IMPROVEMENTS MADE IN SEAMED TUBULAR TYRES FOR CYCLES

Abstract: The tubular-tyres for cycles having the carcass seamed on the intrados, presents the stitching (6) protected by an outer band (5) which is extended axially from one extremity to the other of the surface which is in contact with the mounting-rim. The band is jointed by overstitching, and the outer edge (10) of the overstitching is separated from the inner edge (20) - in correspondence of a limited zone, in the proximity of the band-end, by means of an anti-adhesive plate (13). The circumferential sides of the said plates, materialize two predetermined circumferential lines of fracture (11, 12) that allow for tearing the band along these lines - for, in this way, baring the stitching and simultaneously safeguarding the band-ends and the corresponding carcass zone.

Description: The present invention concerns tubular-tyres for cycles - and in particular, those tubular-tyres that are seamed. This type of tyre is well-known to everyone by now - and since a very long time ago. It is comprised by a carcass - i.e. by a rubberized fabric-strip, provided with reinforcing cords, which was firstly jointed at its two extremities - for realizing a cylindrical sleeve; thereafter, the edges of the said sleeve were folded-back (over themselves), axially and radially inwardly, in such a way as to form an annular toroidal body. Inside this toroidal container, there is housed an inner air-tube which is provided with an inflation-valve - and thereafter, the two sleeve edges are stitched together - so as to close the container. Usually the valve is made to protrude outwards through the stitching. For reinforcing this jointing-zone of the carcass, the borders of the two edges are usually also turned-up, radially and axially outwardly, for a small length. Moreover, for preventing the stitched-seam from coming into contact with the surface of the mounting-rim, there is disposed a fabric band, over the above-said stitched-seam, which is either glued or vulcanized onto the tube. When, during exercise, the tubular-tyre is punctured - or rather, when the air-tube is perforated, the band is torn-off the tubular-tyre so as to bare the stitched-seam. This latter is cut, in correspondence of the hole in the air-tube (the position of the hole, is previously indicated by means of an absolutely known technique), and for a certain length that is sufficient for extracting the portion of air-tube to be repaired. The hole is stopped-up - also in the usual manner, and the air-tube is reinserted into the tubular-tyre, after which the borders of the latter are re-stitched again, for completely reclosing the tubular-tyre. Finally, also the band is once again glued over the stitched seam - for thus restoring the integrity of the tubular-tyre, for further exercise. The arduous, if not complex procedure just described, nevertheless results as still being worthwhile - if the price of buying a new tubular-tyre exceeds the cost for repairing the same. Naturally, it is even more worthwhile if the difference existing between these two expenses is great. This, of course, is also provided that the tyre to be repaired, is still in a good enough state for being utilized further. In the field of tubular tyres for cycles, there have recently been put on the market - particularly by the Applicant himself, new and even more specialized products that have brought about a considerable progress in the field - with all the qualitative advantages involved thereby. The most representative tubular-tyre of this sort, is the tubular-tyre having a tunnel-shaped cross-section - with a special base-profile and with the joining-corners, between base and flanks, being opportunely reinforced, so much so that - apart from all its other advantages, this tubular-tyre also allows for it to be mounted both, on the rims for tubular-tyres - of the racing-car type, as well on the rims for bead-tyres - that are provided on their edges with check flanges for the above-said beads. Undoubtedly, this type of tyre does present a high qualitative level and also allows for giving an exceptional performance. However, such tyres are more costly than the alternative normal tyres and tubular-tyres - that are found to be cheaper on the market. So that, what the tyre-buyer also expects, is to be able to have his new type of tubular-tyres repaired in the above-described traditional way. On the other hand, in the stitched version of these new tubular tyres, the seam-covering band takes an active part and has an important function in the reinforcing structure of the corners, between base and flanks, of the tunnel-shaped cross-section. So much so that tearing-off of the band - and especially if done without any particular care, sensibly prejudices the behaviour characteristics and usefulness of the repaired tubular-tyre, with depriving it, for example, of any possibility that the new tubular-tyre has of being mountable alternatively on any whatsoever type of rim. The said plate, presents at least one extremity protruding in the circumferential direction, from the extremity of the said band - or else, as an alternative, it presents at least one extremity protruding axially outwardly with respect to the band, issuing out of one of said incisions. Preferably, the band extremities are circumferentially jointed - by overlapping them, while the band is realized from a rubberized fabric that is reinforced at least with cords disposed longitudinally. Moreover, should the tyre present a base-surface countermarked by two lateral portions and a central portion that is clearly distinguished by said lateral portions, the above-said incisions - are then disposed in correspondence of the axially inner extremity of the above-said lateral portions. It is also known from the Patent FR - A - 539 273, - which corresponds to the preamble of claim 1 - a tubular - tyre for bicycles comprising a strip that can be removed in the axial direction from a seam - covering band by means of a fracture - line in order to uncover the seam. This Patent, however, discloses how to uncover only a small portion of this seam. Moreover said strip in order to make easier its tear does not totally adhere to the tubular - tyre, but only to a part of it. The object of the present invention is to overcome all the above described drawbacks providing a tubular-tyre for cycles having, in correspondence of its radially inner development, a base-surface provided with an axial profile matchable with the corresponding profile of the mounting-rim profile, and comprising a carcass formed by at least one rubberized fabric-strip, whose ends are joined to form a ring, and whose two opposite edges are being jointed together in the longitudinal direction and in the radially inner position to said strip by a stitched-seam covered on its outside with a protective band reinforced with textile cords having a circumferential lay-out with respect to the tyre, said band being axially extended at least from one extremity to the other of said base-surface and being breakable in a predetermined way by two fracture lines characterized by the fact that said fracture lines have a circumferential lay-out with respect to the tubular-tyre, and are disposed exially inside said base-surface and plane of said tyre and are materially determined by corresponding incisions made on the band in the proximity of one extremity of said band and that a plate of a non-vulcanizable, anti-adhesive material is disposed between said band and said carcass, in the zone comprised between said incisions. In any case, the present invention will be better understood with the aid of the following description and from the attached figures - that are given solely by way of non-limiting example, whereby: FIG. 1 - shows the tubular-tyre of the invention, in its more generical form of realization. FIG. 2 - shows the tubular-tyre of the invention - in a particular form of realization, with the tunnel-shaped section. FIG. 3 - shows the tubular-tyre of the invention, when the seam-covering band is being torn-off - during the repairing phase. FIGS. 4, 5 and 6 - show the realization of the seam-covering band, according to two diverse alternative solutions. With reference to FIG. 1, the tubular-tyre comprises a carcass with a circular cross-section, comprised by a ply 1 - whose edges 2 are folded- back (over themselves) and hence, turned-up axially and radially inwardly, and finally stitched together for realizing a closed tubular body. Inside said tubular body, there was connected, prior to the stitching, an air-tube 3 - provided with an inflation-valve (not shown). In the radially outer position, the said carcass presents a rubber strip 4 that costitutes the tread-band, which will contact the ground, during tyre exercise. In the radially inner position, the carcass is provided - on its outer surface, with a band 5 (which is substantially as wide as the surface portion of the tubular-tyre), for contacting the surface of the mounting-rim, having the function of favouring the tubular-tyre/mounting-rim union after their gluing, and of protecting the stitching thread 6 - precisely from having any direct contact with the surface of said mounting-rim. Passing over now to to FIG. 2 - the differences from the tubular-tyre of FIG. 1, are obvious. Apart from the fact of this carcass comprising a second reinforcing ply 7, the cross-section of said tubular-tyre is no longer circular - but tunnel-shaped. In other words, the above-said cross-section presents a base having a special axial profile, comprised substantially by two lateral portions 8, having the axial profile almost parallel to the tyre axis, and by a central concave portion 9. The sidewalls of said tubular-tyre (proceeding radially outwardly) are initially rectilineal and successively, by curving axially inwardly - they go inwards, for in this way, defining the characteristic barrel-vault form of the tubular section of the tyre. The union of the sidewalls to the base, is comprised by a rather sharp corner - i.e. having an angle of about 90° - and even of a lesser value. The seam-covering band 5 extends axially, at least from one corner to the other of the tubular-tyre - but, in the preferred version shown, it even turns-up around the above-said corners - by ascending, for a certain tract, the side-walls of the tubular tyre. Said band constitutes one of the reinforcing elements of the structure of the tubular-tyre, at the above-said corners. FIG. 4 illustrates the cross-section of the band, disposed on the tubular-tyre, in a view orthogonal to the equatorial plane m-m, of the carcass. Practically speaking, the band presents an overlapping portion which, at the joining point, results as protecting the stitching more efficaciously than could be done - by the also possible, butt-splicing (not shown). The above-said band is realized from a rubberized fabric - either woven or cord, provided with reinforcing textile cords - that are made out of any whatsoever appropriate known material. The band must be prepared in such a way that said cords (in the cord-fabric), or at least, a group of cords (in the woven-fabric) , have a circumferential lay-out with respect to the tyre. The above-said band can be disposed - in a non-vulcanized state, on the raw - and in this case, it is welded to the same - through the successive vulcanizing process, or else, it can be glued to the carcass even in the phase successive to that of vulcanizing - in particular when the band, or the carcass - or both these elements, are already in a partially vulcanized state - prior to their being reciprocally assembled. In said case, the gluing can be favoured by using opportune adhesives. From said figures - and particularly from FIG. 2, what is immediately apparent is the serious damaging effects done to the carcass's structural resistence - in particular, in the delicate lateral zones, by the said tearing-off, of the band from the surface of the carcass - in the vulcanized tyre, during tyre exercise. According to the invention, the band is hence, provided with at least two pre-determined zones of fracture, in correspondence of a circumferential line - not coinciding with the joining-line of the carcass-edges - i.e. in correspondence of the stitching. According to the invention, the pre-determined fracture-lines are two in number and are disposed symmetrically with respect to the equatorial plane of the tyre, in an axially inner position respecting the base-width of the tubular-tyre and, in the case of the tubular-tyre having a tunnel-shaped cross-section, they run along the line of demarcation, between the flat-zone and concave-zone of the base-profile, as deferentiated by the more or less sharp change in the curve of the above-said profile. In FIGS. 1 and 2, these fracture-lines are defined by the points FS and FD. FIG. 3 shows, in a clear manner, the just described characteristic. Said pre-determined zones of fracture, are realized through inserting into the overlapping zone - between the two extremities of the band, or - as an alternative, even between the band and the carcass, a plate made of a non-vulcanizable material which is incapable of realizing any adhesion with the surrounding rubberized fabric - for, in this way, creating a zone, in the total width of the band, that is axially narrower and in coincidence with which, the outer band does not adhere to the underlying fabrics. In the plastic materials' field, the question just arises of selecting an apt material for realizing the said plate. For example, the Applicant finds it opportune to use a polyesther - that is commercially known as mylar. FIG. 5 shows a first form of solution, for solving the problem. In this figure - as in FIG. 6, the two overlapped extremities of the band 5 - are planned so that the edge that lies in the innermost position, is wider than the over-lapping edge. This artifice - which does not exist in the practical realization, has the sole purpose of facilitating the comprehension of the text and of the drawings. According to the solution shown in FIG. 5, between the outer edge 10 (of band 5) and the inner edge 20, there is inserted a plate 13 made of the above-said anti-adhesive material; with said plate being narrower than the width of said edge 10. In particular, the plate has the same axial width as the portion comprised between the pair of points FS and FD (see FIGS. 1 and 2) with a length of a few centimeters - and preferably, it is disposed in such a way as to protrude circumferentially, from the extremity of the outer edge. It is very clear that, during the vulcanization of the tyre, it will be made quite impossible for said outer edge to adhere to the surrounding rubberized fabrics, in correspondence of the area protected by plate 13 - so much so that the sides of said plate determine the above-mentioned pre-determined fracture-lines on the outer edge. As an alternative, according to the solution that is shown in FIG. 6, the anti-adhesive plate 13 is now, no longer oriented longitudinally - but transversally with respect to the tyre, and it is made to pass through two, previously made incisions 11 and 12, still on the outer edge of the band - in such a way as to protrude axially from at least one of these incisions, but preferably from both (just as is shown in the figure). The width of the plate 13 - must be less than the length of the outer edge against which it rests, in such a way as to allow for the said edge to adhere to the underlying fabric - at both sides of the plate, the effect of which will still be of impeding any gluing taking place, between the outer edge and the underlying fabric, in correspondence of the area protected by the plate. The two incisions 11 and 12, can be extended from the border of the edge 10 - upto the furthest circumferential border of plate 13 (as indicat- ed in FIG. 6), but they could even be just restricted to the tract in correspondence of said plate. Obviously, in this latter case, the operation of inserting the plate into the two above-said incisions, will be more arduous. The behaviour of this band will now appear easier to understand, with also making particular reference to FIG. 3. Hence, once the need to proceed with repairing the air-tube (inserted into the tubular-tyre) is verified - firstly, and if the tyre is realized according to the version of FIG. 6, a transversal cut is made, from the part nearest to the edge extremity, that joins the two longitudinal incisions 11 and 12. Whereas, if the tyre is realized according to the version of FIG. 5, two incisions (11 and 12) are made in correspondence of the sides of the plate 13. Resulting from the presence of the anti-adhesive plate that can now be removed, there is created a band-tongue 14 - delimited by the indicated cuts, that is not attached to the carcass. This tang is now taken hold of, and the tearing off - of the band, is carried-out. As a result of these two longitudinal incisions 11 and 12 - which have originated the pre-determined fracture-line, the band is detached from the tubular-tyre, with its continuing to break - along the above-said circumferential lines - for thus making bare the stitched-seam, but without, in the least way, damaging either the lateral portions or, with them, the corresponding carcass zone - in particular, the zones of corners, on the tubular-tyre that has a tunnel-shaped cross-section. Once the air-tube has been repaired and the tubular tyre re-stitched, the band is glued back into place - to be detached once again, should any successive further need arise for repairing the air-tube. The fact of the band being originally vulcanized - together with the carcass, does not constitute any obstacle as regards its being torn-off - along, in particular, the pre-determined fracture-lines. This is because the adhesion - between elastomeric material and cords (in particular those cords used for stitching the edges of the tubular-tyres), has a lesser adhesive force as compared to that existing between elastomeric materials - nor does it have such a value as to impede the detaching of the band from the above-said cords. The advantages of the invention are many, and also quite evident by now. In the first place, the band is assembled onto the carcass in a single operation, and the centering of the band - with respect to the equatorial plane of the tyre, is quite easily assured. In fact, it is quite clear that an alternative solution can be thought of - consisting of disposing, on the intrados of the tubular-tyre, three distinct adjoining bands - one in a central position, protecting the stitching, and the other two in lateral positions for reinforcing the corners and the lateral portions of the tubular-tyre surface - intended for coming into contact with the rim - in such a way as to isolate, right from the start, the band that is destined to be torn-off the tubular-tyre, should the need arise. Nevertheless, all the other technical and economical disadvantages to be had with a similar solution, are also evident. With the band according to the invention instead, it is made possible to realize the tubular-tyre with the same care and precision - as used for tyres which are not intended for being opened-up (the repairing takes place through using special sealing-substances that are injected from the outside into the air-tube) and hence, there is guaranteed for the same, the maximum qualitative level for the finished product. Moreover, with the need being verified for opening-up the tubular-tyre, the band (of the invention) having its pre-determined breaking zone, allows for carrying out all the operations of: the unstitching, repairing and re-stitching of the tubular-tyre - without interfering with the more important zones of the tyre structure, which fact is essential for having good tyre behaviour during exercise - and hence, the qualitative level of the tyre performance and the service life-time of the tyre, are not compromised.

Claims: Tubular-tyre for cycles, having in correspondence of its radially inner development, a base-surface provided with an axial profile matchable with the corresponding profile of the mounting-rim profile, and comprising a carcass formed by at least one rubberized fabric-strip whose ends are joined to form a ring, and whose two opposite edges (2) are being jointed together in the longitudinal direction and in the radially inner position to said strip (1), by a stitched-seam (6) covered on its outside with a protective band (5) reinforced with textile cords having a circumferential lay-out with respect to the tyre, said band (5) being axially extended at least from one extremity to the other of said base-surface and being breakable in a predetermined way by two fracture lines (11, 12) characterized by the fact that said fracture lines (11, 12) have, a circumferential lay-out, with respect to the tubular-tyre, and are disposed exially inside said base surface and symmetrically with respect to the equatorial plane of said tyre, are materially determined by corresponding incisions made on the band (5) in the proximity of one extremity (10) of said band (5) and that a plate (13) of a non-vulcanizable, anti-adhesive material is disposed between said band (5) and said carcass, in the zone comprised between said incisions. Tubular - tyre, according to CLAIM 1, characterized by the fact that said plate (13) presents at least one extremity protruding in the circumferential direction, from the extremity of said band (5). Tubular - tyre, according to CLAIM 1, characterized by the fact that said plate (13) presents at least one extremity protruding axially outwardly with respect to the band, exiting from one of said incisions. Tubular - tyre, according to CLAIM 1, characterized by the fact that the extremities (10,20) of said band (5) are circumferentially joined to each other by means of overlapping. Tubular - tyre, according to CLAIM 1, characterized by the fact that said band (5) is a rubberized fabric, reinforced by at least longitudinally disposed cords. Tubular - tyre, according to CLAIM 1, having, in its cross - section, a tunnel - shaped profile, with the base - surface presenting two lateral substantially flat portions (8) and a central substantially concave portion (9) characterized by the fact that said incisions are disposed in correspondence of the axially inner extremity of said lateral portions.

Inventors: CARRERA, CESARE
Applicants: SOCIETA' PNEUMATICI PIRELLI S.P.A.
Application year: 1986
Main classification: B60C19
IPC codes: B29D30, B60C19, B60C3