Power transmission belt

An elastomeric or plastomeric power transmission belt is reinforced with longitudinally extending wires or threads which are flexible and substantially inextensible. Longitudinally uniformly spaced rigid members which are embedded cross-wise in the belt with one surface adjacent to the longitudinally extending reinforcing members support the wires or threads during vulcanization or curing of the elastomer or plastomer and resist transversal deformation of the belt during use.

The present invention relates to a power transmission belt and, in 
particular, to a V-belt adapted for use in speed variators. 
Power transmission belts having a V-shaped cross-section for transmitting 
mechanical power are known. These known belts have an elastomeric body 
reinforced with a longitudinally extending resistant insert member of a 
plurality of small threads of a flexible and inextensible material. The 
threads all lie in the same plane and are parallel to one another. These 
known belts may or may not have a covering of rubberized fabric which 
resists wear. The prior art belts have several disadvantages, one of which 
is that they have low yield in transmitting power from one pulley to 
another. 
As a matter of fact, a good part of the power transmitted by the known 
V-belts is dissipated by the belts due to hysteresis losses that the 
elastomeric material has because of repeated deformations as it rotates 
around the pulleys. Moreover, such belts absorb large amounts of power 
because of the inertia due to their heavy construction. Also, the known 
belts are not sufficiently rigid transversely to prevent transversal 
deformations. As a consequence of this, in addition to not being capable 
of guaranteeing a constant transmission ratio as time passes, the 
transverse deformation results in "sliding" of the belt in the pulley 
groove which reduces the efficiency of the power transmission. Moreover, 
such transversal deformation results in additional absorption of power and 
causes overheating of the belt body which reduces its resistance to 
fatigue. 
An object of the present invention is to overcome the above-described 
drawbacks of the V-belts, and in particular, to provide a belt having a 
V-shaped cross-section for transmitting mechanical power which efficiently 
transmits power at a constant transmission ratio as time passes and has a 
longer life-time than the prior art V-belts. 
Another object of the invention is to provide a power transmission belt 
having a V-shaped cross-section capable of transmitting greater power over 
a lifetime at least as long as the lifetime of the prior art V-shaped 
belts.

The foregoing objects and others are accomplished in accordance with the 
invention by providing a power-transmission belt having an elastomeric or 
plastomeric body of a V-shaped cross-section, a plurality of elongated 
tension resistant members embedded in and extending longitudinally through 
the body and disposed coplanar and substantially parallel to one another, 
and, also embedded in the belt body, substantially uniformly 
longitudinally spaced rigid members disposed across the width of the body 
which resist transversal deformation of the belt body and have one surface 
thereof supporting the elongated longitudinally extending insert members 
whereby the elongated longitudinally extending insert members are 
supported during the vulcanization or curing of the belt and the belt body 
already vulcanized is made resistant to transverse deformation during use. 
The longitudinally extending insert members may be wires or flexible and 
substantially inextensible threads. 
Thus, in its broadest aspects, the invention contemplates broadly a belt 
for power transmission having an elastomeric or plastomeric body of 
V-shaped cross-section, an insert member formed by a plurality of threads 
of a flexible but inextensible material which are coplanar and parallel to 
one another and resist tensioning of the belt, and a plurality of 
transverse rigid insert members which are embedded and distributed at 
substantially regular intervals along the entire development of the belt 
body with one surface of each of the rigid insert members being in contact 
with the longitudinally extending reinforcing members. The longitudinally 
extending insert members are flexible but substantially inextensible. 
One surface of each of the rigid insert members is disposed in contact with 
the longitudinally extending insert members. The surface of the rigid 
insert members which is in contact with the longitudinally extending 
insert member is disposed transversely across the width of the belt and 
preferably lies in correspondence of the thrust-center for the 
longitudinal tangential forces acting upon the side-edges of the belt. The 
thrust-center for the longitudinal tangential forces acting upon the 
side-edges of the belt is the particular place where the sum total of all 
the longitudinal tangential forces resulting from engagement of the belt 
with the pulley is applied. As is the case for practically all known 
V-belts, also for the belt according to the invention, the elongated 
longitudinally extending insert member is positioned near the neutral axis 
in all sections that are perpendicular to the greater dimension of the 
belt. 
In FIG. 1, a belt 1 having a V-shaped cross-section has an elastomeric body 
2 in which is embedded an insert member 3 formed of a plurality of threads 
3' which are coplanar and parallel to one another. Threads 3' are of a 
flexible and inextensible material such as, for example, steel, nylon, 
glass-fibers, polyamide or aramide, polyester, rayon or the like. In the 
body 2 of elastomeric or plastomeric material moreover, are embedded, 
according to the present invention, a plurality of rigid members 4, each 
having a "H" form, and distributed at substantially regular intervals 
along the entire length of the V-belt 1. The transverse tracts 5 of 
members 4 are in contact with the threads 3' of the resistant insert 
member 3. The contact takes place on the upper part of the transverse 
tracts 5 (as shown in FIG. 1) or else in the lower part of the transverse 
tracts 5. 
Reinforcing members 4 are metal. Alternatively, members 4 may be any other 
rigid material capable of resisting without deformation the temperature 
required for vulcanizing the belt 1. 
FIG. 2 shows another embodiment of a V-belt 6, according to the present 
invention. V-belt 6 is quite similar in its internal structure, to the 
V-belt 1 illustrated in FIG. 1. 
The sole difference is that a longitudinally extending continuous groove 9 
is provided in the major base 7 and a similar groove 10 is provided in the 
minor base 8. 
In other embodiments of the belt only one of grooves 9 and 10 may be 
provided. 
In other embodiments of the invention which are not illustrated in the 
drawing, the insert members 4 are placed upsidedown in belts like 1 and 6 
of FIGS. 1 and 2 so that the free extremities 4' are near the major base 
7, of the V-belt. 
Modifications of the belts of FIGS. 1 and 2 are illustrated in FIGS. 3 and 
4. These two modifications are distinguished from those of FIGS. 1 and 2 
by their height, i.e. the distance between the major and the minor bases 
is reduced. 
For the V-belts of FIGS. 3 and 4, the transverse tract traced by the insert 
members 4 (the form of which shall be described later on, in more detail), 
practically lies in correspondence with the thrust-center of the 
longitudinal transverse forces previously defined. Because, the height of 
the V-belts is reduced, the difference between the theoretical position 
(i.e. the position in correspondence with the thrust-center of the 
longitudinal tangential forces), and the effective position, is 
negligible. 
Even in the case of these V-belts, the resistant insert member 3 lies along 
the neutral axis of the belt. 
In FIGS. 3 and 4, two V-belts 11 and 12, respectively, are shown in 
cross-section and in perspective. Belts 11 and 12 have a body 13 of 
elastomeric or plastomeric material and a resistant insert member 14 
formed by a plurality of threads 14' coplanar and parallel to one another 
embedded in body 13. Threads 14' are nylon. They may be of any of the 
other materials listed for belt 1 of FIG. 1. The transverse reinforcing 
members 15 embedded and distributed at substantially equal intervals in 
elastomeric body 13 having an U-shaped form are of metal or other rigid 
material mentioned before in the description of the belt in FIG. 1. In 
particular in the V-belt 11 of FIG. 3, members 15 are disposed with their 
transverse tracts 16 along the minor base 17 of V-belt 11, while the 
larger base 18 contains a continuous longitudinal groove 19. On V-belt 12 
(represented in FIG. 4) on the other hand, members 15 are disposed with 
their transverse tracts 16 along the larger base 18 of V-belt 12, while 
the smaller base 17 contains the continuous longitudinal groove 19. 
According to another embodiment of the invention, a belt (not illustrated) 
having the same characteristics of the belts 11 and 12 (represented 
respectively in the FIGS. 3 and 4) differs from belts 11 and 12 only by 
being devoid of a continuous longitudinal groove 19. 
In both of the embodiments illustrated in FIGS. 3 and 4, the transverse 
tract 16 of the members 15 is in contact with the threads 14' of the 
longitudinal resistant insert member 14, along the upper surface of the 
transverse tract 16. As an alternative, the transverse tracts 16 of 
members 15 are in contact with the threads 14', along the lower surface of 
the transverse tract 16. 
In FIG. 5, a length of another embodiment of a V-belt 20 is illustrated in 
a side elevation. V-belt 20 has a resistant insert member 21 and 
reinforcing members 23 embedded in the body 22 of elastomeric or 
plastomeric material. In particular, the resistant member 21 are in 
contact with the part of the reinforcing members 23 that are parallel to 
the bases of the V-belt. 
The V-belt 20 has moreover, transverse incisions 24 which extend from the 
smaller base substantially up to the resistant insert members 21 without, 
however, touching it. Transverse incisions 24 are regularly interposed 
with the members 23 that are embedded in the body 22 (as is clearly shown 
in said FIG. 5). However, (although not represented in FIG. 5) there may 
also be present in the body 22 of the V-belt 20, instead of the transverse 
incisions 24 or along with them, other transverse incisions that are 
similar to the transverse incisions 24, which however, depart from the 
larger base and extend substantially up to the resistant insert member 21, 
without however, touching it. The form of the incisions 24 present in the 
body of the belt of FIG. 5 is not critical. Such incisions may be of any 
other geometrical form provided that the desired form does not interfere 
with either the resistant insert members 21 or the members 23. The 
transverse incisions 24 can be present in any of the embodiments of the 
invention. 
The power transmission belts provided by the invention may or may not be 
covered either totally or just partially such as, for instance, only on 
the working surface, with one or more layers of conventional protective 
covering material. 
The covering may be, for example, two layers of a rubberized fabric whose 
wefts and warps are crossed one with respect to the other, and, in 
particular, a fabric in which the wefts and warps are inclined at an angle 
of 45.degree. with respect to the longitudinal symmetrical plane of the 
belt. However, since the wefts and warps of each layer are inclined 
towards opposite sides, the wefts and warps of the two layers of 
rubberized fabrics are substantially perpendicular to each other. 
Moreover, solely by way of example, the belt body may be made of 
elastomeric material having the following composition. Such a belt body 
maintains its rubber-metal connection even during fatigue operations. 
______________________________________ 
Natural rubber 100 parts by weight 
large particle from 50-100 parts 
carbon-black by weight 
zinc-oxide 5 parts by weight 
stearic acid 2 parts by weight 
sulphur 2.5 parts by weight 
accelerators 1 to 2 parts by weight 
anti-ageing 1 to 2 parts by weight 
______________________________________ 
It is apparent that the objects of the invention are achieved. In fact, the 
V-belts provided by the present invention have substantial transverse 
rigidity that allows them to transmit substantial power, with a constant 
transmission ratio as time passes, because the rigid members embedded in 
the V-belts prevent any reduction in the cross-section of the belt and as 
a consequence impede wedging of the belt in the pulley grooves, as 
normally occurs in the known V-belts. Moreover, the V-belts provided by 
the present invention are considerably lighter in weight both because of 
the presence of the longitudinal grooves and of the presence of the 
transverse incisions. But the reduction in weight alone is not the main 
reason for the greater efficiency in power transmissions. The amount of 
power absorbed by the belt because of hysteresis losses caused by 
deformation as the belts traverse the pulley is greatly reduced by the 
reduction in elastomeric material because of the longitudinal grooves and 
where the transverse incisions are present. This reduction in the energy 
absorbed and dissipated through the hysteresis losses causes the total 
power transmitted by the V-belt of the invention to be higher than the 
power transmitted with the heretofore available V-belt. This helps the 
yield of power transmission to be higher than with a V-belt of the known 
type. Moreover, the employment of individual rigid transverse reinforcing 
members separated from one another provides greater longitudinal 
flexibility when compared to that of the known V-belts. Finally, since the 
threads of the longitudinal resistant insert member are in contact with 
the horizontal transverse tract of the spaced insert members the threads 
of the longitudinal insert remain aligned and coplanar and parallel to one 
another during manufacture and use exactly in their predetermined 
position, i.e. with respect to the neutral axis of the belt. 
As a direct consequence of the improvements with which the V-belts, 
according to the present invention, are furnished, it results that the 
belts can transmit greater power if their lifetime remains the same as 
that of known V-belts, or if the power transmitted is the same as that of 
known V-belts, the V-belts according to the present invention have a 
longer lifetime. 
In addition to the particular forms described and represented in the 
drawing for the longitudinally spaced insert members, it is to be 
understood that members of other shapes may be used provided that they are 
appropriate to the mechanical purpose so as to guarantee both the 
transverse rigidity of the V-belt and a suitable supporting surface for 
the threads of the resistant insert. 
Although the invention has been described in detail for the purpose of 
illustration, it is to be understood that such detail is solely for that 
purpose and that variations can be made therein by those skilled in the 
art without departing from the spirit and scope of the invention except as 
it may be limited by the claims.