PNEUMATIC TIRE

Abstract: A pneumatic tire (1) comprises a radial carcass (2), a tread portion (7) and a belt reinforcing structure (8) extending circumferentially around the carcass (2). Disposed radially outwardly of the belt reinforcing structure (8) is a textile reinforced overlay structure (9) having substantially circumferentially extending cords (10). The overlay structure (9) is composed of a series of helical convolutions of a textile ribbon (11) whereby adjacent helical convolutions of the textile ribbon (11) overlap. There is further disclosed a method of applying multiple layers of a single continuous helically wound textile ribbon (11) in a single continuous operation from one axial side to the other axial side of the belt reinforcing structure (8).

Description: This invention relates generally to pneumatic tires and more specifically to tires having a textile reinforced overlay structure located radially outwardly of a belt reinforcing structure. Such a tire is for example described in LU-85 964. In this prior art patent helical convolutions of a ribbon are wound axially across the belt reinforcing structure such that the convolutions are in abutting contact with each other. Although in practice tires using this construction have exhibited the benefits claimed in LU-85 964, there are a number of restrictions that the construction of this prior art tire imposes onto the manufacturing methods. The method described in this prior art reference has the drawback that if it is desired to form an overlay structure with two or more layers of the ribbon, two or more complete helical convolutions have to be applied from one axial side of the reinforcing belt structure to the other axial side. This involves a multiple step operation, which considerably slows down the manufacturing process. Document EP-A-0 258 822 discloses a pneumatic tire, corresponding to the preamble of claim 1, having a textile reinforced overlay structure comprising a series of helical convolutions of a cord reinforced ribbon. Adjacent convolutions are in an overlapping relationship in the shoulder portions of the tire tread and in abutment or slightly spaced in the center portion of the tread. An object of the invention is to provide a tire with reduced polyester. A further object of the invention is to provide a tire which can be manufactured more economically and using more flexible building methods. The above mentioned objects are achieved and drawbacks are averted by the pneumatic tire and by the method of manufacturing such a tire as defined in the appended claims. The invention will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of a pneumatic tire according to this invention; Figure 2 is a schematic view of the ribbon utilized for the construction of the overlay structure; Figure 3 is a schematic cross sectional view of the construction of the overlay structure as applied on a belt reinforcing structure of a first embodiment of the invention; Figure 4 is a schematic cross sectional view of the construction of the overlay structure as applied on a belt reinforcing structure of a second embodiment of the invention; Figure 5 is a schematic cross sectional view of a construction of the overlay structure as applied on a belt reinforcing structure of a third embodiment of the invention; Figure 6 is a partially schematic view of a two ply belt reinforcing structure in conjunction with an overlay structure and a tread portion; Figure 7 is another partially schematic view of a two ply belt reinforcing structure in conjunction with an overlay structure and a tread portion; and Figure 8 is a schematic view illustrating a method for applying an overlay structure on a belt reinforcing structure which is located on a tire building drum. The terms "axial" and "axially" as used throughout this specification refer to directions parallel to the axis of rotation of a tire. The terms "radial" and "radially" as used throughout this specification refer to directions perpendicular to the axis of rotation of a tire. With reference to Figure 1 there is illustrated a cross-sectional view of a pneumatic tire 1 having a radial carcass. A radial carcass ply 2 extends between a pair of annular beads 3,4. A sidewall 5 extends radially outwardly from each bead 3,4 to a crown region 6 of the tire. The crown region 6 has a ground contacting tread 7 extending circumferentially thereabout. The tire is reinforced in the crown region by an annular belt reinforcing structure 8 disposed radially outwardly of the carcass ply 2. The belt reinforcing structure 8 comprises one or more elastomeric plies 12,13 reinforced by steel cord or an other known suitable material, for example glass fiber, or aromatic polyamide. Radially outwardly of the belt reinforcing structure 8 there is disposed a textile reinforced overlay structure 9 having an axial width D between its lateral edges 14,15 such that it is at least as wide as the axial width C of the belt reinforcing structure 8 so as to completely cover it. As can be seen from Figure 1 and Figure 2, the overlay structure 9 comprises a helically wound ribbon 11, of elastomeric material having longitudinally extending cords 10 embedded therein, which extend circumferentially around the tire and substantially parallel with the mid-circumferential plane M-M of the tire, that is, they make an angle of between 0° - 5° with the mid-circumferential plane M-M. By "mid-circumferential plane" is meant a plane which is perpendicular to the axis of rotation of the tire and which is located midway between the beads 3,4. Adjacent helical convolutions of the ribbon 11 overlap. The ribbon has a width A, preferably in the range of 10 to 40 mm, and a thickness B, preferably in the range of 0.4 to 1.2 mm. Preferably the cords 10 of the ribbon 11 are made of a heat shrinkable material such as nylon. In Figure 3 there is schematically illustrated a cross section of an embodiment in which the overlay structure 9 comprises adjacent overlapping convolutions of the ribbon 11 disposed radially outwardly of the belt structure 8. In the embodiment shown here, and throughout this specification, the belt structure that is illustrated comprises two plies 12,13 with reinforcing cords making opposite angles with the mid-circumferential plane M-M of the tire. It is understood that the present invention is not limited thereto, but equally applies to tires having different belt structures. As can be seen from Figure 3, the adjacent convolutions of the ribbon 11 overlap. The width of the overlap between adjacent turns of the ribbon is indicated by an axial distance O. In the embodiment shown in Figure 3, the ribbon overlap is such that the axial width O of the overlap is uniform across the width of the belt reinforcing structure. The uniform axial width O of the overlap is determined by the following equation: O = W (1 - 1 n ) whereby: O = axial width of the overlap between adjacent turns of the ribbon W = width of the ribbon n = integer which represents the number of desired layers of the ribbon in the overlay structure. The number of desired layers of the ribbon 11 determines the axial width of the overlap 0 between adjacent turns of the ribbon 11. Figure 4 shows an example of a preferred embodiment in which the overlay structure 9 is divided into a center portion and a pair of axially outer portions. By center portion of the overlay structure 9 is meant the portion of the overlay structure 9 that extends axially outwardly on either side of the mid-circumferential plane M-M over about 25% of the width of the overlay structure 9, and by axially outer portions are meant the portions on either side of the center portion which extend axially inwardly from the axial edges 14,15 of the overlay structure 9 over about 25% of the width of the overlay structure 9. According to Figure 4, the overlap between adjacent helical convolutions of the ribbon 11 is such that the width O of the overlap is not constant across the width of the overlay structure 9 but is greater in the axially outer portions than in the center portion of the overlay structure 9. In the embodiment shown in Figure 4, the axial width of the overlap O S between adjacent turns of the ribbon in the axially outer portions of the overlay structure 9 is 0.75 times the width W of the ribbon, while the axial width of the overlap O C between adjacent turns of the ribbon in the center portion of the overlay structure 9 is 0.5 times the width W of the ribbon. The greater axial width of the overlap between adjacent helical convolutions of the ribbon 11 in the axially outer portions of the overlay structure 9 results in a greater density of cords in this area of the tire and hence, confers a greater strength to these areas. This may be desirable for counteracting the stresses which the tire experiences during service and which are most concentrated in its shoulder portions. In a further preferred embodiment of the invention, illustrated in Figure 5, the adjacent helical convolutions of the ribbon are arranged such that the width O of the overlap decreases continuously from each axial edge 14,15 of the overlay structure 9 towards the center of the overlay structure 9. In the embodiment shown in Figure 5, the axial width of the overlap O between adjacent turns of the ribbon decreases gradually from 0.75 times (O S ) the width W of the ribbon in the axially outer portions to 0.5 times (O C ) the width W of the ribbon in the center portion of the overlay structure 9, while there is also shown an intermediate value O i of the overlap between adjacent turns of the ribbon which are located between the axially outer portions and the center portion of the overlay structure 9, O i being 0.66 times the width W of the ribbon. With reference to Figure 6 there is provided a schematic view of a two ply belt reinforcing structure 8 in conjunction with an overlay structure 9 and a tread portion 7. As can be seen from this Figure, the first and the last convolution of the ribbon begin and finish at an axial distance beyond each axial edge 12, 13 of the belt reinforcing structure 8, the axial distance being at least equal to the width of the overlap as measured at the axial edges 12, 13 of the belt reinforcing structure 8. Such an arrangement of the ribbon 11 ensures that the entire belt reinforcing structure 8 is covered by the helically wound convolutions of the ribbon 11. The excess material of the overlay structure 9 beyond the axial edges 12, 13 of the belt reinforcing structure may be trimmed back to the axial edges 12,13 if it is so desired. Alternatively, as illustrated in Fig. 7, the axially outer edges of the first and the last convolutions of the ribbon 11 can be arranged such that they coincide with the axially outer edges 12,13 of the belt reinforcing structure 8 and that they are substantially parallel to the mid-circumferential plane of the tire, while the other convolutions of the ribbon 11 are all helically wound. This particular construction had the advantage that the axial width of the overlay structure 9 is identical to the axial width of the belt reinforcing structure 8 and that no trimming of the normally obtained excess material at the axial edges 12,13 of the belt reinforcing structure is required. As can be seen further from both Figure 6 and Figure 7, the overlay structure 9 is preferably applied such that the cords 10 of the overlay structure 9 are in a crossing relationship with the cords 8" of the radially outermost belt layer 8' of the belt reinforcing structure 8, i.e. are oriented in a direction opposite to the direction of the cords 8" of the radially outermost belt layer 8'. This crossing relationship of the cords helps towards reducing the tendency of the tire steering in a particular direction which tendency is commonly known in the tire art as ply steer. There are two alternative methods generally used for applying the overlay structure to the belt reinforcing structure. A first method comprises assembling the overlay structure around the belt reinforcing structure on a separate drum before the total belt assembly is applied on the carcass band, the belt reinforcing structure thus being built on a separate drum. A second method comprises assembling a tire whereby the overlay structure is assembled around the belt reinforcing structure during the final step of the tire building process, that is after that the belt reinforcing structure has been assembled around a toroidal tire casing. Figure 8 schematically illustrates the method for assembling a tire according to the present invention that can be used with either of the methods described above. In Figure 8, there is illustrated a drum 16 upon which there is placed a belt reinforcing structure 8. In the case of the second method as explained above, the drum would be replaced by a toroidal tire casing. The overlay structure 9 is placed around the belt reinforcing structure 8 by helically winding a single continuous ribbon 11 of cord reinforced elastomer around the outside of the belt reinforcing structure 8 from one axial edge 12 thereof to the other axial edge 13 thereof. In the embodiments shown, the ribbon 11 is wound in one continuous operation from the left hand axial edge 12 of the belt reinforcing structure 8 to its right hand edge 13, but could alternatively be wound in the other direction. The ribbon 11 is wound such that each helical convolution is in overlapping relationship with its respective adjacent helical convolutions. In a preferred embodiment of a tire according to the invention, as shown in Figure 3, adjacent convolutions of the ribbon 11 are applied in such a way that the axial width of the overlap between adjacent convolutions is uniform across the width of the belt reinforcing structure 8. The uniform width of the overlap is determined by the equation described above in conjunction with the pneumatic tire of the present invention. The method of the present invention equally applies to the manufacture of the other preferred embodiments of the pneumatic tires as described above and illustrated in Figures 4, 5, 6 and 7.

Claims: A pneumatic tire (1) comprising a radial carcass (2), a tread portion (7) and a belt reinforcing structure (8) having belt layers (8') with reinforcing cords (8"), which is radially interposed between the carcass (2) and the tread portion (7), a textile reinforced overlay structure (9) being located radially outwardly of the belt reinforcing structure (8), the overlay structure (9) comprising a series of helical convolutions of a ribbon (11) which comprises an elastomeric material reinforced by cords (10) arranged side by side and extending longitudinally of the ribbon (11), the cords making an angle of between 0° and 5° with the mid-circumferential plane of the tire and the adjacent turns of the ribbon (11) being in an overlapping relationship characterized in that the cords (10) of the overlay structure (9) are oriented in a direction opposite to the direction of the cords (8") of the radially outermost belt layer (8') of the belt reinforcing structure (8) with respect to the mid-circumferential plane of the tire. A pneumatic tire (1) as claimed in claim 1 characterized by adjacent turns of the ribbon (11) overlapping in such a way that the axial width (0) of the overlap between adjacent turns of the ribbon ( 11 ) is uniform across the axial width (C) of the belt reinforcing structure (8). A pneumatic tire (1) as claimed in claim 2 characterized by the uniform width (0) of the overlap between adjacent turns of the ribbon (11) being determined by the equation: 0 = W (1 - 1 n ) wherein: 0 = width of the overlap between adjacent turns of the ribbon; W = width of the ribbon; and n = integer equal to the number of desired layers in the overlay structure. A pneumatic tire (1) as claimed in claim 1 characterized by the overlay structure (9) being divided into a center portion and a pair of axially outer portions and by the width of the overlap being greater in the axially outer portions (0 s ) than in the center portion (0 c ) of the overlay structure. A pneumatic tire (1) as claimed in claim 4 characterized by the overlay structure (9) having a pair of axial edges (14, 15) and the axial width of the overlap decreasing gradually from each axial edge of the overlay structure to the center portion of the overlay structure. A pneumatic tire (1) as claimed in any one of claims 1 to 5 characterized by the axial width (D) of the overlay structure (9) being equal to the axial width (C) of the belt reinforcing structure (8). A pneumatic tire (1) as claimed in any one of claims 1 to 6 characterized by the axial width (D) of the overlay structure (9) being greater than the axial width (C) of the belt reinforcing structure (8). A pneumatic tire (1) as claimed in any one of claims 1 to 7 characterized by the width (A) of the ribbon (11) being in the range of 10 to 40 mm. A pneumatic tire (1) as claimed in any one of claims 1 to 8 characterized by the thickness (B) of the ribbon (11) being in the range of 0.4 to 1.2 mm. A pneumatic tire (1) as claimed in any one of claims 1 to 9 characterized by the reinforcing cords (10) of the ribbon (11) comprising nylon or polyester. A method of manufacturing a radial tire as claimed in any one of the preceding claims, comprising the step of placing a textile reinforced overlay structure (9) around the radially outer periphery of a belt reinforcing structure (8), by helically winding a ribbon (11) of cord (10) reinforced elastomer from one axial side to the other axial side of the belt reinforcing structure (8), applying each spiral convolution of the ribbon (11) in overlapping relationship with its respective adjacent spiral convolutions, the cords (10) making an angle of between 0° and 5° with the mid-circumferential plane of the tire, winding the ribbon (11) of the overlay structure (9) in such a way that its reinforcing cords (10) are oriented in a direction opposite to the direction of the cords (8") of the radially outermost belt layer (8') of the belt reinforcing structure (8) with respect to the mid-circumferential plane of the tire. A method as claimed in claim 11 characterized by the first and the last convolutions of the ribbon (11) beginning and finishing at an axial distance beyond each axial edge (12, 13) of the belt reinforcing structure (9), the axial distance being at least equal to the width (0) of the overlap, measured at the axial edges of the belt reinforcing structure (40). A method as claimed in any one of the claims 11 and 12 characterized by the axially outer edges (14, 15) of the first and the last convolutions of the ribbon (11) coinciding with the axially outer edges (12, 13) of the belt reinforcing structure. A method as claimed in any one of claims 11 to 13 characterized by the convolutions of the ribbon (11) being applied such that the first and the last convolutions of the ribbon are substantially parallel to the mid-circumferential plane (M) of the tire (1).

Inventors: BEER, KLAUS, BORMANN, RENE LOUIS, MAATHUIS, ANTONNIS GERARDUS, MEIJER, THEO, OARE, THOMAS REED, SPIELMAN, JUERGEN, Bormann, René Louis, Spielman, Jürgen
Applicants: THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1989
Main classification: B60C9
IPC codes: B60C9