Method for checking a continuous elongated element during the building of a tyre for vehicle wheels

Abstract

A method for checking a continuous elongated element during the building of a tyre for vehicle wheels. A beam of an electromagnetic radiation is projected on a section of the continuous elongated element dispensed by a dispensing head and interposed between the dispensing head and a first contact area of the continuous elongated element with a radially outer surface of a tyre being processed. An image of a radiation reflected by the section is acquired. A first parameter related to the image is detected, and the first parameter is compared with a second reference parameter.

Claims

1. A method for checking a continuous elongated element during building of a tyre for vehicle wheels, comprising: setting a forming drum in rotation around a rotation axis thereof; dispensing a continuous elongated element from a dispensing head for building at least one component of a tyre being processed carried by said forming drum winding said continuous elongated element according to side-by-side and/or radially superimposed coils; projecting at least one beam of an electromagnetic radiation on a section of said continuous elongated element dispensed by said dispensing head and interposed between the dispensing head and a first contact area of the continuous elongated element with a radially outer surface of said tyre being processed; detecting at least one radiation reflected by said section in order to determine a first parameter related to a geometrical dimension of said continuous elongated element; and comparing said first parameter with a second reference parameter, wherein detecting said at least one reflected radiation comprises acquiring at least one image of said at least one radiation reflected by said section, said at least one beam intercepts lateral longitudinal edges of the continuous elongated element, wherein said at least one image comprises two ends corresponding to said lateral longitudinal edges, wherein the first parameter is related to a distance between said two ends, the electromagnetic radiation is a light radiation, said at least one image is acquired through a camera, and said at least one beam of electromagnetic radiation is substantially flat and extends transversely with respect to a feeding direction of the continuous elongated element in said section whereby said image is substantially defined by at least one transverse line.

2. The method according to claim 1, comprising: projecting a first beam and a second beam respectively towards a first lateral longitudinal edge and towards a second lateral longitudinal edge of the continuous elongated element; wherein the first beam and the second beam are substantially flat and extend transversely with respect to a feeding direction of the continuous elongated element in said section, whereby said image is substantially defined by a first transverse line and a second transverse line.

3. The method according to claim 2, wherein the first transverse line and the second transverse line are separate, wherein the first transverse line comprises a first end of said two ends and the second transverse line comprises a second end of said two ends.

4. The method according to claim 3, wherein said at least one beam of electromagnetic radiation identifies at least one emission direction; wherein the acquisition of said at least one image is performed along at least one acquisition direction; wherein the emission direction and said at least one acquisition direction are tilted with respect to each other.

5. The method according to claim 4, wherein the emission direction lies in a plane perpendicular to a feeding direction of the continuous elongated element along said section; wherein the first beam and the second beam identify a first emission direction and a second emission direction respectively, wherein the first emission direction and the second emission direction lie in a plane perpendicular to a feeding direction of the continuous elongated element along said section.

6. The method according to claim 5, wherein the first emission direction impinges on the first lateral longitudinal edge and the second emission direction impinges on the second lateral longitudinal edge.

7. The method according to claim 6, wherein the first emission direction is substantially perpendicular to the first lateral longitudinal edge and the second emission direction is substantially perpendicular to the second lateral longitudinal edge.

8. The method according to claim 3, wherein the first parameter is the distance between said two ends detected along a fixed direction in a reference system of the camera.

9. The method according to claim 8, wherein the fixed direction is a horizontal direction in the reference system of the camera and wherein, in said reference system of the camera, the horizontal direction is perpendicular to parallel and vertical reference straight lines, each straight line passing through one of the two ends.

10. The method according to claim 8, wherein the value of said second reference parameter is calculated by detecting said distance and averaging it during a time interval after a first startup time interval.

11. The method according to claim 10, wherein the value of said second reference parameter is calculated in conditions of dispensing head not obstructed in a controlled cycle.

12. The method according to claim 1, wherein the first parameter is detected continuously during the dispensing of the continuous elongated element.

13. The method according to claim 1, wherein the first parameter is detected starting from an instant after a first startup time interval.

14. The method according to claim 1, wherein comparing comprises: checking whether the value of the first parameter falls within a tolerance range placed around the value of the second parameter.

15. The method according to the claim 14, comprising: reporting a non-compliance if the value of the first parameter exits at least once from the tolerance range for a period of time longer than a preset value.

16. The method according to claim 15, wherein the value of the first parameter is recorded in a file and wherein reporting a non-compliance comprises marking the file as non-compliant.

17. A method for checking a continuous elongated element during building of a tyre for vehicle wheels, comprising: setting a forming drum in rotation around a rotation axis thereof; dispensing a continuous elongated element from a dispensing head for building at least one component of a tyre being processed carried by said forming drum winding said continuous elongated element according to side-by-side and/or radially superimposed coils; projecting at least one beam of an electromagnetic radiation on a section of said continuous elongated element dispensed by said dispensing head and interposed between the dispensing head and a first contact area of the continuous elongated element with a radially outer surface of said tyre being processed; detecting at least one radiation reflected by said section in order to determine a first parameter related to a geometrical dimension of said continuous elongated element; and comparing said first parameter with a second reference parameter, wherein detecting said at least one reflected radiation comprises acquiring at least one image of said at least one radiation reflected by said section, and said at least one beam of electromagnetic radiation is substantially flat and extends transversely with respect to a feeding direction of the continuous elongated element in said section whereby said image is substantially defined by at least one transverse line.

Description

DESCRIPTION OF THE DRAWINGS

(1) Such description will be set forth hereinbelow with reference to the enclosed drawings, provided only as a non-limiting example, in which:

(2) FIG. 1 schematically shows a plant for making tyres for vehicle wheels comprising an apparatus for building tyres according to the present invention;

(3) FIG. 2 is a radial half-section of a tyre for vehicle wheels made according to the process and with the apparatus of the present invention;

(4) FIG. 3 illustrates a side view of a portion of an apparatus for building tyres provided with a control device according to the present invention;

(5) FIG. 4 illustrates a front view of the portion of FIG. 3;

(6) FIG. 5 illustrates an enlargement of the portion of FIG. 3;

(7) FIG. 6 illustrates a section of an elongated element during the deposition on a forming drum performed in the apparatus of FIGS. 3, 4 and 5;

(8) FIG. 7 illustrates a perspective view of the elongated element during the deposition in the apparatus of FIGS. 3, 4 and 5;

(9) FIG. 8 is a graph which illustrates the obtainment of a reference parameter;

(10) FIG. 9 is a graph which illustrates the progression of a parameter detected during the process for making tyres for vehicle wheels in the plant of FIG. 1;

(11) FIG. 10 illustrates a different progression of the parameter of FIG. 9.

DETAILED DESCRIPTION

(12) With reference to FIG. 1, reference number 1 overall indicates a plant for making tyres 2 for vehicle wheels.

(13) A tyre 2, made in said plant 1 is illustrated in FIG. 2 and essentially comprises a carcass structure 3 having two carcass plies 4a, 4b. An impermeable layer of elastomeric material or so-called liner 5 is applied inside the carcass ply/plies 4a, 4b. Two anchoring annular structures 6, each comprising a so-called bead core 6a carrying an elastomeric filler 6b in radially outer position, are engaged with respective end flaps of the carcass ply/plies 4a, 4b. The anchoring annular structures 6 are integrated in proximity to areas normally identified with the name “beads” 7, at which the engagement between the tyre 2 and a respective mounting rim (not illustrated) normally occurs. A belt structure 8 comprising one or more belt layers 8a, 8b, situated in radial superimposition with respect to each other and having textile or metallic reinforcement cords with cross orientation and/or substantially parallel to the circumferential extension direction of the tyre, is circumferentially applied around the carcass ply/plies 4a, 4b, and a tread band 9 is circumferentially superimposed on the belt structure 8. So-called “under-belt inserts” 10 can be associated with the belt structure 8; each of such inserts 10 is situated between the carcass ply/plies 4a, 4b and one of the axially opposite terminal edges of the belt structure 8. Two sidewalls 11, each extended from the corresponding bead 7 to a corresponding lateral edge of the tread band 9, are applied in laterally opposite positions on the carcass plies 4a, 4b.

(14) The plant 1 illustrated in FIG. 1 provides for a production line 13 for tyres 2 comprising a carcass building line 16, an outer sleeve building line 17, and at least one moulding and vulcanisation unit 15 operatively arranged downstream of the aforesaid building lines.

(15) In the non-limiting embodiment of the plant 1 illustrated in FIG. 1, in the carcass building line 16, forming drums, not illustrated, are moved between different semi-finished product dispensing stations arranged to form, on each forming drum, a carcass sleeve comprising the carcass plies 4a, 4b, the liner 5, the anchoring annular structures 6 and possibly at least one part of the sidewalls 11.

(16) Simultaneously, in the outer sleeve building line 17, one or more auxiliary drums, not illustrated, are sequentially moved between different work stations arranged to form, on each auxiliary drum, an outer sleeve comprising at least the belt structure 8, the tread band 9, and possibly at least one part of the sidewalls 11. The production line 13 also comprises an assembly station, not illustrated, at which the outer sleeve is coupled to the carcass sleeve.

(17) In other embodiments of the plant 1, not illustrated, the building lines can be of different type, for example arranged to form all the aforesaid components on a single drum by means of suitable building devices.

(18) The built tyres 2 are then transferred to the moulding and vulcanisation unit 15.

(19) According to that schematically illustrated in FIG. 4, an apparatus 14 for building the tyres 2 belonging to any one of the above-illustrated building lines, comprises a support member 18 for a forming drum 19. The support member 18 is connected to a motor 20 configured for setting the forming drum 19 in rotation around a rotation axis thereof “X”.

(20) A dispensing head 21 or opening of an extruder 22 is placed in proximity to a radially outer surface 23 of the forming drum 19 (FIGS. 3 and 5). The dispensing head 21 is configured for continuously dispensing a continuous elongated element 24 up to a first contact area of said continuous elongated element 24 with the radially outer surface 23 of the forming drum 19 or of a tyre being processed carried by said forming drum 19, while the motor 20 makes the forming drum 19 rotate around the rotation axis “X” in a manner so as to wind the continuous elongated element 24 on the abovementioned radially outer surface. Preferably, such winding occurs according to side-by-side coils. Preferably, such winding occurs according to coils that are side-by-side and/or at least partially radially superimposed.

(21) As is visible in particular in FIG. 5, the dispensing head 21 has a dispensing direction incident with the radially outer surface 23 of the forming drum 19 and at a distance, measured along said dispensing direction, of a few centimetres from the forming drum 19, so that a section 25 of the abovementioned continuous elongated element 24 interposed between the dispensing head 21 and the first contact area has a length of a few centimetres, e.g. 25 mm-30 mm. A design width of the continuous elongated element is for example about 20 mm.

(22) An applicator device 26 comprises a pressing element 27, which in the illustrated example is a roller, operatively active in the first contact area. The applicator device 26 also comprises an actuator, for example hydraulic or pneumatic, not illustrated, configured for pressing the roller 27 against a portion of the continuous elongated element 24 placed immediately downstream of said section 25 and then for pressing said portion against the radially outer surface while the continuous elongated element 24 is deposited on the tyre being processed. A support 28 of the roller 27 extends along a direction that is substantially radial in moving away from the forming drum 19 and partially above the dispensing head 21 (FIG. 3).

(23) The apparatus 14 comprises a control device operatively active between the dispensing head 21 and the first contact area and configured for checking a width of the continuous elongated element 24 before its deposition on the tyre being processed.

(24) The control device comprises (FIGS. 3 and 4) a first and a second emitter 29′, 29″ of laser light and a camera CCD 30 supported by a support frame 31 which, in the illustrated exemplifying embodiment, is mounted on the extruder 22. The emitters 29′, 29″ of laser light and the camera CCD 30 are directed towards an upper face (i.e. further away from the ground on which said extruder 22 lies) of the continuous elongated element 24.

(25) With respect to the feeding direction “F” of the continuous elongated element 24 along said section 25, the emitters 29′, 29″ of laser light are interposed between the dispensing head 21 and the first contact area. The emitters 29′, 29″ are also radially more external than the dispensing head 21 with respect to the rotation axis “X” of the forming drum 19.

(26) The camera CCD 30 is positioned upstream of the dispensing head 21, with respect to an advancing sense of the continuous elongated element along said section 25, and is radially more external than the dispensing head 21 with respect to the rotation axis “X” of the forming drum 19.

(27) More in detail, the support frame 31 has a pair of uprights 32 which are extended from the extruder 22 and which support a first rod 33. The first rod 33 extends along a direction parallel to the abovementioned section 25 of the continuous elongated element and has a terminal end situated above the first contact area and the roller 27. A second rod 34 is transversely mounted on the terminal end of the first rod 33 and carries, at each opposite ends thereof, one of the emitters 29′, 29″ of laser light.

(28) The camera 30 is installed between the two uprights 32 and can be moved and blocked in order to adjust the position thereof along a curved path by means of a first adjustment device 35 which comprises two pins 36 constrained to the camera 30 and inserted in respective slots 37, of which only one is visible in FIG. 3. In this manner, it is always possible to maintain the camera 30 pointed on the reflected image. As is visible in FIG. 3, the camera 30 is radially more external than the applicator element 26 with respect to the rotation axis.

(29) Second adjustment devices 38 allow adjusting the position of the emitters 29′, 29″ of laser light. The second adjustment devices 38 comprise a first body 39 slidably engaged on the first rod 33 such that it can be blocked. The first body 39 carries the second rod 34. Second bodies 40 are slidably engaged, such that they can be blocked, on the second rod 34. Each of the emitters 29′, 29″ is pivoted to the respective second body 40 around a respective axis parallel to the first rod 33 in a manner so as to be able to adjust the angular position thereof. As is visible in FIG. 4, the emitters 29′, 29″ are placed on opposite sides of the applicator device 26.

(30) A control unit “CU”, schematically represented in FIG. 4, is operatively connected to the emitters 29′, 29″ and to the camera 30 in order to manage the operation thereof.

(31) The emitters 29′, 29″ respectively emit a first laser beam 41′ and a second laser beam 41″ along a respective first and second emission direction Y′, Y″ directed towards the section 25 of the continuous elongated element 24. As is visible in FIG. 4, the first and second emission direction Y′, Y″ are symmetric with respect to a said section 25. Each of said first and second laser beam 41′, 41″ opens as a fan, is flat and extends transversely with respect to a feeding direction “F” of the continuous elongated element 24 along said section 25. In other words, the first and second emission direction Y′, Y″ lie in a plane perpendicular to the feeding direction “F” of the continuous elongated element 24 along said section 25.

(32) In the illustrated preferred embodiment (FIGS. 6 and 7), the first and the second laser beam 41′, 41″ intercept the section 25 so as to generate, on the upper face of said section 25, a reflected image formed by a first transverse line 42 and by a second transverse line 43 which each terminate at a respective first and second lateral longitudinal edge of the continuous elongated element 24. In other words, the two laser beams 41′, 41″ encounter the continuous elongated element 24 without intersecting, so as to give rise to the two separate transverse lines 42, 43 (FIG. 7).

(33) As can be observed in FIG. 6, the continuous elongated element 24 has a cross section of lenticular form with tapered opposite edges, and each of the first and second emission directions Y′, Y″ impinges on the respective lateral longitudinal edge perpendicular thereto (FIG. 6).

(34) The camera 30 is pointed towards the reflected image formed by the first transverse line 42 and by the second transverse line 43 in order to acquire said image along an acquisition direction “Z” (FIGS. 3 and 5). The acquisition direction “Z” lies in an acquisition plane perpendicular to an advancement plane of the continuous elongated element 24 and parallel to the feeding direction “F” of the continuous elongated element 24 along said section 25. The acquisition direction “Z” is tilted with respect to the advancement plane of the continuous elongated element 24 by an angle “α”, preferably by about 45° (FIG. 5). The Applicant observes that the camera 30 sees the section 25 of the continuous elongated element 24 in perspective view as a trapezoid, according to that illustrated in FIG. 7, both due to the aforesaid tilt, and due to the stretch effect along the feeding direction “F” that the continuous elongated element sustains between the dispensing head 21 and the first contact area with the radially outer surface of the tyre being processed.

(35) The acquisition direction “Z” passes between the dispensing head 21 and the applicator device 26. The first and second emission direction Y′, Y″ and the acquisition direction “Z” are therefore tilted with respect to each other.

(36) The camera 30 frames a coverage area 44 which at least partly contains said section 25. An analysed area 45, as described hereinbelow, is contained in said coverage area 44. The analysed area 45 contains the reflected image formed by the first transverse line 42 and by the second transverse line 43.

(37) The control unit “CU” is configured for detecting, through the camera 30, a first parameter “d1(t)” related to the reflected image formed by the first transverse line 42 and by the second transverse line 43 and for comparing the first parameter “d1(t)” with a second reference parameter “d2”.

(38) As is visible in FIG. 7, the image formed by the first transverse line 42 and by the second transverse line 43 comprises a first end 46 lying on one of the longitudinal edges and belonging to the first transverse line 42 and a second end 47 lying on the other of the longitudinal edges and belonging to the second transverse line 43.

(39) The abovementioned first parameter “d1(t)” is the distance “d” between said first and second end 46, 47 detected along a fixed horizontal direction (in a reference system of the camera 30), in which the horizontal direction is perpendicular to parallel and vertical reference straight lines, each passing through one of the two ends 46, 47 (FIG. 7). The abovementioned first parameter “d1(t)” is the distance “d” continuously detected during the deposition of the continuous elongated element 24 starting from an instant after a first startup time interval “t1” for the stabilization of the value of said distance “d”.

(40) The second parameter “d2” is the reference value of the distance “d” that was previously acquired, as will be better illustrated hereinbelow, during a controlled cycle, in which the value of said distance “d” is certainly within the prescribed tolerances since it was produced under controlled conditions (dispensing head 21 or opening of the extruder 22 in nominal or clean conditions).

(41) More in detail, in accordance with the process and the method of the present invention, the operator, before starting the deposition of the continuous elongated element 24 on the forming drum 19, visually controls that the dispensing head 21 is not obstructed or partially obstructed. If everything is ok, the dispensing of the continuous elongated element 24 is started, along with the rotation of the forming drum 19. In addition, the emitters 29′, 29″ of laser light and the camera 30 are activated and the camera 30 starts acquiring the reflected image (first transverse line 42 and second transverse line 43). The control is therefore carried out in real time.

(42) In a very first step (startup interval “t1” of several seconds according to that indicated in FIGS. 8-10), before a head end of the continuous elongated element 24 reaches under the roller 27, the geometry and the width of said continuous elongated element 24 sustain variations that are not taken under consideration.

(43) In a subsequent first time interval “Δt”, the control unit “CU” through the camera 30 detects the distance “d”, calculates the average value thereof and stores it as said second parameter “d2” (FIG. 8).

(44) The calculation of the aforesaid parameter d2 is made upon manual command of the operator, or automatically upon changing recipe for the elastomeric material, since the procedures in this case also provide for the cleaning of the dispensing head 21 or of the opening of the extruder 22.

(45) During the normal building step, i.e. after having stored the aforesaid second parameter “d2” and once again started the deposition of the continuous elongated element 24 on the tyre being processed, following the startup interval “t1”, the control unit “CU” through the camera 30 detects the first parameter “d1(t)” and checks if the first parameter “d1(t)” falls within a tolerance range “Δd” placed around the second parameter “d2”. The control carried out is therefore of relative type since the reference measurement is the distance “d” detected during a controlled cycle in which the width of the continuous elongated element 24 is certainly that desired. The value of the tolerance range “Δd” is set in the control unit “CU” and can for example be changed by the operator.

(46) If the first parameter “d1(t)” exits from the tolerance range “Δd”, the control unit “CU” also checks if the stay of such first parameter “d1(t)” outside the tolerance range “Δd” exceeds a period of time longer than a preset value “tmax”; the latter can also be set, for example as a function of the dispensing speed.

(47) The control unit “CU” drives a signalling device (e.g. a LED lamp or acoustic signalling device) which emits a first alert signal each time that the first parameter “d1(t)” exits from the tolerance range “Δd”, independent of the stay time and without stopping the deposition.

(48) If instead the stay of the first parameter “d1(t)” outside the tolerance range “Δd” exceeds the preset value “tmax” one or more times, then at the end of the deposition the control unit “CU” drives, for example, a further signalling device that emits a second alert signal which indicates the non-compliance of the tyre just built.

(49) In addition, from the start of the dispensing and of the acquisition, the progression of the distance “d” is recorded in a file preferably saved in a database which contains the records of the measurements carried out during the depositions. If the stay of the first parameter “d1(t)” outside the tolerance range “Δd” exceeds the abovementioned preset value “tmax” one or more times, the respective file is marked (e.g. by giving it a suitable name) as non-compliant.

(50) This for a quick and targeted search of the cycles that are not compliant from among the thousands of saved cycles.

(51) For example, the continuous elongated element 24 has a design width of 20 mm. After the start time interval “t1”, the control unit “CU” through the camera 30 detects the distance “d” and compares it with the second parameter “d2” previously stored during a controlled cycle, as illustrated above.

(52) Such second parameter “d2” is for example 100 pixel which corresponds to about 19 mm. The difference between the weight value taken as average (19 mm) and the design value (20 mm) depends on the acceptable variability of the process and for example on pulses determined by the meshing of the teeth of the gear pump of the extruder 22.

(53) The value of the tolerance range “Δd” preset in the control unit “CU” can for example be +/−5 pixel (or +/−5% of “d2”) which corresponds with +/−0.95 mm.

(54) FIG. 9 illustrates the progression of the first parameter “d1(t)” which remains within the tolerance range “Δd”. The respective file will be marked as compliant.

(55) In FIG. 10, instead, the first parameter “d1(t)” exits from the tolerance range “Δd” for a time greater than the preset value “tmax”, which for example is about 2 s, before returning. For example, the first parameter “d1(t)” detected is 17 mm for 8 s, i.e. the continuous elongated element is narrower than that tolerated. In this case, the control unit “CU” emits the first alert signal and also the second alert signal at the end of the deposition. The respective file will be marked as non-compliant.

(56) The tyre can, for example, be controlled by the operator who judges if the tyre is actually not acceptable or brought, through automated devices, into an area intended for a more in-depth control, or the tyre can be directly discarded.

(57) In an embodiment variant, provision is made for stopping the dispensing and discarding the tyre as soon as the control unit “CU” detects that the first parameter “d1(t)” exited from the tolerance range “Δd” for a time greater than the preset value “tmax”.