Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to a method of repairing
vehicle tyres and is a division of Canadian application
No 244,973, filed on June 30, 1976.
As regards retreading me-thods which are concerned
here, a layer of vulcanizable rubber, called binding rubber,
is laid on a prepared retread on repair region of the tyre
carcass and thereafter a vulcanized tread strip in the form
of a ring, a strip section or in the form of separate elements
adjoining one another is placed thereon, with subse~uent
sealing of this layer formation. At least the lateral outlet
points of the binding rubber are sealed of, for example, by
means of a flexible rubber covering of the tyre, at least
in the region of the lateral outlet points of the binding
rubber. Any occlusions of air or gas are now removed from the
binding rubber region by using reduced pressure and/or excess
pressure on the binding rubber region, and in the event of a
casing or sleeve being used, by suitable application of reduced
pressure and/or excess pressure to these latter. Then follows
a treatment of the tyre as thus prepared in the autoclave,
using pressure and heat, for the purpose of vulcanizing the
binding rubber layer, which firmly unites the tread strip with
the carcass in the vulcanized state.
With repairs to tyres having damaged positions, the
procedure is similar, in that the vulcanizable rubber and other
repair material are applied in the region of the damaged
position on the tyre carcass, with subsequent sealing of the
point of repair, for example, by covering the latter by
means of a piece of a flexible rubber sleeve or cover which
can be sealed off at its edge completely around the carcass.
In this case also, reduced pressure and/or excess pressure
is applied to-the b~nding rubber region for the purpose of
removing gas occlusions, whereafter the vulcanization of the
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binding rubber takes place as previously explained.
In both cases, reduced pressure or vacuum is usually
exerted through a hose connection on the sleeve, cover or
sheathing on the region beneath the latter. Vacuum connections
with a corresponding screw coupling on the sheathing, however,
generally project outwardly and consequently are capable of
being easily damaged. In addition, the hose coupling interferes
with the work carried out on the tyre, for example, the insertion
of the completely prepared tyre in the autoclave. The vacuum
effect is not always uniform. The region of the binding rubber
which is in the vicinity of the hose connection is frequently
exposed to a higher vacuum than other regions, to which the
access can be obstructed, for example, by the binding rubber in
this case acting as an undesired seal and blocking the dis-
charge of air.
Consequently, the object is to simplify the use of
vacuum in connection with repair operations.
Accordingly, the invention herein claimed is a method
for repairing a vehicle tyre comprising the steps of: providing
a repair region of the tyre with rubber material to be bonded
to the tyre by vulcanization, applying a flexible cover to the
region provided with the said rubber material, attaching the
flexible cover to the tyre with an adhesive that can withstand the
vulcanization temperature of the rubber filling around the border
of the flexible cover to provide a seal between the flexible
cover and the tyre, piercing the flexible cover with a hollow
suction needle at at least one point over the repair region where
air or other vapour has accumulated within the repair region,
evacuating the air or other gas or vapour from the repair
region at each of said points by applying a suction through
the needle, removing the needle from the flexible covering at
each of said points after the air or other gas or vapour has
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been evacuated, sealing off the puncture opening in the flexible
cover made by the needle at each of said points, and heating
the repair region to vulcanize and bind the rubber filling to
the tyre.
This salution permits avoiding the use of any fixed
vacuum connections when employing a cover or sheathing. Instead,
a sharpened hollow needle or one which is oblique or comes
to a point at the forward end is used for penetrating into
the cover, said needle being connected to a vacuum line.
If, when making repairs of damage and position , the
repair point is prepared as indicated above, covered with a
flexible piece of sheathing and the latter is itself sealed
off on the carcass, it now only requires the use of the
hollow needle, with which the cover is punctured at a position
which depends on the size of place being repaired, whereafter
a valve in the vacuum line is opened, so that it becomes
possible for all air and gas occlusions to be removed by
suction from the region beneath the cover and also from the
surroundings of the raw rubber by means o the hollow needle.
After the suction has been completed, the perforation is
sealed, preferably by sticking binding rubber on the said
opening. This is simplest method of sealing, and the binding
rubber is advantageously stuck on to ~he puncturing point
before the insertion o the needle. ~
The suction method according to the invention can
likewise also be used to advantage in connection with the
retreading itselfl if the made-up tyre is completely or
partially enclosed with a complete or partial cover. The
suction procedure by means of a hollow needle here permits
occlusions to be removed by suction from the layer structure
of the tyre at different positions on the tyre periphery.
When using bonding rubber for sticking and sealing the perfora-
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tion, the latter is automatically and permanently closed whenvulcanising the tyre, by vulcanization of the binding rubber
used for sealing purposes.
The invention is hereinafter more fully explained
by the description of constructional examples with reference
to the drawings, wherein:
Fig. 1 is a perspective view of the upper half of a tyre with
tread elements of an earth-moving machine with a
position for repair, which is covered by means of a
flexible covering as a sheathing;
Fig. 2 is a cross-sectional view of a tyre having a sheath
or cover stuck and sealed off on the tyre walls;
On the tyre 1 of an earth-moving vehicle as shown in
Figure 1 is to be seen a repair position indicated generally
2, which has been prepared, roughened, filled with unvolcanized
binding rubber 4 and smoothed, and thereafter has been closed
off with a flexible cover 3a, for example of rubber material,
provided as a sheath. The encircling edge 5 of the cover 3a
is stuck by means of an adhesive material, in the present case
a binding rubber material, along its entire length on the
tyre and sealed off, that is to say, both along its path on
the tyre wall ànd also over the tread lands and depressions.
If a vulcanization of the binding rubber only used for sealing
\ purposes is not desired, raw rubber without sulphur, acceleratorm
etc., is for example used. In this way, the repair point is
enclosed all round by the cover 3a and sealed off, so that now
it is possible for the cover 3a to be punctured by means
of a hollow needle 16 which is provided with a handle 17
and which is connected to a controllable vacuum pipe, and the
repair point 2 can be subjected to a pressure treatment by
means of vacuum. For this purpose, the tip of the hollow
needle 16 only penetrates to such an extent into the cover 3a
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that the opening of the hollow needle 16 just reaches the space
which is beneath the cover 3a. Now all air and gas occlusions
in the interstice are removed. As soon as the cover 3a is
bearing tightly everywhere on the repair point 2, because the
suction effect has ended, the hollow needle 16 is retracted and
the puncturing point is sealed off and stuck with binding
rubber. Before introducing the hollow needle 16, binding
rubber in the form of a rubber piece lOd is applied and
pressed tightly on the puncturing position before the said
rubber piece lOd and the cover 3a are then simultaneously
punctured by the hollow needle 16. In this way, an immediate
sealing of the puncturing point after withdrawal of the needle
is very greatly simplified and made easier.
The vulcanization of the tyre as thus prepared can
now take place in the autoclave. However, also a local
heating is possible, as for example by heat radiation directed
on to the repair position or by the fitting of heating elements
into the cover 3a.
Figure 2 illustrates the use of a cover 3, the edges 5 of
which are stuck by means of adhesive material 14 on to the
carcass la and 6ealed off thereon. The figure shows a built-up
tyre, on to the prepared carcass la of which has been applied
a tread ll with interposition of a sheet 10 of binding rubber.
As can be seen, the sealing of the cover edges 5 is effected
underneath the seams lOa of the binding rubber sheet 10 on the
walls of the carcass la, this being effected on the left-hand
part of Figure 2 by placing adhesive material 14, for example
bonding rubber, beneath the edge or rim 5, while in the case
of the right-hand part of Figure 2, this is effected by the
interstice between the edge 5 of the cover3 and the carcass
la being bridged over by a strip 14 of adhesive material, for
example, binding rubber. The method is carried out in other
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respects as explained in connection with ~igure l, i.e. the
harmful air and gas occlusions are withdrawn by suction
from the space beneath the cover 3 ancl also from the inters-
tices between the binding rubber plate or sheet lO and the
carcass la, and also the tread 11, by means of the hollow
needle 16. This suction process can if necessary take place
at several positions on the tyre circumference. Always after
the hollow needle 16 has been retracted, the point of puncture
is once again sealed with binding rubber material, which
advantageously also in this constructional example is already
applied beforehand in the form of a piece of binding rubber
lOd to the cover 3 and is punctured by the hollow needle 16,
so that ultimately there is obtained a layer formation of the
tyre which is free from air occlusions and which is enclosed by
the cover 3.
