Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
The present invention relates to a load handling
gantry having a beam supported at it~ ends typically by
pairs of pivotally cor.nected downwardly divergent legs,
and more particularly to a means for providing such
gantries with a steerable power drive mechanism.
BACKGROUND OF THE INVENTION
Load handling portable ~antry cranes are well
known in industry for the lifting and movement of heavy
loads from one location to another within a shop or other
industrial facility. A typical gantry of this sort is
described in Canadian Patent 926,822. To move such
~antries from one place to another, or to turn the gantry,
swivel casters are provided ad~acent the bottom of each
supporting leg, and the gantries are elther manually
pu3hed or pulled about, or are moved with the aid of a
tractor. Such gantries may also be mounted on rails for
slmple back-and-forth movement, again usually by hand, but
also by means of a power driven wheel.
The manual movement of gantries can be difficult
particularly when heavy loads are involved, and although
this can be alleviated to a certain extent by the use of
rails, freedom of movement is then lost. There can also
be an element of danger from swinging loads or when trying
to control the gantries when being moved.
SUMMARY OF THE INVENTION
Accordlng to one ob~ect of the present
invention, it is sought to mitigate the disadvantages of
prior gantries by providlng means by which the gantries
can become ~elf-propelled, which means further permit the
gantries to be steered within a confined space.
AcGording to the present invention, there is
provided a self-propelled steerable gantry comprising: an
elevated load carrying beam; individually adjustable
downwardly divergent pairs of legs spaced apart lengthwise
o~ the beam proximal the ends thereof for supporting the
beam; tie means between the lower ends of the legs to
maintain and ad~ust the angularity between the legs; the
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tie means having a length whlch i3 substantially shorter
than the lengtll of the beam; and gro~lnd engaging mobile
mounting~ for the gantry includin~: (1) a castering wheel
disposed ad~acent the lower end of one of each pair of
downwardly divergent leg~ to swivel about an upright axls
perpendicular to the longitudinal axis of the tie means;
(2) a fix~d orientation wheel disposed adjacent the lower
end of the other of the pairs o~ legs to be aligned with
the longitudinal axis of the tie means; (3) a prime mover
operatively connected to each of the fixed orientation
wheels to independently rotate the wheels in a forward or
reverse direction; and (4) control means operable to
independently actuate the prime mover means for forward or
reverse rotation of the fixed orientation wheels.
RIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention
will now be described in greater detail and will be better
understood when read in con~unction with the following
drawings, in which:
Figure 1 is a front elevational view of a gantry
crane including the drive mechanism of the present
invention:
Figure 2 is a side elevational view of the
gantry crane oE Figure 1;
Figure 3 is a side elevational view of a portion
of the gantry showing the drive mechanism in greater
detail;
E'igures 4a and 4b are schematical
representations of the ~antry in di~ferent turning modes;
and
Figure 5 i~ a wiring diagram for the gantry
drive mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Load handling gantries are as aforesaid well
known and will therefore be described only briefly with
reference to Figures 1 and 2 illustrating a typical 5 ton
portable gantry. It will be understood however that the
gantry crane as shown is merely exemplary, and that the
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drive mechani~m for gantries described herein is adaptable
to gantries o~ different c~n~tructions.
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With reference now to Figures l and 2, it will
be seen that gantry 1 comprlses a load-carrying member ~,
such as an I-beam comprlsing a vertical web 3 and upper
and lower longitudinally ex~ending Elanges 5 and 6. Beam
2 is suppor~ed adjacent its opposite ends by similarly
structured pairs oE downwardly divergent legs 10. The
legs have their upper ends connected with the beam by
means o~ a cross member 12 to which each of the upper ends
is pivotally connected at pivot connections 14 and 15.
The beam itsel~ is suspended erom cross member 12 by means
o~ weldments, bolts or any other strong load bearing
connection means. Each leg 10 comprises a -telescopically
associated inner and outer sleeve 20 and 21, res~pectively,
so that the length oE the legs can be independently
adjusted by means of, for example, a pin (not shown)
insertable through holes (also not shown) formed in the
inner and outer sleeves.
The load may be suspended Erom beam 2 in any
suitable manner, but is usually slung Erom an electric
power hoist 25 suspended Erom a trolley 26 whose wheels 27
ride on the lower Elange 6 of beam 2 ~or travel
therealong. Other accoutrements are typically associated
with the hoist and trolley as will be appreciated by those
skilled in the art, including a spring-loaded takeup 28
for the power supply cord, but as these features are well
known, and have relatively little to do with the present
inventionr further description thereoE will be delete-l.
Particularly under load conditions, the lower
ends oP legs 10 will tend to spread unless restrained and
it is thereEore the usua] practise to incorporate tie
means 30 between the lower ends oE each pair oE legs 10.
I'he tie means may be Eor example a flexible piece oE chain
or rope, but more typically, greater stability and
strength is to be obtained by means oE a rigid tie bar 30
with or without length adjustlnent means. If length
adjustment means are incorporated, the tie bar will
usually comprise inner and outer telescopically associated
sleeves (not shown) selectively adjustable for length by
means of a retractable pin which cooperates with holes
formed in the sleeves in much the same manner as describe~
above with :respect to the adjus-tability of legs 10. To
accommodate the relative angling between legs 10 and tie
bar 30, the joints between them is by means o~ horizontal
pivots 31 extending through b.rackets 33 provided at the
end of each leg and the adjoining portion oE ti.e bar 30
engaged ~hereby.
The combination of adjustable legs 10 and tie
bar 30 permits a substantial range of independent and
coordinated variation in the height and spread of the
gantry which o:f course lends the versatility needed to
accommodate different load sizes and weights, available
clearances, and also the sur:Eace over which the gantry
will travel. .
In the gantry as shown in Figures 1 and 2, legs
10 are braced by means of struts 40 respectively disposed
on opposite sides o:E beam 2. The upper ends ~1 of each
strut are mounted on a second cross member ~2 by means of
a pivot 44. The lower end 46 of each strut 40 is coupled
to its adjacent leg 10 by a simi.lar pivot ~7 :Eixed on the
leg as shown schematically in Figure 1.
To provide the gantr,y as described above with
mobili-ty, it has been the practice hitherto to moun~
swivel casters 50 beneath opposite ends of each tie bar
30, and to push or pull the gantry either manually or with
the aid of some sort o:E tractor. It is now pro~osed to
replace one oE the casters at the corresponding ends o.E
each tie bar with a power drive assembly 60 as will be
described hereinafter in greater detail.
With refe:rence to Figure 3, each assembly 60
consists oE an outer (metallic) hou.sing 62 which supports
an axle 63 ~or a ground-engaging d:rive wheel 65 and a
prime mover 69 such as a three-phase electric motor
coupled to a gear box 71 with a drive sprocket 73
extending laterally therefrom. Drive wheels 65 include a
relatively large laterally disposed drive sprocket 75
aligned with and connected to drive sprocket 73 by means
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of a drive chain 78 ~or ro~ation o~ the drive wheel in
either the forward or reverse direc-tion. ~ suitable
motor/gear box combination found to provide goocl results
by the applicant is a Marathon coupled to an OH10*MQ206
drivP.
To connect housing 62 to the gantr~ adjacent the
lower ends oE one o each pair of legs 10, a metal ~Elange
76 is welded or bolted to the underside of tie bar 30
adjacent the respective end ther~oE to Elush fit against
the upper surface of housing 62. The two surEaces are
then fastened together such as by means of bolts 79 so
that the housing can be removed iE requlred for
replacement or repair oE the drive assembly. Each of
drive wheels 65 rotates about a fixed axle and is not Eree
to pivot so that when the drive assernbly is installed, the
wheel is aligned with tie bar 30 to be perpendicular to
the longitudinal axis oE the gantxy.
Each drive wheel is independently actuatable for
separate operation in either the ~orward or reverse
direction and, of course, neu-tral. An elec-trical control
box 80 is connected to the gantry between one oE legs 10
and the ad~acent strut ~0 in any suitable manner. Power
to the unit is input via power cord 82 and in an
embodiment constructed by the applicant, three-phase 60 ~Iz
AC current at either 440 or 575 volts is supplied to
operate the unit. If required, the unit can be adapted to
operate on a 115 or 220/1/60 power supply. Control of the
drive units is preferabl~ providefl by means oE a handheld
five-button pendant control 8~ held by the operator in
both hands for thumb actuation of the forward and reverse
buttons on each side a~ well as a stop button. The
bu-ttons on each side oE the control may be colour-coded to
match the colours of each of housings 62. In the wiring
diagram of Figure 5, left hand wheel-drive housing is
coloured yellowr whereas the right hand housing is blac]c,
and on the pendant control, the respective control bu-ttons
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will be coloured corresponclin~ly to provide a visual
correlation Eor the operator. To provlde ~or sorne ~lac~
in the electrical cords 87 and 8~ providing power to the
respective drive assemblies to accommodate adjustments to
the lengths oE legs 10, a few extra loops 89 oE cord are
provided in each circuit to the drive assemblies.
The electrical wiring and controls for the
present gantry illus-trated in the schematic of Figure 5
will be self-evident to those skilled in the art and will
not therefore be described in further detail herein, other
than to indicate that the applicant has found it desirable
to incorporate a micro-logic so~-t start into the circuitry
to minimize load swinging at the commencement of travel.
In operationl it will be evident Erom the
foregoing description tha-t in order to propel the gantry
in a straight line in ei-ther -the forward or reverse
directions, the operator will actuate both drive
assemblies in the same direction simultaneously. Wi-th
reference to Figure 4a, -the gan-try can be made to rotate
about its vertical axis in a clockwise or counterclockwise
direction by simultaneously actuating both drive
assemblies in opposite directions. Broader radius turns
may be accomplished as shown in Figure ~b by allowing one
drive to idle while actuating the opposite drive in the
desired direction oE the turn.
Drive wheels 65 may be standard semi-steel or
urethane ground-engaging.
The principles, preferred embodiments and modes
of operation and construction oE the present invention
have been described in the Eoregoing disclosure. The
invention which is lntended to be protected herein however
is not to be construed as limited to the particular
embodiments disclosed, since these embodiments are to be
regarded as illustrative rather than res-trictive.
Variations and changes may be made by others without
depar-ting Erom the spirit and scope oE the invention.
Accordlngly, it is expressly intended that all such
variations and changes which fall within the spirit and
scope o the invention be included within the scope o:E the
following claim.
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