GB2182894A - Tyre building apparatus - Google Patents

Abstract

A ply turn up device (10) for a tyre building former and which comprises an array of arms (11) each having a pair of rollers (13) and (14) rotatably mounted on its free end. The array of rollers in the retracted position lie in substantially side-by-side abutting relationship. To make a turn-up the rollers are moved radially outwards by rotation of the arms (11) about their pivots (40), causing the rollers to sweep substantially the whole of the ply area which is turned up. In order to accommodate the large number of arms (11) each pivot (40) is formed on a pivot block 26 and each pivot block is generally wedge shaped for packing between neighbouring pivot blocks. <IMAGE>

Description

SPECIFICATION Tyre building apparatus This invention relates to tyre building apparatus, and particularly to a ply tu rn-up device for a tyre building former.

When a pneumatic tyre is constructed by wrapping plies of rubberised cord fabric around a building former, there is a requirement, after the bead wires have been placed in position, for ends of the ply extending axially beyond the bead wires to be turned overthebeadwires. In hand-building this operation is normally performed manually, and considerable difficulty has been encountered in the design of suitable apparatus to perform the operation by automatic apparatus.The ply turn-up operation may be effected by means of rollers (spinners) moved radially with respecttothetyrecarcasswhilethe carcass is rotated, but in certain tyre building apparatusforexample as described in our UK Application Publication No. 2129380A it is desirable fortheturn-up operation to take place while the carcass is held stationary.As described in Publication No.21 29380Athe carcass is formed and placed within a "bead tube" which carries the bead wires at its ends and the ply turn-ups are then turned radially outwardly around the bead wires, and in viewofthe relatively large bulkofapparatus engaged in maintaining the accurate shape ofthe carcass during this operation it would be difficultto rotate the carcass on its former.

Some means therefore had to be developed for smoothly and uniformlyturning-upthe ply ends around bead wires with the carcass held stationary.

The use of air-infiatable plyturn-up bags for this purpose is known, but these devices are relatively troublesome and energy-consuming in operation.

In accordance with the present invention, a ply turn-up device for a tyre building former comprises an array of roller-carrying arms, each arm being pivotally mounted at one end on a support and carrying a roller at its free end forengagementwith an edge portion oftyre building material carried on the former, whereby the array may be retracted to bring the rollers inwardlytowardsthe axis of an associated tyre building former and the array may be expanded by rotation of the arms around their pivots to movetheirfree ends and the rollers carried thereon outwardly in the radial sense relative to the axis of the former, wherein the number of arms is sufficiently large and the individual rollers are sufficiently narrow to enable the array to provide a substantially continuous roller area directed towards the tyre building former, at least in the retracted state of the array.

The invention also provides tyre building apparatus incorporating a tyre building former, a bead tube arranged to surround the tyre building former so asto support a pair of bead wire assemblies in accurately axially spaced relationship at opposite ends of the former, and a pair of ply turn-up devices as defined in the preceding paragraph positioned one at each end oftheformer.

In a preferred example, an array of rollers having a minimum radius (measured radiallyoftheformer axis, to the outer edge of the rollers of 145 millimetres, and designed to expand to a corresponding radius of 245 millimetres) is made up of pairs of rollers each 30 millimetres in diameterand 3 millimetres thickness carried freely rotatably at the ends of sixty-four arms which extend substantially parallel to the axis oftheformerin the unexpanded state and at an angle of approximately 450 to the axis in the expanded state.By providing this very large number of rollers (and associated arms) the rollers can be designed to lie in substantially side-by-side abutting relationship in the unexpanded state ofthe turn-up device and thus as they move radially outwards to turn the ply edge around the bead wire they sweep initially over substantially the whole of the ply area which is to be turned. Inevitably, the rollers spread apartfrom one another in the later stages of the turn-up operation, but it has been found that by this time the ply edges have been constrained to lie smoothly against the bead wire assemblies and no difficulties have arisen in the application ofthe outer parts ofthe plyturn-ups to the bead wire assembly. In fact, the gaps between the rollers in the expanded state can assist in providing channels for the expulsion oftrapped air.

In orderto overcome the problem of providing supportforthevery large number of arms within the confines ofthe plyturn-up apparatus an arrangement of individual pivot blocks, one for each arm has been employed. The pivot blocks are each constructed with a recess and a central peg on which the end ofthe arm is located, and the series of blocks is arranged to be mounted in an assembly contained in a channel formed between flanges of a mounting ri ng for the a rray, the a rrangement being such that each pivot block and its associated arm is held in position by being packed tightly against neighbouring pivot blocks and arms in the completed assembly.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is an end view of part of a plyturn-up device showing areas of rollers in the expanded and retracted states respectively; Figure2 is an axial cross section on the line ll-ll of Figure 1 showing the plyturn-up device in association with a tyre building former (the rollers however being shown in the retracted state); Figure 3 is a similarviewto that of Figure 2 but taken on a different section line, showing the ply turn-up device in its expanded state, and Figure 4 is a detail perspective view of a pivot block.

A plyturn-up device 10 as illustrated in Figure 1 comprises an array 11 of roller-carrying arms 12 each of which has a pair of rollers 13, 4freely rotatably mounted on its free end. The upper part of Figure 1 shows one quadrant of the array in its fully expanded state whilst the lower part of Figure 1 shows a portion of the array in its fully retracted state.

As shown in Figure 2, the plyturn-up device 10 comprises an array of arms 12 disposed around the axis of an expansibletyrebuildingformer20 supported on a shaft 21. The plyturn-up device is located at one end oftheformer 20, which is provided with a segmented shoulder ring 24 in which the rollers 13, rest in theirretractedstate.

The arms 12 are mounted in pivot blocks 26 carried in a support ring 27 which carries a retaining ring 28 providing a mounting flange 29for one end of a rubber sleeve 30 secured to the former 20 at its other end by a bead 31 between the shoulder ring 24 and the former 20. The flange 29 also supports a series of compression springs 33 each mounted on a pin 34 secured to the flange 29 and entering a recess 35 formed in a thrust ring 36 which is arranged to be axially slideable to apply pressure (dependent on the stiffness ofthe springs 33) to an abutment 37 formed on each arm 12 so as to tend to rotate the arm towards the retracted position as shown in Figure 2, the arm pivoting about a peg 40 formed in the pivot block 26.

The support ring 27 is slideable on the axle 21 underthecontrol of a screw 44 engaging a nut 45 secured to the ring 27, the arrangement being such that rotation ofthe screw 44 drives the ring 27 towards the former 20 when the ply tu rn-up device is required to operate, and the principle of operation is illustrated in Figure3which shows the position of the arms 12 in the fully expanded state.

Figure3illustratesa beadwireassemblySO comprising a wire 51 and a rubberapex52as held in position adjacenttheformer20 by a bead tube indicated generally at 53. The associated tyre carcass plies and inner liner are indicated at 55,56, 57 respectively, and the associated ply turn-up ends are indicated generally at 58.

The bead tube 53 comprises at each end a segmented nylon ring 60 the segments of which are secured by screws 61 to flanged tubular metal segments 62 which are movable radially buy a suitable mechanism. As shown in Figure 3the segments forming the bead tube 53 are drawn radiallytogetherto provide a continuous tube surrounding the building former 20 (on which the plies 55, 56 and innerliner57 have been assembled) and in order to ensure accurate registrytogetherof the segments locking rings 61 are fitted by axial movement overthe contracted segments as shown in Figure 3.

The bead tube 53 is arranged to be positioned around the former 20 and to be secured in a fixed axial position with the bead wire assemblies 50 suitably located (e.g. by magnetic holders) against the end faces of the bead tube. The former 20, to which the shoulder ring 24 is attached, is then expanded by conventional means to cause the plies 55, 56and inner liner 57 to be pressed uniformly against the smooth interior of the bead tube and also to cause the bead wire assemblies 50 to be gripped and held in axially spaced positions determined by the length ofthe bead tube. The ply turn-up device is then operated to turn the ply ends outwardly as shown in Figure 3, consolidating the turn-ups against 'anvils' provided by the end faces of the bead tube.

Since a very large number of rollers is provided, the contact of the rollers in the first stage ofthe operation, through the sleeve 30, with the ply turn-ups, is for all practical purposes uniform and continuous around the whole circumference of the former. Thus as the pivot blocks 26 are moved towards the former the ply tu rn-ups are smoothly and uniformly applied to the bead wire assemblies 50 at each end ofthe former without the necessity for any rotation oftheformer. Once the radially inner portions of the turn-ups are firmly applied,the radially outer portions follow smooth ly to provide a uniform and well-consolidatedjoint.The array 11 of armsisthen retracted by movementofthesupport ring in the axially outward direction underthe control of the-lead screw 44 until the state illustrated in Figure 2 is regained.

An important constructional feature of the ply turn-up device is illustrated in Figure 4 which shows the generally wedge shape ofthe pivot block 26 which is manufactured from nylon and comprises an integral peg 40 forming the pivot as described above, for engagement into a hole 70 in the associated arm 12 and surrounded by a recess 71. The pivot blocks are arranged to be tightly packed together with their associated arms 12 in an annular channel 73 formed between flanges 74 and 75 ofthe support ring, thus enabling the array to be mounted within an extremely restricted annular space. The retaining ring 28 has a slotted forward end 78 which serves to retain the blocks 26 in the channel 73 against radially outward movement.The thrust ring 36 is also slotted at its forward end 79, the arms 12 being retained (in the circumferential sense) in the slotted ring 36 so that they can only move in a true radial path.

Theplyturn-up device described above isof particularvalue in that it provides a robust and accurate meansforensuring a uniform and well-consolidated ply turn-up against a radially aligned bead and apex assembly as disclosed in our co-pending UK application, publication No.

2129380A. The method of consolidation against a radially-aligned bead and apex assembly avoids the inaccuracies which arise in more conventional methods oftyre building where plyturn-up and consolidation are carried out with the apices and turn-ups aligned with a cylindrical carcass and subsequently shaped to a radial alignmentinevitably causing displacement of cords and other components.

Claims (10)

1. Aplyturn-up deviceforatyre building former comprising an array of roller-carrying arms, each arm being pivotally mounted at one end on a support and carrying a roller at its free end for engagement with an edge portion oftyre building material carried on theformer, whereby the array may be retracted to bring the rollers inwardly towards the axis of an associated tyre building former and the array may be expanded by rotation of the arms about their pivots to move their free ends and the rollers carried thereon outwardly in the radial sense relative to the axis of the former, wherein the number of arms is sufficiently large and the individual rollers are sufficiently narrow to enable the array to provide a su bsta ntially contin uous rol ler area directed towards the tyre building former, at least in the retracted state ofthe array.

2. Aplyturn-updevice according to Claim 1 whereinthe arms each carrytwo rollersfreely rotatably mounted one on each side ofthe arm.

3. A plyturn-up device according to Claim 1 or Claim 2 wherein a pivot block is provided for each arm, the pivot blocks being arranged to be located in side-by-side engagement in an annular channel of a support ring.

4. A ply turn-up device according to Claim 3 wherein each pivot block is formed with a recess containing a peg on which the associated arm is pivotally mounted, the arrangement being such that when the blocks are assembled side-by-sidethe blocks serve to retain the levers on the pegs of adjacent blocks.

5. A ply turn-up device according to Claim 3 or Claim 4wherein the blocks are generally wedge-shaped to facilitate assembly in annular form.

6. A plyturn-up device according to any of the preceding claims wherein the arms are pivotally mounted on a support which is movable axially with respect to a tyre building former, the arms being spring-loaded towards a retracted position.

7. A plyturn-up device according to Claim 6 wherein the arms each have an abutment engageable by a spring-loaded thrust ring mounted on the support.

8. Tyre building apparatus comprising a tyre building former, a bead tube arranged to be positioned coaxially with the formerto support a pair of bead wire assemblies in axially spaced relationship determined by the length ofthe bead tube and providing end faces to support the bead elements in an operation to turn carcass material radially outwardly around the bead wire assemblies, and a plyturn-up device for each end of the former as claimed in Claim 1.

9. A ply turn-up device substantially as described in the Description and illustrated in the accompanying drawings.

10. Tyre building apparatus substantially as described in the Description and illustrated in the accompanying drawings.