Tire building device

Abstract: A tire building device wherein a unistage drum (6) presents an inner shaft (7) having an intermediate portion fitted with an inner stitching device (11), and two end portions located on opposite sides of the stitching device (11) and supporting two half drums (12,13) connected to the inner shaft (7) via the interposition of respective slides (18), each of which is connected, on one side, in sliding and angularly fixed manner to the inner shaft (7), and, on the other, in rotary manner to the respective half drum (12)(13) which may be locked in relation to the respective slide (18) by means of a friction joint (53).

Description: The present invention relates to a tire building device. In particular, the present invention relates to a tire building device of the type comprising a unistage drum in turn comprising an inner shaft; two half drums mounted in sliding manner on the inner shaft and designed to move in relation to each other between an open idle position and a closed operating position; expandable clamping means on each half drum for clamping a respective bead; and a number of annular bladders on each half drum, selectively inflatable with pressurized fluid. EP-A-0 507 111 or co-pending Italian Patent Application n.T091A000211, filed concurrently by the present Applicant and to which full reference is made herein in the interest of full disclosure, relates to a method and device for joining stratified tire portions by means of an inner stitching operation, during which, the inner carcass of a green tire and the outer tread belt are assembled together inside a fixed stitching mold by rotating stitching devices over the inner surface of the carcass. The stitching devices push the carcass outwards so as to adhere perfectly to the tread belt, which in turn is pushed against the inner surface of the mold in contact with which the finished green tire is accurately formed. It is an object of the present invention to provide a building device of the aforementioned type enabling the assembly of a stitching device as described in said co-pending Italian Patent Application n.T091A000211, and enabling inner stitching of the carcass to be performed directly on the building drum, i.e. without removing the carcass. According to the present invention, there is provided a tire building device comprising a unistage drum in turn comprising an inner shaft; two half drums coaxial with said inner shaft and designed to move along the same and in relation to each other between an open idle position and a closed operative position; expandable clamping means on each said half drum for clamping a respective bead; and a number of annular bladders on each said half drum, selectively inflatable with pressurized fluid; characterised by the fact that it also comprises inner stitching means between said half drums and fitted on to said inner shaft so as to rotate with the same; and slide means between each said half drum and said inner shaft; each said slide means being connected to said inner shaft in sliding and angularly fixed manner; each said half drum being connected for rotation to said respective slide means so as to rotate in relation to the same about the axis of said inner shaft; and connecting means being provided between each said half drum and said respective slide means, and being selectively operatable for angularly locking said half drum to said respective slide means. A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Fig.1 shows a schematic view, substantially in block form, of a preferred embodiment of a tire building device in accordance with the present invention; Fig.2 shows a section of a preferred embodiment of a Fig.1 detail in two different operating positions; Fig.3 shows a larger-scale axial section of a detail in Fig.2. Number 1 in Fig.1 indicates a unit for building a green tire 2 comprising a tread belt 3 and an inner carcass 4 with two metal beads 5. Unit 1 comprises a tire building device consisting of a building drum 6 extending through tire 2 and in turn comprising a powered hollow inner shaft 7 turning about its axis 8, and a tubular body 9 outside drum 6 and co-axial with axis 8. The inner surface of tubular body 9 is fitted with a toroidal body open along its inner edge and constituting a stitching mold 10 for tire 2. Stitching mold 10 is described in detail in co-pending Italian Patent Application n.T091A000213 filed concurrently by the present Applicant and to which full reference is made herein in the interest of full disclosure. Unit 1 also comprises an inner stitching device 11 constituting a portion of drum 6, supported on an intermediate portion of shaft 7, and comprising stitching elements 11a designed to move radially, in relation to shaft 7, between a withdrawn idle position wherein elements 11a are housed inside drum 6, and an extracted operating position wherein elements 11a engage the inner surface of tire 2. Stitching device 11 forms the object of said Italian Patent Application n.T091A000211. As shown in Fig.2, drum 6 comprises two hollow cylindrical half drums 12 and 13 mounted on shaft 7 on opposite sides of a coupling 14 fitted on to an intermediate portion of shaft 7 and in turn fitted with device 11. An outer surface portion of coupling 14 is connected for rotation to the inner surface of a further coupling 15, from the outer edge of which a number of radial brackets 16 extend outwards. The outer end of each bracket 16 is connected to the inner surface of an intermediate annular body 17 having an inside diameter greater than the outside diameter of half drums 12 and 13, and having a number of openings 17a engaged, in use, by elements 11a of device 11 in said extracted position. As half drums 12 and 13 are substantially identical, the following description will be limited solely to half drum 12, any parts of which not shown will be referred to using the corresponding parts (if shown) of drum 13. As shown in Fig.2 and particularly in Fig.3, half drum 12 is connected to shaft 7 by a respective slide 18 comprising a cylindrical tubular body 19 coaxial with shaft 7 and connected to the outer surface of shaft 7 by means of two annular shoes 20. Tubular body 19 presents an outer annular flange 21 on a first end facing coupling 14, and, on the second end opposite the first, an outer thread 22 engaged by the inner thread of an annular body 23 extending radially outwards from the outer surface of tubular body 19. Shaft 7 is fitted inside with a power screw 24 having two opposite threads 25, one for each slide 18. Each thread 25 is fitted with a nut screw 26 having a gripping device 27 on the outside for locking the end of a respective radial pin 28 extending outwards through a respective axial opening 29 formed through shaft 7. Pin 28 presents a number of helical outer grooves 30 forming part of a known fast-fit device enabling rapid assembly of pin 28 through a radial hole 31 formed through an appendix 32 extending axially outwards from the axial surface of annular body 23 opposite that facing flange 21. Thus, when screw 24 is rotated, nut screw 26 is displaced without rotating, thus resulting in displacement of pin 28 along respective opening 29, and displacement of slide 18, which is prevented from rotating about axis 8 by pin 28 engaging opening 29. Half drum 12 is mounted on the portion of slide 18 extending between flange 21 and annular body 23, and comprises a coupling 33 coaxial with tubular body 19 and connected for rotation to the outer surface of tubular body 19 via the interposition of two annular shoes 34 and 35. From the inner axial end of coupling 33, i.e. the end facing flange 21, there extends radially outwards a flat annular wall 36, the outer edge of which is fitted integral with the intermediate portion of a tubular body 37 extending axially outwards of and coaxially with coupling 33. Tubular body 37 presents a number of radial through openings, each forming the outlet of a radial chamber 38 housing a respective piston 39 in the form of a circular sector forming part of a clamping device 40 for a respective bead 5. For each piston 39, device 40 comprises a connecting rod 41 between piston 39 and a tubular piston 42 common to all of connecting rods 41 and mounted so as to slide in contact with the outer surface of coupling 33 by virtue of a variable-volume bladder 43 supported on a flat annular wall 44 extending outwards from the outer end of coupling 33. Bladder 43 is connected (in a manner not shown) to a compressed air supply (not shown) for axially displacing piston 42 to and from flange 21, and pistons 39 to and from an extracted position wherein respective bead 5 is clamped to respective half drum 12. As shown in Fig.2, piston 42 is prevented from rotating on coupling 33 by an axial pin 45 mounted in sliding manner through piston 42 and integral with wall 36. The return movement of piston 42, following a fall in pressure inside bladder 43, is assured by a number of springs 46 (Fig.2) compressed between wall 36 and piston 42. The outer surface of tubular body 37 is fitted with the connection feet 46 of two annular bladders 48 and 49 located on opposite sides of the ring of pistons 39, which support the annular connection foot 50 of a third bladder 51 lying, when idle, over bladder 48. As shown in Fig.3, the outer surface of wall 44 is fitted integral with a friction ring 52 of a friction joint indicated as a whole by 53 and comprising, in addition to ring 52, an annular piston 54 mounted in sliding manner inside an annular chamber 55 formed on the surface of annular body 23 facing wall 44 and coaxial with axis 8. By means of compressed air fed into chamber 55 via duct 56, piston 54 is moved axially, against the action of springs 57, into a position frontally contacting ring 52 and wherein half drum 12 is locked angularly in relation to slide 18. In use, screw 24 is rotated to set drum 6 to the idle position shown in the bottom half of Fig.2, wherein half drums 12 and 13 are open. Drum 6 is then loaded in known manner with the body plies (not shown) of carcass 4, and with beads 5 which are fitted outside pistons 39 of respective clamping devices 40 and clamped in known manner on to the body plies by activating devices 40. When clamping device 40 is activated, pistons 39 are pushed outwards in known manner to clamp beads 5 into position. Compressed air is then fed into bladders 48, 49 and 51 to turn the outer portions (not shown) of the body plies up around beads 5 and commence the building of carcass 4, which is done by activating screw 24, simultaneously with the compressed air supply, to set half drums 12 and 13 to the closed operating position. During the building of carcass 4, tubular body 9 is moved up to drum 6 so as to position stitching mold 10, housing tread belt 3, outside drum 6 for receiving carcass 4 which, as it is being built, expands outwards until it eventually adheres to the inner surface of tread belt 3 and is locked angularly in relation to mold 10. At this point, friction joints 53, which were formerly locked, are released to enable half drums 12 and 13 to rotate in relation to respective slides 18 and about axis 8. Subsequently, as described in co-pending Italian Patent Application n.T091A000211, rotation of shaft 7 results firstly in the extraction of elements 11a through openings 17a and, secondly, in the inner stitching of carcass 4 in contact with tread belt 3 and the inner surface of mold 10 so as to produce a finished tire 2, which is maintained stationary by mold 10 throughout the inner stitching operation by device 11. The presence of slides 18, of the rotary connection between half drums 12 and 13 and slides 18, and of friction joints 53 therefore provides, on the one hand, when joints 53 are locked, for producing carcass 4 in known absolutely standard manner, and, on the other, when joints 53 are released, for inner stitching tire 2 by maintaining tire 2 stationary and rotating shaft 7 about its axis.

Claims: A tire building device comprising a unistage drum (6) in turn comprising an inner shaft (7); two half drums (12,13) coaxial with said inner shaft (7) and designed to move along the same and in relation to each other between an open idle position and a closed operative position; expandable clamping means (40) on each said half drum (12)(13) for clamping a respective bead (5); and a number of annular bladders (48,49,51) on each said half drum (12)(13), selectively inflatable with pressurized fluid; characterised by the fact that it also comprises inner stitching means (11) between said half drums (12,13) and fitted on to said inner shaft (7) so as to rotate with the same; and slide means (18) between each said half drum (12)(13) and said inner shaft (7); each said slide means (18) being connected to said inner shaft (7) in sliding and angularly fixed manner; each said half drum (12)(13) being connected for rotation to said respective slide means (18) so as to rotate in relation to the same about the axis of said inner shaft (7); and connecting means (53) being provided between each said half drum (12)(13) and said respective slide means (18), and being selectively operatable for angularly locking said half drum (12)(13) to said respective slide means (18). A device as claimed in Claim 1, characterised by the fact that it also comprises a control device (24,26,28) for moving said slide means (18) along said inner shaft (7), together with said respective half drums (12,13), between said open and closed positions; said control device (24,26,28) comprising, for each said slide means (18), a screw element (25) coaxial with and housed inside said inner shaft (7), and a nut screw (26) connected to said screw element (25); connecting means (28) being provided for connecting said nut screw (26) to said respective slide means (18). A device as claimed in Claim 2, characterised by the fact that, for each said connecting means (28), said inner shaft (7) presents an axial guide opening (29) engaged in sliding manner by said connecting means (28). A device as claimed in any one of the foregoing Claims, characterised by the fact that each said slide means (18) comprises a tubular body (19) coaxial with said axis (8) and connected in sliding manner to the outer surface of said inner shaft (7). A device as claimed in Claim 4, characterised by the fact that each said half drum (12)(13) comprises a cylindrical inner coupling (33) coaxial with said axis (8) and connected to the outer surface of said tubular body (19) so as to rotate about said axis (8). A device as claimed in any one of the foregoing Claims, characterised by the fact that said connecting means (53) between each said half drum (12)(13) and said respective slide means (18) comprise a releasable friction joint.

Inventors: SIEGENTHALER KARL J, SIEGENTHALER, KARL J.
Applicants: BRIDGESTONE FIRESTONE INC, BRIDGESTONE/FIRESTONE, INC.
Application year: 1992
Main classification: B29D30
IPC codes: B29D30