Wheel substitutes for land vehicles – Endless belt having nonmetallic track or tread – Track formed of endless flexible belt
Reexamination Certificate
2002-02-28
2003-07-08
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
Endless belt having nonmetallic track or tread
Track formed of endless flexible belt
C305S172000, C305S173000, C305S177000
Reexamination Certificate
active
06588862
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
not applicable
BACKGROUND
(1) Field of the invention
The present invention relates generally to a rubber crawler.
(2) Description of related art
From EP-A-0.118.912 a rubber crawler is known comprising an endless rubber belt driven around a toothed sprocket wheel and intermediate wheel. In the interior of the rubber crawler, distributed over the internal circumference of the belt, between the sprocket wheel and intermediate wheel, supporting rolls are provided for supporting the rubber belt. In longitudinal direction of the belt, at a regular distance from each other and parallel to each other, a plurality of metal core elements are embedded to drive the rubber crawler around the sprocket wheel and the intermediate wheel. Each metal link contains a basis with a center, the basis extending in transverse direction of the rubber belt, the center of the basis comprising a guiding. On both sides of the guiding a protrusion which protrudes towards the inner surface of the rubber belt, is provided in such a way that protrusions of successive metal links form the running surface for the supporting rolls. In order to render the running surface as continuous as possible, the protrusions are elongated in longitudinal direction of the crawler and extend in longitudinal direction of the rubber belt with respect to the metal link. The space between the basis of the metal link and the bottom side of the protrusion is at least partly filled with rubber.
The rubber crawler disclosed in EP-A-118.912 however presents the disadvantage that its stiffness in the bending direction of the crawler is too large, which leads to the formation of cracks and causes fatigue fractures in the rubber belt especially in the rubber phase located between the metal links, during use of the rubber crawler.
SUMMARY
The inventions, according to one aspect, provide a rubber crawler with which the formation of the above described cracks and fatigue fractures can be decreased.
This is achieved according to the claimed inventions which provide, in accordance with one aspect thereof, a rubber crawler arrangement in which first and second protrusions respectively show, on opposite sides of the metal link and in transverse direction of the rubber crawler, a first and second front surface which extend from the basis of the metal link in upward direction thereof. Both the first and second front surface slant—taken in longitudinal direction of the crawler—in opposite directions with respect to the basis. The slope of the first and second front surface with respect to the basis is smaller than 90°, so that the metal links can be embedded in the rubber crawler in such a way that the space between the front surface of the protrusions and the inner surface of the rubber belt remains almost free of rubber.
The top surfaces of the first and second protrusions have, taken in longitudinal direction of the crawler, a length W
t
which is smaller than the width of the basis W
b
, taken in longitudinal direction of the crawler, so that the protrusions do not extend with respect to the metal link. Because of the limited length of the protrusions and the absence of a bond between the protrusion, in particular the front surface thereof and the rubber belt, a larger free space remains between the protrusions of successive metal links. In that way on the one hand a reduction of the minimum possible bending radius of the rubber crawler can be obtained, while simultaneously the bendability and flexibility of the rubber belt in the moving direction of the crawler can be improved. Simultaneously, evacuation of stones and sand which may end up between the successive links during use of the rubber crawler can be improved. Also, because of the absence of a bond between the front surface of the protrusion and the rubber belt, stresses on the rubber of the belt caused by the tilting of the links within the belt, which lead to the formation of cracks and fatigue fractures, can be reduced.
The slopes &agr; and &bgr; of the front surfaces of the first and second protrusions with respect to the basis are geared to the length of the running surface of the first and second protrusions W
t
in such a way that the top surfaces of the first and second protrusions within one and the same metal link show an overlap O
1
in transverse direction of the crawler which is >0, and the top surfaces of the first and second protrusions of successive metal links show an overlap O
2
in transverse direction of the rubber crawler which is also >0. Herewith O
1
and O
2
and the length W
t
of the top surfaces of the first and second protrusions, taken in longitudinal direction of the crawler, are chosen such that
O
1
+O
2
=2
W
t
−P
in which P is the distance between the centers of two successive metal links.
By gearing the angles &agr; and &bgr; to the length W
t
of the top surfaces of the first and second protrusions, it is possible to limit W
t
in such a way that the protrusions taken in longitudinal direction of the rubber crawler do not extend with respect to the metal link, while maintaining an overlap between the protrusions within one link and between successive links and thus maintaining continuity of the running surface of the supporting rolls. Consequently, W
t
is smaller than the width of the basis W
b
, taken in longitudinal direction of the crawler. Because the length of the top surfaces of the protrusions is limited, it is possible to positively influence the bendability and the life time of the rubber crawler. By the particular mounting of the protrusions and improved continuity, the running surface of the supporting rolls can be optimized and vibrations caused by the movement of the supporting rolls over the running surface of the metal links can be kept under control.
The inventions described and claimed herein provide a rubber crawler with an improved flexibility in the moving direction of the crawler, in which the risk to the occurrence of cracks or fatigue fractures in the rubber can be reduced. At the same time an improved evacuation of materials which may end up between the links during use of the rubber crawler is made possible. Due to the improved continuity of the running surface of the supporting rolls, vibrations caused by a discontinuous contact of the supporting rolls with the successive metal links can be diminished correspondingly. Thus, with this invention a simultaneous improvement of the flexibility of the crawler and the evacuation of outside materials from the crawler can be obtained, as well as an optimization of the continuity of the running surface of the supporting rolls.
O
1
is preferably substantially equal to O
2
to obtain a running surface for the supporting rolls with an optimal continuity.
Preferably also the length of the running surfaces of the first and second protrusions W
t
is larger than or equal to W
s
, W
s
being the width of the sprocket of the metal part, in order to provide a sufficient overlap between protrusions of successive metal links even in the case of a rubber crawler with a narrow sprocket.
To allow the stabilization of the metal link in the rubber belt to be improved, without sacrificing the bendability and flexibility of the rubber crawler, the first and second wings preferably have a substantially constant width over their entire length (W
W2
below and W
W1
on top), measured in the longitudinal direction of the rubber crawler.
To simplify the production process of the metal links and the rubber crawler the angle a between the front surface of the first protrusion and the basis is preferably substantially equal to the angle &bgr; between the front surface of the second protrusion and the basis, and the length W
t
of the first protrusion is equal to the length W
t
of the second protrusion.
Preferably the first and second protrusions have, on a position where they pass into the basis, taken in longitudinal direction of the crawler, a width W
b
, which is su
Morano S. Joseph
Nguyen Lung B
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