Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
2000-12-18
2002-05-14
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
C474S212000, C474S214000
Reexamination Certificate
active
06387003
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a chain having a number of interleaved rows of link plates articulately connected together in an endless fashion by means of rocker joint pins, and more particularly to a chain having an improved rocker pin joint structure.
A chain having a number of interleaved rows of link plates articulately connected together in an endless fashion by means of rocker joint pins is used as a silent chain or a CVT (Continuously Variable Transmission) chain. The silent chain is used as a driving chain for an engine camshaft, or a power-transmitting chain for a transmission. The CVT chain is used as a power-transmitting chain for a CVT unit.
These chains essentially comprise a plurality of interleaved rows of link plates connected together in an endless fashion by rocker joints each composed of a pair of rocker joint pins of different lengths. The link plates each have a pair of pin holes. A longer pin and a shorter pin jointly forming one rocker joint are inserted through the respective pin holes in the link plate of one row and the respective pin holes in the link plate of an adjacent row so as to join the two adjacent link plate rows.
The pin holes of the conventional chain have a generally circular shape. The inner peripheral surface of the generally circular pin hole includes a chord-like seat surface located closer to an outer end of the link plate than to the center of the link plate. The longer pin and the shorter pin have the same cross-sectional shape and each include a convexly arcuate rolling surface. These pins are inserted through laterally aligned pin holes of the overlapping link plates in such a manner that the respective rolling surfaces of the longer and shorter pins are in confrontation with each other with the longer pin being seated on the seat surface of the pin hole in one link plate, and the shorter pin being seated on the seat surface of the pin hole in an adjacent link plate.
The chain of the foregoing construction, when used as a silent chain for an automobile, is required to have high wear resistance, great noise reduction and good lubricating properties in addition to easy assembly and producibility, and low cost.
In order to improve wear resistance, an attempt has been made to provide a large space for holding a lubricating oil between upper and lower portions of the outer peripheral surface of each pin and corresponding upper and lower portions of the inner peripheral surface of the pin hole. This prior attempt has not been satisfactory because the rocker joint pins are liable to displacement within the pin holes when they are designed to have a relatively small thickness for enabling adjustment of the chain pitch during assembly, or when they becomes thin due to progressive wear.
Once the rocker joint pins are displaced from the correct position within the pin holes, it becomes no longer possible for the respective rolling surfaces to contact with each other on a pitch line of the chain. Even though a large lubricating oil holding space is provided for improving wear resistance, wear has occurred with rocker joint pins and link plates due to interference between the displaced rocker joint pins and the inner peripheral surfaces of the pin holes.
In addition, since the respective rolling surfaces of the longer and shorter pins contact each other at an incorrect position, wear on the rolling surfaces is locally intensified, causing deterioration of the durability of the chain. The contact of the rolling surfaces at incorrect positions gives rise to the additional problem that the link plates are displaced or offset from the pitch line and hence unable to start meshing with a sprocket at a correct position. This will result in a remarkable increase in operation noise.
Japanese Utility Model Laid-open Publication No. 62-196950 and Japanese Patent No. 2924915 disclose a chain wherein a projection is provided at an upper portion or a lower portion of the inner peripheral surface of each pin hole so as to prevent displacement including rotation of rocker joint pins within the pin hole and also to prevent adjacent link plates from becoming bent into a V shape. By the projection thus provided, the rocker joint pins are held in position against displacement relative to the link plates.
However, the projection gives rise to another problem. The effective contact area between respective rolling surfaces of the longer and shorter pins is reduced by the projection, and the wear resistance of the chain deteriorates with a reduction of the effective contact area. In addition, since the projection partly surrounds the contour of each rocker joint pin, a space for holding a lubricating oil, defined between the opposed rolling surfaces, is reduced. This may accelerate wear of the rolling surfaces due to insufficient lubrication. Furthermore, due to the presence of the projection, placement of the rocker joint pins into the pin holes is not easy to achieve, thereby lowering the assembly efficiency and increasing the assembly cost. In addition, the presence of the projection makes it difficult to produce the link plates by punching due to a shortened service life of punching dies. This may add to the cost of the chain.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a chain having an improved rocker pin joint structure which is capable of holding rocker joint pins in a correct position against displacement relative to link plates.
Another object of the present invention is to provide a rocker pin joint structure of a chain, having a combination of a unique profile of the pin holes and a unique cross-sectional shape of the rocker joint pins, which is capable of preventing warping or reverse bend of the chain.
A further object of the present invention is to provide a chain having an improved rocker pin joint structure capable of withstanding a great load.
According to the present invention, there is provided a chain comprising a plurality of interleaved rows of link plates articulately connected together in an endless fashion by means of rocker pin joints. Each of the link plates has a pair of pin holes. Each of the rocker pin joints is composed of a pair of rocker joint pins inserted through each of the pair of pin holes in one link plate and each of the pair of pin holes in an adjacent link plate. The pair of rocker joint pins has a convexly arcuate rolling surface, a back surface opposite to the rolling surface, and a pair of upper and lower flat surfaces formed between the rolling surface and the back surface and extending in a longitudinal direction of the chain. Each of the pin holes has a seat surface engaged with the back surface and formed on a side located closer to an outer end of each link plate than to a center of the link plate, a pair of upper and lower pin-position constraining surfaces facing the upper and lower flat surfaces, respectively, of one of the pair of rocker joint pins seated on the seat surface with a very small clearance defined between each of the flat surfaces and a corresponding one of the pin-position constraining surfaces, a bend permitting surface contiguous to the upper pin-position constraining surface and spaced from the upper flat surface of the other rocker joint pin seated on the seat surface of the pin hole in the adjacent link plate, a warp blocking surface contiguous to the lower pin-position constraining surface and facing the lower flat surface of the other rocker joint pin seated on the seat surface of the pin hole in the adjacent link plate with a very small clearance defined therebetween, and a concavely arcuate surface contiguous to the bend permitting surface and the warp blocking surface and spaced from the back surface of the other rocker joint pin seated on the seat surface of the pin hole in the adjacent link plate.
When the chain is stretched substantially straight, the rocker joint pins are in contact with each other at their rolling surfaces within the pin holes of the two adjacent link plates.
Assuming that the one
Fukuda Shigekazu
Funamoto Takayuki
Horie Hiroshi
Iwasaki Yoshinori
Matsuno Kazumasa
Bucci David A.
Charles Marcus
Howson & Howson
Tsubakimoto Chain Co.
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