Note: Descriptions are shown in the official language in which they were submitted.
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HOIST
FIELD OF THE INVENTION
This invention relates to improved hoists useful, for example, for lifting and
lowering
truck dump bodies. In certain example embodiments, this invention relates to
improved scissor-
type hoists, which exhibit improved efficiency and/or performance.
BACKGROUND OF THE INVENTION
Extendible and retractable hoists for raising and lowering the dump bed of a
truck about
a pivoting hinge are well known in the art and come in many different types
and designs
(whether they be rear or side dump vehicles). The term "truck" is used herein
to describe all
types of vehicles which employ such hoists, including light, medium and heavy
duty dump
trucks and trailers.
In a typical hydraulic truck hoist, one or more hydraulic cylinders in a hoist
frame lie
lengthwise in relation to the frame rails of the vehicle and underneath the
truck bed. As the
hoist's cylinder extends, one end of the hoist frame pushes against the
underside of the dump
bed to which one end of the hoist is pivotally attached while the other end of
the hoist frame
pushes against the frame of the truck to which the other end of the hoist is
pivotally attached.
This causes the bed to rotate about its rear hinge pivot whereby the dump bed
is raised.
Retraction of the cylinder causes the bed to be lowered.
Generally speaking, truck hoist designs known prior to the subject invention
have one or
more inefficiencies and/or drawbacks (or problems) associated with their use.
For example,
some hoist designs are configured to require long, telescopic hydraulic
cylinder strokes to
achieve sufficient dump angles. However, as a telescopic hydraulic cylinder
extends e.g., in a
long "stroke" towards its full displacement, the amount of force that it is
capable of providing
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decreases significantly. The required length of the cylinder also impacts the
cycle time required
to operate the hoist. Although scissor-type hoists reduce this inefficiency
(at least in part),
scissor-type hoists exhibit other inefficiencies and/or problems.
For example, known scissor hoists are configured such that the hoist cylinder
is nearly
parallel to the dump bed when the dump bed is in the non-raised or lowered
position and thus
has very little initial leverage at the beginning of the lifting process.
Specifically, in such
designs, during the initial lift phase, much of the force of the cylinder is
inefficiently directed
because of the low angle of cylinder thrust relative to the truck frame and
dump bed (which
directs cylinder forces along the length of the truck and dump bed frame
rather than in the more
efficient raising direction which changes as the dump body is raised).
Therefore, much of the
hydraulic cylinder's lift force is unused at the beginning of lift operation.
As a result, such prior
art hoists often require larger and more expensive (or multiple) cylinders
otherwise unnecessary
in later lifting phases (i.e., they are only required to accommodate the
initial, inefficient lifting
phase).
In view of the above, it is apparent that there exists a need in the art for a
hoist which
addresses, overcomes, mitigates, and/or solves one or more of the above
problems and/or
drawbacks and/or inefficiencies in the art. It is a purpose of this invention
to fulfill this and/or
other needs in the art which will become more apparent to the skilled artisan
once given the
following disclosure.
SUMMARY OF THE INVENTION
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Generally speaking, this invention addresses the above-described needs in the
art by
providing a hoist which, by way of its unique structure and/or configuration,
exhibits improved
lift efficiency and/or performance.
In certain example (non-limiting) embodiments, therein is provided:
a hoist for raising or lowering a dump bed to and from a truck frame, the
hoist
comprising:
a pedestal located on and extending upwardly from a top surface of a frame
rail of a
truck frame for mounting the hoist to a truck frame;
a first lever arm having a first end connected to the pedestal via a first
pivot and having
a second end connected to a first end of a second lever arm via a second
pivot, the second lever
arm having a second, distal end pivotally connected to a dump bed frame via a
third pivot;
an extendible and retractable cylinder connected at a first end to said first
end of said first
lever arm via a fourth pivot, said fourth pivot being located at a location
spaced apart from said
first pivot, and said extendible and retractable cylinder connected at a
second end to said second
lever arm via a fifth pivot, said fifth pivot located on said second lever arm
between said second
pivot and said third pivot;
wherein in an initial, non-lift position, said first lever arm and said second
lever arm are
in a generally folded orientation such that said first and said second lever
arms are in or near a
generally parallel orientation with respect to one another, and said fourth
pivot is located
generally below said first pivot a selected offset distance sufficient to
improve said extendible
and retractable cylinder's lift angle relative to a lift direction of said
dump bed frame;
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wherein in a lifting phase, said extendible and retractable cylinder extends
and exerts a
lifting force on said second lever arm via said fifth pivot causing said
second lever arm to exert a
lifting force on said dump bed frame via said third pivot; and wherein said
first lever arm and
said second lever arm pivot out of the in or near generally parallel
orientations towards a dump
bed lifted position; and
wherein the location of said pedestal on said top surface of said frame rail
locates said
hoist at an elevated position relative to said frame rail thereby reducing
space usage between
frame rails when said hoist is installed on a vehicle.
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In yet further embodiments of the hoists described herein, when the hoist is
in the
initial, non-lift position, the fourth pivot is located generally or directly
in-line with a vertical
centerline of the first pivot. In other embodiments, however, the fourth pivot
is initially located
offset from a vertical centerline of the first pivot when the hoist is in the
initial, non-lift position.
In at least one variation of a hoist described herein, the hoist is so
structurally
configured such that when the hoist is operated in a lifting phase, and the
second lever arm is
caused to unfold from and lift upwardly from the first lever arm during the
lifting phase, the
fourth pivot moves about the first pivot and generally follows a lift
direction of the second lever
arm. In another embodiment, however, the first end of the extendible and
retractable cylinder and
the fourth pivot are each connected to the hoist pedestal or to a portion of a
truck frame generally
vertically below the first pivot in such a manner such that the fourth pivot
does not move and/or
follow the lift of the second lever arm as in other embodiments.
In yet further example embodiments, the hoist, including the (optional, and
therefore
only provided in certain embodiments) hoist pedestal, the first and second
lever arms, and the
first, second, third, fourth, and fifth pivots are each substantially
duplicated on each side of a
vehicle comprised in part of a truck frame and a dump bed frame.
In such embodiments, the respective pairs of first, second, and third pivots
(each pivot
of each pair located opposite its corresponding pivot on an opposite side of
the vehicle) are
connected to and joined by respective first, second, and third cross-shafts.
In at least one example
of such an embodiment, a cross member is optionally provided to structurally
connect oppositely
located pedestals to one another.
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In the embodiments described herein, the phrases "in or near generally
parallel" or
"generally parallel" do not refer to a narrow condition where the first and
second lever arm
structures or their associated pivots are precisely parallel to one another
but, instead, refer more
generally to a condition when the lever arms are folded upon one another in
conventional scissor
hoist fashion. Thus, significant angular deviations from a precisely parallel
orientation are
certainly contemplated within the meaning of these phrases or terms.
Certain specific examples of the invention are now described below with
respect to
certain non-limiting embodiments thereof as illustrated in the following
drawings wherein:
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. lA is a profile, perspective view of a prior art scissor-type hoist
installed between a
truck frame and a dump bed illustrated in a non-extended (or non-lifted)
state.
FIG. 1B is a profile, perspective view of the prior art scissor-type hoist
(and related
installation environment) depicted in FIG. lA illustrated in an extended (or
lifted) state.
FIG. 2 is a two-dimensional, plan view of one example embodiment of a hoist
according
to the subject invention shown with the lift cylinder in a non-extended (non-
lifted) state (with
the example hoist depicted installed between a truck frame and a dump bed).
FIG. 3 is an alternative, two-dimensional, plan view of the example hoist
depicted in
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FIG. 2 shown with the lift cylinder in an extended (or lifted) state.
FIG. 4 is a detailed, partial side-view of a truck having a raisable and
lowerable dump
bed installed with an example hoist according to the subject invention (and
the dump bed shown
in a non-lifted state).
FIG. 5 is a detailed, partial side view of a truck having a raisable and
lowerable dump
bed installed with an example hoist according to the subject invention (and
the dump bed shown
in a lifted or raised position for effecting a dumping operation).
FIG. 6 is a two-dimensional, plan view of an alternative, example embodiment
of a hoist
according to the subject invention shown with the lift cylinder in a non-
extended (non-lifted)
state (with the example hoist depicted installed on top of truck frame rails).
FIG. 7 is an alternative, two-dimensional, plan view of the example embodiment
of a
hoist illustrated in FIG. 6 shown with the lift cylinder in a partially
extended (partially lifted)
state (and with the example hoist depicted installed between truck frame rails
and a dump bed
frame).
FIG. 8 is an alternative, two-dimensional, plan view of the example embodiment
of a
hoist illustrated in FIG. 7 shown with the lift cylinder in a fully extended
(fully lifted) state (and
with the example hoist depicted installed between truck frame rails and a dump
bed frame).
FIG. 9 illustrates a three-dimensional, perspective view of one exemplar
embodiment of
a hoist according to the subject invention.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
For a more complete understanding of the present invention and advantages
thereof,
reference is now made to the following description of various illustrative and
non-limiting
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embodiments thereof, taken in conjunction with the accompanying drawings in
which like
reference numbers indicate like features.
Referring now initially to FIGS. 1A and 1B, therein is illustrated a prior art
scissor-type
hoist 101 known conventionally as a Type 1, Single Stage Scissor as designated
by the National
Truck Equipment Association ("NTEA"). Although this type of hoist is very
common in the
truck equipment industry, several inefficiencies and/or drawbacks have been
identified as
associated with this hoist design. As such, it is this design which serves as
a background in view
of which the present invention is compared and described.
As shown in the subject figure, hoist 101 is illustrated installed on a truck
T and
generally comprises a first lever arm 103 pivotally connected at one end to
frame rails 1 of truck
T via pivot 104 and at its other end to a second lever arm 105 via pivot 106.
Lever arm 105, in
turn, is pivotally connected to dump bed frame structures 3 via pivot 107. As
can be seen, prior
art hoist 101 is a scissor-type hoist which employs a lift cylinder 109 (e.g.,
a single stage
hydraulic cylinder) for raising and lowering the dump bed (not shown) of truck
T via dump
frame 3. Cylinder 109, in this regard, is connected to truck T via pivot 104
at its base end and is
connected to lever arm 105, at its other end, via pivot 111. It should be
noted that cylinder 109,
in its connection to the hoist and the truck to which it is installed, shares
a pivot, pivot 104, with
the first lever arm (arm 103) of the hoist. As a result, during initial lift
phases (such as depicted
in FIG. 1A), much of the force of cylinder 109 is inefficiently used because
of the low angle of
the cylinder relative to the lift direction of the dump bed. Although the
angle of the cylinder
relative to the lift direction of the dump bed improves in later stages of
dump bed lifting
operation (see FIG. 1B), the aforedescribed inefficient design of hoist 101
necessitates the use of
larger and more powerful lift cylinders than are otherwise required (at least
in the initial lift
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phase). This, of course, adds expense to the hoist as well as increases the
weight of the truck and
decreases available free space under the dump bed.
Turning now to FIG. 2, this figure illustrates a hoist 6 which reduces the
above described
inefficiencies in hoist design (i.e., described with respect to the hoist
depicted in FIGS. 1A and
1B) in conjunction with a partial view of a conventional dump truck T as one
environment in
which the present invention (e.g., example embodiment, hoist 6) finds utility.
Generally
speaking, dump truck T's relevant parts as they relate to this embodiment of
the invention
_
include a pair of longitudinal truck frame rails 1 on either side of the
vehicle (only one side
being shown here), frame 3 of a typical dump bed (the actual bed being omitted
for clarity), and
a rear pivot 5, all conventional in the art. So as to more clearly illustrate
novel hoist 6, various
other conventional parts of truck T are not shown.
Referring still to FIG. 2, hoist 6 is shown installed on truck T between truck
frame rails 1
and frame 3 of a dump bed. Specifically, first lever arm 7 of the hoist is
pivotally connected to
the truck at its first end via pivot P1 and is connected at its opposite end
to second lever arm 9
via pivot P2. The distal end of second lever arm 9, moreover, is connected to
dump bed frame 3
via pivot P3 (e.g., a cross-shaft assembly which substantially spans the width
of the dump bed
frame). Providing lifting power to hoist 6, an extendible and retractable
hydraulic cylinder 11 is
pivotally connected to first lever arm 7 via pivot P4 and to second lever arm
9 via pivot P5
(located generally between pivots P2 and P3).
Notably, unlike the prior art hoist illustrated in FIGS. 1A and 1B, cylinder
11 of hoist 6
does not share a pivot with its lower scissor arm (lever arm 7) as its
connection to truck T.
Instead, lever arm 7 of the inventive hoist is a generally triangularly shaped
structure (although
it need not be) with pivots P1, P2, and P4 located generally at (and thereby
"forming") the three
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corners of the triangle. Thus, in the illustrated embodiment, rather than
connecting cylinder 11
directly to truck frame rails 1 via pivot P1, cylinder 11 is connected to
pivot P4 located on
triangularly configured lever arm 7 (although, in some embodiments, it could
be connected to
the truck frame rails at a location spaced a select vertical distance below
pivot P1 while still
retaining some, but not all, of the improvements of other embodiments
described herein).
Furthermore, when hoist 6 is in the non-lift phase or position or in the
beginning of the lift phase
(e.g., when the arms of the hoist are folded down upon one another and
therefore generally, but
not precisely, parallel to one another) such as illustrated in FIG. 2, pivot
P4 is located generally
below and approximately in-line with the vertical centerline "C" of pivot P1
(certainly,
however, pivot P4 can be located somewhat offset from centerline "C" as long
as it is located
sufficiently below pivot P1 to achieve the benefits described herein) .
Importantly, locating
pivot P4 as such (as the point at which cylinder 11 is attached to the lever
arm), the angle of
thrust of cylinder 11 with respect to the lift direction of the dump bed is
improved (i.e., the
thrust angle is more nearly parallel to the lift direction). More
specifically, rather than the lift
cylinder being oriented largely perpendicular to the dump bed lift direction
in the non-lift phase
(i.e., at or near the beginning of the lift phase) such as prior art hoist 101
depicted in a non-lifted
state in FIG. 1A, locating pivot P4 below and generally vertically in-line
with pivot P1 angles
cylinder 11 away from a perpendicular orientation with respect to the lift
direction and more
parallel thereto (i.e., more in-line therewith). Angling or re-orienting
cylinder 11 as such, lift
efficiency is improved and smaller, less powerful (and therefore typically
cheaper and/or
lighter) lift cylinders can be employed and/or the weight lifting capacity of
the hoist is
increased.
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It should be understood, of course, that even though it is the relative
location of pivot P4
beneath and generally vertically in-line with pivot P1 in the beginning of the
lift phase that
enables the improved efficiencies of the subject hoist invention, it is not
intended that the scope
of the invention be limited to specific spacing(s) between pivots P1 and P4 or
limited to
particular degrees of vertical alignment thereof. Instead, it is simply
important that, whatever
quantity of vertical spacing is chosen and/or whatever degree of vertical
alignment is selected,
the angle of orientation of cylinder 11 with respect to the lift direction of
the dump bed which is
obtained provides improved lift efficiency (i.e., as compared to prior art
hoists where the lift
cylinder and the lower scissor arm share a pivot). It should be further
understood that the
configurations of one or both of lever arms 7 and 9 can be changed without
departing from the
scope of the invention as long as the relative (but not necessarily specific)
locations of pivots
P1-P5 are maintained with respect to one another. This contemplates and
includes, for example,
an embodiment in which pivot P4 is not located on lever arm 7 at all but,
instead, is located on
the truck or truck frame; lever arm 7, as a result, therefore, not necessarily
being triangular in
configuration (pivot P4, nevertheless, still being located generally below and
generally in-line
with pivot P1). This embodiment, however, would not favorably affect the
length of cylinder
stroke used in lifting operations such as described herein below.
Despite not being specifically limited to particular pivot spacing(s) or lever
configurations, certain non-limiting embodiments of hoist 6, such as
illustrated in FIGS. 2-5, are
believed to be capable of improving the lift capacity of the hoist by 20% or
more. Furthermore,
in embodiments such as illustrated, because pivot P4 moves during operation of
the hoist,
generally following the direction of the dump bed as it is lifted (see FIG. 3
where the movement
of pivot P4 is indicated by directional arrows), the length of stroke of
cylinder 11 which is
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needed to achieve full dump bed lift height is decreased (notwithstanding
other embodiments of
the invention in which pivot P4 is located on the truck frame and therefore
does not "travel", for
example). In the embodiment illustrated, for example, the required stroke
length to achieve full
lift is believed to be reduced by more than 20% without reducing the lift
capacity of the hoist.
Hoist 6, of course, can include more than one cylinder and/or sets of lever
mechanisms
(e.g., pairs of pivotally connected lever arms 7 and 9). In this regard, the
hoist lever assemblies
and/or respective lift cylinders may be duplicated on each side of a truck
frame, for example
(other embodiments, where more than two lever assemblies or lift cylinders are
employed are
contemplated as well). Moreover, either single stage or multi-stage telescopic
cylinders can be
used (nevertheless, although useful with the subject invention, expensive,
multi-stage, telescopic
cylinders are generally obviated by the hoists described and claimed herein).
Referring now to FIGS. 6-9, an alternative hoist embodiment, shown as hoist
60, is
illustrated therein. As can be in these figures, hoist 60 employs a pair of
pedestals 12a and 12b
(in some embodiments, connected via a cross member 13 such as shown in FIG.
9), each located
on a top surface 1T of respective frame rails 1, as the mount location for the
base of the hoist
(rather than locating pivots P1 and P4 generally or entirely between frame
rails 1 of truck "T"
when the hoist is in the non-raised or pre-lift state such as with hoist 6).
Moreover, the particular
example embodiment which is illustrated employs a duplicate lever arm set on
each side of the
vehicle (70a, 90a and 70b, 90b, respectively), each example lever arm set
being configured to be
operated synchronously with the other (only one side or set being visible in
FIGS. 6-8; FIG. 9
being the only three-dimensional figure). In this regard, each lever arm set
70a, 90a and 70b,
90b is connected to pivots P1, P2, P3 and P4 in a mirror image configuration
with respect to the
other (that is, with one lever arm set on one side of the hoist being
substantially or entirely
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duplicated on the other side).
More specifically, and referring still to FIGS. 6-9, first lever arms 70a and
70b are each
pivotally connected to brackets 12a and 12b at their first ends via pivot P1,
respectively, and are
connected at their opposite ends to second lever arms 90a and 90b via pivot
P2, respectively
(pivots P1 and P2 including or comprising cross-shafts in this embodiment).
The distal ends of
second lever arms 90a and 90b, moreover, are each connected to respective
brackets 15a and
15b via pivot P3 (also including or comprising a cross-shaft in this example
embodiment)
which, in turn, are connected to dump body frame 3. To power the hoist, a pair
of extendible and
retractable hydraulic cylinders 21a and 21b are pivotally connected to first
lever arms 70a and
70b via pivot P4 at one end and to second lever arms 90a and 90b via pivot P5
at the other (and,
in turn, are connected to a conventional hydraulic system, not shown, for
extending or retracting
the cylinders to lift or lower the hoist respectively).
At the beginning of hoist 60 operation, when hoist 60 is in a non-lifted state
and
cylinders 21a and 21b are fully retracted (see FIG. 6), similar to the
configuration of hoist 6 at
the beginning of its lift phase, pivot P4 is located generally below and
generally in line with the
vertical centerline "C" of pivot P1 (but it can be located offset from such
centerline as well). As
with hoist 6, locating pivot P4 as such establishes an improved cylinder lift
angle with respect to
the lift direction of dump bed frame 3 (with lift force being applied against
pivot 5) thereby
improving lift efficiency as compared to prior art hoists. Further similar to
hoist 6, as cylinders
21a and 21b are pressurized and hoist 60 is extended or "lifted", pivot P4
follows the lift
direction of the hoist (as indicated by arrows A in FIGS. 7 and 8), thereby
reducing the cylinder
stroke length needed to achieve a full dump bed lift angle.
Turning now to the structural differences and potential commercial advantages
of hoist
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60 (e.g., as compared to hoist 6), the use of pedestals 12a and 12b by the
hoist elevates certain
hoist parts so that space usage by hoist 60 between vehicle frame rails 1 is
substantially reduced
(but preferably minimized or even eliminated, in certain embodiments). In this
regard, although
the general (but not necessarily specific) orientation and spatial
relationship of hoist parts with
respect to one another remains generally the same in hoist 60 as compared to
hoist 6 (thereby
retaining lift angle advantages and the like such as described throughout the
specification
herein), pedestals 12a and 12b are employed in hoist 60 principally to raise
the mounting
position of pivots P1 and P4 (and their associated assemblies or parts) above
the horizontal
plane of the top surface 1T of frame rails 1. In particular, raising pivots P1
and P4, as such,
raises the first (lowermost) ends of cylinders 21a and 21b, as well as the
first ends of lever arms
70a and 70b (proximal to and including pivot P4 including the associated cross-
shaft), above the
horizontal plane of the top surface 1T of frame rails 1. Raising the mount
location of the parts of
the hoist in this manner (as described herein and as depicted in FIGS. 6-9)
entirely removes
hoist 60 from the horizontally extending space envelope extending between
frame rails 1
thereby freeing up such space between the frame rails for the installation or
operation of other
components of or for the vehicles on which hoist 60 may be installed. For
example, use of hoist
60 (such as compared to other hoist types, including hoist 6) leaves or
maintains an
unencumbered space envelope between frame rails 1 so that safety related
components may be
installed therein such as might be required by current or future highway
safety laws (e.g., such
as those administered or enforced by the National Highway Traffic Safety
Administration).
As an additional advantage to hoist 60 (e.g., as compared to hoist 6), raising
the mount
location of pivot P1 (e.g., relative to hoist 6) decreases the distance
between pivot P1 and pivot
P3 when hoist 60 is in a fully lifted or extended position (such as
illustrated in FIG. 8). As a
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result, the total required lift distance of the hoist, that is the distance
which the hoist must raise
frame 3 to obtain a full lift angle, is decreased appreciably while still
retaining much of the lift
efficiency improvements of the hoist (i.e., as compared to prior art hoists)
which primarily result
from improved initial lift angles (e.g., obtained by locating pivot P4
generally below pivot P1 at
the beginning of the lift phase). In certain embodiments, in this regard, it
is contemplated that
such total required lift distance can be reduced by as much as 8-10 inches,
thereby again reducing
the size of lift cylinders needed for hoist lift operations.
Although, in the illustrated embodiment, certain hoist parts (as discussed
herein) are
depicted located entirely above the plane of top surface 1 T, other
embodiments in which such
parts are only partially raised relative to surface IT (e.g., such as compared
to the orientation
and/or location of parts of hoist 6) are, of course, contemplated as within
the scope of the
invention. Furthermore, just as with hoist 6, hoist 60, can, of course (such
as in other
embodiments not specifically illustrated in the present application), include
as few as one or,
alternatively, more than two hydraulic cylinders and/or sets of lever arms or
mechanisms. Also
similar to hoist 6, either single stage or multi-stage telescopic cylinders
can be used with such
hoists (recognizing that the hoist designs disclosed herein largely obviate
the need for multi-
stage, telescopic cylinders). Moreover, it is contemplated that hoists of this
invention may be
used in other applications other than for rear dumping vehicles.
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