Motor vehicles – Special driving device – Portable track
Reexamination Certificate
2000-06-08
2002-04-30
Swann, J. J. (Department: 3611)
Motor vehicles
Special driving device
Portable track
C305S134000
Reexamination Certificate
active
06378635
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a track frame connecting structure of a heavy work vehicle.
2. Description of the Prior Art
Conventionally, as shown in
FIG. 5
, a body of a tractor that constitutes a heavy vehicle has a pivot shaft
31
secured thereto and track frames
4
are pivotally and tiltably mounted thereon. Crawlers
34
, which are guided by rollers
35
and idlers
36
, are provided on the track frames
4
. Sprockets
33
are fixedly secured to sprocket shafts
32
, which are disposed at a position different from the pivot shafts
31
. The sprockets
33
transmit power to the crawlers
34
. As shown in
FIG. 6
, an equalizer bar
3
has its center pivotally and tiltably mounted on the body
1
by means of a center pin
2
. The equalizer bar
3
has two ends pivotally connected to the track frames
4
by means of pins
37
.
Upon receiving an external force from a lateral direction, each track frame
4
has a distal end thereof (left side in the drawing) shifted toward the center of the body (toe-in) or toward the outside of the body (toe-out) around a point M in
FIG. 7
, which functions as its center. The equalizer bar
3
connects the left and right track frames
4
with the body
1
, so as to prevent the toe-in and toe-out which may be caused by this external force. Further, as shown in
FIG. 5
, when the tractor travels on uneven ground, the track frames
4
tilt up and down following the landform about the pivot axis
31
, thus reducing the fluctuation of the body
1
.
In the above-mentioned conventional suspension system, as shown in
FIG. 6
, a pin
37
, which connects the equalizer bar
3
and the track frame
4
, traces a circular arc having a radius R and its center at center pin
2
. When displaced by distance “x”, the pin
37
is shifted toward the inside from the initial position by the interval &dgr;1. When this condition is observed from the H direction shown in
FIG. 5
, the center line KaKa of the track frame
4
takes a position KbKb, which is displaced by &dgr;1 along the center line of the equalizer bar
3
around the center M of the pivot shaft
31
, as shown in FIG.
7
. In addition, the center of the crawler
34
deviates from the center of the sprocket
33
by &dgr;2 at a position where the crawler
34
is wound around the sprocket
33
.
That is, the toe-in gives rise to the distortion of the alignment. Accordingly, there have been problems that non-uniform abrasion occurs at side faces of teeth of the sprockets, side faces of the crawler links, flanges of rollers and bushings of the crawlers, so that the lifetime of these parts is shortened. In addition, an excessive load is applied to the track frame and the pivot shaft frequently, so that the lifetime of these parts is also shortened.
To solve such problems, in Japanese Utility Model Laid-Open Publication 132590/1990, the applicant proposed a suspension system of a crawler type tractor that can reduce the toe-in and the toe-out by providing a crankshaft
10
and a link
20
. In this arrangement, a crankshaft and a link shaft are provided where an equalizer bar
3
and a track frame
4
are connected.
This suspension system of the crawler type tractor is shown in FIG.
8
and FIG.
9
.
FIG. 9
is a cross-sectional view of
FIG. 8
taken along a line I—I. In these figures, the equalizer bar
3
is tiltably and pivotally mounted on the body
1
by means of a center pin
2
. A pin journal
7
is fitted in a spherical bearing
9
, which is mounted in an end portion of the equalizer bar
3
. A crankshaft
10
has main journals
8
pivotally mounted in bearings
5
, which are welded to the track frame
4
. Levers
11
are integrally formed on both ends of the crankshaft
10
. End portions of the levers
11
and brackets
22
, which are fixedly secured to the frame
1
, are connected by way of link pins
21
and links
20
. The link pins
21
and links
20
are fixedly secured to each other. The link pins
21
and levers
11
are rotatably connected with each other, and the link pins
21
and the brackets
22
are also rotatably connected with each other.
The manner of operation of the above suspension system will now be explained. As shown in
FIG. 10
, the crank shaft
10
is pivotally mounted in the portion of equalizer bar
3
. With the lifting of an axis Q of the bearing
5
that is brought about by the lifting of the track frame
4
, an axis P of the pin journal
7
of the crank shaft
10
moves on a circular arc BB which has its center at the center pin
2
. A center S of the link pins
21
, which are provided at the end portions of the levers
11
, moves on a circular arc CC. The levers
11
are pivotally mounted on the brackets
22
of the body
1
. Accordingly, the position of the motion of the axis Q is restricted, and the motion approximates a straight line AA so that the amount of the toe-in takes the least value. Although not shown in the drawings, the similar effect is obtained in lowering the track frame
4
. Accordingly, even when the track frame
4
is jolted at the time that the tractor travels on an uneven ground, an amount of toe-in caused by the equalizer bar
3
can be minimized.
However, the above-mentioned suspension system of the crawler type tractor has the following problems.
As shown in FIG.
8
and
FIG. 9
, the pin journals
7
provided at the end portions of the equalizer bar
3
are disposed at the outside of body
1
in the left and right directions, while the main journals
8
, which are pivotally mounted on bearings
5
welded to the track frame
4
, are disposed close to the center of the body
1
in the left and right directions. That is, the pin journals
7
and the main journals
8
are arranged in the left and right directions of the body. Compared to the main journals
8
, which are pivotally mounted on the bearing
5
welded to the track frame
4
, the pin journals
7
provided at the end portions of the equalizer bar
3
are disposed at positions further from the center pin
2
. Therefore, in order to assure a necessary amount of movement of the track frame
4
in the up and down directions, it becomes necessary to have an amount of movement of the end portions of the equalizer bar
3
in the up and down directions, which is equal to or greater than the amount of movement of the track frame
4
. Accordingly, it is necessary for there to be a space in the body
1
, which allows such a motion of the equalizer bar
3
. To this end, the center pin
2
, which mounts the equalizer bar
3
to the body
1
so that the body freely tilts and pivots, must be lowered and a bracket portion
1
b
of the body
1
, to which the center pin
2
is mounted, must be enlarged in the downward direction. The result is that the weight of the vehicle is increased and waste materials are increased, thus increasing the cost.
Further, as mentioned previously, if the track frame
4
is lifted, the axis Q of the bearing
5
has its range of motion thereof restricted and the motion substantially approximates the straight line AA. However, as mentioned previously, because the pin journals
7
are fitted in the end portions of the equalizer bar
3
, the main journals
8
are pivotally mounted on the bearings
5
welded to the track frame
4
at positions toward the center of the body
1
, and the axis P of the pin journal
7
. Also, the axis Q of the bearing
5
and the center S of link pins
21
are arranged in the horizontal direction as shown in FIG.
8
. Thus, the range of motion for the axis Q of the bearings
5
is a straight-line motion and narrow, and the range is insufficient to provide the straight-line motion in a manner necessary for a heavy work vehicle like a tractor.
SUMMARY OF THE INVENTION
The present invention was made to solve the above-mentioned problems. It is an object of the present invention to provide a track frame connecting structure of a working vehicle that can minimize the up and down movement of end portions of an equalizer bar, so that the range of the straight-line motion of the track frames is, for practi
Ozaki Taira
Yoshida Tsuyoshi
Divine David
Komatsu Ltd.
Swann J. J.
Varndell & Varndell PLLC
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