Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVEMENTS IN OR RELATING TO
MATERIAL HANDLING VEHICLES
FIELD OF TH~ INVENTION
The present invention is concerned with improvements in
or relating to material handling vehicles and especially,
but not exclusively, to the type of such vehicles commonly
known as lugger trucks which carry a drop-off container for
the material to be handled.
1~ REVIEW OF THE PRIOR ART
Lugger trucks are a specific type of material handling
vehicle that are equipped with a loading/unloading mehanism
for the drop-off container comprising two
transversely-spaced, parallel lifting arms, which are
pivotally mounted on the vehicle for movement in a
longitudinal forward/rearward direction about a horizontal
axis located adjacent the rear end of the vehicle. To load
a container the lugger truck is backed close up against one
end thereof and the lifting arms are pivoted backwards until
they extend over the container, when a set of lifting slings
carried by the arms can be a~tached to projections at the
sides of the container. The arms are then pivoted forward
to simultaneously lift the container and move it onto the
body of the vehicle.
The system is simple and easy to use and it has been
widely adopted. For the sake of cost reduction it is
preferred to use a standard vehicle chassis of standard
height (i.e. rather than a special more expensive low-bed
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chassis as is employed for high loads~, while at the same
time the whole vehicle with the maximum size container in
place must meet the usual transport gauge requirements for
public road use, particularly the maximum height requirement
for it to pass under bridges.
The maximum load that can be carried is determined
principally by the axle load permitted in the jurisdiction
in which the vehicle operates, and authorities have become
much more strict in this regard in view of the road damage
that can be caused by overloading. It is therefore clearly
of advantage to distribute the load between the front and
rear axles to the maximum of their respective capaci-tes, or
- proportionally to the maximum, but it becomes difficult to
do this with a standard truck chassis because of the
geometrical constraints in designing a suitable arm system.
Thus, the arms are fixed in length and must be short enough
to meet to maximum height requirements, yet must be able to
lift the fully-loaded container high enough to clear the
back end of the vehicle, and also deposit it as far forward
a possible, while at the same time maintaining the
longitudinal stability of the vehicle during loading and
unloading; in practice this is difficult to do. This
preferred distribution of the load proportionally between
the axles, rather than the rear axles being relatively
heavily loaded while the front axle (or axles) is relatively
lightly loaded, would also be advantageous in improving the
road handling of the fully-loaded vehlcle.
Attempts have therefore been made hitherto to provide
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lugger trucks with loadingJunloading mechanisms which can
slide the container (or containers) in a forward/rearward
direction after its loading on the vehicle platform in order
to accomodate a number of smaller containers on the platform
one behind the other, or to change the load distribution.
These proposals do not however appear to have found
widespread acceptance, mainly it is believed because of the
cost and complexity of the mechanism required to allow the
lifting arms to move in unison down either side of the
platform, while supporting a loaded contalner, and/or the
problem of mounting such mechanisms on a vehicle chassis of
standard height while meeting maximum height requirements.
DEFINITION OF THE INVENTION
It is an object of the present invention therefore to
provide a new material handling vehicle with which the load
distribution between the front and rear axles can be
adjusted in a manner that permits an increase in load
carrying capacity.
It is another object to provide a movable load carrying
platform for a lugger truck which allows the load carried by
the lugger truck to be moved forward on the truck after
loading thereon to increase load carrying capacity and
stability.
It is a further object to provide such a platform that
can be mounted on a standard truck chassis with a minimum of
modification and allow the use of a standard lugger fixed
length arm lifting mechanism, therby minimizing cost and
complexity
In accordance with the present invention there is
provided a load-carrying platform for use with a lugger
truck having front and rear running wheels and a truck
chassis, comprising:
a platform member having front and rear ends and
providing a platform surface on which a drop-off container
can be deposited;
the platform member comprising a pair of container
lifting arms mounted adjacent the rear end of the platform
member about a horizontal pivot axis for movement between a
rear position in which a container on the ground is engaged
and disengaged, and a forward position in which a container
is disposed on the platform surface, and motor means
connected between the platform member and the lifting arms
5 for moving the arms in said movement;
the platform member also comprising bearing means on
its underside for engagement with cooperating bearing means
on the truck chassis to permit forward/rearward movement of
the platform member on the truck chassis, retaining means
operable between the platform and the truck chassis to
maintain the platform in engagement with the truck chassis
during said forward/rearward movement, and motor means for
connection between the platform member and the truck chassis
for moving the platform member on the truck chassis in such
5 movement;
whereby the platform member is movable to a rear
position in which a drop-off container is loaded onto and
unloaded from the platform member, and to a forward position
with a drop-off container loaded thereon to distribute the
load of the container more evenly between the truck front
and rear running wheels.
DESCRIPTION OF THE DRAWI~GS
A particular preferred embodiment of the invention will
now be described, by way of example, with reference to the
accompanying diagrammatic drawings, wherein;-
Figure 1 is a side elevation of a lugger truck
embodying the invention showing the moveable platformthereof in its rear loading and unloading position and a
container on the ground ready for loading;
Figure 2 is a similar view of the rear end only of the
lugger truck with the moveable platform still in its rear
loading and unloading position and the container loaded
theron, part of the platform being broken away for clarity
of illustration of the pla-tform moving mechanism.
Figure 3 is a view similar to Figure 2 showing the
platform in its forward travelling position, part being
broken away to show the arm moving mechanism;
Figure 4 is a perspective view from the rear and above
to show the structure of the moveable platform, part of the
floor being broken away for this purpose;
Figure 5 is perspective view of a detail of the
connection between the platform and the means for moving it;
Figure 6 is a perspective view of a detail of the
manner in which the platform is mounted for movement on the
truck chassis members, the view being taken generally on the
- 5 -
line 6-6 in Figure 3;
Figure 7 is a plane cross-section taken on the line 7-7
in Figure 4;
Figure 8 is a plane cross-section taken on the line 8-8
in Figure 2 and in Figure 4;
Figure 9 is a plane cross-section taken on the line 9-9
in Fiyure 7~ and
Figure 10 is a plne cross-section taken on the line
10-10 in Figure 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In this preferred embodiment the invention is shown
employed with a standard single front-steering axle truck
chassis of about 29,000 Kg. (64,000 pounds) gross weight
capacity consisting of an operator's cab 10, a pair of front
steerable wheels 12 mounted on a front steering axle 14, a
longitudinal chassis frame 16 having thereon two
transversely spaced parallel chassis members 18, and two
longitudinally spaced rear axles 20. The two rear axles
each carry four wheels in two pairs for maximum
load-carrying capacity. It is also desired to load the
front steering axle 14 to its maximum capacity and
relatively high load capacity steering axles of about 9,000
Kg. (20,000 pounds) are now available, so that it is
possible to distribute the load with 9,000 Kg. (20r000
pounds) carried by the front axle and the remaining 20,000
Kg. (44,000 pounds) carried by the rear axles. Steering
axles are usually intended to be used with single wheels 12
s~
and if greater front end load carrying capacity is required
this can be obtained in known manner by using two coupled
steering axles in tandem (not shown), whereupon the gross
weight capacity is increased by the extra 9,000 Kg (20,000
pounds) to about 38,000 Kg (84,000 pounds). Another way in
which the gross weight capacity is sometimes increased is by
use of what is known as an ~airlift~ axle, with or without
castering mountings, between the front and rear axles, the
wheels on this axle being lifted from the road by the driver
when a tight turn is to be made.
The truck chassis supports a moveable load carrying
platform, indicated generally by the reference 26, for
longitudinal forward/rearward sliding movement between a
rear loading/unloading position shown in Figures 1 and 2 and
a front travelling position shown in Figure 3, the platform
being retained transversely and guided for such movement by
longitudinally spaced side retainers 28 attached to the
sides of the members 18. It is moved as required by a
hydraulic piston and cylinder motor 30, the motor being
controlled by operation of the appropriate valves at a
control section 32 just behind the cab 10. The platform
carries a loading/unloading structure of known type for a
container 34, this structure consisting of a pair of
fixed-length, transversely-spaced parallel lifting arms 36
pivoted about respective horizontal coaxial pivot shafts 38,
and connected at their top ends for simultaneous movement by
a transverse connecting rod 40, from which extends a pair of
slings 42 terminating in hooks that engage lifting bosses on
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the container sides. The arms are moved as required between
a rear loading/unloading position shown in solid lines in
Figure 1, and a front loaded or travelling position shown in
broken lines in that ~igure by two piston and cylinder
motors 44 mounted on the platform, the motors being
pivotally connected at 46 to the arms and at 48 to the
plat~orm, and also bein~ controlled by respective valves at
the control station 32. The rear end of the chassis 16 is
provided with a pair of transversely spaced hydraulically
operated stabilizers 50 which are extended to engage the
ground while the container is loaded and unloaded, as shown
in Figure 1, their operation also being controlled from the
station 32.
In operation therefore, to pick up a fully loaded
container, the platform is moved to its rearward position
and the truck backed into position against -the end of the
container. The rear stabilizers 50 are extended, the arms
36 swung to the rear and the sling hooks engaged. The
container 34 is now lifted into position on the platform,
which is then moved by its motor 30 to its forward position
for running while the stabilizers are raised. The sequence
is reversed for unloading.
It will be noted that with the platform in its rear
postion shown in Figures 1 and 2 more of its weight is over
the rear wheels 22 than when it is in its forward position
shown in Figure 3, and by careful choice of the amount of
longitudinal movement of the platform it can be arranged
that in the forward position the weight is distributed
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between the wheels proportionally in accordance with their
maximum designed load capacity, increasing the maximum
capacity available and also improving the running road
stability. Moreover, it is possible to obtain this improved
result using arms 36 of sufficiently short length to be able
without difficulty to meet government regulations as to
maximum geight; while giving the effective ~throw~ of much
longer arms that would not meet these regulations.
We have found that by application of the ivention it is
possible to increase the maximum load-carrying capacity of a
lugger truck built on a standard truck chassis of 4.93
metres (194 ins) wheelbase from 21,636 Kg (47,700 lbs)
gross, distributed 18,212 Kg (40,150 lbs) on the rear wheels
and 3,425 Kg (7,750 lbs) on the front wheels to about
26,988 Kg (59,500 lbs) disributed with the same amount on
the rear wheels and the balance on the front wheels, this
distribution requiring -the load platform to be mo~ed forward
about 107 cm (42 ins). In this case a high capacity front
steering axle is employed to withstand the additional load,
which would not have been used in the prior art structures
since such loadings could not be obtained. As described
above, if tandem front steering axles or an intermediate
airlift axle, are employed the gross capacity can be raised
even further.
The platform 26 consists of a flat heavy metal base
plate 52 upon which the container 34 is deposited. The
plate has two vertically-downwardly extending I
cross-section members 54 attached to its underside so that
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the lower flange sits on the horizontal upper surface of a
respective chassis member 18, constituting bearing means
permitting the platform to move freely longitudinally on the
chassis while retained transversly by the members 28 (Fig.
6), which extend upwards and embrace the edges of the
cross-bar. A replaceable metal wear strip 56 and a strip 58
of low-friction material, such as a nylon, are interposed
between each member 18 and the lower flange. Additionally a
suitable lubricant grease can be applied between the moving
surfaces. The underneath of the palte 52 is provided on
either side and immediately adjacent to the load-bearing
pivots 38 with heavy (e.g. 5 cm thick) transverse
reinforcing bars 62. The rear end of the plate is provided
with an upwardly-shaped protion 64 to guide the container on
to the platform, and the sides of the platform are provided
with guide members 66 to centralize the container on the
platform.
The arm members 36 and their operating motors 44 are
mounted on the platform by means of respective pairs of
closely transversely-spaced parallel vertical plates 68
forming respective narrow troughs 70 at each side of the
platform. Each trough therefore provides a separate force
receiving and resisting structure separate also from the
platform, so that its height on the truck chassis can be
made lower than that of the platform so as to maximize the
length of arm that can be used. At their rear ends these
plates are shaped to extend beneath the level of the plate
52, so that the coaxial axes of the pivot shafts 38 are
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F
beneath the plate to again provide for the maximum length of
the arms 36 within ~he permitted height gauge. The motor 30
and its attachments to the chassis and the platform are
subjected to the heavy sliding load of the platform and a
fully loaded container and accordingly the attachment of the
motor piston at 72 (Fig. 5 and 8) is to a special
cross-member 74 attached to the I-members 54, and also
provided with additional vertical connection members 76.
In the embodiment described above the bearing means
between the platform and the chassis employ sliding bearing
surfaces to permit the necessary forward/rearward movement,
but in other embodiments other bearing means may be
employed, such as two transversely-spaced sets of
longitudinally-spaced rollers, preferably mounted on the
underside of the platform.
It will be seen therefore that the invention provides a
new lugger truck having important structural, operational nd
economic advantages over the trucks currently in use~ in
permitting maximum use of the load carrying capacity of the
truck axle employed, while employing standard components,
meeting government regulations with regard to maximum
dimensions, and also improved riding characteristics because
of the better load distribution.
