DE2041268A1 - Method and device for the production of toroidal objects - Google Patents

Description

DR. MÖLLER-BOR6 Dl PL-PHYS. DR. MAN ITZ DIPL-CHEM. DR. DEUFEL DIPL-ING. FINSTERWALD Dl PL-I NG. GRÄMKO W

PATENT LAWYERS

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Hl / Sv - D 1181

0? HE DUlTLOP COMPANY LIMITED

Dunlop House, Ryder Street, St James ¹ Sy

London S.W.1, England

Method and apparatus for manufacturing toroidal objects

The invention relates to a method and a device, for the production of an object which has a closed torus shape.

In the method of manufacturing a tire having a closed toroidal shape according to the present invention, at least a substantial part of the tire is molded or cast into an annular core by injection or transfer, an annular gap is left in the tire to allow removal of the core, the core becomes removed and brought the tire with or without the addition of a strip of material or tape in the gap in the closed üforusform with a seam .

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According to the invention an apparatus for producing tires with a closed toroidal shape is also provided, which a two-part mold defining a substantially toroidal mold cavity, a segmented toroidal core for an arrangement in the cavity, means for opening the mold and means for moving the segments of the core axially and radially from the mold for removing the molded articles therefrom.

The method of the invention is particularly suitable for the manufacture of closed toroidal tubeless pneumatic tires and such tires can be made with bead cores or, if desired, without bead cores. In the manufacture of such tires, at the stage in which at least a substantial portion of the tire is molded or cast around an annular core, the molding or casting of the sidewalls, the tread and the portion between the bead cores with a slot in one of these parts, to remove the core. Alternatively, one of these parts, for example the tread portion, which may be extruded, molded or cast as a secondary operation, may be omitted from the casting or molding. In either alternative, the bead cores can be placed in the mold before the molding or casting operation is started and the tire is then molded around the bead cores.

Preferably, the slot or gap is left in the outer periphery of the tire, for example the crown area of the tire, rather than in the inner periphery of the tire, for example between the bead cores.

In the case where a slit is left in one of the sections of the tire, the shooting can be done by means of a seam can be achieved by using a hot plate or high frequency

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welding is applied when the tire is made of thermoplastic material, or by using a suitable adhesive. "In the case where the molding or casting is done in two sections, these

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can be mechanically fastened together with / or without a Swiss process or an adhesive or can simply be welded together as above. Alternatively, a tape of material can be attached to the tire to bridge the gap or slot, for example a tread ring where the gap or slot is in the uron of the tire. The Haterialband can with "ä the tire are bonded, or it can form a further stage are placed under application.

A threaded valve core "or a simple valve can be integrally molded into the tire or a preformed valve or valve core can be inserted into the mold and the tire can be molded onto this.

The masses or compositions used in the manufacture of tires according to the invention are preferably thermoplastic and advantageously exhibit in the tire Young's modulus of at least approx.

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30 kg / cm (4 x .5 x 10 "pounds per sq.in.) and an elongation (real elongation) of no more than 15 % in. Of length

a load of approximately 7 kg / cm (100 pounds per sq..in.) des Cross-section at a temperature of 30 ° C.

Examples of compositions that are used can, are (1) a composition which is a copolymer of Ä'thylen with a vinyl alkanoic acid ester, a Alkyl acrylate, an alkyl methacrylate or an unsaturated one Include acid in which the olefin moiety in

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an amount of at least 60% by weight of the copolymer is present or mixtures of such copolymers with natural or synthetic rubbers, (2) a composition of a mixture of a crystalline, olefinic homopolymer or copolymer with a natural or synthetic rubber or with a rubber homopolymer of an X -olefin or ¹ copolymer of an X -olefin, (3) a composition of a plastomeric copolymer of ethylene and an X -olefin which contains at least 50 mol% of ethylene and in which parts of the molecular chain contain blocks of polyethylene, or a mixture of such a copolymer with a crystalline homopolymer or copolymer of ethylene or (X -olefin, which contains crystalline material in an amount of up to 4-0% by weight of the mixture, (4) a composition which is an elastomeric block copolymer of the general formula A- ( BA) has a polymer block at v / elcher A he tJbergangstemperatur 2nd-order (glass transition temperature) alc higher 25 ° C and a numerical average molecular weight ranging from 200 to 100,000, and B is an elastomeric polymer block having an average molecular weight in the range 25000 to 1000 and a glass transition temperature below 10 ⁰ C and η represent an integer from 1 to 10, and (5) a composition of a block copolymer with a configuration ABC, in which A is a block of a relatively rigid polymer, B is an elastomeric block and C is a crystalline block.

Compositions of types (1), (2) and (3) become more varied in British Patent 1,159,675, Compositions of type (4) in more detail in the British patent

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font 1 159 676 and the compounds of type (5) used Block copolymers described in British patent application 10539/6 $.

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Has the use of thermoplastic compositions the advantage that the waste and scraps can be reused while the compositions are crosslinked through the use of organic peroxides, sulfur or through irradiation improvements in terms of certain properties. If a heat or high frequency welding operation is to be carried out, a thermoplastic material must be used, but in these cases crosslinking can optionally be carried out by irradiation of the finished object can be seen.

The invention is illustrated below with reference to the drawing, for example described; in this shows;

Fig. 1 is a sectional view showing one half of a device is shown for the injection molding of a toroidal tire with a slot along it the crown of the tread is suitable, and

FIG. 2 is a sectional view showing one half of a device which is suitable for bringing the tire formed in the device of FIG. 1 into the closed toroidal shape by means of a seam. M.

The casting device shown in FIG. 1 consists of a two-part mold which has an upper and a lower mold half 1 and 2 and defines a toroidal cavity 3 in the closed state. In the cavity there is a segmented annular core 4 which is held in place by webs or shafts 5 attached to the segments ₉ which form the slot in the crown of the cast or shaped aid. The trays 5 are also used to remove the segments © of the core from the mold au when the casting is complete. The core

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is divided into four segments (not shown), each of which forms a »quarter of the ring and is held in place by its own shaft, with the shafts 5 at are clamped in their place between the mold halves 1 and 2, when the mold is closed. Injection points 6 are provided at intervals around the lower half of the two-part mold, the points being all by one hot pouring head system 7 from one single central injection point 8 are supplied.

In the mold halves 1 and 2 and in the core 4, provision is made to control their temperature; for example passages 9, 10 and 11 may be provided in them in order to to allow the passage of heating or cooling fluids through them, and / or the mold halves can be integral with electric heaters.

In operation, a bead core 12 is placed in the lower half 2 of the mold, the segments of the core 4 becoming one Ring assembled in the lower half 2 of the mold, the second bead core 15 is placed on top of the core, a valve insert (not shown) is placed in the lower half 2 of the mold and the upper half 1 of the mold is used for a Close placed on the lower half 2 and thus the core 4 clamped in its position. An exact alignment of the core 4 in its position in the mold is by engagement of the projections 14 and 15 on the shafts 5 with corresponding Recesses in the upper and lower mold halves 1 and 2 promoted. The mold halves 1 and 2 and the Core 4 are heated by means of a passage of a hot fluid through passages 9 »10 and 11 and the material is via the hot casting head system 7 from the central injection point 8 into the mold through the spaced apart Injection points 6 are injected on the sidewall of the tire section in the lower half 2 of the mold.

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after the material has been injected and sufficient has cooled so that it has set in the mold, the upper half 1 of the mold is lifted off.

The segments of the core 4 are grounded axially by means of the shafts 5 upwards i; ur release of the lip or nose of the lower Half 2 of the mold lifted up and radially from the mold moved outward, removing the core segments from your formed bzvi. cast tire through the slot in the crown of the tire is relieved.

The cast tire is then removed from the mold. During the material injection / cooling period, mold halves 1 and 2 and core 4 are maintained at a fixed temperature which is high enough to allow the injected material to flow but also low enough for the material to settle can set in the mold quickly without the need for cooling the mold.

The slot in the ki-one of the tire is assembled or closed by a hot plate welding operation.

IT alas. Fig. 2 shows the device for this operation a mold in two halves 16 and 17, the break in the outer periphery of the mold with the location of the slot coincides in the crown of a tire placed in the mold.

An air line (not shown) is provided to blow air into a tire in the mold and four hot plate segments 18 are provided around the mold which, when moved radially inwardly into the mold, are used to form fit together in an annular plate.

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In operation, a tire 19 is angeacl.net in the lower half 17 of the shape and the air line is connected to the tire valve 20. The top half 16 of the mold is lowered far enough to contact the tire 19 but not far enough to compress the edges of the slot in the tire. The shape is dimensioned so that at this stage the edges 21, 22 of the slot to be welded together project just behind the lips or noses of the upper and lower mold halves 1 and 2.

The hot plate segments 18 are then put together in the mold and moved into the slot in the crown of the tire while air is blown into the tire 19 through the valve 20 to keep the tire 19 in contact with the mold. A slight pressure is then applied to the mold halves 1 and 2, to press the edges of the slot against the hot plate 18 (as shown in Figure 2). The pressure is relaxed, «■ die Hot plate segments 18 are moved away and the mold halves 1 and 2 are joined together, whereupon the softened edges 21 and 22 of the slot into an abutting one Relationship are forced.

The tire 19 is then allowed to cool while the air pressure is maintained.

Finally the air pressure is released and the tire 19, which now has a closed toroidal shape, becomes from the Shape removed.

The invention envisions a very quick and easy process for the production of pneumatic tires and it is particularly suitable for the production of wheel tires with low loist demands suitable as lvinder wheel tires. ,: ■

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8AD ORiG [MAl.

Claims (13)

_ 9 -
Patent claims A method for producing a tire with a closed toroidal shape, characterized in that that at least a substantial part of the tire around an annular core by injection or transfer is molded or cast that an annular gap is left in the tire for removal of the core, that the core is removed and that the tire is in the closed toroidal shape with or without the addition of a strip of material is brought into the gap with finer /. 2. The method according to claim 1, characterized marked, that the gap in the outer circumference of the tire is left. 3. Method according to claim 1 or 2, characterized in that it is e k e η η ζ e ic η e t that the gap is a slot left in the crown of the tire. 4-. Method according to one of Claims 1 to 3> marked by the fact that the essential part of the Tire that is molded or cast by injection or transfer to form a pair of bead cores _ will. ^ 5. The method according to any one of the preceding claims, characterized marked that the tire is a tubeless pneumatic tire. 6. The method according to any one of the preceding claims, characterized marked that the tire is a thermoplastic Comprises mass that has an elastic in the tire modulus of elasticity (Young's modulus) of at least approx. 30 kg / cm 2
(4j5 x 10 pounds per sq "in.) And an elongation (creep) 109810/1603 of not more than 15 % in length in a Laotian ο
st of 7 kg / cm '(1OO pounds per square inch) of cross sections at a temperature of 30 ⁰ C to V / e ^. 7. The method according to any one of the preceding claims, characterized in that the tire is seam welded by means of hot plates. 8. The method according to claim 7 »characterized in that the tire is maintained by air pressure in a mold while the slit is welded together by a hot plate is inserted between its edges, the plate is removed and the edges of the slit together by closing the mold, will. 9 · The method according to any one of claims 1 to 6, characterized marked that a slot or gap in which help is left and that a strip of material or a tape of material is attached to the tire that bridges the slot or gap. 10. The method according to claim 9, characterized in that the tape in a further forming stage is applied. 11. Apparatus for making tires with closed Toroidal shape, characterized by a two-part shape, which is a substantially toroidal shape Defined mold cavity, a segmented toroidal core for an arrangement in the cavity, means for opening the mold and means for moving the segments of the core axially and radially from the mold to remove molded articles therefrom. 109810/1609 12. The device according to claim 11, characterized in that g e k e η η ζ ei c h η e 't that egg injection points at intervals around the lower half of the two-part mold, with all points being provided by a hot pour head system x ^ earth supplied from a single injection point. 13. The apparatus according to claim 11, characterized in that the segments of the core each have a stem or shaft, by means of which the the
Segments can be moved into / out of the mold, with the shafts wedged between the mold halves are, if, the mold is closed. Ä 1A-. Apparatus according to claim 13, characterized ge 1; e η η - indicates that cooperating localization surfaces are provided on the shafts and on the mold halves, whereby a precise alignment of the core segments is obtained, vena, the shafts are clamped between the mold halves. BAD ORIGINAI. 109810/1609