Note: Descriptions are shown in the official language in which they were submitted.
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High-reach ~ork platforms. of the parallelogram linkage
type are well known in the prior art. Examples of such
structures are shown in Merrick 3,807,575, Stucky 3,768,591 and
Jones et al. 3,283,850. The linkage of the present invention is
characterized by use of spaced twin parallelograms at the lower
level, the upper parallelogram linkage being nested between the
twin linkage when th.e assembly is in folded or retracted position.
In this pos:ition the linkages are at acute angles with the
spaced, stationary vertical members attached to the base, and,
since the upper li.nkage is longer than the lower, the work
platform is positioned outboard of the s.paced vertical members.
The assembly thus folds into the mi.nimum space for transport
or storage. Also the platform assembly of thi.s, invention
because of its s~mmetrical construction i.s better balanced and
stronger than certain pri.or art devices as; shown in the Merrick
United States Patent 3,807,575.
Accordin~ to the present invention there is provided
a high-reach ~ork platform assembl~, comprising:
(.a~ a base frame;
(,bl two stationary members attached to said base frame,
sai.d members bei:ng sp~aced apart and extendi,ng in a vertical,
parallel relation up~ardly from sai.d bas.e frame;
(cl a fi,rst ~e~tical post;
~d~ t~o fi,rst pair of vertically spaced, co-extensive
t~in li.nkage arms,, said first pairs being spaced laterally
apart, sai.d first pairs bei.ng pi.votally attached at one of their
ends -to the faci.ng surfaces: of said members and being further
pivotally attached at thei.r opposi.te ends to the outer surfaces
of said first ~ertical pos:t, said first post being su:Eficiently
wi.de to span the lateral di.stance separating said first pairs;
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te) a second vertical post;
(.f), a second pair of vertically spaced, co-extensive twin
linkage arms pivotally attached one of their ends to said first
post above the points of attachment of said first pairs, said
second pair extending in overlying relation to and between said
first pairs and ~eing further pivotally attached at their
opposite ends to said second post, sai.d second pair of linkage
arms being lon~er than said first pairs; .:
(.gl a work platform ri.gidly secured to and extending
horizontally from sai,d second post aboye th.e points of attach-
ment of said second pair;
(',h). a fir~t pai,r of extendable and retractable motor
element means for pi.voti.ng s.aid firs.t pai.rs about said
stationar~mem6ers:, sai,d ~i.rst means i.ncludi.ng a paix of
hydrauli.c c~li.nders spaced laterally apart and pivotally
connected between said ~ase frame and the lower linkage arms
i,n said first pai.rs; and
~i,l a second extendable and ret~actable motor element
means ~or pivoting said second pair about said first post,
sai.d second means i:ncludi,ng a hydraulic cylinder pivotally
connected between sai.d fi,rst post and the lower linkage arm in
said se:cond pai.r, sai.d first means and sai.d second means, when
re.tracted, causing said second pai.r of twin li.nkage arms to
nest ~etwe.en sai.d fi.rst pairs, ~ith said first pairs and said
second pair di~posed at acute angles to said first post at
their pivotal attachments thereto and with said work platform
adjacent to but outwardly of said stationary members.
In the accompanying dra~ings, which illustrate an
exemplary embodiment of the present invention:
3Q Fig. 1 is a perspective view of the assembly in
, ~:
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operation;
F;g. 2 is a side view of the assembly of Fig. 1 in
retracted or folded condition; and
Fig. 3 is a top plan view of the structure as shown
in ~ig. 2.
Referring initially to Fig. 1, the assembly includes
a generally rectangular base frame formed of side members 10
and 11 and two end members 12. Extending outwardly from the
corner areas of the base frame are plates ~hich carry s~litable
casters 13 and swingout stabilizi,ng jacks 14.
Stati,onary spaced members 16 and 17 extend in vertical,
parallel relation upwardly from the base frame. Two pairs of
vertically spaced, coextensive twin linkage arms are pivotally
attached at one of their ends to the facing surfaces of each of
said stationary~ members 16 and 17. One of the twin pairs of
linkage arms is identlfi,ed at 21 and 22 in Fig. 1, the other
pair being identifi,ed at 23 and 24 i,n Fi,g. 2. As will be obvious
from Fig. 3, the twin pairs of parallelogram linkages are spaced
apart horizontall~ an amount generally equal to the space
between the vertical mem~ers 16 and 17.
Extendable and retractable motor elements, taking
form of hydraulic cylinders 31 and 32 (,Figs. 1 and 2), are
pivotally attached to the base frame and extend upwardly to
be pivotally attached to parallel li,nkage components 24 and 22,
respectively. Load transfer members 34 axe pivotally attached
to, and extend between the linkage components 23-24 and 21-22.
The vertical members 16 and 17, which carry the twin, lower
parallelogram linkages, are braced by the diagonals 59 which
extend to the base frame.
The free ends of the twin parallelogram linkage members
! ~ 2 ~
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23-24 and 21-22 are p.;votally connected to a vertical post 36,
~hich may be of generally square configuration, and whose width
spans the horizontal distance between the twin pair of linkage
arms, as will be evident from Fig. 2.
An upper, or additional parallelogram linkage is
formed by twin mem~ers 37 and 38 which are spaced vertically
from each other and w~ich have bifurcated ends pivotally attached
to the upper port;on of the post 36. A further extendable and
retractable motor eIement, taking the form of the hydraulic
cylinder 3~, is pivotally attach.ed to the b.ase of post 36 and
extends to a suitabIe pivotal attachment 3~A ~Fig. 2~ to the :
lowermost linkage arm 38. Load transfer member 41 is pivotally
attached to the~members.37 and 38 and spans the vertical
distance between them. The ends of the li.nka~e ar~s 37 and 38
opposi.te the post 36 are pivotally attached to a second vertical
~J~
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~L~7 ~37
post 42 and the post 42 carries, by means of suitable support
members 43 and 44 (Fig. 2), a work platform 46 which has a
guard rail structure 47 and a suitable bo~ 48 with suitable
control push buttons. It will be understood that the pressure
in the hydraulic cylinder 39 is controlled independently from
that in the dual cylinders 32 and 33 and that the cylinder 39
has a separate "up" and "down" push button on the control box
48, as do, jointly, the paired hydraulic cylinders 32 and 33.
As indicated at 51 in Fig. 1, a suitable pump and drive motor
may provide the necessary fluid pressure for the cylinders,
pressurization of the working side of the pistons in the
cylinders being controlled, as previously mentioned, by means
of push button switches in the control box 48, these switches
serving to energize and deenergize appropriate solenoid valves
in the hydraulic line (not shown).
In operation, the assembly, initially, will have the
stabilizing jacks folded against the side of the base frame
and these are extended and leveled as shown in Fig. 1. The
retracted or folded position of the structure is indicated
in broken lines at A in Fig. 1 and is also shown in Fig. 2
The control ~8 may then be manually operated by the occupant
of the work platforms to extend the hydraulic cylinder 39
thereby raising the work platform to the position indicated
at B in Fig. l. Alternatively, the hydraulic cylinders 32
and 33 may be extended while leaving the cylinder 39 retracted
and this places the work platform in the position indicated
at C in Fig. 1. If, while maintaining the cylinders 32 and
33 extended, the hydraulic cylinder 39 is extended, the
linkage 37-38 will assume its solid line position of Fig. l
and the work platform will be raised to its uppermost position.
By releasing the control buttons at the proper time, the work
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platform may be locked in position at any desi.red height
between the folded position (A) of Fig. 1 and its extended
(solid line) position of Fig. 1. By simultaneously retracting
or extending hydraulic c~linder 39 with the opposite action
occurring with the paid cylinder~ 32 and 33, the work platform
may be moved in a generally hori.zontal path., for example,
between the broken line positi.ons C and D of Fig. 1. :~
These pivotal attachments mentioned abo~e for the
several pairs of t~in li.nkage arms may be accomplished by use
of adjustable bolts, as sh.own in Fig. 2. For example, in
this preferred em~odiment the t~in pai.rs of linkage arms 21-22
and 23-24 are bolted at one o~ their ends to two inner plates
or ears 53 connected to the faci.ng surfaces. of the stationary
members 16 and 17, as better shown in Fig. 3.
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