Loader with a controlled vertical path of a working implement

Details Loader with a controlled vertical path of a working implement Loader with a controlled vertical path of a working implement

2000-03-31

2001-12-04

Underwood, Donald W. (Department: 3652)

Material or article handling

Vertically swinging load support

Shovel or fork type

C414S685000

Reexamination Certificate

active

06325589

ABSTRACT:

FIELD OF THE INVENTION
The present invention is generally directed to a loader having a lift boom assembly mounted to a vehicle frame for raising up and lowering down a bucket or other working implements attached to a forward distal end of a lift boom. More specifically, the invention pertains to a loader whose lift boom assembly is so configured as to move the bucket along a controlled vertical path of travel with enhanced stability.
DESCRIPTION OF THE PRIOR ART
Use has heretofore been made of self-propelled loaders capable of, e.g., dumping such a load as bulk material into a container or truck. Typical examples of the loaders include a skid steer loader which is usually small in size but has an excellent maneuverability owing to its discretely driven wheels or caterpillars. Such loaders are provided with a lifter device which mounts a bucket or other working implements to a vehicle frame in an elevationally movable manner.
A prior art skid steer loader with a typical lift boom assembly is illustrated in FIG.
1
. As shown, the skid steer loader includes a vehicle frame
10
having upright supports
12
positioned at the rear section of the frame
10
. Pivotally attached to the upright supports
12
are a pair of laterally spaced lift booms
14
which have a working implement or tool, e.g., bucket
16
, mounted between the forward free ends thereof. Vertical movement of the lift booms
14
and the bucket
16
relative to the frame
10
can be caused by means of double acting boom cylinders
18
arranged on opposite lateral sides of the frame
10
. A bucket cylinder
20
is utilized in causing the swinging movement of the bucket
16
relative to the lift booms
14
.
With the loader illustrated in
FIG. 1
, the bucket
16
has a tendency to move, responsive to the elevational movement of the lift booms
14
between lowered and raised positions, along a heavily curved vertical path of travel
22
forming a part of a circle whose center lies at the pivot point
24
of the respective lift boom
14
. At about midheight point of the vertical travel path, the bucket
16
exhibits the greatest overhang OH, wherein the term “overhang” means the distance measured from the center axis of the front wheel
26
to a vertical plane on which the pivot axis of the bucket
16
lies, during the elevational movement of the bucket
16
. The prior art loader shown and described above has a disadvantage in that it becomes highly unstable as the lift booms and the loaded bucket are raised up and lowered down, due to the fact that the overhang OH directly affecting the stability of the loader grows too great at the midheight of the vertical travel path of the bucket
16
. Unstableness of the loader may lead to vehicle tipping in the worst circumstances.
In an effort to provide solution to the problem pointed out just above, U.S. Pat. No. 5,609,464 issued Mar. 11, 1997 to John M. Moffitt et al. discloses a lift boom assembly for a loader machine including a pair of laterally spaced interconnected lift arms having a tool mounted between forward ends thereof. Each lift arm includes a main lift link having upper and lower connecting portions at a rear end thereof. A second lift link is pivotally connected to the upper connecting portion of the main lift link and partially controls movement of the respective lift arm. The opposite end of each second lift link is pivotally connected to a frame of a machine on which the lift assembly is mounted. Movement of the lift arms is further controlled by a pair of control arms. A lower end of each control arm is pivotally connected to the frame. When the boom assembly is in a lowered position relative to the frame, a second or upper end of each control arm extends upwardly and rearwardly from the lower end and is pivotally connected to the lower connecting portion of the respective main lift link. In response to vertical movement of the boom assembly between raised and lowered positions, each control arm swings forwardly and rearwardly of its true vertical position to alter the movement of the lift arms and such that the tool is elevationally moved along a generally linear vertical path. A pair of extendable and retractable drivers provide powered vertical movement to the lift assembly and the tool carried thereby relative to the frame.
According to the lift boom assembly taught in the 464 patent, there is no denying the fact that the tool or bucket attached to the forward ends of the lift arms can be moved along a generally linear vertical path of travel between the lowered and raised positions, thus significantly improving the overall stability and the load lifting capacity of the loader. The boom assembly is however disadvantageous in that it requires a pair of supports of substantial elevation for supporting itself high enough to assure elevational movement of the tool along the intended linear vertical travel path. Apparently, the tall supports and the elevated mounting position of the lift boom assembly result in an elevated weight center of the loader, a reduced overall stability and lifting capacity, and a marred visibility to the rear sideward direction. Another shortcoming with the lift boom assembly referred to above is that the overhang of the tool or bucket from the center of a front wheel remains great for the substantial part of its elevational movement except the initial short range of upward movement. Needless to say, it is desirable to reduce the overhang as far as possible, inasmuch as the greater the overhang, the smaller the load lifting capacity.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a loader with such a controlled working implement travel path that can reduce the overhang of a working implement throughtout the elevational movement thereof, thus increasing the load lifting capacity and improving the overall stability of the loader.
Another object of the invention is to provide a loader whose lift booms are mounted directly to a vehicle frame at such a low position as to lower the loader weight center, increase the load lifting capacity and attain a widened rear side visibility of the loader operator, while avoiding the use of separate boom supports.
With these objects in view, there is provided a loader comprising: a frame; a pair of laterally spaced lift booms disposed at opposite lateral sides of the frame for elevational movement between lowered and raised positions, each of the lift booms having forward free end which carries a working implement and a rear proximal end articulately mounted to the frame; a pair of front control links arranged on the opposite sides of the frame, each of the front control links having a first end pivotally attached to the frame at a first pivot point and a second end pivotally connected to the rear proximal end of the respective lift boom at a first connection point; a pair of rear control links disposed at the rear of the front control links and arranged on the opposite sides of the frame, each of the rear control links having a first end pivotally attached to the frame at a second pivot point positioned rearwardly and downwardly of the first pivot point when the lift booms are in the lowered position and a second end pivotally connected to the rear proximal end of the respective lift boom at a second connection point which remains rearwardly and upwardly of the first connection point when the lift booms are in the lowered position; and actuator means for causing the respective lift boom to move along with the working implement between the lowered and raised position.


REFERENCES:
patent: 4355946 (1982-10-01), Wykhuis et al.
patent: 5169278 (1992-12-01), Hoechst et al.
patent: 5518358 (1996-05-01), Aschroft et al.
patent: 5609464 (1997-03-01), Moffitt

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