Demoldability prediction model

Abstract

The demoldability prediction model includes the steps of choosing a mold specimen; choosing a reference material; measuring the force F.sub.0 for demolding the reference material from the mold specimen; determining the force M.sub.0 for demolding the reference material from the control test specimen; selecting a material to be measured; determining the force M for demolding the material from the control test specimen; calculating the ratio of the forces M.sub.0 for demolding the reference material and M for demolding the material from the control test specimen so as to define a coefficient C of material impact; and calculating the force F for demolding the material such that F=CF.sub.0.

Claims

1. A method for evaluating a force for demolding a tire from a mold, consisting in measuring the force for demolding a material from a mold specimen and a control test specimen, said method including the steps of: choosing a mold specimen, choosing a reference material, measuring the force F.sub.0 for demolding the reference material from the mold specimen, determining the force M.sub.0 for demolding the reference material from the control test specimen, selecting a material to be measured, determining the force M for demolding the material from the control test specimen, calculating the ratio of the forces M.sub.0 for demolding the reference material and M for demolding the material from the control test specimen so as to define a coefficient C of material impact, and calculating the force F for demolding the material such that F=CF.sub.0.

2. The method according to claim 1 further including the step of measuring a second specimen such that the force M.sub.1 for demolding from this second specimen is greater than the force M.sub.0.

3. The method according to claim 2, wherein the force M.sub.0 for demolding constitutes a lower limit and the force M.sub.1 constitutes an upper limit.

4. The method according to claim 1, wherein the evaluation of the force M for demolding a second material is limited to the following steps of: determining the force M for demolding the second material from the control test specimen, calculating the ratio of the forces M.sub.0 for demolding the second reference material and M for demolding the second material from the control test specimen so as to define a coefficient C of material impact, calculating the force F for demolding the second material such that F=CF.sub.0.

5. The method according to claim 1, wherein the mold specimen is chosen from a region of the mold where the demolding force is greatest.

6. The device for selecting a material/mold pair, wherein it comprises a mold specimen, a control test specimen, a force measuring device and a calculating means and in that it uses the method according to claim 1.

7. A method of selecting a material/mould pair that meets the condition that the force F for demolding the material is less than a predetermined demolding force comprising the steps of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

(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 illustration:

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

(3) FIG. 2 shows a selection device according to the disclosure.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT

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

(5) The method includes a step E of determining, for a reference material 6, the forces F.sub.0 for demolding from a mold and M.sub.0 from a control test specimen 3. This step E comprises a substep E1 of defining a mold specimen 2 from a curing mold for a tire, a substep E2 of choosing a reference material 6, a substep E3 of measuring the force F.sub.0 for demolding the reference material 6 from the mold specimen 2, and a substep E4 of determining the force M.sub.0 for demolding the reference material 6 from the control test specimen 3.

(6) This step E requires two measurements, one for the mold specimen 2 and one for the control test specimen 3.

(7) The method comprises a second step P1 of defining the material 7 to be measured, followed by a step P2 of determining the force M for demolding the material 7 from the control test specimen 3.

(8) The following step P3 consists in calculating the coefficient of material impact C of the material 7 to be measured, this coefficient C being the ratio of the forces M.sub.0 for demolding the reference material 6 and M for demolding the control 7 from the control test specimen 3:
C=M/M.sub.0.

(9) Next, step P4 is the calculation of the force F for demolding the material 7 to be measured from the mold specimen 2 such that F=CF.sub.0.

(10) For each new material 7 to be measured, all that will be necessary is to define its coefficient of material impact by repeating the method from step P1. It will thus be understood that determining the force for demolding this material from the mold requires only one measurement, that of the force for demolding from the control test specimen, thereby considerably reducing costs.

(11) In order to make it easier to choose a type of tread pattern, a test specimen of the molds can be produced with a top limit and a bottom limit for each variant to be evaluated of a material. The top limit corresponds to easy demolding and the top limit corresponds to difficult demolding.

(12) The following table shows examples of easy (bottom control) and difficult (top control) demolding force values.

(13) TABLE-US-00001 Bottom Top control Variant A Variant B control Test specimen 374 452 472 570 demolding forces (in daN) Coefficient of 1 1.2086 1.2620 1.5241 test specimen demoldability Materials used X Y Y Z

(14) In this table, the different mold variants have been measured with different materials X, Y and Z. The method makes it possible to use these measurements to define the forces for demolding different materials without requiring new measurements with the different mold variants.

(15) Specifically, it is easy to measure the force for demolding from a control test specimen 3 which is simple, without tread patterns and has a planar shape. This makes it possible to classify the different materials with respect to one another. Thus, if the material X were taken as reference, the following Table T1 would be obtained for example:

(16) TABLE-US-00002 Material analysis test specimen Compound X Compound Y Compound Z Material demolding 318 340 404 forces Coefficient of 1 1.0692 1.2704 material impact

(17) It can thus be seen that material Y generates 7% more forces and material Z 27% more.

(18) By contrast, if Y is taken as reference material, the following Table T2 is obtained:

(19) TABLE-US-00003 Material analysis test specimen Compound X Compound Y Compound Z Material demolding 318 340 404 forces Coefficient of 0.9353 1 1.1882 material impact

(20) It can be seen that material Y generates 19% more forces than Z.

(21) From these measurements, it is possible to extrapolate the demoldability of the different variants using different materials without repeating a set of measurements which would associate variant/compound. It is thus possible to evaluate variants A and B with materials X or Z while the measurements were taken with material Y, the following Table T3 then being obtained for X:

(22) TABLE-US-00004 Bottom Top control Variant A Variant B control Coefficient of 1 1.2086 1.2620 1.5241 test specimen demoldability Materials used X Y Y Z Materials to be X X X Z evaluated Coefficient of 1 0.9353 0.9353 1 material impact Coefficient of 1 1.1304 1.1803 1.5241 mold demoldability

(23) And the following Table T4 for Z:

(24) TABLE-US-00005 Bottom Top control Variant A Variant B control Coefficient of 1 1.2086 1.2620 1.5241 test specimen demoldability Materials used X Y Y Z Materials to be X Z Z Z evaluated Coefficient of 1 1.1882 1.1882 1 material impact Coefficient of 1 1.4361 1.4996 1.5241 mold demoldability

(25) It can thus be seen that when the material to be evaluated is identical to the material used on the test specimen, the coefficient of material impact is 1, and when the material to be evaluated is different from that used for the test specimen, the coefficient of material impact is different. In Table T3, it can be seen that using compound X on variants A and B makes it possible to reduce the forces (by around 7%) compared with Y. By contrast, it is found that by using compound Z on variants A and B, the resulting forces are close to the top control (which is the limit not to be exceeded). It is possible to conclude therefrom that either it is necessary to redefine the tread pattern of the different variants or it is necessary to modify the composition of compound Z to reduce the forces. It is therefore possible with this method to predict the demoldability of new tread patterns associated with different compounds without having to repeat a set of specific force measurements for each variant.

(26) The device 1 illustrated in FIG. 2 will now be described. This device 1 comprises a mold specimen 2, a control test specimen 3, a force measuring device 4 and a calculating means 5. The device is used to measure the force F.sub.0 for demolding a reference material 6 placed in the mold specimen 2 and then the force M.sub.0 in the control test specimen 3 by means of the measuring device 4. Said device 1 is then used to measure the force M for demolding the material 7 to be measured and then to use the calculating means 5 to calculate the coefficient C of material impact and the force F for demolding the material 7 from the mold specimen 3.