Note: Descriptions are shown in the official language in which they were submitted.
21492702
The present invention pertains to a process for retreading a
used tire, whereby the running surface of the tire is ground
off and/or roughened, a layer of a binder rubber is applied
to the surface of the tire, a closed ring of a new running
tread is applied onto the binder rubber, the air is removed
between the binder rubber and the running tread, and the
running tread is connected to the tire by vulcanizing the
binder rubber disposed between the tread and the tire.
It has been known heretofore to make used tires of motor
vehicles available for further use in that a new running
tread is applied onto their surface. This is based on the
premise that the use of tires causes the running tread to be
removed by way of friction, so that they do no longer provide
the necessary profile, while the fabric carrying the running
tread, the so-called carcass, remains undamaged. When, at
that point, a new running tread is applied onto the undamaged
carcass of a vehicle tire, a tire is created which fully
meets the traffic-technological requirements.
The mounting of a new running tread onto a used tire, which
is referred to a retreading, is particularly economical with
large diameter tires. These are tires for trucks, propelled
machines, such as earth movers, excavating machines, planing
vehicles, and the like.
2149270 3
Retreading of vehicle tires is effected in that a used tire
is ground down and/or roughened. Subsequently, a rubber
solution is sprayed onto the surface of the tire, and a layer
of a binder rubber, which is necessary for vulcanization, is
applied thereon. It is thereby necessary to guard against the
inclusion of air pockets between the surface of the tire and
the binder rubber. This is assured in that the layer of the
binder rubber is rolled thereon.
Subsequently, a closed ring of a new running tread is aplied
onto the tire. This is effected in that the annular running
tread is radially stretched with a pulling device, which is
provided with gripper arms, enough as to allow the tread to
be placed over the tire provided with the binder rubber. Then
the gripper arms of the pulling device are laterally pulled
from between the tire and the annular running tread, whereby
the running tread comes to lie on the surface of the tire and
tightly enclose the tire. In the further sequence, the tire
provided with the new running tread is exposed in an
autoclave to a pressure of about 5 bar and a temperature of
about 100C, which causes the binder rubber to vulcanize. The
new running tread is thereby permanently attached to the
carcass of the used tire.
An essential requirement for attaining the necessary
connection of the new running tread with the carcass is that
no air pockets remain between the binder rubber and the
~ -- 21~9270 4
annular running tread, because otherwise no connection would
be effected between the running tread and the carcass in the
area of the air pockets. In efforts to avoid such air
inclusions, due to which retreaded tires do not meet the
traffic-technological requirements, several measures have
been proposed heretofore.
It is known from AT-PS 305 061, from AT-PS 353 119, and from
AT-PS 357 423 to enclose the tire provided with the running
tread partly or entirely with an elastic, air-tightly closed
sleeve, and to evacuate the inside of the sleeve before and
during the vulcanization process. The difficulty arises
thereby, however, that the air pressure existing on the
outside of the sleeve presses the wedge-shaped lateral edges
of the running tread onto the side flanks of the tire so
strongly as to cause an airtight closure, so that in spite of
the vacuum existing in the sleeve, air enclosures between the
running tread and the tires are not removed. Additionally,
that process requires a sleeve formed of a rubber-type
material to enclose the tire at least partially, which sleeve
is also subject to heating in the autoclave and thus to such
stresses so as to make it suitable for only a limited number
of uses. Because the sleeve becomes frail and air-permeable,
air may pass through during the vulcanization process and in
between the carcass and the running tread, which may also
cause faults in the retreading. The fact that the retreading
of tires with large diameters necessitates correspondingly
2149270 5
large sleeves causes great material requirements, wherein
that process is also not economical.
It is further known from AT-PS 353 119 to form the inner
surface of the running tread with a plurality of channels,
through which air can be aspirated from between the running
tread and the tire. This too, however, requires a sleeve
enclosing the tire fully and air-tightly, which sleeve is
suitable for only a few assignments.
Furthermore, it is known from AT-PS 296 799 to mount the
annular running tread onto the tire within an evacuated
container. The tire is inserted into the container for that
purpose, the running tread is disposed radially near the
tire, and the container is subsequently closed and evacuated.
Only then is the running tread placed on the tire. In this,
air enclosures between the tire and the running tread are
safely avoided. That process brings with it the disadvantage
of great technical expense, in that it requires an evacuated
container with a stretching device.
The present invention is therefore based on the object to
provide a process which avoids the disadvantages associated
with the prior state of the art. This is attained in
accordance with the invention in that a plurality of mutually
interconnected channels are provided between the binder
rubber and the inside surface of the annular running tread,
2149270 6
which channels terminate at a distance from the lateral edges
of the running tread and which communicate with at least one
opening extending through the running tread, in that after
the running tread has been placed on the tire the lateral
edges of the running tread are air-tightly connected with the
sidewalls of the tire by vulcanizing the binder rubber
located there, in that the air located between the remaining
running tread and the binder rubber is subsequently aspirated
off through at least one opening in the running tread and
that thereafter the remaining running tread is attached to
the tire by vulcanizing the binder rubber located between the
running tread and the tire.
The process according to the invention is based on the
premise that that function which is satisfied in the prior
art with the tire-enclosing sleeve, can be satisfied by the
annular running tread itself, as long as the same is
air-tightly connected with the tire along its lateral edges.
Due to the fact that, in accordance with the invention, air
enclosures located between the tire and the running tread can
be removed through an opening extening through the running
tread, the use of a sleeve can be done away with, whereby the
disadvantages associated with the sleeve are avoided. Since
further a plurality of mutually interconnected channels are
provided between the running tread and the tire, any air
enclosures are dependably removed, whereby this process
2149270 7
avoids all of the disadvantages associated with the prior art
processes.
On the inside surface of the running tread there are
preferably provided a plurality of mutually interconnecting
channels, which terminate at a distance from the lateral
edges of the running tread, and which are particularly formed
as mutually crossing, web-like channels.
Analogously, a plurality of mutually interconnected channels
may be located at the upper surface of the binder rubber
applied on the tire. They can thereby be produced in that a
first layer of binder rubber is applied on the tire, onto
which a second layer of preferably strip-shaped sections of
the binder rubber are applied, whereby channels are disposed
between the sections. The first layer of the binder rubber
can thereby be plate-shaped and the second layer of the
binder rubber can be formed by strips, which are applied on
the first layer in the form of a multiply interrupted spiral.
Furthermore, the inside surface of the running tread is
preferably formed with at least one transversely extending
channel from which the opening extending through the running
tread originates. In accordance with a preferred embodiment,
the tire with the running tread is inserted into an autoclave
and the evacuation of the air from between the running tread
2149270 8
and the binder rubber continues during the vulcanizing
process in the autoclave.
The process according to the invention is explained in more
detail in the following with the aid of the exemplary
embodiments illustrated in the drawing. There is shown:
ig. 1 a running tread for use with the process according
to the invention, in an axonometric view,
Fig. la a section of the running tread according to Fig.
1, in an axonometric view and in section,
Figs. 2 and 2a two embodiments of a tire coated with a
binder rubber, in section,
Fig. 3 a tire with a running tread, in a first stage of
the process according to the invention, in section,
Fig. 4 the tire with the running tread according to Fig. 4
in a second stage of the process according to the
invention, in section, and
Fig. 5 an autoclave with a tire disposed therein, in
section.
As illustrated in Figs. 1 and la, a running tread 1 which is
provided for retreading a used and ground-off tire, is formed
as a closed ring, which is provided on its outside with a
profile tread in the form of a plurality of tread bumps 11
and on its inside with a plurality of mutually criss-crossing
and thus web-like converging channels 12. The channels 12
2149270 9
thereby end at a distance from the two lateral edges 13 of
the running tread 1, thus forming strips along the lateral
edges 13, which have a plane surface.
Fig. 2 further illustrates a tire 2, which is mounted on a
wheel 4. A layer 3 of a binder rubber is disposed on the
ground-off and roughened surface of the tire 2. Because the
layer 3 has been rolled onto the tire 2, air pockets are
avoided. As further seen from Fig. 2, the running tread 1 is
formed with at least one through-opening 14, which leads to
the channels 12 on the inside surface.
Fig. 2a illustrates an embodiment in which the inside surface
of the tire tread 1 is formed without mutually converging
channels. Instead, two layers 31 and 32 of binder rubber 3
are applied on the tire 2, whereby the first layer 31, which
lies on the upper side of the tire 2, extends through, while
the layer 32 disposed thereon is formed of a plurality of
mutually spaced-apart strips 32, which extend spirally about
the tire 2, thus forming channels 33 therebetween. The
opening 14 extending through the running tread 1 thereby
opens into a single channel 12a extending transversely at the
inside surface of the running tread 1, which channel 12a also
ends at a distance from the lateral edges 13 of the running
tread 1.
2149270 lO
As can be seen from Fig. 3, the running tread 1 is applied
onto the tire 2, whereby air enclosures 5 are located between
the tire 2 and the running tread 1. The lateral edges 13 are
subsequently air-tightly connected with the sidewalls of the
tire 2 by vulcanizing the intermediately located binder
rubber with annular heating devices 6, through which hot gas
flows, for instance. Then, as illustrated in Fig. 4, the air
which is located between the running tread 1 and the tire 2
is aspirated via a suction line 7, which communicates with an
evacuating device. Due to the fact that the lateral edges 13
of the running tread 1 are air-tightly connected with the
tire, no air can follow along that path. Due to the fact that
furthermore a plurality of channels 12 are located between
the running tread 1 and the tire 2, any air enclosures
between the running tread 1 and the tire 2 are removed by the
evacuation process.
The tire 2 is subsequenly inserted into an autoclave 8, in
which the entire binder rubber 3 disposed between the running
tread 1 and the tire 2 is vulcanized, whereby the running
tread 1 is attached to the tire 2. Because the suction line 7
leading to the evacuation device extends through the wall of
the autoclave 8, the evacuation may be continued during the
vulcanization process.
For the applicant
6.12.1994 Patent Attorney
