Material handling vehicle

A vehicle for handling heavy loads and moving them short distances. The vehicle has a lifting linkage arrangement that allows the center of gravity of the load to be carried over the front wheels or between the front and rear wheels after the initial lifting phase. Initial lifting is aided by an outrigger and loadrest. This design therefore eliminates the need for a heavy vehicle using counterweights and provides a vehicle that has maximum maneuverability and lifting capacity.

BACKGROUND OF THE INVENTION 
There are known and commercially available a number of different designs of 
vehicles for handling and moving loads, especially loads on pallets, short 
distances. Vehicles commonly referred to as "forklifts" have been used for 
many years in numerous industrial and other applications. The forklift has 
a fork-vertical slide mechanism for engaging and lifting the load, and the 
moment of the load is offset by the counter-moment of the vehicle. The 
axle of the front wheels of the forklift provides the fulcrum in both the 
stationary-load position and the dynamic-carry mode. By tilting the mast 
containing the fork-slide mechanism, the moment of the load is reduced 
somewhat, but a substantial counterweight is still required, and the 
forklift cannot carry a load in excess of its own weight. 
There is also known and commercially available a material handling vehicle 
which can lift and carry loads in excess of its own weight. This vehicle 
has a variable wheel base provided by a design that permits the front 
wheels, which are mounted on "legs", to be extended as the load is lifted 
and carried. The rear wheels or wheels can also be extended or withdrawn. 
In this manner, the lifting moment is eliminated since the load will be 
between the front and rear supporting wheels. Thus, there is no necessity 
for a counterweight. However, with this vehicle, the load must be lifted 
and carried between the front wheels thus limiting the use of the vehicle 
to those situations where space permits the vehicle to travel with a wide 
stance. Also, because of the mechanism required for extending and 
withdrawing the wheels, the vehicle is relatively expensive. 
There is therefore a need for a material handling vehicle that is capable 
of lifting loads in excess of its weight and which is small enough in 
physical size to be useful in applications where space is limited. There 
is also a need for a relatively inexpensive material handling vehicle that 
can carry loads comparable to the standard forklift in industrial 
applications where space is limited and also in other applications as 
well. 
SUMMARY OF THE INVENTION 
The material handling vehicle of the invention is a fixed wheel base stable 
vehicle supported on either three or four wheels. Most of the machine 
weight is over the rear axle which also serves as the steering axle. 
Unlike the prior art machines, the lift mechanism does not utilize a 
fork-slide mechanism, but rather the lifting fork is secured to a linkage 
mechanism that is basically a double four-bar linkage arrangement. With 
this linkage, the load can be lifted and swung rearwardly to a carry 
position where the center of gravity of the load is over the front axle or 
between the front and rear axles of the vehicle. During the lifting mode, 
an outrigger is utilized until the center of gravity is shifted rearwardly 
over the front axle. The dual four-bar linkage that forms the lifting 
mechanism is hydraulically supported and operated, and with the aid of the 
outrigger and load rest mechanism, the vehicle can carry loads greatly in 
excess of its weight.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
The material handling vehicle of the invention has a main vehicle frame 
indicated generally by the reference numeral 10 that supports a front axle 
12 carrying wheels 14. The rear of the frame 10 is supported from a 
steerable rear axle assembly, indicated generally by the reference numeral 
16, which assembly contains turnable rear wheels 18. The connection 
between frame 10 and rear axle assembly 16 is a rocker pin 104 which 
allows front and rear wheels to make firm ground contact in rolling 
terrains. Affixed to the rear of the main frame 10 are vertical frame 
members 20, and on the left side of the vehicle (FIG. 1) cab frame members 
22 define an operator's station 24 in which are located a steering wheel 
26 and control levers 28. 
On the right side of the machine (FIG. 2) a housing 30 encloses a power 
unit (not shown) of any suitable type either gasoline or diesel powered. 
The power unit supplies the necessary power for the hydraulic system (not 
shown) which operates and controls the lifting assembly, indicated 
generally by the reference numeral 32, and the outrigger assembly 
indicated generally by the reference numeral 34. The power unit also 
drives pumps (not shown) which supply hydraulic power to hydraulic motors 
(not shown) contained inside of short axles 84. The hydraulic motors power 
the wheels 14 and 18. 
The outrigger assembly 34 includes a foot pad 36 engagable with the ground 
upon which the vehicle is resting which foot pad 36 is affixed to a pair 
of vertical supports 38. The outrigger assembly 34 is raised and lowered 
by means of a parallelogram or four-bar linkage arrangement connected to 
each of the two vertical uprights 38. The four-bar linkage arrangement 
includes a pair of parallel horizontal links 40 each pivotally connected 
at one end to a vertical support 38. The other ends of horizontal links 40 
are pivotally connected in a suitable manner to a portion of the main 
frame 10. Each of the upper ones of horizontal links 40 are joined at 
their rear ends by a cross bar 42 that has affixed to it a lifting arm 44 
that extends upwardly and forwardly from the cross bar 42. A hydraulic 
cylinder 46 is pivotally mounted at a suitable place to a portion of the 
main frame 10 and has its operating rod 48 pivotally connected to the 
lifting arm 44. Thus, when the hydraulic cylinder 46 is actuated and the 
operating rod 48 extended, the foot pad 36 will be lowered to the ground 
and held in that position by reason of the force of the hydraulic cylinder 
46. 
Because of the four-bar linkage arrangement, the vertical supports 38 will 
always be raised and lowered substantially perpendicularly to the main 
frame 10. With a load rest bar 50 extending horizontally across the top of 
the vertical supports 38, and through actuation of the lifting assembly 32 
as described more fully hereinafter, the load can be supported on the bar 
50 while the load is being carried thus providing further stability for 
the vehicle. 
Referring now to FIGS. 3 and 4, the lifting assembly 32 will be described. 
FIG. 3 is a side elevational view of the lifting linkage with the left 
portion of the linkage removed for purposes of clarity. A first four-bar 
linkage is provided by a main advance arm 52 pivotally connected to the 
main frame 10 and a secondary advance arm 54 parallel to arm 52. Both arms 
52 and 54 are pivotally connected at one end to the main frame 10 and are 
pivotally connected at their other end to one leg of a triangular shaped 
upper linkage frame 56. 
As shown in FIG. 4, a second pair of main and secondary advance arms 52 and 
54 corresponding to the first pair of arms 52 and 54 are also pivotally 
connected at one end to the main frame 10 and at their upper ends to the 
upper linkage frame 56. Arms 52 are joined by a cross member 58 which is 
pivotally connected to the free hand of an operating rod 60 of a hydraulic 
cylinder 62. Hydraulic cylinder 62 is pivotally connected also to the main 
frame 10 and provides the power for operating the advance mechanism. 
A second four-bar linkage is provided by the vertical leg 64 of the upper 
linkage frame 56 which has pivotally connected at its ends the main 
lifting arm 66 and the secondary lifting arm 68. Arms 66 and 68 are 
parallel to each other and parallel to corresponding arms 66 and 68 
connected at the right side of the upper linkage frame 56 (FIG. 4). At the 
outer ends of the arms 66 and 68, there is pivotally connected a 
rectangular shaped load frame 70 which will generally be provided with an 
appropriate accessory such as lifting forks, a bucket, etc. (not shown). 
The upper linkage frame 56 also supports a hydraulic lift cylinder 72 which 
has the free end of its operating rod 74 connected to a cross member 76 
joining the lifting arms 68. The hydraulic cylinder is pivotally connected 
to a supporting frame consisting of a pair of rotating links 78 and 80 
joined by a connecting member 82 which provides the pivotal mounting for 
the end of the hydraulic cylinder 72. 
The load frame 70 may also be tilted by the hydraulic cylinder 110 which is 
pivotally connected to the cross-member 76 and the load frame 70. Two 
tension hangar members 108 are also connected at cross-member 76 and 
extend downward to a pivotal connection with the main lifting arms 66. 
Thus, actuation of the hydraulic cylinder 72 supports and activates 
cross-member 76 which in turn lifts the main lifting arms 66 through the 
tension hangar members 108, and thus the load frame 70 is supported at the 
outer ends of arms 66 with the tilt cylinder 110 being the stabilizer and 
vertical control. 
With the arrangement thus described, it will be evident that the lifting 
assembly 32 includes two four-bar linkages interconnected by linkage frame 
56. This triangular shaped linkage frame 56 will "float" with the two 
four-bar linkage arrangements and will always have the vertical legs 64 in 
a substantially vertical position. The upper linkage frame 56, in 
providing support for the hydraulic cylinder 72, transmits the forces from 
the upper linkage arrangement to the lower linkage arrangement and then to 
the main frame 10. 
With the foregoing described lifting assembly, the hydraulic cylinder 62, 
by operating the lower four-bar linkage, provides the capability of 
extending the load frame 70 forwardly and rearwardly and also provides 
some of the lifting function. The upper linkage arrangement that is 
powered by the hydraulic cylinder 72 provides the main lifting force for 
the load frame 70. The entire lifting assembly 32 thus permits the load 
frame 70 to be lowered and extended forwardly to pick up a load in almost 
any position, including a load resting on the ground. With the assistance 
of the outrigger assembly 34, the load can then be lifted sufficiently to 
clear the front wheels 14 and then moved rearwardly to shift the center of 
gravity of the load over or rearwardly of the front axle 12. Once the 
center of gravity is thus shifted rearwardly, lifting of the load can 
continue using primarily the upper linkage frame operated and powered by 
the hydraulic cylinder 72. If desired, the outrigger assembly 34 can be 
also lifted and the load rested upon the bar 50 while it is being carried. 
The double four-bar arrangement of the lifting assembly 32 thus provides a 
very flexible lifting arrangement that adds versatility to the vehicle and 
permits the vehicle to lift and carry loads greatly in excess of the 
weight of the vehicle. 
Referring now to FIGS. 5 and 6, there is shown a steering mechanism for the 
vehicle which, through a very simple arrangement, provides for excellent 
maneuverability of the vehicle. The rear wheels 18 are each supported on 
short axles 84 each of which is in turn connected to a vertical arm 86. 
The upper ends of vertical arms 86 are affixed to plate 88 which is one 
leg of a triangular control linkage. Plate 88 is turnable about pivot 90 
connected to a rocker arm 106. The second leg 94 of the triangular control 
linkage is pivotally connected at one end to plate 88 and at the other end 
to the angular leg 92 which in turn is pivotally connected at one end to 
tie rod 96 and at the other end to rocker arm 106. The hydraulic cylinder 
98 is pivotally connected to the rocker arm 106 and has its operating rod 
100 pivotally connected to pin 102 which in turn is affixed to the tie rod 
96. Thus, when hydraulic cylinder 98 is actuated, tie rod 96 will be 
shifted to the right or left which in turn rotates the control linkage to 
the right or left causing plates 88 to pivot about pivot points 90 thus 
turning the wheels 18. With this arrangement, it is obvious that a very 
simple but quite effective hydraulic steering system is provided that is 
easily actuated by a single control from the operator's station 24. 
Having thus described a preferred embodiment of the invention, it will be 
obvious to those skilled in the art that various revisions and 
modifications can be made to the preferred embodiment without departing 
from the spirit and scope of the invention. It is my intention however 
that all such revisions and modifications as are obvious to those skilled 
in the art will be included within the scope of the following claims.