Patent Publication Number: US-2021178826-A1

Title: Utility vehicle tyres

Description:
The invention relates to a utility vehicle tyre having a tread with at least one circumferential channel with a channel base and channel walls, wherein base elevations are formed on the channel base in a manner distributed over the circumference and acting centrally as stone ejectors, with a height of 25% to 60% of the profile depth and a greater extent in the circumferential direction than in the axial direction, which base elevations either contact the channel walls or are at distances of up to 4.0 mm therefrom in the axial direction and are bounded in the radial direction by a top surface having an encircling surface edge, wherein the channel walls between the base elevations have wall portions which converge toward each other. 
     A utility vehicle tyre of said type is known for example from JP S6 325 107 A. The tread of said utility vehicle tyre is provided with a central circumferential channel, on the channel base of which base elevations acting as stone ejectors are formed. The base elevations in a plan view are in the form of hexagons elongated in the circumferential direction, and are bounded in the radial direction by flat top surfaces which are oriented substantially parallel to the tread periphery. The base elevations have a width of 25% to 40% of the profile depth in the axial direction and a height of 20% to 60% of the profile depth in the radial direction. Between the base elevations, projections which are trapezoidal in a plan view and which have a height of 20% to 60% of the profile depth in the radial direction are formed on channel walls. 
     U.S. Pat. No. 4,345,632 A discloses a utility vehicle tyre having a tread which has a circumferential channel which runs in a zigzag-shaped manner in a plan view and on the channel base of which base elevations which are spaced apart from the channel walls are formed as stone ejectors. The base elevations have a height of 20% to 60% of the profile depth and a length of, for example, 6.0 mm in the circumferential direction. 
     DE 37 27 050 A1 discloses a further utility vehicle tyre having a tread with a circumferential channel which runs in a zigzag-shaped manner in a plan view with base elevations acting as stone ejectors on the channel base. The base elevations have, for example, an extent length of 4.0 mm in the circumferential direction. Further base elevations of web-like configuration run between said base elevations. 
     The base elevations which are known from the prior art and act as stone ejectors have configurations and dimensions which have proven not very suitable for reliably ejecting relatively large stones because of a lack of stability. The stones consequently jammed in the channels can cause undesirable damage to the channel walls and the stone ejectors. 
     The invention is therefore based on the object, in a utility vehicle tyre of the type mentioned at the beginning, of improving the effectiveness of the base elevations acting as stone ejectors to reliably eject relatively large stones. 
     The stated object is achieved according to the invention in that the top surface of the base elevations slopes downward uniformly toward the surface edge, wherein the channel walls have, to the side of the base elevations, wall sections which are convexly curved toward one another in a plan view, and wherein the surface edge of the top surface follows the profile of the wall sections which are convexly curved toward one another, such that the width of the base elevations decreases toward those ends thereof which lie in the circumferential direction. 
     In the invention, the stone ejectors are components of a channel concept or are coordinated with the configuration of the channel walls. The adaptation of the configuration of the base elevations to the wall sections of the channel walls, which wall sections are curved convexly toward one another, particularly significantly increases the stability of the base elevations and thereby the capability thereof of being able to effectively eject even relatively large stones. The top surfaces of the base elevations sloping down toward the channel base “distribute” the forces acting on the base elevations from the trapped stones, and thereby reduce the risk of jamming of the stones and protect the base elevations and also the channel walls and the channel base from damage due to stones penetrating the channel. In addition, the curved wall sections of the channel walls have a supporting, stabilizing effect on the channel walls in the region of the base elevations and also contribute to improving the effect of the base elevations. 
     According to a preferred design variant, the base elevations in a plan view have the form of diamonds which are elongated in the circumferential direction and have rounded corners. Such base elevations interact with the convexly curved wall sections of the channel walls in such a manner that the stone-ejecting effect is additionally improved. The base elevations are furthermore particularly stable because of the diamond shape. 
     According to a preferred design variant, the base elevations are composed of a base part with a height which is constant in the radial direction and of a dome-like upper part placed onto said base part. It is preferred here if the height of the base part of the base elevations is 35% to 90%, in particular 40% to 80%, of the height of the base elevations. Such a base part increases the stability of the base elevation. 
     Furthermore, it is preferred if the top surface of the base elevations has a core top surface and an edge top surface which runs around the latter and slopes downward toward the surface edge of the top surface, in order to avoid jamming of stones. 
     According to a preferred further design variant, the base elevations are bounded exclusively by their top surfaces. The stability of the base elevations can likewise be increased in this manner. Such base elevations are preferably in the form of a hemi-ellipsoid or of a subsection of a hemi-ellipsoid. By means of the completely rounded top surfaces of such ellipsoids, firstly jamming of stones is very effectively prevented and secondly the base elevations are particularly resistant to possible damage due to stones. 
     The channel walls have a particularly pronounced supporting effect if the wall sections of the channel walls, which wall sections are curved convexly toward one other in a plan view, are curved convexly at least over the majority of their radial extent, as viewed in cross section. 
     The base elevations are particularly stable if, according to a further preferred variant, they have in the circumferential direction at their longest point an extent length of 10.0 mm to 35.0 mm, in particular of 15.0 mm to 25.0 mm. Such base elevations are significantly larger and more stable than conventionally designed “stone ejectors”. 
     According to a preferred further design variant, the height of the base elevations amounts to 25% to 60%, in particular 30% to 55%, preferably at most 50%, of the profile depth. This measure likewise contributes to the stability of the base elevations and, in particular via an advantageous interaction with the curved wall sections, improves the stone-ejecting effect. 
     In this connection, it is furthermore of advantage if the base elevations have a width of 5.0 mm to 15.0 mm in the axial direction at their widest point. 
     According to a preferred further variant, it is provided that a channel path of the circumferential channel runs between the wall sections, which converge toward one another between the base elevations, said channel path at its narrowest point having a width of 15% to 45%, in particular of at most 35%, of the width of the circumferential channel at the tread periphery. By means of such channel paths, in particular the water-draining properties in the circumferential channels are advantageously influenced. 
     Furthermore, it is preferred if the wall sections which converge toward one another between the base elevations bound projections which project into the circumferential channel, lie opposite one another in pairs and are in particular of lug-like configuration. Such projections as a component of the channel concept mentioned improve firstly themselves and secondly, by interaction with the base elevations, the stone-ejecting effect. In addition, the projections also have a supporting, stabilizing effect on the channel walls in the region of the base elevations. 
     According to a further preferred design variant, the wall sections which converge toward one another between the base elevations are at a distance of 2.0 mm to 4.0 mm at their radially inner ends. This is of advantage in particular in respect of the water-draining properties of the circumferential channel. 
     According to a further preferred design variant, the channel walls of the circumferential channel are wave-shaped in a plan view and run symmetrically with respect to a plane defined by the circumferential direction and the radial direction. This variant provides a further particularly advantageous channel concept with stone ejectors. 
    
    
     
       Further features, advantages and details of the invention will now be described in more detail on the basis of the drawing, which schematically shows exemplary embodiments of the invention. In the drawing, 
         FIG. 1  shows a plan view of a central circumferential section of a tread of a utility vehicle tyre with a first design variant of the invention, 
         FIG. 2  shows an enlarged plan view of a circumferential section of a circumferential channel of the tread from  FIG. 1 , 
         FIG. 3  shows an oblique view of the circumferential section from  FIG. 2 , 
         FIG. 4  shows a section along the line IV-IV in  FIG. 2 . 
         FIG. 5  shows a section along the line V-V of  FIG. 2 . 
         FIG. 6  shows a section along the line VI-VI in  FIG. 2 , 
         FIG. 7  shows a section along the line VII-VII in  FIG. 2 , 
         FIG. 8  shows a section along the line VIII-VIII in  FIG. 2 , 
         FIG. 9 a    shows a plan view of a circumferential section of a circumferential channel of a tread with a second design variant of the invention, 
         FIG. 9 b    shows an oblique view of the circumferential section from  FIG. 9   a,    
         FIG. 10 a    shows a plan view of a circumferential section of a circumferential channel of a tread with a third design variant of the invention, 
         FIG. 10 b    shows an oblique view of the circumferential section from  FIG. 10 a   , and 
         FIG. 10 c    shows a section along the line Xc-Xc in  FIG. 10   a.    
     
    
    
     Utility vehicle tyres designed according to the invention are tyres of radial design, in particular for construction site vehicles, trucks or buses. 
     The central circumferential section of a tread that is shown in  FIG. 1  has four profile positives  1  which encircle in the circumferential direction, are illustrated schematically and in simplified form and are in particular profile bands or profile block rows realized in a known manner. Profile positives  1  which are adjacent in the axial direction are separated by a respective circumferential channel  2  running rectilinearly in a plan view. 
     In the exemplary embodiment shown, the circumferential channels  2  are designed in a corresponding manner. The configuration of the circumferential channels  2  will be described below with reference to the circumferential channel  2  shown in  FIG. 2  to  FIG. 8 . 
     As  FIG. 2  and  FIG. 3  show, the circumferential channel  2  at the tread periphery is bounded by two channel edges  3 , which run substantially in the circumferential direction and, in the exemplary embodiment shown, have a slightly wave-shaped profile in a plan view, and furthermore by channel walls  4  adjoining the channel edges  3 , and a channel base  5 . The circumferential channel  2 , at its deepest point in the radial direction, has the profile depth T 1  ( FIG. 4 ,  FIG. 8 ) that is provided for the respective utility vehicle tyre of 12.0 mm to 26.0 mm and, at the tread periphery, at its widest point in the axial direction, a width B 1  ( FIG. 8 ) of in particular 10.0 mm to 25.0 mm. According to  FIG. 4  to  FIG. 8 , the channel walls  4 , in the exemplary embodiment shown, have radially outer sections running in the radial direction, as viewed in cross section, between which the circumferential channel  2  likewise has the width B 1 . 
     Each channel wall  4  bounds and forms a multiplicity of flat lug-like projections  6  which follow one another in the circumferential direction and are arranged at regular intervals over the entire extent of the circumferential channel  2 , wherein each projection  6  is bounded by a wall section  4   a  of the respective channel wall  4 . The projections  6  bounded by wall sections  4   a  at the two channel walls  4  lie opposite one another in pairs and are formed symmetrically with respect to a plane which is defined by the circumferential direction and the radial direction and runs through the center of the circumferential channel  2 . 
     Each projection  6  is additionally formed symmetrically with respect to a plane which is defined by the radial direction and the axial direction, runs through the center of the projection  6  and runs along the intersecting line IV-IV shown in  FIG. 2 . The wall sections  4   a  bounding the projections  6  are composed of a slightly outwardly curved central wall region  4   a   I  forming the lug back and two lateral wall regions  4   a   II  which adjoin said central wall region and form the lug wings. The central wall region  4   a   I  of the wall section  4   a  runs in the plane mentioned, which coincides with the intersecting line IV-IV, at an angle α ( FIG. 4 ) of 10° to 30° to the radial direction, as viewed in cross section. The lateral wall regions  4   a   II  of the wall section  4   a  are preferably flat surfaces which are inclined with respect to the circumferential direction ( FIG. 3 ) and, as viewed in cross section, run at an angle β ( FIG. 5 ) of, for example, 5° to 25° to the radial direction, wherein β&lt;α. 
     Wall sections  4   b  which are sickle-shaped in a plan view run between the projections  6  which are formed on the same channel wall  4  and directly follow one another in the circumferential direction. The sickle-shaped wall sections  4   b  belonging to a channel wall  4  are curved convexly in a plan view with respect to the sickle-shaped wall sections  4   b  belonging in each case to the opposite channel wall  4 . In accordance with their sickle shape, the wall sections  4   b  peter out along the lateral wall regions  4   a   II  forming the lug wings. 
     Furthermore, the wall sections  4   b,  as viewed in cross section, are slightly bent, and therefore the wall sections  4   b  belonging to the different channel walls  4  are also curved slightly convexly toward one another in cross section ( FIG. 7 ,  FIG. 8 ). 
     In each intermediate space which is located between opposite wall sections  4   b  that are curved convexly toward one another, a base elevation  7  acting as a stone ejector is formed centrally on the channel base  5  of the circumferential channel  2 . Each base elevation  7  is therefore located between two pairs of opposite projections  6  directly following one another in the circumferential direction. In a plan view, each base elevation  7  is in the form of a diamond which is elongated in the circumferential direction and has rounded corners, in particular substantially in the form of a football. Remaining on the channel base  5  of the circumferential channel  2  is a channel path  2   a  ( FIG. 3 ) which encircles all of the base elevations  7  and, in a plan view, extends substantially along two intersecting shafts which have a coinciding wavelength and are phase-displaced with respect to one another by half of the wavelength in the circumferential direction. 
     The channel path  2   a  has a depth T 2  ( FIG. 4 ) of up to 4.0 mm, in particular of up to 3.0 mm, in the radial direction between the central wall regions  4   a   I  of mutually opposite projections  6 . Furthermore, the channel path  2   a  between said wall regions  4   a   I  has, at its narrowest point in the axial direction, a width B 2  ( FIG. 4 ) of 15% to 45%, in particular of at most 35%, of the width B 1  ( FIG. 8 ) of the circumferential channel  2 . In the region between the sickle-shaped wall sections  4   b  and the base elevations  7 , the width of the channel path  2   a  is such that the base elevations  7 , at the narrowest point of the channel path  2   a,  are at a distance a 1  ( FIG. 8 ) in the axial direction of 2.0 mm to 4.0 mm from the sickle-shaped wall sections  4   b.    
     Each base elevation  7  has, in the circumferential direction, a greatest extent length l 1  ( FIG. 2 ) of 10.0 mm to 35.0 mm, in particular of 15.0 mm to 25.0 mm, which correlates to the distances of projections  6  which follow one another in the circumferential direction and are assigned in pairs to one another. In the radial direction, each base elevation  7  at its highest point in its central region has a height h 1  ( FIG. 8 ) which amounts to 25% to 60%, in particular 30% to 55%, and, in a particularly preferred manner, at most 50%, of the respectively provided profile depth T 1 . In the axial direction, each base elevation  7  has, at its widest point, a width b 1  ( FIG. 2 ) of 5.0 mm to 15.0 mm. 
     According to  FIG. 3 , each base elevation  7  is composed of a base part  7   a  and a dome-like upper part  7   b  which is placed onto said base part. As  FIG. 6  to  FIG. 8  show, the base part  7   a  is of rectangular design in cross section and, in the radial direction, has a height h 2  which is determined from the channel base  5  and which corresponds to 35% to 80%, in particular 40% to 60%, of the height h 1  of the base elevation  7  ( FIG. 8 ). 
     The dome-like upper part  7   b  is bounded in the radial direction by a top surface  8  ( FIG. 8 ) which slopes uniformly downward from the height hi present at the highest point of the base elevation  7  to the height h 2  at the edges of the dome-like upper part  7   b.  As  FIG. 2  and  FIG. 3  in particular show, the top surface  8  is preferably formed by a plurality of flat partial top surfaces, nine in the exemplary embodiment shown. 
       FIG. 9 a    and  FIG. 9 b    show a circumferential channel  2 ′ which is a variant of the circumferential channel  2  and differs therefrom by channel edges  3 ′ running in a wave-shaped manner in a plan view and by channel walls  4 ′ which adjoin said channel edges and run in a wave-shaped manner in a plan view. The channel walls  4 ′ preferably run at a constant angle of 5° to 30°, in particular of 10° to 20°, to the radial direction. The two channel edges  3 ′ and the two channel walls  4 ′ are formed symmetrically to one another in each case with respect to a plane defined by the circumferential direction and the radial direction, wherein the circumferential channel  2 ′ at the tread periphery has a width B 1 ′ at its widest point and a width B 2 ′ at the narrowest point. The width B 1 ′ amounts to 10.0 mm to 25.0 mm, the width B 2 ′ amounts to 75% to 95% of the width B 1 ′. The channel walls  4 ′ have wall sections  4 ′ a  which are curved concavely toward one another in a plan view and wall sections  4 ′ b  which are curved convexly toward one another in a plan view, in an alternating manner in the circumferential direction. 
     In each intermediate space which is located between opposite wall sections  4 ′ b  curved convexly toward one another, a base elevation  7 ′ configured in a manner corresponding to the base elevation  7  of the first design variant ( FIG. 1  to  FIG. 8 ) is formed centrally on the channel base of the circumferential channel  2 ′ and has a top surface  8 ′ which, in the exemplary embodiment shown, contacts the channel walls  4 ′ at their radially inner end regions ( FIG. 9 b   ). In a preferred manner, a channel path which encircles all of the base elevations  7 ′ and is at a distance of 2.0 mm to 4.0 mm from the wall sections  4 ′ b  in the axial direction remains on the channel base of the circumferential channel  2 ′. Of the channel base of the circumferential channel  2 ′, there remains a multiplicity of channel base regions  5 ′ which run at a profile depth between mutually adjacent base elevations  7 ′ and are in the manner of an elongated X in the circumferential direction in a plan view. 
       FIG. 10 a    and  FIG. 10 b    show a circumferential channel  2 ″ which is a further variant of the circumferential channel  2 . The circumferential channel  2 ″ differs from the circumferential channel  2  by base elevations  7 ″ configured differently from the base elevations  7  thereof. The base elevations  7 ″ are bounded in the radial direction by a top surface  8 ″ which has a core top surface  8 ″ a  oriented parallel to the tread periphery and an edge top surface  8 ″ b  which encircles the latter and slopes downward toward the edge of the base elevation  7 ″. In the radial direction, the base elevations  7 ″ in the region of the core top surface  8 ″ a  have a height h 3  ( FIG. 10 c   ) which amounts to 25% to 60%, in particular 30% to 55%, and, in a particularly preferred manner, at most 50%, of the profile depth T 1 . As  FIG. 10 c    shows, the base elevations  7 ″ are composed of a base part  7 ″ a  and an upper part  7 ″ b  which is placed onto the latter and is trapezoidal in cross section. The base part  7 ″ a  reaches in the radial direction as far as a height h 4 , which corresponds to 35% to 90%, in particular 70% to 80%, of the height h 3  of the base elevation  7 ″ ( FIG. 8 ). 
     The invention is not limited to the embodiments described. The base elevations can be in a form differing from that described, in particular in the form of hemi-ellipsoids or in the form of subsections of hemi-ellipsoids. The channel walls of the circumferential channels can also be formed without the radially outer sections which are mentioned in conjunction with the first design variant ( FIG. 4  to  FIG. 8 ) and run in the radial direction. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  . . . Profile positive 
           2 ,  2 ′,  2 ″ . . . Circumferential channel 
           2   a  . . . Channel path 
           3 ,  3 ′ . . . Channel edge 
           4 ,  4 ′ . . . Channel wall 
           4   a,    4 ′ a  . . . Wall section 
           4   a ′, . . . Wall region 
           4   b,    4 ′ b  . . . Wall section 
           4   c  . . . Connecting surface 
           5  . . . Channel base 
           5 ′ . . . Channel base region 
           6  . . . Projection 
           7 ,  7 ′,  7 ″ . . . Base elevation 
           7   a,    7 ″ a  . . . Base part 
           7   b,    7 ″ b  . . . Upper part 
           8 ,  8 ′,  8 ″ . . . Top surface 
           8 ″ a  . . . Core top surface 
       
    
       8 ″ b  . . . Edge top surface
     a 1  . . . Distance   b 1  . . . Width   B 1 , B 2  . . . Width   B 1 ′, B 2 ′ . . . Width   l 1  . . . Extent length   h 1 , h 2 , h 3 , h 4  . . . Height   T 1  . . . Profile depth   T 2  . . . Depth   α, β angle