BRPI0904870A2 - pneumatic - Google Patents

Abstract

PNEUMATIC A tire is described that includes a tread, a frame and a belt reinforcing structure interposed between the frame and the tread. The belt structure includes a pair of operating belts, in which the angle of the operating belts varies from about 15 to about 30 degrees, where the belt structure also includes a zigzag belt structure, located radially into the operating belts . The zigzag belt structure is formed of at least two layers of cords, interwoven together of a rubber strip reinforced with one or more cords, in which the strip forming the zigzag belt structure is arranged in a first zigzag winding, extending from a first side belt edge to a second side belt edge, in a zigzag wavelength having a first amplitude W1, followed by a second amplitude W2, in the direction opposite to said first amplitude. The zigzag belt structure is additionally arranged in a second zigzag winding, extending from a first side belt edge to a second side belt edge, in a zigzag wavelength having a first amplitude W2, followed by a second WI amplitude.

Description

"PNEUMATIC"

This patent application claims the benefit of, and incorporates by reference, U.S. Provisional Patent Application 61 / 139,168, filed December 19, 2008.

FIELD OF INVENTION

This invention relates to a tire having a carcass and belt-reinforcing structure, and more particularly to radial-toe-jointed tires in aircraft, trucks and other high-load applications.

BACKGROUND OF THE INVENTION

In tires that have to withstand heavy loads, such as truck tires or aircraft tires, zigzag belt layers have been used for strapping. Zigzag belt layers eliminate cutting off shoulder strap ends. An exemplary part of a pneumatic with a zigzag belt layer 5 is shown in Figure 1. The advantage of zigzag belt layers is that they do not cut belt edges near the shoulder, which greatly enhances the durability of the tire. The disadvantages of zigzag belt layers are that at the edges, near the shoulder, there is overlap of layers. In some areas there are too many layers, such as typically 4 or more layers and even 6 or more layers in some places. Reduction of overlapping shoulder straps has been shown to improve durability. Thus, it is desired to have a pneumatic with a non-overweight belt edge durability.

SUMMARY OF THE INVENTION

The invention provides, in a first aspect, a tire comprising a tread, a housing and a belt reinforcing structure interposed between the housing and the tread. The belt structure includes a pair of operating belts, in which the angle of the operating belts ranges from about 15 to about 30 degrees, and a zigzag belt structure. The zigzag belt structure is formed of at least two layers of strands, woven together of a reinforced rubber strip with one or more strands, wherein the strip forming the zigzag belt structure is arranged in a first zigzag winding, extending from a first side belt edge to a second side belt edge in a zigzag wave length having a first amplitude W1, followed by a second amplitude W2, in the opposite direction to said first amplitude. The zigzag belt structure is further arranged in a second zigzag winding, with a first side belt edge extending to a second side belt edge at a zigzag wave length having a first amplitude W2, followed by a second one. amplitude W1, in the opposite direction to said first amplitude.

The invention provides, in a second aspect, a tire comprising a tread, a carcass and a belt structure interposed between the carcass and the tread. The belt structure includes a pair of operating belts, wherein the angle of the operating belts ranges from about 15 to about 30 degrees, and a zigzag belt structure. The zigzag belt structure is formed by at least two layers of strands woven together from a strand of rubber reinforced with one or more strands, and wherein the zigzag belt structure is formed of a first zigzag winding having a first amplitude. WMax at a first lateral end and a second amplitude Wmin at a second lateral end, and WMax is greater than Wmin; and a second zigzag winding, having a first WMin amplitude at a first side end and a second Wmax amplitude at a second side end, and wherein the second zigzag winding is located adjacent said first zigzag winding.

DEFINITIONS

"Filling" means an unreinforced elastomer, positioned radially above a bead core.

"Appearance ratio" of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% expression as a percentage.

"Axial" and "axially" means lines or directions that are parallel to the tire's rotation axis.

"Bead" means that part of the tire comprising an annular tensioning element wrapped around canvas and molded, with or without other reinforcing elements such as bead covers, wire reinforcements, padding, nail protectors. and anti-friction agents, to fit the project rim.

"Bias tarpaulin tire" means a tire having a carcass with reinforcing ribs on the carcass ply extending diagonally from bead core to bead core at an angle of about 25 - 50 degrees to the dopneumatic equatorial plane. The strands extend at opposite angles in alternating layers.

"Carcass" means the tire structure apart from the belt structure, tread, tread, and side rubber over the tarps, but including the lugs.

"Circumferential" means lines or directions extending along the perimeter of the annular tread surface perpendicular to the axial direction.

"Anti-friction agents" refer to narrow strips of material placed around the outside of the bead to protect the strings from the rim strands, to distribute flexion above the strand, and to seal the tire.

"Wire ribs" means a reinforcement structure located on the pneumatic bead portion. "Cord" means one of the reinforcement filaments of which the pads on the tire are comprised.

"Equatorial plane (EP)" means the plane perpendicular to the axis of rotation of the tire and passing through the center of its tread.

"Copper bead" means a reinforced fabric wrapped around the core of the bead and the filler.

"Tread design" means the contact patch or contact area of the tire tread, with a flat surface at zero speed and under normal load and pressure.

"Inner lining" means the layer or layers of elastomer, or other material, which forms the inner surface of a tubeless tire and which contains the inflating fluid within the tire.

"End-initial ratio" means the ratio of the tire tread rubber, which makes contact with the rolling surface while printing the tread pattern, divided by the tread area in the tread pattern print, including contactless parts such as notches.

"Radial tarpaulin tire" means a circumferentially girdled or restrained tire in which the tarpaulins, which extend from bead to bead, are arranged at bead angles between 65 - 90 degrees with respect to the equatorial plane of the bead. pneumatic.

"Section height" (SH) means the radial distance from the nominal rim diameter to the outer diameter of the tire in its equatorial plane.

"Winding" means the strip model formed in a first revolution of the strip around a tire, tire or core construction drum.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a schematic sectional view of part of a prior art tire having a zigzag belt;

Figure 2 illustrates a partial cross section of an exemplary tire of the present invention;

Figure 3 is an example of a tire construction drum showing the belt of the present invention being formed;

Figure 4A is an example of a tire construction drum disposed circumferentially for illustrative purposes, illustrating a first integral revolution of the strip arrangement forming the zigzag belt;

Figure 4B is the tire construction drum of Figure 4A, illustrating only a second revolution of the zigzag belt drawstring model (the first revolution has been removed for clarity);

Figure 4C is a foreground view of the strap edge strap supporting a U-turn;

Fig. 5A is an example of a pneumatically disposable tire construction drum illustrative purposes illustrating a first integral revolution or first winding of the strip arrangement forming the zigzag belt;

Figure 5B is the tire construction drum of Figure 5A illustrating the second revolution of the drum showing the first and second windings of the strip arrangement forming the zigzag belt;

Figure 5C is the tire construction drum of Figure 5A illustrating the third revolution of the drum showing the first, second and third windings of the strip arrangement forming the zigzag belt;

Figure 5D is the tire construction drum of Figure 5A illustrating each revolution of the drum showing the first, second, third and fourth windings of the strip arrangement forming the zigzag belt;

Figure 6 illustrates the zigzag belt edge;

Figure 7 illustrates the cross-sectional view of the zigzag belt edge in sections A - A, B - B, C - C, D - D and E - E showing the overlapping of stretched layers;

Figure 8 illustrates the cross-sectional view of the zigzag belt edge in sections A - A, B - B, C - C, D - D and E - E, showing the overlap of stretched layers for the zigzag belt. from the prior art of Figure 1;

Figures 9A - 9C illustrate a zigzag belt having a transverse displacement of 0.1 mm and wherein the drum travel angle is varied from 6.75 degrees, shown in Figure 9A, to 13.5 degrees, shown in Figure 9B, and 27 degrees, shown in Figure 9C; and

Figures 10A-10C illustrate a zigzag belt having an 8mm cross-sectional displacement, wherein the angle of displacement of the drum is varied from 6.75 degrees, shown in Figure 10A, to 13.5 degrees, shown in Figure 10B, and 27 degrees, shown in Figure 10C.

DETAILED DESCRIPTION OF AN EXEMPLIFICATIVE MODE OF THE INVENTION

Figure 2 illustrates a partial cross section of an exemplary radial tire 10 including a bead portion 23 having a bead core 22 embedded therein, a side portion 24 extending radially outwardly of the bead portion 23, and a flat portion cylindrical tread 25 extending between the radially outer ends of the side portions 24. The tire 10 is reinforced by a housing 31, extending from one bead part 23 to the other bead part 23 '(not shown). The carcass ply 32 is anchored to the bead core, and may, for example, wrap around bead core 22 inside the tire 10, away from the equatorial plane EP, to form refolding parts. A belt reinforcement housing 40 is disposed between the housing 31 and the tread 25.

The belt reinforcement pack 40 according to an exemplary embodiment of the present invention includes a pair of operating belts 41, 42. The belt 41 is located radially into the 42. The belt 41 has a width that is approximately equal to the arc width of the tread. Preferably, the belt 41 has a belt width substantially equal to the tread arch width. Belt damper angle 41 is between about 16 and 30 degrees, preferably with a left orientation, particularly in the range of about 19 to about 25 degrees. Belt angles are measured with respect to the circumferential direction. The belt 41 is preferably made of steel having a 4 + 3x.35 construction. The% elongation at 10% burst strength can range from about 0.18 to about 0.26, and particularly greater than 0.2. % Elongation is measured on a cord taken from a vulcanized tire. The% elongation at 10% breaking load for a green, bare cord may range from about 0.2 to about 0.27%.

Belt 42 is the second element of the operating belt pair. Belt 42 is less than that width of belt 41 (the other operating belt), and is preferably radially outward of belt 41. Preferably, belt 42 is less than the width of belt 41 by a degree. which can range from about 10 to about 20 mm. The belt 42 has a damping angle between about 16 and 30 degrees, preferably with a right orientation, particularly in the range of about 19 to about 25 degrees. Belt 42 is preferably made of the same wire as belt 41 having the same construction with the same opposite angular orientation as 41.

The belt structure 40 further comprises a zigzag belt structure 39, which is preferably located radially into both operating belts 41, 42. Zigzag belt 39 may be formed from the use of either zigzag pattern. described below. Preferably, the zigzag belt structure is 0.5 zigzag wave per revolution of the drum or 1 zigzag wave per revolution of the drum. The drum width of the zigzag belt is preferably in the range of about 70% to about 80% of the tread arch width, and particularly in the range of 73 - 77%. The zigzag belt 39 may be steel, formed into a high elongation construction, such as, for example, 3x7x.22HE, and having an EPC of about 5.5 (EPI of about 14). High elongation wire may have a% elongation at 10% of the breaking load, ranging from about 1.7 - 2.05% for a bare green cord. High elongation wire may have a% elongation at 10% of the rupture load, ranging from about 0.45-0.68% taken from the cured tire. Another example of a bead construction suitable for the invention is made of steel having a 4x7x.26HE construction having EPC DE 7.1 (EPI of 18).

Alternatively, the zigzag belt may be non-metallic. An example of a non-metallic bead that can be used is aramid having a 1670/3 construction having an EPC (ends per centimeter) density of 9.4 (EPI - ends per inch) of 24). The aramid may also have a 3300/3 EPC construction of 9.4 (EPI of 24). The% elongation may also have a 3300/3 EPC construction of 9.4 (EPI of 24). The% elongation at 10% of the breaking load for a bare cord and; typically 0.98%.

It is preferred that the zigzag belt be formed of a cord having a stiffness or sturdiness as defined below. The stiffness is analogous to a spring having an equation F = KX, where F is the force per unit of the transverse width of the strip (N / inch); K is the stiffness of the transverse width force divided by the% elongation in the longitudinal direction, N / cm (N / inch), and X is the relative elongation% in the longitudinal direction. Of this, in a representation of the force / transversal width vs. % relative elongation, stiffness will be equal to the slope of the curve. A cross-sectional string (EPI) string and density should be selected, providing a strip stiffness in the range of about 118,110 N / cm (300,000 N / inch) to about 314,960 N / cm (800,000 N / inch) and particularly in the range from about 137,795 N / cm (350,000 N / inch) to about 295,275 N / cm (750,000 N / inch). The properties of the cord described above are measured using a cord taken from a cured tire.

The aspect ratio of the tire described above may vary. The aspect ratio is preferably in the range of from about 50 to about 90. The tire may have a starting ratio in the range of about 70 to about 90, particularly in the range of about 74 to about 86, especially about 78 to 84.

ZIGZAG BELT CONSTRUCTION

Figure 3 illustrates a tire construction drum 48 having axial circumferential edges 44, 45. To form the modified zigzag belt structure 39 notably the tire construction, the tire construction drum is rotated with a rubberized strip 43. The bead is wound around the drum in a generally circumferential direction, alternately extending from one drum edge 44 to another drum edge 45.

Figures 4A and 4B illustrate the tire construction drum, wherein the circumference of the drum is arranged flat, from 0 degree radian (degree) to 2tt radians (360 degree). Figure 4A illustrates a first winding for a first revolution of the zigzag belt drum being formed in the drum. The invention may also be formed into a core or pneumatic, and is not limited to being formed into a drum of a pneumatic construction. For illustrative purposes, the initial starting point 50 will be the intermediate circumferential central plane of the drum at 0 radian, although any starting point may be used. The strip is first angled at an angle to the edge 45 of the pneumatic construction drum. This correlates to a location of about tt / 2 radians to 1 zigzag per revolution. The following description illustrates the model for 1 zigzag wave per revolution, and is not limited to it, since the zigzag wave per revolution may vary as desired. At the edge 45 of the tire construction drum, the strip has a first axial width or amplitude W1, measured from the center or intermediate circumferential plane of the drum. W1 is preferably the maximum axial width located near the edge of the drum. Thereafter, the strip may optionally continue for a distance L in a circumferential direction (0 degrees) at edge 44. As shown in Figure 4C, the strip is preferably U-shaped without sharp angles, and is preferably rayed at the points of trajectory T1 and T2. As shown in Figure 4, the strip is then angled a -a towards the opposite drum edge 44. At about 3/2 tt radian, the strip has a second axial width or amplitude W2, which is measured from the central plane, and it's different from W1. W1 is preferably larger than W2. Thus, the strip does not extend completely to the axial end 44 of the drum. Thereafter, the strip may be optionally oriented in a substantially circumferential (0 degree) direction to a circumferential distance L. Finally, the strip is angled in the direction of the intermediate circumferential central plane to an angle α. The strip reaches the intermediate circumferential central plane at about 2t radians.

The arrangement of the strip for a second winding is shown in Figure 4b. For the sake of clarity, the first winding has been removed. The starting point 50 'of the second winding was axially indexed to a desired degree, depending on the degree of successive gap between desired strips. For illustrative purposes, the second strip winding is set to a strip width so that it abuts the first winding. Starting at 50 ', the strip is first angled at an angle to the edge 45 of the pneumatic construction drum. This correlates with a site of about t / radian to 1 zigzag per revolution. At this location, the strip has an axial width or amplitude W2, measured from the center or circumferential central plane of the drum. Thereafter, the strip may continue optionally at a distance L in a circumferential direction (about 0 degrees) at the edge44. As shown in Figure 4C, the strip is preferably rotated at the edge of the drum without sharp angles, and is preferably streaked at the transition points T1, T2. As shown in Figures 4b and 4C, the strip is then angled from transition point T2 a -a in the opposite direction of the opposite drum 44. At about 3/2 radian, the strip has an axial width or amplitude W1. Thereafter, the strip may be optionally oriented in a circumferential direction (about 0 degrees) to a circumferential distance L. As shown in Figure 4C, the strip is preferably rotated at the drum edge without sharp angles, and preferably is streaked. -da at the transition points T1, T2. Finally, the strip is angled toward the intermediate circumferential central plane at an angle α. The strip reaches the mid-circumferential circumferential central plane at 2rr radians.

Thus, in a first strip winding, the strip is traversed from the point divided to a first amplitude W1, then to a second amplitude W2, and then back to the starting point. W1 and W2 are in opposite directions from the central plane, eWW W2, and preferably W1> W2. Then in a second strip winding, the strip traverses a starting point indexed to a first amplitude W2, then a second amplitude W1, and then back to the starting point. Thus, the tirase windings abut but can also be overlapped or spaced apart. The strip may also be circumferentially displaced at the edges, either alone or in combination with the variable amplitude zigzag pattern.

A second embodiment of the invention is as described above, except for the differences presented below. If there are no N revolutions required to form the zigzag belt structure, after the first N / 2 revolutions, each zigzag winding has a W1 - W2 model. For the second half (N / 2) of the revolutions, each zigzag winding has a model W2 - W1, where W1 and W2 extend opposite directions of the central plane, and W1 * W2. Preferably W1> W2.

A third embodiment of the invention will be described below. Figure 5A illustrates a first strip winding having a first amplitude W1, followed by a second amplitude W2 in the opposite direction. Figure 5B illustrates a second strip winding, wherein the strip has a first amplitude W2, followed by a second amplitude W1 in the opposite direction. The second winding has been indexed at a desired distance from the first winding, and thus can lean (as shown), overlap or be spaced from it.

Figure 5C illustrates a third strip winding, wherein the strip winding has been moved or circumferentially displaced from the two previous strip windings, so that the turn on the edge is offset from the edges of the previous windings. Just after dolocal tt / 2, at a displacement distance C, the strip had an amplitude W1, and an amplitude W2 just after location 3tt / 2. Figure 5D illustrates a fourth strip winding, the strip is also circumferentially displaced from the first and second windings to reduce the gauge of the belt strip at the outer belt edge. As shown, right after dolocal tt / 2, at a travel distance D, the strip has a first amplitude W2, and a second amplitude W1 at a travel distance D. The travel distance D is different from the travel distance C. Preferably , the travel distance D is less than the travel distance C. To form the complete zigzag belt layer, the sequence as described is repeated until the belt layer is formed.

Figure 6 illustrates a belt revolution zigzag wave in the area near the belt edge having multiple layers or strips. Figure 7 illustrates the cross-sectional views of the belt edge taken at various locations A - A by E - E. As shown, the degree of strip overlap ranges from about one layer to a maximum of 4 layers at the top. section C - C. Figure 8 illustrates the prior art zigzag belt arrangement in which there are up to 6 layers overlapping each other. Thus, the resulting configuration of the present invention has reduced the number of overlapping layers, which is believed to reduce the durability of the tire.

The strip is formed of a rubberized ribbon of one or more strands. The width of the strip may vary, and may be, for example, from a width of about 5-14 mm, and particularly about 10-13 mm wide. Cord reinforcements can be formed of nylon, polyester, aramid or steel. All of the above exemplary embodiments have been illustrated with 1 zigzag wave per 1 drum revolution. The invention may also include N zigzag waves per 1 drum revolution, where N is 0.25 or greater. N may also be an integer> 1. For example, the strip may be arranged so that an integral zigzag wave occurs in 2 integral drum revolutions or 1/2 zigzag per revolution. The invention, as described above, can also keep gaps in contact, thus there is no gap in the consecutive winding spacing. Alternatively, successive strip winding may be overlapped from about 1% to about 100% of the width of the strip. Alternatively, the successive strip winding may have a gap distance G formed between them. G may range from about 1% to about 100% of the width of the strip.

Another variable that can be used is drum displacement, which is best shown in Figure 4c. Drum displacement is the circumferential distance of the drum (measured in degrees or radians) from the edge of the strip to point Y to point X. In other words, the displacement of the drum is half the circumferential distance by which the strip makes one turn. in U, measured from the point Y closest to the edge, to the point X at which the lap is completed. Drum travel or lap distance may be varied, effectively extending the rim in the circumferential direction if increased, or resulting in a sharper lap angle. For example, the displacement of the drum may range from about 5 degrees to about 30 degrees, and particularly from about 10 to about 16 degrees. As the displacement of the drum increases, the angle of the strip a also increases. Figures 9A - 9C illustrate a strip arranged on the drum in a 1 zigzag per dotambor revolution. Figure 9A illustrates a 6.75 degree drum displacement, resulting in a 6.65 degree steel. Figure 9B illustrates a drum shift of 13.5 degrees, resulting in a 7.22 degree adjustment. Figure 9C illustrates a 27 degree drum shift, resulting in an 8.76 degree barrel. As can be seen from a review of all figures, as the displacement of the drum is increased, the angle of one revolution extends along the edge and results in a more homogeneous step. Increased drum displacement also results in a slightly higher one. As the dotambor offset is increased, the degree of overlap of the strip layers increases from 2.83 in Figure 9A to 3.87 in Figure 9B, and above 6 in Figure 9C.

Another variable that can be used is transverse displacement. Transverse displacement is the axial distance from the belt edge from the drum edge, in mm. As the transverse displacement increases, the strip begins to rotate earlier, and irregular belt edges may result, as shown in the Figures. 10A and 10B, as compared to Figures 9A and 9B. Figures 10A - 10C illustrate an 8mm transverse displacement. Figure 10A illustrates a drum displacement of 6.75 degrees, resulting in one at 5.96 degrees. Figure 10B illustrates a displacement distance of 13.5 degrees, resulting in a to 6.48 degrees. Figure 10C illustrates a displacement distance of 27 degrees, resulting in an a of 7.18 degrees. The diminishing effect of transverse displacement results in a belt with more uniform or homogeneous edges and a slight circumferential angle reduction in the strap.

Variations in the present invention are possible in light of their description provided herein. Although certain embodiments and representative details have been shown for the purpose of illustrating the present invention. It will be apparent to those skilled in the art that various changes and modifications may be made thereto without departing from the scope of the present invention. It is to be understood, therefore, that variations may be made in the particular embodiments described, which will be within the intended scope of the invention as defined by the following claims.

Claims (10)

1. pneumatic, CHARACTERIZED, a carcass and a belt structure interposed between the carcass and the tread, wherein the belt structure includes a pair of operating belts, where the angle of the operating belts ranges from about 15 degrees to about 30 degrees, wherein the belt structure further includes a zigzag belt structure located radially into the operating belts, the zigzag belt structure is formed of at least two layers of strands , woven together from a rubber band reinforced with one or more cords, wherein the strip forming the zigzag belt structure is disposed in a first zigzag winding, extending from a first side belt edge to a second side belt edge at a zigzag length having a first amplitude W1, followed by a second amplitude W2, in the opposite direction to said first amplitude, wherein the strip forming the zigzag belt structure is arranged in a second zigzag winding, extending from a first side belt edge to a second side belt edge, at a zigzag wave length having a first amplitude W2, followed by a second amplitude W1, in the opposite direction to said first amplitude. Pneumatic according to claim 1, characterized in that each of said first and second zigzag windings has turns on the first and second side edges, wherein the strip on each edge is extended in a circumferential direction. for a distance L. Pneumatic according to Claim 1, characterized in that the zigzag belt structure has a first belt edge in a first winding and a second belt edge in a second winding, wherein the intermediate point of the first belt. belt edge is offset circumferentially from the intermediate point of the second belt edge. Pneumatic according to claim 1, characterized in that the radially internal operating belt is the widest belt of the belt reinforcement structure. Pneumatic according to claim 1, characterized in that the zigzag belt has a width in the range of about 0.5 to about 0.75 * width of the tread arch. Pneumatic according to claim 1, characterized in that the zigzag belt is formed of a cord having a% elongation at 10% breaking load of more than 0.45% when taken from the a cured tire. 7. Pneumatic, CHARACTERIZED, a carcass and a belt structure interposed between the carcass and the tread, wherein the belt structure includes a pair of operating belts, where the angle of the operating belts ranges from about 15 degrees to about 30 degrees, wherein the belt structure further includes a zigzag belt structure located radially into the operating belts, wherein the zigzag belt structure is formed of at least two layers. of strands woven together from a reinforced rubber strip with one or more strands, and wherein the zigzag belt structure is a first zigzag winding having a first amplitude WMax at a first side end and a second amplitude Wmin at a second lateral end, and WMax is greater than Wmin, and a second zigzag winding tends to have a first WMin amplitude at a first end and a second Wmax amplifier at a second lateral end, and wherein the second zigzag winding is located adjacent said first zigzag winding. Pneumatic according to Claim 7, characterized in that the zigzag belt structure further includes a third zigzag winding having a first amplitude WMax at a first lateral end and a second amplitude Wmin at a second side end, wherein the first and second side ends of the third windings are circumferentially displaced from the first and second side ends of the first zigzag winding and the second zigzag winding, respectively. Pneumatic according to claim 7, characterized in that the zigzag belt structure further includes a fourth zigzag winding having a first amplitude WMin at a first lateral end and a second amplitude Wmax at a second side end, wherein the first and second side ends of the fourth zigzag windings are circumferentially displaced from the first and second side ends of the first zigzag and second zigzag windings, respectively. Pneumatic according to claim 7, characterized in that the zigzag belt has a width in the range of about 0.5 to about 0.75 * width of the tread arch.