Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
2000-06-02
2001-12-04
Green, Mary Ann (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
C474S206000
Reexamination Certificate
active
06325735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a silent chain which is constructed to reduce noises generated when meshing with a sprocket and to improve the lifetime of the chain.
2. Description of the Related Art
Silent chains are used extensively for a variety of purposes, such as power transmission between an engine crank-shaft and a camshaft in an automotive vehicle. These silent chains include a plurality of rows of link plates serially interconnected or articulated with each other, and each of the link plates is in a virtually bifurcated or V shape to provide, at its opposite ends, a pair of meshing teeth which are directly meshable with successive teeth of a sprocket wheel. More specifically, outside or inside flanks of these teeth are sequentially brought into a power-transmitting contact with the sprocket teeth.
FIG. 5
shows one example of the conventional silent chains which is disclosed in Japanese Patent Publication No. HEI-1-56304. The disclosed silent chain
50
, for the purpose of reducing an impact and noises during power-transmitting meshing operation thereof, includes an inside flank
52
of arcuate convex profile and an outside flank
54
of straight profile which jointly form each tooth
56
of one link plate. When the silent chain
50
is in a straight-line state, the arcuately convex inside flank
52
of one link plate projects outwardly from the straight outside flank
54
of the preceding link plate.
FIG. 5
also illustrates an operational sequence in which the link plates of the silent chain
50
sequentially mesh with teeth of a sprocket S. At the onset of meshing engagement between the link plates of the silent chain
50
and the teeth of the sprocket S, the arcuate convex inside flanks
52
of the link plate are caused to interfere with and then slide along the sprocket teeth, as achieved at the position of a tooth T
1
of the sprocket S. When the link plates of the silent chain
50
are placed in full meshing engagement with the sprocket teeth, the straight outer flanks
54
of the link plates are completely seated on the sprocket teeth, as achieved at the position of another tooth T
2
of the sprocket S. By the meshing engagement between the outside flanks
54
of the link plates and sprocket teeth thus acheived, the silent chain achieves its power-transmitting operation between, for example, a crankshaft and a camshaft in an engine.
In the case of the link plates having the combination of an arcuate convex inside flank
52
and a straight outside flank
54
, a problem arises in that the projecting length of the arcuately convex inside flank
52
becomes excessively large at a central portion of the inside flank
52
, thereby hindering smooth intermeshing engagement between the silent chain
50
and the sprocket S. If the projecting length at the central portion of the arcuate convex inside flank
52
is made small, a sufficient noise-suppressing effect cannot be attained partly due to insufficient interference between the inside flank
52
and the sprocket tooth occurring in the vicinity of a tip of each tooth of the link plate, and partly due to a delay in timing of the meshing operation.
In addition, due to the excessive projectina length at the central portion of the arcuately convex inside flank
52
, wear of the inside flanks
52
and the sprocket tooth occurs in a relatively short time, making it difficult to maintain the prescribed noise-suppressing effect of the silent chain.
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 silent chain which can minimize undesired meshing sounds or noise produced by meshing engagement between the silent chain and a sprocket.
Another object of the present invention is to provide a silent chain which can minimize wear of the silent chain and a sprocket occurring due to meshing engagement between the silent chain and the sprocket, thereby maintaining the prescribed noise suppressing effect over a long period of use.
A further object of the present invention is to provide a silent chain which can effectively prevent the unwanted resonance of the meshing sounds and thereby minimize the noise level.
In order to accomplish the above-mentioned object, the present invention provides a silent chain for use with a toothed sprocket, which includes guide links and articular links alternately arranged in the longitudinal direction of the chain. Each of the guide links has a pair of guide plates and at least one guide link plate disposed laterally between the guide plates. The guide plates each have a pair of pin holes spaced in the longitudinal direction of the chain, and the guide link plate has a pair of pin holes spaced in the longitudinal direction of the chain. Each of the articular links has at least two laterally aligned articular link plates each having a pair of pin holes spaced in the longitudinal direction of the chain. Each of the guide links and an adjacent one of the articular links are articulately connected together by a pivot pin inserted through one of the pair of pin holes in each of the guide plates, one of the pair of pin holes in the guide link plate and one of the pair of pin holes in each of the articular link plates. The guide link plate has a pair of teeth designed to engage the sprocket, each of the teeth being defined by an inside flank having a straight profile and an outside flank having a straight profile. The articular link plates each have a pair of teeth designed to engage the sprocket, each of the teeth being defined by an inside flank having a straight profile and an outside flank having a straight profile.
When the silent chain is in a straight-line state, the inside flank of the guide link plate of any one of the guide links projects outwardly from the outside flank of each of the articular link plates of a preceding one of the articular links, and the inside flank of each of the articular link plates of any one of the articular links projects outwardly from the outside flank of the guide link plate of a preceding one of the guide links.
When the silent chain is wrapping itself around the sprocket with the adjacent guide and articular links being in a flexed state, the inside flank of the guide link plate of any one of the guide links retracts inwardly from the outside flank of each of the articular link plates of a preceding one of the articular links, and the inside flank of each of the articular link plates of any one of the articular links retracts inwardly from the outside flank of the outside flank of the guide link plates of a preceding one of the guide links.
The outside flank of the guide link plate and the outside flank of each articular link plate have the same shape and configuration. One of the guide link plate and each articular link plate is comprised of at least two types of link plates arranged in the longitudinal direction of the chain and each having a different inside flank designed such that when the chain is in the straight-line state, the inside flank of a first link plate of the at least two types of link plates has a first projecting length with respect to the outside flank of the other of the guide link plate and each the articular link plate of the preceding link, and the inside flank of a second link plate of the at least two types of link plates has a second projecting length with respect to the outside flank of sand other link plate of the preceding link, the first and second projecting lengths being different from each other.
In one preferred form, the other link plate is comprised of a single type of link plate and identical in shape and configuration with one of the first and second link plates.
The first and second projecting lengths of the respective inside flanks of the first and second link plates may be uniform throughout the length of the inside flanks or may vary by either increasing, or alternatively decreasing, gradually toward a tip of the associated tooth.
In response to rotation of the sprocket, a silent chain
Fukuda Shigekazu
Funamoto Takayuki
Horie Hiroshi
Kanehira Makoto
Kusunoki Yoshihiro
Green Mary Ann
Howson & Howson
Tsubakimoto Chain Co.
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