Centerline double riser with single lift cylinder and link for a low profile self propelled aerial work platform

A vehicular low profile, self propelled aerial work platform having an articulated parallelogram boom assembly including a lower boom 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 having a work platform 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.

BACKGROUND OF THE INVENTION 
A vehicular low profile self propelled aerial work platform is disclosed in 
U.S. Pat. No. 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. No. 5,129,480, also owned by the Assignee of the 
instant application, wherein a lower boom assembly having parallel 
compression and 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 tension arms, offset from the centerline of the vehicle, 
are pivotally connected between the platform frame and the floating frame. 
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 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. 
SUMMARY OF THE INVENTION 
The low profile self propelled aerial work platform of the present 
invention comprises, essentially, an articulated parallelogram boom 
assembly connected between a support frame on the vehicle and a riser at 
the proximate end portion of a telescopic boom assembly having a work 
platform on the distal end thereof. The parallelogram boom assembly 
includes a lower boom assembly having parallel compression and tension 
arms positioned substantially on the centerline of the vehicle and 
pivotally connected between the support frame on the vehicle and a 
floating frame or riser; and an upper boom assembly having compression and 
tension arms positioned substantially on the centerline of the vehicle and 
pivotally connected between the floating frame and the riser at the 
proximate end portion of the telescopic boom. The tension arms on the 
upper and lower boom assemblies share a common pivot connection on the 
floating frame so that the tension arms on the upper and lower boom 
assemblies inter-digitate and lie in the same common horizontal plane when 
the telescopic boom is lowered to the folded position, whereby the vehicle 
can be maneuvered in warehouses or manufacturing plants having standard 
height six foot, seven inch doorways. A single lift cylinder extends 
between the compression arms in the upper and lower boom assemblies for 
elevating and lowering the telescopic boom assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, and more particularly to FIGS. 1, 2 and 3, the 
low profile self propelled aerial work platform of the present invention 
comprises a superstructure support frame 1, having vertically extending 
plates 2 upon which counterweights, not shown, are adapted to be mounted; 
the support frame is mounted on a turntable 3 carried by a vehicle chassis 
4. An articulated parallelogram boom assembly 5 is operatively connected 
between the support frame 1 and a riser 6 connected to the proximate end 
portion of telescopic boom assembly 7 having a work platform 8 mounted on 
the distal end 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 floating frame 11, the arms being pivotally connected to the support 
frame as at 12 and 13, and to the floating frame as at 14 and 15. The 
articulated parallelogram boom assembly 5 also includes an upper boom 
assembly having pairs of parallel, laterally spaced compression and 
tension arms 16 and 17, respectively, extending between the riser 6 and 
the floating frame 11, the arms 16 and 17 being pivotally connected to the 
riser as at 18 and 19, and to the floating frame 11, as at 20 and 15, 
which is the same pivot connection for tension arms 10 in the lower boom 
assembly. 
An extensible hydraulic cylinder 21, positioned on the centerline of the 
machine, is pivotally connected as at 22 to and between the lower 
compression arms 9, and as at 23 to and between the upper compression arms 
16, whereby, when the cylinder 21 is retracted, the parallelogram 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. 
A boom lift cylinder 24 is similarly pivotally connected along the 
centerline of the machine, above cylinder 21, between the riser 6, as at 
25, and the telescopic boom assembly 7, as at 26. The remaining components 
on the telescopic boom assembly 7 are conventional and include a master 
hydraulic cylinder 27 for controlling a slave cylinder 28 on the distal 
end of the telescopic boom assembly 7 for maintaining the work platform 8 
in a horizontal position during the raising and lowering of the 
parallelogram assembly 5 and the luffing of the telescopic boom assembly 7 
with boom lift cylinder 24. In the folded or retracted position of the 
parallelogram assembly 5, cylinder 21 is nested between the pairs of arms 
9, 17 and 16, and boom lift cylinder 24 is nested between arms 16, above 
cylinder 21, and master hydraulic cylinder 27, as well as the cylinder 
inside the telescopic boom assembly 7 for extending and retracting the 
same are positioned above the other cylinders on the centerline of the 
machine. 
FIGS. 7 and 8 illustrate the details of the common pivot connection 15 
between the tension arms 10 and 17 at the floating frame 11 wherein it 
will be seen that a transversely extending plate 29 is integral with the 
side walls of the floating frame 11 and has a plurality of spaced, short 
tubular members 30, 31, 32 integral with the plate 29 and extending 
outwardly therefrom. Each of the tension arms 10 and 17 are provided with 
enlarged portions 10a and 17a which extend into the respective spaces 
between the tubular members 30, 31 and 32, and the pivot bolt connection 
15 extends transversely through the side walls of the floating frame 11, 
the enlarged end portions 10a and 17a of the tension arms 10 and 17, and 
the tubular members 30, 31, 32. 
As shown in FIGS. 3 and 6, the opposite side plates of riser 6 are spaced 
apart a smaller distance than the support frame plates 1 to which the 
pairs of arms 9 and 10 are pivotally connected at 12 and 13, respectively. 
This allows the lower end of riser 6, in the retracted position of the 
parallelogram boom assembly 5 to extend down between support frame plates 
1, as shown particularly in FIGS. 4 and 6, so that pivot connection 19 of 
the pair of tension arms 17 to the riser 6 is positioned in axial 
alignment with the pivot connections 13 of the pair of tension arms 10 to 
the support frame plates 1. The pair of arms 17 are connected between the 
side walls of riser 6 and are thus spaced apart a smaller distance than 
the spacing between the pair of tension arms 10, and thus lie between the 
pair of arms 10 in the retracted position. 
The pair of compression arms 16 are pivotally connected at 18 on the outer 
sides of the side plates of riser 6, as shown in FIG. 6, so that the pair 
of arms 16, the pair of arms 10 and the pair of arms 9 are spaced apart 
substantially the same distance to provide a very stable parallelogram 
assembly, with only the pair of arms 17 being spaced apart a lesser 
distance than the others. 
As will be seen in FIGS. 7, 9 and 10, a synchronization linkage 33 is 
provided for maintaining the vertical orientation of the floating frame 11 
during the raising and lowering of the articulated parallelogram boom 
assembly 5. The linkage comprises a transversely extending tubular housing 
34 extending between and integral with the inner walls of the compression 
arms 16, through which the pivot connection bolt 20 extends. Similarly, a 
transversely extending housing 35 extends between and is integral with the 
inner walls of the compression arms 9. A pair of spaced, parallel 
forwardly extending ears 36 are integral with the housing 34, and a pair 
of spaced, parallel, upwardly extending ears 37 are integral with the 
housing 35. A link 38 extends between the pairs of ears 36 and 37, and its 
opposite end portions are positioned in the spaces therebetween and 
pivotally connected thereto by pins 39 and 40. By this construction and 
arrangement the link 38 extends diagonally relative to the pivotal 
connections 14 and 20, so that the link pivot connection 39 is on one side 
of the compression arm 16 pivot connection 20, and the link pivot 
connection 40 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 link 38 
will cause the floating frame 11 to remain in a vertical orientation and 
synchronize the movement of the upper parallelogram assembly relative to 
the lower parallelogram assembly. 
To complete the structural description, the transverse wall 29 is 
reinforced by a pair of spaced, parallel reinforcing plates 39 extending 
between and integral with the wall 29 and front wall of the floating frame 
11. 
From the above description it will be readily apparent to those skilled in 
the art that by providing the tension arms 10 and 17 with a common pivot 
15 on the floating frame 11, the pairs of arms 10 and 17 inter-digitate 
and lie in the same common horizontal plane when the articulated 
parallelogram boom assembly 5 is lowered to the folded position, whereby 
the low profile self propelled aerial work platform can be maneuvered in 
warehouses or manufacturing plants having relatively low doorways, such 
as, six feet, seven inches. In the lowered folded position the 
parallelogram boom assembly 5 lies in three closely adjacent horizontal 
planes, with the spaced arms 9 in the lowermost horizontal plane, parallel 
to the top of the superstructure horizontal plate on the turntable, the 
inter-digitated pairs of spaced arms 10 and 17 being in the center 
horizontal plane, and the spaced arms 16 being in the upper horizontal 
plane closely adjacent the center horizontal plane. The telescopic boom 
assembly 7 pivots down on top of the parallelogram boom assembly 5 in 
substantially a fourth plane above the upper horizontal plane, whereby the 
proximate end of the telescopic boom assembly adjacent its pivot 
connection with riser 6, is the highest point of the machine in the folded 
travel position, and is approximately six feet, six inches in height above 
the ground plane. The machine is approximately eighteen feet, eight inches 
in overall length, and five feet, nine inches in width which allows it to 
travel through standard width double doors having a six foot width. In the 
raised position of FIG. 2, with the telescopic boom assembly extended and 
elevated, the floor of the work platform 8 is approximately forty feet 
above the ground plane. 
The terms and expressions which have been employed herein are used as terms 
of description and not of limitation, and there is no intention, in the 
use of such terms and expressions, of excluding any equivalents of the 
features shown and described or portions thereof, but it is recognized 
that various modifications are possible within the scope of the invention 
claimed.