FI57226B - FOERFARANDE FOER PAOVULKANISERING AV EN VULKANISERAD SLITBANA PAO ETT FORDONSDAECK - Google Patents

Description

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Patani och r * gtft * ntyr «lMn 'Antflon utltgd och utl.tkrlfUn published 31.03.80 (32) (33) (31) Pyydttty« uolk «ut — Btgftri prlorltat 25.06.69 USA (US) 836 ^ 5 ^, 09.07 .69, 10.11.69 Germany

Federal Republic-Förbundsrepubliken Tyskland (DE) p 193 ^ 767.2, P 1956391.8 (71) Vacuum Vulk Holdings Ltd., 360, Queen Street, Nassau, Bahamas-Bahamas ama (BS) (72) Vilhelm Schelkmann, Witten / Ruhr, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (7 * 0 Leitzinger Oy (5I1) Method for vulcanizing a vulcanized tread strip to the surface of a driving guide tire - fr & n ansökan 1727/70 (patent 5I + 2U8)

The invention relates to a method for adhering a vulcanized tread strip to the surface of a vehicle tire by using a tread with outer wool, curved edges around the side edges of the vehicle tire and interposing an unvulcanized bonding rubber layer and placing the tire in a vulcanized press chamber according to the vulcanization requirements. the autoclave.

Known tread strips are most often made in a tread plane press with a planar lower surface in both the longitudinal and transverse directions. In this case, however, there are difficulties in connecting such tread strips to the surface of a ring curved and coated with a layer of bonding rubber. The tread strip must be adapted to the shape of the ring curved both circumferentially and transversely. The fitting results in a corresponding elastic deformation of the tread. This results in stresses that act against the holding force of the adhesive layer. When the bonding rubber layer at the beginning of the autoclave vulcanization heats up and then loses a substantial part of its holding force, the elastic restoring forces, especially in the area of the tire sidewalls, exceed the reduced holding force of the bonding rubber layer, resulting in partial release of the tread layer from the tire surface.

One known method (DT patent 1,094,976, CH patent 444,474) uses an elastic full sheath which holds the layers of the vulcanizable ring together by means of external overpressure and / or internal underpressure even when the adhesive force of the bonding rubber layer decreases. In this case, it has been found that profile shifts in the profile base are possible, because the jacket pressure only affects the raised parts of the profile and not the profile bases in the intermediate spaces of the profiles. On the other hand, the pressure provided by these sheaths is not entirely sufficient at the sidewalls of the tire to eliminate the risk of peeling off the edges of the tread layer with sufficient certainty. In addition, the use of elastic full sheaths significantly increases the cost of retreading tires because they require careful fabrication and handling.

Thus, in order to avoid the use of a full sheath, a method is known (CH patent 325 925) in which a steel rim is placed on its outer surface during vulcanization to prevent the elastic parts of the ring to be coated from being detached, while the inside of the ring is pressurized. However, the steel strip breaks easily and further puts local pressure on the protruding profile parts so that when the bonding rubber finally softens completely, it runs unevenly corresponding to the uneven distribution of pressure caused by the steel strip, resulting in an uneven thickness of the vulcanized bonding rubber layer.

Furthermore, in order to avoid a strong elastic shaping of the tread strip, it is known to manufacture a tread strip which is already shaped approximately to correspond to the longitudinal and transverse curvature of the vehicle tire (DT Patent 1,232,845). However, it has been shown that the tread design corresponding to the curvature of the tire surface cannot be carried out in each individual case with such precision that the use of pressure or tensioning means in the autoclave could be avoided. Thus, the attachment of such treads has always taken place by using a surrounding full sheath which acts to drain gaseous and liquid components from the tire ply and later in an autoclave to ensure tread retention on the tire as the adhesion of the bonding rubber layer decreases due to heating. However, since the full sheath rests only on the protruding profile surfaces, the pressure is transferred unevenly to the bonding rubber layer, which consequently transfers to the points where the pressure is at its lowest, i.e. to the points below the profile spaces.

3 57226

The object of the invention is to provide a method of the type mentioned at the beginning for vulcanizing a pre-vulcanized tread band to the surface of a worn vehicle tire, with which the above-mentioned disadvantages associated with known methods can be avoided in a simple manner.

According to the invention, this object is achieved by using a tread strip whose radius of curvature of the projecting edges is smaller than the radius of the corresponding side edge of the vehicle tire to be coated, so that the edges of the tread strip abut against the sidewall of the tire. This solution according to the invention makes it possible to carry out the vulcanization without any tightening jacket, i.e. the ring on the surface of which the coating is attached can be placed in the pressure medium of the autoclave without any jacket.

According to an embodiment of the invention, the prestressing of the edges of the tread strip can be reinforced by compressing a rubber sheath which adheres around the seam of the bonding layer. Also in this case, the use of an awkward full sheath is avoided and it is ensured that at the beginning of vulcanization, as the holding force of the bonding rubber layer decreases, the side edges of the tread layer do not give up or come off. Instead of expensive full diapers, the invention can use a diaper of virtually any rubber material or plastic used during or after application to the tread to form a sealed space from which unwanted gaseous or liquid components can be removed by vacuum to release the tire layer structure from detrimental effects.

The solution according to the invention also avoids the uneven flow of the bonding rubber during the softening phase, which results from the uneven pressure distribution when using a full jacket or steel strip. This avoids the risk of profile shifts. The uniformity of the thickness of the bonding rubber layer is also maintained during and after vulcanization. As a result, the adhesion of the tread to the tire is improved and the driving safety of the retreaded tires is increased.

In practice, it has been found that the holding force provided by the solution according to the invention, which is caused by the pressing of the side edges of the tread strip by elastic tension against the side edges of the tire, advantageously complements the holding force of the bonding rubber. Namely, in the Auto-57226 clave, the bonding rubber softens first from the points that first heat up. These are the edge areas of the bonding rubber layer over which there are only very thin tread side edges of the tread. As a result, the holding force of the bonding rubber deteriorates rapidly when the central areas of the binding rubber layer have not yet heated up and, as a result, lose all or part of their holding force. However, detachment of the side edges is not possible due to the inward elastic tension. Later, when the middle areas of the bonding rubber layer also soften and lose their holding force, the edge regions of the bonding rubber layer are already vulcanized and consequently form already inseparable joints between the tread and the tire, so that no tread movement can take place on the tire body.

The invention will now be described with reference to the accompanying drawing, in which Figure 1 shows a cross-section of a tread strip used in the method according to the invention in the rest state and Figure 2 shows a cross-section of an assembled tire on which the tread strip of Figure 1 is placed.

The rubber tread strip 2 shown in Fig. 1 has curved and tapered side edges 51, the inner edges of which have a radius of curvature R. This shape has already been given to the tread strip 2 in connection with its manufacture. The body 1 of the tire to be coated is machined in such a way that the outer radius R 'of its side edge is larger than the inner radius R of the side edge 51 of the tread strip 2.

When the tread layer 2 is now placed on the tire body 1 by interposing a bonding rubber layer 3, the side edges 51 become stretched outwards, whereby they are pressed with an elastic prestress against the side surface of the tire body. This prestressing is caused by the fact that the inner radius R of the tread layer 2 is smaller at rest than the outer radius R 'of the corresponding edge of the tire carcass.

When the tread layer 2 is thus placed on the tire body 1 free of air entrapment, e.g. by temporarily using a jacket enabling a vacuum effect, the bonding rubber layer 3 of the assembled tire can thus be vulcanized in an autoclave without any aids 57226 such as a jacket or other tightening member.

However, if necessary, in the region of the side edges 51, sub-sheaths can be used which cover only these edge portions of the ring and which strengthen the compression pressure of the side edges 51.

Since the displacement of the tread layer 2 and also the outflow of the flowable bonding rubber is prevented when the tire is heated in an autoclave, the tires can be stacked in the autoclave without any aids together or next to each other.

It is particularly important in this case that the pressure acting on the tread layer 2 in the autoclave is similar everywhere, i.e. both in the profile projections and in the profile bases, so that the softening bond-rubber layer is not subjected to uneven pressure.

The tread strip 2 can also be multi-parted, e.g. it has a central part with a rectangular cross-section and associated edge-or-angular parts with a substantially triangular cross-section on both sides thereof. Thus, on both sides of the tire body 1, there are two outermost edges of the bonding rubber layer, and also in this case the side edges 51 of the multi-part tread strip can be formed so that an inwardly directed prestress is generated.