GB2207644A - Apparatus for the manufacture of a pneumatic tyre - Google Patents

Abstract

A tyre building former (100) comprises at least three coaxial discs (101), (102), (106) for supporting a carcass ply (30), Fig 16, on their radially outer surfaces. The central disc (102) is axially movable between the two other discs so as to support a portion of an elastomeric ply (103) helically wound onto the former (100) from a strip (104). <IMAGE>

Description

APPARATUS FOR.

THE MANUFACTURE OF A PNEUMATIC TYRE This invention relates to apparatus for the manufacture of pneumatic tyres.

In the conventional manufacture of radial carcass pneumatic tyres a ply of parallel rubberised tyre cords is laid on a drum or former with the cords extending axially of the cylindrical former, over an inner liner, and the bead wire assemblies are placed in axially spaced positions coaxially around the ply, following which the ply is expanded into engagement with the bead wire assemblies and the axially outer portions of the ply are turned around the bead wire assemblies to provide ply "turn ups" which in the shaped and finished tyre may extend for a considerable distance radially outwardly from the bead wire assemblies.

One object of the present invention is to provide apparatus for the manufacture of a tyre in which the bead "turn up" can be substantially reduced.

The invention is particularly suitable for use in the manufacture of a tyre having a carcass ply produced hy a method and apparatus as described in GB 21591 85A.

According to the invention t-here is provided a substantially cylindrical tyre building former comprising at least three rotatable coaxial discs for supporting a tyre carcass on their outer surfaces, at least one disc being arranged to support part of a tyre inner liner formed as a winding thereon and to travel during the winding process from a position at one end of the former to a position at the other end of the former.

Embodiments of the invention will now be described, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of a carcass ply and support elements as utilised in the present invention also showing an enlarged detail Figure 2 is an alternative carcass ply and bead assemblies which may also be utilised in the present invention also showing an enlarged detail, Figures 3 to 11 are diagrammatic axial cross sectional views showing stages in the manufacture of a pneumatic tyre carcass and its incorporation into a tyre tread assembly; Figure 12 is a diagrammatic axial end view showing in more detail the stage illustrated in Figure 7, and & Figure 13 is an axial view at the same stage;; Figures 14 to 20 are similar views to those of Figures 1 to 9, showing an alternative process, and showing details of the former in cross-section only above the centreline of the former; Figures 21 to 23 show in more detail the former illustrated in Figures 14 to 20, and Figure 24 shows an alternative step using the carcass ply of Figure 2.

With reference to Figures 3 to 11, the sequence of steps in the manufacture of a pneumatic tyre is as follows: Figures 3 to 5 illustrate a method for the preparation of a rubber inner liner 27 for the tyre from a narrow strip 10 which may be fed from a stock roll, or preferably from a small calender, adjacent to a tyre building former 11 which comprises a series of coaxial, axially movable discs 15, 16, 17, 18 and 19. The discs 15 to 19 each have a cylindrical outer surface for supporting the tyre carcass or part of the tyre carcass at various stages of its manufacture. The former 11 has a diameter larger than the bead diameter of the tyre to be built thereon.

As shown in Figure 3 the inner liner 27 is in process of formation by winding the strip 10 as a continuous helical axially extending winding, initially on the rotating discs 15, 17 and 19, which are grouped together at one end of the former 11, and a pressing roller 25 is used to lay the strip on the discs and the winding processes by axial movement of the roller 25 from left to right to form a continuous butt - or scarf-jointed layer. Normally, two layers of the strip 10 are wound with the joints of the second layer staggered relative to the joints of the first layer.

Figure 4 shows the completion of the winding to form the inner liner 27. Since the winding is laid helically it will be necessary for the ends to be trimmed (this step is not shown) and the discs 15 and 16 are then removed axially leaving the liner 27 supported on discs 17, 19 and 18 as illustrated in Figure 4. It will be noted that the discs 17 and 18 remain axially stationary and that the disc 19 travels, during the winding process, from the position adjacent disc 17 shown in Figure 3 to the position shown adjacent the disc 18 in full lines in Figure 4 at the opposite end of the former. The disc 19 moves axially to remain.in alignment with the strip so as to support the strip as it is wound across the former.

This enables a hollow former to be employed, and thus to allow all the tyre building operations including shaping to be carried out on the same former. After the winding of the inner liner the disc 19 returns to the position shown in dotted lines nix Figure 4 in the central region of the former.

Figure 5 shows the end portions 28, 29 of the liner turned down (radially inwardly) against the end surfaces of the discs 17 and 18. The inner liner is now in a suitable condition to receive a carcass reinforcement ply 30 as illustrated in Figure 6.

The ply 30 is conveniently manufactured by apparatus similar to that disclosed in published patent application GB2159185A which comprises a pair of longitudinally extending rotatable spindles mounted in spaced apart parallel relationship one for each edge of the ply fabric, a cord winding head, and means for rotating the winding head around the pair of spindles so as to form a winding of cord which passes around both spindles and is progressively moved axially along the spindles by helical members coaxial with the spindles and rotating in opposite directions to the direction of spindle rotation to move the winding in synchronisation along both spindles.

The cord ply formed on the above apparatus comprises continuous cord reinforcement 31 having a series of loops 36 adjacent the edges of the ply. This is illustrated in Figure 1.

& BR< The preparation of the ply further comprises the step of applying thin sheets of unvulvanised rubber to the upper and lower surfaces of the cord winding as it emerges from the spindles thus producing a rubberised parallel-cord ply in which the edges having un-rubbered loops of cord protruding from the edges of the rubberised fabric.

Support elements, 32 and 33 preferably wire elements, but it is envisaged that other materials such as aromatic polyamides, nylons, or polyesters could be used, are located through the loops 3fi at each edge of the ply subsequently to form hooped support elements at each edge of the ply when it is formed into a cylindrical shape.

The support element may be located into the loops after the cord ply has been rubberised or alternatively may be located into the loops prior to cords being rubberised.

One method of incorporating the wires into the loops is to pass each support element wire through the centre of a respective spindle so that the loops of cord are held on the support elements as they are removed from the spindle.

The above method may produce a continuous length of reinforced elastomeric ply which is then necessary to cut to suitable ply lengths as required. If the support elements are already in place it will be necessary to sever both the reinforcement cord and the support wires.

The ply and support elements are formed in a cylindrical shape with hooped support elements at each end.

A ply 30 as shown in Figure 6 thus comprises a cylindrical layer of rubberized cord material 31 in which the cords lie in the axial direction and have loops 35 ,oassina around support wires 32, 33. After forming the support wires to circular form around the former their ends are welded (adjacent cord loops being parted to enable welding electrodes to be inserted without damaging the fabric) and the circled support wires are then crimped so as to enable the ends 34 and 35 of the ply to be turned radially down against the ends of the former as shown in Fig. 7.The formation of the support wire 32 in its crimped state is shown in more detail in Figure 12, which also shows the position of the weld 38 by which the ends of the wire 32 are secured together and which indicates a bead wire assembly 40 which is then brought into position adjacent the corresponding end of the former as shown in Figure 8.

A similar bead wire assembly 41 is placed at the opposite end of the former. The bead wire assembly preferably comprises a plurality of hooped turns of continuous wire bundled together into a suitable bead shape, for example, square, hexagonal, circular, etc. The bead assemblies 40 and 41 are formed with a turn of wire left out of the axially outer side of the bead bundle in the radially outer layer of wire so that there is a vacant position in the bead wire configuration in the outer layer of the bead assembly.

& BR< Apparatus for forming the support wires 32, 33 to the crimped condition shown in Figures 7, 8, 12 and 13 is not illustrated but may take the form of a series of coaxially extending fingers arranged initially around two pitch circles of different diameters and moved axially towards the former, respectively, radially within and radially outside the wire 32 or 33. The fingers are then contracted the outer fingers being drawn radially inwardly to a greater extent than the inner fingers so as to deform the support wire as shown in Figure 12. This effectively reduces the diameters of the support wires to enable the bead wire assemblies 40 and 41 to be fitted against the turned-down portions 34, 35 of the ply as seen in Figure 8.

The axially extending fingers are then withdrawn axially outwardly and released to permit the support wires 32, 33 to resume their natural circular configuration.

Where the support elements are aromatic polyamides etc., the ends of the hooped element may be tied together.

Figure 9 shows the condition of the partly-built tyre carcass following release of the support wires. A further operation, shown in Figure 10, is then employed to press the support wires into engagement in the suitable annular notshes 43, 44, or spaces, which have previously been formed in the bead wire assembly configuration, as previously described.

The completed ply, liner, and bead assemblies are consolidated as shown in Figure 10 and the ply is tensioned by moving the discs 17 and 18 slightly away from one another. Other tyre & BR< components such as apexes, chaffer strips, etc., may be added at this stage.

The next stage is a shaping operation as illustrated in Figure 11, in which the interior of the tyre is inflated by suitable conventional means and the discs 17 and 18 moved towards one another, thus shaping the tyre carcass to toroidal form. Conveniently the shaping operation is carried out within a tread carrier ring 50 in which a previously moulded tread and breaker assembly 51 is positioned around the carcass so that the breaker and tread are assembled accurately with the breaker and tread in symmetrical relationship to the circumferential centre line of the carcass. The tread carrier ring 50.may constitute a mould, and the sidewalls may be added in pre-moulded condition, carried on suitable sidewall moulding plates, to enable the final curing operation to be carried out as described in our U.K.

Application No. 2134439A.

Figures 14 to 20 show a second method also of manufacturing a pneumatic tyre in accordance with the invention, and which also illustrates a former in greater detail.

Figure 14 shows a winding process in which a liner is built by a progressive helical winding of a strip around a former as previously described with reference to Figures 1 to 9.

The building former assembly 100 comprises three rotatable discs 101, 102, and 106 and its operation is generally similar to that described above in relation to Figures 3 and 5 except that only three discs are used. The winding commencing on a pair of discs 101 and 102 of which the disc 102 is moved to the right, supporting the liner 103 as it is wound under a moving roller 104, and the winding terminates on a disc 106. The three coaxial discs IQ1, 102, 106 are mounted on a hollow shaft 130 and are axially moveable by internal rods 131 and 132. The rod 131 having oppositely handed screw threaded portions thereon for movement of the discs 101 and 106 towards or away from each other in a known manner.Figure 15 shows the disc 102 in its central position and the inner liner 103 being cut to length by disc cutters 135.

Figure 16 shows the addition of the carcass reinforcement ply 30 (omitted from the lower part of the drawing) in which the portions containing support wire elements 108, 109 project beyond the edge of the former assembly, and in this example the overall diameter of the former, liner 103, and ply 30 is arranged to be slightly less than the internal diameter of bead wire assemblies 115, 116 (see Figure 17) which are to be built into the tyre carcass. It will be noted that the support wires 108, 109 may be formed as a broken ring in which the ends of the wire length are not welded together but have a short overlap to enable the circled support wires to be expanded in diameter, before welding, to the final diameter required to fit in the required position against the bead wire assembly.

Figurel7 shows the bead wire assemblies 115 and 116 placed in position over the liner and ply on the former 100 and Figure 18 shows the expansion of discs 101 and 106 to grip the bead wire assemblies 115, 116, through the ply. The disc 101 and 106 include radially slidable segments 136 and 137, having inclined cam surfaces 138 on the radially inner end portions thereof which are engagable on a conical disc 140 slidably mounted on the shaft 130. The support wires 108, 109 are expanded to their required diameter i.e. with their ends abutting. The ends of the wires 108, 109 may be then welded together to form inextensible rings which as shown in Figure 19 are then pressed by a suitable device into engagement with corresponding notches 118, 119 formed, respectively, in the bead wire assemblies 115, 116 (as previously described).As before apex strips and chaffer strips may be added at this stage.

The ply is then tensioned by outward movement of the discs 101, 106. The carcass is then shaped into engagement with a tread and breaker package 125 carried in a tread moulding ring 126 as shown in Figure 20. Finally, premoulded sidewalls carried on suitable sidewall moulding plates are added and the whole assembly is cured as described in our U.K. Application No. 2134439A.

Figures 21, 22 and 23 show in more detail the sequence of operations to expand the disc 101 so as to bring the ply 30 and a double thickness liner 103 into engagement with a bead wire assembly 115. The former 100 incorporates a sleeve 120 of flexible plastics material extending from one end of the former to the other and supported on the radially expansible segments 136 and 137. The purpose of the sleeve 120, when the operation of Figures 14 and 15 is being carried out, is to support the liner 103 whilst permitting the travelling disc 102 which is maintained in alignment with the roller 104, to move within the sleeve 1?0 across the axial width of the former between the discs 101 and 106.The sleeve 120 is of low-friction material to enable the disc 102 to slide freely within it, and acts to counter any tendency which the axial movement of the disc 102 might otherwise have to pull the windings apart as it moves across.

Figure 22 shows the disc 101 and the segments 136, and 137 expanded to grip and position the bead assembly 115, the expansion of the segments 137 providing a shoulder for accurate location of the bead wire assembly.

In Figure 23 the shaping of the tyre carcass with apex strips 122 now added is illustrated, and in this operation the central portion of the sleeve 120 is deflected radially inwardly by the inflation pressure, which it serves to retain by sealing the inner parts of the former.

With reference to Figure 2 and Figure 24, in an alternative method the support elements may be formed as a single hoop of wire which is a portion of the continuous wire of the bead wire assemblies. Each bead 215 is formed of a plurality of turns of a wire, a portion of this wire may be located in the loops 36 at the respective edge of the ply 30 so that support members 232 and .233 for the loops are actually constituted by a single turn of the bead assembly 215. & BR< Thus, in Figure 24, the bead assemblies 215 are formed simultaneously as the ply 30 is wound onto the former 100.

The operation of the former 100 continues as before.

Claims (11)

1. A substantially cylindrical tire building former comprising at least three rotatable coaxial discs for supporting a tire carcass Rly at their radially outer surfaces, one disc being associated with each axial end portion of the former, and the other inner disc being arranged to move between the two end portions of the former so as to support a portion of an elastomeric ply to be helically wound thereon from a strip.

2. A tire building former as claimed in claim 1, wherein a sleeve of flexible material extends between the two discs associated with the end portions of the former and the inner disc is axially moveable within the sleeve.

3. A tire building former as claimed in Claim 2 wherein the sleeve of flexible material is formed from a low friction flexible plastics material.

4. A tire building former as claimed in any one of Claims 1 to 3 wherein the two discs associated with the end portions of the former are capable of simultaneous movement towards and away from each other, and each disc has radially expandable segments for pressing a carcass ply against a bead assembly located around the ply.

5. A tire building former as claimed in any one of Claims 1 to 4 wherein the three discs are mounted on a hollow shaft, and are axially moveable thereon by rods located within the shaft, the two axially outer discs being connected to oppositely handed screw threded portions of one rod for movement towards and away from each other, and the inner disc being connected to the second rod for movement between the two axially outer discs.

6. A tire building former as claimed in any one of Claims 1 to 5, wherein the discs associated with each end portions of the former each have two sets of radially expandable segments thereon, the axially inner set of segments providing a shoulder for location of a tire bead and the axially outer set of segments being expandable to press against the internal surface of said tire bead.

7. A tire building former as claimed in Claim 6 wherein the radially expandable segments each have radially inner end portions with an inclined cam surface thereon which is engageable with a conical disc slideably mounted on said shaft.

8. A tire building former as claimed in Claim 1 wherein the former comprises five coaxial axially moveable discs, there being two discs associated with each axial end portion of the former, the two axially outer disc being axially removeable to leave any ply on the former supported only on the three axially inner discs.

9. A tire building former as claimed Claim 4 when dependant on Claims 2 and 3 , wherein the sleeve serves to seal the inner parts of the former, when the axial and discs are moved together and a carcass ply on said sleeve is shaped into toroidal form by inflation pressure.

10. A tire building former substantially as described herein and with reference to Figures 14 to 23 of the accompanying drawings.

11. A methodof manufacture of a pneumatic tire in which a cylindrical ply for a tire is formed by continuous helical winding of strip elastomeric material around a former comprising at least three rotatable coaxial discs which support said ply at their radially outer surfaces, one disc being assoicated with each axial end portion of the former, and the other inner disc being arranged to move between the two axially outer discs, wherein said inner disc travels axially during the winding process from a position at one end of the former to a position at the other end of the former to remain in axial alignment with the portion of strip being wound onto the drum.