Patent Application
20250060282
The invention relates to an apparatus and to a method for testing tires.
The use of retreaded tires has become more and more widespread, said retreaded tires being obtained at the end of a retreading process to which damaged tires are subjected, namely tires having defects such as holes, cracks or irregularities in the innerliner. Before carrying out the retreading process, however, it is extremely important to recognize, in a reliable manner, all the defects present in the tire, in particular on the carcass, and repair them. Even though a visual or mechanical inspection of a carcass is relatively accurate, it often happens that some defects fail to be recognized; these defects can then cause problems during the retreading process or during the use of the retreaded tire on the road, leading to tire failures, safety issues and vehicles stopping.
For this reason, tire testing apparatuses are known, of which the test tires have a toroidal carcass, which internally defines a cavity and supports a pair of sidewalls arranged on the outside of the carcass. Said apparatuses typically comprise a probe obtained by means of at least one plate, to which a number of wire loops are connected, which are designed to slide on the superficial profile of the cavity of the carcass and are made of an electrically conductor material; spreaders which are aimed at widening the carcass to let the probe enter in proximity of the cavity; at least one roller, which is designed to support the tire and cause it to rotate around a central axis and is made of an electrically conductor material; and, finally, a high-voltage test system, which is suited to detect the presence of defects in the carcass and comprises a pair of electrodes, which are defined by the probe and by the roller.
In use, the roller is caused to rotate, so that it causes the tire to rotate around its central axis. When the tire rotates, the probe slides on the surface of the inner cavity and, at the same time, is supplied with high-voltage pulses by a power supply source, thus creating an electric field around the probe. In case the carcass lacks defects (holes, cracks or irregularities in the innerliner, etc.), the carcass provides an insulation between the two electrodes. On the contrary, in case the carcass has defects, the insulation between the two electrodes is not ensured and the defect is detected by a control unit.
However, apparatuses of the type described so far suffer from some drawbacks. In particular, the wire loops defining the probe do not engage, in a reliable and satisfactory manner, the entire surface of the inner cavity which could have defects, namely the crown (the central portion of the carcass) and, to an even greater extent, the sidewalls. Furthermore, probes of the type described above often are relatively large and make it difficult for the probe to be inserted into the inner cavity of the tire and require additional spreaders to enlarge the carcass prior to let the probe enter in the cavity, thereby rendering the apparatus more complex to use.
Therefore, the object of the invention is to provide a reliable apparatus for testing tires which is not affected by the drawbacks of the prior art and, in particular, is easy and economical to be manufactured.
Further object of the invention is to provide a method for testing tires which is not affected by the drawbacks of the prior art and, in particular, is easy and economical to implement.
According to the invention, there are provided an apparatus and a method for testing tires according to the appended claims.
The invention will now be described with reference to the accompanying drawings, which show some non-limiting embodiments thereof, wherein:
With reference to
The tire 2 comprises a toroidal carcass 3, which consists of a body ply having, on its opposite sides, two annular beads. The carcass 3 supports a pair of sidewalls 4 arranged on the outside of the carcass 3 and extending up to the beads. On the inside of the carcass 3, on the entire available surface (namely, in the area of the central crown and of the sidewalls 4), there is arranged an innerliner, which is impermeable to air, forms an inner coating and has the function of holding air inside the tire 2.
The apparatus 1 comprises a support frame 5, which is suited to support the tire 2 and causes it to rotate around a central axis X of its through motor-driven rollers 6, 7. Preferably, there are a pair of rollers 6, 7 having respective axes Z6 Z7, which are parallel to one another and are parallel to the axis X.
The apparatus 1 further comprises a high-voltage test system 8, which is suited to detect the presence of defects (holes, cracks or irregularities in the innerliner, etc.) in the casing 3.
The high-voltage test system 8 comprises the roller 6 (and, in particular, a central core 9 thereof), which is designed to serve as a first electrode of the high-voltage test system 8, as better described below.
The roller 6 comprises a central core 9, which is a conductor and made of an electrically conductive material, central core 9 is preferably made of a metal material.
The roller 6 further comprises a coating layer 10, which is coaxial to the central core 9 and to the axis Z6. The coating layer 10 has an even thickness and is applied so as to completely and uniformly wound the central core 9. More in detail, the coating layer 10 has a thickness less or equal to 15 mm, preferably ranging from 4 to 15 mm. The coating layer 10 is made of an electrically conductive material. Preferably, but not limited to, the coating layer 10 is made of a polymer (like, for example, synthetic or natural or silicone based rubber). In use, the coating layer 10 is interposed between the carcass 3 and the central core 9. Surface resistivity of an outer surface 11 of the roller 6 is comprised in the range 10*e3-10*e6 Ω/sq cm.
Outer surface 11 has a concave profile, with the concavity facing the tire 2. More in detail, the central core 9 is provided with an outer surface 12 having a concave profile, with the concavity facing the tire 2, with the interposition of the coating layer 10.
The bending radius of the concave profile of the outer surface 11 ranges from 68 to 240 centimetres; preferably, the bending radius of the concave profile of the outer surface 11 is equal to 103 centimetres.
The support frame 5 further comprises a probe 13. The probe 13 is conveniently obtained by means of a robot 14 provided with a movable arm 15 and suited to be inserted into the tire 2 so as to slide on the profile of an inner cavity 16 of the tire 2. The expression “profile of the inner cavity 16” indicates a superficial profile of the tire 2 or of the carcass 3, in the area of the portion of the tire 2 that is going to come into contact with the asphalt, namely in the area of the crown and, at least partially, of the sidewalls 4.
The probe 13 comprises a structure 17, which is designed to adjust to the superficial profile of the inner cavity 16. The structure 17 is made of an electrically non-conductive or insulating material. The structure 17 is made, for example, of PLA or ABS or nylon.
The structure 17 comprises a central pin 18 having an axis X18 and having one of its ends connected to a fixed bar 19 provided with a guide roller 20, which is designed to slide on the profile of the inner cavity 16. According to a preferred variant, the fixed bar 19 has, at the front, a U-shape provided with two side appendages. The structure 17 further comprises two arms 21A, 21B articulated to one another and arranged in a mirror-like manner relative to the axis X18, only one of them being described in the description below.
The structure 17 further comprises a movable bar 22, which is connected to the pin 18 and is free to slide along the pin 18 between a lifted position (shown in
Each articulated arm 21A, 21B is obtained by means of a respective rod 23A, 23B, which is hinged, at a first end, to a respective end of the movable bar 22 by means of a respective articulation pin 24A, 24B. Each rod 23A, 23B carries, connected at a second end, a respective guide roller 25A, 25B, which is suited to slide on the surface of the inner cavity 16 when the structure 17 is in the test position.
Each articulated arm 21A, 21B further comprises a respective rod 26A, 26B, which is hinged, at a first end, to a respective appendage of the fixed bar 19 by means of a respective articulation pin 27A, 27B. Each rod 26A, 26B is further connected, at a second end, to a second end of a respective rod 23A, 23B by means of a respective articulation pin 28A, 28B.
The axes of the aforesaid articulation pins indicated with 24A, 24B, 27A, 27B and 28A, 28B are all parallel to one another and orthogonal to the axis X18.
The probe 13 finally comprises a chain mail portion 29, which is connected to both rods 23A, 23B, preferably in the area of the articulation pins 28A, 28B. The chain mail portion 29 is made of an electrically conductive material. In particular, the chain mail portion 29 is made of a metal material. The chain mail portion 29 defines the second electrode of the high-voltage test system 8, as described more in detail below.
The chain mail portion 29 has a length L of at least 3 cm; preferably, the length L of the chain mail portion 29 ranges from 8 to 15 cm. The chain mail portion 29 covers at least 3 cm of the innerliner along a substantially longitudinal direction (which correspond to the direction of rotation of the tire 2 indicated with arrow D in
The width S of the chain mail portion 29, on the other hand, is defined by the distance of the two articulation pins 28A, 28B in the test position. The width S of the chain mail portion 29 is such that it engages the surface of the inner cavity 16 in the area of the crown, namely of the central portion of the carcass 3, and at least partially in the area of the sidewalls 4. The chain mail portion 29 covers an area of the innerliner along a transversal direction that corresponds to the crown and at least partially the sidewalls 4.
The chain mail portion 29 is designed to serve as a second electrode of the high-voltage test system 8, as described more in detail below.
The apparatus 1 further comprises an electronic control unit ECU, which controls the operation of the apparatus 1 and, in particular, controls the operation of the high-voltage test system 8. More in detail, the electronic control unit ECU is suited to supply the second electrode (namely, the chain mail portion 29) with pulses of approximately 25 kV, as described more in detail below.
According to a preferred variant, when the arm 15 is inserted in the inner cavity 16, the roller 6 is aligned with the axis X18. In other words, the roller 6 and the structure 17 are not misaligned. According to a variant shown in
The second electrode (namely, the chain mail portion 29) is connected to the electronic control unit ECU and to a high-voltage power supply source 30. The first electrode (namely, the roller 6) is connected to the electronic control unit ECU, as well.
The strategy implemented by the electronic control unit ECU in order to check for the presence of defects in the tire 2 will be described below.
The method comprises, first of all, a preparation step, during which:
On the other hand, the actual test step, which is subsequent to the preparation step, entails causing the rotation of the rollers 6, 7, which, in turn, cause the rotation of the tire 2 around the axis X. When the tire 2 rotates around the axis X, the second electrode (namely, the chain mail portion 29) slides on the entire surface of the inner cavity 16. Simultaneously, the second electrode (namely, the chain mail portion 29) is supplied with high-voltage pulses by the power supply source 30, thus creating an electric field around the second electrode (namely, around the chain mail portion 29).
In case the carcass 3 lacks defects (holes, cracks or irregularities in the innerliner, etc.), the carcass 3 provides an insulation between the first electrode (namely, the roller 6) and the second electrode (namely, the chain mail portion 29). On the contrary, in case the carcass 3 has defects (holes, cracks or irregularities in the innerliner, etc.), the carcass 3 does not ensure the insulation between the first electrode (namely, the roller 6) and the second electrode (namely, the chain mail portion 29) and the defect is detected by the electronic control unit ECU.
Once a rotation of the tire 2 around the axis X has been completed, the movable bar 22 is controlled so as to move from the test position to the lifted position, the arm 15 is extracted from the inner cavity 16 and the tire 2 is removed either manually (by an operator) or automatically (with a robot arm) from the support frame 5 in order to replace it with a tire 2 to be tested.
The advantages of the apparatus 1 for testing tires 2 disclosed in the description above are numerous and can evidently be assumed from the description above. In particular, the structure 17 can easily be inserted into any type of tire 2 without requiring any additional spreaders. Furthermore, the roller 6 is designed to adjust to the shape of the carcass 3 and to ensure, during the test step, a good contact with the entire portion of the tire 2 that is going to come into contact with the asphalt, namely with the crown and, at least partially, with the sidewalls 4. Finally, the high-voltage test system 8 recognizes defects (holes, cracks or irregularities on the innerliner, etc.) of the carcass 3 in a reliable manner and, especially, avoids wrong recognitions of defects.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21214356.4 | Dec 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/085361 | 12/12/2022 | WO |
