GB1560052A

GB1560052A - Method of manufacturing rubber articles and means forcarrying out said method

Info

Publication number: GB1560052A
Application number: GB2613977A
Authority: GB
Original assignee: Firestone Tire and Rubber Co
Current assignee: Bridgestone Firestone Inc
Priority date: 1976-06-23
Filing date: 1977-06-22
Publication date: 1980-01-30
Also published as: JPS53270A; DE2728333C2; IT1079077B; FR2355648A1; FR2355648B1; DE2728333A1

Description

(54) METHOD OF MANUFACTURING RUBBER ARTICLES AND MEANS FOR CARRYING OUT SAID METHOD (71) We, THE FIRESTONE TIRE & RUBBER COMPANY, a Company organised and existing under the laws of the State of Ohio, United States of America, of 1200 Firestone Parkway, Akron 17, Ohio, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of manufacturing pneumatic tyres.

Industrial products exist which are entirely or partially based on rubber whose composition, structure and geometric shape are relatively complex.

Their manufacture assumes the use of materials which are different both in their nature and their composition. It is necessary, mostly, to form a blank from intermediate elements, to produce a well-defined final structure. This is followed lastly, by the final moulding operation which simultaneously realises two objectives, on the one hand, the almost final dimensional shaping of the product and, on the other hand, the vulcanization of the rubber mixes.

The forming of the blank requires very considerable labour and fabricating means.

The moulding operation constitutes practically the last step in the manufacture.

The formation of the blank requires the assembly of intermediate parts which when assembled together according to a given procedure and vulcanized produce the final desired structure. It is important, at this stage of manufacture, to have intermediate parts which have good adhesion, that is to say the ability of each element to adhere or to stick to the structure in the course of fabrication without resorting to glueing agents. It is also important to have sufficient plasticity to ensure ease of shaping by the action of stresses.

It must be noted that the plasticity of the parts is, to a very great extent, one of the most difficult problems to master in the production of intermediate products having dimensional characteristics which are both very accurate and very faithfully reproduced.

During the moulding operation, the vulcanization of the rubber mixes is carried out under the simultaneous action of time, temperature and pressure. This irreversible transformation modifies the physical and chemical properties of the initial rubber mixes by conferring elasticity on them and causing the properties of adhesion and plasticity to practically disappear.

The moulding operation always associates a dimensional shaping and a vulcanization, even partial, and hence a heat stabilising of the product.

There are known to exist injection moulding devices for the manufacture of parts made from only a single rubber mix, which parts of complex shape. The mix is introduced directly into a closed mould, through an injection nozzle, after plasticizing of the rubber mix. The advantage is the reduction in the time of vulcanization of the part since the injection temperature of the rubber is very close to its vulcanizing temperature.

The adhesive power and plasticity of accelerated but unvulcanized rubbers and their capacity to preserve these properties as long as no vulcanization has taken place are known.

The present invention provides a method of manufacturing a pneumatic tyre comprising the steps of placing an annular bead in a mould adapted to receive an accelerated, unvulcanized rubber compound by an injection system, plasticizing said rubber compound at a temperature sufficient to plasticize the rubber compound yet insufficient to cause premature, partial vulcaniz ation of the compound, injecting said rubber compound at a given temperature under high pressure into said mould to form a bead filler piece contiguous with said annular bead, the mould being maintained at a temperature which is such that vulcanization of the rubber compound does not occur, removing said annular bead and bead filler assembly from said mould while the rubber compound is still in an unvulcanized state, assembling said assembly into a tyre and vulcanizing said tyre.

It is thus possible to produce in a single operation of the injection type an assembly of a bead filler and a bead core for subsequent use in the manufacture of a pneumatic tyre. Tyre manufacturing methods previously necessitated use of several techniques leading to the fabrication of one or more parts in order to apply the bead filler and bead core during the assembly of a pneumatic tyre. These techniques have the intermediate drawbacks of storage, identification and preparation of the individual parts.

Other advantages of the present invention are that the dimensional qualities of the individual intermediate parts are improved, the moulding operation being more accurate. Due to the fact of the pressure utilised, any possibility of including air is eliminated. The droppings and rejects can be recycled, which is not the case with vulcanzied elements. Moreover, the level of productivity is high.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of an annular bead and bead filler assembly for use in the manufacture of a pneumatic tyre in accordance with the method of the present invention; Figure 2 is a sectional view along the line Il-Il of Figure 1; and Figure 3 shows a mould suitable for preparing the assembly of Figures 1 and 2.

The method of the present invention comprises plasticizing by any suitable means an accelerated unvulcanized rubber compound, then injecting this rubber compound at a certain temperature into a closed mould which is kept at a chosen temperature. The temperature of the mould is chosen so that vulcanization of the moulded part, even at its surface is avoided thereby to preserve its previously described properties and also to permit easy and rapid unmoulding, without the intervention of specific unmoulding compounds which could alter the properties of adhesion of the rubber in the subsequent use of the intermediate product. Moreover, the physical properties of the compound develop in such a way that the distortion of the part is minimal in the course of the unmoulding operation.

The manufacture of a pneumatic tyre requires rubber mixes with well-defined physical and chemical properties, cables of natural or synthetic style fibers, and steel wires.

In standard tyre manufacture, the intermediate bead core or bundle and bead filler are assembled separately with other parts and then united in a final stage, after a preparatory operation.

In this invention the bead core and the bead filler strip are united prior to assembly into the final product into a pre-assembly of one piece. This means that the piece is built into the tyre for this operation, instead of the two pieces previously used.

Thus, a metallic annular bead 1 is introduced into a mould 2 and the filler rubber 3 is injected at very high pressure through a nozzle 4.

The mould shown in Figure 3 is a multiple mould and hence composed of several complementary blocks or units (2a, 2b, 2c, etc.). Certain of these units are traversed by a circulation of fluid through passages 5 forming part of a temperature regulating device which is present in order to avoid any vulcanization. The units define between them a system of branches 6 for the distribution of the filler rubber compound, connected to the injection nozzle 4.

The metallic annular bead 1 is held in place in the mould space formed between two blocks, by a centering or holding device constituted by a ring 7 to which it is fastened. The ring 7 is itself ensleeved on an annular wall 8 formed in one of the two blocks. On unmoulding, the ring 7 forms an integral part of the intermediate product (Figure 2).

Generally, the invention enables parts of a pneumatic tyre to be manufactured by the cold-forming of acelerated but unvulcanized rubber. The rubber compound may be only a single rubber mix or may include several types of rubber mixes.

One or several supports of metal or material of other types may be incorporated in the pneumatic tyre prior to the vulcanization step. The parts of the pneumatic tyre are then assembled together due to the fact notably of their adhesive power and the group of parts thus assembled is vulcanized to obtain a pneumatic tyre.

WHAT WE CLAIM IS: 1. A method of manufacturing a pneumatic tyre comprising the steps of placing an annular bead in a mould adapted to receive an accelerated, unvulcanized rubber compound by an injection system, plasticizing said rubber compound at a temperature sufficient to plasticize the rubber compound yet insufficient to cause premature,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ation of the compound, injecting said rubber compound at a given temperature under high pressure into said mould to form a bead filler piece contiguous with said annular bead, the mould being maintained at a temperature which is such that vulcanization of the rubber compound does not occur, removing said annular bead and bead filler assembly from said mould while the rubber compound is still in an unvulcanized state, assembling said assembly into a tyre and vulcanizing said tyre. It is thus possible to produce in a single operation of the injection type an assembly of a bead filler and a bead core for subsequent use in the manufacture of a pneumatic tyre. Tyre manufacturing methods previously necessitated use of several techniques leading to the fabrication of one or more parts in order to apply the bead filler and bead core during the assembly of a pneumatic tyre. These techniques have the intermediate drawbacks of storage, identification and preparation of the individual parts. Other advantages of the present invention are that the dimensional qualities of the individual intermediate parts are improved, the moulding operation being more accurate. Due to the fact of the pressure utilised, any possibility of including air is eliminated. The droppings and rejects can be recycled, which is not the case with vulcanzied elements. Moreover, the level of productivity is high. The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of an annular bead and bead filler assembly for use in the manufacture of a pneumatic tyre in accordance with the method of the present invention; Figure 2 is a sectional view along the line Il-Il of Figure 1; and Figure 3 shows a mould suitable for preparing the assembly of Figures 1 and 2. The method of the present invention comprises plasticizing by any suitable means an accelerated unvulcanized rubber compound, then injecting this rubber compound at a certain temperature into a closed mould which is kept at a chosen temperature. The temperature of the mould is chosen so that vulcanization of the moulded part, even at its surface is avoided thereby to preserve its previously described properties and also to permit easy and rapid unmoulding, without the intervention of specific unmoulding compounds which could alter the properties of adhesion of the rubber in the subsequent use of the intermediate product. Moreover, the physical properties of the compound develop in such a way that the distortion of the part is minimal in the course of the unmoulding operation. The manufacture of a pneumatic tyre requires rubber mixes with well-defined physical and chemical properties, cables of natural or synthetic style fibers, and steel wires. In standard tyre manufacture, the intermediate bead core or bundle and bead filler are assembled separately with other parts and then united in a final stage, after a preparatory operation. In this invention the bead core and the bead filler strip are united prior to assembly into the final product into a pre-assembly of one piece. This means that the piece is built into the tyre for this operation, instead of the two pieces previously used. Thus, a metallic annular bead 1 is introduced into a mould 2 and the filler rubber 3 is injected at very high pressure through a nozzle 4. The mould shown in Figure 3 is a multiple mould and hence composed of several complementary blocks or units (2a, 2b, 2c, etc.). Certain of these units are traversed by a circulation of fluid through passages 5 forming part of a temperature regulating device which is present in order to avoid any vulcanization. The units define between them a system of branches 6 for the distribution of the filler rubber compound, connected to the injection nozzle 4. The metallic annular bead 1 is held in place in the mould space formed between two blocks, by a centering or holding device constituted by a ring 7 to which it is fastened. The ring 7 is itself ensleeved on an annular wall 8 formed in one of the two blocks. On unmoulding, the ring 7 forms an integral part of the intermediate product (Figure 2). Generally, the invention enables parts of a pneumatic tyre to be manufactured by the cold-forming of acelerated but unvulcanized rubber. The rubber compound may be only a single rubber mix or may include several types of rubber mixes. One or several supports of metal or material of other types may be incorporated in the pneumatic tyre prior to the vulcanization step. The parts of the pneumatic tyre are then assembled together due to the fact notably of their adhesive power and the group of parts thus assembled is vulcanized to obtain a pneumatic tyre. WHAT WE CLAIM IS:

1. A method of manufacturing a pneumatic tyre comprising the steps of placing an annular bead in a mould adapted to receive an accelerated, unvulcanized rubber compound by an injection system, plasticizing said rubber compound at a temperature sufficient to plasticize the rubber compound yet insufficient to cause premature,

partial vulcanization of the compound, injecting said rubber compound at a given temperature under high pressure into said mould to form a bead filler piece contiguous with said annular bead, the mould being maintained at a temperature which is such that vulcanization of the rubber compound does not occur, removing said annular bead and bead filler assembly from said mould while the rubber compound is still in an unvulcanized state, assembling said assembly into a tyre and vulcanizing said tyre.

2. A method according to claim 1, wherein a single rubber mix is used.

3. A method according to claim 1, wherein several types of rubber mixes are used.

4. A method according to claim 1, 2 or 3, wherein additional elements of metal or other materials are included in the pneumatic tyre prior to vulcanization.

5. A method according to claim 1, substantially as hereinbefore described with reference to, and as shown, in the accompanying drawings.

6. A pneumatic tyre whenever produced by a method as claimed in any one of the preceding claims.