Wheel substitutes for land vehicles – Endless belt having nonmetallic track or tread – Track formed of endless flexible belt
Reexamination Certificate
1998-10-29
2001-01-09
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
Endless belt having nonmetallic track or tread
Track formed of endless flexible belt
C305S171000
Reexamination Certificate
active
06170925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel rubber crawler, and more particularly to a rubber crawler having a structure for preventing the occurrence of crack or breakage in each of the widthwise edge portions of rubber in the crawler.
2. Description of Related Art
There are well-known and widely used two types of rubber crawlers having structures shown in FIG.
1
and FIG.
2
. The first type rubber crawler shown in
FIG. 1
comprises an endless rubber belt
1
, a plurality of core metal pieces
2
arranged and buried at predetermined intervals in the longitudinal direction of the belt
1
, and steel cords
3
arranged to cover the outer surface of the metal pieces
2
and buried in the longitudinal direction of the belt
1
. Since a widthwise length of the metal piece
2
is shorter than a full width of the belt
1
, widthwise edge portions
4
made from only rubber are formed in both sides of the belt
1
. On the other hand, the second type rubber crawler shown in
FIG. 2
comprises rubber pads
5
fixed to links
6
, which being axially supported by pins
7
form an endless structure, through metal crawler blocks
8
and bolts and nuts
9
. In the latter case, a widthwise length of the rubber block
8
is shorter than a full width of the rubber pad
5
, so that widthwise edge portions made from only rubber are formed in both sides of the rubber pad
5
.
In general, the widthwise edge portion of the core metal piece has a vertically cut shape at its widthwise edge and front and back edges and is the most flexible portion of the rubber crawler, so that deformation strain is liable to be most caused in the widthwise edge portion at a use state of the rubber crawler. For example, when the rubber crawler contacts with or rides on protrusions such as pebbles, stone pieces, and the like scattered on a running road or a curb of a footpath as shown in
FIG. 3
, the widthwise edge portion
4
is sandwiched between the core metal piece
2
(or metal crawler block) and the curb
10
and shearing force strongly and repeatedly acts to the widthwise edge of the core metal piece during the running of the rubber crawler to thereby create crack C from the vicinity of such an edge toward an outer surface of the widthwise edge portion
4
. See
FIG. 3
a crack grows toward the side of contacting with ground and further toward the front and back sides of the widthwise edge portion due to repetition of deformation stress to finally cause breakage of the widthwise edge portion. As a result, the durability of rubber constituting the widthwise edge portion and hence service life of the rubber crawler are undesirably degraded.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the afore-mentioned problem of the conventional rubber crawler and to provide a novel rubber crawler capable of reducing or preventing the occurrence of cracks or breakage in the widthwise edge portions of rubber due to the contacting with or riding on the protrusion scattered on road or the curb of the footpath.
According to the invention, there is the provision of a rubber crawler comprising a rubber elastomer constituting a main body of the crawler, at least one metal core buried in the rubber elastomer and extending in a widthwise direction perpendicular to a running direction of the crawler, and at least one rubber lug formed on an outer peripheral face of the rubber elastomer, wherein each widthwise end portion of the metal core and front and back edge portions near to the widthwise end thereof in the running direction are inclined at a ground contacting side toward an inner peripheral side of the crawler to form a bow-shaped section in each of both widthwise ends of the metal core.
In a preferable embodiment of the invention, the rubber elastomer is an endless rubber belt or a rubber pad.
In another preferable embodiment of the invention, an inclination angle of the bow-shaped section with respect to an outer horizontal peripheral face of the metal core is 15-45°, preferably 20-35°. Particularly, an inclination angle of the widthwise end of the metal core in the bow-shaped section with respect to the outer horizontal face thereof is 15-45° and an inclination angle of each of the front and back edges of the metal core in the bow-shaped section is approximately 90°.
In the other preferable embodiment of the invention, a length of the rubber lug in the widthwise direction at the ground contacting face is longer than a distance between the bow-shaped sections at both widthwise ends of the metal core.
In a further preferable embodiment of the invention, a rubber protruding portion covering each of the bow-shaped sections of the metal core is formed on an inner peripheral side of the crawler.
In a still further preferable embodiment of the invention, the bow-shaped section is provided with an outside-inside path. In another preferable embodiment of the invention, when the rubber elastomer is an endless rubber belt, a row of plural steel cords arranged side by side is buried in the rubber elastomer along an outer surface of the metal core to extend these steel cords in the circumferential direction of the rubber elastomer and each of outermost steel cords in the steel cord row is located inward from the widthwise end of the metal core by not less than 15 mm.
In the other preferable embodiment of the invention, an edge of a plane surface in a widthwise end portion of the rubber elastomer facing to ground is located outward from an outer surface of the metal core.
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Bridgestone Corporation
Morano S. Joseph
Nguyen Long Bao
Sughrue Mion Zinn Macpeak & Seas, PLLC
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