GB2327390A

GB2327390A - Tyre manufacture

Info

Publication number: GB2327390A
Application number: GB9715449A
Authority: GB
Inventors: Eric Holroyd; Colin Holroyd
Original assignee: Holroyd Associates Ltd
Current assignee: Holroyd Associates Ltd
Priority date: 1997-07-23
Filing date: 1997-07-23
Publication date: 1999-01-27
Also published as: WO1999004957A1; AU8547298A; GB9715449D0

Abstract

A circular support 26 defines a peripheral surface for supporting a tyre carcass during manufacture, the peripheral surface corresponding substantially to the intended final shape of the tyre. Tensioning means 42 receives ply material 40 and applies a different tension to a central portion of the material than is applied to side portions thereof so that the material assumes the profile of the peripheral surface.

Description

Title: ImDrovements in Tvre Manufacture The present invention is concerned with apparatus and a method for use in the manufacture of a pneumatic tyre.

Pneumatic tyres are generally composed of several layers of material superimposed for their specific structural properties.

One such layer is known as the ply, which can be incoprporated with an inner liner and which together can be the first layer to be laid down during manufacture of a tyre. The ply is a band of material formed as a planar strip and having a plurality of reinforcing ply cords. In the past, a tyre has been manufactured by laying down the ply over a generally cylindrical support and building up other layers of the tyre thereover. The tyre has then been expanded to its final shape. GB-A-2212460 shows such a technique, where two tyres are formed simultaneously on the same machine.

Furthermore, techniques have been used in the past to form sections of tubular ply material by winding an elongate strip helically around a former, and cutting the wound strip transversely. The flat sheet so produced is then reoriented so that the cut edges extend circumferentially of a second former.

If an axial reinforcing cord is contained within the strip, the cord will be oriented in the axial direction of the second former. The sheet can then be expanded from the second former to produce a toroidal tyre shape.

That is disclosed in United Kingdom Patent Applications GB-A2216468, GB-A-22164569 and GB-A-2216485. In all those cases, additional machinery must be provided for the expansion of the ply material from the cylindrical to a toroidal form, which requires significant energy consumption.

United Kingdom Patent 877480 describes apparatus which forms rubber sheet directly into a near final tyre shape. In that apparatus, a tyre shaped former is used to draw a sheet of rubber from a dispenser. GB-A-2138351 shows similar equipment but, in that case, the former is merely cylindrical.

It is an object of the invention to provide an alternative apparatus and method for shaping ply material into a near-final tyre shape.

According to a first aspect of the invention there is provided apparatus for use in tyre manufacture, the apparatus comprising a circular support defining a peripheral surface for supporting a tyre carcass during manufacture, the peripheral surface corresponding substantially to the intended final shape of a tyre to be constructed, and tensioning means, suitable for receiving ply material, for applying a different tension to a central portion of said material than is applied to side portions thereof so that said material in use assumes the profile of the peripheral surface, and presenting said ply material to said peripheral surface.

By basing tyre construction on a support having an external shape substantially corresponding to the final shape of the tyre to be formed, there is no need for means to be provided for expanding a cylindrical tyre blank to its final toroidal shape. In contrast, in order to move sufficient material to form a toroidal tyre from a plane cylindrical blank, heavy tooling must be used in order to accommodate high moulding pressures. Furthermore, the moulding process has a high energy requirement. Therefore, expensive and bulky moulding equipment may be avoided by the present invention because the tyre is formed in its final shape.

In that way, the need for expansion of the tyre blank before curing is mitigated. By tensioning material prior to delivery to the surface of the support, there is no need for the provision of a heavy and bulky former as provided in GB-A-0877480.

Metering means for regulating the rate of delivery of material along the guide means may be provided.

The metering means preferably comprises two rollers mounted for rotation on parallel spaced axes, between which rollers material passes in use.

The guide means may comprise an elongate saddle. The saddle may be arranged generally tangentially of the support.

Furthermore, the saddle of either embodiment may also include means for applying a pressure differential across the ply, to assist with the training of the ply across the saddle.

The gripping means may comprise a gripper bar adjacent the periphery of the support.

In a preferred embodiment of the invention, the apparatus further comprises cutting means for terminating material, such that the material can be terminated once sufficient material has been wound onto the support, in use.

The gripping means may define a cutting face for aligning the cutting means, in use.

According to a second aspect of the invention, there is provided a method of manufacturing a pneumatic tyre comprising the steps of providing a support having a profile on which to build said tyre, providing a length of planar ply material, training said ply material into said profile, gripping an end of said ply material against said support and rotating said support to wind said ply material around said support.

The step of providing material may include the step of regulating the rate of delivery of said material relative the rate of rotation of said support.

The step of regulating the rate of delivery preferably comprises passing the material through braking means.

In a preferred embodiment of the invention, the rate of delivery of said material is at most the same as the linear speed of the radially innermost edge of material wound on the support, such that all material wound on the support is taut.

Preferably, the method further includes the steps of rotating the support through one revolution and cutting the material such that the cut edge created thereby abuts the end gripped in the gripping step.

Further preferred features and advantages of the invention will become apparent from the following description of a specific and preferred embodiment of apparatus for use in tyre manufacture, as illustrated in the drawings appended hereto, in which: Figure 1 shows a side elevation of a rig with a support in accordance with the present invention; Figure 2 shows a schematic diagram of apparatus in accordance with a first specific embodiment of the invention, for winding a ply around the support of figure 1; Figure 3 shows a diagonal view of the support of figure 1 in combination with a saddle guide of the apparatus illustrated in figure 2; Figure 4 shows a diagonal view of the support of figure 1 in combination with apparatus in accordance with a second aspect of the invention and showing the initial stage of a ply layer being wound onto the support; and Figure 5 shows a fragmentary view of a part of the apparatus illustrated in figure 4 and showing the apparatus during the winding of a ply layer onto the support.

Referring firstly to figure 1, a support rig 10 comprises a headstock 12 and a tailstock 14 which are each mounted on a base 16. The headstock 12 and the tailstock 14 are movable towards and away from each other in accordance with arrows 18. Each of the headstock 12 and the tailstock 14 has an elongate bracket 20 extending therefrom.

The brackets 20 are coaxial and are rotatable coaxially relative the headstock 12 and tailstock 14 respectively. Locking means 22 is provided between the two brackets so that the brackets may be rotated in unison. Drive means (not shown) is provided within the headstock 12 and is operative to rotate the bracket 20 of the headstock 12 and, if the locking means is deployed, the bracket 20 of the tailstock 14.

A plurality of circumferentially spaced fingers 24 is mounted at the end of each bracket 20. The fingers 24 of one bracket 20 are interdigitated with the fingers 24 of the other bracket 20. In combination, the fingers 24 define the near final internal shape of a tyre to be supported thereby. Collectively, the fingers 24 define a support 26.

Figure 2 shows apparatus for applying ply material over a support 26 as described above. The apparatus includes a festoon 30 comprising an entry drum 32, an exit drum 34 and an intermediate drum 36. In use, ply 40 is fed over the entry drum 32, around the intermediate drum 36 and over the exit drum 34. Such ply 40 generally includes parallel ply cords which are oriented transverse to the longitudinal direction of the ply which is also the feed direction.

The entry and exit drums 32, 34 are rotatable on parallel axes fixed relative each other; the intermediate drum 36 is rotatable on an axis parallel to the axes of rotation of the other drums but movable relative thereto (in the direction of arrow 38) to vary the distance between the intermediate drum and the other drums.

The apparatus further includes a pre-tensioner 42 to which ply 40 is fed out of the festoon 30. The pre-tensioner 42 comprises two -let-out rolls 44, 46 adjacent one another which are driven to rotate. The let=out rolls are made up of several portions which are arranged to rotate independently, so that different portions of ply passing between the rolls can be imparted with different amounts of strain and pre-tension.

Ply 40 is fed out of the pre-tensioner 42 and over a saddle guide 48. The saddle guide 48 is more clearly illustrated in figure 3, in which it can be seen that the saddle guide 48 has an upper end 50, which has a planar profile, and a lower end 52, which has a profile corresponding to the near final profile of a tyre. The strain introduced in the pre-tensioner causes the ply to curl over the saddle, and take on the profile of the support.

The lower end 52 also has side plates 54 which in use support side portions of the ply fed along the saddle 48.

The saddle guide 48 is arranged tangentially of the support 26 previously described in respect of figure 1. The support 26 is arranged to rotate and so ply 40 is guided on to the circumference of the support 26. A gripper bar 56 is provided on the support 26 for rotation therewith, the gripper bar 56 being operative to hold an end of a length of ply against the surface of the support 26. The gripper bar is shown in figure 2 in a second position with reference 56'.

The circumferential speed of the let out rolls 44, 46 is set to be equal to the circumferential speed of the support 42 at the point where the edge of the ply (where the bead is located) is laid on the support 42. Other speeds can be set for different portions of the ply width as is deemed necessary in order to provide sufficient strain for the ply to take on the desired profile.

The action of the pre-tensioner 42 is to draw the ply out of the festoon 30 and apply a strain thereto. As the ply 40 travels over the saddle guide 48, the ply assumes the profile of the support 26. In that way, the forces associated with inducing the strain in the ply are applied at the pre-tensioner, rather than at the support. The support 26 may therefore be a relatively lightweight structure such as that illustrated in figure 1.

The support 26 is rotated through one complete revolution. The ply is then cut to form a butt joint with the end retained by the gripper bar 56, which may also be used as a cutting edge for cutting the ply 40.

An alternative embodiment of the invention is described with reference to figures 4 and 5. Features which are common to the two specific embodiments are given the same reference numerals herein, and will not be specifically described hereafter.

At the lower end 52 of the saddle guide 48, let out rolls 58, 60, 62 are situated against the three portions of the saddle guide.

The middle roll 60 of the three is adjacent the crown of the profile, and the two side rolls 58, 62 are arranged to be adjacent the side portions of the profile, i.e. at the bead radius. The rolls are driven at differential speeds so that ply passing adjacent the middle roll 60 is imparted a strain relative the outer portions of the ply. In that way, the ply cords in the region of the crown are separated, to allow controlled shaping of the ply before it reaches the support 26.

It will be noted that the gripper bar 56 of the second embodiment is of a slightly different construction from that disclosed in figure 2, but the differences are not significant. The purpose of the gripper bar 56 is to hold the ply against the support while the support is rotated, and ply is wound thereon.

As shown in figure 5, as the ply is wound onto the support, and the support is rotated, clamps 64 are progressively applied to the bead radius portion of the support so that the ply is unable to move once it has been applied to the support. In that way, the ply is able to define a near final tyre shape without any expansion steps or the like.

It is clear from the above that the embodiments described herein is significantly advantageous in that the support can be made a more lightweight construction, since forces associated with the introduction of strain to the ply are not imparted to the support. Furthermore, by applying strain at the let-out rolls, the strain may be controlled closely and accurately, to provide an accurate fit of ply around the support.

Claims

1. Apparatus for use in tyre manufacture, the apparatus comprising a circular support defining a peripheral surface for supporting a tyre carcass during manufacture, the peripheral surface corresponding substantially to the intended final shape of a tyre to be constructed, and tensioning means, suitable for receiving ply material, for applying a different tension to a central portion of said material than is applied to side portions thereof so that said material in use assumes the profile of the peripheral surface, and presenting said ply material to said peripheral surface.

2. Apparatus according to claim 1 wherein the support is axially rotatable relative the tensioning means, the apparatus further comprising gripping means rotatable with the support for gripping a piece of ply material against the support.

3. Apparatus according to claim 2 further comprising guide means, the guide means being generally elongate and having a lateral profile transitioning along its length from a generally planar profile distal the support to a profile adjacent the support generally corresponding to the profile of the peripheral surface of the support.

4. Apparatus according to claim 3 wherein the guide means comprises an elongate saddle.

5. Apparatus according to claim 4 wherein the saddle is arranged generally tangentially of the support.

6. Apparatus according to any one of claims 3 to 5 and comprising metering means for regulating the rate of delivery of material along the guide means.

7. Apparatus according to claim 6 wherein the metering means comprises two rollers mounted for rotation on parallel spaced axes, between which rollers material passes in use.

8. Apparatus according to any one of claims 3 to 7 wherein the gripping means comprises a gripper bar adjacent the periphery of the support.

9. Apparatus according to any one of claims 2 to 8 further comprising cutting means for terminating material.

10. Apparatus according to claim 9 wherein the gripping means defines a cutting face for aligning the cutting means, in use.

11. Method of manufacturing a pneumatic tyre comprising the steps of: providing a support having a profile on which to build said tyre; providing a length of planar ply material; introducing a strain into at least a portion of said ply material such that said material assumes said profile; and applying said ply material to said support.

12. Method according to claim 11 wherein the strain is introduced into a portion substantially midway between the two edges thereof.

13. Method according to claim 11 or claim 12 further comprising the step of gripping an end of said ply material against said support

14. Method according to any one of claims 11 to 13 wherein the step of providing material includes the step of regulating the rate of delivery of said material relative the rate of rotation of said support.

15. Method according to claim 14 wherein the rate of delivery of said material is at most the same as the linear speed of the radially innermost edge of material wound on the support, such that all material wound on the support is taut.

16. Method according to any one of claims 11 to 15 and further comprising the steps of rotating the support through one revolution and cutting the material such that the cut edge created thereby abuts the end gripped in the gripping step.

17. Apparatus for use in tyre manufacture as described herein, with reference to figures 1, 2 and 3 of the accompanying drawings.

18. Method of manufacturing a pneumatic tyre as described herein, with reference to figures 1, 2 and 3 of the accompanying drawings.

19. Apparatus for use in tyre manufacture as described herein, with reference to figures 1, 4 and 5 of the accompanying drawings.

20. Method of manufacturing a pneumatic tyre as described herein, with reference to figures 1, 4 and 5 of the accompanying drawings.