Power transmission belt

A power transmission belt having a compression section defined by a plurality of portions having different contents of transversely extending short fibers therein. In one form, the different portions of the compression section are separated by a bonding layer. In one form, where the difference between the fiber content of the respective layers is minimized, the bonding layer is omitted. A number of different configurations of the power transmission belt incorporating such different compression section portions is disclosed.

TECHNICAL FIELD 
This invention relates to power transmission belts and in particular to 
power transmission belts formed of elastomeric material. 
BACKGROUND ART 
In one conventional form of power transmission belt, a plurality of 
longitudinally extending tensile cords are provided in a cushion rubber 
section thereof. The belt further defines an inner compression section 
conventionally formed of an elastomeric material, such as rubber. 
In one form of such belt, short fibers are provided in the rubber of the 
cushion section. 
It is further conventional to provide cover fabric on the outer surface of 
the belt and on the inner surface of the compression section of the belt. 
By maintaining the side surfaces of the V-belt raw edge, a high friction 
coefficient with the confronting surfaces of the pulley groove is 
obtained. The provision of the transverse fibers in the compression 
section minimizes deformation of the belt in the driving operation as a 
result of the relatively large lateral pressure on the compressed part of 
the belt. 
In one prior art construction, the compression layer is formed of an inner 
layer and an outer layer having different hardnesses. A problem has 
arisen, however, in such construction in that separation of the layers 
along their interfaces tends to occur after a relatively short use of the 
belt due to the deterioration of adhesion between the layers caused by 
heat generated in the driving operation and as a result of their 
relatively large lateral pressure acting on the compression section. 
DISCLOSURE OF THE INVENTION 
The present invention comprehends an improved power transmission belt 
overcoming the problems of the prior art as discussed above, in a novel 
and simple manner. 
The power transmission belt of the present invention provides a silent 
running belt having a plurality of layers defining the cushion section 
constructed to avoid the problem of layer separation found in the prior 
art belts. 
More specifically, the invention comprehends an improved power transmission 
belt including a cushion section having longitudinally extending tensile 
cords distributed therein, and a compression section formed of an 
elastomeric material and having an outer portion adjacent the cushion 
section and an inner portion inwardly of the outer portion, the outer 
portion having short fibers distributed therein and the inner portion 
having short fibers distributed therein, the parts by weight of the short 
fibers in the inner portion elastomeric material being less than the parts 
by weight of the short fibers in the outer portion elastomeric material. 
In one embodiment, means are provided between the outer and inner portions 
of the compression section bonding the inner and outer portions to each 
other. 
The belt may include an inner section overlying the cushion section formed 
of at least one layer of fabric, and in one embodiment, a tension section 
is provided inwardly of the cushion section which, in turn, is covered by 
a fabric layer. 
In the illustrated embodiments, the cushion and compression sections define 
raw edge side surfaces of the belt. 
The short fibers, in the illustrated embodiment, extend transversely of the 
compression section. 
The short fibers are preferably provided in the range of approximately 30 
to 50 parts by weight of the fibers to 100 parts by weight of the 
elastomeric material in the outer portion of the compression section. 
The short fibers are preferably provided in the range of approximately 10 
to 40 parts by weight of the short fibers to 100 parts by weight of the 
elastomeric material in the inner portion of the compression section. 
In the illustrated embodiment, the elastomeric material of the compression 
section comprises rubber. The short fibers may comprise cotton fibers, 
nylon fibers, rayon fibers, etc., and may be woolly processed. 
In the illustrated embodiment, the outer portion of the compression section 
has a hardness greater than the hardness of the inner portion of the 
compression section. 
In the illustrated embodiment, the outer portion of the compression section 
has a hardness in the range of approximately 85-92 and the inner portion 
of the compression section has a hardness in the range of approximately 
76-88. 
In the preferred embodiment, the parts by weight of the short fibers in the 
inner portion of the compression section is at least 10 less than the 
parts by weight of the short fibers in the outer portion. 
In the illustrated embodiment, the portion by weight of short fibers in the 
inner portion of the compression section is in the range of approximately 
10-40 less than the parts by weight of the short fibers in the outer 
portion. 
In the illustrated embodiment, the means for bonding the inner and outer 
portions to each other comprises a layer of bonding rubber having a 
thickness in the range of approximately 0.05 to 0.20 mm. 
In the preferred embodiment, the bonding layer has a hardness less than 
that of the compression section portions and, illustratively, is in the 
range of approximately 62-80. 
The bonding layer may have ceramic particles, such as ceramic powder, 
ceramic whiskers, etc., distributed therein. 
In one embodiment, the boundary between the first and second portions of 
the compression section is wavy. In another embodiment, the boundary 
therebetween is flat. 
In one embodiment, a tension section is provided outwardly of the cushion 
section. The tension section comprises an inner portion similar to the 
outer portion of the compression section and an outer portion similar to 
the inner portion of the compression section and, thus, defines, with the 
compression section and cushion section, a reversible belt. 
The compression section may define ribs or cogs. 
In one embodiment, a cord layer is provided between the cushion section and 
compression section. The cord layer, in the illustrated embodiment, 
comprises a layer of elastomeric material having a plurality of cords 
spaced longitudinally of the belt and extending transversely thereacross. 
In one embodiment, a cord layer is disposed outwardly adjacent the cushion 
section. In one embodiment, the compression section further includes an 
innermost portion having short fibers distributed therein, the short 
fibers in the innermost portion being present in an amount less than that 
of the outer portion and inner portion of the compression section. In the 
illustrated embodiment, the short fibers in the inner most portion are 
prsent in the range of approximately 10 to 40 parts by weight. 
The power transmission belt of the present invention is extremely simple 
and economical of construction, while yet providing the highly desirable 
features discussed above.

BEST MODE FOR CARRYING OUT THE INVENTION 
In the illustrative embodiment of the invention as disclosed in FIG. 1 of 
the drawing, a power transmission belt generally designated 10 is shown to 
include a cushion section 11 having longitudinally extending tensile cords 
12 distributed therein. The belt further defines a compression section 
generally designated 13. 
The compression section includes an outer portion 14 and an inner portion 
15. The outer portion has a plurality of short fibers 16 distributed 
therein, and the inner portion has a plurality of short fibers 17 
distributed therein. In the illustrated embodiment, the fibers 17 are 
similar to the fibers 16. The invention comprehends that the parts by 
weight of the fibers 17 in the inner portion 15 of the compression section 
be less than the parts by weight of the short fibers 16 in the outer 
portion 14 of the compression section. 
Means are provided for bonding the outer portion 14 to the inner portion 15 
in the belt 10. As shown in FIG. 1, the bonding means may comprise a layer 
18 of bonding rubber. 
The belt further includes an inner section generally designated 19 formed 
of at least one layer of fabric 20. 
As seen in FIG. 1, the belt comprises a V-belt raw side edges, i.e. the 
side edges of the belt are free of cover fabric. 
More specifically, the short fibers 16 and 17 extend transversely of the 
compression section. The short fibers 16 in the outer portion 14 of the 
compression section are present, in the illustrated embodiment, in the 
range of approximately 30 to 50 parts by weight of the short fibers to 100 
parts by weight of the elastomeric material forming the outer portion 14. 
In the illustrated embodiment, the short fibers 17 in the inner portion of 
the compression section are present in the range of approximately 10 to 40 
parts by weight of the short fibers to 100 parts by weight of the 
elastomeric material forming the inner portion 15. 
In the illustrated embodiment, each of the cushion section and inner and 
outer portions of the compression section are formed of rubber. 
Illustratively, the short fibers may comprises cotton fibers, nylon 
fibers, rayon fibers, etc., and may be woolly processed or unprocessed 
fibers, as desired. 
The hardness of the outer portion 14 may be greater than the hardness of 
the inner portion 15 of the compression section and, in the illustrated 
embodiment, the outer portion 14 has a hardness in the range of 
approximately 85-92 JIS Hardness, and the inner portion 15 has a hardness 
in the range of approximately 76-88 JIS Hardness. 
Preferably, the parts by weight of the short fibers 16 in the outer portion 
14 of the compression section is at least 10 less than the parts by weight 
of the short fibers 17 in the inner portion 15 thereof. 
In the illustrated embodiment, the parts by weight of the short fibers 17 
is in the range of approximately 10-40 less than the parts by weight of 
the short fibers 16 in the outer portion 14. 
In the illustrated embodiment, the compression section portions 14 and 15 
are bonded together by the bonding rubber layer 18, as discussed above. 
The bonding rubber layer illustratively may have a thickness in range of 
approximately 0.05 to 0.20 mm, and may be formed of a rubber material 
similar to that of the cushion section 11. Preferably, the bonding rubber 
has a hardness less than that of the compression section portions 14 and 
15 rubber. Illustratively, the bonding layer rubber may have a hardness in 
the range of approximately 62-80 JIS. 
The bonding rubber layer 18 may have ceramic particles distributed therein. 
Illustratively, the particles may comprise ceramic powder, ceramic 
whiskers, etc. 
In the belt 10, the bonding rubber layer is substantially flat, as 
illustrated in FIG. 1. 
In the illustrated embodiment, the cushion rubber is formed of any one or 
more of natural rubber, styrene butadiene rubber, chloroprene rubber, and 
nitrile butadiene rubber. Short fibers may be provided in the cushion 
section as desired, and such fibers may be raw fibers or fibers treated 
for improved adhesion with the cushion section rubber. Where short fibers 
are provided in the cushion section, they may be provided in the range of 
up to approximately 20 parts by weight of such fibers to 100 parts by 
weight of the cushion section rubber. 
The tensile cords may be formed of conventional material, such as polyester 
fibers, nylon fibers, aromatic polyamide fibers, etc. 
The fabric cover layer 20 may be formed of up to seven layers of 
conventional rubberized biased canvas. In the illustrated embodiment, the 
wefts have a relatively wide angle in the range of approximately 
80.degree. to 120.degree. . Alternatively, the canvas may be woven with 
woolly finished curly nylon warps and conventional nylon wefts. 
The compression section rubber preferably consists of one or more of 
natural rubber, chloroprene rubber, Hypalon rubber manufactured by duPont, 
epichlorohydrin rubber, and hydrogenated nitrile butadiene rubber. 
It has been found that the inner portion having the indicated amount of 
embedded short fibers has a low friction coefficient, thereby reducing the 
noise level in the operation of the drive using the belt 10. The reduction 
in the amount of transverse fibers in the inner section 15 provides for 
improved bending flexibility of the belt and extended useful life. Thus, 
belt 10 exhibits both relatively low noise characteristics and long, 
troublefree life resulting from the controlled flexibility of the 
compression section. 
The specific amounts of short fibers in the compression section portions 
may be varied depending on the desired operating characteristics. 
Illustratively, where the drive has a relatively large load and a 
relatively large pulley diameter, the parts by weight of the short fibers 
16 is preferably about 50 and the parts per weight of the short fibers 17 
is preferably about 40. Where the drive has a relatively small load and a 
relatively small pulley diameter, the short fibers 16 may be present in 
the amount of approximately 30 parts by weight, and the short fibers 17 
present in the amount of approximately 10 parts by weight. 
Where a large load and a small pulley diameter are utilized in the drive, 
the short fibers 16 may be provided in parts by weight of approximately 50 
and the short fibers 17 may be provided in parts by weight of 
approximately 20. Where the drive is one having a large load and a small 
pulley diameter under high ambient temperature conditions, it has been 
found desirable to provide the short fibers 16 in parts by weight of 
approximately 50 and the short fibers 17 in parts by weight of 
approximately 10. 
The bonding rubber layer 18 is preferably relatively soft having a 
composition similar to that of the cushion rubber layer 11. Preferably, 
the hardness of the bonding rubber layer is in the range of approximately 
62 to 80 JIS, and preferably lower than that of either of the compression 
section portions 14 and 15. 
The selection of the rubber in forming different portions of the belt may 
be based on the necessary characteristics for the particular use thereof. 
Thus, where resistance to low temperature is desired, natural rubber is 
preferable. It has been found desirable to use natural rubber for the 
inner portion 15 of the compression section to provide desirable cold 
resistance. Chloroprene rubber has been found to be advantageous for use 
as the rubber material of compression section portion 14, wherein the 
larger content of short fibers is provided, so as to provide the desired 
high deformation resistance. It has been found advantageous to use either 
the natural rubber or chloroprene rubber for the bonding layer 18 to 
provide both high cold resistance and deformation resistance. 
Referring now to FIG. 2, a modified form of power transmission belt 
generally designated 110 is shown to comprise a power transmission belt 
similar to power transmission belt 10 but wherein the boundary between the 
outer compression section portion 114 and the inner compression section 
portion 115 is wavy and, thus, the bonding layer 118 finds a wavy 
configuration, as shown. In all other respects, the power transmission 
belt 110 is similar to and functions similar to the power transmission 
belt 10. 
A further modified form of modified power transmission belt generally 
designated 210 is shown in FIG. 3 to comprise a power transmission belt 
generally similar to power transmission V-belt 10, but wherein a tension 
section generally designated 221 is provided outwardly of the cushion 
section 211. The tension section comprises a configuration reversely 
similar to that of the compression section generally designated 213 and, 
thus, includes an inner portion 222 provided with transversely extending 
short fibers 216, and an outer portion 223 provided with transversely 
extending short fibers 217. The inner portion 222 is similar to outer 
portion 214 of the compression section 213, and the outer portion 223 is 
similar to the inner portion 215 of the compression section. Thus, the 
parts by weight of the short fibers 217 in the outer portion of the 
tension section is less than the parts by weight of the short fibers 216 
in the inner portion of the tension section, and the more specific 
characteristics thereof similar to the characteristics discussed relative 
to the components of the compression section 13 of belt 10. 
Belt 210 includes an outermost fabric layer portion 220 similar to fabric 
layer portion 20 of belt 10. In addition, the inner surface of the 
compression section may be provided with an underlying fabric layer 224. 
The inner fabric layer 224 may be similar to fabric layer 20 of belt 10 
and the fabric layer 220 of belt 210. 
As shown in FIG. 3, a bonding layer 225 may be provided between tension 
section portions 222 and 223, the characteristics of bonding layer 225 
being similar to those described relative to bonding layer 18 in belt 10. 
A bonding layer 218 may be provided between the compression section 
portions 214 and 215, as in belt 10. 
Thus, a plurality of belts 210 may be formed from a common flank by 
longitudinal separation of the respective belts therefrom, as each of the 
belts is reversely similar. Thus, low cost manufacture of the belt 210 may 
be effected by elimination of waste in the formation thereof from a common 
belt blank. 
A further modified form of power transmission belt generally designated 310 
embodying the invention comprises a belt generally similar to power 
transmission belt 10, but wherein the compression section is provided with 
a plurality of longitudinally extending grooves 326 forming, in the 
compression section, a plurality of transversely spaced, longitudinally 
extending ribs 327. As shown in FIG. 4, the grooves may extend fully 
through the inner portion 315 of the compression section, the bonding 
layer 318 thereof, and at least partially through the outer portion 314 of 
the compression section. Belt 310 is adapted to be used with a multiple 
groove pulley, with each of the ribs 327 being received in a respective 
pulley groove thereof, and effectively providing the desirable low noise 
and low friction characteristics of the power transmission V-belt 10. 
In all other respects, the belt 310 is similar to and functions in a manner 
similar to power transmission belt 10. 
Another modified form of power transmission belt embodying the invention is 
shown in FIG. 5 to comprise a power transmission belt generally designated 
410. Belt 410 comprises a cogged belt having a plurality of cogs 428 
defining the inner surface thereof. Belt 410 further differs from power 
transmission belt 10 in the provision of a third, innermost compression 
section portion 429 inwardly of the inner portion 415 of the compression 
section. Innermost portion 429 is provided with transversely extending 
short fibers 430 similar to the short fibers 16 and 17 of belt 10. The 
parts by weight of the short fibers 430, in the innermost portion 429, is 
less than the parts by weight of the short fibers 417 in the inner portion 
415, which, in turn, is less than the parts by weight of the short fibers 
416 in the outer portion 414 of the compression section. 
An inner cord fabric layer generally designated 431 is provided 
intermediate the cushion section 412 and the outer compression section 
portion 414. Between the cushion section 412 and the outer fabric layer 
419 is a second cord fabric layer 432. Each of these layers comprises a 
plurality of transversely extending cords 433 providing increased rigidity 
in the transverse direction of the belt. The cords may be formed of 
polyester, nylon, aromatic polyamide, glass, carbon, etc., fibers. 
The content of the short fibers 416 in the inner compression section 
portion 414 is preferably in the range of approximately 30 to 60 parts by 
weight to 100 parts by weight of the rubber, thereby providing improved 
rigidity in the transverse direction of the belt. The content of the short 
fibers 417 in the inner portion 415 of the compression section is 
preferably in the range of approximately 20 to 50 parts by weight to 100 
parts by weight of the rubber. The contents of the short fibers 430, in 
the innermost portion 429 of the compression section, is preferably in the 
range of 10 to 40 parts by weight to 100 parts by weight of the rubber, 
thereby providing improved belt durability. 
It is preferred that the difference in the content of the short fibers 
between the respective layers is less than 20 to permit bonding between 
the respective layers of the compression section without the provision of 
the bonding layers provided in the previously described embodiments. 
The cord layers 431 and 432 preferably comprise layers of elastomeric 
material having a plurality of the cords 433 spaced longitudinally of the 
belt therein. 
In a preferred embodiment, the short fiber 430 content in the innermost 
compression section portion 429 is in the range of 10 to 40 parts by 
weight to 100 parts by weight of the rubber. The content of the short 
fibers 417 in the inner portion 415 is in the range of approximately 20 to 
50 parts by weight, and the content of the short fibers 416 in the outer 
portion 414 is preferably in the range of 30 to 60 parts by weight. 
Other than as discussed above, power transmission belt 410 is similar to 
and functions in a manner similar to power transmission belt 10, as 
discussed above. 
The foregoing disclosure of specific embodiments is illustrative of the 
inventive concepts comprehended by the invention.