GB2179307A - Method and apparatus for pneumatic tyre manufacture - Google Patents

Abstract

A method of manufacture of a tyre in which a carcass ply is formed by winding a continuous cord around a pair of spaced members to form a ply (31) having loops (36) at its edges. The cord ply is rubberised and support elements (32) (33) are located in the loops (36) to form a cylindrical ply having spaced hooped support elements at each ply edge. Bead wire assemblies (40) and (41) are located coaxially of the ply together with the support elements which are subsequently incorporated in the bead wire assemblies. A tyre building former is disclosed on which the above method can be performed. The former (100) comprises at least three coaxial discs (101), (102), (106) for supporting a carcass ply 30 on their radially outer surfaces. The central disc (10) 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

SPECIFICATION A method and apparatus for the manufacture of a pneumatic tyre This invention relates to methods and 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 orformerwith the cords extending axially ofthe cylindrical former, overran inner liner, and the bead wire assemblies are placed in axially spaced positions coaxially around the ply, foilowing which the ply is expanded into engagement with the bead wire assemblies and the axially outer portions ofthe 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 isto provide a method of manufacture of a tyre and apparatus therefore in which the bead "turn up" can be substantially reduced.

The invention is particularlysuitablefor use in the manufacture of a tyre having a carcass ply produced by a method and apparatus as described in GB 2159185A.

According to the invention there is provided a method of manufacture of a pneumatictyre including winding a cord reinforcement around a pair of spaced members to form a ply of continuous reinforcement cord having a series of loops adjacent the edges ofthe ply, rubberising the cords to form a reinforced elastomeric ply, locating at least one support element in the loops at each edge ofthe plyto form hooped support elements at each ply edge and shaping the ply into a cylindrical form, locating a bead wire assembly coaxially of the cylindrical ply together with the support elements and incorporating the support elements in each respective bead wire assembly to anchorthe loops of cord to each respective bead assembly.

The support elements may be wires which are formed into rings the ends of which may or may not bejoined together. The supportelements may be formed as an integral portion ofthe bead wire which is passed through the loops on each side ofthe ply and is then hooped and forms part of the bead assemblywhich comprises bundled wire hoops.

Alternatively when built into a tyre the support elements may be circled and welded and fitted against the bead wire assemblies so asto anchorthe loops of cord securely. Each bead wire assembly may be preformed with a notch suitably positioned to receivethe associated supportwire.

The invention further provides a tyre building former comprising a series of rotatable discs for supporting a tyre carcass on their outer surfaces, at least one disc being arranged to support part of a tyre inner linerformed as a winding thereon and to travel during the winding process from a position at one end ofthe former to a position at the other end oftheformer.

Embodiments ofthe invention will now be described, with reference to the accompanying draw- ings, in which Figure lisa diagrammatic view of a carcass ply and support elements as utilised in the present invention also showing an enlarged detail, Figure2 is an alternative carcass ply and bead assemblies which may also be utilised in the present invention also showing an enlarged detail, Figures3to 11 are diagrammatic axial cross sectional views showing stages in the manufacture of a pneumatic tyre carcass and its incorporation into a tyretread assembly;; Figure 1Z is a diagrammatic axial end viewshowing in more detail the stage illustrated in Figure 7, and Figure 13 is an axial view at the same stage; Figures 14to20 are similarviews to those of Fi gures 1 to 9, showing an alternative process, and showing details of the former in cross-section only above the centreline of the former; Figures 2 1 to 23 show in more detail theformer illustrated in Figures 14to 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 pneumatictyre is as follows: Figures 3 to 5 illustrate a method for the prepara tion ofa rubber inner liner 27 for thetyre 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 atvarious stages of its manufacture. The former 11 has a diameterlargerthanthe bead diameterofthe tyreto be built thereon.

As shown in Figure 3 the inner liner 27 is in process of formation bywinding 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 laythe strip on the discs and the winding processes by axial movement of the roller 25 from left to right to form a continuous butt-orscarfjointed layer. Normally,two layers ofthe strip 10 are wound with the joints ofthe second layer staggered relative to the joints of the first layer.

Figure4 shows the completion of the winding to form the inner liner 27. Since the winding is laid helically it will be necessaryforthe ends to betrimmed (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.

Itwill be notedthatthe 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 Figure3tothe position shown adjacentthe disc 18 in full lines in Figure4atthe opposite end of the former. The disc 19 moves axially to remain in alignment with the strip so asto supportthe strip as it iswoundacrosstheformer.Thisenablesa hollow formerto be employed, and thus to allow all thetyre building operations including shaping to be carried out on the same former. Afterthewinding of the inner liner the disc 19 returns to the position shown in dotted lines in Figure 4 in the central region ofthe former.

Figure 5 shows the end portions 28,29 ofthe liner turned down (radially inwardly) against the end sur faces ofthe 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 similarto that disclosed in published patent application GB2159185Awhich comprises a pair of longitudinally extending rotatable spindles mounted in spaced apart parallel relationship one for each edge ofthe 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.

The preparation of the ply further comprises the step of applying thin sheets of unvulvanised rubberto the upper and lower surfaces of the cord winding as it emerges from the spindles thus producing a rubberised paraliel-cord ply in which the edges having unrubbered loops of cord protruding from the edges of the rubberised fabric.

Supportelements,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 36 at each edge of the ply subsequently to form hooped support elements at each edge of the plywhen it is formed into a cylindrical shape.

The support element may be located into the loops afterthecord ply has been rubberisedoralternatively may be located into the loops prior to cords being rubberised.

One method of incorporating the wires into the loops isto pass each support elementwirethrough the centre of a respective spindle so that the loops of cord are held on the support elements as they are removedfromthespindle.

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 Figure6thuscomprisesa cylindrical layer of rubberised cord material 31 in which the cords lie in the axial direction and have loops 36 passing around support wires 32,33. After forming the support wires to circularform around the formertheir ends are welded (adjacent cord loops being parted to enable welding electrodes to be inserted without darnaging the fabric) and the circled supportwires are then crimped so as to enable the ends 34 and 35 ofthe ply to be turned radially down the ends of the former as shown in Figure 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 ofthe 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 hoopedturns of continuouswire bundledtogether 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 ofthe 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 ofthe bead assembly.

Apparatusforforming the supportwires 32, 33to the crimped condition shown in Figures 7,8, 12 and 13 is not illustrated but may take the form of a series ofcoaxially extending fingers arranged initially around two pitch circles of different diameters and moved axiallytowards the former, respectively, ra diallywithinandradiallyoutsidethewire32or33.

The fingers are then contracted the outerfingers being drawn radially inwardly to a greater extentthan the innerfingers so as to deform the supportwire 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 againsttheturneddown 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-builttyre carcass following release ofthe supportwires. A further operation, shown in Figure 10, is then employed to press the supportwires into engagement in the suitable annular notches 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. Othertyre components such as apexes, chaffer strips, etc., may be added atthis 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.21 34439A.

Figures 14to 20 show a second method also of manufacturing a pneumatictyre 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 referenceto Figures 1 to 9. The building former assembly 100 comprises three rotatable discs 101,102, and 106 and its operation is generally similarto that described above in relation to Figures 3 and 5 except that only three discs are used. The winding commencing on a pairofdiscs 101 and 102 of which the disc 102 is moved to the right, supporting the liner 103 as itis wound under a moving roller 104,and the winding terminates on a disc 106. Thethreecoaxial discs 101, 102, 106are 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 ofthe discs 101 and 106 towards or away from each other in a known manner. Figure 1 5 shows the dise 102 in its central position and the inner liner 103 being cutto length by disc cutters 135.

Figure 16 shows the addition ofthe carcass reinforcement ply 30 (omitted from the lower part ofthe drawing) in which the portions containing support wire elements 108, 109 project beyond the edge ofthe former assembly, and in this examplethe overall diameter ofthe 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 intothetyre carcass.It will be noted thatthesupportwires 108,109 may beformed as a broken ring in which the ends ofthewire length are not welded together but have a short overlap to enable the circled supportwiresto be expanded in diameter, before welding, to the final diameterre- quiredtofitin the required position against the bead wire assembly.

Figure 17 shows the bead wire assemblies 115 and 116 placed in position overthe liner and ply on the former 100 and Figure 18 shows the expansion of discs 101 and 106 to grip the bead wire assemblies 115,1 16,throughthe ply. The disc 101 and 106in dude radiallyslidable segments 136 and 137, having inclined cam surfaces 138 on the radially inner end portionsthereofwhich are engagable on a conical dise 140 slidably mounted on the shaft 130. Thesup- portwires 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 buy a suitable device into engagement with corresponding notches 118,119formed, respectively, in the bead wire assemblies 115, 116 (as pre viously 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, pre-moulded sidewalls carried on suitable sidewall moulding plates are added and the whole assem bly is cured as described in our U.K. Application No.

2134439A.

Figures 21,22 and 23 show in more detail thesequence 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 offlexible plastics material extending from one end oftheformerto 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 alignmentwith the roller 104, to move with in the sleeve 120 across the axial width ofthe 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 counteranytendency 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 expandedto grip and position the bead assembly 115, the expansion ofthe segments 137 providing a shoulderforaccurate location of the bead wire assembly.

In Figure 23 the shaping of the tyre carcass with apexstrips 122 now added isillustrated,and inthis operation the central portion ofthesleeve 120 isdeflected radially inwardly by the inflation pressure, which it serves to retain bysealingthe 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 233forthe loops are actually constituted by a single turn of the bead assembly 215.

Thus, in Figure 24, the bead assemblies 215 are formed simultaneously as the ply 30 is wound onto theformer 100.The operation oftheformer 100con- tinues as before.

Claims (15)

1. A method of manufacture of a pneumatictyre including winding a cord reinforcement around a pair of spaced members to form a ply of continuous reinforcement cord having a series of loops adjacent the edges of the ply, rubberising the cordsto form a reinforced elastomeric ply, locating at least one support element in the loops at each edge ofthe plyto form hooped support elements at each ply edge and shaping the ply into a cylindrical form, locating bead wire assemblies coaxially of the cylindrical ply together with the support elements and incorporating the support elements in each respective bead wire assembly to anchorthe loops of cord to each respective bead assembly.

2. A method according to Claim 1 wherein thin sheets ofunvulcanised rubber are applied to the upper and lower surfaces of the cord ply as it emerges from the pair of spaced members.

3. A method according to Claim 1 or 2 wherein the support elements are formed into rings by circling the support elements and joining theirends and the ply is wrapped around a former of a diameter greaterthan the bead wire assemblies, and the circled support elements are then crimped to reduce their diameters, bead wire assembliesthen being passed over the reduced-diameter support elements which are subse quently released to resumetheir natural circularcon- figuration and then pressed into engagement with the respective bead wire assemblies.

4. A method according to Claim 1 or2whereinthe ply is wrapped around an expansible former at a diameter less than the internal diameter of the bead wire assemblies, the bead wire assemblies are then located around the ply, the former is expanded to grip the bead wire assemblies through the ply, and the endsofthesupportelementsarethen secured together at the diameter required to fit againstthe bead wire assemblies.

5. A method according to any of Claims 1 to 4 wherein an inner lining forthe ply is formed by continuous helical winding of strip material around a former comprising a series of rotating discs, at least one disc travelling axially during the winding process from a position at one end oftheformerto a position at the other end oftheformer, to remain in axial alignment with the portion of the strip material being wound onto the drum.

6. A method as claimed in Claim 1 or 2 in which each bead wire assembly comprises a plurality of bundled together hoops of continuous wire, and wherein the support element is formed from at least one hoop ofthe continuous wire which is located in the loops atthe respective ply edges.

7. Amethod accordingto anyoneof Claims3,4,5 or6 in which the support elements are fedthrough the centre of each spaced member as the ply cord is wound around, to hold the loops ofthe ply cord emerging from the spaced members.

8. Asubstantially cyiindrical former comprising at least three rotatable coaxial discs for supporting a tyre carcass at their radially outer surfaces, one disc being associated with each axial end portion ofthe former, andthe other innerdisc being arranged to move between the two end portions of the former as to support a portion of an elastomeric plyto be helically wound thereon from a strip.

9. Atyre building former as claimed in claim 8, wherein a sleeve offlexible material extends between the two discs associated with the end portions ofthe former and the inner disc is axially movable within the sleeve.

10. Atyrebuildingformerasclaimed in claim 8Or 9 wherein the two discs associated with the end portions of the former are capable of simultaneous movementtowards and awayfrom each other, and each disc has radiallyexpandablesegmentsfor pressing a carcass ply against a bead assembly located around the ply.

11. Atyre building former as claimed in anyone of Claims 8, 9, or 10, wherein the discs associated with each end portion ofthe former each have two sets of radially expandable segments thereon, the axially in ner set ofsegments providing a shoulder for location of a tyre bead and the axially outer set of segments being expandable to press against the internal surface of said tyre bead.

12. A method of building a tyre substantially as described herein and with reference to Figure 1 and Figures 3 to 13 of the accompanying drawing.

13. A method of building a tyre substantially as described herein and with reference to Figure 1 and Figures 14to 20 ofthe accompanying drawing.

14. Amethodofbuilding atyresubstantiallyas described herein and with reference to Figure2,and Figures 14,15,19,20 and 24 of the accompanying drawings.

15. Atyre building former substantially as described herein and with reference to Figures 1 4to 23 ofthe accompanying drawings.