GB2223988A

GB2223988A - Manufacture of pneumatic tyres

Info

Publication number: GB2223988A
Application number: GB8824372A
Authority: GB
Inventors: Anthony Gerald Goodfellow
Original assignee: Apsley Metals Ltd
Current assignee: Apsley Metals Ltd
Priority date: 1988-10-18
Filing date: 1988-10-18
Publication date: 1990-04-25
Anticipated expiration: 2008-10-18
Also published as: GB8824372D0; GB2223988B

Abstract

Means for shaping a tyre breaker from a flat profile to an arcuate profile as in a green tyre includes an elastomeric former 11 having an outer cylindrical portion 12, an inwardly projecting stem 13 and a detent means 14, (15, Fig. 1) for holding the former 11 in a constricted condition with its outer surface 16 flat, the outer surface assuming an arcuate profile when the former is in a relaxed condition. The former 11 is supported on a housing 21 having locking rings 22, 23 to hold it in the constricted condition and is constricted by use of a constrictor ring (51, Fig. 3) acting around its outer portion 12. The breaker is formed onto the constricted flat former 11 which is subsequently relaxed to assume an arcuate profile to shape the breaker. The former 11 is made by casting polyurethane resin then machining the outer annular surface to the required convex profile with the former in its relaxed condition. <IMAGE>

Description

Apparatus and Method for Manufacturing a Tire This invention relates to apparatus and a method of manufacture of a pneumatic tire, and in particular a radial carcass pneumatic tire.

In the manufacture of radial tires it is usual for a breaker assembly to be built separately from the carcass of the tire.

The annular breaker assembly is then transfered to a positon in which it is made concentric with a cylindrical tire carcass which is then shaped-up into a toroidal configuration within the breaker to assemble the carcass to the breaker.

In an alternative method, the cylindrical tire carcass may be shaped-up and the breaker assembly formed directly onto the toroidal carcass by winding a breaker belt onto the outer surface of the carcass.

The breaker belts used in the above assembly techniques are flat in cross-section and as a consequence the assembled green tire includes a breaker assembly which is substantially flat in cross-section and when the green tire is placed in the vulcanisation mould for final shaping and curing the flat breaker is distorted into an arcuate shape. This final transformation from a flat breaker assembly to an arcuate convex breaker assembly is difficult to control and may be a source of inconsistencies in the finished product.

The applicant has devised a method and apparatus for use in tire manufacture which will ameliorate the above problems.

Accordingly there is provided a method for the manufacture of a tire utilising a breaker assembly former having a radial outer annular surface for receiving a breaker assembly, said outer surface having in a first condition a substantially flat profile in radial cross-section, and in a second condition having a convex arcuate profile, said method comprising:1. causing the former to take up said first condition with the outer surface being substantially flat in radial cross-section; 2. forming a breaker assembly onto said flat annular surface; and 3. subsequently causing the former to take up said second condition so that the former and breaker assembly assume a convex arcuate shape in radial cross-section, said convex arcuate shape being such that the breaker assembly assumes the curved shape that would be taken by the breaker assembly in an assembled tire.

There is also provided apparatus for manufacturing a pneumtic tire and which includes a breaker shaping means for shaping a breaker from a substantially flat profile in radial cross-section to an arcuate profile in radial cross-section and which is substantially the same as the profile which the breaker would assume in a green tire, said shaping means including an elastomeric former having a radially outer cylindrical portion with an outer annular surface thereon, a radially inwardly projecting annular stem located at the axial mid length of the cylindrical portion and extending inwards therefrom, said stem having at its inner end portion a detent for holding the former in a stressed contracted condition in which the annular outer surface is flat in radial cross-section, said outer surface assuming a convex arcuate shape in radial cross-section when the former is in a relaxed expanded condition.

Conveniently the former may be caused to assume its flat condition by a constrictor ring which comprises a plurality of clamping shoes which are mounted in a circular array in a support ring, said shoes all being simultaneously radially moveable relative to the support ring.

Preferably the support ring comprises a pair of spaced apart side plates with an annular cam plate located for movement therebetween, so that relative rotational movement of the cam plate to the side plates simultaneously operates all the clamping shoes for radial movement.

Also the former may be held in its flat state, after removal of the constrictor ring by a retention means acting against the detent on the former, the retention means comprising a pair of coaxial lock rings engagable on opposite sides of the former which are capable of axial movement towards and away from each other, said lock rings each having an outer annular cylindrical flange which provides a support radially inwardly of a respective axial end of the cylindrical portion of the former, and a latching surface which is engagable with the detent on the stem of the former to hold the former in its contracted state.

The invention will be described by way of example and with reference to the accompanying drawings in which: FIG 1 is a section through a breaker assembly former as claimed in the present invention, FIG 2 is a section through a retention means for holding the former of FIG 1 in a flat condition, FIG 3 is a constrictor means for tranforming the former of FIG 1 from an expanded arcuate condition to a contracted flat condition, FIGS 4 and 5 are sections on the lines IV-IV and V-V in FIG 3, and FIG 6 is a schematic diagram showing the manufacture of a tire according to the present invention.

With reference to FIG 1, there is illustrated a radial cross-section through a breaker shaping means, or former 11.

By radial cross-section is meant a radial section taken on a plane including the axis of rotation of the former. The former 11 is made of a polyurethane rubber (Bunaprene T.M.) having a hardness of 90 degrees shore A, and comprises a one piece polyurethane casting having a radially outer cylindrical portion 12, a radially inwardly projecting annular stem 13 located on the axial centerline CL of the former, and detent 14 located at the radially inner end portion of the stem 13. The detent 14 has a radially outwardly projecting tapered surface 19 for engagement with a retention means (to be described later). The detent includes an annular array of metal inserts 15 circumferentially spaced around the detent to provide a suitable rigid surface for locking the former in a contracted state (to be discussed later).

The former 11 is a substantially solid elastomeric mass which is shown in FIG. 1 on the left side of the centerline CL in a contracted stressed condition in which the outer annular surface 16 is substantially flat in radial cross-section, and which on the right side of the centerline is shown in the expanded relaxed condition in which the outer annular surface has a convex arcuate shape in radial cross-section which is the same shape which the breaker assembly will assume in a green tire and a moulded tire.

As can be seen in FIG 1, the terms expanded and contracted refer to the dimensions of the former at the centerline CL, since when the centerline dimension is reduced during the flattening process, the axially outer portions 12A and 12B of the cylindrical portion 12 actually move radially outwardly.

The radially inwards displacement D1 of the axially mid portion of the arcuate surface 16 may be between 1/2 and 1% of the nominal radius of the outer surface 16 when flat.

Preferably the displacement is about 0.75% of the said nominal radius. The radial outwards displacement D2 of the axially outer portions 16A and 16B may be slightly greater and is between 1% and 2% of said nominal radius.

The axially outer margins 16A and 16B of the outer annular surface 16 may be shaped to accept shoulder wedge inserts.

The polyurethane former is manufactured by liquid casting a suitable polyurethane resin in a mould of approximately the desired shape of the finished former. Any metal inserts 15 are cast integrally into the former at this stage.

After curing, the former is machined to the required convex arcuate outer surface 16 with the former held in a substantially relaxed expanded condition. After this machining the former is placed into its constricted condition and the outer surface 16 measured for flatness. If the surface is not flat more machining may be required to remove material from the radially inner surface of the outer portion 12 until the desired result is obtained.

With reference now to FIG. 2, the polyurethane former 11 is a relatively flexible former and to retain its circular shape during the constriction of the ring into its flat condition, and also to support the cylindrical portion 12 during breaker assembly, the former 11 is mounted in a support housing 21 which can be mounted on any standard breaker building machine. In FIG. 2 the support housing 21 is shown in diametral cross-section with the righthand portion below the axis of rotation R-R showing the breaker former 11 in the expanded condition and the remainder of FIG. 2 showing the breaker former in the contracted condition.

The support housing 21 comprises a pair of coaxial locking rings 22 and 23 which are engagable on opposite axial sides of the former 11. The locking rings 22 and 23 are each mounted on a respective cylindrical sleeve 24 and 25 with the sleeve 25 having a telescopic connection within the sleeve 24. Each locking ring 22 or 23 has an outer cylindrical flange 26 which supports the respective axially outer portion of the cylindrical portion 12 of the former 11, and an axially inner end portion 27 that engages and supports a respective axial side face of the stem 13 of the former 11.The axially inner end portions 27 also have a radially inwardly projecting tapered surface 28 which is engagable with the like tapered face 19 of the detent 14 on the former 11. The radially innermost portion of the locking ring is engagable with the axial sides of the detent 14.

The cylindrical sleeves 24 and 25 has a latching mechanism in the form of an annular slot 29 in the sleeve 25, and an annular array of six equiangularly spaced locking segments 31 on the sleeve 24 and which are engagable in the slot 29 to lock the sleeves 24 and 25 together and hence the locking rings 22 and 23 axially together. The locking segments 31 are each operated by the tapered head 32 of a lock actuator 33, and the six lock actuators 33 are mounted on a lock actuator ring 34 for simultaneous operation.

The former 11 is originally in its relaxed expanded condition with the outer surface 16 assuming a convex arcuate profile.

In order to make the outer surface 16 assume a flat condition it is necessary to constrict the axially mid portion 16c of the former. The means of constriction of the former will be described later.

The locking rings 22 and 23 are axially spaced apart with their axially inner end portions 27 clear of the axial sides of the detent 14. The constrictor means then acts on the center portion 16c of the outer surface 16 to push the stem 13 and detent 14 radially inwardly. The two locking rings 22 and 23 are then moved axially together so that the tapered surface 28 on each locking ring fully engages with the tapered surface 19 on the detent 14, to hold the former 11 in the contracted condition. Since there are considerable inherent stresses within the former 11 attempting to return the former to its expanded relaxed state, the locking rings 22 and 23 must be secured together by engagement of the locking segments 31 with the slot 29. The constrictor means may then be removed.

One of the locking rings 23 has an annular array of six circumferentially spaced ring grips 36 thereon which are each radially moveable and are spring biased radially outwardly.

These grips 36 serve to retain the polyurethane former 11 on the support housing 21 when the former 11 is in a relaxed expanded condition.

The means for constriction of the former 11 from its arcuate condition to its flat condition is shown in FIG 3. and is a constrictor ring 51 comprising a plurality of clamping shoes 52, preferably sixteen shoes, which are mounted in a circular array in the annular support member 53 for radial movement relative thereto. The shoes 52 are shown in their radially innermost extended position for constriction of the former 11, above the horizontal centerline, and in their retracted position below the centerline. The shoes 52 are each mounted for radial movement on radially directed guide pins 54 secured to the respective shoes 52 and slideably mounted on the annular support member 53.The annular support member 53 comprises a pair of spaced coaxial annular side plates 55 which are hold in spaced relationship to each other by a plurality of, preferably four, bridges 56, equiangularly spaced around the side plates 55. This is best seen in FIG 5. The support member is supported on a pair of brackets 57.

The clamping shoes 52 are operated by a cam plate 58 located between the two side plates 55, and which is mounted on rollers 59 fitted to the bridges 56 for rotational movement relative to the side plates 55. The cam plate 58 is rotated as required, by a pair of actuators 59, mounted one on each bracket 57 and each having a respective actuator rod 60 connected via a pivot 61 to the cam plate. The extension of the two actuators 59 causes the cam plate 58 to rotate clockwise causing the polyurethene former to contract. The two actuators are caused to contract to allow the cam plate 58 to rotate anticlockwise and allow the constrictor unit to re-expand.

The cam plate 58 has a series of cam tracks 62 and bearing tracks 63 thereon, one for each respective shoe 52. Each cam track 62 is an arcuate spiral slot on one axial side of the cam plate that engages a cam follower 64, in the form of a stud, attached to a respective shoe 52 so that rotational movement of the cam plate 58 causes the cam follower 64 to move relatively along the slot 62 and hence radially.

Each bearing track 63 is parallel with a respective cam track 62 and acts in conjunction with a roller bearing 65 on each shoe 52 which is moveable along the bearing track 63 so that rotation of the cam plate 58 in one direction acts through the roller bearings 65 to provide the high radial forces necessary to constrict the former, and the reverse rotation of the cam plate 58 causes the cam followers 64 to move along the respective cam tracks 62 and draw the shoes 52 outwards.

The extension of the actuator 59 will rotate the cam plate 58 clockwise moving all the cam followers 64 simultaneously radially inwardly so that the shoes 52 move in to constrict a former 11 which may be located concentrically within the constrictor ring, and operation of the actuator 61 causes the cam plate 58 to rotate anticlockwise to move all the cam followers simultaneously radially outwards to release all the shoes 52 from the former.

The present apparatus is for the manufacture of tires preferably utilising a method in which the uncured tread is formed in a patterned tread mould prior to the addition of the tread to the breaker assembly and tire carcass. Such a method is described in our patent application GB 2133357-A.

With reference to Fig 6 ,in the present method the former 11 is first placed onto a support housing 21 including the locking rings 22 and 23. The center portion of the former is then constricted preferably utilising the apparatus of FIGs.

3 to 5 so that the outer annular surface 16 of the former 11 is flat. The locking rings 22 and 23 are then moved axially together and locked together so that the former is restrained in its flat condition, and the constrictor ring is expanded and removed. The combined unit 81 of the former 11 and the support housing 21 is then taken by a typical transfer means 82 of the type well known in the art, through a series of tire building stations. If a pair of shoulder wedges are required to be located one in each axial edge portion 16A, 16B of the former ,the unit 81 is moved to a shoulder wedge strip laying machine 83 to lay two shoulder wedge strips 84 onto the former 11. The unit 81 is then transferred toa breaker building machine 85 which will lay the number 1 and number 2 breakers onto the former 11, over the shoulder strips (if required).

At this point there are alternative methods. In the first method the former 11 is released to allow it to expand on the support housing 21 to allow the breaker assembly to take up the same shape as it would have in the green or cured tire.

If desired , the shaped breaker assembly could be utilised in a conventional tire building process.

The former could be released within a concentric tread held in a mould so that the expansion of the former transfers the breaker assembly to the tread. The former 11 is then removed from the tread/breaker assembly by dismounting the former 11 from the locking rings 22 and 23 and allowing the former 11 to distort so that it can be removed In a second method, the unit 81 is transfered to a tread winding machine 86 and a tread package wound onto the constricted former 11.

The unit 81 with breaker and tread thereon is transfered to become concentric with a tread mould of the type described in GB 2134439 or GB 2133357 and the tread/breaker assembly transfered directly into the mould with release of the former 11 which will expand outwardly to its natural shape pushing the breaker/tread assembly into the tread mould.

Yet another alternative would be for the breaker/tread package to be transfered to a transfer unit by release of the former 11 to make the transfer. The breaker/tread package can then be utilised in a conventional tire building process by shape-up of a conventional carcass assembly within the breaker/tread package.

Release of the former 11 from the breaker/tread package is as already described.

Claims

1. A method of manufacture of a tire which utilises a breaker assembly former having a radial outer annular surface for receiving a breaker assembly, said outer surface having in a first condition a substantially flat in radial cross-section, and in a second condition having a convex arcuate radial cross-section, said method comprising 1 ] causing the former to take up said first condition with the outer surface being substantially flat in radial cross-section; 2] forming a breaker assembly onto said flat annular suface; and 3] subsequently causing the former to take-up said second condition so that the former and breaker assembly assume a convex arcuate shape in radial cross-section, said convey arcuate shape being such that the breaker assembly assumes the cured shape that would be taken by the breaker in an assembled tire.

2. A method as claimed in Claim 1 which utilises an elastomeric breaker assembly former with a radially outer annular surface for receiving the breaker assembly, the outer annular surface being in said first condition with a flat surface when the former is in a contracted stressed state, and being in said second condition with a convex arcuate surface when the former is in an expanded relaxed state, said method further comprising; a) constricting the axially center portion of the elastomeric former to cause it to contract to take up said first condition and b ] utilising a locking means to hold the axially center portion of the former in the stressed contracted condition.

3. A method as claimed in Claim 1 or Claim 2, wherein after forming a breaker assembly on the flat surface of the former, and prior to causing the former to take up said second conditions, a tread is formed onto the breaker assembly.

4. A method as claimed in Claim 2, or Claim 3 when dependant on Claim 2, in which the axially outer margins of the elastomeric former are shaped to accommodate shoulder wedges, wherein said method further comprise, forming shoulder wedge onto the axially outer margins of the former prior to forming the breaker assembly onto the contracted former.

5. A method as claimed in Claim 1 or 2 wherein the breaker assembly is transfered to an annular tread located in a tread mould, by making the former concentric with the tread mould and then allowing the former to expand to its relaxed condition within the tread to effect said transfer.

6. A method as claiemd in Claim 3 wherein the former with the breaker/tread insitu is made concentric with a tire mould, and the former allowed to expand to its relaxed condition in effect transfer of the breaker/tread package to said mould.

7. A method as claimed in Claim 3, wherein the former with the breaker/tread insitu is made concentric with an annular transfer unit, and the former, is allowed to expand to its relaxed condition to effect transfer of the breaker/tread package to the transfer unit, and the breaker/tread is then transfered to a tire building former for assembly to a tire carcass.

8. A method of manufacture of an elastomeric former for use in the manufacture of a tire said former having a radially outer surface for receiving a breaker assembly, said outer surface in a first condition being flat in radial cross-section, and in a second condition having a convex arcuate shape in radial cross-section, said method including; casting a liquid polyurethene resin into a mould of substantially the required shape for the former, and allowing the resin to cure; then removing the polyurethene former from the mould and machining the outer annular surface of the former to said convex arcuate profile with the former in said second condition.

9. Apparatus for manufacturing a pneumatic tire and which includes a breaker shaping means for shaping a breaker from a substantially flat profile in radial cross-section to an arcurate profile in radial cross-section and which is substantially the same as the profile which the breaker would assume in a green tire, said shaping means including an elastomeric former having a radially outer cylindrical portion with an outer annular surface thereon, a radially inwardly projecting annular stem located at the axial mid length of the cylindrical portion and extending inwards therefrom, said stem having at it inner end portion a detent for holding the former in a stressed constricted condition in which the annular outer surface is flat in radial cross-section, said outer surface assuming a convex arcuate shape in radial cross-section when the former is in a relaxed expanded condition.

10. Apparatus as claimed in Claim 9 in which the axially outer margins of the outer annular surface are shaped to each receive a shoulder wedge.

11. Apparatus as claimed in Claim 9 or 10 wherein said detent includes at least one annular metal insert integrally moulded into the inner end portion of the stem.

12. Apparatus as claimed in any one of Claims 9 to 11 in which the radially inward displacement of the axial mid-portion of the outer arcuate surface, and the simultaneous radially outward displacement of the axially outer end portions of said outer surface on going from an arcuate state to a flat state is in the order of 1% to 2.5% of nominal radius of said surface when flat.

13. Apparatus as claimed in any one of Claims 9 to 12 and further including a constructor ring which is placeable around the former to act on the outer annular surface thereof to flatten said surface.

14. Apparatus as claimed in Claim 13 wherein said constrictor ring comprises plurality of clamping shoes which are mounted in a circular array in a support reing, said shoes being sumultaneously radially moveable relative to the support ring.

15. Apparatus as claimed in Claim 14 wherein the support ring comprise a pair of spaced apart side plates with an annular cam plate located for movement therebetween, so that relative rotational movement of the cam plate to the side plates simulteneously operates all the clamping shoes for radial movement.

16. Apparatus as claimed in any one of Claims 9 to 15 and further comprising a former support housing having a retention means for acting against the detent on the former to holding the former in a constricted flat condition.

17. Apparatus as claimed in Claim 16 wherein the retention means comprises a pair of coaxial locking rings engageable on opposite sides of the former and which are capable of axial movement towards and away from each other, said locking rings each having an outer annular cylindrical flange which provides a support radially inwardly of a respective axial end portion of said cylindrical portion of the former, and a latching surface which is engageable with the detent on the stem of the former to hold the former in its constricted condition.

18. Apparatus as claimed in Claim 17 wherein the two locking rings are slideably mounted relative to each other for said movement, and there is a locking means for securing the two against axial movement when said rings are in engagement with the detent on the former.

19. Apparatus for the manufacture of a tire and which is for shaping a breaker assembly to a profile which is substantially that which it would assume in the green tire and /or cured tire , and which is substantially as described herein and with reference to the accompanying drawings.