Silent chain

Details Silent chain Silent chain

2000-03-03

2001-08-21

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Positive drive belt

Belt formed of rigid links

C474S215000

Reexamination Certificate

active

06277046

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a silent chain, and more particularly to such a silent chain which is constructed to diminish wear elongation of the chain.
2. Description of the Related Art
As shown in
FIGS. 3 and 4
, a conventional silent chain A
1
is composed of a large number of link plates A
4
which are articulately connected together in an endless fashion by means of plural sets of rocker pins A
2
, A
3
with each set being constituted by two rocker pins. Teeth of a sprocket A
5
come into direct meshing engagement with engaging surfaces T of the link plates A
4
to perform transmission of power between the sprocket A
5
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 link 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.
Of the two rocker pins A
2
, A
3
which constitute each set, one rocker pin A
2
is longer than the other rocker pin A
3
and has opposite ends fitted into non-circular pin holes formed in guide plates A
6
which are arranged adjacent both outsides of the plural, transversely arranged link plates A
4
and are guided by side faces of the teeth of the sprocket A
5
.
As shown in
FIG. 5
, the rocker pins A
2
, A
3
have the same cross-sectional shape and are inserted into each of the pin holes A
7
and A
8
through the link plates A
4
so as to be opposed to each other so that respective rocker surfaces R of the rocker pins A
2
, A
3
are adjacent to each other.
The rocker pins A
2
, inserted into the pin holes A
7
, A
8
of each link plate A
4
and located closer to the outer end of the link plate A
4
, each have a concavely arcuate load-bearing surface C
1
formed on the side opposite to the rocker surface R and a pair of convexly arcuate load-bearing surfaces C
2
formed on both sides of the load-bearing surface C
1
. The concavely arcuate load-bearing surface C
1
and the convexly arcuate load-bearing surfaces C
2
, C
2
come into engagement with a convexly arcuate pin-seating surface S
1
and a pair of concavely arcuate pin-seating surfaces S
2
, S
2
, respectively, of each pin hole A
7
, A
8
of the link plate A
4
so that the rocker pins A
2
are prevented from rotating.
The load-bearing surface C
1
and each of the load-bearing surfaces C
2
, C
2
are smoothly connected together by a convexly arcuate surface having a small radius of curvature r
1
(FIG.
5
A). The pin-seating surface S
1
and each of the pin-seating surfaces S
2
, S
2
are smoothly connected together by a concavely arcuate surface having a radius of curvature r
2
(
FIG. 5A
) which is slightly smaller than the radius of curvature r
1
. Due to the different radii of curvature r
1
and r
2
, the convexly arcuate surface and the concavely arcuate surface are spaced by a slight gap or clearance.
On the other hand, the rocker pins A
3
inserted into the pin holes A
7
, A
8
of each link plate A
4
and located closer to the center of the link plate A
4
, are each engaged at respective load-bearing surfaces C
1
and C
2
with pin-seating surfaces of a corresponding one pin hole formed in a longitudinally adjacent link plate (not shown).
As shown in
FIG. 3
, when the silent chain A
1
is entrained on the sprocket
5
and a tensile force is exerted between longitudinally adjacent link plates A
4
, the rocker surface R of the rocker pin A
2
and the rocker surface R of the rocker pin A
3
are pressed against each other to effect transfer of the tensile force.
Since the opposed rocker surfaces R and R are each formed in a convexly arcuate shape, it becomes possible to perform a relative rocking motion between the rocker pins A
2
and A
3
, thus permitting bending or articulating of the 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
and the two concavely arcuate pin-seating surfaces S
2
of each of the pin holes A
7
, A
8
and the concavely arcuate load-bearing surface C
1
and the convexly arcuate load-bearing surfaces C
2
of the associated rocker pins A
2
which are located closer to the outer ends of the link plate A
4
are simultaneously brought into engagement with each other to effect transmission of a tensile force while preventing rotation of the rocker pins A
2
, A
3
relative to the link plate A
4
.
Form the manufacturing point of view, however, it is vary difficult to finish the rocker pins A
2
, A
3
and the pin holes A
7
, A
8
with high accuracies to secure the afore-mentioned simultaneous engagement between the three surfaces S
1
, S
2
, S
2
of each pin hole A
7
, A
8
and the corresponding surfaces C
1
, C
2
, C
2
of the rocker pins A
2
. In practice, it may occur that due to uneven or local engagement, the rocker pins A
2
, A
3
become wobble within the pin holes A
7
, A
8
which is usually accompanied by local wear. Especially, when the wear is concentrated on the pin-seating surfaces S
1
of the pin holes A
7
, A
8
or on the load-bearing surfaces Cl of the rocker pins A
2
, the wear will progressively grow or increase in the longitudinal direction of the silent chain. This will often result in an increased wear elongation of the silent chain.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a silent chain which is capable of stably holding rocker pins within the pin holes in link plate against wobbling to thereby prevent the occurrence of local wear between the rocker pins and the link plates, thus diminishing wear elongation of the silent chain.
To attain the above object, there is provided, in accordance with the present invention, a silent chain which comprises: a multitude of link plates, each link plate having two pin holes formed therethrough in symmetrical relationship with respect to a center of the link plate; and first and second rocker pins being inserted into each of the two pin holes of each link plate in such a manner that convexly arcuate rocker surfaces of the first and second rocker pins are adjacent with each other to bendably interconnect the link plates. An outer peripheral surface of each of the first and second rocker pins is formed with the rocker surface, a first non-contact surface opposed to an inner peripheral surface of each pin hole on a side opposite to the rocker surface, a pair of load-bearing surfaces contiguous with both circumferential ends of the first non-contact surface, and two second non-contact surfaces interconnecting the pair of load-bearing surfaces and both circumferential ends of the rocker surface, respectively. The inner peripheral surface of each the pin hole has a portion formed in a pair of pin-seating surfaces being in register with the pair of load-bearing surfaces of each the rocker pin, respectively, to prevent rotation of the rocker pin within each the pin hole. When the load-bearing surfaces and the corresponding pin-seating surfaces are in register with each other, the first non-contact surface and each of the second non-contact surfaces define, jointly with the inner peripheral surface of the pin hole, two slight clearances spaced in a circumferential direction of the pin hole.
With the silent chain thus constructed, a tensile force exerted on the silent chain is transmitted between two longitudinally adjacent link plates through the first and second rocker pins disposed in opposite relation with their rocking surfaces held in abutment with each other. In this instance, the pair of load-bearing surfaces of each rocker pin, which are formed on opposite sides of the first non-contact surface, and the pair of pin-seating surfaces which are formed as a part of the inner peripheral surface of each pin hole are brought into intimate face-to-face contact with each other.
Since each rocker pin is supported by two circumferentially spaced inner peripheral surface portions (i.e., the pin-sea

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