by those of skill in the art of heavy
equipment and
machinery familiar with existing skidders and grapple attachments, such as
commercially available from Deere & Co. of Moline, Illinois.
[0031] The boom assembly 30 of the example skidder 32 shown in FIGS. 1-5 is a
dual function boom assembly, that is, it provides two degrees of freedom in
which the
grapple 34 can be moved above and beyond the rotation and articulation of the
grapple 34 itself. The example boom assembly 30 generally includes the boom
60, a
boom support arch 62, a boom actuator 64 and a boom support actuator 66. The
actuators 64, 66 for the boom 60 and boom support arch 62 can be any heavy-
duty
hydraulic cylinders, such as single and double acting telescoping piston
cylinders of
suitable displacement and stroke length.
[0032] As will be described in more detail below, the boom 60 suspends the
grapple
34 at a distal end thereof so that the grapple 34 can be maneuvered to a work
area
behind the skidder 32. The boom support arch 62 is mounted to the chassis 40
at a
pivot mount 68 generally at the level of the chassis 40, and the boom 60 is
mounted
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to the boom support arch 62 at an elevated pivot mount 70. From within the
cabin 42,
the operator controls the height of the grapple 34 primarily by activating the
boom
actuator 64 to pivot the boom 60 about the boom support arch 62 and controls
the
reach of the grapple 34 primarily by activating the boom support actuator 66
to pivot
the boom support arch 62, and thereby also the boom 60, about the chassis 40.
As is
known, the operator can further articulate the grapple 34 in position to clamp
against
the objects, such as logs and felled trees, that are to be dragged away by the
skidder
32. The grapple 34 itself can be any suitable conventional grapple mechanism,
such
as a heavy-duty hydraulic logging grapple having a grapple head 72 and a large
pair
of opposed grapple tongs 74. The grapple head 72 can include hydraulic
cylinders
(not shown) for actuating the grapple tongs 74 to open and close. The grapple
34
can mount to the boom 60 by a head joint and hydraulic motor assembly 76,
which
permits the operator to rotate the grapple 34 up to 360 degrees as needed to
properly
orient the grapple tongs 74.
[0033] Referring to FIGS. 6-10, the boom 60 itself can have a generally
wishbone
configuration that is symmetric about a central boom axis 80. Specifically,
the boom
60 can have an elongated body section 82 extending along the boom axis 80 to
the
distal end where the grapple 34 mounts. At the opposite end of the body
section 82
from the grapple 34, the boom 60 forks into two branch sections 84, which
extend
outwardly on each side of the boom axis 80. In the example construction, the
branch
sections 84 have outwardly angled segments 86 that extend at an acute angle to
the
boom axis 80 and straight segments 88 generally parallel with the boom axis
80.
[0034] The example boom 60 has a hollow box construction in which a top panel
90,
a bottom panel 92 and several side panels 94 are metal plates that are welded
together to form the wishbone configuration. The bottom panel 92 of the boom
60
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has a flange 96 at the distal end of the body section 82 for mounting the
grapple head
joint and motor assembly 76 that suspends the grapple 34. The top panel 90 has
a
removable cover and access opening 98 for accessing the electric and/or
hydraulic
working lines 36 to the grapple 34. The bottom panel 92 has an opening located
in
the body section 82 near the forked end for a work light 100. The bottom panel
92 has
additional openings 102, which can have compliant or rigid grommets or other
friction
and load dampening linings along their peripheries that reduce damage to the
lines,
to allow access to the interior of the boom 60. The hollow box construction of
the
boom 60 permits electrical and/or hydraulic working lines 36 to be routed
through the
interior of the boom 60 rather than along the exterior of the boom 60 where
they are
susceptible to damage and interfering with the operation of the skidder 32 and
grapple 34 or obstructing the operator's view of the grapple 34 and work area.
[0035] The branch sections 84 of the boom 60 each have two pivot locations,
namely
a pair of pivot lugs 104 extending substantially perpendicularly from the
bottom panel
92 at the angled segments 96 along a boom pivot axis 106, and a pair of
clevises 108
extending substantially perpendicularly from the straight segments 88. The
pivot lugs
104 can be formed to have two or more segments at an angle to each other. For
example, each pivot lug 104 can have a straight center flange segment 110 that
is
substantially parallel to the boom axis 80 and has an opening centered on the
boom
pivot axis 106 that receives a bushing or bearing 112. Each pivot lug 104 can
also
have front 114 and rear 116 angled end flange segments that extend near and
substantially parallel to respective inner and outer edges of the branch
sections 84.
Aligning the angled end segments 114, 116 with the edges of the branch
sections 84
reduces the localized strain at area of attachment of the pivot lugs 104 by
better
dispersing the strain down the length of the boom 60.
CA 02824580 2013-08-23
[0036] With reference to FIG. 6, a more precise description of the mounting
location
of the pivot lugs 104 will now be given. As shown, the pivot lugs 104, and in
particular the central segments 110 thereof, are located on the angled
segments 86 of
the branch sections 84 at opposite sides of the boom axis 80 centered on the
boom
pivot axis 106 at a distance "A", which is greater than the distance spanning
the short
dimension of the body section 82. Moreover, the opening of the center segment
110
of the pivot lug 104, which receives the bearing 112 and defines the boom
pivot axis
106, is located a distance "B" along the boom axis 80 in the direction away
from the
grapple mounting side of the boom 60 from the inner periphery 118 of an open
space
120 between the branch sections 84 of the boom 60. Thus, the open space 120
begins closer to the grapple end of the boom 60 than the pivot location of the
boom
60. Consequently, as will be described in more detail, for a set of pivot
angles of the
boom 60 about the boom pivot axis 106 above horizontal and the open space 120
provides or contributes to a window for a direct operator sightline from the
cabin 42 to
the grapple 34.
[0037] With reference to FIGS. 11-14, the boom 60 is mounted at an elevated
height
above the chassis 40 by the boom support arch 62, which can have the horseshoe
configuration shown. In this configuration, the boom support arch 62 has a
generally
straight cross-segment 122 between the upper ends of two upright segments 124
which can toe in slightly from top to bottom. Like the boom 60, the boom
support arch
62 has a metal plate, hollow box construction formed of front 126 and rear 128
horseshoe shaped panels with a plurality of side panels 130 welded between the
front
126 and rear 128 panels. Also, like the boom 60, the hollow box construction
of the
boom support arch 62 permits electrical and hydraulic working lines 36 to be
routed
through the interior of the boom support arch 62 rather than along its
exterior where
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they are susceptible to damage and interfering with the operation of the
skidder 32
and grapple 34 or further obstructing the operator's view of the grapple 34
and work
area. Also, the upper panel of the cross-segment 122 can have openings 132,
which
can have grommets or other friction and load dampening linings along their
peripheries, to allow passage of the working lines 36 between the interiors of
the
boom 60 and boom support arch 62. Furthermore, one or more of the side panels
130 can have a removable cover and access opening 134 for a bulkhead manifold
(not shown) for connecting together shorter lengths of hydraulic lines 36,
which
facilitates installation and repair of the lines.
[0038] The boom support arch 62 is pivotally connected to the chassis 40 about
a
boom support pivot axis 136 at the pivot mount 68, and the boom 60 is
pivotally
connected to the boom support arch 62 about the boom pivot axis 106 at the
elevated
pivot mount 70. Each pivot mount 68, 70 can be an assembly of mating lug
flanges
and clevises. In the illustrated example, clevises 138 are welded to the boom
support
arch 62 at the cross-segment 122 for pivot mount 70 and at the distal ends of
the
upright segments 124 for pivot mount 68. Mating lug flanges are welded to the
branch sections 84 of the boom 60 at pivot mount 70, as previously described,
and
also to the chassis 40 at pivot mount 68. Of course, the specific mounting
component, lug or clevis, could be interchanged. All four pivots of the pivot
mounts
68 and 70 can be operationally the same, and thus only one of the pivot
assemblies
will be described in detail.
[0039] With references to FIGS. 21 and 22, the left side pivot (isolated in
FIG. 22) of
pivot mount 70 includes the associated pivot lug 104 of the boom 60 and clevis
138 of
the boom support arch 62. The mating lug 104 and clevis 138 are joined by a
flag pin
140, which can be statically mounted in the clevis 138 along the boom pivot
axis 106
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so as not to rotate and on which the straight bore lug bearing 112 can rotate.
The
flag pin 140 can be secured by a split-ended retainer 142 that has an opening
144,
which fits into a mating annular groove near an end of the flag pin 140. The
retainer
142 can be bolted to the clevis 138 by a bolt 146 inserted through
corresponding
openings in the retainer 142 and clevis 138. Spacers 148 can be welded to the
inside
of the clevis 138 and/or to the outside of the pivot lug 104 to reduce play
along the
boom pivot axis 106. Additional shims or washers 150 can be mounted on the
flag
pin 140 between the fixed spacers 148 as needed to further shore up the
connection
and facilitate smooth pivoting action. The flag pin 140 can also have a
fitting 152
communicating with internal passages 154 leading to the bearing 112 for
applying
grease or other lubricant at the pin/bearing interface in situ and without
requiring
disassembly of the pivot.
[0040] Similar lug flange and clevis pivotal connections can be used for the
boom 64
and boom support 66 actuators. For example, with reference to FIGS. 11, 12 and
15,
a pair of inner pivot lugs 160 and a pair of outer pivot lugs 162 can be
welded to the
chassis 40, which mate with clevis ends of the cylinder pairs of the
associated
actuators 64, 66. Additional pivot lugs 164 can be welded to the front panel
126
along the upright segments 124 of the boom support arch 62, which pivotally
connect
with clevises at the piston ends of the cylinder pair for the boom support
actuator 66.
The piston ends of the cylinder pair for the boom actuator 64 can have rod
eyes or
trunnions that mate with the clevises 108 at the end of the boom 60. Because
the
clevises 108 are mounted at the ends of the widely spaced branch sections 84,
the
clevises 108 can be aligned with the pivot lugs 160 such that the cylinders of
the
boom actuator 64 can be arranged in parallel to each other on opposite sides
of, and
parallel with, the boom axis 80. The boom support actuator 66 has a similar
parallel
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cylinder mounting arrangement in which the pivot lugs 162 and 164 are
essentially
co-planar. This permits the actuators 64, 66 to be pivotally coupled to the
boom 60
and boom support arch 62 by straight-bore bushings or plain cylindrical
bearings,
rather than spherical bearings as would normally be required for out of plane,
non-
parallel cylinder mounting arrangements. Straight bearings and plain bearings
are
easier to lubricate, less complex and more durable than spherical bearings,
which
extends the operational life of the boom assembly 30 between maintenance
periods.
[0041] Having described the pertineot co;nponents of an example grapple
skidder 32,
the improvements in operator visibility of the grapple and work area that the
example
construction of the disclosed boom assembly 30 provides will now be described.
As
mentioned, the example boom assembly 30 is a dual function boom assembly that
permits independent pivoting about the boom pivot axis 106 and the boom
support
pivot axis 136. From within the cabin 42, the operator controls the height of
the
grapple 34 primarily by activating the boom actuator 64 to pivot the boom 60
about
the boom pivot axis 106 and the reach of the grapple 34 primarily by
activating the
boom support actuator 66 to pivot the boom support arch 62, and thereby also
the
boom 60, about the boom support pivot axis 136.
[0042] Figures 15 and 17 illustrate the boom assembly 30 in its home position.
For
the illustrated example, in the home position, the cylinders of the actuators
64, 66 are
fully retracted forward such that the boom support arch 62 is in its furthest
counter-
clockwise angular position (as viewed from the left side show in FIG. 17),
which
corresponds to an angle a of approximately 100 with respect to the chassis
40, or
horizontal if the chassis 40 is parallel to the horizon. In the home position,
the boom
60 is also in its furthest counter-clockwise angular position, which
corresponds to an
angle 13 of about 40 from horizontal, or with respect to the chassis 40 if it
is not
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horizontal. Also, in the home position the included angle y between the
intersection
of the centerline through the boom support arch 62 and the boom axis 80 is
about
60 . Figures 18-20 illustrate three of the numerous intermediate positions to
which
the boom assembly 30 can be pivoted, including the horizontal boom position
depicted in FIG. 20. The approximate values of the three angles a, f3 and y
mentioned above corresponding to the boom assembly 30 positions shown in FIGS.
17-20 are summarized in the table below.
Position a 13 Y H
FIG. 17 100 39 61 15.2"
FIG. 18 92 20 73 14.8"
FIG. 19 76 6 68 13.4"
FIG. 20 63 0 63 11.6"
The above table also provides approximate values of the vertical height "H",
as
notated in FIG. 15, of the visibility window created by the boom assembly 30
at the
four positions shown in FIGS. 17-20. As noted, the "H" values range from about
15.2"
to about 11.6" throughout the range of motion depicted in FIGS. 15-20.
[0043] It should be noted that the value "H" represents the vertical dimension
of the
open space above the boom support arch 62 through which an operator inside the
cabin 42 can view the grapple 34 without being obstructed by the boom 60. This
dimension includes the height of the air space between the top of the boom
support
arch 62 and the bottom of the boom 60, as in the position shown in FIGS. 16
and 20,
as well as any of the open space 120 between the branch sections 84 of the
boom 60
which adds to the visibility window when the boom 60 is in a suitable angular
position,
such as the home position shown in FIGS. 15 and17. The range of operator
sightlines through the visibility window are depicted graphically by the dot-
dash lines
in FIGS. 17-20. It should also be noted that the dimension "H" does not
include the
CA 02824580 2013-08-23
additional visibility window that is present beneath the cross-segment 122 of
the
boom support arch 62, such as represented by the lower operator sightline
(dashed
line) in FIG. 5.
[0044] As can be seen in FIGS. 15-20, the boom assembly 30 provides a
consistent
sightline "S" for the operator throughout the range of motion shown in FIGS.
15-20,
including from the home position of FIG. 15 to the horizontal boom position of
FIG.
20. The sightline "S" is depicted by the horizontal dashed line in FIGS. 17-20
and the
crosshair in FIGS. 15 and 16. As shown, the sightline extends from
approximately
eye-level of a seated operator inside the cabin 42 to the grapple 34. In each
position,
the sightline "S" is maintained at the same height from a common reference
point,
such as on the chassis 40 or the ground. This gives the operator not only a
direct
view of the grapple 34, but also a consistently positioned, centralized window
to look
through, thereby reducing the frequency and extent to which the operator would
be
required to crane his neck to view the grapple 34.
[0045] As mentioned, additional visibility, particularly toward the ground or
lower part
of the work area, as shown in FIG. 5, can be gained by angling the sightline
downward by the operator simply looking or tilting his head downward.
Adjusting the
sightline to angle downward from the cabin 42, would be particularly
advantageous
for viewing the grapple 34 should the boom assembly 30 be extended beyond the
FIG. 20 horizontal boom position, such as when the grapple 34 is to be used in
a
subterranean work area. Thus, even in that case a direct operator sightline
(albeit not
the same sightline "S"), exists between the cabin 42 and the grapple 34. Such
increased visibility throughout the range of motion is useful during operation
of the
grapple both pick up a load and to monitor the load as it is transported.
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[0046] It should also be noted that the boom assembly 30 provide benefits in
addition
to the improved visibility for the operator. For example, the wide pivotal
connection of
the boom 60 to the support arch 62 allows the boom assembly 30 to better
handle
torque loading applied to the boom 60 by the grapple 34. In addition, as
compared to
a corresponding wide pivot full-body boom, the presence of the open space 120
between the branch sections 84 reduces the weight of the boom, thereby
allowing for
improved energy efficiency and/or more cargo load weight. The wider
connections
and structures are more efficient and with less weight, and the wider stance
increases
the operational life of the bushings and pins at the pivots due to the lower
torque
loads passing through the pins.
[0047] The foregoing detailed description describes the subject of this
disclosure in
one or more examples. A skilled person in the art to which the subject matter
of this
disclosure pertains will recognize many alternatives, modifications and
variations to
the described example(s). The scope of the invention is thus defined not by
the
detailed description, but rather by the following claims.
17
