Method of making banded belts

A method of producing endless power transmission belts having a plurality of longitudinal ribs by the steps of forming an annular belt sleeve, positioning the sleeve on a continuous curing apparatus, forming longitudinal ribs in the compression section, and curing the formed belt. An additional step of stabilizing the cured belt is provided when the belt has a load-carrying cord of polyester.

BACKGROUND OF THE INVENTION 
There are numerous types of endless power transmission belts in present use 
which are made primarily of elastomeric materials, known as V-ribbed 
belts. These belts have longitudinal ribs in the compression section as an 
integral part of the belt, and the ribs may be V-shaped or in the form of 
truncated Vees. The fabrication of such belts is usually complex and 
expensive, and there is a constant effort to find new ways of 
manufacturing which are simpler and less costly. 
Some of the most recent methods of making belts of this type are disclosed 
in U.S. Pat. Nos. 3,822,516; 3,839,116; 3,891,405; and 3,981,206. The use 
of such belts is illustrated by U.S. Pat. Nos. 3,951,006; 4,028,995; and 
4,031,761. 
The present invention is an improvement over the prior art, particularly 
with respect to the number of fabricating steps necessary to produce a 
V-ribbed belt. According to the present invention, a belt sleeve is 
fabricated by assembling the various components in a conventional manner 
on a drum. However, instead of using curing devices such as shown in U.S. 
Pat. Nos. 3,839,116 and 3,981,206, the curing is accomplished on a curing 
mechanism known as "Rotocure", which comprises a heated cylinder and an 
endless band passing around the cylinder. Such a mechanism is shown, for 
example, in U.S. Pat. No. 2,039,271. 
While it is known to treat a complete sleeve of material in order to form 
it into individual belts, for example as outlined in U.S. Pat. Nos. 
3,477,895 and 3,565,984, the present invention is an improvement over the 
teaching of these patents, in that sufficient rubber is employed in 
fabricating the belt sleeve to completely fill the grooved roller during 
the forming process so that the load-carrying cord is continuous across 
the sleeve. The load-carrying cord, according to the present invention, is 
not cut into individual belt widths and is not compressed into the body of 
the belt, which would result in distortion. 
A further feature of the method of this invention is that belts having 
polyester load-carrying cord are formed completely on the vulcanizing 
apparatus and do not require subsequent stabilization on a separate 
apparatus as is disclosed in U.S. Pat. No. 3,761,558. 
It is therefore an object of the present invention to provide an improved 
process for producing a V-ribbed belt. 
Other objects, aspects and several advantages of the present invention will 
be apparent to those skilled in the art from a reading of the following 
detailed description, as well as the appended claims. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a process for 
producing a V-ribbed belt comprising a compression section, a 
load-carrying section and a tension section, which belt has a plurality of 
longitudinal ribs, either V-shaped or of truncated V-shape, in the 
compression section. The process of the present invention comprises the 
steps of: 
a. Fabricating a belt sleeve comprising an inner compression layer of 
moldable uncured rubber, a load-carrying layer of helically-wound cord, 
and an outer tension layer; 
b. Positioning the belt sleeve over a rotatably mounted vulcanizing 
cylinder having a plurality of axially spaced circumferential mold ribs 
forming belt element grooves therebetween, and in contact with the ribs; 
c. Tensioning the belt sleeve; 
d. Applying pressure to the tension section of the belt sleeve while 
rotating the vulcanizing cylinder to thereby force the compression layer 
into the grooves, forming the belt elements; and 
e. Curing the rubber while in the grooves.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The initial operations involved in the forming of the belt sleeve according 
to the present invention are substantially identical to those used in the 
prior art. The belt sections are built up in a sleeve form onto a mandrel, 
either a fixed or an expansion mandrel, which is well known in the V-belt 
manufacturing art. Generally, the elements of the sleeve include a layer 
of compression rubber, a layer of tension members which usually include a 
single helically wound cord, and a layer of top rubber or 
rubber-impregnated fabric. It is presently preferred that the sleeve also 
include layers of cushion stock arranged above and below the tension 
members. The belt sleeve, when built in this manner, is substantially 
identical to that of the prior art. However, in prior art methods, the 
sleeve is next cut into individual belt widths which are subsequently 
removed from the mandrel, separated and subjected to a series of 
manipulative steps which reduce the individual belts to the approximate 
contour of the mold in which the belts are to be cured. 
In accordance with the present invention, the belt sleeve is removed from 
the mandrel and transferred directly to the forming and curing apparatus. 
Referring now to the drawings, FIG. 1 shows a conventional rotary curing 
apparatus, of the type also described in U.S. Pat. No. 2,039,271, 
comprising a large vulcanizing cylinder 2, rotatable about a horizontal 
axis and heated internally by heating means, not shown, such as electrical 
resistance heaters; and externally by heating means 3, such as infrared 
heaters. The vulcanizing cylinder 2 cooperates with a tensioning roller 4 
that can be adjusted and locked in the direction in which the belt sleeve 
6 to be treated is tensioned. One or more belt sleeves 6 pass around the 
vulcanizing cylinder 2 and the roller 4. The vulcanizing cylinder 2 will 
be described in greater detail hereinafter. 
Also slowly passing around the vulcanizing cylinder 2 is pressure band 8, 
which can be tensioned by means of an adjustable roller 10. The band 8 is 
also led around guide rollers 12, mounted on pivotally connected arms 14, 
which are held together by a pair of straps 16. 
Referring now to FIG. 2, the vulcanizing cylinder 2 is provided with a 
plurality of axially spaced circumferential mold ribs 18 having belt 
element grooves 20 therebetween. Although trapezoidal shaped grooves are 
shown in FIG. 2, grooves which provide a "V" shape can also be provided. 
The belt sleeve 6, which comprises a compression section 22, a 
load-carrying section 24 longitudinally reinforced with at least one layer 
of helically wound cord 26 and a tension section 28, is positioned over 
the vulcanizing cylinder 2 in contact with the ribs 18. The belt sleeve 6 
is placed under tension by moving the tensioning roller 4 in a direction 
away from the vulcanizing cylinder 2. The tensioning roller can have a 
cylindrical surface, although it is presently preferred that the 
tensioning roller 4 be provided with mold ribs and belt element grooves 
corresponding in cross-section to the ribs 18 and grooves 20 in the 
vulcanizing cylinder 2. 
The belt 8 is then tensioned by means of adjustable roller 10 while 
rotating vulcanizing cylinder 2, thereby applying pressure to the outer 
tension section 28 of the belt sleeve 6. This pressure forces the 
compression section 22 into the grooves 20 of the vulcanizing cylinder 2, 
forming the belt elements, as shown in FIG. 3. 
During the forming step, the vulcanizing cylinder 2 is rotated at a rate of 
one revolution for every 15 to 30 minutes. The temperature of the 
vulcanizing cylinder 2 is elevated above ambient temperature during the 
forming step, and is sufficient to render the rubber of the compression 
section 22 moldable, but less than the temperature required to effect 
vulcanization of the sleeve 6. 
After the belt sleeve 6 has passed completely around the vulcanizing 
cylinder one time, the temperature of cylinder 2 is increased to 
vulcanizing temperature, and the sleeve 6, now having formed belt elements 
corresponding to the cross-section of the grooves 20, as shown in FIG. 3, 
is passed around the vulcanizing cylinder 2 a second time to effect 
vulcanization. This forms the completed V-ribbed belt. Upon completion of 
the vulcanization operation, the pressure band 8 is removed from the 
vulcanization cylinder 2. If desired, the completed belt can be removed 
from cylinder 2 by releasing tensioning roller 4. Alternatively, the 
completed belt can be cooled while mounted on the vulcanizing apparatus 
prior to removal therefrom. 
The term rubber, as used herein and in the claims, is intended to include 
any vulcanizable elastomeric material, natural or synthetic, normally used 
in building power transmission belt structures. 
The load-carrying cord 26 can be any suitable material known in the art, 
such as cotton, rayon, nylon, fiberglass, aramid, or the like, including 
blends and mixtures thereof. The load-carrying cord 26 can also be a 
polyester cord, in which case additional processing steps are required and 
which form a part of the present invention. 
In the case of a belt sleeve 6 having a polyester load-carrying cord 26, 
the desired belt element cross-section is formed, as described previously. 
At the end of the first cycle, i.e., the forming cycle, the sleeve is 
tensioned by means of tensioning roller 4 to a predetermined belt length 
and the vulcanizing cylinder 2 is heated to the desired vulcanizing 
temperature. The thus-formed belt is vulcanized, as previously described. 
Following the second cycle, i.e., the vulcanizing cycle, the vulcanized 
belt is subjected at least one additional cycle, preferably two additional 
cycles, at vulcanization temperature to stabilize the polyester cord. The 
pressure band 8 is then removed, tension is released and the completed 
belt is removed from the apparatus. 
The completed truncated V-ribbed belt made according to the above process 
is illustrated in FIG. 4, and is designated by reference number 32. The 
belt has at least 2 and preferably not greater than 5, trapezoidal shaped 
belt elements 30, also called truncated V-ribs. The belt 32 comprises 
load-carrying section 24 reinforced with cord 26, and tension section 28. 
In the embodimdent shown, the tension section includes a layer of 
elastomeric material in which are embedded laterally extending cords 34 in 
spaced substantially parallel relation along the endless path of the belt, 
with each of the cords 34 extending across the entire transverse dimension 
of the band 32. The cords 34 are of the type often referred to in the art 
as "tire cord". Such tire cord has relatively weak tie strands 36 holding 
the strength cords 34, substantially parallel. However, the tension 
section may incorporate bias laid woven fabric, "stress-relieved" fabric 
in which the warp and weft threads are at an angle of 95.degree. to 
155.degree. with each other; knitted fabric; or other fabrics employed as 
tension fabrics. In addition, other belt constructions may be utilized, 
such as placing a layer of fabric inwardly of the compression section 22, 
so that the fabric covers the rib portions or trapezoidal elements 30. 
FIG. 5 illustrates a further form of the invention in which the completed 
belt 40 has V-shaped ribs 54 instead of the truncated-V or trapezoidal 
shape of belt 32. The manufacturing process for this belt is the same as 
described above, except that the mold grooves are altered to achieve the 
V-shaped ribs. Belt 40 includes an outer tension section 42, which 
consists of an elastomer in which is embedded a fabric layer 44, 
illustrated as being a knit fabric. However, this fabric may be of the 
"tire cord" type shown in belt 32, bias woven, stress-relieved, or other 
known types. The belt 40 also comprises a strength section 46 having a 
longitudinally extending strength cord 48; a compression section 50 in the 
shape of V-ribs; and a cover fabric 52 which may be woven, knitted, or 
formed of special types of compounds. The fabric 52 may be omitted, as 
shown in FIG. 4. 
As indicated above, the completed belt sleeve 6 may be formed to provide a 
finished belt 32 or a belt 40, each having any desired number of ribs, but 
preferably between 2 and 5. However, such a sleeve may have more ribs than 
desired in a finished belt; for example, 10, 12 16, or more. In such a 
case, the completed sleeve may be cut into individual belts, such as 32 or 
40, having the number of ribs required. Thus, each sleeve provides a 
plurality of belts. 
Other forms of the invention are also contemplated as being within the 
scope of the inventive concept.