MXPA97002025A - An agricated pneumatic rim - Google Patents

Abstract

An agricultural pneumatic tire 20 has a bearing band 32 having a plurality of central projections 50 disposed in a circumferentially continuous row and extending through the equatorial plane. Each central projection 50 is similar but is oppositely oriented relative to each circumferentially adjacent central projection 50. Each central projection 50 has a circumferentially extending front end portion 51 and a circumferentially extending rear end portion 53. The front and rear end portions 51, 53 are positioned on opposite sides of the equatorial plane. The end portions 51, 53 being connected by a mean inclined portion 55, the middle inclined portion 55 being oriented at an angle 0 of 50 ° or less relative to the equatorial plane. This central projection 50 in combination with pluralities of first and second shoulder projections 40, 42 provides excellent traction.

Description

AN AGRICULTURAL PNEUMATIC RIM BACKGROUND OF THE INVENTION This invention relates to an agricultural pneumatic tire for the drive shaft of a tractor or similar vehicle. Farm tires for the drive shaft of a tractor have a primary function of providing tremendous drag on the ground. To achieve this task, the tread patterns are very open with elongated, widely circumferentially spaced traction elements commonly referred to as projections or rods. Mof these tires use what are called "long bars". These protrusions extend from the tread shoulders axially inward and some or all of the projections cross-the center line of the tread. These projections or bars commonly have an enlarged projection head in the innermaxial portion of the projection. These tires are in the prior art in U.S. Patents 3,603,370, 4383,567 and 4,534,392. The primary limitation of these tires was related to the limited amount of protruding edges or surfaces that could be provided for traction. To increase this particularity, the inventor mentioned in this patent previously developed a tire commonly sold as the Goodyear DT720 rim. This tire is described in U.S. Patent 5,046,541. The tire used four rows of relatively short bars. This increased number of bars provided much more mordant edges for traction and as a result - it has demonstrated significantly superior traction. Some farmers, however, are not willing to believe that short bars can be so effective in very wet conditions that they can tend to fill the tires with mud. Even though the DT710 wheels work very well in these conditions, the inventor has tried to achieve a tractor tire that has a combination of long bars and short bars with excellent traction performance, riding handling and operation and superior band cleaning properties. of bearing in wet muddy soil conditions. To achieve this result, the inventor has designed a tractor bearing band 32 -one having a continuously continuous row of 50 alternating central headers that cross at the center of the tread band 32. The rim 20 of the present invention has a very durable design that is believed to be capable of excellent performance in very wet and very dry land conditions. This multi-purpose capability, coupled with the specifics of safe on-the-road riding, means that a farmer can rely on a set of these tires that will fill the full range of farm conditions. Currently, farmers must store a variety of special application tires such as rice, sugarcane and the like in addition to conventional tires. This rim 20 of the invention can make this practice obsolete in many cases and, therefore, will provide a good csavings for many farmers.

SUMMARY OF THE INVENTION An agricultural pneumatic tire 20 for the drive shaft of a tractor or similar vehicle has a width (W) of maximum section, an axis of rotation, an equatorial plane, the equatorial plan being centered between the section width maximum and being perpendicular to the axis, a housing having a frame 21 reinforced with rubber-coated cords, a rubber bearing strip 32 disposed radiating outwardly from the zon 21 weapon. The bearing band 32 is divided on each side-of the plane equatorial to first and second half 32A and 32B of tread. The tread band 32 has an inner bearing strip 34 and a plurality of tread projections 40, 42 50. The tread has a pair of lateral tread edges 33A and 33B, the distance between the side tread edges defines the tread width T. A plurality of central projections 50 are arranged in a row 60 with continuous circumference and extend through the equatorial plane. Each central projection 50 is similar in appearance but is oppositely oriented relative to each circumferentially adjacent central projection 50. Each central projection 50 has a front end portion 51 which extends substantially circumferentially and a rear end portion 53 extending substantially circumferentially. The front and rear end portions 51, 53 of each central projection 50 are positioned on opposite sides of the equatorial plane. additionally, the tread band 32 has a plurality of first shoulder protrusions 40 projecting radially outwardly from the inner tread surface 34 and extending from the lateral edge 33A, 33B toward the equatorial plane of the tire. The first shoulder -40 protrusions have an axially inner end 41 disposed -circumferentially between a leading end 51 and a rear end -53 of the circumferentially adjacent central projections 50. The first shoulder projections 40 extend from each side edge 33A, 33B and are similar in appearance and configuration, but are circumferentially offset and opposite in orientation relative to the first shoulders 40 of the shoulder extending from an edge 33A or 33B of opposite tire band. Each of the first shoulder projections 40 is collocated within a tread half 32A or 32B.

The bearing band 32 further has a plurality of second shoulder projections 42 projecting radially from the inner bearing band 34. The second shoulder projections 42 extend from each edge 33A or 33B of the lateral tread band. These projections 42 are similar in appearance, but are circumferentially biased and opposed in relation to projections 42 extending from an opposite lateral edge 33A or 33B. Each second shoulder projection 42 is within a tread half 32A or 32B and is circumferentially positioned between a pair of shoulder protrusions 40 within the tread half 32A 32B from which it is positioned. These second shoulder projections 42 have an axially internal extrusion 44, circumferentially aligned with a rear end portion 53 of a centrical projection 50 placed on an opposite tread half 32A or 32B. Each first projection 50, 40, 42 of central shoulder, and second of shoulder has a radially outer surface 58, 48, 47. The minimum distance between the surfaces 58, 48, 47 d of the projections 50, 40, 42 is greater than 175% of the average width (W) of the projections as measured on the respective external radial surfaces. The tread band 32 has a net to br to less ratio of 255 as measured around the full circumference of 360Q of a normally inflated and normally loaded rim 20 contacting a hard, flat surface. The central projections 50 each have an elongated half portion. The projection 50 has a pair of projection edges 52, 54, a leading edge 52 and a trailing edge 54. A line 63 centered between the leading edge and the rear edge on the surface of the middle portion 55 defines the center line 63B of the center exit, the center line 63B is inclined at an angle? Included with the equatorial plane of the rod band, the angle 0 is less than 50 °, preferably approximately 45 °. The leading and trailing ends 51, 53 of the central projection 50 each preferably have a length of about 20 °. 20% or more of length 1 of total projection. The middle portion has a length of about 30% or more of the total protruding length 1. The forward and rearward projections 51, 53 each have a central line 63A and 63C extending substantially circumferentially at a beta angle with reference to the equatorial plane of the beta angle approximately 30Q or preference of less than 305. The combination of the central projections 50 and the first and second shoulder projections 40, 42 provide exceptionally good traction performance and a very smooth low-vibration travel on road surfaces. The protruding arrangement creates large earth discharge channels 36 which pan out volumetrically as they progress laterally outwardly from the center of the tread pattern, this feature greatly enhances the self-cleaning properties of this tread pattern.

Definitions "Relationship between Dimensions" means the ratio of its section height to its section width. "Axial" and "axially" means the lines or directions that are parallel to the axis of rotation of the rim. "Heel" or "Heel Core" generally means here that part of the rim comprising a tension member voids the internal radiating beads are associated with the retention of the rim to the rim wheel which is being wrapped by layer cords and configuring, with or without other reinforcement elements such as legs, splinters, apices or fillings, tip protections and bevels, the heel or beads under the tread being encapsulated in tread rubber can be with or without Other elements of cloth reinforced with cue da. "Band Structure" or "Reinforcement Bands" means at least two layers of parallel strings, woven or nonwoven that remain under the tread, not anchored to the heel and that have both left and right rope angles in the cove from 17Q to 27Q with respect to the equatorial plane of the rim. "Deviated Layer Tire" means that the reinforcing cords in the frame layer extend diagonally through the bead-to-bead rim at an angle of approximately 25-75 Q with respect to the equatorial plane of the rim, the cords of current layer at opposite angles in alternating layers. "frame" means a laminate of rim layer material and other rim components cut to appropriate length for splicing, or already spliced, into a cylindrical or toroidal configuration. Additional components can be added to the frame before it is vulcanized to create the modified tire. "Circumferential" means lines or directions that extend along the perimeter of the surface of the annular tread, perpendicular to the axial direction. "Design Wheel Wheel" means a wheel of 11 a-ta that has a specified configuration and width. For the purposes of this specification, the design rim wheel and wheel width of the design rim are as specified by industry standards in effect at the location where the rim is made. For example, in the United States, the design tire wheels are as specified by the Tire an Rim Association. In Europe, rim wheels are as specified in the European Tire and Rim Technical Organization - Standars Manual and the term tire rim wheel means the same as conventional rim wheels. In Japan, the conventional organization is The Japan Automobile Tire Manufacture to Association. "Wheel Rim Design Wheel" is the coemrci rim width available, specific, assigned to. Each tire size and typically is between 75% and 90% of the specific tire section width. "Equatorial plane (EP)" means the plane perpendicular to the axis of the rotation rim and passing through the center-of its tread. "Footprint" means the patch or contact area of the touch pad of the tire tread with a flat surface at zero velocity and under normal load and pressure. "Internal" means to the inside of the tire and "external" means to the outside. "Lateral Edge" means the axially most extejr edge of the tread as defined by a plane parallel to the equatorial plane and intersecting the outer ends of the axially most external traction protrusions at the radial height of the tread surface. internal bearing "Front" refers to a portion or portion of the tread that contacts the ground first, with respect to a series of said portions or portions, during the rotation of the rim in the direction of travel. "Net-to-gross ratio" means the ratio of the surface of the normally loaded and normally inflated tire rim rubber to contacting a hard, flat surface divided by the total area of the rim band, including portions that do not make contact such as grooves, as measured around the full circumference of the 11th. "Normal Inflation Pressure" means the specific design inflation pressure and load assigned by the standards organization ap ried to the service condition for the tire. "Normal Load" means the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire. "Radial" and "radially" mean directions radially toward or away from the axis of rotation of the rim. "Radial Layer Tire" means a pneumatic tire with bands or circumferentially restricted in which the layer cords extending from bead to heel are stretched to rope angles between 659 and 909 with respect to the equatorial plane of the tire. "Section height" (SH) means the radial distance from the nominal rim wheel diameter to the outer diameter of the rim on its equatorial flange. "Section width" (SM) means the maximum linear distance, parallel to the axis of the rim and between the outside of its side walls when and after it has been inflated at normal pressure for 24 hours, but discharged, including the elevations of the side walls due to labeling, decoration or bands protective. "Rim Design Load" is the base or reference load assigned to the tire at a specific inflation pressure and service condition; Other load-pressure ratios api ic_ables to the rim are based on that base or reference. "Rear" refers to a portion or part of the tread that makes contact with the ground at the end, with respect to a series of said parts or porcine during the rotation of the rim in the direction of travel. "Bearing Band Arc Width" (TAW) s ign i fJ_ ca the width of an arc that has its center placed in the plane (EP) and that substantially coincides with the radially outermost surfaces of the various elements of traction (ridges, blocks, buttons, ribs, etc.) through the width - lateral or axial of the tread portions of a rim when the rim is mounted on its designated rim wheel and inflated to its tire pressure. inflated specific, but not subject to any load. "Bearing Band Width" means the arc length of the tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire. "Unitary Bearing Band Pressure" means the radial load carried per unit area (square centimeter or square inch) of the bearing surface when that area is in the tire tread normally inflated and normally loaded.

BRIEF DESCRIPTION OF THE DRAWINGS The following is a brief description of the drawings - in which the like parts bear like reference numbers and in which: Figure 1 is a perspective view of the preferred embodiment rim according to the invention . Figure 2 is a plan view of the rim of Figure 1. Figure 3 is an enlarged fragmentary view of a portion of the tread of the rim, taken from 1 to Figure 2. Figure 4 is a cross-sectional view of the rim, taken along lines 4-4 of Figure 2. Figure 5 is a plan view of a portion of the preferred rim contact patch in accordance with the present invention. .

Detailed Description of the Invention Referring now to Figure 4, a rim is shown in cross-sectional view generally as a reference number 20. The pneumatic rim has a frame 21 having one or more frame layers 22 extending circumferentially. - essentially around Rotation axis of the rim 20. The frame layers are anchored around a pair of substantially inextensible annular beads 24. A band reinforcement member 26 which commpenses one or more band layer 28 is disposed radially outwardly from the frame layers. The band layers provide reinforcement for the rim region of the rim. A circumferentially extending rolling band 32 is collided radially outwardly from the band re-structuring structure 26. A sidewall portion 33 extends radially inwardly from each edge 33A, 33B of the axial or lateral tread of the tread to an annular shoulder portion 35 having heels 24 positioned therein. The frame layers 22 preferably have textile or synthetic cords that reinforce the layers. The cords are preferably oriented radially. More preferably, the cords are made of polyester or nylon material. Typically the rim can have two, three or four layers, each construction increasing in load bearing capacity as a function of the number of layers. the band reinforcement member 26 preferably includes at least two reinforced bands of synthetic piles, nylon, rayon or aramid. Referring now to Figures 1-5, a tire 20 in accordance with the present invention is illustrated. The belt 20 according to the present invention has a single bearing band 32. The tread band 32 has a first rim tape 33A edge and a second tread edge 33B. Arranged between the bands 33A, 33B of the rolling band is an inner rolling band 34 and a plurality of central splines 50 extending radially outwardly from the inner rolling band 34. as illustrated in Figure 2, each cental projection 50 has a radially external surface 58, a first leading edge 52, a second trailing edge 54, and a central line 63 between the first and second edges. Each central projection 50 extends generally circumferentially from a forward end 51 to a rear end 53. As illustrated in Figure 5, the radically outer surface 58 when viewed from the contact patch has a polygon configuration. The surface 58 when divided into portions, each encompassed by a substantially rectangular portion 65A, 65B and 65c, exhibits the approximate orientation of the central projection 50, for purposes of this invention, the central lines 63A, 63B and 63C of the projection 50. they are approximated by a line intersecting the middle through, thus bisecting, the short legs of the rectangle, the line extending parallel to the long legs of the substantially rectilinear portions 65A, 65B and 65C. It is important to note that each of the protrusions has a length (I,) at least three times the average width of the element, while the block elements have an average width greater than one third of the length of the element. A projection for purposes of this invention has a length of at least 10% of the section width of the spout, preferably the protrusion length as measured along the protrusion centerline must be more than 25% the total tread width TW, more preferably, at least 30% of the total tread width TW. The average distance along the center lines 63 between the front and rear ends 51, 53 defines the entire length of the length (1,) of the central projection 50. The distance extending substantially perpendicularly between the first and second edges 52, 54 of the central projection defines the width (1) of projection. The radial distance extending between the inner bearing strip 34 and the edges 52, 54 of the slat 50 defines the height (1.) of the radial projection. The ratio of the width (1 W) of projection to the radial height (lh) is less than two thirds on at least 70% of the length (1,) of projection for the shoulders. The central projections 50 are arranged in a circumferentially repeating row 60 of projections 50, each segment 50 extending from its respective band edge 33A, 33B across the equatorial plane. The circumferentially adjacent central projections 50 are oriented in a similar but opposite way. Each projection 50 is preferably equally spaced from each of the respective bearing band halves 32A or 32B. The forward ends 51, as shown, intersect the equatorial plane, with each central projection 50 having a majority of its forward end portion 51 on an opposite tread half relative to the circumferentially adjacent central projection. Similarly, the rear end portions 53 are also positioned in opposite tread halves relative to the forward end 51 of the nose itself and in a tread half of the bearing relative to the rear end portions 51 of the tires. projections 50 circumferentially adjacent centrals. In order to maintain the handling operation of the rim, having 50 alternating central outlets in the center requires special attention to the design of the central projection. The central projections 50 arranged as illustrated, create the effect of a common central rib on tractor tires that must be handled on road surfaces. Unusually the open space S is interrupted between the central projections 50. The almost circumferential bearing of the front and rear end projections 51, 53 allows the web band projections 50 to penetrate even hard or compacted soil. Unlike most tractor ribs that prevent the tread from engaging with the ground, these central ledges 50 uniquely oriented to be narrow in width and broadly spaced at a distance S from at least 175% of the protrusion width as measured on the surface 58, allows the 11th anchor to be buried towards the ground greatly improving the tensile functions. The travel operation and traction capability are further enhanced by employing a plurality of first shoulders 40 extending from each bo of respective tread 33A or 33b and remaining fully within a 32A or 32B half. of rodmaiento band. The first shoulder lugs 40 are relatively short in length having a length 1, total equal to or less than the total length lj of the central projection 50. The first shoulder projection 40 has an axially internal end 41 that is The corked portion is mutually co-ordinated between the front end portion 51 and the rear end portion 53 of the circumferentially adjacent center projections 50. Interposed between each pair of first shoulder projections 40 is a second shoulder projection 42. The second shoulder projection 42 is preferably substantially longer in total length than either the center projection 50 or the first shoulder 40. The second long shoulder projection 42 extends from a bearing band edge 33A or 33b toward the center of the bearing band 32. It lies entirely within a tread half 32A or 32B and has an axially inner end 44 circumferentially aligned with a rear end portion 53 of a central saver 50, the rear end portion 53 being in an opposite tread half 32A or 32B relative to the second shoulder projection 42. As shown in Figure 5, both the first shoulder 40 and the second shoulder 42 have preferably a composite inclination, the alpha, axially internal inclination being approximately 45Q relative to the equatorial plane, while the inclination Axial axial external is approximately 60Q in relation to the equatorial plane. A very important feature of the rolling band 32 is the number of central projections 50 relative to the number of shoulder projections 40, 42. There is only one central outlet 50 for every two sash sails. This two-to-one relationship of shoulder protrusions to central protrusions creates a more open tread pattern providing a very low net-to-gross ratio. The DT710 rim of the prior art mentioned above had a one-to-one ratio of crescent projections to shoulder projections, thus providing a more densely packed central area or regiment of the tread which has been suspected by some. which is susceptible to low tread cleaning in very wet, muddy solid conditions. This bearing band 32 of the invention, however, is perceived to be superior under these more severe conditions. As shown further in Figure 5, the center array has a middle portion having a central line 63B between the leading and trailing edges 52, 54. The central line 63B is oriented at an angle? less than 50Q, preferably less than 459 relative to the equatorial plane. Similarly, the front and rear end portions 51, 53 are similarly inclined, the respective central lines 63A, 63B being inclined at a beta, beta angle approximately 309 or less with r alion to the equatorial plane, preferably 309 or less. As shown in Figure 5, the net to gross ratio of the tread is less than 25%. The space between the projections creates large earth discharge channels 36. These channels 36 increase in volume as they extend from the center of the tread to the bearing shoulders. This particularity of increasing volume allows the earth to flow out when operating in very humid conditions. The open quality of the tread pattern also improves the self-cleaning properties of the rolling belt, preventing it from packing with mud. It is understood that the overall configuration of the projections can be varied and the general orientation or appearance of the projections can be modified without abandoning the spirit of the claimed invention which is directed to the novel tread pattern described herein. . A very important aspect of the rim of the invention relates to the axial width 70 of the circumferentially continuous row 60 of central projections 50. The full axial extension 70 as measured from the platen contact patch shown in Figure 5 is only about 33% of the total tread width TW. The first shoulder projections extend axially inwardly at a distance 71 from only about 305 of the tread width from their respective tread edge. The second shoulder protrusions being longer extend axially from one tread edge to an axially more internal location 72 of 40% of the tread width. Consequently, only the second shoulder projections axially are fractionally aligned with a portion p of the rear end portion 53 of the shoulder projections 50 remaining on the same lap band half 32A or 32B. On a 18.4R42 tire made in accordance with the invention, the TW width of the tread was 44.30 centimeters and the tread had a net to gross ratio of 21%. The axial width 70 of the die 60 was 14.81 centimers or 33% TW. The axial extension 71 of the first shoulder -40 of the shoulder was 12.83 centimeters or TW of 29%. The axial extension 72 of the second shoulder projection 42 was 17.86 centimers or 40.3% TW. The projecting lengths were 16.26 centimeters for the central overhang, 37% of TW, 15.49 centimeters, 35% of TW for the first shoulder 40, and 21.84 centimeters or 49% of TW for the second shoulder 42. The central projection 50 had a front end portion 51 of a length measured along the center line 63A adjusted to 5.84 centimeters or 36% of the total length of the first line, the average portion of a length of 5.08. centimeter or 31% of the total projection length and the 55 rear end portion of a length of 5.44 centimeters or 33% of the total projection length. The 0 and beta angles were 45Q and 309 respectively for the central projection. The alpha and alpha angles for the first 40 and 42 and second angles of the shoulder were the same, alpha "being 56.5Q and 45.4Q relative to the equatorial plane. The protruding angled LW for the central projection 50 was 3.81 cemeterimeters while the projection width for the first and second abutment projections was approximately 3.56 centimers. The central projection 50 had a protrusion height set at a conventional R-1 tractor nose height as specified in the Tire and Rim Association Standards, that dimension being approximately 4.09 centimeters for the exemplary rim as shown in FIG. measured in the equatorial plane. As can be seen, the preferred tread 32 had the adjacent earth discharge channels 36 of unequal width and spacing. This particularity, even when it is beneficial for traveling operation was not a design particularity. It is believed that equal spacing would work as well, it being understood that the -70 channels should not decrease as they extend axially outward.

Claims (11)

CLAIMS:

1. - A pneumatic tire for a tractor or similar vehicle that has a width (W) of maximum section, an axis of rotation, an equatorial plane. centered between the maximum section and which is perpendicular to the axis, a housing having a frame reinforced with rubber-coated cords, a rubber tread band disposed radially outwardly of the frame, the tread being divided on each side of the píate non-equatorial to first and second half of tread, the tread has a pair of side tread edges, the distance between the edges of the tread-band defines the tread width, the tread having an internal tread and a plurality of tread projections projecting radially from the internal rolling belt, the tread band is characterized by: a plurality of central projections disposed in a circumferentially continuous row and extending to through-from the equatorial plane, each central projection being similar but oppositely oriented with relation to each circumferentially adjacent central projection, each central projection having a front end portion extending substantially circumferentially and a rear end portion extending substantially circumferentially, the front end portion of each central projection being placed on an opposite side of the equatorial plane relative to the rear portion of the same central projection. 2.- The pneumatic tire grinder of claim 1, the tread further characterized by: a plurality of first shoulder protrusions projecting radially outwardly from the tread-inner and extending from the band edges of lateral bearing towards the equatorial plane of the rim, the first shoulder projections having an axially internal end and being circumferentially positioned between a leading end and a rear end of the circumferentially adjacent central projections, the first shoulder protrusions extending from each lateral edge being similar in configuration but -as opposed in orientation with respect to the first shoulder protrusions extending from an opposite shoulder edge, each first shoulder protrusion being placed within one half of the shoulder band. tread. 3.- The agricultural pneumatic tire of the claim 2, the tread further characterized by: a plurality of second shoulder projections projecting radially from the inner tread, the second shoulder projections extend from each side bearing-band edge, the second shoulder projections shoulder -from each side tread edge being similar but oppositely oriented relative to the second shoulder projections extending from the opposite side edge, each second shoulder is completely within a tread half and is circumferentially placed between a pair of first shoulder protrusions within the half of the tread from which it is placed. 4. The agricultural pneumatic tire of claim 1, further characterized in that each of the second shoulder projection has an axially inner end circumferentially aligned with a rear end portion of a central seat placed in a half of opposite tread 5.- The pneumatic tire, agricultural of the reivindicació 4, further characterized in that each central projection, of the first spade and second spade has a radially eternal surface, and the minimum distance, between the surfaces of the spans is greater than 175% of the average width of the spans. protrusions as measured on the radially external surface. 6.- The pneumatic tire, agricultural of the reivindicació5, further characterized in that the tread has a net-to-gross ratio of less than 25% as measured around the full circumference of 3609 of a normally-inflated and normally loaded rim that makes contact with a hard flat surface . 7. The agricultural pneumatic tire of claim 1, further characterized in that the central projections have an elongated middle portion, the middle portion has a pair of projection edges, a leading edge and a trailing edge, a line centered between the leading and trailing edge on the surface of the middle portion defines the center line of trailing brow protrusion, the center line is inclined at an angle? included in relation to the equatorial plane of the tread, the angle 0 being less than 50Q. 8.- The agricultural pneumatic tire of the claim 7, further characterized in that the front and rear end portions of central projections each have a central line, the respective center lines being extending substantially circumferentially at an angle beta, beta being approximately 305 relative to the plane equatorial. 9.- The agricultural pneumatic tire of the claim 8, further characterized in that the central protrusion has a total protrusion length, as measured along the central lines of front end portions, rear end and m dia, and the middle portion has a length of 30% or more of the total outgoing lojpitude. 10.- The agricultural pneumatic tire of the claim 9, further characterized in that the length of the rear extrusion portion and the length of the front end portion are-each of at least 20% of the total protrusion length. 11.- An agricultural pneumatic tire for a tractor or similar vehicle having a width (W) of maximum section, -a rotation axis, an equatorial plane, centered between the maximum section in its width and being perpendicular to the axis , a housing having a frame reinforced with coated cords - with rubber, a rubber tread band disposed radially outwardly from the frame, the tread being divided on each side of the equatorial plane towards a first and a second half of tread, the tread has a pair of side tread edges, the distance between the tread edges defines the tread width, the tread has an inner tread and a tread plurality of radial band projections projecting radially from the internal tread, the tread being characterized by: a plurality of first passages; blades extending from the lateral edges axially inwardly at a distance of approximately 25% of the tread width a plurality of second shoulder protrusions extending from the lateral edges, axially towards a distance at a distance of about 40% of the rolling bandwidth, a second stiffened shoulder protrusion interposed between each shoulder protrusion; a central projection that crosses the equatorial plane, having a central projection for each two shoulder projections.