WO1999004955A1

WO1999004955A1 - Improvements in tyre manufacture

Info

Publication number: WO1999004955A1
Application number: PCT/GB1998/002192
Authority: WO
Inventors: Eric Holroyd; Colin Holroyd
Original assignee: Holroyd Associates Limited
Priority date: 1997-07-23
Filing date: 1998-07-22
Publication date: 1999-02-04
Also published as: GB9715452D0; GB2327392A; AU8454398A

Abstract

A tread package for a pneumatic tyre comprises two tread sub-packages (106). The sub-packages (106) are annular. Each sub-package (106) has an annular abutment surface lying in a plane substantially perpendicular to the axis of the sub-package such that the abutment surfaces of the sub-packages can be fitted together to constitute a tyre shape.

Description

Title: Improvements in Tyre Manufacture

The present invention relates to improvements in tyre manufacture, and particularly to components, a method and apparatus for use in the final stages of tyre manufacture.

In practice, a tyre is manufactured by building a tyre carcass on a former. Typically, a tyre carcass comprises a plurality of layers and tyre beads. Once a tyre carcass has been constructed in that way, a tread package and sidewalls must be fitted thereto. That has previously been achieved in a number of ways.

For instance, a tread package could be provided as an elongate strip then laid over an expanded tyre carcass. Alternatively, a tread package could be provided as a self contained article in a forming mould; an unexpanded tyre carcass could then be placed therein and expanded into place. Such a method is demonstrated in U.K. Patent 1471547, and in U.K. Patent Applications GB-A-2134439, GB-A-2133357 and GB-A-2185211.

Both of the above methods require the movement of a significant amount of material. Consequently, the machinery required to carry out the methods must include heavy components, which adds to expense and to energy consumption. Therefore, it is an object of the present invention to provide means for ameliorating the above problems.

According to a first aspect of the invention, there is provided a tread package for a pneumatic tyre, the tread package comprising two tread sub-packages, the sub-packages being annular and each sub-package having annular abutment surfaces lying in a plane substantially peφendicular to the axis of said sub package such that said abutment surfaces of said sub-packages can fitted together to comprise a tyre shape.

The invention as described above is advantageous because the two tread sub-packages can be brought into contact with a tyre carcass without the need to change the shape or size of the tread package after fitting. Therefore, heavy moulding equipment previously used can be dispensed with.

The abutment surface may be annular.

In a preferred embodiment, each sub-package comprises a radially outwardly extending flange adjacent said annular abutment surface. In that way, the flanges can contact each other to locate the sub-packages for adhesion.

Preferably; each sub-package comprises a sidewall and a tread layer extending from said sidewall, said annular abutment surface being defined along a free edge of said tread layer, and a radially outwardly extending flange adjacent said free edge of said tread layer. Such an integrated tread package is advantageous since the entire finishing stage in the manufacture can thereby be carried out at one plant station.

The sub-packages may be substantially identical. In that way, cost savings may be achieved in that one piece of equipment may be used to manufacture both sub-packages.

According to a second aspect of the invention, there is provided a method of forming a pneumatic tyre with a tread package as defined in any preceding claim including the steps of providing a tyre carcass on a support, providing the two sub-packages in respective housings either side of said support, moving said housings towards said support to fit said sub-packages to said carcass and to each other, and applying heat to the tread package and carcass combination for vulcanisation thereof.

The method preferably further includes the steps of applying pressure differentials to the carcass in order to obtain a suitable fit of the carcass within the tread package.

The two sub-packages are preferably incompletely vulcanised before commencement of the method. In that way, the sub-packages are initially less susceptible to distortion through stress than would be the case it they were completely unvulcanised; the step of applying heat preferably causes completion of the previously incomplete vulcanisation.

According to a third aspect of the present invention there is provided apparatus for performing the above described method, the apparatus comprising a base, a support mounted on the base and two package housings arranged one either side of the support, the package housings being movable towards the support.

Preferably, the apparatus further comprises means for imparting a pressure differential to a tyre carcass on the apparatus in use.

In a preferred embodiment of the invention, the support is detachable from the base. In that way, the support can be used as transport means to bring a tyre carcass to the apparatus; a green tyre carcass is extremely susceptible to distortion through stress and so it is desirable that it is not moved from one support to another during the manufacturing process.

Further aspects and advantages of the present invention will become apparent from the following description of a specific and preferred embodiment of the present invention, with reference to the accompanying drawings in which:

Figure 1 shows a side elevation of apparatus suitable for producing a tread package in accordance with the invention;

Figure 2 shows a side elevation of the apparatus illustrated in figure 1 at a later stage of use;

Figure 3 shows a side elevation of a support for performing a method of forming a tyre in accordance with the invention;

Figure 4 shows a side elevation of an assembly station comprising a specific embodiment of the invention and in an initial state; Figure 5 shows a side elevation of the assembly station of figure 4 in a first intermediate state;

Figure 6 shows a side elevation of the assembly station of figure 4 in a second intermediate state; and

Figure 7 shows a side elevation of the assembly station of figure 4 in a final state.

As illustrated in figure 1, a mandrel 100 is provided having a generally circular periphery. The mandrel 100 comprises an annular diaphragm 102 with an inflatable bladder 104 within the diaphragm 102. Inflation of the bladder 104 causes radial expansion of the diaphragm 102. An annulus 106 of elastomeric material is formed around the diaphragm 102.

A jig 108 is illustrated in figure 1 , in position to be placed over the mandrel 100. The jig 108 is circular and concave, and laid in the jig 108 are the components of a sidewall of a tyre (omitted for clarity). The jig 108 also includes a tread grid 110 which defines a tread pattern of a tyre to be formed.

As shown in figure 2, the jig 108 is placed over the mandrel 100 and the sidewall and the annulus 106 come together. The bladder 104 of the mandrel 100 is inflated and the diaphragm is caused to move radially outwardly. In that way, the tread grid 110 moulds into the annulus 106 and defines a tread pattern therein. In that way, a half tyre tread package 112 is formed, the package comprising a tread portion and a sidewall.

As illustrated in figure 3, a support 10 comprises two halves 12, 14. Each half 12, 14 has a cylindrical body 16. The cylindrical body 16 has front and rear circular faces 18, 20. The front faces 18 of the respective bodies 16 face each other as illustrated in figure 3. The front face of each body 16 includes an axial attachment 22 for releasable attachment to the corresponding feature of the other body 16. In that way, the halves 12, 14 are releasably connectable to one another. A plurality of fingers 24 are spaced around the circumference of the front face 18 of each body 16. Each finger 24 has a supporting arm 26 corresponding generally to a half profile of a tyre to be constructed, and a locating arm 28 substantially peφendicular thereto. Each finger 24 is pivotally mounted on the respective body 16 in a plane radial of the body 16 and on an axis tangential of the body 16 so that the locating arm 28 is directed generally radially inwardly of the body 16.

The front face 18 of each body 16 includes a circular recess 30. A circular locking plate 34 is provided on each half 12, 14 of the support 10, about the axial attachment 22, and is arranged to move axially in to and out of the recess. The locking plate 34 abuts the locating arm 28 of- each finger 24. In that way, movement of the locking plate 34 out of the corresponding recess 30 is operative to splay the supporting arms 26 of the fingers 24 radially outwardly.

The right hand half 14 of the support 10 of figure 3 illustrates two possible positions of the fingers 24 and the locking plate 34. The finger 24A illustrated in ghosted line is in a withdrawn or retracted position and the corresponding position of the locking plate has reference numeral 34A. The other position of the locking plate 34 corresponds with the extended position of the finger 24 illustrated in solid line.

The fingers 24 of the two halves 12, 14 are interdigitated in order to prevent clashes from occurring during movement of the fingers 24.

Adjacent the fingers 24 on the periphery of the body 16 of each half 12, 14 of the support 10 is a circumferentially extending bladder 36. On inflation of the bladder 36, a metal turn up 38 is caused to extend radially outwardly of the body 16.

The rear face 20 of each half 12, 14 has attachment means to allow attachment of the support to an assembly station, in a manner to be described below.

Figure 4 shows an assembly station 40 comprising a headstock 42 and a tailstock 44. Each of the headstock 42 and the tailstock 44 has a cylindrical attachment portion 46 having attachment means corresponding to that of the rear face 20 of a half of the support 10. The attachment portions 46 have control means for controlling the positions of the locking plates 34 and to attach and release the axial attachments 22 of the support 10. Suitable control means could be connecting rods.

A support 10 as described above is shown in figure 4 being introduced into the station 40. The support has been passed through previous processes such that the support has a green tyre carcass applied around it, with bead and apex packages, and breaker strip.

The station 40 has a support rod 48 parallel with and generally above the axis of the headstock 42 and tailstock 44. Suspended from the rod are two formers 50, around respective attachment portions 46, holding half tyre tread packages 112 which may be formed as described above with reference to figures 1 and 2. The tread packages 112 illustrated in figures 4 to 7 include radially outwardly extending flanges which may be removed after the presently described process.

In figure 5, the support 10 as previously described is shown installed into the station 40. The formers 50 are shown being moved along the rod 48 closer to the support 10 for fitting of the half tyre tread packages 112 thereabout.

In figure 6, the formers have now been withdrawn leaving the tread packages 112 in place around the support 10. The fingers 24 of the left hand half 12 of the support 10 are retracted and by the application of pressure, the green carcass and the left hand half of the tread package 112 are conformed to shape. The axial attachments 22 are released and the left hand half 12 of the support 10 is withdrawn away from the right hand half 14. Subsequently, the same process is undergone in respect of the right hand half of the tyre carcass and tread package 112, with the constituent parts being conformed to shape by the application of pressure as the fingers 24 of the right hand half 14 of the support 10 are retracted, as shown in figure 7. In that figure, means for supporting the tyre are omitted for clarity. The present invention allows the moulding and fitting of rounded tyre packages without the need for complicated equipment to be used. The joint in the outer layer of the finished tyre between the two half tyre tread packages is obliterated by subsequent curing and, in any event, the joint can be reinforced by a breaker strip laid across the width of the tyre carcass prior to the fitting with the half tread packages 112.

Claims

1. A tread package for a pneumatic tyre, the tread package comprising two tread sub-packages (106), the sub-packages (106) being annular and each sub-package (106) having an annular abutment surface lying in a plane substantially pe╧åendicular to the axis of said sub package such that said abutment surfaces of said sub-packages can fitted together to constitute a tyre shape.

2. A tread package according to claim 1 wherein each sub-package (106) comprises a radially outwardly extending flange adjacent said annular abutment surface.

3. A tread package according to claim 2 wherein each sub-package (106) comprises a sidewall and a tread layer extending from said sidewall, said annular abutment surface being defined along a free edge of said tread layer, and a radially outwardly extending flange adjacent said free edge of said tread layer.

4. A tread package according to any preceding claim wherein the sub-packages (106) are substantially identical.

5. Method of forming a pneumatic tyre with a tread package as defined in any preceding claim including the steps of providing a tyre carcass on a support, providing the two sub-packages in respective housings either side of said support, moving said housings towards said support to fit said sub-packages to said carcass and to each other, and applying heat to the tread package and carcass combination for vulcanisation thereof.

6. Method according to claim 5 and further including the steps of applying pressure differentials to the carcass in order to obtain a suitable fit of the carcass within the tread package.

7. Method according to claim 5 or claim 6 wherein the two subpackages are incompletely vulcanised before commencement of the method.

8. Apparatus for performing the method of any one of claims 5 to 7 comprising a base (40), a support (10) mounted on the base and two package housings (50) arranged one either side of the support (10), the package housings (50) being movable towards the support (10).

9. Apparatus according to claim 8 further comprising means for imparting a pressure differential to a tyre carcass on the apparatus in use.

10. Apparatus according to claim 8 or claim 9 wherein the support (10) is detachable from the base (40).