METHOD OF PRODUCING ENDLESS DRIVE BELTS

PROCEDE DE FABRICATION DE COURROIES DE COMMANDE SANS FIN

English Abstract

ABSTRACT
A method of producing endless drive belts of natural
or synthetic rubber with thread-like embedded strength
carriers of synthetic polymers which extend in, or essen-
tially in, the longitudinal direction. This method applies
especially to belts having longitudinal ribs upon the inner
periphery or circumference thereof. A raw belt is built
up in reversed layer sequence, is formed-out and vulcanized
in an outer or external form or mold, and is subsequently
turned or rolled over into the utilization condition of
the belt. The raw belt is built up with an outer diameter
corresponding to the smallest inner diameter of the outer
form or mold, is widened or expanded in the form or mold,
subject to plastic stretching of the strength carriers,
and then vulcanized, and is subsequently cooled off in
the stretched condition of the strength carriers.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PRO-
PERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing endless rubber drive belts,
defined as groove belts having longitudinal ribs exclusively
upon the inner periphery thereof, in external molds, said
belts having embedded therein thread-like strength cords
of synthetic polymers which extend continuously at least
essentially in the longitudinal direction of said belt, said
method including in combination the steps of:
building up a raw belt structure in upside-down position
by way of a reverse layer sequence from the outside to the in-
side, and with an outer diameter corresponding to the smallest
inner diameter of said external mold;
placing said raw belt structure in said external mold,
forming and enlarging said raw belt structure in said ex-
ternal mold by both expanding the diameter thereof while also
simultaneously subjecting said strength cords to plastic
stretching;
then vulcanizing said belt structure with thermal fixa-
tion of said strength cords maintaining at least partial
stretching after said vulcanizing;
subsequently cooling said belt structure in the stretched
condition of said strength cords; and
turning said belt structure over from upside-down posi-
tion for converting thereof into final finished condition for
use without necessity for costly multiple-part mold devices.

Description

23
~IETHOV OE PRODUCING ~NDLESS DRIVE BELTS
The presen~ invention relates ~o a method o~ producing
endless drive belts of natural or synthetic rubber wi~ch
thread~like embedcled strength carriers of synthetlc polymers
which extend in, or essen~îally in, the longitudinal direc~
tion. The invention relates especially to belts having longi-
tudinal ribs upon the inner periphery or circumference there~
of. A raw belt is built up in reverse layer se~uence (in-
verted), is fo~ned out and vlllcanized in an outer or ex-ternal
form or mold, and is subsec~uently rolled over or turned inside
out into the utiliz~tion condition of t~e belt,
In contrast to toothed belts, ~ich, because of tne trans-
versely arranged tooth configuration, are relatively easy to
pull off in the axial direction from the inner form or mold
core utilized or vulcaniæation, even in longer rolls or wind~
ings, and which therefore can be ~uilt up alxeady as a raw
belt in the condition of use with layer sequence advcmcing
from the inside to the outside7 the grooved belts, multiple
V-belts, and the like, embodied with longitudinally extending
ribbing, offer or encounter the problem of deformation or
~0 opening the mold without diameter expanslon and damaging . .
tears as a consequence thereof~ It has become customary to
counter these difficulties by building up the raw belts in
upside-do~n or inverse position, which rneans that the raw
belts are built up progressively in a reversed layer sequence
from the outside to the inside, and ~o subsequen~ly roll over
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the finished vulcanized belts (suitably aftex first cutting
the belts to their intended width), a procedure designated
in practice as "cardi-ng" (Krempeln) The forming-out of the
longitudinal ribs or grooves, and the vulcanizing, must in
this case be undertaken in an outer form or mold~ The fin-
ished belts can be withdrawn from such outer form without
special difficulties In contrast~ however, the intro-
duction or insertion of the prefabricated ra~ belts presents
a problematic situation
It is an object of the present invention to sîmplify
the introduction or insertion of the raw belts into the
outer form or mold, and to create the preconditions for
economical production o high-grade precision belts with
reduced waste~ scrap or rejected material which has to be
discarded.
By one aspect of this inventionJ a method is provided
for producing endless rubber drive belts, defined as groove
belts having longitudinal ribs exclusively upon the inner
periphery thereof, in external molds ? the belts havlng em-
bedded therein thread-like strength cords o synthetic poly-
mers which extend continuously at least essentially in the
longitudinal direction of ~he-belt, the method including
in combination the steps of building up a raw belt st.ruc-
ture in upside-down position by way of a reverse layer
sequence from the ou~side to the inside, and with an outer
diameter corresponding to the smallest inner diameter of
said external mold; placing the raw belt s-tructure in the
external mold; forming and enlarging .~he.raw belt structure
in the external mold by both expanding the diameter thereo~0 while also si~ultaneously subjecting .the strength cords to
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plastic stretching; then vulcanizing th~ belt structure
with thermal ~ixation of the strength cords maintaining
at least partial stretching after said vulcanizing; sub
sequently cooling the belt structure in the stretched con-
dition of the strength cords; and turning the belt struc-
ture over from upside-down~ position for converting thereof
into final finished condition for use without necessity
for costly multiple-part molcl devices.
The present invention avoids the otherwise necessary
constructive complexity of the segmented type of assembled
multiple part forms or molds in that the teaching of the
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present inven~ion utilizes sp~cial ~h~rm~c~ flxabl~ ex-
,~,~
pansion characteristics of synthetic fiber materials suchas7 ~or example, polyamide and polyester, for bringing about
the diameter changes. The xaw belts, first produced under-
size in comparison to the final finished condition thereof,
can be inserte~ or introduced directly in~o the vulcanizing
form or mold without further preparation or preliminary work.
Not only because of the widening or eæpanding, but also as
a result of the inEluence of heat and the complete formîng-
out of the raw belts within the form or mold, ~he strength
carriers experience or encounter a partial stretching ~t~h
s `~t~ ~
rP still in the plas~ic $~ . This partial stretching -`
is maintained over the duration of the vulcanization9 and
is fixed in the subsequent coollng-off phase. The cooling-
off is expediently undertaken as far as to below the so-
called softening or freezing temperature of the fiber
material, that is, to a temperature at which the adjusted
texture or ~rain structure is maintained subject to elim-
inating all mechanical stresses The Einished vulcanized
belts, ~herefore9 are removed from the form or mold with
~he accurate end measurement~ and, after cu~ting off from
the entire winding9 need only be cardefl or burred (krempelt).
The present in~ention is 7 0~ course~ in no way re-
stricted to the specific disclosure of the speci~ication~
but also encompasses any modi~ications within the scope o~
the appended claims.
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