Method for producing a tread

Abstract

The invention relates to a method for producing a tread (20), comprising the steps: extruding the tread (20), which has an outer side (22) and an inner side (24), opposite the outer side (22), and a carrying region (26) made of a carrying region rubber material and a guide strip (28) made of a guide strip rubber material, wherein the guide strip (28) extends from the outside (22) to the inside (24) and a specific electrical guide strip resistance (W.sub.28) of the guide strip rubber material is smaller than a specific electrical carrying region resistance of the carrying region rubber material. The steps according to the invention are: determining an electrical guide strip resistance (W.sub.28) of the guide strip (28) between the outer side (22) and the inner side (24) and outputting a warning signal when the electrical resistance (W) exceeds a specified maximum resistance (W.sub.28,max).

Claims

1. A method for manufacturing a tread (20), with the steps of: (a) extruding a tread (20), which has an exterior side (22) and an interior side (24) lying opposite the exterior side (22), and comprises a supporting area (26) made out of a rubber supporting area material and a guide strip (28) made out of a rubber guide strip material, (b) wherein the guide strip (28) extends from the exterior side (22) to the interior side (24), and a specific electrical guide strip resistance (ρ.sub.28) of the guide strip rubber material is less than a specific electrical supporting area resistance (ρ.sub.26) of the supporting area rubber material, characterized by the steps of: (c) determining a parameter (P) that correlates with an electrical guide strip resistance (W.sub.28) of the guide strip (28) between the exterior side (22) and interior side (24), and (d) outputting a warning signal when the parameter (P) assumes a value indicating that the guide strip resistance (W.sub.28) exceeds a prescribed maximum value (W.sub.28,max), wherein (a) determining the parameter (P) involves the step of applying an electrostatic charge (Q) to a side (22, 24), and (b) the parameter (P) describes a charging current (I) that arises when applying an electrostatic charge (Q), and wherein the electrostatic charge (Q) is applied without contact.

2. The method according to claim 1, wherein determining the guide strip resistance (W.sub.28) involves the following steps: contacting the exterior side (22) by means of an outer electrode (32), and contacting the interior side (24) with an inner electrode (34), wherein one of the electrodes (22, 24) contacts the tread (20) from above.

3. The method according to claim 1, wherein a region of the tread (20) in which the maximum resistance (W.sub.28,max) has been exceeded is eliminated.

4. A method for manufacturing a tread (20), with the steps of: (a) extruding a tread (20), which has an exterior side (22) and an interior side (24) lying opposite the exterior side (22), and comprises a supporting area (26) made out of a rubber supporting area material and a guide strip (28) made out of a rubber guide strip material, (b) wherein the guide strip (28) extends from the exterior side (22) to the interior side (24), and a specific electrical guide strip resistance (ρ.sub.28) of the guide strip rubber material is less than a specific electrical supporting area resistance (ρ.sub.26) of the supporting area rubber material, characterized by the steps of: (c) determining a parameter (P) that correlates with an electrical guide strip resistance (W.sub.28) of the guide strip (28) between the exterior side (22) and interior side (24), and (d) outputting a warning signal when the parameter (P) assumes a value indicating that the guide strip resistance (W.sub.28) exceeds a prescribed maximum value W.sub.28,max), wherein (a) determining the parameter (P) involves the step of applying an electrostatic charge (Q) to a side (22, 24), and (b) the parameter (P) describes a charging current (I) that arises when applying an electrostatic charge (Q), and wherein a voltage (U) measures at least 3 kV when applying the charge.

5. A method for manufacturing a tread (20), with the steps of: (a) extruding a tread (20), which has an exterior side (22) and an interior side (24) lying opposite the exterior side (22), and comprises a supporting area (26) made out of a rubber supporting area material and a guide strip (28) made out of a rubber guide strip material, (b) wherein the guide strip (28) extends from the exterior side (22) to the interior side (24), and a specific electrical guide strip resistance (p28) of the guide strip rubber material is less than a specific electrical supporting area resistance (p26) of the supporting area rubber material, characterized by the steps of: (c) determining a parameter (P) that correlates with an electrical guide strip resistance (W.sub.28) of the guide strip (28) between the exterior side (22) and interior side (24), and (d) outputting a warning signal when the parameter (P) assumes a value indicating that the guide strip resistance (W.sub.28) exceeds a prescribed maximum value (W.sub.28,max), wherein (a) determining the parameter (P) involves the step of applying an electrostatic charge (Q) to a side (22, 24), and (b) the parameter (P) describes a charging current (I) that arises when applying an electrostatic charge (Q), and wherein the electrode (32, 43) used in applying the charge has an emission edge (58), and that the electrode (32, 34) can be turned in such a way that an effective width (B.sub.eff) of the electrode (32, 34) can be varied.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail below based on the attached drawings. Shown here on:

(2) FIG. 1 is a horizontal view of a tread manufacturing device according to the invention,

(3) FIG. 2 is a cross section through a guide strip fabricated by means of the tread manufacturing device,

(4) FIG. 3 is a side view of the tread manufacturing device according to FIG. 1, and

(5) FIG. 4 is a schematic, side view of a tread manufacturing device based on a second embodiment.

(6) FIG. 5 shows a horizontal section of a tread manufacturing device based on a second embodiment of the invention, and

(7) FIG. 6 shows a horizontal section of a tread manufacturing device according to the invention based on a third embodiment of the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

(8) FIG. 1 shows a tread manufacturing device 10 according to the invention, which comprises an extruder system 12. The extruder system 12 has a head 14 and, in the present case, five extruders 16.1, . . . , 16.5. The extruders 16.i (i=1, 2, 3, 4, 5) each convey rubber material, and press it into the head 14 through corresponding guide channels 18.i. The head 14 forms a tread 20 out of the rubber material.

(9) FIG. 2 shows a cross section through the tread 20. As evident, the latter has an exterior side 22 and an interior side 24. In a tire produced by means of the tread 20, the interior side 24 faces inward, and the exterior side 22 faces toward the street.

(10) The tread 20 has a carrying region 26, which in the present case is composed of carrying region parts 26.1, 26.2. Carrying region rubber material is present in the carrying region. In addition to rubber and possibly soot and other constituents, the carrying region rubber material consists of a high percentage of silicon dioxide. For example, the percentage of silicon dioxide measures at least 10 percent by weight and at most 20 percent by weight. As a result, the carrying region 26 has a high resistance to wear. However, the specific electrical resistance is high, and measures more than ρ.sub.26=10.sup.12 Ω.Math.m, for example. This value relates to 20° C.

(11) The tread 20 also has a guide strip 28 comprised of guide strip rubber material, the electrical conductivity ρ.sub.28 of which is distinctly lower, and in particular measures at most 1/10 of the electrical conductivity ρ.sub.26 of the carrying region rubber material. An electrical resistance ρ.sub.28 of the guide strip between the exterior side 22 and interior side 24 preferably measures at most W.sub.28=100 MΩ, in particular at most W.sub.28=10 MΩ.

(12) FIG. 3 presents a schematic, side view of the tread manufacturing device 10. As evident, the tread manufacturing device 10 has a resistance determining device 30, which has an outer electrode 32 and an inner electrode 34. The outer electrode 32 comprises a wheel 36, which is fastened in an electrically conductive manner to an arm 38. The inner electrode 34 is formed by at least one support roller 40.1 of a conveying device 42. The conveying device 42 transports the tread 20 away from the head 14 (see FIG. 1). An evaluation circuit 44 determines the electrical resistance W.sub.28 between the outer electrode 32 and inner electrode 34, which very closely approximates the resistance of the guide strip 28 (see FIG. 2).

(13) In terms of a direction of material flow M, electrodes 32, 34 are arranged closely behind the head 14. If the evaluation circuit 44 detects an electrical resistance W.sub.28 greater than a prescribed maximum resistance W.sub.28,max., it emits a warning signal.

(14) For example, the warning signal can be an electrical signal to a control unit, which also controls the extruder system 12. Alternatively involved is an acoustic and/or optical signal, so that a machine operator can recognize the error. Alternatively or additionally as well, the evaluation circuit 44 is wirelessly connected or hardwired with a schematically recorded marking device 46, which in this case applies color 48 to the tread 20, in particular through spraying. The section of the tread that can possibly not be used for manufacturing tires is marked in this way.

(15) FIG. 4 shows a schematic, side view of a tread manufacturing device 10 according to a second embodiment of the invention. As evident, both the outer electrode 32 and inner electrode 34 have a plurality of hair-shaped conductors 50.1, 50.2, . . . , which are combined into a block 50 and thereby electrically contacted. The conductors 50.j (j=1, 2, . . . ) pass by the guide strip 28 from the exterior side 22 and interior side 24, and thereby contact it. The evaluation takes place as described above.

(16) Purely schematically delineated are a cutting machine and a vulcanizing device 56, which are used to manufacture tires using the tread 20.

(17) FIG. 5 shows another tread manufacturing device 10 according to the invention, in which an electrode, in the case at hand the outer electrode 32, is arranged for grounding the tread 20, and in particular the guide strip 28.

(18) Let it be noted that the orientation of the tread 20 can also be reversed in the entire specification. In other words, the structure of the tread manufacturing device does not change if the tread lies on the conveying device 42 not with its exterior side 22 facing up, but rather with its exterior side 22 facing down. The outer electrode 32 could therefore also be referred to as the first electrode, and the inner electrode 34 could also be referred to as the second electrode. The terms outer electrode and inner electrode are only used for the sake of simplicity.

(19) The tread manufacturing device 10 has an inner electrode 34, which is designed for contacting the tread 20 without contact. The inner electrode 34 has an emission edge 58, and is connected with a high-voltage source 60. In the present case, the high-voltage source emits a voltage U, which can also be referred to as the application voltage, that measures U=3 kV. Therefore, electrons 62 are applied from the emission edge 58 onto the tread 20.

(20) If the guide strip 28 (see FIG. 2) is correctly designed, its electrical resistance W.sub.28 is less than the prescribed maximum resistance W.sub.28,max. As a result, an electrical current I arises between the inner electrode 34 and outer electrode 32. In the present case, the outer electrode 32 is grounded, and the high-voltage source 60 generates a voltage against ground. Alternatively, the outer electrode can be directly connected with the high-voltage source 60.

(21) The electrical current I is detected by the evaluation circuit, which is connected with the high-voltage source 60. The high-voltage source 60 can also be part of the evaluation circuit 44. The higher the electrical current E, the lower the electrical resistance W.sub.28 of the guide strip 28.

(22) If the guide strip 28 is defective, i.e., if it has too high an electrical resistance, the electrons 62 permanently accumulate on the tread 20. They there form a permanently remaining electrical charge Q. This charge Q leads to an electrical field that superposes itself with the electrical field of the inner electrode, and causes the current I to become smaller. Therefore, the current I is a parameter P based upon which the guide strip resistance can be assessed. If the parameter P, for which P=I in the case at hand, drops below a minimum value I.sub.min, it indicates that the guide strip resistance W.sub.28 has dropped below the prescribed maximum value W.sub.28,max. A warning signal is then output.

(23) A discharge electrode 64 is arranged behind the electrodes 32, 34 in the direction of material flow M, and used to largely discharge the tread 20. It is possible and preferred that the discharge electrode work without contact, as in the present case. However, the discharge electrode 64 can also work in a contacting manner.

(24) FIG. 6 shows another alternative embodiment of a tread manufacturing device 10 according to the invention, in which the outer electrode is designed as a contactless electrode. The latter applies the electrical charge Q to the exterior side 22 of the tread 20. The tread is grounded by means of the inner electrode 34, which in the present case has a wheel 36 as described above, which contacts the guide strip 28 (see FIG. 2).

(25) FIG. 1 presents a schematic, top view of the outer electrode 32. As evident, the emission edge 58 extends transverse to a longitudinal direction L of the tread 20. In other words, an offset angle α in the case at hand preferably measures at least 75°, and at most 105°.

(26) The electrode can be turned with a turning device 66 (see FIG. 6) in such a way that the offset angle α can be adjusted. This makes it possible to adjust the offset angle α, and hence an effective width B.sub.eff of the outer electrode 32. It is favorable that the effective width B.sub.eff be greater than the width b of the guide strip 28. However, it is also favorable that the effective width B.sub.eff be at least three times, preferably at least five times, the width b of the guide strip 28. As a rule, it is favorable that the effective width B.sub.eff measure at most 50 times, in particular 30 times, the width b of the guide strip.

(27) The evaluation circuit 44 continuously compares whether the parameter P, in the present case the electrical current I, has a value indicating that the guide strip resistance W.sub.28 does not exceed the prescribed maximum value W.sub.28,max. If the parameter P is the electrical charging current I, a drop below a minimum current I.sub.min means that the guide strip resistance W.sub.28 has exceeded the prescribed maximum value W.sub.28,max. For example, the electrical current I is determined at least once per second, preferably at least once per tenth of a second.

(28) As described above, the charge Q can be applied in the form of electrons. Alternatively, it is also possible that the respective electrode be designed as an anti-static bar, which accelerates ions toward the tread 20, and thereby electrostatically charges the latter.

REFERENCE LIST

(29) 10 Tread manufacturing device 12 Extruder system 14 Head 16 Extruder 20 Tread 22 Exterior side 24 Interior side 26 Carrying region 28 Guide strip 30 Resistance determining device 32 Outer electrode 35 Inner electrode 36 Wheel 38 Arm 40 Support roller 42 Conveying device 44 Evaluation circuit 46 Marking device 48 Color 50 Conductor 52 Block 54 Cutting device 56 Vulcanizing device 58 Emission edge 60 High-voltage source 62 Electrons 64 Discharge electrode 66 Turning device A Distance between extruder outlet and electrode α Offset angle B Width of guide strip I Load index I Electrical current I.sub.min Minimal current M Direction of material flow P Parameter Q Electrostatic charge U Voltage (=applied voltage) W.sub.28 Electrical resistance of tread W.sub.28,max Maximum resistance ρ Specific electrical resistance