Method for bonding a carcass for a tubed tire with a belt band

A method and apparatus for bonding a carcass for a tubed tire with a belt band that protects the radially inner side of the tire. The bonding surface is coated with a rubber solution, the belt band is placed thereon, and the bonding zone of tire and belt band is vulcanized. To achieve an increased resistance to separation between a biased carcass and a belt band, the zenith portion of the tire is reinforced with additional or overlapping plies in such a way that the rigidity of the outer half in the circumferential direction is greater than that of the inner half. While avoiding high speed accelerators, the rubber solution is provided with such a quantity of polymerizing agent that at the selected vulcanization temperature a vulcanizing time of between a third of a minute and ten minutes results. The tire, which is provided with the belt band and is in a position of use, is disposed onto a ring that is provided with a circumferential trough and is heated. The tire is inflated to shrink its circumference and to compress the bond that is to be vulcanized with the belt band.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and apparatus for bonding a 
carcass for a tubed tire with a belt band that protects the radially inner 
side of the tubed tire, with the method including coating the bonding 
surface with a rubber solution, placing the belt band thereon, and 
subsequently vulcanizing the bonding zone of tubed tire and belt band. 
A natural rubber solution is generally used as the rubber solution. In this 
connection, the bonding surface of not only the carcass but also of the 
belt band itself that is to be placed thereagainst is coated six to twenty 
times, depending upon the embodiment. After the bonding surface has been 
made tacky in this manner, the belt band is pressed for a short period of 
time against the carcass. The vulcanization is effected at room 
temperature, and requires approximately three weeks to three months. Thus, 
the predominant portion of the polymerization is achieved during a free or 
natural vulcanization. 
In addition to the very long vulcanization time, the heretofore known 
method has the drawback that the belt band, which is intended to protect 
the tubed tire from wear resulting from the rim, is not seated securely 
enough on the carcass to reliably prevent separation of the belt band 
during high stress, as occasionally occurs, for example, during bicycle 
races. 
It is therefore an object of the present invention to provide a method for 
bonding a tubed tire carcass with a belt band that provides a considerably 
greater resistance to separation between the belt band and the carcass.

SUMMARY OF THE INVENTION 
The method of the present invention includes the steps of: reinforcing the 
zenith portion of the tubed tire with additional or overlapping plies in 
such a way that the rigidity of the outer half in the circumferential 
direction is greater than the rigidity of the inner half; providing the 
rubber solution, while avoiding high speed accelerators, with such a 
quantity of polymerizing agent that at a selected vulcanization 
temperature a vulcanizing time results that is between a third of a minute 
and ten minutes; disposing the tubed tire, which is provided with the belt 
band and is in a position of use, onto a ring that is provided with a 
circumferential trough and is heated; and inflating the tubed tire to 
shrink its circumference and to compress the bond that is to be vulcanized 
with the belt band. 
Due to the fact that the pressure is maintained during the entire 
vulcanization time, a higher degree of polymerization, and a considerably 
higher resistance against separation, are achieved. Pursuant to the 
present invention, in order to build up pressure in the bonding surface it 
is not necessary to have an outer ring that resembles the rim-like heating 
ring; rather, the biased carcass, by being inflated, is itself the 
pressing mechanism. This is accomplished due to the phenomenon that the 
biased carcass for tubed tires, due to its subcritical thread angle 
(40.degree. to 45.degree.), has its inner diameter reduced as the pressure 
is increase. The simultaneous use of the workpiece carcass as a tool 
mechanism saves not only the cost for an outer ring, but also makes it 
possible to have a particularly uniform distribution of pressure over the 
periphery. 
The profile of a tubed tire exhibits a nonuniform distribution of rigidity. 
The seam which is generally disposed on the inner side, and which is 
closed after introduction of the airtight tube, has a greater rigidity 
than the surrounding non-seamed carcass zones due to the folded-over 
carcass portions that are required to form the seam. Pursuant to the first 
characteristic of the inventive method, the tubed tire is reinforced 
radially outwardly at least to such an extent that its outer half, in the 
circumferential direction, is slightly more rigid than is its inner half. 
As a result, the phenomenon observed with most tubed tires, namely that 
during shrinkage or contraction the tubed tire twists, is avoided. This 
results in a more reliable seating of the tire in the heating ring. 
The tubed tire is preferably first forced into such a transposed position 
that that side that in the position of use is disposed inwardly, is 
disposed outwardly. In this inverted position, after the bonding surface 
is made tacky, the belt band is placed thereon. The tire is then again 
placed in its position of use and is disposed on the heating ring. The 
heating ring and its trough, onto which the tubed tire is disposed, is 
preferably heated to a temperature of between 120.degree. and 210.degree. 
C. 
For this purpose, the heating ring preferably has a hollow chamber. 
Utilizing this hollow chamber, the ring can be heated by conveying a gas 
or a hot liquid through the hollow chamber, or by disposing electrical 
heating elements in the hollow chamber. Considerably shorter vulcanization 
times are achieved due to the fact that the vulcanization is now effected 
at considerably higher temperatures than the room temperature that was up 
to now used for this purpose. These short vulcanization times make it 
possible for the first time to keep the bonding surface under pressure 
during the entire vulcanization time, which has been shortened from the 
previous length of several months to a time interval that is measured in 
just a few minutes; this pressure is in contrast to the essentially 
natural vulcanization of the heretofore known method. Pursuant to the 
present invention, the high speed accelerator, for example thiuram or 
dithiocarbamate, which is extremely toxic due to the release of 
nitrosoamine, is unnecessary. 
Pursuant to the present invention, the bonding surface between the belt 
band and the tubed tire carcass is preferably coated only one time with 
rubber solution prior to the placement of the belt band thereon. 
Advantageously both the bonding surface on the side of the carcass as well 
as the bonding surface on the side of the belt band are coated one time. 
This one-time coating is sufficient because due to the reliable 
application of pressure, the rubber solution per application can be coated 
considerably thicker than was previously known in the state of the art. As 
a result of coating both the carcass and the belt band one time, a 
particularly good initial tackiness is achieved that facilitates the 
manufacture. 
The heated ring on which the tubed tire that is provided with the belt band 
is to be heated up, is advantageously disposed essentially horizontally. 
The lowermost of the two flanges that delimit the trough of the ring 
preferably has a greater outer diameter than does the upper flange. This 
larger lower flange prevents the tire from falling through in a downward 
direction and at the same time serves as a centering aid. This arrangement 
permits the tubed tire to be mounted particularly rapidly on the ring, and 
prevents localized overheating. 
It is particularly advantageous to provide a somewhat hotter location on 
the heating ring, and to position the tubed tire valve at this location. 
The increased heat requirement at this location is then completely 
compensated for by the increased temperature, and provides a uniform 
degree of vulcanization over the periphery. If the heating ring is to be 
heated by conveying a hot medium therethrough, the hottest location is 
disposed in the vicinity of the inlet of the heating medium. Thus, the 
tubed tire valve should be positioned at this location. 
As indicated previously, most tubed tires have a seam. This seam involves a 
widened portion. In order nonetheless to achieve a uniform pressure 
against the belt band that is to be bonded, it is proposed pursuant to the 
present invention that the heated ring, which has a trough that is 
delimited by two flanges, be provided at the deepest location of the 
trough with a narrow groove for receiving the carcass seam and the 
folded-over portions of the tubed tire that are necessary for forming the 
seam. 
It is to be understood that the transverse radius of curvature of the 
trough in the heating ring should correspond approximately to the 
transverse radius of the tubed tire that is to be treated. In order to 
achieve a particularly high pressure against the edges of the belt band, 
which are particularly subjected to the danger of separation, it is 
advisable that the transverse radius of the groove be slightly less than 
the transverse radius of the tubed tire, preferably being 92 to 98% 
thereof. 
Further specific features of the present invention will be described in 
detail subsequently. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawing in detail, shown is a heated ring 1 onto which 
the tubed tire 2 is to be disposed, via the axial movement indicated by 
the arrow 4, for the vulcanization of the bond with the belt band 3. 
The tubed tire is illustrated in only a very diagrammatic manner, showing 
its two-ply biased carcass 5 which, after the introduction of a 
nonillustrated tube, is closed off radially inwardly, accompanied by the 
formation of folded-over portions 6, via a seam 7. The thread angles in 
the carcass plies are 43.degree., so that with an increase in the 
inflation pressure, the inner radius R.sub.i of the tubed tire is reduced. 
Provided in the zenith portion between the tread strip 8 and the carcass 5 
is a two-ply, belt-like reinforcing strip 9. This reinforcing strip serves 
not only to increase the resistance against penetration, i.e. a reduction 
of the risk of a blowout or flat tire, but also affects the rigidity 
distribution such that the radially outer half is more rigid in the 
circumferential direction than is the inner half. 
The heated ring 1 is provided with a trough 10 that is delimited at the top 
by a flange 11 of maximum radius R.sub.o, and is delimited at the bottom 
by a larger flange 12 of maximum radius R.sub.u, with R.sub.o being 
slightly greater than R.sub.i, so that the tubed tire 2 "snaps" into 
position in the trough 10. The larger flange 12 has a conical 
configuration, prevents the tubed tire 2 from falling through toward the 
bottom, and facilitates orientation of the tire 2 on the heated ring 1. At 
its deepest location, the trough 10 is provided with a circumferential 
groove 13 for accommodating the seam 7 and the folded-over portions 6 of 
the carcass 5 of the tubed tire 2. This permits the belt band 3 to be 
pressed particularly uniformly against the inner side of the tire 2. For 
most applications, it is expedient for the belt band to contain 
load-carrying cords in a known manner; however, this is not absolutely 
necessary. 
The rim-like heating ring 1 is provided with a hollow chamber 14 via which 
the ring is heated. The configuration shown in the illustrated embodiment 
is based on heating the ring by conveying steam therethrough. It is to be 
understood that other heating principles could also be utilized. 
The invention provides an improved method for heating belt bands on tubed 
tires. In addition, the present invention discloses a suitable apparatus 
for carrying out this method. While providing for a rapid production 
sequence, the inventive method provides for an increased resistance to 
separation between the biased carcass and the belt band. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawing, but also encompasses any 
modifications within the scope of the appended claims.