Method and equipment for controlling a manufacturing process of a component of a tyre for vehicle wheels

Abstract

A method and equipment for controlling a manufacturing process of a component of a tire for vehicle wheels, wherein at least one continuous elongated element fed by a supplying member is placed on a forming support by means of at least one pressing member active on the at least continuous elongated element along an application direction. During the manufacturing of the component of the tire, at successive sampling times T.sub.i, the value P.sub.i of a quantity indicative of the position of the pressing member is acquired along the application direction, where i is an integer greater than or equal to 1, T.sub.i=i*1/f, and f is the sampling frequency.

Claims

1. A method for controlling a manufacturing process of a component of a tire for vehicle wheels, wherein at least one continuous elongated element fed by a supplying member is placed on a forming support by means of at least one pressing member active on said at least one continuous elongated element along an application direction, comprising, during the manufacturing of the component of the tire: a) acquiring at successive sampling times T.sub.i, a value P.sub.i of a quantity indicative of a position of the pressing member along the application direction, where i is an integer greater than or equal to 1, T.sub.i=i*1/f, and f is a sampling frequency and, at each sampling time T.sub.i; b) determining a difference .sub.i in absolute value between the value of said quantity P.sub.i, at the sampling time T.sub.i, and a value P.sub.i1 of said quantity at the previous sampling time T.sub.i1; c) determining a value of a mobile sum S.sub.i, of M addends with M greater than or equal to 2 and i greater than or equal to M, the M addends representing differences .sub.i, .sub.i1, . . . .sub.iM+1, at a current sampling time T.sub.i, and at previous M1 sampling times T.sub.i1, . . . .sub.iM+1; and d) comparing the value of the mobile sum S.sub.i, determined with at least one threshold value, wherein, if the value of the mobile sum S.sub.i, is greater than said at least one threshold value, at least one of the following is performed: generating a warning and/or alarm signal; checking for a possible presence of a deposition anomaly of the continuous elongated element on the forming support; checking for a possible need to discard the tire with the component being manufactured; and automatically stopping the manufacturing process.

2. The method according to claim 1, wherein said at least one threshold value provides for a first threshold value that is less than a second threshold value.

3. The method according to claim 2, wherein, if the value of the mobile sum S.sub.i is greater than the first threshold value and less than the second threshold value, at least one of the following is performed: generating a warning signal; checking for a possible presence of a deposition anomaly of the continuous elongated element on the forming support; checking for a possible need to discard the tire with the component being manufactured; and stopping the manufacturing process at the end of the manufacturing of the component being manufactured.

4. The method according to claim 2, wherein, if the value of the mobile sum S.sub.i is greater than the second threshold value, at least one of the following is carried out: generating an alarm signal; giving for sure a presence of a deposition anomaly of the continuous elongated element on the forming support; discarding the tire with the component being manufactured; and immediately stopping the manufacturing process.

5. The method according to claim 1, wherein the number M of addends of the mobile sum is 3 or 4.

6. The method according to claim 1, comprising comparing the value of the mobile sum S.sub.i with said at least one threshold value if the value of the mobile sum S.sub.i is greater than a value taken, at the current sampling time T.sub.i, by a parameter S.sub.max that is representative of a maximum value reached by the mobile sum S.sub.i while the tire component is being manufactured.

7. The method according to claim 6, comprising, after c) determining a value of a mobile sum S.sub.i of M addenda, and before d) comparing the value of the mobile sum S.sub.i, comparing the current value of the mobile sum S.sub.i with the current value taken by the parameter S.sub.max.

8. The method according to claim 7, wherein, if the value of the mobile sum S.sub.i is greater than the current value taken by the parameter S.sub.max, assigning the parameter S.sub.max the current value of the mobile sum S.sub.i.

9. The method according to claim 7, wherein, if the value of the mobile sum S.sub.i is less than or equal to the current value taken by the parameter S.sub.max, leaving the current value taken by the parameter S.sub.max unchanged.

10. The method according to claim 8, comparing the current value taken by the parameter S.sub.max with said at least one threshold value.

11. The method according to claim 10, wherein, if the current value taken by the parameter S.sub.max is greater than said at least one threshold value, at least one of the following is performed: generating a warning and/or alarm signal; checking for a possible presence of a deposition anomaly of the continuous elongated element on the forming support; checking for a possible need to discard the tire with the component being manufactured; and automatically stopping the manufacturing process.

12. The method according to claim 2, wherein the second threshold value is between about 130% and about 150% of the first threshold value.

13. The method according to claim 1, wherein the manufacturing of the component of the tire comprises supplying the continuous elongated element on the forming support for at least one first complete rotation of the forming support about its own rotation axis.

14. The method according to claim 1, wherein the sampling frequency f is greater than or equal to about 75 Hz.

15. The method according to claim 1, wherein said component of the tire is made from elastomeric material not reinforced with cords.

16. The method according to claim 1, wherein from a) to d) are repeated for each component of the tire.

17. The method according to claim 15, wherein from a) to d) are repeated for each component of the tire made from elastomeric material not reinforced with cords.

18. Equipment for controlling a manufacturing process of a component of a tire for vehicle wheels, comprising an apparatus for manufacturing said tire component and at least one processor operatively associated with said apparatus, said apparatus comprising: a supplying member configured to place a continuous elongated element on a forming support; a pressing member active on said continuous elongated element along an application direction so as to press said continuous elongated element on said forming support; and a detection device operatively coupled with said pressing member and configured to supply a quantity indicative of a position of the pressing member along the application direction during deposition of said continuous elongated element on said forming support; wherein said at least one processor is configured to: a) acquire, at successive sampling times T.sub.i, a value P.sub.i of said quantity supplied by the detection device, where i is an integer greater than or equal to 1, T.sub.i=i*1/f, and f is a sampling frequency and, at each sampling time T.sub.i: b) determine a difference .sub.i in absolute value between the value P.sub.i of said quantity at the sampling time T.sub.i, and a value P.sub.i1 of said quantity at the previous sampling time T.sub.i1; c) determine a value of a mobile sum S.sub.i of M addends with M greater than or equal to 2 and i greater than or equal to M, the M addends representing differences .sub.i, .sub.i1, . . . .sub.iM+1, at a current sampling time T.sub.i and at previous M1 sampling times .sub.Ti1, . . . T.sub.iM+1; and d) compare the determined value of the mobile sum S.sub.i with at least one threshold value, wherein, if the value of the mobile sum S.sub.i is greater than said at least one threshold value, at least one of the following is performed: generating a warning and/or alarm signal; checking for a possible presence of a deposition anomaly of the continuous elongated element on the forming support; checking for a possible need to discard the tire with the component being manufactured; and automatically stopping the manufacturing process.

19. The equipment according to claim 18, wherein said at least one processor is configured to generate a warning and/or alarm signal.

20. The equipment according to claim 18, wherein said at least one processor is configured to automatically stop the apparatus for manufacturing said tire component.

21. The equipment according to claim 18, wherein said detection device is a linear transducer.

22. The equipment according to claim 18, wherein said pressing member comprises a roller adapted to rotate about a rotation axis thereof.

23. The equipment according to claim 22, wherein said pressing member comprises a support device of said roller configured so as to move said roller according to a linear motion along said application direction.

24. The equipment according to claim 23, wherein said detection device is a linear transducer operatively coupled with said support device, so as to move according to a linear motion along said application direction or a direction parallel to said application direction.

25. The equipment according to claim 23, wherein said support device of said roller comprises an air piston active on said roller.

26. The equipment according to claim 22, wherein said roller has a diameter between about 40 mm and about 60 mm.

27. The equipment according to claim 18, wherein said at least one processor is situated at least partially at the apparatus for manufacturing said tire component.

28. The equipment according to claim 18, wherein said at least one processor is situated, at least in part, in a remote location with respect to the apparatus for manufacturing said tire component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the present invention will be made clear from the following detailed description of some illustrative embodiments thereof, provided solely as non-limiting examples, said description being made with reference to the attached drawings, in which:

(2) FIG. 1 shows a schematic perspective view of a preferred embodiment of equipment according to the invention;

(3) FIG. 2 schematically shows an example of the variation of the position of the roller of the apparatus comprised in the equipment of FIG. 1, along an application direction A, during the manufacturing of a tire component;

(4) FIG. 3 schematically shows a flow chart of a preferred embodiment of an algorithm that can be used to carry out the control method of the invention;

(5) FIGS. 4 and 5 schematically show the results obtained by the Applicant in the presence and in the absence, respectively, of deposition anomalies, carrying out the algorithm of FIG. 3;

(6) FIGS. 6 and 7 show two examples of positioning of the roller (down spatial frame) at the sampling times T.sub.i (top time frame) with respect to a plan development of the surface of the forming support 2 with geometric irregularities due to excess or lack of material, for values of the peripheral speed of the forming support respectively equal to 1 m/s and 2 m/s.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows equipment 100 for controlling a manufacturing process of a component of a tire for vehicle wheels, comprising an apparatus 1 for manufacturing said tire component and at least one processor 10 operatively associated with a said apparatus 1.

(8) More specifically, the apparatus 1 is part of a work station (not shown) of a tire production plant (not shown) of the type described above, in which the production of a tire takes place in a plurality of work stations through an automated and substantially continuous process, in other words at least without intermediate storage of semi-finished products made from elastomeric material not reinforced with cords. In such a process, structural components of the tire made from elastomeric material not reinforced with cords (for example liner, under-liner, sidewalls, tread band, inserts made from elastomeric material, etc.) are made directly on a forming support 2 from a continuous elongated element 3.

(9) The forming support 2 is preferably a substantially toroidal or cylindrical rigid support.

(10) The apparatus 1 comprises a supplying member 4 configured to deposit the continuous elongated element 3 on the forming support 2. In the embodiment illustrated in FIG. 1, the supplying member 4 is in the form of an extruder (only partially shown) equipped with an extrusion head 5 adapted to supply the continuous elongated element 3.

(11) During the manufacturing of a tire component, the continuous elongated element 3 is fed substantially continuously by the aforementioned supplying member 4, which preferably maintains a flow rate comprised between about 2 cm.sup.3/s and about 50 cm.sup.3/s, more preferably between about 5 cm.sup.3/s and about 40 cm.sup.3/s. Said values regulate the rotation speed of the forming support 2 about its own rotation axis, said speed preferably varying between about 90 and about 120 revolutions per minute. Preferably, the peripheral speed of the forming support 2 is at least equal to about 0.5 m/s and less than about 5 m/s.

(12) The apparatus 1 also comprises a pressing member 6 configured so as to press the continuous elongated element 3 on the forming support 2 along an application direction A. In the illustrated preferred embodiment, the application direction A forms a predetermined acute angle with the radial relative to the forming support 2 at the contact point between the pressing member 6 and the forming support 2. In the illustrated preferred embodiment, the pressing member 6 comprises a roller 8 and a support device 7 of the roller 8. The support device 7 is configured so as to move the roller 8 according to a linear motion along the application direction A. The roller 8 is also hinged to the support device 7 so as to be able to rotate about a respective pivot axis B-B.

(13) The roller 8 acts as a pressing element for the deposition of the elongated element 3 on the forming support 2. The support device 7 comprises, for example, an air piston active on said roller 8 configured so as to keep it pressed against the forming support 2 along the application direction A.

(14) The roller 8 preferably has a diameter comprised between about 40 mm and about 60 mm, preferably equal to about 50 mm.

(15) The apparatus 1 also comprises a linear transducer 9 operatively coupled with the pressing member 6. The linear transducer 9 is configured to provide said at least one processor 10 with a quantity indicative of the position of the roller 8 along said application direction A during the deposition of said continuous elongated element 3 on the forming support 2.

(16) Said at least one processor 10 can be located at least in part in the work station where the apparatus 1 is located and/or at least in part in a remote location.

(17) Said at least one processor 10 can, for example, comprise a Programmable Logic Controller (PLC).

(18) As already explained above, during the deposition of the continuous elongated element 3 on the forming support 2, the position of the roller 8 along the application direction A undergoes continuous oscillations that depend on surface irregularities that the roller 8 encounters on the forming support 2. Such irregularities can derive from deposition anomalies or be structural, in other words intrinsically linked to the deposition process.

(19) An example of such oscillations is schematically shown in FIG. 2, where the variation of the displacement s of the roller 8 along the application direction A is illustrated as a function of time t during the manufacturing of said tire component. The solid and broken lines show the variation of the displacement of the roller 8 in a situation of absence and presence, respectively, of deposition anomalies. The circled part highlights the variation of the displacement s in the presence of deposition anomalies.

(20) Said at least one processor 10 is configured to identify possible deposition anomalies of the continuous elongated element 3 on the forming support 2 during the manufacturing of said tire component in the work station.

(21) In particular, said at least one processor 10 comprises hardware and/or software and/or firmware elements configured to carry out the control method according to the invention during the manufacturing of said tire component in the work station. Such a method provides to acquire, at successive sampling times T.sub.i, the value P.sub.i of the quantity supplied by the linear transducer 9, indicative of the position of the roller 8 along the application direction A, where i is an integer greater than or equal to 1, T.sub.i=i*1/f and f is the sampling frequency. The method also provides to determine, at each sampling time T.sub.i: the difference .sub.i in absolute value between the value of said quantity P.sub.i at sampling time T.sub.i and the value P.sub.i1 of said quantity at the previous sampling time T.sub.i1, setting P.sub.0 equal to a predetermined value (for example zero) at time T.sub.i=0; and the value of a mobile sum S.sub.i of M addends with M greater than or equal to 2 and i greater than or equal to M, the M addends representing said differences .sub.i, .sub.i1, . . . .sub.iM+1, at the current sampling time T.sub.i and at the previous M1 sampling times T.sub.i1, . . . T.sub.iM+1.

(22) The mobile sum at the sampling time T.sub.i is defined by the following relationship:

(23) $S_i=\underset{j=i-M+1}{\overset{j=i}{.Math.}}{}_j$

(24) The method also provides to compare the value of the mobile sum S.sub.i determined with at least one threshold value.

(25) The differences .sub.i are determined in absolute value (in other words by adding always positive values irrespective of the direction of the displacements) so as to amplify the value of the parameter S.sub.i.

(26) FIG. 3 shows a flow chart of an algorithm that can be used to carry out the control method of the invention, according to a preferred embodiment.

(27) Preferably, said component of the tire is made from elastomeric material not reinforced with cords.

(28) Preferably, the algorithm is repeated for each component of the tire.

(29) More preferably, the algorithm is repeated for each component of the tire made from elastomeric material not reinforced with cords manufactured in the work station.

(30) The algorithm starts at block 300, at the stat of the manufacturing of each tire component. At block 301 the values taken up by two parameters S.sub.i, S.sub.max are zeroed, the parameter i is set equal to 1 and the number of addends M of the mobile sum S.sub.i is set.

(31) At block 302 it is checked whether the manufacturing process of the tire component has ended. In the affirmative case, at block 312 it is checked whether in the process just ended a warning signal has been generated. In the positive case, at block 311 the manufacturing process in the work station is interrupted. This can allow, for example, an operator to verify the possible presence of a deposition anomaly of the continuous elongated element 3 on the forming support 2 and the possible need to discard the tire with the component being manufactured. The algorithm ends at block 313 to then start again with the manufacturing of the component for another tire.

(32) If at block 302 the manufacturing process of the tire component has not ended, at block 303, the value of the parameter i is set to the value i+1 (i=i+1). Thereafter, if i is greater than or equal to M the process proceeds with block 304, otherwise block 303 (i=i+1) is carried out again, and such an operation is then repeated until i is greater than or equal to M.

(33) At block 304 the parameter S.sub.i is set to the value of the mobile sum at sampling time T.sub.i, determined through the relationship described above. At block 305 the current value of the mobile sum S.sub.i is compared with the current value of the parameter S.sub.max. If the current value of the mobile sum S.sub.i is less than or equal to the current value of the parameter S.sub.max, the algorithm goes back to block 302. If the current value of the mobile sum S.sub.i is greater than the current value of the parameter S.sub.max, at block 306 the parameter S.sub.max is assigned the current value of the mobile sum S.sub.i. The value taken up by the parameter S.sub.max is therefore representative of the maximum value reached by the mobile sum during the manufacturing of the tire component.

(34) At block 307 the current value taken up by the parameter S.sub.max is compared with two threshold values Th1 and Th2, with Th1<Th2. If the current value taken up by the parameter S.sub.max is greater than the first threshold value Th1 and less than the second threshold value Th2, at block 308 a warning signal is generated and the algorithm goes back to block 302. The warning signal can, for example, provides that an indicator light is switched on at the apparatus 1.

(35) At block 309 the current value taken up by the parameter S.sub.max is compared with the second threshold value Th2. If the current value taken up by the parameter S.sub.max is not greater than the second threshold value Th2, the algorithm goes back to block 302. If the current value taken up by the parameter S.sub.max is greater than the second threshold value Th2, in block 310 an alarm signal is generated and at block 311 the manufacturing of the tire component is stopped immediately. The algorithm then ends at block 313.

(36) The alarm signal can provides, for example, that both the indicator light and an alarm siren are switched on at the apparatus 1. At this point an operator can, for example, give for sure the presence of a deposition anomaly of the continuous elongated element 3 on the forming support 2 and decide to discard the tire with the component being manufactured. This advantageously makes it possible to avoid waste of material and unproductive use of the machinery of the production plant and to ensure ever greater quality levels in the tires manufactured.

(37) FIGS. 4 and 5 schematically show (not to scale) the results obtained by the Applicant in the presence and absence, respectively, of deposition anomalies, carrying out the algorithm of FIG. 3 and using: a sampling frequency of 100 Hz, a feeding flow rate of the continuous elongated element 3 of about 35 cm.sup.3/s, a peripheral speed of the forming support of about 2 m/s, number M of addends equal to 4, first threshold value Th1 equal to 8 mm, second threshold value Th2 equal to 12 mm, diameter of the roller 8 equal to about 50 mm.

(38) In such figures, the curve G represents the feeding speed of the continuous elongated element 3, the curve F represents the instantaneous position P.sub.i of the roller 8 along the application direction A, the curve D represents the instantaneous value of the mobile sum S.sub.i, and the curve E represents the instantaneous value of the parameter S.sub.max.

(39) As can be seen in both figures, the curve of the parameter S.sub.max (curve E) continually rises, until the maximum is reached within the production cycle of the tire component in progress. In the cases analysed of FIGS. 4 and 5 the parameter S.sub.max respectively reached the peak value of 12 mm (above the second threshold value Th2) and of 2.8 mm (in other words below both threshold values Th1 e Th2).

(40) Other simulations carried out by the Applicant showed peak values of the parameter S.sub.max greater than 8-9 mm in the case of presence of deposition anomalies and below 4-5 mm, in the case of absence of deposition anomalies (such values depend on the type of component in formation, for example for the tread band the values are higher, for the under-layer the values are lower). The Applicant has therefore experimentally found that it is possible to discriminate very clearly anomalous deposition cycles from regular cycles, through a suitable definition of the threshold values Th1 and Th2.

(41) It should also be observed that in the case of FIG. 4 the parameter S.sub.max reaches its peak value of 12 mm at instantaneous values of the difference .sub.i and of the position P.sub.i of the roller 8, along the application direction A, that are little evident. This shows that the mobile sum S.sub.i advantageously makes it possible to correctly identify the deposition anomalies also for instantaneous values of .sub.i and P.sub.i that in themselves are not very significant.

(42) In particular, the use of the mobile sum of several addends advantageously makes it possible to emphasise the value of the variations in position undergone by the roller 8 along the application direction A and to increase the ability to discriminate geometric irregularities due to deposition anomalies from the structural ones, intrinsically linked to the deposition process of the continuous elongated element 3.

(43) Moreover, the use of many addends makes it possible, in the presence of an irregularity due to an excess or lack of material, to increase the probability that the comparison with the predetermined threshold value be carried out based on at least one addend that is representative of the variation of the position of the pressing member at such an irregularity. In other words, the probability of taking at least one sample P.sub.i that is indicative of the position of the pressing member at such an irregularity is increased.

(44) This is schematically exemplified in FIG. 6 in which an example of positioning of the roller 8 is shown (down spatial frame) at the sampling times T.sub.i (top time frame) with respect to a plan development of the surface of the forming support 2 with geometric irregularities due to excess material (schematically illustrated with peaks) or lack of material (schematically illustrated with troughs) of the continuous elongated element 3. FIG. 6 reproduces the case of a sampling frequency f of 100 Hz (1/T=10 ms) and a peripheral speed of the forming support 2 equal to 1 m/s so that the position of the roller 8 advances by 1 cm for each subsequent sampling time of 10 ms.

(45) As schematically illustrated, in the example of FIG. 6 the roller 8 undergoes a variation of position at time T.sub.4 with respect to the previous time T.sub.3 (.sub.40) and at the time T.sub.5 with respect to the previous time T.sub.4 (.sub.50), due to the peak 61, and a variation of position at times T.sub.8, T.sub.9, T.sub.11, T.sub.12, T.sub.13, T.sub.15 and T.sub.17, with respect to the previous times (.sub.80, .sub.90, .sub.110, .sub.120, .sub.130, .sub.150, .sub.170), due to the troughs 62, 63 and the peak 64.

(46) It is clear that already with a number of addends M equal to 2 (see, for example, times T.sub.5 and T.sub.9 where, with M=2, S.sub.5=.sub.40+.sub.50 and S.sub.9=.sub.90+.sub.90) it is possible to benefit from the emphasising effect of the position differences .sub.i of the roller 8, that can be obtained with the mobile sum S.sub.i according to the invention, with respect to the case in which the value of only one difference .sub.i is considered. Moreover, it should be noted that the emphasising effect increases as the value of M increases (see, for example, times T.sub.11, T.sub.13 and T.sub.17 where, with M=3, S.sub.11=.sub.110+.sub.100+.sub.90; S.sub.13=.sub.130+.sub.120+.sub.110 and S.sub.17=.sub.170+.sub.160+.sub.150). As the value of M increases, the probability of considering at least two .sub.i different from zero in the mobile sum indeed increases.

(47) The value of M is preferably at least equal to two and, more preferably, at least equal to 3.

(48) The Applicant has also found that values of M that are too high risk triggering a filtering effect so that it is no longer possible to notice significant variations in the value of the current mobile sum S.sub.i. The value of M is, therefore, preferably less than or equal to 5.

(49) FIG. 7 shows an example similar to that of FIG. 6 where a peripheral speed of the forming support 2 equal to 2 m/s is considered so that the position of the roller 8 advances by 2 cm at each successive sampling time of 10 ms.

(50) As can be seen from a comparison between the examples of FIGS. 6 and 7, for the same sampling frequency, the discriminatory ability of the method for identifying deposition anomalies increases as the peripheral speed of the forming support 2 decreases; or, vice-versa, for the same peripheral speed of the forming support 2, the discriminatory ability of the method for identifying deposition anomalies increases as the sampling frequency increases.

(51) The Applicant also observes that, once the sampling frequency f and the peripheral speed of the forming support 2 have been set, the aforementioned discriminatory ability is greater for geometric irregularities having circumferential dimensions at least equal to the portion traveled by the roller 8 between one sample and the other (in other words, in time T=1/f). When the circumferential dimensions of the geometric irregularities are at least equal to the portion traveled by the roller 8 between on sample and the other, it indeed becomes possible to take at least two consecutive samples at such irregularities.