Note: Descriptions are shown in the official language in which they were submitted.
CA 02480238 2004-10-14
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LIFT APPARATUS HAVING AN ARTICULATED DOUBLE
PARALLELOGRAM BOOM ASSEMBLY
Background of the Invention
This application is a division of copending Canadian Patent Application Serial
No. 2,227,986 filed January 2C~, 1998.
1. Field of the Invention
The present invention relates to a lift apparatus; and more particularly, to a
lift
apparatus, such as an aerial work platform, having an articulated double
parallelogram
boom assembly.
2. Description of Related Art
A vehicular tow profile self propelled aerial work platform is disclosed in
U.S.
Pat. 4,757,875, owned by the Assignee of the instant application, wherein a
work
platform is mounted on the distal end of a telescopic boom assembly having its
proximate
end pivotally connected to a floating or riser frame assembly which, in turn,
is connected
to a support frame on the vehicle by a-pair of parallel arms, whereby the
telescopic boom
assembly and associated work platform can be extended to an operative position
and
folded to a lowered position, so that the vehicle can be maneuvered in
warehouses or
manufacturing plants having nine foot high doorways.
An articulated parallelogram assembly for elevating a work platform is
disclosed
in U.S. Pat. 5,129,480, also owned by the Assignee of the instant application,
wherein a
lower boom assembly having parallel compression and
CA 02480238 2004-10-14
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tension arms, offset from the centerline of the vehicle, are
pivotally connected between a floating or riser frame assembly
and the vehicle frame . An upper boom assembly is also provided
wherein parallel compression and tensian arms, offset from the
centerline of the vehicle, are pivotally connected between the
platform frame and the floating frame.
Another vehicular low profile, self-propelled aerial work
platform having an articulated parallelogram boom assembly is
disclosed in U.S. Patent No. 5,584,356, also owned by the
Assignee of the instant application. The articulated boom
assembly includes a lower baom assembly having pairs of
compression and tension arms pivotally connected between a
support frame on the vehicle and a floating frame, and an upper
boom assembly having pairs of compression and tension arms
pivotally connected between the floating frame and a riser
connected to the proximate end of a telescopic boom assembly
havi.n~J ~ war. k pl~t~form connected to the distal end thereof .
The ends of the tension arms in the upper and lower boom
assemblies, which are pivotally connected to the floating
frame, share the same pivot connection so that when the
articulated parallelogram is in the folded position, the
tension arms are inter-digitated and lie in the same common
plane so that the vehicle can be maneuvered through a low
doorway, in the order of six feet, seven inches. A
synchronization linkage is mounted in the floating frame and
connected between the pairs of compression arms in the upper
and lower boom assemblies for maintaining the floating frame
in a vertical orientation during the elevating and folding of
the articulated parallelogram boom assembly.
While the self propelled aerial work platforms disclosed
in the aforementioned patents have been satisfactory for their
intended purposes, certain features contained in these self
propelled aerial work platforms are employed in the low profile
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self propelled aerial work platform of the present invention to provide a new
combination
of components; whereby the telescopic boom assembly can be folded to a lowered
position so that the vehicle can be maneuvered through standard height six
foot, seven
inch doorways.
SIJIUIMARY OF THE INVENTION
In accordance with an embodiment of the present invention there is provided a
lift
apparatus, comprising: a superstructure frame support; a riser; and an
articulated
parallelogram boom assembly operatively connected between the superstructure
frame
support and the riser. The articulated parallelogram boom assembly includes a
floating
frame; a lower parallelogram boom assembly operationally connected between the
superstructure frame support and the floating frame; an upper parallelogram
boom
assembly operationally connected between the floating frame and the riser, and
a lift
cylinder raising and lowering the articulated parallelogram boom assembly and
connected
between the upper parallelogram boom assembly and the lower parallelogram boom
assembly. The lift cylinder remains vertically oriented with respect to the
superstructure
frame support over a range of motion of the articulated parallelogram boom
assembly.
In one preferred embodiment, the lower parallelogram boom assembly includes a
pair of parallel, laterally spaced first compression arms and a pair of
parallel, laterally
spaced first tension arms. The first compression and tension arms form a
parallelogram
assembly. The f rst compression and tension arms are pivotally connected at
one end to
the. superstructure frame support and pivotally connected at another end to
the floating
frame. Preferably, the upper parallelogram boom assembly includes a pair of
parallel,
laterally spaced second compression arms and a tubular second tension arm: The
second
compression arms and the second tension arm form a parallelogram assembly. The
second compression and tension arms are pivotally connected at one end to the
floating
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frame and pivotally connected at another end to the riser.
In another preferred embodiment, the lift cylinder includes a first and second
end,
the first end connected to the first compression arms and the second end
connected to the
second tension arm.
In another preferred embodiment, the first end of the lift cylinder includes a
first
end and a second end, the first end connected to the first compression arms
and the
second end connected to the second compression arms.
In preferred embodiments, the lower parallelogram boom assembly slopes
downward from the superstructure frame support to the floating frame when the
articulated parallelogram boom assembly is fully lowered.
In yet another preferred embodiment, the upper parallelogram boom assembly
slopes downward from the floating frame to the riser when the articulated
parallelogram
boom assembly is fully lowered.
In preferred embodiments, the lift apparatus further includes a work platform
operationally connected to the articulated parallelogram boom assembly. A
telescopic
boom may be connected between the riser and the work platform.
Other features and further scope of applicability of the present invention
will
become apparent from the detailed description given hereinafter. However, it
should be
understood that the detailed description and specific examples, while
indicating preferred
embodiments of the invention, are given by way of illustration only, since
various
changes and modifications within the spirit and scope of the invention will
become
apparent to those skilled in the art from this detailed description.
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BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed
description given herein below and the accompanying drawings which are given
by way
of
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J
illustration only, and thus, are not limitative of the
present invention, and wherein:
Fig. 1 is a side elevational view of a mobile aerial
work platform showing the double parallelogram riser
s assembly according to the invention in a fully lowered
position;
Fig. 2 is a side elevational view showing the double
parallelogram riser assembly in an extended raised
position;
to Figs. 3a and 3b illustrate cross-sections of the
articulated parallelogram boom assembly along lines 3a-3a
and 3b-3b in Fig. 2;
Fig. 4a illustrates a cross-section of the
articulated parallelogram boom assembly viewed in the
is direction of arrows 4a-4a in Fig. ~;
Fig. 4b illustrates the opposite side of the floating
frame of the articulated parallelogram boom assembly as
compared to Fig. 4a;
Fig. 5 illustrates a planar bottom view of the
2o tubular tension arm in the upper boom assembly of the
articulated parallelogram boom assembly;
Fig. 6 illustrates a top view of the upper boom
assembly of the articulated parallelogram boom assembly;
Fig. 7 illustrates a top view of the lower boom
2s assembly of the articulated parallelogram boom assembly;
Fig. 8 illustrates a top down view of the compression
arms in the lower boom assembly of the articulated
parallelogram boom assembly; and
Fig. 9 illustrates a top down view of the aerial work
30 platform according to an embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, and more particularly to
Figs. 1-4b, a low profile self propelled aerial work
35 platform representing an embodiment of the present
invention includes a super-structure support frame 1,
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having vertically extending plates 2 upon which
counterweights, not shown, are adapted to be mounted. The
support frame 1 is mounted on a turntable 3 carried by a
vehicle chassis 4. An articulated parallelogram boom
s assembly 5 is operatively connected between parallel
upwardly projecting plate portions 1a of the support frame
Z and a riser 6. ~'he riser 6 is also connected to the
proximate end portion of a telescopic boom assembly 7
having a work platform 8 mounted on the distal end
to thereof .
The articulated parallelogram boom assembly 5
includes a lower boom assembly having pairs of parallel,
laterally spaced compression and tension arms 9 and 10,
respectively, extending between the support frame 1 and a
15 floating frame 11. The compression and tensions arms 9
and 10 are pivotally connected to the support frame 1 as
at 12 and 13, respectively, and to the floating frame as
at 14 and 15, respectively. As shown in Fig. l, in the
retracted position, the compression and tension arms 9 and
zo l0 extend downwardly from the frame 1 to the floating
frame 11.
The articulated parallelogram boom assembly 5 also
includes an upper boom assembly having a pair of parallel,
laterally spaced compression arms 16 and a tubular tension
as arm 17 extending between the riser 6 and the floating
frame 11. The compression arms 16 and the tubular tension
arm 17 are pivotally connected to the riser 6 as at 18 and
19, respectively, and to the floating frame 11 as at 20a
and 20b, respectively. As shown in Fig. 1, in the
3o retracted position, the compression arms 16 and the
tubular tension arm 17 extend downwardly from the floating
frame 11 to the riser 6.
An extensible hydraulic cylinder 21, positioned on
the centerline of the frame 1, is pivotally connected as
3s at 22 to and between the lower compression arms 9, and as
at 23 to and between side walls of the tubular tension arm
17. Fig. 5 illustrates a planar bottom view of the
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tubular tension arm 17. As shown., the tubular tension arm
17 has a hole 42 formed in a bottom wall thereof. The
hole 42 accommodates the hydraulic cylinder 21 such that
the rod of the hydraulic cylinder 21 extends up into the
s tubular tension arm 17, and is pinned to the side walls of
the tubular tension arm 17. As further shown in Figs. 1,
2, 4 and 5, two pairs of reinforcement plates 40 are
attached to and project downwardly from the tubular
tension arm 17. As discussed in more detail below, the
1o reinforcement plates 40 serve as pivot mounting points 44
for a pair of tension links 33.
As shown in Figs. l and 2, the hydraulic cylinder 21
is pinned at 22 arid at 23 on the longitudinal center lines
of the lower compression arms 9 and the tubular tension
i5 arm 17, respectively. When the hydraulic cylinder 21 is
retracted, the articulated parallelogram boom assembly 5
is in the folded position, as shown in Fig. 1, and is in
the elevated position, as shown in Fig. 2, when the
hydraulic cylinder 21 is extended. Throughout the range
20 of motion of the articulated parallelogram boom assembly
5, the hydraulic cylinder 21 remains vertical. w
A boom lift cylinder 24 is also pivotally connected
along the centerline of the frame 1, above the hydraulic
cylinder 21, between the riser 6, as at 18, and the
25 telescopic boom assembly 7, as at 26. Accordingly, the
boom lift cylinder 24 and the compression arms 16 share a
common pivot point 18. The remaining components on the
telescopic boom assembly 7 are conventional and include a
master hydraulic cylinder 27 for controlling a slave
3o cylinder 28 on the distal end of the telescopic boom
assembly 7 which, together, maintain the work platform 8
in a horizontal position during the raising and Towering
of the articulated parallelogram boom assembly 5 and the
luffing of the telescopic boom assembly 7 with boom lift
35 cylinder 24. In the folded or retracted position of the
articulated parallelogram boom assembly 5, the hydraulic
cylinder 21 is nested between the pairs of arms 9 and 10,
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and the boom lift cylinder 24 is nested between the
compression arms 16, above the hydraulic cylinder 21.
Both the master cylinder 27 and the cylinder for
telescoping the telescopic boom assembly 7 are also
s disposed along the centerline of the frame 1.
Figs. 3a and 3b illustrate cross-sections of the
parallelogram boom assembly S along lines 3a-3a and 3b-3b
in Fig. 2. As shown in Fig. 3a, the riser 6 is formed
from parallel plates 31 and a transverse plate 32. The
io tubular tension arm 17 is 'disposed between the parallel
plates 31, and sidewalls of the tubular tension arm 17 are
pinned to lower portions of the parallel plates 31
extending below the transverse plate 32. A pivot, pin 35
pivotally attaches the compression arms 16 to the riser 6
15 with a boss 34 between each compression arm 16 and plate
31 such that the parallel plates 31 are disposed between
the compression arms 1~.
As shown in Fig. 3b, the support frame 1 includes
upwardly projecting plate portions la to which both pairs
20 of the compression and tension arms 9 and 10 are pivotally
attached. The compression arms 9 are pinned to the inside
of a respective one of the plate portions la. The tension
arms 10 each have lugs 60 attached thereto forming a fork
between which a respective plate portion la is pinned.
2s Fig, 7 illustrates a top view of the lower boom assembly
of the articulated parallelogram boom assembly 5, and
shows the pivot connections between the tension arms 10
and the plate portions la. Consequently, the tension arms
are disposed further apart from one another than the
3o compression arms 9.
As shown in Figs . 3a .. and 3b, the parallel plates 31
of the riser 6 are spaced apart a smaller distance than
the parallel plate portions 1a of the frame 1. As shown
in Fig. l, this arrangement permits the tubular tension
3s arm 17 connected to the parallel plates 31 to nest between
the tension arms 10, and when nested, the pivot point 19
for the tubular tension arm 17 is disposed below the pivot
CA 02480238 2004-10-14
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point 13 for the tension arms 10. As further shown in
Figs. 3a and 3b, the pair of compression arms 16, the pair
of tension arms 10, and the pair of compression arms 9 are
spaced apart substantially the same distance to provide a
s very stable parallelogram assembly. Because of the stable
parallelogram assembly of the lower boom assembly, the
floating frame 11 is maintained in a vertical orientation
throughout the range of motion of the articulated
parallelogram boom assembly 5.
io Fig. 4a illustrates a cross-section view of the
articulated parallelogram boom assembly 5 looking in the
direction of arrows 4a-4a, and Fig. 4b illustrates the
opposite side of the floating frame 11 as compared to Fig.
4a. As shown, the floating frame 11 is formed from
is parallel plates 52 and transverse plates 54 and 56 (see
also Fig. 2). The compression arms 9 are pinned to a
respective' plate 52. The tension arms 10 and the
compression arms 16 each have lugs attached thereto
forming a fork between which a respective plate 52 is
zo pinned. Fig. 6 illustrates a top down view of the upper
boom assembly of the articulated parallelogram assembly 5,
and shows the pivot connections between the compression
arms 16 and the floating frame 11. Fig. 7 shows the pivot
connections between the tension arms 10 and the floating
2s frame 11 (see also Fig. 2). The tubular tension arm 17 is
pinned between plates 52. Specifically, a cylindrical
housing 58 passes through the side walls of the tubular
tension arm 17, and the cylindrical housing 58 is pinned
to the plates 52.
3o As further shown in Figs. 4a and 4b, the links 33
extend diagonally down from the two pairs of parallel
reinforcement plates 40 through a hole in the transverse
plate 54, and, as shown in Fig. 2, attach to the end of
the compression arms 9 at pivot point 46. Fig. 8
3s illustrates a top down view of the compression arms °. As
shown, at the floating frame 11 end of the compression
arms 9, the compression arms 9 have a block 70 welded
CA 02480238 2004-10-14
therebetween. Two pairs of lugs 72 extend from the block
70, and form forks between which a respective one of the
links 33 is pinned as at 46 in Figs. 1 and 2. The pivot
point 46 lies in a plane formed between respective
s extensions of the longitudinal center lines of the
compression arms 9. .
Furthermore, Fig. 4b shows a slot section 50 formed
in the upper portion of the floating frame 11. The slot
section SO accommodates the telescopic boom assembly 7 in
to the retracted position as shown in Fig. 1. Consequently,
the telescopic boom assembly 7 slopes downwardly from the
riser 6 in the retracted position. As shown in Fig. 4b,
three guide blocks 62 (e.g., wear pads), for guiding the
telescopic boom assembly 7 to the retracted position, are
disposed about the slot section 50.
As discussed above, each link 33 is pivotally
connected to one of the -reinforcing plates 40 as at 44.
The pivot point 44 is disposed further from the floating
frame 11 than the pivot point 20b for .the tubular tension
zo arm 17. Each link 33 is further pivotally connected to a
respective compression arm 9 as at 46.
By this construction and arrangement, the links 33
extend diagonally relative to the pivotal connections 14
and 20b, so that the link pivot connection 44 is on one
as side of the compression arm 16 pivot connection 20b, and
the link pivot connection 46 is on the other side of the
compression arm 9 pivot connection 14; whereby, during the
actuation of the hydraulic cylinder 21 to pivot the
compression arms 9 and 16 relative to each other, the
30 links 33 will synchronize the movement of the upper
parallelogram assembly relative to the lower parallelogram
assembly.
Specifically, in the retracted position, the
perpendicular moment arm at the lower boom assembly of the
articulated parallelogram boom assembly 5 (i.e., the
distance, measured perpendicularly, between a line passing
through the longitudinal axis of the link 33 including the
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pivot point 46 and a line parallel thereto passing through
the pivot point 14) is substantially larger than the
perpendicular moment arm for the upper boom assembly
(i.e., the distance, measured perpendicularly, between a
s line passing through the langitudinal axis of the link 33
and the pivot point 44 and a line parallel thereto passing
through the pivot point 20b).
As the articulated parallelogram boom assembly 5
extends, the perpendicular moment arms for the lower and
to upper boom assemblies gradually become equal at about the
point when the lower ar_d upper boom assemblies are
parallel, and then the perpendicular moment arm for the
upper boom assembly becomes larger than the perpendicular
moment arm for the lower boom assembly. At the fully
a.s extended position, the perpendicular moment arm of the
upper boom assembly is substantially larger than the
perpendicular moment arm of the lower boom assembly by
about the same margin that the perpendicular moment arm of
the lower boom assembly exceeded the perpendicular moment
2o arm of the upper boom asse;nbly in the retracted position.
In a preferred embodiment the perpendicular moment arms
of the upper and lower boom assemblies are 69.12mm and
114.04mm in the retracted position, 107.64mm and 123.59mm
in the parallel position, and 113.88mm and 68.03mm in the
2s fully extended position. The above values are given by
way of example only, and in no way limit the possible
perpendicular moment arm values of_ the present invention.
Disposing the hydraulic cylinder 21 vertically
between the compression arms 9 and the tubular tension arm
30 17, permits the compression and tension arms 9 and 10 to
slope downwardly from the frame 1 in the retracted
position, and permits the compression arms 16 and the
tubular tension arm 17 to slope downwardly from the
floating frame 11 in the retracted position.
35 Additionally, the slot sec~ion 50 in the floating frame 11
permits the telescopic boo::; assembly 7 to slope downwardly
from the riser 6 in the r~~racted position. As a result,
CA 02480238 2004-10-14
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the height of the frame 1, the length of the floating
frame 11, and the length of the riser 6 can be increased
without increasing the overall retracted height of the
machine. Accordingly, the highest point of the machine in
s the retracted position is approximately six feet, six
inches or less. As one skilled in the art will realize,
however, the overall dimensions of the machine could be
increased or decreased.
The increased height of the frame 1, the increased
length of the floating frame 11, and the increased length
of the riser 6 provides for at least a first and/or second
advantage. The first advantage is an increase in the
working height that the machine can achieve. The second
advantage is a decrease in the length of the telescopic
Zs boom assembly 7 and/or the length of the articulated
parallelogram boom assembly 5 without a decrease in the
working height as compared to conventional aerial work
platforms. As a result, an aerial work platform with no
tail swing and minimal front swing is produced without a
2o decrease in working height as compared to conventional
aerial work platforms. Fig. 9 illustrates a top view of
the aerial work platform according to the present
invention. As Figs. 2 and 9 show, the aerial work
platform according to the present invention has no tail
2s swing and minimal front swing. Depending on desired
operating characteristics, one skilled in the art can
balance the increased working height versus reduced front
swing trade-off to meet those characteristics.
Furthermore, as Figs. 1-2, 6-7, and particularly Fig.
30 9 show, the longitudinal axes of the articulated
parallelogram boom assembly 5, the hydraulic lift cylinder
21, the telescopic boom assembly 7, and the boom lift
cylinder 24 lie within the same vertical plane (i.e., are
in-line) .
The positioning of the hydraulic cylinder 21 in
cooperation with the links 33 sets up a lift geometry
which minimizes the loads on both the hydraulic cylinder
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21 and the links 33, and maintains the loads on the
hydraulic cylinder 21 and the links 33 substantially
constant over the range of motion of the articulated
parallelogram boom assembly 5.
The load on the hydraulic cylinder 21. could be
reduced by positioning the hydraulic cylinder 21 closer to
the frame 1. Doing so, however, presents a clearance
problem with the bottom of the hydraulic cylinder 21.
Accordingly, the length of, the hydraulic cylinder 21 would
to have to be decreased; thus, decreasing the maximum
possible working height of the machine. Depending on
desired operating characteristics one skilled in the art
can balance the load versus maximum working height trade-
off to meet those characteristics.
Additionally, the rod of the hydraulic cylinder 21
could be pinned between the compression arms 16. This
would require forming a larger version of hole 42, and
forming a similar hole in the top of the tubular tension
arm 17 to accommodate the cylinder portion of the
2o hydraulic cylinder 21. To make such an accommodation
would require increasing the width of the"tubular tension
arm 17 with the resulting ripple effect being an overall
increase in the width of the articulated parallelogram
boom assembly 5.
As a further note, the articulated parallelogram boom
assembly 5 may be applied to devices other than self
propelled aerial work platforms without departing from the
spirit and scope of the present invention.
While the invention has been described in connection
3o with what is presently considered the most practical and
preferred embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments, but
on the contrary, is intended to cover various
modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
