Method and apparatus for cleaning vulcanization moulds for elastomer material articles

Abstract: In a vulcanization mould (2) for vehicle tyres the rubber blend deposits are cleaned off by the action of one or more laser beams (9) supplied in the form of short-duration and high-energy pulses, which beams cause separation of the rubber blend by effect of the shock wave generated by them and hitting the operating surfaces of the mould (2). Each laser beam (9) is guided by a scanning unit (21a, 21b) mounted on a rotating column (16) for distributing the beam action over the whole circumferential extension of the mould.

Description: The present invention relates to a method and apparatus for cleaning vulcanization moulds for elastomer material articles. More particularly, the method and apparatus in reference especially aim at carrying out a periodical cleaning of the moulds employed in the vulcanization of vehicle wheel tyres. It is known that during the tyre production cycle, and more generally when many articles of elastomer material are to be manufactured, a moulding and vulcanization step is provided in which the article of manufacture initially in a raw state, is closed into a mould and submitted to a combined pressure and temperature action by effect of which the article of manufacture is shaped according to the desired geometrical configuration and definitively consolidated into this geometrical configuration and also into its physico-molecular structure, as a result of a molecular cross-linking in the elastomer material caused by high temperature. It is to note however that during each vulcanization cycle the tyre deposits a very thin rubber layer over the mould surfaces with which it comes into contact. The thickness of this layer becomes increasingly greater as the vulcanization cycles are repeated and therefore, in the long run, it can reach such values that the aesthetical features of the finished tyre are impaired to an unacceptable level and the air vents necessarily provided in the mould walls for ensuring evacuation of the air entrapped between the surface of the article of manufacture to be vulcanized and that of the mould are partly or completely obstructed. Submitting the mould to a careful cleaning action after a certain number of vulcanization cycles becomes therefore necessary. These cleaning operations presently provide that the mould should be removed from the vulcanization press to be submitted to sandblasting and/or washing operations by means of particular chemical agents at the inside of appropriate machines. When dismantling of the mould occurs, the press shall remain inactive over a certain period of time which may have a duration of eight hours, that is a whole work shift, in that a lapse of time is first required for enabling cooling of the mould, followed by another period of time needed by manpower for dismantling of the mould itself, in turn followed by a further period of time for mounting of another mould and pre-heating of the same until achievement of the operating temperature. These periods can be reduced even to a great extent if automatic systems for quick mould release and devices for mould pre-heating are utilized, but in any case dismantling of the mould from the press is required. This does not represent a drawback when the mould needs to be in any case disassembled for being replaced with another mould of different size and/or tread pattern, but it is a very onerous operation when the vulcanization cycle must go on with the same tyre pattern. In this case in fact the expensive "machine stoppage" to which the press is submitted can be avoided only when another identical mould is available for being mounted in place of the one sent to cleaning, and therefore when there is a mould pool having excess pieces with respect to the real production necessities (which represents an expensive solution too). It has been suggested of carrying out cleaning of the mould using a laser light in order to preserve the integrity in time of the work surfaces of the mould, leaving out of consideration actions of the mechanical (abrasion) or chemical (acids and/or solvents) type. This allows to carry out the mould cleaning without dismantling the mould from the vulcanization press thus eliminating all drawbacks resulting therefrom. WO 95/11764 discloses a method and an apparatus for cleaning moulds for forming glass articles that provides for cleaning baths and a photo-ablation phase by using a laser beam that is axially admitted into the mould and diverted onto the inner surface thereof. DE 195 17 218, that was published after the priority date of the present application, discloses a method and an apparatus for cleaning moulds for the vulcanization of tyres that includes a transportable assembly formed by a laser head mounted on an orientable manipulator. WO 94/21418 discloses a method and an apparatus for cleaning vulcanization moulds for elastomer material articles that employs the laser light generated by a transportable source. An optical fiber system, manually controlled by an operator, allows for directing the laser light onto the surfaces to be cleaned. The laser source is movable and more than one optical fiber system can be provided for operating on several near moulding equipment's. With such an arrangement it is difficult to carry out an accurate and controlled cleaning of a mould for vulcanizing tyres. It is an object of the present invention to overcome the limitations and the drawbacks of the prior art. In one aspect, the invention relates to a method of cleaning moulds in a vulcanization press for tires, said mould comprising a lower and an upper coaxial cheek and a plurality of circumferential sectors operatively interposed between said cheeks, said lower and upper cheeks being respectively fastened to a bed and to a movable support of said vulcanization press, said mould exhibiting operating surfaces covered with vulcanized rubber deposits to be removed, comprising the step of arranging a laser unit outside said mould, removing the deposits by effect of at least one laser beam emitted from said laser unit, said method comprising the steps of: a) opening the mould for extracting a vulcanized tyre by moving the sectors radially away from the mould axis and axially shifting, reciprocally away, the upper and lower cheek; b) removably fixing with respect to the opened mould and inside the opened mould, according to a pre-established positioning, an apparatus for cleaning the mould comprising at least one scanning unit having at least one inlet and one outlet port through which the laser beam enters and exits; c) guiding said at least one laser beam radially to the mould from the laser unit to the inside of said mould and guiding said at last one laser beam through reflections axially inside the mould and guiding and moving said at least one laser beam through reflections to the said at least one outlet port so that through said outlet port the laser beam is selectively directed to different areas of the operating surfaces of the mould and is selectively oriented toward either one of said cheek. More particularly, the laser light radiation is transmitted to the mould in the form of electromagnetic energy pulses each localized at a delimited surface area of the mould, to cause separation of the rubber blend adhering to said surface areas by effect of a shock wave generated by each electromagnetic energy pulse. The rubber material removed from said operating surfaces is taken away from the mould by an air stream produced by suction. In an embodiment particularly appropriate to operate on a vulcanization mould for vehicle wheel tyres of the type having two coaxially aligned cheeks and circumferential sectors operatively interposed between said cheeks, the simultaneous action of at least two radiation beams of laser light directed at right angles to each other and pointing to the mould cheeks and sectors respectively, is provided. Advantageously, the mould submitted to the laser light radiation does not need to be dismantled from the vulcanization press. In accordance to a second aspect, the present invention relates to an apparatus for cleaning a vulcanization mould for vehicle tires, said mould comprising two coaxial cheeks and circumferential sectors operatively interposed between said cheeks, said mould exhibiting operating surfaces covered with vulcanized rubber deposits to be removed, said apparatus comprising: a) at least one laser unit arranged outside the mould to emit at least one laser beam; b) guide and movement means comprising at least an outlet port and reflecting elements to direct the at least one laser beam axially to the mould and to deviate the at least one laser beam to the outlet port inside the mould, said guide and movement means being operatively connected with the laser unit to direct the laser beam radially from the laser unit to the inside of the mould; c) a first and a second reflecting elements both inside the opened mould, said first element directing the laser beam along the axis of the mould and said second reflecting element deviating the laser beam to the outlet port; d) said outlet port selectively directing the laser beam to different areas of the operating surfaces of the mould and selectively orienting the laser beam towards either one of said cheeks; e) positioning means, removably fixed to the mould for supporting the guide and movement means according to a pre-established positioning within the mould. Additional advantageous features of the invention are claimed in the dependent claims. In more detail, preferably said laser unit is of the YAG type, which is well known in the laser units art, adapted to emit electromagnetic energy in the form of sequential pulses. In a preferential solution, said guide and movement means comprises at least one optical scanning unit having: an inlet port through which the laser beam enters the optical scanning unit; an outlet port through which the laser beam comes out of the optical scanning unit; a diverting assembly operatively interposed between said inlet port and said outlet port and operable upon command of a central electronic unit to direct said laser beam according to an angle varying within a predetermined range with respect to the axis of the outlet port. Advantageously, the optical scanning unit can be positioned for rotation about the axis of said inlet port to selectively point the outlet port to either one of said cheeks of the vulcanization mould, said outlet port being oriented in a direction substantially perpendicular to the inlet port. An embodiment particularly appropriate to operate on a vulcanization mould for vehicle tyres having two coaxial cheeks and circumferential sectors operatively interposed between said cheeks, comprises at least two of said optical scanning units, the outlet ports of which are directed to the mould cheeks and sectors respectively. Preferentially, at least the optical scanning unit having the respective outlet port oriented towards the mould sectors can be slidably positioned parallelly to the mould axis and preferably the axis of said outlet port can be angled in a range of at least 8° from the orthogonal position relative to the mould axis. Said positioning means may advantageously comprise: a centering ring to be coaxially associated with one cheek of the mould; a bridge element in engagement with said centering ring and extending diametrically to said cheek; a supporting column extending from said bridge element in coaxial relationship with said cheeks. It is also preferably provided that said bridge element be angularly movable about the axis of the supporting column. Advantageously, the supporting column holds the optical scanning unit rotatably about the supporting column axis, so that the laser beam from said outlet port lends itself to be selectively guided along the whole circumferential extension of the mould. In accordance with a further feature of the present invention, the guide and movement means for the laser beam define an optical path of travel having a first length extending along said bridge element, a second length extending parallelly to the supporting column axis and at least one third length extending away from the supporting column for reaching the optical scanning unit through said inlet port. The apparatus in reference can further comprise at least one annular reflecting element coaxially circumscribing a respective mould cheek, and at least one abutment member arranged to act on the mould sectors so as to hold them all at a predetermined distance from said centering ring. Further features and advantages will become more apparent from the detailed description of a preferred and non-exclusive embodiment of a method of cleaning vulcanization moulds for elastomer material articles and an apparatus for putting said method into practice, in accordance with the present invention. This description will be taken hereinafter with reference to the accompanying drawing, given by way of non-limiting example, in which the only figure shows the apparatus of the invention under operating conditions within a vulcanization mould for motor-vehicle tyres, diagrammatically represented in a diametrical sectional view. In the accompanying figure, an apparatus for cleaning vulcanization moulds for elastomer material articles in accordance with the present invention has been generally identified by reference numeral 1. In the described embodiment, apparatus 1 is arranged to carry out cleaning of a mould 2 used in the vulcanization of motor-vehicle tyres. In a manner known per se, this mould 2 has a lower cheek 3a and an upper cheek 3b disposed coaxially and intended for operating on the opposite sidewalls of the tyre being worked, and a plurality of circumferential sectors 4 operatively interposed between the cheeks 3a, 3b to define a raised pattern on the tread band of the tyre itself. Under operating conditions, the lower cheek 3a is fastened to a bed 5 of a vulcanization press, in the central part of which a vulcanization chamber 5a is operatively mounted, which chamber is designed to be inflated with steam under pressure at the inside of the tyre so that said tyre is pushed against the inner walls of the mould 2 and in order to carry out the necessary heat supply for the vulcanization operation. The upper cheek 3b is in turn fastened to a movable support 6 to which an annular element 7 is also connected for operatively engaging the sectors 4 and setting them in motion so that they are axially moved close to or away from the mould axis, during a closing and opening step of the mould 2, respectively. The support 6 and annular element 7 are movable relative to the bed 5 and to each other to alternately cause closing of the mould 2 and opening of same to enable the vulcanized tyre to be extracted and replaced with a new tyre to be vulcanized. All that being stated, the apparatus 1 essentially comprises at least one laser unit 8 arranged to emit at least one laser beam 9, guide and movement means 10 operatively connected with the laser unit 8 to selectively direct the laser beam 9 to different areas of the operating surfaces of the mould 2, as well as positioning means 11 to be removably fastened to the mould 2 to suitably hold the guide and movement means 10 in a predetermined position within the mould itself. In a preferential solution the laser unit 8, only diagrammatically shown since it is commonly available on the market, is of the well known YAG type and is designed to emit two distinct laser beams parallel to each other (shown in the drawing by line 9 alone), each consisting of a sequence of short-duration and high-energy pulses. More particularly, each laser beam preferably has a diameter included between 6 and 12 mm, and is emitted in the form of pulses each having a duration included between 3 and 8 nanoseconds (ns) and an energy included between 300 and 500 microjoules (µJ). The laser beams, initially lying in distinct planes disposed in side by side relation, are intended for following distinct optical paths of travel within the guide and movement means 10 to be directed against the cheeks 3a, 3b and sectors 4 respectively, as better clarified in the following. The positioning means 11 preferably is comprised of a centering ring 12 to be coaxially associated with one of the mould cheeks, preferably the lower one 3a. Preferably, engagement between the centering ring 12 and cheek 3a takes place at an outer perimetric rim 13 of the cheek itself, spaced apart from a perimetric junction wall 14a where junction between said cheek and sectors 4 occurs for confining the inner mould cavity 2 when the mould is in a closed condition. Operatively connected to the centering ring 12 is a bridge element 15 preferably of a tubular structure and extending diametrically above the lower cheek 3a. Standing from the bridge element 15 is an internally-hollow supporting column 16 in coaxial relationship with the cheeks 3a, 3b. In a preferential solution, the positioning means 11 further comprises at least one abutment member 30 fastened to the centering ring 12 and arranged to interfere with the lower ends of sectors 4 so as to hold them at a given distance from the ring itself. This abutment member 30 can be formed of three or more supporting elements 31 carrying an annular rest element 32 adapted to act against sectors 4. The guide and movement means 10 comprising a first, a second and a third reflecting elements 17a, 17b, 17c for example, guide a corresponding one of the beams 9 emitted from the laser unit 8 in an optical path of travel having a first length 18 extending longitudinally in the bridge element 15, a second length 19 extending within the column 16 parallelly to the axis of the latter, and a third length 20a, 20b extending in a perpendicular direction away from the supporting column itself. In the embodiment shown the two beams 9 admitted to the first length 18 directly from unit 8, are both deviated on the second length 19 by the first reflecting element 17a. Along the second length 19 the mutually separated beams fetch the second and third reflecting elements 17b, 17c respectively, that divert them along the respective third lengths 20a, 20b extending radially of the column 16 axis in respectively opposite directions. The third lengths 20a, 20b terminate at a respective first and second optical scanning unit 21a, 21b upon the action of which the laser beams are selectively oriented towards different areas of the operating mould surfaces. To this end, each of the optical scanning units 21a, 21b, only briefly described in that it is similar to, or can be easily deduced from operatively similar units commonly available on the market (the galvanometric XY Modules from SCANLAB, for example), essentially has a diverting assembly housed within a box-shaped structure 22 in which an inlet port 23 is formed which is in alignment with the third length 20a, 20b to enable the laser beam to enter the scanning unit 21a, 21b, as well as an outlet port 24 through which the laser beam comes out of said scanning unit. In a manner known per se each diverting assembly not shown in the figure, essentially consists of an assembly of mirrors and/or prisms movable upon command of respective galvanometric motors managed by a central electronic unit so as to direct the respective laser beam according to an angle included within a predetermined range about the axis of the outlet port 24. The deviation angle of the laser beam can take any value within a given range (a cone of an amplitude at least equal to 25°) fixed by the optical and mechanical features of the components of the optical diverting assembly 21a, 21b and/or in connection with specific requirements. In conclusion, the maximum deviation angle of the laser beam coming out of the optical diverting assembly 21a, 21b defines a reach identified by R having said cone or conoid configuration for example, delimiting a circular or ellipsoidal reach on the operating mould 2 surfaces within which the beam can be directed to any area of an amplitude corresponding to the diametric size of the beam itself, obviously taking care to keep said beam always focused in order to maximize the instantaneous power transmitted to said area. As clearly shown in the accompanying figure, the first and second optical scanning units 21a, 21b are oriented in a manner enabling each of them to direct its own laser beam to the cheeks 3a, 3b and the sectors 4 of the mould 2 respectively. The first optical scanning unit 21a can be rotatably positioned about the axis of its inlet port 23 so as to carry out an angular rotation in the range of 180°, to selectively orient the outlet port 24, and consequently the laser beam, towards either one of the cheeks 3a, 3b. Rotation of the first optical scanning unit 21 about the axis of the inlet port 23 can be achieved by a stepping motor 25 for example, or another type of motor operating on a ring gear 25a integral with the scanning unit itself, said ring gear being rotatably in engagement with a sleeve 25b radially projecting from column 16. Usually, the size and geometrical conformation of the cheeks 3a, 3b are of such a nature that the radial extension of each of them is completely contained within the reach R of the first scanning unit 21a: in the case of cheeks radially extended more than the maximum diameter of said reach R the possibility of moving the scanning unit 21a in a direction orthogonal to the supporting column 16 axis can be advantageously provided. In order to ensure the laser beam action also over areas of the cheeks 3a, 3b that do not directly face the scanning unit 21a, the presence of at least one annular reflecting element 26 coaxially circumscribing the cheek itself may be further provided. In the embodiment shown, such a reflecting element 26, shown in chain line in the drawing, is linked to the upper part of sectors 4 to suitably reflect the laser beam on a junction surface 14b perimetrically exhibited by the upper cheek 3b. This junction surface 14b, oriented parallelly to the geometrical axis of the mould 2, is subjected to get dirty due to the rubber material penetrating between the sectors 4 and the cheek itself during the moulding step of the tyre, and therefore must be periodically cleaned as well. Obviously, a similar annular reflecting element may be also coaxially associated with the lower cheek 3a to facilitate cleaning of the junction surface 14a thereof. The second optical scanning unit 21b intended for cleaning sectors 4 is preferably associated with column 16 in such a manner that it can slide along the same to be positioned parallelly to the geometrical axis of the mould. In more detail, the second scanning unit 21b can be selectively positioned, upon command of one or more actuators not shown as feasible in a manner known per se, between a first operating position in which it is disposed relatively close to the bed 5 and a second operating position in which it is spaced apart from the bed itself, as shown in phantom lines. Still more preferentially, the second optical scanning unit 21b too is mounted to advantage on column 16 in a manner enabling the orientation at least of the outlet port 24 axis to be varied with respect to the plane containing the column axis, within a circular range of an amplitude equal to at least 8° relative to the direction perpendicular to said plane, so that the axis of the laser beam reach can be inclined with respect to the geometrical axis of said mould within said values. Clearly, the possibility of varying the inclination of the axis of the laser beam outlet port can be also applied to the first optical scanning unit 21a, in combination with or alternatively to the possibility of making said unit carry out a radial translation relative to the axis of the supporting column 16. The selective positioning of the second scanning unit 21b in the first and second operating positions and according to different inclinations enables the laser beam coming out of same to reach the operating surfaces of the sectors according to different angles, so that it is eliminated the risk that some areas may not be conveniently reached by the laser beam by effect of the shadow created by the presence of the number of fins and/or ribs usually arranged on the sectors 4 in order to form the raised thread pattern of the tyre tread band. In order to enable the laser beam to act over the whole circumferential extension of the cheeks 3a, 3b and sectors 4, the optical scanning units 21a, 21b are also provided to be positioned for rotating about the geometrical axis of the mould, so that the laser beams coming out of the respective outlet ports 24 lend themselves to be selectively positioned along the whole circumferential extension of the mould itself. More particularly, the supporting column 16 is provided to be rotatably in engagement with the bridge element 15 and operable in rotation, e.g. upon command of a stepping motor 27 acting on a toothed pulley through a driving belt 27b. Preferably, rotation of the supporting column 16 takes place through angles of 180° in opposite directions relative to an intermediate reference position, in order to avoid the difficulties that a continuous rotation greater than 180° could involve with reference to the electrical connections necessarily arranged for operation and movement of the scanning units 21a, 21b. For the purpose of avoiding that the inevitably produced shadow of the bridge element 15 may inhibit an efficient cleaning of some areas in the lower cheek 3a, the bridge element is advantageously provided to be angularly movable about the axis of the supporting column 16. The angular rotation of the bridge element 15 preferably included within 5° and 15° can be obtained for example by a motor, not shown, acting on a toothing 28 peripherally carried by the bridge element itself. Operation of the apparatus in reference described above mainly as regards structure, is as follows. The mould being in its completely open condition, the apparatus 1 is mounted on the vulcanization press and engagement between the centering ring 12 and the press bed 5 occurs coaxially with the lower cheek 3a. When mounting has been completed, the annular element 7 carrying sectors 4 is lowered towards the bed 5 until the sectors come to rest on the annular element 32 of the abutment member 30. At this point the laser unit 8 and optical scanning units 21a and 21b are activated, so that the laser beams are suitably conducted onto the operating surfaces of one of the cheeks 3a, 3b, the upper cheek 3b for example, and onto sectors 4. At the points where the operating surfaces of the mould 2 are hit by the laser beam, each energy pulse carried by said beam causes a shock wave by effect of which detachment of the encrusting thin layer of vulcanized rubber deposited on the mould metal surfaces is caused. This detachment is likely to be due to the fact that, since metal and rubber have different physical features and, in particular, different moduli of elasticity, they react to the shock wave with different resonances that exactly cause separation of the rubber material from the metal surface. Movement of the laser beam by the corresponding scanning unit 21a, 21b enables the action of the beam itself to be homogeneously distributed over the whole extension of the operating mould surfaces, within the reach R of the unit itself. Upon the action of the rotation motor 27 acting on the supporting column 16, the scanning units 21a, 21b are by turns rotated about the geometrical axis of the mould 2, in a stepping or substantially continuous movement, depending on requirements, until the action of the laser beams has been distributed over the whole circumferential extension of the cheek 3b and sectors 4. At this point the first optical scanning unit 21a is rotated through 180° about the axis of its own inlet port 23 to direct the laser beam towards the lower cheek 3a, or vice versa. The second scanning unit 21b in turn is shifted from the first to the second operating position, or vice versa, so that it is ready to operate on sectors 4 according to an axial positioning different from the preceding one. In each operating position, the reach R axis of the laser beam will be caused to vary depending on specific requirements so that each point of the sector surface can be surely reached by the laser beam with the expected inclination and intensity. Therefore the action of the laser beam is distributed over the whole circumferential extension of the lower cheek 3a and sectors 4, in the same manner as previously described. At the end of cleaning or during the cleaning step, the vulcanized rubber fragments coming off the mould 2 can be easily removed by an air stream produced by a suction device for example, that can indifferently be either of the portable manual type or the automatic type, directly installed on the vulcanization press or the cleaning apparatus 1. The present invention achieves important advantages. It is pointed out in fact that the method and apparatus of the invention enable a perfect cleaning of the vulcanization mould to be carried out in a maximum period of time of approximately 2 to 3 hours. This cleaning time can be further reduced by arranging more than two scanning units simultaneously operating on the mould sectors and cheeks. In this connection it is to note that the method and apparatus of the invention also enable the simultaneous cleaning of several moulds, e.g. cleaning of one pair of moulds mounted on presses provided with two mould seatings operable in parallel. In this case each mould only needs to be provided with its own positioning device, as all the positioning devices can be supplied from a single laser unit 8 emitting the necessary number of laser beams subsequently conducted to the different positioning devices by appropriate reflecting and guide means. In addition, the invention enables the mould cleaning process to be carried out while keeping said mould directly mounted on the press, without waiting for cooling of same, the mould being immediately available for a new operating cycle as soon as the cleaning operation is over. It should be also noted that the laser beam enables a perfect cleaning of the moulds to be carried out without altering the metal surface of same, which on the contrary happens with conventional cleaning processes by sandblasting that inevitably bring about a certain wear in the moulds. With reference to the use of solvents or other washing chemicals according to the known art, the invention also eliminates all toxicity and pollution problems connected with the use and disposal of chemical substances after use. Another advantage of the invention resides in that the same apparatus can be employed for indifferently cleaning moulds of cast iron, alluminium or other materials, thereby eliminating the necessary provision of different washing and/or sandblasting agents specifically required in the known art for carrying out cleaning of each specific mould type. The method of the invention also enables cleaning of the mould to be enhanced as even the innermost areas of the vent ducts can be reached, which was practically impossible with the traditional cleaning methods by washing and/or sandblasting. In the light of the advantages achieved by the present invention, a more frequent cleaning of the moulds than in the known art becomes convenient, which will bring about an improvement in the quality evenness of the finished product and a reduction in the machine shop rejections.

Claims: A method of cleaning moulds in a vulcanization press for tires, said mould comprising a lower and an upper coaxial cheek and a plurality of circumferential sectors operatively interposed between said cheeks, said lower and upper cheeks being respectively fastened to a bed and to a movable support of said vulcanization press, said mould exhibiting operating surfaces covered with vulcanized rubber deposits to be removed, comprising the step of arranging a laser unit outside said mould, removing the deposits by effect of at least one laser beam emitted from said laser unit, said method comprising the steps of: a) opening the mould for extracting a vulcanized tyre by moving the sectors radially away from the mould axis and axially shifting, reciprocally away, the upper and lower cheek; b) removably fixing with respect to the opened mould and inside the opened mould, according to a pre-established positioning, an apparatus for cleaning the mould comprising at least one scanning unit (21a, 21b) having at least one inlet and one outlet port through which the laser beam enters and exits; c) guiding said at least one laser beam radially to the mould from the laser unit to the inside of said mould and guiding said at last one laser beam through reflections axially inside the mould and guiding and moving said at least one laser beam through reflections to the said at least one outlet port so that through said outlet port the laser beam is selectively directed to different areas of the operating surfaces of the mould and is selectively oriented toward either one of said cheek. A method according to claim 1, characterized in that it provides the simultaneous acting of at least two laser light beams directed onto the surfaces respectively of the checks (3a, 3b) and of the sectors (4) of said mould (2). A method according to claim 1, characterized in that the vulcanized rubber material removed from said operating surfaces is evacuated from the mould (2) by an air stream produced by suction. A method according to claim 2 or 3, characterized in that each of said laser beams is emitted in the form of pulses and has a diameter included between 6 and 12 mm. A method according to claim 2 or 3, characterized in that each pulsating laser beam has a duration included between 3 and 8 nanoseconds (ns) and an energy included between 300 and 500 microjoules (µJ). An apparatus for cleaning a vulcanization mould for vehicle tires, said mould comprising two coaxial cheeks (3a, 3b) and circumferential sectors (4) operatively interposed between said cheeks (3a, 3b), said mould (2) exhibiting operating surfaces covered with vulcanized rubber deposits to be removed, said apparatus comprising: a) at least one laser unit (8) arranged outside the mould to emit at least one laser beam (9); b) guide and movement means (10) comprising at least an outlet port and reflecting elements to direct the at least one laser beam axially to the mould and to deviate the at least one laser beam to the outlet port inside the mould, said guide and movement means (10) being operatively connected with the laser unit (8) to direct the laser beam (9) radially from the laser unit to the inside of the mould; c) a first and a second reflecting elements both inside the opened mould, said first element directing the laser beam along the axis of the mould and said second reflecting element deviating the laser beam to the outlet port; d) said outlet port selectively directing the laser beam to different areas of the operating surfaces of the mould and selectively orienting the laser beam towards either one of said cheeks; e) positioning means (11), removably fixed to the mould (2) for supporting the guide and movement means (10) according to a pre-established positioning within the mould. An apparatus according to claim 6 characterized in that said positioning means (11) comprises: a centering ring (12) to be coaxially associated with one cheek (3a) of the mould (2); a bridge element (15) in engagement with said centering ring (12) and extending diametrically to said cheek (3a); a supporting column (16) extending from said bridge element (15) in coaxial relationship with said cheeks (3a, 3b). An apparatus according to claim , 6 characterized in that said guide and movement means (10) comprises at least one optical scanning unit (21a, 21b) having: one inlet port (23) through which the laser beam (9) enters the optical scanning unit (21a, 21b); one outlet port (24) through which the laser beam (9) comes out of the optical scanning unit (21a, 21b); a diverting assembly operatively interposed between said inlet port (23) and said outlet port (24) and operable upon command of a central electronic unit to direct said laser beam (9) according to a predetermined angle with respect to the axis of the outlet port (24). An apparatus according to claim 8, characterized in that said optical scanning unit (21a) can be positioned for rotation about the axis of said inlet port (23) to selectively point the outlet port (24) to either one of said cheeks (3a, 3b) of the vulcanization mould (2). An apparatus according to claim 8, characterized in that said optical scanning unit (21b) has the respective outlet port (24) oriented towards the mould sectors (4). An apparatus according to claim 8, characterized in that said optical scanning unit (21b) can be slidably positioned parallelly to the geometrical axis of the mould (2). An apparatus according to claim 8, characterized in that it comprises at least two of said optical scanning units (21a, 21b) the outlet ports (24) of which are oriented towards the mould cheeks (3a, 3b) and sectors (4), respectively. An apparatus according to claim 6, characterized in that said laser source (8) is capable of emitting electromagnetic energy in the form of subsequent pulses. An apparatus according to claim 7 , characterized in that said bridge element (15) is angularly movable about the axis of the supporting column (16). An apparatus according to claim 8 , characterized in that said guide and movement means (10) defines an optical path of travel having a first length (18) extending along said bridge element (15), a second length (19) extending parallelly to the supporting column (16) axis and at least one third length (20a, 20b) extending away from the supporting column (16) for reaching the optical scanning unit (21a, 21b) through said inlet port (23). An apparatus according to claim 7 , characterized in that it further comprises at least one annular reflecting element (26) coaxially circumscribing a respective cheek (3b) of the mould (2). An apparatus according to claim 7, characterized in that said positioning means (11) comprises at least one abutment member (30) arranged to act on said sectors (4) to sustain them at a predetermined distance from said centering ring (12).

Inventors: BENEA PAOLO, MANCOSU FEDERICO, BENEA, PAOLO, MANCOSU, FEDERICO
Applicants: PIRELLI, PIRELLI PNEUMATICI SOCIETA PER AZIONI
Application year: 1997
Main classification: B29C33
IPC codes: B23K26, B29C33, B29C35, B08B7, B29L30, B29K21, B29K105