Wheel substitutes for land vehicles – Tracks or treads – With guide means for interfitting with sprocket wheel or roller
Reexamination Certificate
2002-12-20
2004-05-11
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
Tracks or treads
With guide means for interfitting with sprocket wheel or roller
C305S197000, C305S199000
Reexamination Certificate
active
06733092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a travel driving apparatus in a track-type earthmoving machine such as a bulldozer, a hydraulic excavator and the like, and more specifically to a travel driving apparatus for a track-type vehicle provided with a structure for enhancing durability of a track chain which is connected by links and a sprocket which drives the track chain.
2. Description of the Related Art
Conventionally, a traveling apparatus in a track-type earthmoving machine is structured such that a track chain formed in an endless shape is wound around a sprocket and an idler which are assembled in driving apparatuses disposed in front and rear sides of a vehicle body at a required distance so as to perform traveling. Further, the track chain has a lot of track links which are arranged in right and left sides at a predetermined interval, bushings which are provided between the right and left track links, and a plurality of connection pins which are inserted into the respective bushings and which connect the adjacent track links to each other. Track shoes are fastened to outer peripheral surfaces of the right and left track links, which are connected in a circular shape, by bolts, whereby the track chain is formed in an endless shape.
The traveling apparatus provided with the track chain having the above-described configuration is driven by a sequential engagement between the sprocket and the bushings in the track chain at a time of traveling. At a time of the engagement, the bushing in the track chain is engaged with a tooth bottom of the sprocket in a contact state, whereby a power is transmitted. However, when the track chain engaged with and driven by the sprocket moves to a grounded side, the track shoe is in contact with the ground surface and supports the vehicle body. Accordingly, an up-throwing force is applied to the sprocket via the bushings in the track shoe engaged with the teeth of the sprocket in the grounded side.
In the manner described above, not only a surface pressure with respect to the bushing caused by a rotational driving force, but also an up-throwing load generated for supporting the vehicle body and a load caused by a slip between an initial position at which the bushing is sequentially engaged and a position at a time of moving apart from the tooth portion are greatly applied to the tooth portion of the sprocket. Further, earth and sand which are flung up at a time of traveling on rough ground intrude into the engagement portion between the tooth portion of the sprocket and the bushing in the track chain. When the traveling operation is continuously performed, moreover, friction with the earth and sand becomes significant, and the bushings and the teeth of the sprocket are considerably worn. Further, vibration in the vehicle body is generated at a time of traveling. Particularly, in the track-type vehicle such as a bulldozer which performs an operation while intensely moving in a repeated manner for a long time, vibration is frequently generated, and considerable abrasion of the sprocket is generated. Accordingly, it is unavoidable to frequently replace specific parts of the sprocket and the track chain.
On the basis of the above-described condition, in order to reduce the wear and tear of the tooth portion in the sprocket of the travel driving apparatus, some proposals have been made. As one of them, there is an idea of driving without engaging the bushing in the track chain with the tooth bottom of the sprocket. In accordance with this idea, even when earth and sand intrude into the engagement portion at a time when the sprocket and the bushing are engaged with each other, it is possible to prevent friction caused by earth and sand between the sprocket and the bushing from being generated, due to a gap generated in the tooth bottom. Accordingly, it is possible to reduce abrasion and it is simultaneously possible to reduce vibration.
FIG. 3
is a sectional view partially showing a front face of a sprocket portion in a traveling apparatus for a track-type vehicle which is disclosed in Japanese Unexamined Patent Publication No. 10-45056. As shown in
FIG. 3
, a sprocket
30
is fastened and attached to an outer peripheral portion of a housing
41
in a reduction gear
40
by a bolt
42
. When a track chain
20
is wound around the sprocket
30
, a surface
32
in a track chain inner peripheral side of a link
21
of the track chain
20
is brought into contact with an outer peripheral surface
43
of a housing
41
, and a gap F is provided between a tooth bottom portion
31
of the sprocket
30
and an outer peripheral surface of a bushing in the track chain
20
.
Further, as another conventional art, there is a configuration in which an engagement portion between the sprocket and the track chain is changed with the intention of making it easy to replace a worn portion. For example, there is a configuration described in U.S. Pat. No. 6,220,378-B1.
FIG. 4
is a partly sectional view of a side face which shows such a structure. In
FIG. 4
, a plurality of engagement members
52
are detachably mounted with a uniform pitch to an outer peripheral portion of a hub
51
which is mounted to a reduction gear
40
, whereby a sprocket assembly
50
is constructed. A traction lug
62
is detachably mounted to a non-grounded surface of a crawler shoe
61
of a crawler belt
60
by a bolt
63
. Groove portions
64
and
64
provided in front and rear end portions of the traction lug
62
of the track chain
60
are engaged with the engagement members
52
of the sprocket assembly
50
so as to drive the track chain
60
, and are exposed to a radial load. That is, the engagement member
52
and the groove portion
64
of the traction lug
62
are simultaneously exposed to the driving force and the radial load. The engagement member
52
and the traction lug
62
which correspond to the abrasion members are freely attached to and detached from each other, and it is easy to replace them.
However, in the above-described conventional configurations, the following problems have arisen.
In the conventional art disclosed in Japanese Unexamined Patent Publication No. 10-45056, when the track chain
20
is wound around the sprocket
30
in
FIG. 3
, the surface
32
in the track chain inner peripheral side of the link
21
in the track chain
20
is brought into contact with the outer peripheral surface
43
of the housing
41
in the reduction gear
40
. Accordingly, the outer peripheral surface
43
of the housing
41
is worn. In the case of being worn, it is necessary to replace the housing
41
of the reduction gear
40
, so that a lot of time is required for replacing, and a cost of the replaced part is high. Further, since the surface
32
in the crawler belt inner peripheral side of the link
21
is considerably worn, the lifetime of the link is reduced. In addition, since it is generally very hard to perform the replacing operation of the track chain
20
including the link
21
, and since a high cost is required for replacing these parts, in practice the frequency of replacing the link
21
and/or the track chain
20
is set to be less than the frequency of replacing the sprocket
30
. However, since the frequency of replacing the link
21
becomes high for the above-described reason, a great economic loss is generated.
In the conventional art disclosed in U.S. Pat. No. 6,220,378, since the engagement member
52
and the traction lug
62
are simultaneously exposed to the driving force and the radial load, the lifetime of both becomes short, the frequency of replacement is increased, and it is necessary to frequently replace the engagement member
52
and the traction lug
62
which requires a high cost. Accordingly, there has arisen a problem that the maintenance cost is high.
The present invention has been made by taking the above-described problems into consideration, and an object of the present invention is to provide a travel driving apparatus for a track-type vehicle which can reduce abrasion in a spr
Yamamoto Teiji
Yoshida Tsuyoshi
Bellinger Jason H.
Frishauf Holtz Goodman & Chick P.C.
Komatsu Ltd.
Morano S. Joseph
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