RU2330757C2 - Method of tyre manufacture and method of control of uncured elastomer material application during manufacture of tyre - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: uncured tyre and toroidal support are installed inside vulcanising form, in which molding cavity is created, for molding and vulcanisation of uncured tyre. Molding cavity includes section, in which molding and vulcanisation are performed with formation at constant volume. Application of elastomer material onto rigid toroidal support is performed by control of elastomer material volume distribution on toroidal support to correspond to preset curve of material excess volume. Curve indicates differences between distribution of material volume, which forms uncured tyre, and volume that is available in section of molding cavity, which is intended for molding and vulcanisation of uncured tyre, with constant volume.

EFFECT: invention allows to reduce amount of waste in production of tyres by drawing and analysis of curve.

23 cl, 8 dwg

Description

The present invention relates to a method for manufacturing a tire. In particular, the invention relates to a method for manufacturing a tire, wherein the unvulcanized tire is assembled on a toroidal support, and then molded and vulcanized in a vulcanization form forming a molding cavity, which includes at least a portion in which molding and vulcanization are carried out at constant volume.

Typically, in a tire production cycle after a manufacturing process in which various tire components are made and assembled to create an unvulcanized tire (i.e., an uncured or unprocessed tire), a molding and vulcanization process is performed to stabilize the tire structure and give it the desired geometric shape, typically characterized specific tread model. To this end, the tire is placed in a vulcanization form, usually containing a pair of lateral parts made axially close to each other, which are designed to act on the bead and sidewalls of the tire, and at least one row of peripherally distributed sectors intended for radial moving close to each other to act on the tread band of the tire. In more detail, the side portions and sectors are mutually movable between an open position in which they are spaced apart from each other to ensure loading of the processed tire and a closed position in which they form a molding cavity whose inner surface is the same as the outer surface of the resulting tire.

In the known method of molding and vulcanizing a tire, a rigid toroidal support having the same configuration as the inner surface of the obtained tire is located inside the tire. For example, US Pat. No. 4,895,692 discloses a mold for treating and vulcanizing an elastomeric tire comprising a rigid rod defining an inner surface of the tire, two side portions and a peripheral ring divided into multiple segments. The mold elements provide molding of the outer and inner surfaces of the tire and completely form the molding space for the tire. Therefore, vulcanization is performed at a constant volume.

Another approach is disclosed in PCT patent application WO 01/00395, which describes a method in which an unvulcanized tire made on a toroidal support is closed in a vulcanization form. The lateral sections of the tire are placed between the lateral parts of the mold and the toroidal support. Steam or other fluid under pressure is fed into the diffusion gap formed due to the expansion of the tire between the inner surface of the tire and the outer surface of the toroidal support. More specifically, after closing the mold, the tire is enclosed in a retaining gap defined between the outer surface of the toroidal support and the inner walls of the molding cavity. The holding gap when the mold is closed has a larger volume than the volume occupied by the tire itself.

In particular, the holding gap has two radially inner portions, the shape and size of which substantially correspond to the shape and size of the tire side portions, and a radius outer portion bounded between said radially inner portions, with radial dimensions larger than the radial dimensions, those. thickness measured on the outer radius portion of the tire itself.

Recently, new tire manufacturing methods have been proposed that do not need to separately manufacture the semi-finished products used in traditional methods, for example, tread band, sidewalls, carcass layers, belt belts and bead cores, if we only talk about the basic elements. According to the aforementioned innovation processes, these semi-finished products are replaced by a small number of basic components that are manufactured “in place” where the unvulcanized tire is assembled. These basic components are elongated elements, usually in the form of a strip or tape, made of untreated elastomeric material, possibly reinforced with one or more reinforcing cords.

This new tire assembly process is carried out by placing said base components on said toroidal support for forming structural parts of the tire (essentially corresponding to parts made from conventional semi-finished products in accordance with conventional manufacturing methods) using a small number of types of movement, such as radial application directed to the axis of rotation of the toroidal support, and peripheral application to the surface of the toroidal support driven in rotation around its axis, or combination thereof.

The basic components are fed to the toroidal support in the form of continuous elongated elements. The components applied along the radius can be pre-cut into sections of a given size, while the components applied around the periphery are cut after being wound onto a drum. These basic components usually have a cross section with smaller dimensions than the dimensions of the structural part to be built.

Once the assembly steps are completed, the unvulcanized tire prepared in accordance with the above method is closed in a vulcanization form, for example, belonging to the type disclosed in WO 01/00395, and finally vulcanized.

It should be noted that this process gives a very high degree of production flexibility, since due to the significant similarity of the basic components for each type of tire for the production of different tire models, you only need to change a limited number of parameters that control the toroidal support rotations for peripheral and axial components extension for radius-mounted components.

Despite this, some difficulties may arise in setting the technical requirements that must be provided on the equipment that controls the movement of the toroidal support in order to obtain the correct position of the basic components on it when they plan to manufacture a new tire. In particular, due to the location of the base components on the toroidal support, problems may arise during molding and vulcanization, especially in areas where vulcanization is performed with a constant volume.

In particular, it has been found that excess elastomeric material in the constant-volume mold portion can cause uncontrolled movements of the elastomeric material within the mold, which can lead to unacceptable defects and / or geometric distortions in the finished tire. This makes it necessary to ensure constant redefinition of technical requirements and equip them with equipment in order to correctly control the movement of the toroidal support when applying a complex structure until the correct technical requirements are found. When planning the production of another tire, this can lead to a large amount of waste in the tire production process, i.e. rejection of many tires due to defects or geometric distortions. In addition, it also extends the period from the start of development of a new tire to be produced to its entry into the market.

In addition, control of only the total volume of material located on a rigid toroidal support, compared with the total available volume in the molding cavity, may be insufficient to obtain a vulcanized tire without defects and / or geometric distortions.

However, it should be noted that ways have been found to solve the problem of reducing the amount of waste in the tire production process, including molding and vulcanization in a vulcanization form containing a section in which vulcanization is performed with a constant volume. In particular, ways were found to solve the problem of determining technical requirements for a reduced period of time for the correct application of elastomeric material on a toroidal support to be inserted into the vulcanization form, especially when planning new tires for production.

These problems can be solved by obtaining and analyzing a curve showing the distribution of the volume of elastomeric material over the available volume in the constant volume section of the molding cavity. In the rest of the description and in the claims, a curve of this type will be referred to as a “curve of the volume of excess material”. Explicit preferred functions suitable for determining the curve of the excess volume of the material will be given in the remainder of the description.

In particular, a curve of this type related to the distribution of material in the unvulcanized tire of the first tire model from which the finished tires are obtained, which, after molding and vulcanization, have practically no defects and / or geometric distortions, can be used as a predetermined curve to determine technical requirements for the preparation of unvulcanized tires of a second tire model different from the first tire model (for example, having a different size, different geometric proportions or different stiffness of any part, Which as the sidewall, or another arrangement of elastomeric fillers and / or insertions or other profile sidewall or sidewall different height, etc.). This method can significantly reduce the amount of waste, as well as the period from the start of development of the second tire model to its entry into the market.

According to a first aspect of the present invention, there is provided a method for manufacturing a tire in which unvulcanized elastomeric material is applied to a substantially rigid support to form an unvulcanized tire; an unvulcanized tire placed on a support is introduced into the vulcanization form; close the vulcanization form to form a molding cavity between the outer surface of the support and the inner surface of the vulcanization form; and molding and vulcanizing the unvulcanized tire, wherein at least one portion of the unvulcanized tire is molding and vulcanizing with a substantially constant volume in at least one portion of the molding cavity; moreover, when applying unvulcanized elastomeric material to the support, the first curve of the excess volume of the material of the elastomeric material is determined with respect to the available volume in at least one section of the molding cavity, depending on a given direction, and the distribution of the volume of elastomeric material over the rigid support is controlled so that essentially match the first curve.

Preferably, when controlling the distribution of the volume of elastomeric material over the support, a first set of technical positioning requirements for equipment associated with applying unvulcanized elastomeric material to the support corresponding to the first curve of the excess material volume is determined, and the equipment is moved in accordance with the set of technical requirements.

Preferably, when determining the first curve of the excess material volume, a predetermined curve of the excess material volume is provided, at least a second set of technical requirements for positioning for the equipment is provided, a second curve of the excess material volume corresponding to the set of technical requirements for positioning is determined, and the second curve is compared with the predetermined curve to determine the difference in volume distribution between the second curve and a given curve depending on a given direction.

Preferably, a first cross-sectional profile of at least one portion of the unvulcanized tire from the second set of technical positioning specifications is additionally determined.

Preferably, the first cross-sectional profile is further modified using differences in the volume distribution between the second curve and the predetermined curve, thereby defining a second cross-sectional profile of at least one portion of the unvulcanized tire.

Preferably, when determining the first set of technical requirements for positioning for equipment, a first set of technical requirements for positioning is determined from at least the second section profile.

Preferably, the equipment comprises a mechanical manipulator associated with the support.

Preferably, when an elastomeric material is applied to a support, an uncured elastomeric material is extruded in the form of elongated elements including an elastomeric material.

Preferably, the first set of technical requirements for positioning comprises a plurality of positioning records, each of the positioning records containing at least spatial coordinates of a given section point of an elongated element.

Preferably, the first, second or predetermined curve of the excess volume of material represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y.

Preferably, the first, second or predetermined curve of the excess volume of material represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y.

Preferably, the first, second or predetermined curve of the excess volume of the material is the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ .

Preferably, the first, second or predetermined curve of the excess volume of the material is the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ .

Preferably, the predetermined direction is a radial direction.

According to a second aspect of the present invention, there is provided a method for controlling the application of an unvulcanized elastomeric material to a rigid support for manufacturing an unvulcanized tire to be molded and vulcanized in a vulcanization form, wherein the vulcanization form and the rigid support form a molding cavity such that at least one portion of the unvulcanized tire is molded and cure at a substantially constant volume in at least one portion of the molding cavity, in which the first a set of technical requirements for positioning for equipment related to the application of unvulcanized elastomeric material on the support, provide a section profile of at least a portion of the molding cavity and determine from the first set of technical requirements for positioning and from the section profile of the molding cavity the first curve of the excess volume of unvulcanized elastomeric material material in relation to the available volume in the area of the molding cavity, depending on the specified direction.

Preferably, a predetermined curve of the excess volume of the material is additionally provided, and the first curve is compared with the predetermined curve to determine the difference in the volume distribution between the first curve and the predetermined curve depending on the predetermined direction.

Preferably, a first sectional profile of at least one portion of the unvulcanized tire from the first set of positioning specifications is additionally determined.

Preferably, the first cross-sectional profile is further modified using differences in the volume distribution between the first curve and the predetermined curve, thereby defining a second cross-sectional profile of the portion of the uncured tire.

Preferably, the first or predetermined excess material curve represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y.

Preferably, the first or predetermined excess material curve represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y.

Preferably, the first or predetermined excess material curve represents the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the specified mold cavity, contained between the values of y ₁ , y ₂ .

Preferably, the first or predetermined excess material curve represents the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ .

Preferably, the predetermined direction is the radial direction of the unvulcanized tire.

According to a third aspect of the present invention, a computer program is created, loaded directly into a computer memory, for implementing a method for controlling the application of unvulcanized elastomeric material to a rigid support for manufacturing an unvulcanized tire to be molded and vulcanized in a vulcanization form, wherein the vulcanization form and the rigid support form a molding cavity, that at least one portion of the unvulcanized tire is molded and vulcanized at a substantially constant volume in at least one area of the molding cavity, and the program contains code parts intended for

obtaining the first set of technical requirements for positioning for equipment associated with the application of unvulcanized elastomeric material on a support,

obtaining a cross-sectional profile of at least a portion of the molding cavity,

determining, from the first set of technical requirements and from the cross-sectional profile of the molding cavity, the first curve of the excess material volume of unvulcanized elastomeric material with respect to the available volume in the molding cavity section, depending on a given direction.

According to a fourth aspect of the present invention, a computer program product is provided comprising a computer-readable medium on which a computer program according to the third aspect of the present invention is stored.

Other features and advantages of the present invention will become apparent from the following detailed description of some illustrative embodiments thereof, disclosed by way of non-limiting examples with reference to the accompanying drawings, in which:

Figure 1 - installation for the manufacture of tires for vehicle wheels on a sufficiently rigid toroidal support;

Figure 2 is a sectional section of an unvulcanized tire ready for molding and vulcanization;

3a and 3b show a portion of a molding cavity and a corresponding portion of an unvulcanized tire to be molded and vulcanized in such a molding plane, respectively;

4 is a first illustrative curve of the excess volume of the material;

5 is a second illustrative curve of the excess volume of the material;

6 is a third illustrative curve of the excess volume of material;

7 is a comparison of a given curve of the excess volume of material and the curve of the excess volume of material related to the new planned tire model; and

Fig. 8 is a comparison of a predetermined curve of an excess volume of material and a subsequent curve of an excess volume of material corresponding to modified specifications for performing an unvulcanized tire for a new tire model.

1, a preferred embodiment of an apparatus for manufacturing tires for vehicle wheels is generally indicated by reference numeral 1. Installation 1 is associated with a device 2 for producing tires for vehicle wheels or for performing part of a tire production cycle.

This includes the manufacture of various tire components that are obtained directly on a substantially rigid toroidal support 3 having an outer surface 3a, 3b, the shape of which is substantially mated to the inner shape of the tire itself. For this purpose, the device 2 may, in General, contain many work items 4, 5, 6, each of which is designed to perform at least one of these works for the manufacture of tires on the toroidal support 3.

In more detail, in the example shown in FIG. 1 and described by way of example only, a portion of the device 2 is shown which is designed to carry out the frame structure on the outer surfaces 3a, 3b of the toroidal support 3. The frame structure contains at least one first frame a layer arranged so as to cover the outer surface 3a, 3b of the toroidal support 3, at least one pair of annular reinforcing structures located at the respective end edges of the frame layer, and possibly a second frame loi disposed in superposed relationship with the first carcass ply and the annular reinforcing structures. Each annular reinforcing structure may contain first and second annular inserts containing at least one metal wire wound in several turns arranged in the form of a crown, and an elastomeric material filler mounted axially between the first and second annular inserts.

In the area of the device 2 intended for carrying out the frame structure, for example, a first working point 4 can be provided for pre-heating the toroidal support 3 and / or possibly applying a lining on its outer surface, that is, a thin layer of rubber, which after vulcanization is completed airtight to maintain tire operating pressure.

The second working paragraph 5 may, in turn, be designed to perform frame layers. The formation of each layer can preferably be accomplished by sequentially applying strip elements arranged sequentially, side by side, with a mutual peripheral supply of a toroidal support 3 to the outer surface 3a, 3b. Additional details regarding production techniques for performing a frame layer or layers in the second working paragraph 5, largely disclosed in European patent applications No. 928680 and No. 928702 in the name of the applicant.

Can also be used the third working paragraph 6, designed to perform annular reinforcing structures at the inner end edges of the first frame layer. For this purpose, the third working paragraph 6 contains feeding devices designed to supply one or more elongated elements to be used in the implementation of the filler and the ring inserts. In more detail, the feeding devices may, for example, comprise a first extruder 14 for supplying, through a suitable feeding element 14a, at least one first continuous elongated element, for example, a strip of elastomeric material with a given cross-sectional size, used to make the filler of each of the ring reinforcing constructions. More specifically, it is preferable to ensure that the cross section of the elastomeric strip exiting the feed element 14a of the first extruder 14 has a conveniently reduced size compared to the cross section of the filler being manufactured. The filler in its final configuration is obtained by supplying a continuous elastomeric tape to the toroidal support 3, while the indicated support, under the action of the peripheral distribution means, rotates the peripheral distribution around its geometric axis of rotation, designated “X”. Simultaneously with the rotation provided by the toroidal support 3, the lateral distribution means will cause controlled relative displacements between the toroidal support itself and the feed element 14a connected to the first extruder 14, so that the elastomeric strip will form a series of turns located radially and / or along the axis side by side until they form a filler.

The feeding means provided in the third working paragraph 6 may further comprise at least one second extruder 15, designed to supply, through a suitable feeding element, not shown in the drawings, a second continuous elongated element, for example a rubber-coated metal wire, for use in making annular inserts that are part of each annular reinforcing structure. Each annular insert is made by laying on the periphery of a corresponding rubber-coated metal wire on a toroidal support 3 by means of a rotational movement of the peripheral distribution communicated to said support around its geometrical axis, designated “X”. Meanwhile, the movement of the transverse distribution is also performed between the toroidal support 3 and the feed element of the second extruder 15, so that the continuous elongated element forms a series of turns sequentially located side by side, when moving away from the axis of rotation "X" of the toroidal support 3, to form corresponding ring insert.

Like moving the peripheral distribution, i.e. the rotation of the toroidal support around its axis “X” and the movement of the lateral distribution are preferably carried out by the direct movement of the toroidal support 3. In this case, the extruders 14, 15 forming the means for feeding the elongated element preferably maintain a fixed location when different components of the processed tire are made.

In order to provide a suitable movement of the support 3, the peripheral distribution means for bringing the toroidal support into rotation about its “X” axis and the lateral movement means can be integrated into the mechanical manipulator, indicated in general by the reference numeral 16, for releasably engaging, preferably lever a method with a toroidal support 3, in order to deliver it sequentially to each of the working points 4, 5, 6 and move it in a convenient manner relative to the indicated points.

In particular, a seven-axis mechanical manipulator 16, preferably of an anthropomorphic type, comprises a first link 17 having a first end 17a connected to the support platform 18 for rotation around a first horizontal axis of vibration “A” and around a second axis “B” located vertically or, in any case, perpendicular to the first axis "A" of the oscillation. The mechanical manipulator 16 further comprises a second link 19 connected to the second end 17b of the first link 17, with the possibility of oscillation around the third axis “C”, preferably parallel to the first axis “A”, as well as around the fourth axis “D” of oscillation perpendicular the third axis "C" and preferably located longitudinally relative to the second link. The end head 20 is functionally connected from its end to the second link 19 and is located so as to detachably engage with the toroidal support 3. The end head 20 perceives vibrations around the fifth axis "E", perpendicular to the fourth axis "D" of the oscillation. In a preferred embodiment, the fifth axis "E" is coplanar to the fourth axis "D", and the end head 20 further perceives vibrations around the sixth axis "F", perpendicularly oriented relative to the toroidal support 3 and relative to the fifth axis of vibration "E".

The use of lateral distribution means directly acting on the toroidal support 3 allows the use of the same mechanical manipulator 16 as for controlling the movement of the toroidal support 3 in front of the individual extruders 14, 15 and / or other feeding means provided in the first, second, third and others, possibly , existing working points, and for the transfer of toroidal support from one working point to another.

In particular, in the shown example, the mechanical manipulator 16 picks up the toroidal support 3 from the first working point 4 to transfer it to the second working point 5 to perform the first frame layer. In the formation of the first skeleton layer, the toroidal support 3 preferably remains in engagement with the mechanical manipulator 16, which preferably performs a suitable orientation of the support relative to the devices for feeding and stacking the strip elements provided in the second paragraph, and rotates it in accordance with the stepwise movement around the geometric X-axis, in synchronization with the operation of the aforementioned feeding and applying devices, or other convenient feeding and applying devices, in order to distribute the floor waist elements with a given circumferential step.

Then the toroidal support 3 is removed from the second working point 5 to be placed in front of the first extruder 14 of the third working point 6 to complete the first annular insert of each annular reinforcing structure. The toroidal support 13 is then placed in front of the second extruder 14 of the third work item 6 to cause the formation of filler of each annular reinforcing structure, and then again moved to the first extruder 14 to complete the second annular insert and thus complete the formation of annular reinforcing structures.

The mobility of the toroidal support along the six axes of vibration "A", "B", "C", "D", "E", "F" in addition to rotating it around the geometric axis "X" allows the correct application of elongated elements that exit them extruders 14, 15, regardless of the shape matching of the toroidal support 3 and the resulting tire components.

Upon completion of the ring reinforcing structures, the toroidal support 3 can again be transferred to the second working point 5 to form a second carcass ply, in the same manner as described previously in connection with the first carcass ply, thus completing the manufacture of the carcass tire structure.

The same mechanical manipulator 16, or another similar mechanical manipulator, or more, installed in the respective adjacent working areas provided in the device 2, can move the toroidal support 3 to the following extruders or other feeding devices designed to feed the elongated elements provided for execution additional components of the tire, such as, for example, the sidewalls, tread band, subprotective layers, as well as for transmitting the toroidal support to other operating points, intended, for example, for the vulcanization of a tire thus made unvulcanized.

The movement of the first link 17, the second link 19 and the end head 20 around the respective axes of oscillation "A", "B", "C", "D", "E", "F" can be controlled by the respective engines. The operation of all engines associated with the lateral distribution means or with the peripheral distribution means can be controlled by an electronic control device (not shown), in a way that ensures the correct movement of the toroidal support in the corresponding operating points 4, 5, 6 to obtain the correct execution of the bus components. Such proper movement of the toroidal support 3 can be controlled by sets of technical requirements for positioning (usually one technical requirement for positioning to fulfill one corresponding structural part of the tire), which is equipped with an electronic control device. In practice, sets of technical requirements can be computer files containing many positioning records defining spatial coordinates along which the toroidal support 3 successively follows when applying elongated elements provided by means 14, 15 of supply. As an example, the only positioning record included in the technical requirements files may contain two spatial coordinates (Xi, Yi) orthogonal to each other, defining a point on the base plane, and the angle βi, which the toroidal support 3 and the protrusion 14a of the extruder 14 should form . For completeness of information regarding the trajectory of the toroidal support in space, the fourth parameter Ri can be used, which determines the number of full revolutions that are necessary for the toroidal support to reach 3 spaces position in said reference plane defined in the next positioning record.

Said specification files may preferably be generated by a suitable computer program, such as, for example, the program disclosed in PCT Patent Application WO 02/05143, the general features of which are briefly mentioned here. Once the cross-sectional profile of the various components of the uncured tire to be carried out is determined, such a profile can be shown to the operator in graphical form on a computer screen. The operator “fills” the cross-sectional profile of various structural parts containing an elastomeric material with a base element of the corresponding material, placing one after another many sections of the specified element. The dimensions of the base element used, in particular its width and height, as well as the elastomeric material from which it is made, have predetermined values. In particular, different elastomeric compositions may be required for different structural parts of the tire.

For example, by means of a manual traction device, the operator locates sections of the basic elements within the section profile of various structural parts of the tire, partially overlapping them. This operation can be performed by selecting, for example, using a computer mouse, a section of the base element provided by the program, and dragging it into the form to be filled, which is displayed graphically until it is located near its final position. The program accurately determines the final position of each element, calculating the change in its shape due to the plasticity of the material forming the element, caused by stretching during installation and mutual overlapping with adjacent elements. This change in the cross-sectional shape of the base elements is calculated based on the previously stored properties of the material from which the element is made.

Thus, for each section located inside the form, the following parameters can be stored in the record of the technical requirements file:

the position (Xi, Yi) of a given point, for example, the midpoint of one side of the section of the element, relative to a given base coordinate system, for example, a pair of Cartesian axes combined with a toroidal support,

the orientation angle βi of the plot with respect to a given basic coordinate system, for example, the axis of rotation of the toroidal support.

The operator can then select the next item and, using the same procedure, position it near the previous item. The program determines, as explained previously, the final position of the next element, partially superimposing it on the previous element and deforming it in accordance with the degree of its plasticity. In addition, the operator can create a configuration of a number of rotations Ri, which the toroidal support must perform in order to allow the next element to reach the selected position, starting from the position of the previous element. In preferred embodiments, such a parameter Ri may be set to one by default.

The procedure continues until the entire space intended for the machined structural part is completely filled with sections of the base element in order to fully determine the technical positioning requirement for the machining procedure, i.e. production instructions necessary for the robot to correctly position the extruded elastomeric element on a toroidal support.

The above procedure is repeated for each structural part to be performed by applying the basic elements in order to reproduce in practice the actual application of the elements necessary for the formation of the whole tire.

Figure 2 shows, by way of example, a cross-section of a sidewall and a bead portion of an unvulcanized tire 100 ready for molding and vulcanization in a vulcanization form. The uncured tire 100 comprises a first backing layer 101, a second backing layer 102, a carcass ply 103, a reinforcing bead structure comprising three annular inserts 104, 105, 106, associated with respective inserts 107, 108, 109, an abrasion resistant layer 102, a sidewall 111 The unvulcanized tire 100 is located on a toroidal rigid support (not shown in FIG. 2) for molding and vulcanization in a vulcanizing form in which a molding cavity is formed between the outer surface of the toroidal rigid support, inner overhnostyu plurality of segments ensuring exterior molding of the tread and the inner surface of the two side portions of the mold, ensuring the molding of the tire sidewalls. For the purposes of the present invention, the term “rigid” (with respect to the toroidal support) should be understood to be “substantially undeformable” compared to a conventional inflatable vulcanizing membrane, which, by definition and design, is highly deformable compared to other parts of a conventional shape that undergo very little elastic deformations due to stresses caused by molding pressure.

The molding cavity contains at least a portion in which molding and vulcanization are carried out at a constant volume, i.e. a portion in which the available volume in the molding cavity and the volume of the corresponding portion of the unvulcanized tire 100 substantially coincide after closing the mold. According to a preferred embodiment, in the remaining portion of the molding cavity, the available volume of the portion of the molding cavity may be larger than the volume of the corresponding portion of the uncured tire, so that a gap can be formed between the outer surface of the uncured tire to be molded and vulcanized and the inner surface of the vulcanized mold after closing the mold . According to this preferred embodiment, molding the outer surface of the uncured tire corresponding to said portion of the uncured tire that is not in contact with the inner surface of the vulcanized mold after it is closed can be obtained by expanding the uncured tire in accordance with this portion by supplying a pressurized fluid to the diffusion gap which is formed between the outer surface of the support and the inner surface of the uncured shea s (as described, for example in said publication WO 01/00395).

In a preferred embodiment, the portion of the unvulcanized tire that is molded and vulcanized at a constant volume corresponds to the bead region and the sidewalls of at least most of the latter, while the portion of the tire that is molded and vulcanized with expansion corresponds to the crown region of the tire, including tread and possibly a small portion of the sidewalls. 2, dashed line A represents an example of the radially outer boundary of a portion of unvulcanized tire 100 to be molded and vulcanized at a constant volume in this preferred embodiment.

Figures 3a and 3b respectively show a portion of a molding cavity adapted to form and vulcanize an unvulcanized tire at a constant volume in the region of the sidewalls and beads, and a corresponding portion of a unvulcanized tire to be molded and vulcanized. Typically, the total volume of the material forming the portion of the unvulcanized tire to be molded and vulcanized at a constant volume is slightly larger than the volume available in the molding cavity, and the difference can reach 10-15%.

The problem regarding the molding and vulcanization of at least a portion of an unvulcanized tire with a constant volume is that it is necessary to control the volume of the material forming the unvulcanized tire located on a rigid toroidal support in order to avoid unexpected movements of the elastomeric material inside the mold with subsequent formation of defects and / or geometric distortion in a molded and vulcanized tire or, in the worst cases, damage to the shape itself.

However, it was found that a simple check of the ratio of the total volume of material located on a rigid toroidal support to the available volume in the molding cavity is not sufficient to guarantee a molded and vulcanized tire without defects and / or geometric distortions.

Instead, it has been found that it is important to monitor how the difference between the volume of material located on the toroidal support and the volume in the molding cavity changes depending on the given direction. In the remainder of the description and in the claims, a function describing said volume difference will be referred to as a function describing “excess material volume”. A predetermined direction for which the volume of excess material can be monitored is preferably the radial direction of the tire, indicated as in FIGS. 3a and 3b. Following the notation indicated in FIGS. 3a and 3b, the excess volume of material must be monitored in the portion of the molding cavity in which molding and vulcanization are carried out at a constant volume, i.e. between two base levels, denoted by y_ref_low and y_ref. Figures 3a and 3b also show the dotted sections V _mold (y) and V _mat (y) corresponding to the available volume in the molding cavity and the volume of the material located on the toroidal support to a radial height y, respectively. Preferred functions of excess material may be as follows:

where Vmold (y) and Vmat (y) correspond to volumes calculated between y_ref_low and y, while Vmold (y ₁ , y ₂ ) and Vmat (y ₁ , y ₂ ) correspond to volumes calculated between y ₁ and y ₂ . Amounts calculated by the formulas [1] and [3] can preferably be expressed as percentages.

In particular, it is especially convenient to use the aforementioned function [1] to perform analysis of the excess volume of the material. Such an analysis can preferably be carried out using a computer program loaded into the computer's memory.

The amounts of V _mold (y) and V _mat (y) to be used in the above formulas [1], [2] or [3] can be determined by suitable calculations. More specifically, V _mold (y) can be obtained by storing a cross-sectional image file of a portion of a molding cavity for molding and vulcanizing at a constant volume, from which the region of the molding cavity to a radial height y (dashed portion in Fig. 3a) can be determined using conventional ways. To obtain the volume V _mold (y) from such an area, the rotational symmetry of the molding cavity can be used. On the other hand, V _mat (y) can be obtained using conventional methods from technical requirements files that determine the positioning and sizes of the basic elements that make up the unvulcanized tire.

Figure 4 shows the direction, for the radial direction y, of the function [1] obtained from the set of technical requirements files for an illustrative tire (225 / 45R17 PZero Nero) made in the above-described manner, and from the corresponding section of the molding cavity adapted for molding and constant volume vulcanization. Such a portion of the molding cavity, extended from the radially lower point of the bead to a place just below the upper edge of the sidewall (see the dashed line at the radial height y_ref in Figures 3a and 3b). The abscissa y is normalized so that y_ref_low corresponds to 0, and y_ref corresponds to 100. EM (y) is expressed using percentage values. It should be noted that the very first section of the curve shows extremely high values of the excess volume of the material, due to the fact that the calculation of the difference from the exact value is performed on a very small section of the molding cavity and unvulcanized tire near the edge of the bead. As can be seen from the value achieved by the curve in accordance with the abscissa value of 100, the total volume of unvulcanized tire in the area to be molded and vulcanized at a constant volume is approximately 5% redundant with respect to the available volume of the area of the molding cavity. It should also be noted that the value of the EM function, which is slightly lower than the abscissa value of 50, is below zero; this means that in approximately the first 45% of the radial height of the mold, the total volume of the material is less than the corresponding available volume in the mold.

Figure 5 shows the deviation, in the radial direction y, of the above-mentioned function [3], corresponding to the same illustrative unvulcanized tire and shape as the curve in Figure 4. The curve in FIG. 5 has a similar deviation with respect to that shown in FIG. 4, with less amplification of changes caused by local increase or decrease in the ratio of the volume of the material to the available volume in the cavity.

FIG. 6 shows the deviation, in the radial direction y, of the function [3] mentioned, corresponding to the same illustrative unvulcanized tire and shape as the curves of FIGS. 4 and 5. The EMloc function makes it easy to recognize where the material volume locally exceeds the cavity volume or vice versa. As can be seen, strong local differences between the volume of the material and the volume of the cavity are found in Fig.6 in the radially outer section. Figure 6 also shows that in the radially inner region, the portion of the molding cavity has a volume slightly less than the volume of the corresponding portion of the unvulcanized tire.

It is established that the actual shape of the deviation curve of the function of the excess volume of the material, such as the mentioned functions [1], [2] or [3], can be used as a guide to determine the set of technical positioning requirements for equipment that controls the application of elastomeric material on the toroidal support. More specifically, it was found that if an unvulcanized tire was prepared using a given set of technical requirements and if such an unvulcanized tire after molding and vulcanization, at least partially, at a constant volume in the vulcanization form, stably provides a finished tire of an acceptable level in terms of defects and geometric distortion, then its curve of the excess volume of material can be used as a given curve for editing a set of technical requirements, when necessary and modification of such a set of technical requirements, for example, to cope with the structural modification of the tire. This situation is quite typical, for example, when setting up production of a new tire, since a series of tests on test samples of tires can lead to several modifications of the dimensions and / or composition of some structural parts of the tire in order to achieve the specified technical requirements for the tire in terms of traction , ease of manipulation, bending behavior, braking behavior, etc. However, a modification of the set of technical requirements for fulfilling an unvulcanized tire can lead to an imbalance in the distribution of the material applied to the toroidal support and to subsequent formation of defects and / or geometric distortions on the finished tire after molding and vulcanization, at least partially, with a constant volume. In these cases, further modification of the set of technical requirements is required, so that editing the entire process of determining technical requirements may require a lot of time and a large amount of production waste, i.e. rejected tires.

As an example, Fig.7 shows two curves 70 and 71 of the excess volume of material obtained using the above-mentioned function [1] for two unvulcanized tires that are identical but with different sizes of the outer axis of the insert (insert 109 in Figure 2). In particular, curve 70 is the same curve as the curve in FIG. 4 and relates to an unvulcanized tire having an insert having a radially outer position below 10 mm and having a total volume of 70 cm ³ less with respect to the insert of the unvulcanized tire, related to curve 71. Modification of the insert was required to avoid early cracking in the radially outer portion of the sidewall, at the junction with the tread band, to increase tire durability. However, the unvulcanized tire corresponding to curve 71 during the molding and vulcanization in the vulcanization form behaved almost perfectly in terms of the presence of defects and geometric distortions, and this is a condition that is no longer guaranteed after modification of the insert.

As can be seen from Fig. 7, curves 70 and 71 are practically superimposed at low radial heights and then separated at higher radial heights, in accordance with the fact that the modification of the insert implies only a modification of the radially outer part of the tire. It was also observed that the total volume of unvulcanized tire related to curve 71 is approximately 10% greater than the available volume of the mold cavity, while the total volume of unvulcanized tire related to curve 70 is approximately 5% greater than that available in the volume of the mold cavity is available, due to the smaller total volume of the insert. It is likely that defect formation after molding and vulcanization of the unvulcanized tire referring to curve 70 may be associated with this lower overall excess volume.

It has been found that to correct the technical requirements for the formation of an unvulcanized tire related to curve 70, curve 71 can be used as a predetermined curve. By calculating the differences between curve 71 and curve 70, corresponding to differences in the volume distribution for the radial direction between the two unvulcanized tires related to curves 70 and 71, a computer program (which may be the same program adapted to calculate and show the deviation of the function of the excess material volume) can to obtain a modified section of the unvulcanized tire previously related to curve 70 and graphically show it to the operator. The modified section takes into account differences in volume, calculated from the differences between curves 70 and 71. Before obtaining a modified section, the operator may need to select the structural part of the tire to be modified: if the internal structural part of the tire is modified, the corresponding modifications can preferably be applied to the external structural parts of the tire . In this example, the sidewall profile was modified using the calculated volume differences in the radial direction to modify the insert.

After receiving a new section of the unvulcanized tire or preferably structural parts of the tire to be modified, the operator can use the program adapted to reproduce the application of the elastomeric material on the toroidal support in order to fill the new section with suitable elastomeric elements and generate new technical files required to perform the modified unvulcanized tires.

FIG. 8 shows a predetermined excess material curve 71 along with a new excess material curve 72 corresponding to a new unvulcanized tire obtained from specification files defined as explained above. As you can see, the two curves are almost superimposed on each other. The tire corresponding to the unvulcanized tire of curve 72, after molding, had practically no defects and geometric distortions and had increased durability with respect to the tire corresponding to the unvulcanized tire of curve 70. The set of technical requirements for its implementation on the toroidal support was preferably edited in a very short time with a corresponding reduction in the number of rejected tires during tire alignment.

An analysis similar to that shown with reference to FIGS. 7 and 8 can also be applied using the functions [2] or [3] of the excess material disclosed above. However, it is especially convenient to use the function [1] of excess material.

The invention has been explained with reference to an illustrative method for manufacturing tires using robotic equipment adapted to transfer and move / rotate a toroidal support with respect to the extruder of the elastomeric material to apply strip elements to the toroidal support to form an unvulcanized tire. Obviously, the exact shape of the base element may differ from the strip shape and may, for example, be a fiber shape or any other suitable shape. In addition, the feed device can be moved, as an option or simultaneously with the toroidal support, in a coordinate way.

In addition, the invention can also be used with more conventional tire manufacturing methods, including making an unvulcanized tire to be molded and vulcanized on a rigid toroidal support for insertion into the vulcanization mold for molding and vulcanization, at least partially, at a constant volume. In such traditional methods, various structural parts forming unvulcanized tires are previously preformed separately in the form of semi-finished products with a given section profile determined by suitable technical requirements, and then assembled on a toroidal support. The functions of the excess material volume can be calculated in this case, provided that the section of the uncured tire to be performed is known, or, in other words, provided that the section profile adopted by various semi-finished products during assembly on a toroidal support is known.

In addition, the invention is disclosed with reference to the calculation of the functions of the excess volume of material in the radial direction. However, another suitable direction, for example an axial direction, can be selected for analysis. In addition, the functions of the excess material volume can be calculated using the cross-sectional areas of the unvulcanized tire and the molding cavity instead of the actual volume, especially in the case of calculations performed using the above functions [3], [4]. Thus, the term “volume” should not be interpreted for the purposes of the present invention as necessarily implying a volume in three spatial dimensions, and also includes a surface in two dimensions.

In addition, the invention is also applicable to manufacturing methods that use molded cavities that are fully adapted to molding and vulcanizing at a constant volume, not only partially, as explained in the disclosed examples.

The actual operations and / or calculations indicated in the analysis of the curves of excess material disclosed above can be applied in suitable program code parts of one or more computer programs and performed by any well-known general-purpose computer having suitable ability to process data, which is obvious to specialists in this areas of technology.

Generally speaking, at least one computer program is adapted to be loaded into the memory of a computer containing at least one central processor. A computer program may, for example, be embodied in one or more executable files located on a suitable medium accessible from a computer memory, such as, for example, a hard disk, diskette, CD-ROM, DVD-ROM, or an external disk readable via a local network . For the purposes of the present invention, the terms “computer program loaded directly into a computer’s memory” encompasses files necessary for executing an executable file or files, such as libraries, initialization files, etc., that may be located on suitable media accessible from a computer’s memory, such as, for example, a hard disk, floppy disk, CD-ROM, DVD-ROM, or an external drive readable through a local network. In addition, for the purposes of the present invention, the term “computer program” also encompasses files, possibly different from an executable file or files and / or files necessary for their execution, embodied on the installed software, adapted when run on a computer to install the executable file or files, as well as the files required to execute them. Such installable software may be located on a suitable medium, such as a floppy disk, CD-ROM, DVD-ROM, or it may be available for download from a network source, such as a server contained on a local network, or accessible via an external network, such as the Internet .

Claims (23)

1. A method of manufacturing a tire in which an unvulcanized elastomeric material is applied to a substantially rigid support to form an unvulcanized tire, an unvulcanized tire placed on the support is inserted into the vulcanization mold, the vulcanization mold is closed to form a molding cavity between the outer surface of the support and the inner surface of the vulcanization mold and form and vulcanize the unvulcanized tire, wherein at least one portion of the unvulcanized tire is molded and vulcanized For a substantially constant volume in at least one portion of the molding cavity, and when applying the uncured elastomeric material to the support, a first curve of the excess volume of elastomeric material material is determined with respect to the available volume in at least one portion of the molding cavity, depending on a predetermined direction, and control the distribution of the volume of elastomeric material over the rigid support in order to essentially correspond to the first curve. 2. The method according to claim 1, in which when controlling the distribution of the volume of elastomeric material over the support, a first set of technical positioning requirements for equipment associated with applying unvulcanized elastomeric material to the support corresponding to the first curve of the excess material volume is determined, and the equipment is moved in accordance with a set of technical requirements. 3. The method according to claim 2, in which when determining the first curve of the excess volume of the material provide a given curve of the excess volume of the material, provide at least a second set of technical requirements for positioning for the equipment, determine the second curve of the excess volume of the material corresponding to the set of technical requirements to positioning, and compare the second curve with a given curve to determine the difference in the distribution of volume between the second curve and a given curve depending on a given direction Nia. 4. The method according to claim 3, in which additionally determine the first cross-sectional profile of at least one section of unvulcanized tires from the second set of technical requirements for positioning. 5. The method according to claim 4, in which the first sectional profile is further modified using differences in the volume distribution between the second curve and the predetermined curve, thereby determining a second sectional profile of at least one portion of the uncured tire. 6. The method according to claim 5, in which when determining the first set of technical requirements for positioning for equipment determine the first set of technical requirements for positioning from at least a second section profile. 7. The method according to any one of claims 2 to 6, wherein the equipment comprises a mechanical manipulator associated with a support. 8. The method according to claim 1, in which when applying the elastomeric material to the support extruded unvulcanized elastomeric material in the form of elongated elements, including elastomeric material. 9. The method according to claim 2 or 8, in which the first set of technical requirements for positioning contains many positioning records, each of the positioning records containing at least spatial coordinates of a given section point of the elongated element. 10. The method according to any one of claims 1 to 3, in which the first, second or predetermined curve of the excess volume of the material represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y. 11. The method according to any one of claims 1 to 3, in which the first, second or predetermined curve of the excess material volume represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y. 12. The method according to any one of claims 1 to 3, in which the first, second or predetermined curve of the excess volume of the material is the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ . 13. The method according to any one of claims 1 to 3, in which the first, second or predetermined curve of the excess volume of the material is the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ . 14. The method according to claim 1, wherein the predetermined direction is the radial direction. 15. A method for controlling the application of unvulcanized elastomeric material to a rigid support for manufacturing an unvulcanized tire to be molded and vulcanized in a vulcanizing form, wherein the vulcanizing form and the rigid support form a molding cavity, so that at least one portion of the unvulcanized tire is molded and vulcanized by a substantially constant volume in at least one portion of the molding cavity, which provides the first set of technical requirements for positioning for equipment associated with the application of unvulcanized elastomeric material on the support, provide a sectional profile of at least a portion of the molding cavity, and determine, from the first set of technical requirements for positioning and from the sectional profile of the molding cavity, the first curve of the excess material volume of unvulcanized elastomeric material with respect to to the available volume in the area of the molding cavity, depending on the given direction. 16. The method according to clause 15, in which additionally provide a given curve of the excess volume of the material and compare the first curve with a given curve to determine the difference in the distribution of volume between the first curve and a given curve depending on a given direction. 17. The method according to clause 15 or 16, in which additionally determine the first cross-sectional profile of at least one section of the uncured tire from the first set of technical requirements for positioning. 18. The method according to 17, in which the first sectional profile is further modified using differences in the volume distribution between the first curve and the predetermined curve, thereby determining a second sectional profile of the portion of the unvulcanized tire. 19. The method according to clause 15 or 16, in which the first or predetermined curve of the excess volume of material represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y. 20. The method according to p. 15 or 16, in which the first or predetermined curve of the excess volume of the material represents the following function:

where y is a variable representing a given direction, V _mat (y) is the volume of elastomeric material contained between the control point of the vulcanization form and the value of the variable, V _mold (y) is the volume of the mold cavity contained between the control point and the value of y. 21. The method according to clause 15 or 16, in which the first or predetermined curve of the excess volume of the material represents the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the specified mold cavity, contained between the values of y ₁ , y ₂ . 22. The method according to clause 15 or 16, in which the first or predetermined curve of the excess volume of the material represents the following function:

where y ₁ , y ₂ are two given values of a variable representing a given direction, V _mat (y ₁ , y ₂ ) is the volume of elastomeric material contained between the values of y ₁ , y ₂ , V _mold (y) is the volume of the mold cavity contained between the values of y ₁ , y ₂ . 23. The method according to clause 15, in which the specified direction is the radial direction of the uncured tire.

Images