Power transmission chain having a spring link

A power transmission chain with a spring link of improved durability. The chain includes a plurality of link plates. Each of the links has a pair of pinholes. The links are interleaved and are connected by rocker joints inserted in the pinholes. Guide links are placed at the outermost sides of the inner links. A spring link with a pair of pinholes formed in it is placed between adjacent link plates. The link plate contacting parts at both ends of spring link are located outside of the link apertures. The spring links may also be placed in the chain in two different orientations.

BACKGROUND OF THE INVENTION 
This invention relates to a silent or inverted tooth chain for transmitting 
power in an automobile, motorcycle or other vehicle. More specifically, 
this invention relates to a power transmission chain having a large number 
of interleaved links. The links are arranged in rows or sets and connected 
by connecting pins. Guide links are located at the outermost sides of 
alternate sets of links. Spring links are included in some rows or sets of 
links. 
In conventional silent chains used as a power transmission chain for 
automobiles and motorcycles, spring links are typically used for reduction 
of chordal vibration of the chain and reduction of the chain noise. An 
example of a conventional chain of the prior art is shown in FIGS. 4 and 
5. In this chain, a large number of inverted tooth links or link plates 51 
are interleaved in rows by connecting pins 52. Guide links or guide plates 
53 are located at the outermost sides of alternate sets of links. The 
inverted tooth links are constructed and arranged to articulate with 
respect to one another, and transmit power, as the chain passes over the 
sprockets. The guide links act to maintain the chain on the sprockets. 
Additionally, spring link 54 is located or sandwiched between one guide 
plate 53 and its adjacent link plate 51. Spring link 54 has one pair of 
apertures or pinholes 54a for insertion of connecting pins, as shown in 
FIG. 5, and its center portion is pressed against the guide plate 53 while 
both of its ends are pressed against the link plate 51. As the links move 
around the sprockets and articulate with respect to one another, friction 
occurs between adjacent link plates 51 and the bending resistance of the 
chain is increased because of the elastic repulsive force of this spring 
link 54. As a result, the chordal vibration of the chain is reduced or 
suppressed. 
In this conventional silent chain, the guide plate contacting parts at both 
ends of spring link 54 contact the edge of aperture 54a, as shown in the 
cross-hatched part D of FIG. 5(a) and the circled location D' of FIG. 
5(b). Therefore, the aperture or pinhole edge that intersects the 
cross-hatched part D tends to become the point of origin of fatigue, which 
decreases the durability of the spring link. 
Other examples of power transmission chains with spring links are found in 
U.S. Pat. No. 5,090,948 (particularly FIG. 16), U.S. Pat. No. 5,167,587 
(particularly FIG. 16), and U.S. Pat. No. 5,007,883 (particularly FIGS. 
14-16), each of which is incorporated herein by reference. 
The present invention is directed to the above-described problems in the 
conventional chains, and offers a power transmission chain that further 
improves the durability of the spring link. 
SUMMARY OF THE INVENTION 
This invention is concerned with a power transmission chain in which a 
plurality of link plates, each having pair of apertures or pinholes in 
each link plate, are connected into rows or sets of links by connecting 
pins inserted in the pinholes. Guide links are located on the outermost 
sides of some of the sets of links. In one embodiment, the power 
transmission chain of the present invention has a spring link that 
includes a pair of apertures for insertion of the connecting pins. The 
spring link is placed in the sets of links between a guide link and an 
inner link or between adjacent inner links. Additionally, the spring link 
contacts or presses against the guide link or inner link at both ends of 
the spring link at the outside of the apertures of the spring link. By 
having the spring link contact the guide link or inner link at both ends 
of the spring link outside of the aperture edges, the durability of the 
spring link is improved by altering the location of the point of origin of 
fatigue of the spring link. In one embodiment, the orientations of the 
spring links are reversed in alternate rows in order to allow a longer 
spring link without interference with the neighboring spring link.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawings, as shown in FIGS. 1 and 2, silent chain 1 has 
a plurality of link plates 2, each of which has a pair of inverted teeth 
21 and a pair of apertures or pinholes 22. The links are interleaved in 
sets or rows of links and the link plates 2 are pivotally connected by 
inserting rocker joints 3 into the apertures. Each rocker joint includes a 
pair of long and short rocker pins. Guide links or guide plates 4 are 
located at the outermost sides of the rows of link plates 2. 
Spring link 5, shown in FIG. 3, is inserted 5 in the compressed state at 
about the center in the width direction of silent chain 1. Spring link 5 
is a wavy-form member and has a pair of apertures or pinholes 5a for 
insertion of rocker joint. The center part of spring link 5 is in pressure 
contact with the center part of opposing link plate 2 and both of its ends 
are in pressure contact with the center parts of two opposing link plates 
2, 2. Frictional force is generated between adjacent link plates 2, 2 due 
to the elastic repulsive force of spring link 5 in the chain width 
direction. Accordingly, the bending resistance of the chain is increased 
and, as a result, the chordal vibration of the chain increases and the 
noise of the power transmission chain is reduced. 
The link plate contacting parts, or portions of the spring link that 
maintain pressure contact with the inner links, are located at both ends 
of spring link 5 toward the ends of the spring link 5. The contacting 
parts are located outside the edge of pinhole 5a, as shown in 
cross-hatched part A in FIG. 3(a) and circle-marked part A' in FIG. 3(b). 
Therefore, the number of locations where fatigue can originate is reduced 
and the durability of spring link 5 is improved. Also, the outside 
location of the link plate contacting part of spring link 5 from the 
pinhole edge increases the area of link plate contacting part to reduce 
surface pressure acting on spring link 5, so that the wear of spring link 
5 is reduced. Incidentally, spring link 5 is placed between adjacent link 
plates 2, 2 in the above-described embodiment, but this invention can be 
similarly applied to the placement of spring link 5 between link plate 2 
and guide plate 4, as shown in the conventional chain of FIG. 4. 
In the embodiment of FIG. 2, the spring link has the same orientation in 
each of the rows of links. Alternatively, as shown in FIG. 6, the 
orientation of the spring link may be reversed and alternated in every 
other spring link row. That is, the spring links are located in a sequence 
wherein the link is in the first orientation in the first row and then in 
the reverse orientation in the next row and then in the first orientation 
in the next row and so forth. As shown in FIG. 6, the spring links are 
only placed in alternate rows of the chain, and then in alternate 
orientation in alternate rows. In this manner, the spring links avoid 
contact with one another as the links spread out or lengthen in the 
longitudinal direction of the chain as a result of the pressure on the 
spring links from adjacent links in each spring link row. 
In the above-described embodiments, this invention is applied to a rocker 
joint-type silent chain. This invention can also be applied to the silent 
chain that uses round pins instead of rocker joints. Furthermore, this 
invention can be similarly applied to a random chain or CVT (Continuously 
Variable Transmission) chain (see Japanese Laid-Open Patent Heisei 
1-145447). 
As explained above, in operation, guide plate contacting parts or link 
plate contacting parts of the spring link are located outside of the 
pinholes of the spring link at both ends of the spring link. In this 
manner, the durability of the spring link is improved.