GB1581169A

GB1581169A - Method for production of tyres from cellular rubber

Info

Publication number: GB1581169A
Application number: GB23810/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-06-08
Filing date: 1977-06-03
Publication date: 1980-12-10
Also published as: DK251077A; YU141277A; FI61424B; NO143261C; IN146111B; IT1083758B; JPS5947659B2; DE2725560A1; ES459584A1; NO761945L; DE2725560C2; SE7706559L; AT354281B; JPS52150485A; NO143261B; ATA403577A; FR2354192B1; FI771766A; FI61424C; FR2354192A1

Description

(54) METHOD FOR PRODUCTION OF TIRES FROM CELLULAR RUBBER (71) I, ALF MATHIESEN, a Norwegian citizen, of Olsen Bergsgt. 30, 2600 Lillehammer, Norway, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of producing wheel tires of cellular rubber with of without internal cavities, in a mould which is divided radially and also parallel to its axis into three main parts and of which the inner surface defines the outer shape of the tire including two circumferentially extending tire beads.

When producing a tire to be inflated and which may possibly contain an inner tube, the tire is as a rule built up manually of noncured rubber strips rather flat in the transverse direction prior to curing. Only during the curing process the tire will get its final shape. To this effect the non-cured tire is arranged on a so-called curing tube and placed in a curing mould, whereupon said tube is inflated so that the strips are pressed against the walls of the mould. The cord layer of the tire is arranged in or between rubber strips and subjected to an optimal tension during curing, which is necessary for an inflated tire which is always under superatmospheric pressure.

When producing a tire having an inner cellular rubber core which is caused to expand during the curing and, correspondingly, when producing a tire which is to have a solid unfoamed inner core, it is preferable to press the tire into the desired shape prior to curing in order to avoid air bubbles in the tire.

This method is relatively complicated and the object of the invention is to provide a method of producing puncture-free tires, which is very simple and which avoids the necessity of several machines of special construction, and thereby saving working time.

The invention consists in the method of producing wheel tires of cellular rubber, with or without internal cavities, and with textile reinforcement, in a mould which is divided radially and also parallel to its axis into three main parts, the inner surface of the mould defining the outer shape of the tire including two circumferentially extending tire beads, characterized in that in the mould there is placed at least one textile ribbon with coarse meshes which is of a length corresponding to the circumference of the tire, and a width somewhat less than the transverse outer peripheral dimension of the tire between the beads, that the textile ribbon is secured along its longitudinal edges to be anchored in the beads, that within said ribbon there is placed a mixture of noncured rubber and foaming material, whereupon the mould is closed and subjected to heat for activating the foaming material and curing of the rubber, whereby a part of the material in the rubber mixture expands through the meshes of the textile ribbon and is brought in close contact with the inner surface of the mould.

According to a modification of the method for producing a tire with a core of cellular rubber which is covered at least over part of its surface with an outer layer of unfoamed rubber, there is additionally arranged in the mould, outside the textile ribbon and in contact with same, at least one strip of unfoamable, unvulcanized rubber, whereby, upon heating the closed mould, the expanding rubber mixture passing through the meshes of the textile ribbon is connected to the inner surface of the outer layer of unfoamed rubber of which the outer surface is brought into close contact with the inner surface of the mould.

The rubber strips which contain foaming material and which form the inner core, expand during the curing. The strip or strips is/are placed in the curing mould either separately or fixed to a textile ribbon having coarse meshes and which will form a cord layer and may consist of a woven textile which along its longitudinal edges near the wheel rim is attached to a steel wire ring or the like which is embedded in the beads.

Said textile material is also arranged in the curing mould and may, if desired, have been rubberized beforehand. The textile ribbon has a width less than the transverse circumferential dimension of the tire, such as a width of 85 mm when the transverse circumferential dimension is to be 100mm. During curing the expanding rubber forming the inner core will be pressed out through the meshes of the textile material and form the tread of the tire. If it be not desired that cellular rubber should form the tread of the tire, there is placed in the mould, prior to or simultaneously with the arrangement of the strip or strips which are to form the core of cellular rubber of the tire, a strip of unfoamable, vulcanized rubber, to the inner surface of which the expanding mixture of rubber and foaming material which passes through the textile ribbon during curing, is combined, the outer surface of the unfoamable rubber strip being formed by the mould with the tread of a desired pattern.

In order that the inner core shall penetrate through the meshes of the textile material, the core must produce a certain pressure during the expansion, for which reason the lower part of the curing mould must be so gastight that the gas developed in the rubber can not too easily escape. However, if said part of the mould is completely tight, the excess gas cannot escape from the mould so that there is formed a gas layer at the lowest part which will prevent the rubber from expanding completely to the bottom of the mould.

It may, therefore, be necessary to provide an adjustment of the mould, so that undesired excess pressure is released.

The rubber with added foaming material may also, prior to curing, be mechanically pressed through the meshes of the textile ribbon to form the outer sides of the tire.

The method of production described above is best suited for tires for lighter vehicles, such as bicycles, mopeds or the like. It is of substantial importance that the textile material has relatively coarse meshes since the expanded rubber must have the possibility to pass, as soon as possible during the curing, through the meshes of the textile material and form an outer side corresponding with the inner side of the mould. For lighter vehicles a single textile ribbon having coarse meshes will be completely sufficient to provide the tire with the necessary strength.

It may be of interest to provide the tire with only the tread of unfoamed rubber, whereas the sides are produced from expanded cellular rubber. In this case a strip of unfoamable, unvulcanized rubber is placed in the bottom of the mould before the textile ribbon is placed in position, and the rubber with foaming material is caused to expand and press the unfoamable rubber strip against the inner surface of the mould.

The invention will now be described with reference to the drawing, in which Fig. 1 shows a radial section of a rubber tire which is built up from cellular rubber and is formed with inwardly open cavities; Fig. 2 shows a section along line II--II in Fig. 1; Fig. 3 shows a similar section of a tire having an outer tread of unfoamed rubber; and Fig. 4 shows a radial section of a mould known per se for the production of rubber tires.

In Fig. 1 the cellular rubber in expanded condition is numbered 1 and has been formed in a mould as shown in Fig. 4 to be described below. The tire is provided with evenly distributed cavities 2 formed by protrusions extending radially and outwardly from the inner part of the mould. The intermediate walls thereby formed are numbered 3 and their lower ends 3' are so made that they extend below the bead 6 of the tire to rest on the wheel rim or the rim tape. Each of the beads 6 contains a circumferential steel wire ring 5 to which is fastened a longitudinal edge of a textile ribbon 7 which has a width less than the transverse outer circumferential dimension of the tire so that said ribbon of textile material will remain embedded in the rubber during its expansion, and is of a length corresponding to the tire circumference.

In order to facilitate mounting of the tire on the wheel rim, a circumferentially extending recess 8 is formed within and parallel to each bead 6. According to Figs. 1 and 2 the tread or wear surface 4 of the tire is formed with circumferential ribs or with any other suitable tread pattern.

The mould as shown in Fig. 4 is divided radially so as to comprise two symmetrically equal shells la and lb and parallel to its axis to provide an inner bottom portion 14 which consists of a number of sector-shaped parts. The inner wall of the shells la and Ib form the side walls 1 and the tread or wear surface 4 of the tire, said shells being formed with longitudinal, parallel grooves 4a in the upper inner wall. The shells la and 1b are placed against each other and are mutually aligned by means of pins 13 cooperating with corresponding bores in the dividing walls between the two shells. The sectors of the bottom portion 14 are formed in one piece with a number of radially projecting protrusions 2a which correspond with the cavities 2 in the tire. At each side of the sectors there is formed a circular recess 6a with a radially extending rib 8a for forming the beads 6 of the tire in which is embedded the steel wire ring 5, as well as for forming the circumferential recess 8. In order to prevent mutual displacement of the sectors of the bottom portion 14 in relation to the shells la and lb, the sectors are formed at each side with a recess 15 cooperating with correspondingly shaped flanges 16 on the two shells as clearly shown in Fig. 4.

When producing a tire according to Figs.

1 and 2 one of the shells, such as la, Fig. 4, is placed on a horizontal table, whereupon the sectors of the bottom portion 14 are placed in position with one recess 15 meshing with a circumferential flange 16. At the place in the mould where the bead 6 is to be formed, there is previously arranged a ring-shaped steel wire 5 around which has been folded one of the longitudinal edge portions of the textile ribbon 7. After the sectors of the bottom portions 14 have been brought in position as described, there is placed on the inner side of the textile ribbon one or more strips of non-vulcanized rubber with foaming material added thereto. The strip or strips of non-vulcanized rubber is/are of such a length as to fit at the inner side of the textile ribbon 7. Then a second steel wire ring 5 is arranged at the place where the second bead 6 is to be formed, and the second longitudinal edge of the textile ribbon 7 is folded around said second ring 5. Now the mould may be closed by arranging the second shell lb on the first shell la. Said two shells are pressed together by means of clamps or the like (not shown), and the combined mould is heated to a curing temperature of about 150O C. To start with the heat will activate the foaming material which is added to the rubber and cause the rubber to expand and fill the whole space of the mould. During said expansion a part of the rubber will be forced through the meshes of the textile ribbon 7 and be pressed against the inner wall of the shells la and lb. The remaining part of the rubber will expand in the spaces between the protrusions 2a and fill the rest of the mould space.

As shown in Fig. 4 the sectors of the bottom portion 14 are formed with recesses 3'a between the protrusions 2a to form the lower ends 3' of the walls 3 between the spaces 2. As already mentioned said ends 3' protrude below the beads 6 of the tire for resting against the rim of the wheel. After the rubber has expanded and filled the whole mould space and has been cured, the clamps (not shown) as well as the shell lb are removed, whereupon the tire together with the sectors of the bottom portion 14 are lifted up from the first shell la. The tire will have such a resilience that the sectors of the bottom portion 14 may easily be removed together with the protrusions 2. After all the sectors have been removed in this way the tire is finished.

Fig. 3 shows a corresponding section as Fig. 2, but in this case the tire is to be formed with a core 11 of cellular or sponge rubber and an outer skin 12 of unfoamed rubber which covers the side walls of the tire and has a thicker, outer peripheral portion forming the tread 4. When producing a tire according to Fig. 3, the same mould may be used as for the production of the tire according to Figs. 1 and 2. In the case of Fig. 3 there are first placed in the mould two relatively thin strips of non-vulcanized rubber without foaming material. Said thin strips are arranged in superimposed fashion to form a tread which is thicker than the side walls.

Then the textile ribbon 7 and the first steel wire ring 5 is brought in position, and at the inside of the textile ribbon there are placed further rubber strips with foaming material added thereto. After the mould has been assembled and clamped fast, heat is applied as described above. During the expansion of the rubber strips which are to form the inner sponge rubber core 11 of the tire, said rubber will expand through the meshes of the textile ribbon 7 and unite with the non-vulcanized, unfoamed rubber strips which are to form the side walls 12 and the tread 4.

Above is mentioned that the rextile ribbon 7 is fastened to the reinforcing wire rings 5 along its edges. However, in most cases it will be sufficient only to fold the edges of the textile ribbons around the wire rings since the expanding rubber will penetrate through the meshes and ensure the necessary connection of the ribbon with the rings 5.

As mentioned the textile ribbon 7 may be previously rubberized, in which case the ribbon has special coarse meshes in order that the rubber core material may penetrate therethrough during expansion and curing.

In order to prevent the textile ribbon from forming folds along the side walls of the tire, preferably a ribbon is used which is expandable lengthwise.

The expression "rubber" covers any natural or synthetic material which behaves similarly to rubber.

WHAT I CLAIM IS: 1. Method of producing wheel tires of cellular rubber, with or without internal cavities, and with textile reinforcement, in a mould which is divided radially and also parallel to its axis into three main parts, the inner surface of the mould defining the outer shape of the tire including two circumferentially extending tire beads, characterized in that in the mould there is placed at least one textile ribbon with coarse meshes which is of a length corresponding to the circumference of the tire, and a width somewhat less than the transverse outer peripheral dimension of the tire between the beads, that the textile ribbon is secured along its longitudinal edges to be anchored in the beads, that within said ribbon there is placed a mixture of non-cured rubber and foaming material, whereupon the mould is closed and subjected to heat for activating the foaming material and curing of the rubber, whereby a part of the material in the rubber mixture expands through the meshes of the textile ribbon and is brought in close contact with the inner surface of the mould.

2. Modification of the method claimed

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. is placed on a horizontal table, whereupon the sectors of the bottom portion 14 are placed in position with one recess 15 meshing with a circumferential flange 16. At the place in the mould where the bead 6 is to be formed, there is previously arranged a ring-shaped steel wire 5 around which has been folded one of the longitudinal edge portions of the textile ribbon 7. After the sectors of the bottom portions 14 have been brought in position as described, there is placed on the inner side of the textile ribbon one or more strips of non-vulcanized rubber with foaming material added thereto. The strip or strips of non-vulcanized rubber is/are of such a length as to fit at the inner side of the textile ribbon 7. Then a second steel wire ring 5 is arranged at the place where the second bead 6 is to be formed, and the second longitudinal edge of the textile ribbon 7 is folded around said second ring 5. Now the mould may be closed by arranging the second shell lb on the first shell la. Said two shells are pressed together by means of clamps or the like (not shown), and the combined mould is heated to a curing temperature of about 150O C. To start with the heat will activate the foaming material which is added to the rubber and cause the rubber to expand and fill the whole space of the mould. During said expansion a part of the rubber will be forced through the meshes of the textile ribbon 7 and be pressed against the inner wall of the shells la and lb. The remaining part of the rubber will expand in the spaces between the protrusions 2a and fill the rest of the mould space. As shown in Fig. 4 the sectors of the bottom portion 14 are formed with recesses 3'a between the protrusions 2a to form the lower ends 3' of the walls 3 between the spaces 2. As already mentioned said ends 3' protrude below the beads 6 of the tire for resting against the rim of the wheel. After the rubber has expanded and filled the whole mould space and has been cured, the clamps (not shown) as well as the shell lb are removed, whereupon the tire together with the sectors of the bottom portion 14 are lifted up from the first shell la. The tire will have such a resilience that the sectors of the bottom portion 14 may easily be removed together with the protrusions 2. After all the sectors have been removed in this way the tire is finished. Fig. 3 shows a corresponding section as Fig. 2, but in this case the tire is to be formed with a core 11 of cellular or sponge rubber and an outer skin 12 of unfoamed rubber which covers the side walls of the tire and has a thicker, outer peripheral portion forming the tread 4. When producing a tire according to Fig. 3, the same mould may be used as for the production of the tire according to Figs. 1 and 2. In the case of Fig. 3 there are first placed in the mould two relatively thin strips of non-vulcanized rubber without foaming material. Said thin strips are arranged in superimposed fashion to form a tread which is thicker than the side walls. Then the textile ribbon 7 and the first steel wire ring 5 is brought in position, and at the inside of the textile ribbon there are placed further rubber strips with foaming material added thereto. After the mould has been assembled and clamped fast, heat is applied as described above. During the expansion of the rubber strips which are to form the inner sponge rubber core 11 of the tire, said rubber will expand through the meshes of the textile ribbon 7 and unite with the non-vulcanized, unfoamed rubber strips which are to form the side walls 12 and the tread 4. Above is mentioned that the rextile ribbon 7 is fastened to the reinforcing wire rings 5 along its edges. However, in most cases it will be sufficient only to fold the edges of the textile ribbons around the wire rings since the expanding rubber will penetrate through the meshes and ensure the necessary connection of the ribbon with the rings 5. As mentioned the textile ribbon 7 may be previously rubberized, in which case the ribbon has special coarse meshes in order that the rubber core material may penetrate therethrough during expansion and curing. In order to prevent the textile ribbon from forming folds along the side walls of the tire, preferably a ribbon is used which is expandable lengthwise. The expression "rubber" covers any natural or synthetic material which behaves similarly to rubber. WHAT I CLAIM IS:

1. Method of producing wheel tires of cellular rubber, with or without internal cavities, and with textile reinforcement, in a mould which is divided radially and also parallel to its axis into three main parts, the inner surface of the mould defining the outer shape of the tire including two circumferentially extending tire beads, characterized in that in the mould there is placed at least one textile ribbon with coarse meshes which is of a length corresponding to the circumference of the tire, and a width somewhat less than the transverse outer peripheral dimension of the tire between the beads, that the textile ribbon is secured along its longitudinal edges to be anchored in the beads, that within said ribbon there is placed a mixture of non-cured rubber and foaming material, whereupon the mould is closed and subjected to heat for activating the foaming material and curing of the rubber, whereby a part of the material in the rubber mixture expands through the meshes of the textile ribbon and is brought in close contact with the inner surface of the mould.

2. Modification of the method claimed

in claim 1, for producing a tire with a core of cellular rubber which is covered at least over part of its surface with an outer layer of unfoamed rubber, wherein there is additionally arranged in the mould, outside the textile ribbon and in contact with same, at least one strip of unfoamable, unvulcanized rubber, whereby, upon heating the closed mould, the expanding rubber mixture passing through the meshes of the textile ribbon is connected to the inner surface of the outer layer of unfoamed rubber of which the outer surface is brought into close contact with the inner surface of the mould.

3. Method as claimed in claim 2, wherein the outer layer is formed by two strips of unfoamable, unvulcanized rubber which are arranged in superimposed fashion in the mould in order to form a tread having greater thickness than the side walls of the tire.

4. Method as claimed in claim 1, 2 or 3, wherein reinforcing wire rings are arranged in the bead portions of the mould and the longitudinal edges of the textile ribbon are folded around and fixed to the reinforcing wire rings.

5. Method as claimed in any one of the preceding claims, wherein the textile ribbon has been previously rubberized.

6. Method as claimed in any one of the preceding claims, wherein the textile ribbon is expandable in its longitudinal direction only.

7. Method as claimed in any one of the preceding claims, wherein the mould is provided with radially outwardly directed protrusions on the radially inner part of the mould for forming inwardly opening cavities in the cellular rubber material, and the quantity of the mixture of unvulcanized rubber and foaming material is so chosen that the walls between the cavities are formed with radially inwardly directed extensions for resting against the wheel rim or the rim tape of the wheel.

8. Method of producing wheel tires of cellular rubber substantially as hereinbefore described with reference to the accompanying drawings.

9. A wheel tire when produced by the method claimed in any one of the preceding claims.