Note: Descriptions are shown in the official language in which they were submitted.
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VERTICAL LIFT LOADER BOOM
BACKGROUND OF THE INVENTION
The present invention relates to loader boom
assemblies for self-propelled loaders which are
controlled to maintain the forward ends of the boom
assembly in a generally vertically linear path throughout
a substantial portion of the upward travel of the boom
assembly.
Loader boom assemblies which provide a
generally vertical movement of a bucket used for lifting
material have been used. For example U.S. Patent
4,355,946 illustrates a lift arm control linkage
structure for a loader which uses a long lift arm support
link at the rear portions of the loader boom assembly, to
provide an altered upward path of a front bucket, and at
the same time provides bucket leveling.
U.S. Patent 3,215,292 issued to Halls on
November 2, 1965 illustrates guide links which operate to
cause lift arms of a loader to extend out at the same
time they are raised. However, in this unit the bucket
continually moves outward Prom the supporting machine as
the bucket raises, rather than moving on a generally
vertical path in the upper portions of the range of
movement.
SUMMARY OF THE INVENTION
The present invention relates to a boom
assembly for a loader which comprises a pair of lift
arms, each including a pair of articulated links which
are controlled in movement as the lift arms are raised to
cause the outer ands of the lift arms to move generally
vertically and substantially linearly when the lift arms
are raised beyond a horizontal position. The articulated
links of each lift arm include a main forwardly extending
lift arm link or section and a rear, substantially
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shorter lift arm link or section which has one end
pivoted to the main lift arm link or section and the
other end pivoted to the self propelled loader frame.
The path of movement of the main lift arm
sections is partially controlled by a control link that
is connected to the self propelled loader frame at a
forward end of the frame and to the lift arm main section
of the respective lift arm. The lift arms are raised by
operating hydraulic cylinders or actuators which react
forces between the main lift arm sections and the loader
main frame. As the boom assembly is raised the rear lift
arm link first is controlled to pivot about its pivot at
the main loader frame so as to move the other or first
end of the rear link which is pivoted to the main lift
arm link rearwardly under control of the control link.
After the bucket at the forward end of the boom assembly
is about level with the pivot of the rear lift arm link
to the loader main frame the one end of the rear lift arm
section or link starts to move forwardly as the boom
assembly is raised further, and the main lift arm
sections also move forwardly so that the rear and main
lift arm links or sections unfold as the boom assembly is
raised, to keep the forward ends of the l~.ft arms and
bucket moving in a generally vertical path throughout the
range of higher movements of the lift arms forming the
boom assembly.
This positions the bucket support at the front
ends of the lift arms for easier dumping of material into
a truck, for example, and has the advantage of not having
the forward ends of the lift arms move rearwardly in an
arc during the upper portions of lift movement of the
lift arms.
Both sections of each loader lift arm, the
hydraulic actuator and the control link for the
respective lift arm, are made to be in a common plane so
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that the lateral dimensions of the operators compartment
do not have to be changed from existing dimensions of
skid steer loaders with conventional booms.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic side elevational view
of a skid steer loader having a loader boom assembly made
according to the present invention installed thereon with
parts broken away;
Figure 2 is a side elevational view of the
loader of Figure 1, taken from the opposite side;
Figure 3 is a part-schematic side elevational
view, showing a bucket and boom assembly in a plurality
of raised positions to illustrate the path of movement of
the outer ends of the boom assembly and a supported
bucket; and
Figure 4 is a schematic perspective view of the
loader boom assembly shown in Figure 1 with the skid
steer loader plain frame also shown, but with other parts
removed for sake of clarity.
~FmATr,Fr~ DESCRIPTION OF THE PREFE ED EMBODIMENTS
A loader assembly indicated generally at 10,
made according to the present invention, is mounted onto
a skid steer machine or prime mover 12 that has a main
frame 14 that extends longitudinally in fore and aft
direction, and is supported suitably on front and rear
wheels 16. Wheels 16 are driven in a suitable manner
through a drive train supported on the main frame ~14,
from an engine (not shown) in an engine compartment 15
mounted directly behind an operator's compartment
indicated schematically at 18. Frame uprights 20 at the
rear portion of the main frame are used for supporting
the loader 10. Each of the uprights 20 comprises a part
of spaced apart plates.
It is known that when conventional loader
booms, mounted at a single pivot axis to the loader frame
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are raised and lowered, the outer forward ends travel in
an arc, and when the boom starts to raise, there is some
forward movement of a supported bucket and, after the
pivoting boom goes over center, there is a substantial
amount of rearward movement of the bucket, as well as
upward movement, which tends to shorten the forward
"reach" of a bucket with the boom assembly in a raised
position.
The main frame 14, frame uprights 20, the drive
wheel configuration, fenders 22, and wide operator's
compartment 18 are all features of the standard skid
steer loaders. The operator's compartment extends
laterally across the entire main frame. The operator's
compartment extends substantially the full width between
the inner plates of frame uprights 20 and fenders 22 (see
Figure 4). The present articulated boom is designed to
fit onto the basic construction of the main frame,
uprights and wide cab while permitting the usual access
to service the machine in the same manner. An engine
compartment 15 is immediately behind the compartment 18
and the engine access door or panel 15A can be opened in
the same manner as on existing machines because of the
lack of interference from the rear links 32 and clearance
of cross member 36 due to use of high pivots 40.
The high rear pivot of existing machines is
maintained, in arder to accomplish the purposes of using
the basic loader design of conventional radius arc booms.
Skid steer loaders of the general type shown
herein are well known and are manufactured by the Melroe
Company, a business unit of Clark Equipment Company of
Fargo, North Dakota, and are marketed under the
registered trademark BOBCAT.
The loader 10 includes a lift boom assembly 24,
which is, in the preferred embodiment, a twq section
boom. The two section boom includes a main lift arm
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assembly 26 and a rear lift arm link assembly 28, which
are pivotally mounted together. The main lift arm
assembly 26 includes a pair of laterally spaced main lift
arm, links or sections 30, and a pair of rear or second
lift arm links or sections 32. The main lift arm links
30 are on opposite sides of the main frame connected with
suitable cross members at the forward ends thereof, for
example with a cross member shown at 34, and the spaced
rear lift arm links 32 on opposite sides of the main
frame are connected together with a suitable cross member
36. The main lift arm assembly 26 has forward and rear
ends, and at its rear end the main lift arm sections are
each pivotally connected with suitable pivot pins 38,
forming a pivot axis, to first ends of the rear lift arm
links 32. The connection is made so the main lift arm
sections 30 and the rear lift arm links 32 lie on a
common plane along the side of the operators compartment.
In addition, each of the rear lift arm links 32
is pivotally connected on suitable pins 40 forming a
pivot axis to the respective frame uprights 20, adjacent
the rear portions of the main frame 14, and at the upper
portions of the upright and between the plates forming
the respective frame uprights 20. The axis of the pins
40, which define the pivoting axis of the rear lift arm
link assembly is raised a substantial distance above a
supporting surface indicated generally at 42. The main
lift arm sections 30 include downwardly extending forward
arms 44 thereon, which extend downwardly and forwardly,
just ahead of the forward wheels 16, with the lift boom
assembly 24 in a lowered position. At the forward ends
of the main lift arm sections 30 there is an attachment
pin 46 which defines a pivot axis for supporting a
working implement. As shown, the working implement is a
bucket 48 that is supported on a subframe 50. The
aubframe in turn is pivotally mounted on the pins 46, and
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is controlled by a tilt cylinder or actuator illustrated
schematically at 52, in a conventional manner. The tilt
cylinder 52 is connected at its based end to a support 53
which is mounted on cross member 34. The subframe 50 is
an attachment frame that is sold by Melroe Company, a
business unit of Clark Equipment Company, located at
Forgo, North Dakota, under the trademark BOB-TACFi. Of
course, any desired mounting far the implement or bucket
48 can be utilized, and in most instances there is a
defined point such as the axis of pin 46 or the front lip
of the bucket 48 that can be used for determining the
path of movement of the forward ends of the main lift
arms 30 during raising and lowering motion.
In this form of the invention, the main lift
arm sections or links 30, have control arms 54 fixed
thereto, at a location spaced forwardly from the pivot
pin 38. The control arms 54 are made of two spaced
plates and extend downwardly along the sides of the
operator's compartment 18, as can be seen, to a location
just above the fenders 22. Hydraulic actuator or
cylinder attachment plate sections 56 are secured to the
main lift arm section 30 on each side of the boom
assembly in a suitable manner, or can be part of the
plates forming control arms 54.
A separate double acting hydraulic actuator or
cylinder assembly 58 is mounted on each of the sides of
the main frame, and has a rod that is extendable~and
retractable. The rod has a rod end that is connected
with a suitable pin 60 between the respective spaced
plates 56. The base end of each actuator or cylinder 58
is connected with a suitable pin 62 to the main frame 14
and, as shown, is located between the plates forming
uprights 2'0. It should be noted that the base end pin 62
for the double acting hydraulic actuator or cylinder 58
is substantially lower than the pivot pins 40. The
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actuator extends upwardly and forwardly from the pivot
pin 62 to pin 60n.
A control link, which in the form of the
invention is a fixed length or rigid link, is indicated
generally at 66. There is a rigid control link on each
side of the main frame 14, and thus there is a separate
control link 66 for each of the lift arm of the boom
assembly. Each of the links 66 has a forward end
pivotally mounted with a suitable pin 68 to a bracket
fixed on the respective fender 22 and thus to main frame
14 of machine 12. The opposite end of the rigid link 66
is connected with a suitable pin 70 to an end of the
respective control arm 54 on each of the main lift arm
sections 30 and is positioned between the plates forming
the respective control arm 54.
Each link 66 is substantially horizontal with
the boom assembly 24 in its lowered position. When
working with a bucket and the like, there is a rearward
force on the boom assembly during the loading of the
bucket. The horizontal links 66 are substantially
parallel to the direction of rearward force and will tend
to hold each of the individual main lift arm sections 30
and rear lift arm links 32 from rearward movement. Part
of this rearward load of course will also be transferred
through the pins 38 to the rear lift arm links 32 and
thus to the pivot 40 on the frame uprights, but With the
articulated lift arms, that is, two lift arm sections
pivoted together, there would be a tendency to cause
folding of the main lift arm sections and rear lift arm
links from horizontal load vectors acting rearwardly
against the pin 46. The links 66, actuator 88, the main
lift arm section 30, and the rear lift arm section or
link on each side of the boom assembly lie in a common
plane to save lateral space and to fit existing skid
steer machines without reducing the width of the
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operator°s compartment or increase the overall width of
the machine.
The actuators or cylinder assemblies 58 can be
operated using a valve and a source of hydraulic pressure
(not shown) to raise the boom assembly 24 to a raised,
dumping position. As the boom assembly raises, the path
of travel of the axis of the pin 46, or front edge of the
bucket will define a substantially vertical path
throughout the upper part of the working range used for
dumping of buckets. Referring to Figure 1, the boom
assembly 24 is shown at its lowered position. In Figure
3, the path of movement of the pin 46 is illustrated, arid
after the pin 46 reaches a height above the support
surface 42 substantially equal to the level of the pin 40
(as shown by a horizontal dashed line in Figure 3),
instead of moving on an arc rearwardly at the same time
that the lift arms are raised further, the axis of the
pin 46 moves substantially vertically to the full raised
position of the lift arms. The tilt cylinder 52 can be
operated as desired for tilting the subframe 50 and the
bucket 48 about the axis of pins 46, in the usual manner.
It also follows that in any particular tilted position of
the bucket 48, each point of the bucket, such as the
leading edge, will move along a path corresponding to the
path of the axis of the pin 46.
In the lowered position of the boom assembly
24, the main lift arm section or link 30 and the rear
lift arm section or link 32 on each side of the loader
form an included acute angle between the center line of
the rear link 32, between the axes of pivot pins 38 and
40, and the line between the axes of pivot pin 38 and pin
46. This included angle is represented by the double
arrow 74. As the lift cylinder or actuator 58 is
operated to start to raise the boom assembly 24 and,
therefore, the bucket 48, the included angle represented
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at 74 will first decrease as the rear lift arm links 32
will be forced to move rearwardly by the rigid link 66,
which pivots about pin 68 in an upward arc.
The control arm 54 positions the pivot pin 70
for the rear end of link 66 in a location such that
rearward movement of the lift arm link 32 occurs as the
arms swing. Pin 46 then moves upwardly along a path 47
that is shown in Figure 3, and when the cylinder or
actuator 58 has been extended to a point where the boom
assembly 24 is about one-third of its total upward travel
the included angle indicated by arrow 74 stops
decreasing, and then starts increasing again as the two
lift arm sections, comprising the main lift arm section
or link 30 and the rear lift arm section or link 32 start
to unfold as the end of link 66 moves forward on an arc.
The effective length of the boom assembly 24 from pivot
pin 40 to the front end increases during the upper two-
thirds of its upward travel to cause the vertical path of
movement of the pin 46 and associated parts of the
bucket. The rigid control link 66 thus controls the path
of pivotal movement of the pivot pin 38 as lift arm link
32 pivots about the pin 40. By proper selection of the
link geometry, including the length of the link 66 to be
of a substantial length, and approximately twice the
length of the rear lift arm link 32, and keeping rear
lift arm link 32 much shorter than lift arm link or
section 30, the desired path of travel of the pin 46~and
bucket 48 can be achieved.
The same path of travel is followed when the
lift arms are lowered, because the control link 66 is
fixed in length. The present boom assembly achieves the
objective of having a longer reach in the upper portions
of the path of movement of the boom assembly so that it
is easier to dump a bucket into a truck, and also that it
is easier to make a pile that is higher, while
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maintaining the advantages of having a high pivot boom
point 40 that is present in existing skid steer loaders,
improved lifting capacity, and still having a compact
loader which is as maneuverable as the prior skid steer
loaders.
The plane defined by the axes of pins 68 and 70
is above the axes of the pin 62 for the lift cylinders or
actuators 58, and the pin 70 is rearwardly of the pin 68
so that from the generally horizontal position of link 66
with the boom lowered, the pin 70 will move upwardly and
forwardly which will cause the rear link 32 to first move
rearwardly. The axis of pin 70 crosses a plane defined
by the axis of pins 68 and 38 and goes "overcenter" as it
raises. At a selected raised position of the main lift
arm sections, the rigid link 66 will cause the rear or
second lift arm links to start to move forwardly as the
main lift arm sections are further raised, again causing
the included angle indicated by arrow 74 to start to
increase. The effective length of the boom assembly
comprising the main lift arm sections or links 30 and the
rear lift arm links 32 increases as raising continues.
It should be noted that the link 66 could be
made adjustable in length to suit individual conditions
that are desired for the path of movement, and provide
for different control paths of the pin 46. However, the
mechanical linkage illustrated herein provides the
desirable vertical path of movement of the pin 46 when
the bucket has been raised to a desired level. In other
words, the bucket raised along a substantially vertical
3o path after it has reached a desired level near the level
of the pivot axis of pin 40.
The loader assembly with the short rear lift
arm links, that are mounted on a high pivot improves the
rigidity of the lift boom assembly 24 so the lift arms
travel in a definite path with clearance maintained along
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the sides of the operator's compartment. The rear lift
arm links 32, mounted on the high pivot 40 to the frame
uprights 20, provides a boom assembly having the benefits
of an articulated boom without extending into the space
needed for the rear engine compartment opening, so that
there is good service access for the engine compartment.
It does not extend rearwardly beyond the rear access door
15A of the engine compartment 15. The articulated boom
loader of the present invention has a large degree of
commonality of basic frame and drive structure with
conventional skid steer loaders.
The path of movement of the bucket 48, and the
forward ends of the lift arms, as stated, is such that
the rear lift arm links 32 move rearwardly upon initial
lifting, as guided by the rigid links 66. This tends to
move the bucket in a more vertical path initially, so
that the bucket 48 and its load stay close to the front
tires and front of the main frame 14 as the bucket is
first lifted, rather than moving out on a radius.
the rearward movement of the rear lift arm links has
important features in defining the initial lifting path
of the bucket.
CONCLUSION
The present invention provides a vertical lift
path in the range of movement of a loader boom where the
reach of the boom normally is reduced. This permits the
operation of the loader in filling trucks and piling
material to proceed more easily. The control linkage
provides a positive and reliable control for obtaining
the vertical path of movement.
The present invention provides a vertical lift
path in the range of movement of a radial arc boom
machine where the reach of the boom normally increases or
moves forwardly.
This mechanical linkage system of providing
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both inward movement initially and increased reach near
full lift height can be packaged on a conventional skid
steer machine design. This maintains the existing
features of machine design, production processes, and
field service procedures in the areas of operator
compartment, controls, engine, transmission, hydraulics
and hydrostatics, cooling system, electrical system,
service access features and means of connecting
attachment tools to the skid steer machine.
Although the present invention has been
described with reference to the preferred embodiments,
those skilled in the art will recognize that changes may
be made in form and detail without departing from the
spirit and scope of the invention.
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