Method for cutting a strip of tire reinforcing product comprising wires at an angle to the longitudinal direction of the product

Abstract

The method includes the step of running a cutting means between two threads of the reinforcing ply. The method proceeds with the steps of measuring; a discrepancy between an actual cutting line (ABC) and a theoretical cutting line (ABC) is measured and determining a point of intersection of the actual cutting line (B) with a reference longitudinal line (XX) placed on the strip. The actual cutting line (BC) of that part of the rubber profiled elements that are not superposed with the reinforcing ply is longitudinally offset (Z) with respect to the theoretical cutting line (BC) so that the actual cutting line (BC) meets the reference longitudinal line (XX) at the point of intersection (B) of the reinforcing ply (AB) with the reference longitudinal line (XX). The rubber profiled elements that are not superposed with the reinforcing ply are cut along the said actual cutting line.

Claims

1. A method for cutting to length a strip formed of preassembled products comprising one or more rubber profiled elements superposed in part on a reinforcing ply made up of threads coated in rubber and making an angle (a) with a longitudinal direction of the strip, comprising: a cutting means (6) running a cutting means between two threads of the reinforcing ply, measuring a discrepancy between an actual cutting line (ABC) and a theoretical cutting line (ABC), and determining a point of intersection of the actual cutting line (B) with a reference longitudinal line (XX) placed on the strip, wherein the actual cutting line (BC) of that part of the rubber profiled elements that are not superposed with the reinforcing ply is longitudinally offset (Z) with respect to the theoretical cutting line (BC) so that the said actual cutting line (BC) meets the reference longitudinal line (XX) at the point of intersection (B) of the actual cutting line of the reinforcing ply (AB) with the said reference longitudinal line (XX), and the rubber profiled elements that are not superposed with the reinforcing ply are cut along the said actual cutting line.

2. The method according to claim 1, further comprising, prior to cutting, positioning the strip in the frame of reference of the cutting device so that the reference longitudinal line (XX) of the strip is arranged at a known location.

3. The method according to claim 1, wherein, in order to cut the reinforcing ply, use is made of a cutting means (6) able to assess the position of the cutting line.

4. The method according to claim 3, wherein the means of cutting the reinforcing ply comprises a cutting wheel of circular shape that can be oriented according to the angle formed by the threads with the longitudinal direction of the strip (a) and which is free to move in the direction of its axis of rotation (rr).

5. The method according to claim 1, wherein the discrepancy between the actual cutting line (AB) and the theoretical cutting line (AB) is determined by measuring a distance (d.sub.1, d.sub.2) between these two lines at two distinct points (P.sub.1, P.sub.2).

6. The method according to claim 1, wherein the cutting means continues to be run between the threads beyond the point of intersection (B) of the actual cutting line (AB) and of the reference longitudinal line (XX) by a short distance of given value (), so as to make it easier to detach the portion of strip after the part of the rubber profiled elements that are not superposed with the reinforcing ply have been cut.

7. The method according to claim 1, wherein in which the cutting line (BC) of that part of the rubber profiled elements that is not superposed with the reinforcing ply makes an angle with the longitudinal direction equal to the angle (a) of the threads of the reinforcing ply.

8. The method according to claim 1, wherein the cutting line (BC) of the part of the rubber profiled elements that is not superposed with the reinforcing ply makes an angle with the longitudinal direction that differs from the angle (a) of the threads of the reinforcing ply.

9. The method according to claim 8, wherein the cutting line of the part of the rubber profiled elements that is not superposed with the reinforcing ply makes a right angle with the longitudinal direction of the strip.

10. The method according to claim 1, wherein, prior to cutting, the strip is moved under the cutting means by a given set length (L) so as to form, after cutting, a portion of strip which is intended to be applied by winding to a tire-building drum of given circumference.

11. The method according to claim 10, wherein the set length (L) of the portion of strip is adjusted so that it is equal to the circumference of the tire-building drum less a maximum given longitudinal offset (Z.sub.max).

12. A method of applying a portion of strip formed of preassembled products comprising one or more rubber profiled elements and a reinforcing ply made up of threads coated in rubber and making an angle (a) with the longitudinal direction of the strip cut according to the method according to claim 10, wherein tension with which the portion of strip is applied to the tire-building drum is adjusted according to a set length (L) increased by the value of the longitudinal offset (Z) of the actual cutting line.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The following description is supported by FIGS. 1 to 4 in which:

(2) FIG. 1 depicts a schematic perspective view of a first type of strip formed of preassembled products

(3) FIG. 2 depicts a schematic perspective view of a second type of strip formed of preassembled products

(4) FIG. 3 depicts a schematic view in cross section and in a view from above of the strip of preassembled products

(5) FIG. 4 depicts a schematic perspective view of a cutting means suited to implementing the method according to the invention

(6) FIG. 5 depicts a geometric view which serves as a basis for calculating the offset.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(7) The strip of product 1 depicted in FIG. 1 comprises a reinforcing ply 2 formed of threads 21 coated in rubber and making a given angle with the longitudinal direction of the strip embodied by the dotted line XX. The reinforcing ply is assembled with rubber profiled elements 3, 4, 5. It may be seen that, in the transverse direction of the strip, the reinforcing ply does not completely cover the profiled rubber products 3, 4 and 5.

(8) FIG. 2 depicts a similar assembly in which the reinforcing ply 2 comprises, on one of its selvedges, an edging rubber 5.

(9) The line XX also represents the reference longitudinal line which may be positioned transversely at a known distance from the two lateral edges of the strip of product. For obvious practical reasons it is often considered that only one of the lateral edges of the strip is used as a reference from which the reference longitudinal line XX that will serve as a basis for the cutting operation explained in the paragraphs which follow will be positioned.

(10) FIG. 3 illustrates, in a view from above, the theoretical path of the cutting line for the strip formed of a first part AB for cutting of the reinforcing ply, ideally passing between two threads and therefore making an angle equal to the inclination of the threads with the longitudinal direction of the strip, followed by a second part BC for cutting of the part of the rubber profiled elements which are not superposed with the reinforcing ply. The point B, situated on the reference line XX, constitutes the point at which the two parts of the cutting line ABC meet.

(11) It will be pointed out here that this second part of the cutting line may make, with the longitudinal direction of the strip, an arbitrary angle different from the angle formed by the threads. This angle may usually be equal to 90 as in the case illustrated in FIG. 3, but may just as easily be equal to the angle , which amounts to defining a rectilinear cutting line making an angle with the longitudinal direction. However, this second scenario remains restricted to a relatively high angle , so as to limit the length of the butting edge.

(12) FIG. 4 illustrates a cutting means suited to evaluating the actual position of the cutting line when this line does not correspond to the theoretical cutting line.

(13) This type of floating cutter, that allows the actual cutting line to be adapted by passing between the threads, is described in detail in publication U.S. Pat. No. 4,857,123 or alternatively in publication WO 2011/076558 one of the embodiments 6 of which is reproduced in FIG. 4.

(14) According to this embodiment, the cutting wheel 60 revolves freely about an axle 61 the orientation rr of which is substantially parallel to the plane of the reinforcing ply when the cutting device is in operation.

(15) The axle 61 of the cutting wheel 60 is connected to a drive support 67 moving substantially in a direction tt parallel to the theoretical direction of the threads, by an articulated frame comprising two link rods 62a and 62b connected by articulations 67a, 67b (which is not visible), 68a, 68b (which is not visible), each to the two ends of an axle 66 secured to the support 67. The direction ss of the axle 66 is parallel to the direction rr of the axle 61 on the one hand, and to the two ends of the axle 61 of the cutting wheel 60 on the other.

(16) The axles of the link rods, respectively 67a, 67b, 68a, 68b, are substantially parallel to the direction ZZ perpendicular to the plane of the reinforcing ply so that movement of the cutting wheel 60 in the direction rr is accompanied by a pivoting of the link rods about the articulations 67a, 67b, 68a, 68b.

(17) The force with which the wheel is applied to the ply comes from the action of an actuating cylinder 64 on an arm 65 fixed to the axle 66.

(18) When the link rods 62a and 62b are parallel, the plane of the wheel 60 remains perpendicular to the direction rr and substantially parallel to the direction tt.

(19) During operation of the cutting means attempts are made to make the path tt of the drive support correspond to the theoretical cutting line AB and all that is required is for sensors to be used to record the movements of the cutting wheel in the direction rr in order to assess the actual path of the wheel as it moves between two threads in an actual path which may potentially differ from the theoretical path.

(20) In order to cut the rubber profiled elements which are not superposed with the reinforcing ply and, failing that, block in the direction rr the movements of the cutting wheel which is no longer guided by the threads between which it was previously running, it is preferable to use a separate cutting means, such as a cutting blade the length of which is equal to the length of the cutting edge.

(21) In this regard, by choosing an angle of 90 the length of the cutting blade used to make the cut along the segment BC is limited.

(22) FIG. 5 illustrates a means of evaluating the actual path ABC of the cutting means.

(23) As a preamble to evaluating the actual path, the strip needs to be positioned precisely in the frame of reference of the cutting device. To do that, the reference side of the strip will be aligned for example along a fixed edge connected with the chassis on which the said cutting device is mounted. The location of the theoretical cutting line ABC is then determined by unwinding the strip by a given set length L, corresponding substantially, after the adjustments which will be explained in what follows have been taken into consideration, to the development of the accepting surface of the tire-building drum onto which the portion of strip that is to be obtained is intended to be laid. The precision of this positioning can also be improved by use of means of detecting the front cutting edge of the strip.

(24) The reference line XX is then positioned precisely with respect to the frame of reference of the cutting device. In a practical way, steps are taken to ensure that this reference line XX is situated slightly beyond the inside edge of the reinforcing ply so as to ensure that the cutting blade of the rubber profiled elements that are not superposed with the reinforcing ply will not strike the end of a thread of the ply.

(25) As mentioned hereinabove, the cutting of the strip is then begun by causing the cutting means 6 to penetrate the reinforcing ply. The cutting blade therefore runs between two reinforcing threads along a path AB which is not necessarily superposed with the theoretical path AB.

(26) This path may be offset longitudinally but may also differ by an angle from the theoretical path based on the angle of the threads 21 of the reinforcing ply 2.

(27) When the wheel reaches the point P.sub.1 situated at a distance M.sub.1+M.sub.2 from the point A, the discrepancy d.sub.1 between the theoretical path and the actual path is then evaluated. And, when the wheel passes the point P.sub.2, distant by M.sub.2 from the point A, the distance d.sub.2 separating the theoretical path from the actual path is measured.

(28) It is then an easy matter, using simple geometric calculations, to determine the additional path that the wheel has to be made to cover in order for it to meet the reference line XX

(29) $\mathrm{Tan}=\frac{d_1-d_2}{M_1}$$=\frac{1}{\cos }\frac{M_1{d}_2+M_2{d}_2-M_2{d}_1}{d_1-d_2+M_1\tan }$

(30) The progress of the cutting means can also be extended beyond the point B over a distance that is generally short, 4 or 5 millimeters for example, in order to ensure that the cutting lines AB and BC are clean and allow the portion of strip to be detached effortlessly.

(31) The distance Z between the point B and the point B is also calculated.

(32) $Z=\frac{1}{\cos }\frac{M_1{d}_2+M_2{d}_2-M_2{d}_1}{d_1-d_2+M_1\tan }$

(33) This distance Z is used to determine the positioning of the cutting line BC for rubber profiled elements which are not superposed with the reinforcing ply.

(34) The second cutting means is accordingly moved by the value of the offset Z, and the rest of the strip is cut.

(35) The way of determining the values and Z which has been set out hereinabove is not in any way limiting on the application of the method that forms the subject matter of the invention and alternative ways at arriving at a similar result are many so long as the movements of the cutting blade in the frame of reference of the cutting device can be determined accurately.

(36) It is beneficial to note that the fact of moving the cutting line by the value of the offset Z of the actual cutting line ABC with respect to the cutting line ABC substantially alters the length L that had been chosen for the portion of strip intended to be applied to the tire-building drum.

(37) As a result, the method may conceive of putting the precise knowledge of this offset Z to use in each cutting operation in order to adjust accordingly the tension with which the said portion is laid. To do that, a value Z.sub.max corresponding to the maximum correction value Z observed over a significant number of samples may be determined experimentally.

(38) A choice is then made to cut the portion of strip to a length L equal to the laying circumference of the tire-building drum less the length Z.sub.max. The actual length to be laid will then be equal to the length L plus the actual correction Z. The total of these two lengths will remain slightly shorter than the development of the receiving surface, which will allow the portion of the strip of preassembled products to be laid under tension. Knowing the value of Z, and therefore the actual length of the said portion, it is then easy to determine the coefficient of elongation to make the strip undergo while it is being wrapped around the tire-building drum.