Surface demoldability prediction model

Abstract

The prediction model includes the steps of calculating a surface area S.sub.1 of a control mold, measuring the force F.sub.1 for demolding from the control mold, determining first and second test specimens with respective surface areas S.sub.0, S.sub.0, measuring the force F.sub.0 for demolding from the first test specimen, measuring the force F.sub.0 for demolding from the second test specimen, calculating the ratio of S.sub.0 and S.sub.0 so as to define a test specimen surface area ratio R.sub.se, calculating the ratio of the force F.sub.0 for demolding from the first test specimen and F.sub.0 for demolding from the second test specimen so as to define a force ratio R.sub.fe, measuring the molding surface area S.sub.m of a mold to be measured and calculating the force F.sub.m for demolding from the mold to be measured such that F.sub.m=F.sub.1S.sub.m/S.sub.1R.sub.fe/R.sub.se.

Claims

1. A method for evaluating a force for demolding a tire from a mold, consisting of measuring a force for demolding from and a molding surface area of a control mold, said method including the steps of: choosing the control mold, calculating the molding surface area S.sub.1 of the control mold, measuring the force F.sub.1 for demolding from the control mold, determining a first control test specimen with a molding surface area S.sub.0, determining a second control test specimen with a molding surface area S.sub.0, S.sub.0 being different from S.sub.0, measuring the force F.sub.0 for demolding from the first control test specimen, measuring the force F.sub.0 for demolding from the second control test specimen, calculating the ratio of the molding surface area S.sub.0 of the first test specimen and S.sub.0 of the second test specimen so as to define a test specimen surface area ratio R.sub.se, calculating the ratio of the force F.sub.0 for demolding from the first test specimen and F.sub.0 for demolding from the second test specimen so as to define a test specimen force ratio R.sub.fe, a step of selecting a mold to be measured, a step of calculating the molding surface area S.sub.m of the mold to be measured, calculating the force F.sub.m for demolding from the mold to be measured such that F.sub.m =F.sub.1S.sub.m/S.sub.1R.sub.fe/R.sub.se; and demolding a tire from the mold based on the calculated force F.sub.m.

2. The method according to claim 1, wherein the molding surface area S.sub.0 of the second test specimen is greater than the molding surface area S.sub.0 of the first test specimen.

3. The method according to claim 1, further including the steps of: determining the force M.sub.0 for demolding the reference material from a material test specimen, selecting a material to be measured, determining the force M for demolding the material from the material test specimen, calculating the ratio of the forces M.sub.0 for demolding the reference material and M for demolding the material from the material test specimen so as to define a coefficient C of material impact, calculating the force F for demolding the material such that F=CF.sub.0.

4. A device for selecting the molding surface area of a molding comprising a control mold according to the method of claim 1, wherein the device comprises a first and a second test specimen, a force measuring device and a calculating means for calculating the calculating steps in the method according to claim 1.

5. A computer program for selecting the molding surface area of a mold, wherein the computer program comprises the following instructions: a step of choosing the control mold, a step of calculating the molding surface area S.sub.1 of the control mold, a step of measuring the force F.sub.1 for demolding from the control mold, a step of determining a first control test specimen with a molding surface area S.sub.0, a step of determining a second control test specimen with a molding surface area S.sub.0, S.sub.0 being different from S.sub.0, a step of measuring the force F.sub.0 for demolding from the first control test specimen, a step of measuring the force F.sub.0 for demolding from the second control test specimen, a step of calculating the ratio of the molding surface area S.sub.0 of the first test specimen and S.sub.0 of the second test specimen so as to define a test specimen surface area ratio R.sub.se, a step of calculating the ratio of the force F.sub.0 for demolding from the first test specimen and F.sub.0 for demolding from the second test specimen so as to define a test specimen force ratio R.sub.fe, a step of selecting a mold to be measured, a step of calculating the molding surface area S.sub.m of the mold to be measured, a step of calculating the force F.sub.m for demolding from the mold to be measured such that F.sub.m=F.sub.1S.sub.m/S.sub.1R.sub.fe/R.sub.se and demolding a tire from the mold based on the calculated force F.sub.m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages may also become apparent to a person skilled in the art from reading the following examples, which are illustrated by the appended figures and given by way of example:

(2) FIG. 1 shows a flowchart of the steps in the method for evaluating the force for demolding a tire according to the disclosure,

(3) FIGS. 2 and 3 are perspective views of a first and a second test specimen,

(4) FIG. 4 a selection device according to the disclosure, and

(5) FIG. 5 shows a flowchart of additional steps of the method.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT

(6) FIG. 1 shows a flowchart of the steps in the method for evaluating the force for demolding a tire from a mold.

(7) The method includes a step E of determining the molding surface area S.sub.1 and of determining the force F.sub.1 for demolding from a control mold. This step E comprises a substep E1 of determining a control mold, a substep E2 of calculating the molding surface area S.sub.1, a substep E3 of measuring the force F.sub.1 for demolding from the control mold.

(8) The method includes a second step P of determining the molding surface area and the force for demolding from control test specimens. This step is split up into a substep P1 of determining a control test specimen with a molding surface area S.sub.0, a substep P2 of measuring the force F.sub.0 for demolding from the control test specimen. This step P requires a second measurement in order to determine the force F.sub.0 for demolding from a second test specimen with a molding surface area S.sub.0.

(9) The method then includes a first step C1 of defining the surface area ratio R.sub.se by calculating the ratio of the molding surface area S.sub.0 of the first test specimen and S.sub.0 of the second test specimen so as to define a test specimen surface area ratio R.sub.se and a second step C2 of defining the test specimen force ratio R.sub.fe by calculating the ratio of the force F.sub.0 for demolding from the first test specimen and F.sub.0 for demolding from the second test specimen so as to define a test specimen force ratio R.sub.fe.

(10) Next, in a step M1, a mold to be measured is selected, followed by a step M2 of calculating the molding surface area S.sub.m of the mold to be measured, and a step M3 of calculating the force F.sub.m for demolding from the mold to be measured such that F.sub.m=F.sub.1S.sub.m/S.sub.1R.sub.fe/R.sub.se.

(11) The test specimens could, for example, have a profile as illustrated in FIGS. 2 and 3. The test specimen 3 illustrated in FIG. 2 has relatively simple grooves 30, in this case rectilinear and parallel, with a depth h.sub.3, and the test specimen 4 illustrated in FIG. 3 has grooves 40 with a depth h.sub.4 greater than h.sub.3. The molding surface area of the test specimen 4 is thus greater than the molding surface area of the test specimen 3. These test specimens have only horizontal and vertical surfaces since the objective is to measure the surface impact, not the geometric impact. In addition, these test specimens should make it possible to measure the tensile forces generated by the profiles of the tire and shear forces generated by the ribs or grooves. The surface impact is obtained using two test specimens 3 and 4, the surface area in contact of each of which is known exactly. The differences measured between the forces for demolding from each test specimen 3 and 4 make it possible to correlate the forces with the surface impact. The measurements are taken with the same materials as those used to manufacture test casings and with the control mold.

(12) The following table shows examples of values for force and molding surface areas of two test specimens.

(13) TABLE-US-00001 Surface area analysis test specimens test specimen 3 test specimen 4 Surface demolding forces (in daN) 410 445 Test specimen surface area (in mm.sup.2) 25 504 31 883 Test specimen surface area ratio (R.sub.se) 1 1.250 Test specimen force ratio (R.sub.fe) 1 1.085

(14) For this example, this means that, for a given compound, an additional 25% of surface area in contact (of test specimen 4 compared with test specimen 3) generates an additional 8.5% of demolding force.

(15) Using the method, the surface area in contact of the control mold 2 and different mould variants 8 to be measured will be measured and the surface area ratio between the control mold 2 and the variants to be evaluated: mold 81 and mold 82, will be calculated.

(16) TABLE-US-00002 Dimension Dim Dim control mold mold 81 mold 82 Molding surface area (in mm.sup.2) 531 525 657 997 779 559 Mold surface area ratio 1 1.238 1.467

(17) Proceeding from the law of change in the surface impact forces, 25% of the surface area in contact generates an additional 8.5% of demolding forces, and from the above mold surface area ratios, we can determine the coefficient of surface demoldability in accordance with the following formula:
Coefficient of surface demoldability=(mold surface area ratio/R.sub.se)R.sub.fe

(18) In other words, in the above example:
Coefficient of surface demoldability=(mold surface area ratio/1.250)1.085, i.e.

(19) TABLE-US-00003 Dim Dim mold 81 mold 82 Coefficient of surface demoldability 1.075 1.273

(20) In the above example, we can see that, for the mold 82, the surface area in contact is increased by 46.7% compared with the control mold and that the forces induced are greater by 27.3%.

(21) Proceeding from the coefficient of surface demoldability and from the measurement of the forces of a test or control mold, it is possible to assess the demolding forces for a new size. This analysis thus makes it easier to define the production means to be employed (type and power of the curing press, coating, etc.) in order to ensure the manufacture of each size of a range of tires. For each new range, a new control casing and thus a control mold is chosen and it is possible to recalculate the demolding forces for the entire range.

(22) FIG. 5 shows a flowchart of the additional steps in the method in order to take account of the material used.

(23) The additional method includes a step T of determining, for a given reference material (in this case the one used in the preceding steps), forces F.sub.no for demolding from a material test specimen. The method comprises a second step S1 of defining the material to be measured, followed by a step S2 of determining the force F.sub.ni for demolding said material from the material test specimen.

(24) The following step S3 consists in calculating the coefficient of material impact C of the material to be measured, this coefficient C being the ratio of the forces F.sub.no for demolding the reference material and F.sub.ni for demolding the material from the material test specimen:
C=F.sub.ni/F.sub.no.

(25) Next, step S4 is the calculation of the force F for demolding the material to be measured from the control mold such that F=CF.sub.0.

(26) For each new material to be measured, all that will be necessary is to define its coefficient of material impact by repeating the method from step S1.

(27) The device 1 illustrated in FIG. 4 comprises a first test specimen 3, a second test specimen 4, a force measuring device 5, and a calculating means 6. Starting from the two test specimens 3 and 4, the device 1 will be used to calculate the molding surface area S.sub.0 of the first test specimen 3, the molding surface area S.sub.0 of the second test specimen 4, to measure the force F.sub.0 for demolding from the first test specimen 3 and the force F.sub.0 for demolding from the second test specimen 4, and then it will calculate the ratio of the molding surface area S.sub.0 of the first test specimen 3 and S.sub.0 of the second test specimen 4 so as to define a test specimen surface area ratio R.sub.se, and the ratio of the force F.sub.0 for demolding from the first test specimen 3 and F.sub.0 for demolding from the second test specimen 4 so as to define a test specimen force ratio R.sub.fe. The calculating means 6 of the device 1 will also calculate the surface area S.sub.1 of a control mold 2 and the force measuring device 5 will measure the force F.sub.1 for demolding from said control mold 2. When the force F.sub.m for demolding from a mold 8 to be measured needs to be known, all that will be necessary is to calculate the molding surface area S.sub.m of the mold 8 so as to obtain the force F.sub.m for demolding from said mold 8 such that F.sub.m=F.sub.1S.sub.m/S.sub.1R.sub.fe/R.sub.se.