Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
2000-08-02
2002-12-17
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
Reexamination Certificate
active
06494800
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a so-called “rocker joint type” silent chain which is particularly suitable for use, as an automobile silent chain, in a drive unit for an engine cam shaft, an engine auxiliary device, a transmission, a transfer box and so on of an automobile.
2. Description of the Related Art
As shown in
FIGS. 4 and 5
, a conventional rocker joint type silent chain A
1
includes a large number of link plates A
4
articulately connected together in an endless fashion by means of rocker joints each composed of a long pin A
2
and a short pin A
3
which is smaller in length than the long pin A
2
. The link plates A
4
each have an inverted tooth-like engagement surface T designed for direct meshing engagement with teeth of a sprocket A
5
so that power is transmitted between the sprocket and another sprocket (not shown).
The link plates A
4
are arranged in many rows in the transverse direction of the silent chain A
1
in such a manner that the plates A
4
, which are adjacent to each other back and forth in the traveling direction of the silent chain A
1
, are sandwiched alternately in the transverse direction.
As shown in
FIG. 6
, opposite ends of the long pin A
2
are press fit in non-circular pin holes A
9
, A
10
formed in two guide plates A
6
which are arranged adjacent both outsides of plural, transversely arranged link plates A
4
and are guided by side surfaces of the teeth of the sprocket A
5
.
The long pin A
2
and the short pin A
3
, as shown in
FIG. 6
, have substantially the same cross-sectional shape and are inserted into each of a pair of pin holes A
7
and A
8
in each link plate A
4
so as to be opposed to each other such that convexly arcuate rocker surfaces R of the long and short pins A
2
, A
3
, respectively, are adjacent to each other.
The long pin A
2
, inserted in each pin hole A
7
, A
8
and located closer to an outer end of the link plate A
4
than a center of the link plate A
4
, has a load-bearing surface C
1
composed of a concavely arcuate portion formed on the side opposite to the rocker surface R and a pair of convexly arcuate portions extending contiguously from both circumferential ends of the concavely arcuate portion. The load-bearing surface C
1
comes into engagement with a pin-seating surface S
1
of each pin hole A
7
, A
8
and is thereby prevented from rotating. The pin-seating surface S
1
is composed of a convexly arcuate portion and a pair of concavely arcuate portions extending continuously from both circumferential ends of the convexly arcuate portion.
The short pin A
3
, inserted in each pin hole A
7
, A
8
and located closer to the center of the link plate A
4
than the outer end of the link plate A
4
, is engaged at a load-bearing surface C
1
thereof with pin-seating surface S
1
of a pin hole A
9
, A
7
formed in a longitudinally adjacent link plate (not shown) and is thereby prevented from rotating.
FIG. 8
is an enlarged view of a portion of
FIG. 7
, showing the manner in which the rocker surface R and the load-bearing surface C
1
are connected with each other. As shown in
FIG. 8
, the rocker surface R and the load-bearing surface C
1
of each pin (long pin A
2
being shown) are connected together by a pair of convexly arcuate connecting surfaces C
2
having an extremely small radius of curvature, such as about one-twentieth of a chain pitch, such that each of the convexly arcuate connecting surfaces C
2
produces no substantial gap or clearance between itself and the peripheral surface of each pin hole A
7
, A
8
.
When the silent chain A
1
is entrained around on the sprocket A
5
, as shown in
FIG. 4
, and a tensile force is exerted between front and rear link plates A
4
, the rocker surfaces R, R of the long and short pins A
2
and A
3
are pressed against each other to effect transfer of the tensile force.
In this instance, the silent chain A
1
is under oiled or lubricated condition so that a lubricating oil is supplied to the silent chain A
1
from the outside thereof. Since the opposite rocker surfaces R, R are each formed in a convexly arcuate surface, it becomes possible to perform a relative rocking motion between the long and short pins A
2
and A
3
, thus permitting bending between longitudinally adjacent link plates A
4
.
In the conventional silent chain A
1
constructed as described above, the convexly arcuate pin-seating surface S
1
of each pin hole A
7
, A
8
of the link plate A
4
and the concavely arcuate load-bearing surface C
1
of the long pin A
2
which is closer to the outside of the link plate A
4
are brought into engagement with each other to effect transfer of the tensile force or load while preventing rotation of the long and short pins A
2
and A
3
relative to the link plate A
4
.
However, the rocker surface R and the load-bearing surface C
1
of each pin A
2
, A
3
are connected together via the edge-like convexly arcuate connecting surfaces C
2
having an extremely small radius of curvature not producing a substantial clearance between themselves and the inner peripheral surface of the corresponding pin hole A
7
, A
8
. As a result, it is difficult for the lubricating oil supplied from the outside of the silent chain A
1
to enter between the load-bearing surfaces C
1
, C
1
of the pins A
2
, A
3
and the inner peripheral surface of each pin hole A
7
, A
8
. Accordingly, if the pins A
2
, A
3
and pin holes A
7
, A
8
have different manufacturing accuracies, abnormal wear such as local wear is likely to occur due to insufficient lubrication. This abnormal wear has a great influence on the reduction of wear of the silent chain as a whole.
In addition, when the long pins A
2
are press fit into the non-circular pin holes A
9
, A
10
of the link plates A
4
to assemble a silent chain, the convexly arcuate connecting surfaces C
2
of each long pin A
2
are susceptible to stress concentration. When a tensile load is exerted between adjacent link plates A
4
during use of the silent chain A
1
, the silent chain A
1
as a whole is likely to cause fatigue failure due to stress concentrated on the convexly arcuate connecting surfaces C
2
. The fatigue failure becomes remarkable as the degree of interference between the long pins A
2
, A
3
and the pin holes A
9
, A
10
during press-fitting operation is enlarged to increase the joint strength between the guide plates A
6
and the long pins A
2
.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art in view, it is an object of the present invention to provide a wear-resistant silent chain which is capable of permitting entry of a sufficient amount of lubricating oil between load-bearing surfaces of two rocker joint pins seated on an inner peripheral surface of each of a pair of pin hole in each link plate, thereby eliminating local wear which would otherwise occur between the rocker joint pins and the inner peripheral surface of each pin hole.
Another object of the present invention is to provide a wear-resistant silent chain which is capable of improving the fatigue strength of the chain by eliminating stress concentration which may occur at connecting portions between a load-bearing surface and a rocker surface of each rocker pin when a longer one of the rocker pins is press fit at each end into a pin hole in each guide plate and when the silent chain is loaded during power transmitting operation.
To achieve the foregoing objects, there is provided according to the present invention a wear-resistant silent chain including a multitude of link plates articulately connected together by a plurality of rocker joint pins, wherein each of the link plates has a pair of pin holes formed therethrough in symmetrical relationship with respect to a center of the link plate, and each of the rocker joint pins is composed of a long pin and a short pin which is smaller in length than the long pin, the long and short pins being inserted into each of the pair of pin holes in each link plate so as to be opposed to each other in such a manner that the long pin is closer to an out
Fukuda Shigekazu
Funamoto Takayuki
Horie Hiroshi
Kanehira Makoto
Kusunoki Yoshihiro
Bucci David A.
Howson & Howson
McAnulty Timothy
Tsubakimoto Chain Co.
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