Power transmission chain constructed with asymmetrical links

A power transmission chain is formed of a plurality of randomly oriented s of links. Pivot means connect adjacent sets of links by fitting into a pair of apertures in the links. Each of the links of the chain has a pair of toes separated by a crotch. Each of the toes is defined by an outside flank and an inside flank. The links of the chain are asymmetrical in configuration with some links being oriented in a first direction and other links being oriented in the opposite direction. The asymmetrical form includes a first toe having an inside flank of a first configuration and a second toe having an inside flank of a different configuration. The first configuration includes either a substantially straight surface or a surface of a different configuration.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to power transmission chains. More 
particularly, the present invention relates to silent chain, that is, 
power transmission chain comprised of interleaved sets of inverted tooth 
links, with the links being of asymmetrical construction. 
2. Description of the Prior Art 
Power transmission chains are widely used in the automotive industry. Such 
chains are utilized for ignition timing as well as for the transfer of 
power from the engine to the transmission or for the transfer of power in 
a transfer case. Power transmission chains are also widely used in 
industrial applications. 
One type of power transmission chain is referred to as "silent chain". Such 
a chain is formed of interleaved sets of inverted tooth links. A set or 
rank of links is assembled from several links positioned alongside of or 
adjacent to each other. The links are connected by pivot means, which are 
typically round pins or rocker joint pins, received in a pair of 
apertures. The links each have a pair of teeth or toes, which are defined 
by outside and inside flanks. The inside flanks of the toes are joined at 
a crotch. 
The conventional power transmission chain drive comprises an endless chain 
of interleaved sets of links which is wrapped around two spaced sprockets 
supported on two generally parallel shafts. One of the shafts is typically 
the input shaft, which carries the driving sprocket, while the other shaft 
is the output shaft, which carries the driven sprocket. The links of the 
chain are adapted to fit over and about the teeth of the sprockets to 
enable the transmission of power from the input shaft and driving 
sprocket, through the chain, to the driven sprocket and output shaft. 
Historically, silent chains have been constructed in which all of the links 
have the identical shape or configuration and all oriented in the same 
direction. Silent chains of more recent vintage generally are constructed 
of links which are all of identical configuration and are symmetrical. The 
links of such chains are generally of a contour having both inside flanks 
of the links being substantially straight or, alternatively, having both 
inside flanks of the links being of a convex curve. The construction of 
the inside flanks of such links can also include alternative 
configurations, such as having a portion being straight, a portion being 
curved, or varying radii of curvature along the inside flank. Differences 
in design can affect the operation of the link within the chain structure. 
Power transmission chains have been used for many years in the automotive 
industry in both timing chain applications and power transfer 
applications. Chains having links with substantially straight inside 
flanks as well as chains having links with inside flanks of different 
configurations have been employed in these automotive applications. 
Historically, great care was taken in avoiding the mixing of these two 
types of links in chain assembly plants manufacturing both types of links. 
That is, great care was taken to produce chains with all links being of 
the identical type and configuration. 
However, it was found that a mixture of links of two different inside flank 
configurations in a chain provided a chain that generated less noise when 
used in automotive applications than did some chains constructed of links 
of all identical configuration. A chain containing a mixture of links of 
two different configurations is described in U.S. Pat. No. 4,342,560, 
issued on Aug. 3, 1982. That prior art patent describes the concept of the 
mixture of sets of links with an inside flank of a first configuration 
with sets of links with an inside flank of a different configuration. 
Those different configurations can be achieved by varying the dimensions 
of the links as well as the flank shapes or the aperture locations. 
The broad, generic concept of U.S. Pat. No. 4,342,560 was to change 
contacts between link flanks and sprockets by having differently 
configured link flanks in different sets of the chain. For example, in one 
species of the invention, some sets of links are comprised of links having 
at least one inside flank of a substantially straight configuration, while 
other sets of links are comprised of links having at least one inside 
flank of a different configuration. As the sprocket drives the chain, the 
sprocket teeth will contact the inside flanks of one configuration in one 
set of links, and will contact the inside flanks of another configuration 
in another set, or possibly the outside flanks of other links in the 
preceding set as a result of the different inside flank configuration at 
differing time intervals. Such differences alter or modify the contacts of 
the links with the sprocket. 
In another species of the invention of U.S. Pat. No. 4,342,560, for 
example, some sets of links are comprised of so-called inside engagement 
type links and other sets of links are comprised of so-called outside 
engagement type links. The actual engagement of the links in such a chain 
is determined by the positioning of the sets of various types of links 
with respect to one another. Of course, the concept of U.S. Pat. No. 
4,342,560 is broader than simply a combination of socalled inside 
engagement links and outside engagement links. 
Thus, U.S. Pat. No. 4,342,560 is directed to the generic concept of noise 
reduction in a chain by providing a chain with the interspersing or mixing 
of links having a first inside flank configuration with links having an 
inside flank of a different configuration. Such a chain utilizes the noise 
reduction technique of attempting to modify the pattern of sound emanating 
from the chain contacting the sprocket by altering the types of 
configurations and thus altering the point and rhythm of contacts. Prior 
to U.S. Pat. No. 4,342,560, patents and structures taught and suggested 
the use of the driving links of the chain (as opposed to the guide links 
on the outside solely for the purpose of guiding the chain) of all 
identical inside flank configuration. The prior art did not teach or 
suggest the mixing of sets of links of a first inside flank configuration 
with sets of links of a different inside flank configuration together in 
the same chain assembly. Indeed, the prior art U.S. Pat. No. 3,377,875 to 
Sand and U.S. Pat. No. 3,495,468 to Griffel, both taught the modification 
of the sprocket teeth, rather than modification of the profile of the 
chain link flank, in order to modify the rhythm of the chain and sprocket 
contacts. 
One advantage of using such a "hybrid" chain of two configurations of links 
is the avoidance of the need to modify the teeth of the sprocket. However, 
the two configurations of links must be kept separate during processing 
prior to assembly and then brought together to form the correct sets 
during manufacture. The optimal pattern of sets of links within the chain 
is determined prior to assembly and the separation of links prior to 
assembly is extremely important in order to achieve that pattern. As set 
forth in the U.S. Pat. Nos. 4,509,323 and 4,509,937, the outside upper 
surfaces of the links can be appropriately marked or identified by a shape 
in order to facilitate mixing of the links in proper positions during 
assembly. 
The present invention is a species of the generic concept set forth in U.S. 
Pat. No. 4,342,560. The present invention overcomes the problem of 
separation by providing a chain formed of links all having the same 
overall outside contour. However, the links are asymmetrical in contour 
and are then given different orientations in the chain in order to provide 
the same result as the hybrid chain of U.S. Pat. No. 4,342,560. The links 
of U.S. Pat. No. 4,342,560 achieve that result by a link with a leading 
inside flank of a first configuration mixed with a link with a leading 
inside flank of a second configuration. 
The links of the present invention are an asymmetrical combination of the 
two links of U.S. Pat. No. 4,342,560, which are oriented in two 
directions. Prior to assembly, when the links of the present invention are 
all oriented in the same direction, the links represent one link form. 
During and after assembly, the links comprise two links forms by virtue of 
their orientation in the claim assembly. In this manner, the links of the 
present invention perform the same function, contacting the sprocket in a 
random manner, in the same way, by having a link with a leading inside 
flank of a first configuration mixed with a link of a leading inside flank 
of a different configuration, to achieve the same result, modification of 
or altering of the chain and sprocket contacts. In the claims of both U.S. 
Pat. No. 4,342,560 and the present invention, the leading inside flank is 
modified by use of a different configuration of link or by orientation of 
the asymmetric link. Of course, in each case, the leading inside flank is 
the flank which primarily effects the link and sprocket contacts. 
OBJECTS OF THE INVENTION 
Accordingly, it is an object of this invention to provide a power 
transmission chain which provides alteration of chain and sprocket tooth 
contacts and yet avoids the necessity of separation of links prior to 
chain assembly. 
It is a specific object of this invention to provide a power transmission 
chain formed of asymmetrical links being oriented in some sets of links in 
a first direction and being oriented in other sets of links in a different 
direction. 
It is an object of this invention to provide a power transmission chain 
formed of asymmetrical links being oriented in some sets of links in a 
first direction and being oriented in other sets of links in a different 
direction, with the sets of links mixed in a predetermined random pattern. 
It is another object of this invention to provide a power transmission 
chain formed of asymmetrical links being oriented in some sets of links in 
a first direction and being oriented in other sets of links in a different 
direction, in which the chain can be operated in both directions. 
It is a further object of this invention to provide a power transmission 
chain formed of asymmetrical links which has an indication on the link to 
facilitate orientation of the links in the proper order in the chain. 
Other objects, advantages and features of the present invention will become 
apparent upon reading the following detailed description and appended 
claims, and upon reference to the accompanying drawings. 
SUMMARY OF THE INVENTION 
In accordance with one embodiment of this invention, a power transmission 
chain is comprised of a plurality of interleaved sets of metal links. 
Pivot means, preferably in the form of round pins, or other type of pivot 
joint, such as a pin and rocker joint, connect adjacent sets of links by 
fitting into a pair of apertures in the links. Each of the links of the 
chain has a pair of toes separated by a crotch. Each of the toes is 
defined by an outside flank and an inside flank, with the inside flanks of 
each link being joined at the crotch. The chain may also include guide 
links to guide the chain on the sprockets. Such guide links do not 
drivingly engage the sprocket teeth. 
The links of the chain are asymmetrical in configuration with some links 
being oriented in a first direction and other links being oriented in the 
opposite direction. The asymmetrical form includes a first toe having an 
inside flank of a first configuration and a second toe having an inside 
flank of a different configuration. The first configuration includes 
either a substantially straight surface or a curved surface. Both the 
first configuration and the different configuration can be curved 
surfaces. The curved surface is generally only along a portion of the 
inside flank of the link; a portion of the flanks of the links may be 
substantially identical. 
The differing curved surfaces of the inside flanks can be formed by 
differing radii of curvature as measured from points relative to the 
centerline. Alternatively, the differing curved surfaces can be formed by 
the same radius of curvature as measured from different points relative to 
the centerline. 
Each of the toes preferably contains a different configuration on the 
outside upper surface of the link. These upper surface configurations 
serve as designations of the particular toes to facilitate orientation of 
the links in the chain. 
The asymmetrical link forms can be constructed and arranged in a number of 
different patterns. For example, the chain can be constructed with a 
mixture of symmetrical links and asymmetrical links or two different 
asymmetrical links. 
Use of a chain constructed in accordance with the teachings of this 
invention with a sprocket results in the generation of a noise pattern 
that is modified in comparison with the noise pattern generated by a chain 
and sprocket in which all links are of an identical and symmetrical 
configuration. The differing orientations with the asymmetrical 
configuration modifies the pattern of contacts between the chain and the 
sprocket. The chain of this invention is suitable for use with a variety 
of sprocket tooth forms including sprockets in which the profile of the 
teeth is defined by an involute.

DETAILED DESCRIPTION OF THE DRAWINGS 
Turning now to the drawings, FIG. 1 illustrates a portion of a power 
transmission chain and sprocket drive including a chain 10 and a sprocket 
12. The sprocket 12 is driven about shaft 14 and includes a plurality of 
spaced teeth 16. The complete chain drive system includes at least a pair 
of sprockets which may be of different diameters and have a different 
number of differently shaped teeth. The sprocket teeth may be evenly or 
unevenly spaced. 
The chain is constructed of joined or interleaved sets 18, 20 of links 22. 
The sets or ranks 18, 20 are more clearly shown in FIG. 6. The shading in 
FIG. 6 is to identify a different orientation of the links, not a 
different configuration of the links. The sets are formed of a plurality 
of links placed in side-by-side relationship. The links of the interleaved 
set are preferably alternated by row with the links of the first set. The 
links 22 are asymmetrical in configuration and are shown in alternative 
embodiments in FIGS. 2, 3, 4, 7, 8, 9 and 10. The adjacent sets of links 
are joined by pivot means 24, illustrated as round pins. The pivot means 
are received in aligned sets of apertures 25. Each link preferably 
includes a pair of apertures 25, 26, located at opposite ends of the link. 
Guide links 28 are provided which maintain the lateral alignment of the 
chain on the sprockets. The guide links illustrated are along the outside 
of the chain and have no driving engagement with the sprocket teeth. Thus, 
the guide links are distinguished from the other toothed links 22, or 
driving links. An inside guide link (not shown) may also be used in which 
case the sprocket is grooved to receive the guide links. The pivot means 
24 are usually peened over to maintain the integrity of the chain 
assembly; however, other methods may be used if desirable. 
Each of the links 22 is of identical overall contour. The links are of 
asymmetrical form and are oriented in different directions in the ranks. 
For example, links in set 18 are oriented in a first direction, while the 
links in set 20 are oriented in the opposite, or reverse, direction. 
Link 22 is illustrated in FIG. 2 and is defined by a pair of spaced toes 
30, 32. The first toe 30 is defined by an inside flank 34 and an outside 
flank 36. The second toe 32 is defined by an inside flank 38 and an 
outside flank 40. The first toe 30 includes upper surface 42 while the 
second toe 32 includes upper surface 44. The upper surface is in the 
portion of the link above a horizontal centerline through the apertures. 
The upper surface 42 of the first toe 30 is extended to form an acute 
angle in contrast to the rounded shape of the upper surface 44 of the 
second toe 32. The different configurations of the upper surfaces 
facilitate identification of the portions of the link. The inside flanks 
34, 38 of the two toes are joined at crotch 46. 
The inside flank 34 of the first toe 30 is concavely curved in an inward 
direction or reverse direction of the link. The inside flank 38 of the 
second toe 32 is convexly curved, or bulging outward, with the center of 
curvature designated by the reference character 48. The radius of 
curvature 50 defines the curvature of the inside flank 38, relative to the 
center of curvature 48. 
The link is generally divided into two portions at the vertical centerline 
52. The centerline 52 extends approximately through the center of the 
crotch 46. The two portions of the link define two orientations of the 
link on the basis of the direction of the link in the chain. A first 
orientation is the link connected in the chain with the first toe leading 
the chain toward contact with the sprocket and the second toe following 
the first toe. A second orientation is the link connected in the chain 
with the second toe leading the chain toward contact with the sprocket and 
the first toe following the second toe. Thus, if the first orientation of 
the link is the link as shown in FIG. 2, the second orientation is the 
link reversed in direction, or flip-flopped in direction. 
The sets of links are preferably formed with the links oriented in the same 
direction. Thus, in assembling the chain, some sets of links are formed 
with the links oriented in a first direction and other sets of links are 
formed with links oriented in a second, or opposite, direction. By 
arranging the sets in such a manner, the pattern of contacts of the link 
flanks with the sprocket teeth is varied. In other words, the points and 
rhythm of the contacts of the links with the sprocket teeth is altered by 
the different orientations of links. Use of a chain constructed in this 
manner with a sprocket results in the generation of a noise pattern that 
is modified in comparison with the noise pattern generated by a chain and 
sprocket in which all links are of a identical and symmetrical 
configuration. 
The links shown in FIGS. 3, 4, 7, 8, 9 and 10 are alternative embodiments 
of the asymmetrical link shown in FIG. 2. In FIG. 3, the first toe 54 has 
a substantially straight inside flank 55. The term substantially straight 
implies a configuration which is generally straight, but is not 
necessarily limited to perfectly or absolutely geometrically straight. The 
second toe 56 has a curved inside flank 57. The curved inside flank 57 has 
a radius of curvature 58 as defined from reference character 59. 
The first toe 54 of the link 22 shown in FIG. 3 has an upper surface 60 
with a dip or inward curve 61. The second toe 56 has rounded upper surface 
62. The different configurations of upper surfaces 60, 62 facilitate 
identification of the links in either of the two available orientations. 
That is, a first orientation of the link with the first toe 54 leading the 
chain toward contact with the sprocket and the second toe trailing the 
first toe, and a second orientation of the link with the second toe 56 
leading the chain toward contact with the sprocket and the first toe 
trailing the second toe. 
The embodiment of the link 22 shown in FIG. 4 has a first toe 64 with a 
curved inside flank 66. The curved inside flank 66 has a radius of 
curvature 68 as defined from reference character 69. The second toe 70 
also has a curved inside flank 72. The curved inside flank 72 has a radius 
of curvature 74 as defined from reference character 75. Variation of the 
locations of the reference points 69, 75, as well as variation of the 
lengths of the radii of curvature 68, 74, results in variation of the 
curvatures of the inside flanks 66, 72. In this manner, the link 22 is 
provided with differing configurations of the first toe 64 and the second 
toe 70. 
The upper surface 76 of the first toe 64 is of a truncated curve, in 
contrast to the rounded curve of the upper surface 78 of the second toe 
70. The different configurations of the upper surfaces 76, 78 facilitate 
identification of the links in either of the two available directions or 
orientations. 
The sets or ranks of links can be assembled in many patterns. As shown in 
FIGS. 5 and 6, the sets of links in a first orientation may be altered 
with the sets of links in the different orientation. The alteration of 
sets may occur in a repeated pattern of sets or in a predetermined random 
pattern of sets. Alternatively, the links may be randomly oriented 
throughout the chain. For example, the links can be alternated in each 
rank, with the alterations staggered in each row. A row of links is the 
series of links in a particular location of the rank as viewed 
longitudinally of the chain. Thus, the links in a row are typically not 
directly interleaved, but spaced; the links are interleaved with the 
adjacent link in the adjacent rank. 
An alternative embodiment of the asymmetrical link 22 is shown in FIG. 7. 
The link has a first toe 80 and a second toe 82. The first toe is formed 
by inside flank 84 and outside flank 85, while the second toe is formed by 
inside flank 86 and outside flank 87. The pair of apertures 88, 90 include 
centers as marked by reference characters 91, 92. The asymmetrical 
configuration of the link is achieved by differences in the distances from 
the centers of the apertures to the flanks of the toes. In the first toe 
80, the distance from the aperture center 91 to the inside flank 84, as 
shown by line 94, is greater than the distance from the aperture center 91 
to the outside flank 85, as shown by line 95. In the second toe 82, the 
distance from the aperture center 92 to the inside flank 86, as shown by 
line 96, is less than the distance from the aperture center 92 to the 
outside flank 87, as shown by line 97. The distances 94, 95 can also be 
measured by the perpendicular distance from the center of the nearest 
aperture or pin hole opening to the tangents of the inside and outside 
flanks. 
The alternative embodiment of link 22 shown in FIG. 7 can be constructed 
with other relative aperture center to flank distances. For example, the 
distance from the aperture centers to the inside flanks of both toes can 
be greater than the distance from the aperture centers to the outside 
flanks of both toes, as long as the distances are such so as to create an 
asymmetrical link. The results of the invention are achieved by the 
utilization of the links in some sets of the chain in a first orientation 
and in other sets of the chain in the opposite orientation. The upper 
surfaces 100, 102 of the two toes are differently shaped in order to 
facilitate orientation of the links in the chain. 
Another alternative embodiment of the asymmetrical link 22 is shown in FIG. 
8. The link has a first toe 104 and a second toe 106. The first toe is 
formed by diverging inside flank 108 and outside flank 110, while the 
second toe is formed by diverging inside flank 112 and outside flank 114. 
The asymmetrical configuration of the link is achieved by differences in 
the widths of the toes of the links. The width of the first toe 104, as 
shown by distance 116 at an arbitrary point 118 along the inside flank 
108, is different from the width of the second toe 106, as shown by 
distance 120 at the same point 122 relative to the centers of the 
apertures 124, 126. The differences in the widths of the toes, or the 
distances of separation of the flanks, provides an asymmetrical link. The 
alternative embodiment of FIG. 8 can also be constructed by shortening the 
second toe relative to the first toe. That is, forming the link with 
different distances 123, 125 from the aperture centers 124, 126 to the 
bases of the first and second toes 104, 106, so that one toe is longer 
than the other toe. For example, distance 123 would be greater than 
distance 125, resulting in toes of different lengths. 
Another alternative embodiment of the asymmetrical link 22 of the chain of 
the present invention is shown in FIG. 9. The link has a first toe 130 and 
a second toe 132. The first toe is formed by inside flank 133 and outside 
flank 134, while the second toe is formed by inside flank 135 and outside 
flank 136. 
The asymmetrical configuration of the link of FIG. 9 is achieved by 
differences in the distances from the link centerline to the centerlines 
of the first and second toe. The link includes a pair of apertures 138 and 
140, which are preferably equally spaced from the link centerline 142. 
That is, the distance 143 from the centerline 142 to the center of the 
first aperture 138 is equal to the distance 144 from the centerline 142 to 
the center of the second aperture. The distances 143, 144 are measured 
along the horizontal centerline of the link in FIG. 9. 
The first toe 130 has a first centerline 146 through its center, while the 
second toe has a second centerline 148 through its center. The distance 
150 from the first toe center line 146 to the link centerline 142 is not 
equal to the distance 152 from the second toe centerline 148 to the link 
centerline 142. The distances in toe separation provides an asymmetrical 
link. 
Another alternative embodiment of the asymmetrical link 22 of the chain of 
the present invention is shown in FIG. 10. The link has a first toe 160 
and a second toe 162. The first toe is formed by inside flank 163 and 
outside flank 164, while the second toe is formed by inside flank 165 and 
outside flank 166. 
The asymmetrical configuration of the link of FIG. 10 is achieved by 
difference in the distances from the centers of the apertures to the 
working surfaces or contacting surfaces of the inside and outside flanks 
of the link. The link includes a first aperture 168, which is located 
along the centerline of the link, and a second aperture 170, which is 
located at a position rotated through angle 172 from the centerline. By 
locating the apertures at different relative positions with respect to the 
inside and outside flanks of the link, an asymmetrical configuration is 
achieved. Such an embodiment may also be constructed by locating either or 
both apertures vertically or horizontally at different relative positions 
with respect to vertical centerline 174 and horizontal centerline 175 of 
the link. 
The apertures 168, 170 shown in FIG. 10 are of the rocker joint variety 
having a generally hour-glass shape of two oral portions connected at 
extending points or eyebrows 176, 177. The pivot means is constructed of 
two generally oval or D-shaped pins 178, 180 which are interconnected 
within the apertures. The oval portions of the apertures 168, 170 are of 
two different sizes, as shown in FIG. 10, with oval portion 182 being 
larger than oval portion 184. The pins have a substantially tight fit 
within oval 182 while oval 184 allows free pin rotation. Thus, when the 
links are oriented in different directions, the pins of the rocker joint 
will roll against one another. The rocker joint pivot means can be used, 
where practical, with other embodiments of the invention than the 
embodiment shown in FIG. 10. 
While several embodiments of the invention are illustrated, it will be 
understood that the invention is not limited to these embodiments. Those 
skilled in the art to which the invention pertains may make modifications 
and other embodiments employing the principles of this invention, 
particularly upon considering the foregoing teachings.