Crawler vehicle

Details Crawler vehicle Crawler vehicle

2001-07-20

2003-05-20

Hurley, Kevin (Department: 3611)

Motor vehicles

Special driving device

Portable track

C305S134000

Reexamination Certificate

active

06564889

ABSTRACT:

REFERENCE TO RELATED APPLICATION
The application is a U.S. national stage application of copending International Application Serial No. PCT/JP01/01766 filed Mar. 7, 2001 and published in a non-English language.
TECHNICAL FIELD
This invention relates generally to a crawler vehicle and, more particularly, to an improvement in a snow-removing machine.
BACKGROUND OF THE INVENTION
A crawler vehicle having at its front portion a working member (snow-removing section) is disclosed in, for example, Japanese Patent Publication No. SHO-51-30378 entitled “Snow-Removing Machine”. This snow-removing machine comprises a body frame connected to a rear portion of a crawler frame, which has a front portion equipped with a driven wheel and a lower portion equipped with two guide wheels, through a pivot shaft for vertical swinging movement, a snow-removing section mounted at a front portion of the body frame and serving as a working member, an engine mounted on the body frame, a drive wheel mounted to a rear portion of the body frame, and a crawler belt trained around the drive wheel, the driven wheel and the guide wheels.
In addition, during traveling of the crawler vehicle with its snow-removing section held in an inoperative state, a jack is extended to allow the body frame to swing clockwise about the pivot shaft, lifting the snow-removing section to thereby prevent the snow-removing section from hitting an obstacle on the road surface.
FIGS. 6A and 6B
hereof are schematic side elevational views showing operations of the aforementioned conventional snow-removing machine. More specifically,
FIG. 6A
shows that the snow-removing machine in snow removing operation, while
FIG. 6B
shows a state in which a jack
101
remains in an extended condition to allow a body frame
103
to swing clockwise about a pivot shaft
102
such that a snow-removing section
104
is lifted.
When the snow-removing section
104
is lifted, a drive wheel
105
moves downward as shown by arrow {circle around (
1
)}. As a result, the distance M between the center of a driven wheel
106
and the center of the drive wheel
105
slightly varies such that the distance N between the center of the drive wheel
105
and the center of the rearmost guide wheel
107
decreases. As the distances M and N vary in such a manner, tension of a crawler belt
108
also varies. When the tension of the crawler belt
108
exceeds an excessive level, the crawler belt
108
encounters a breakdown. In contrast, when the tension of the crawler belt
108
is too small, the crawler belt
108
is apt to be dislocated from the drive wheel
105
or the driven wheel
106
.
Now, discussion will be made as to an operation of the snow-removing machine when it accidentally runs on hard snow during snow-removing operation with reference to
FIGS. 7A
to
7
C.
In
FIG. 7A
, the crawler belt
108
is held in close contact with road surface
100
, with the body frame
103
and an auger
104
located at the front portion of the crawler vehicle being held at a given height from the road surface
100
by the action of a pivot shaft
102
mounted at a rear portion of a crawler frame
109
located inside the crawler belt
108
and the jack
101
located forwardly of the pivot shaft
102
. Reference numeral
110
designates a sleigh which serves as a member for suitably maintaining the auger
104
at the given height from the road surface
100
or as a member for reducing weight and load of the auger
104
to be applied to the body frame
103
. A pentagon is formed by connecting the sleigh
110
, the auger drive shaft
112
, the pivot shaft
102
, the center of the guide wheel
107
, and the sleigh
110
(hereinafter referred to as a “pentagon X”).
It has been proposed to provide a snow-removing practice wherein, when an object to be removed is new snow, the auger
104
is intentionally lowered with a view to remove an increased amount of snow. In such a practice, the jack
101
is retracted to allow of the body frame
103
to rotate counterclockwise about the pivot shaft
102
, thereby lowering the auger
104
.
However, when the snow-removing machine accidentally comes across hard snow with the jack
101
held in the retracted state, the snow-removing machine encounters the following problems. In this event, the sleigh
110
runs on hard snow, causing the crawler belt
108
to be lifted up from the road surface
100
in the vicinity of the driven wheel
106
. That is, the crawler belt
108
is caused to rotate clockwise as a whole at an angle &thgr;
1
about the pivot shaft
102
. In parallel with such a movement, the pentagon X shown in
FIG. 7A
varies in a manner as described below.
The center
107
a of the guide wheel
107
is caused to swing clockwise at the angle &thgr;
1
about the pivot shaft
102
. Since, in this instance, the center
107
a
remains at a fixed height from the road surface
100
, the pivot shaft
102
is lowered. Since, in this event, the sleight
110
and the body frame
103
form a common rigid structure to which the auger shaft
112
and the pivot shaft
102
are interconnected, the line segment connected between the sleigh
110
and the auger shaft
112
and the line segment connected between the auger shaft
112
and the pivot shaft
102
intersects at an angle &agr; which remains unchanged at a constant value.
When the pivot shaft
102
is lowered with the angle &agr; held constant, the auger shaft
112
is apt to swing clockwise about the sleigh
110
, causing the auger shaft
112
to rise. Pentagon formed during such a movement is referred to as the pentagon Y.
FIG. 7C
shows the pentagons X and Y in an overlapped state. When the center
107
a
is caused to swing clockwise at the angle &thgr;
1
about the pivot shaft (provided that, since the level of the center
107
a
remains unchanged, the pivot shaft
102
swings clockwise about the center
107
a
by appearance), the pivot shaft
102
is lowered by the distance &Dgr;
1
and, in link motion therewith, the auger shaft
112
swings clockwise at the angle &thgr;
2
about the sleigh
110
, thereby lifting up the auger shaft
112
by the distance &Dgr;
2
.
Thus, when the auger shaft
112
is raised and the pivot shaft
102
is lowered, the auger
104
shown in
FIG. 7B
is tilted upward more than that shown in
FIG. 7A
, thereby deteriorating biting effect of the snow.
As discussed above, in the conventional snow-removing machine, if the auger is lowered when the snow-removing machine removes snow deeply, the auger is apt to be tilted upward with a resultant decrease in performance efficiency of the snow-removing operation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a crawler vehicle which has an improved performance efficiency in snow-removing operation and is able to minimize the variation in tension of a crawler belt.
According to an aspect of the present invention, there is provided a crawler vehicle comprising a crawler frame having a front portion carrying a driven wheel and a lower portion carrying at least one lower idle wheel, a body frame connected vertically swingably to a rear portion of the crawler frame, a working member mounted to a front portion of the body frame, an engine mounted to the body frame, a drive wheel mounted to a rear portion of the body frame, and a crawler belt trained around the drive wheel and the driven wheel, characterized by a pivot shaft positioned forwardly of the lower idle wheel for allowing the vertical swinging movement of the body frame.
When the front portion of the crawler belt is lifted up from the road surface, the center of the lower idle wheel is apt to swing about the pivot shaft. Since, in this event, the pivot shaft is located forwardly of the lower idle wheel, the swing movement of the lower idle wheel causes the pivot shaft to be lifted. Due to this lifting movement of the pivot shaft, the auger shaft swings about the sleigh and is lowered. Consequently, it is possible for the auger to be lowered regardless of soft snow or hard snow, thereby carrying out snow-removing operation in

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