Patent Publication Number: US-2002004999-A1

Title: Sole for a trail running shoe

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001] This application incorporates by reference, and claims priority to and the benefit of, German patent application serial number 19957821.4, which was filed on Dec. 1, 1999.  
       TECHNICAL FIELD  
       [0002] The invention generally relates to articles of footwear, such as sports shoes, and in particular to a sole for a trail running shoe.  
       BACKGROUND INFORMATION  
       [0003] When shoes, in particular running shoes, are constructed, the design of the sole is of particular importance. The sole performs several functions. The sole should, depending on the intended use of the shoe, provide sufficient cushioning to reduce stresses arising on the human body. Further, the design of the lower part of the sole, the outsole, determines the interaction of the shoe with the ground. The outsole can be designed to optimize the grip of the shoe on the ground.  
       [0004] The optimal design of a sole for a running shoe, for example the number, distribution, shape, and flexibility of profile elements arranged thereon, strongly depends on the intended use of the shoe. The term running shoe may include all kinds of shoes where the sole directly contacts the ground, for example jogging shoes, sprint shoes, or hiking boots. It is, for example, desirable that a sole for a hiking boot to be used on rough ground preferably has a coarser profile structure than a shoe for indoor sports.  
       [0005] It is, however, often a problem with sports shoes that the exact field of use of the shoe, i.e., the ground on which the shoe is to be used, is not clearly determined in advance. For example, running shoes for trail running are often used on a variety of different surfaces. In trail running, the athlete runs over long distances not only on even asphalt roads, but also on gravel roads or woodland trails. Furthermore, depending on weather conditions, the ground may be either dry and hard or wet and muddy. Therefore, it is desirable for a manufacturer of such shoes to construct soles that provide sufficient grip on a plurality of ground surfaces, thereby allowing the multipurpose use of a trail running shoe.  
       [0006] It is known in the prior art to use soles with different characteristics. See, for example U.S. Pat. No. 5,634,283, U.S. Pat. No. 4,271,608, U.S. Pat. No. 4,398,357, and U.S. Pat. No. 5,926,974, the disclosures of which are hereby incorporated by reference in their entirety.  
       [0007] Up till now, different sole materials were almost exclusively employed with respect to the use on grounds with different hardnesses. Other objectives included the self-cleaning of the profile and the reduction in the overall weight of the shoe. The problem of using a particular shoe on ground surfaces with different roughnesses, e.g., asphalt or gravel, has until now not been addressed.  
       [0008] It is, therefore, an object of the present invention to provide a sole for a shoe, in particular a trail running shoe, that assures a reliable grip on ground surfaces of different roughnesses.  
       SUMMARY OF THE INVENTION  
       [0009] In one aspect, the invention relates to a sole for an article of footwear. The sole includes at least one first ground engaging profile element with a first flexibility and at least one second ground engaging profile element with a second flexibility. The second profile element has a ridge or riblike shape and the second flexibility is greater than the first flexibility.  
       [0010] In another aspect, the sole includes at least two first ground engaging profile elements with a first flexibility and a plurality of second ground engaging profile elements with a second flexibility. The plurality of second profile elements are arranged on the sole to encompass the at least two first profile elements. The second flexibility is greater than the first flexibility.  
       [0011] In yet another aspect, the invention relates to an article of footwear. The article of footwear includes a sole having at least one first ground engaging profile element with a first flexibility and at least one second ground engaging profile element with a second flexibility. The second profile element has a ridge or riblike shape and the second flexibility is greater than the first flexibility.  
       [0012] In some embodiments, the first and the second profile elements are substantially the same height. In other embodiments, the first and the second profile elements are about 1 mm to about 10 mm high, preferably about 3 mm to about 8 mm high, and more preferably about 5 mm high. In still other embodiments, the height of the first profile element at least slightly exceeds the height of the second profile element. Both profile elements may simultaneously contact on even ground surfaces when the first profile element is compressed by the weight of a wearer.  
       [0013] In some further embodiments, a plurality of first profile elements are arranged in a forefoot area and a midfoot area of the sole. These areas of the sole may be more critical to gripping during push-off from the ground. Additional first profile elements can be arranged along an outer edge of the forefoot area and the midfoot area of the sole. This arrangement may improve sideways grip. In other embodiments, the first profile elements are essentially arcuate or sickle-shaped and/or can be oriented substantially perpendicular to a longitudinal axis of the sole. The substantially perpendicular orientation may aid push-off in a forward direction.  
       [0014] In still some further embodiments, the second profile elements include parallel ridges spaced apart from each other to allow substantially independent deflection of each of the ridges. In various embodiments, the ridges are about 0.5 mm to about 3.0 mm wide and preferably about 1.0 mm to about 2.0 mm wide. The parallel ridges are spaced about 0.5 mm to about 4.0 mm apart and preferably about 1.0 mm to about 2.0 mm apart. This spacing allows the ridges to deflect on rough surfaces independently of each other. In other embodiments, a plurality of second profile elements can be arranged around the at least one first profile element, thereby obtaining an isolated first profile element when the second profile elements are deflected. Such an arrangement is well suited for engaging a rough surface. In still other embodiments, the at least one second profile element can be oriented substantially perpendicular to a longitudinal axis of the sole.  
       [0015] In some additional embodiments, the sole includes an elongate indentation disposed between a forefoot part and a midfoot part and extending from a lateral side to a medial side of the sole to facilitate greater flexibility in a wearer&#39;s natural gait cycle. In other embodiments, the sole may include a reinforcing element disposed in the midfoot area of the sole for support of an arch of a wearer&#39;s foot and/or a damping element disposed in a heel area of the sole.  
       [0016] These and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description of embodiments of the invention, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings in which:  
     [0018]FIG. 1 is a planar schematic view of an outsole of one embodiment of an article of footwear according to the invention; and  
     [0019]FIG. 2 is a perspective schematic view of the embodiment of FIG. 1. 
    
    
     DETAILED DESCRIPTION  
     [0020] One embodiment of the present invention includes a sole  1  with essentially two groups of downwardly extending profile elements. For the sake of simplicity, only generally commonly configured profile elements  10 ,  20  of the two groups are identified in FIGS. 1 and 2. It is, however, to be understood that the following description relates to all profile elements of each respective group, where variations within one or the other group concerning the size and the orientation are possible. Further, the sole depicted in FIGS. 1 and 2 is for a left shoe; however, it is to be understood the right shoe is typically a mirror image of the left shoe and the description applies to both the left and right shoes.  
     [0021] As can be seen from FIG. 1, which presents a view from the bottom of a shoe  2 , nine first profile elements  10  are arranged on the medial and lateral midfoot part  6 ,  7  and the lateral forefoot part  8  of the sole  1 . The first profile elements  10  may be embedded into a plurality of ridge or riblike second profile elements  20 . This arrangement of the elements  10 ,  20  corresponds to the parts of the sole  1  that are important for a good grip, in particular during the rolling-off and pushing-off phase of a step cycle. For additional grip during ground contact with the heel, additional profile elements (not shown) can be arranged in the heel part of the sole.  
     [0022] The first profile elements  10  are, in their original configuration, about 0.5 mm higher than the second profile elements  20 , so that under compression by the weight of an athlete, both groups of profile elements contact the ground. As a result, a comparatively dense ground contacting profile results, as can be seen in FIG. 2, thereby providing good grip on an even ground surface, such as an asphalt road or a gymnasium floor. In the embodiment shown in FIGS. 1 and 2, the height of the profile elements  10 ,  20  is about 5 mm; however, other height dimensions, for example between about 1.0 mm and about 10.0 mm, are also possible.  
     [0023] The first profile elements  10  may be made of a comparatively hard and relatively inflexible material. They deform only slightly under stress during ground contact and are, therefore, able to penetrate the ground on which a sole  1  according to the invention is used. In some embodiments, the first profile elements  10  have a Shore hardness of approximately  65 A.  
     [0024] In contrast thereto, the second profile elements  20  may be made out of a soft and sticky rubber, thereby providing a greater flexibility than the first profile elements and a good grip even on wet surfaces due also, in part, to their thin, riblike configuration. In some embodiments, the second profile elements  20  have a Shore hardness of approximately  60 A. Due to their greater flexibility, the second profile elements  20  are forwardly or backwardly deflected by protrusions of the ground (see arrow  21  in FIG. 2). As a result, they retract with respect to the first profile elements  10  and no longer extend as far downward from the sole  1  as the first profile elements  10 . This occurs most often during running on ground surfaces with great roughness, for example gravel roads. The deflection of the second profile elements  20  results in an overall profile of the sole dominated by the harder first profile elements  10  such that a comparatively rough sole  1  resembling a spiked sole is obtained. In this situation, the first profile element  10  is able to penetrate the ground or to engage the protrusions of the ground and the grip of the sole  1  under these ground conditions is improved. Because of the greater flexibility of the second profile elements  20 , the second profile elements  20  together with the first profile element  10  adapt to the irregularities of the ground surface. In the situation where the sole is used on a comparatively even surface, for example asphalt or the surface of a gymnasium floor, the first and second profile elements  10 ,  20  together provide the contact area of the sole  1  necessary for a good grip.  
     [0025] The second profile elements  20 , which can also be described as lamella-like structures, are shown in FIGS. 1 and 2 with parallel ribs oriented generally perpendicularly to a longitudinal axis  5  of the sole  1 ; however, other shapes and arrangements of the second profile elements  20  are possible. For example, the second profile elements  20  could be concentric rings disposed around the first profile elements  10  or could be irregularly arranged longitudinal units with an arbitrary orientation.  
     [0026] In the embodiment shown in FIGS. 1 and 2, the second profile elements  20  have a width of about 1.0 mm to about 2.0 mm and are spaced about 1.0 mm to about  2 . 0  mm apart. These values, however, are only approximate values. In practice, the spacing of the second profile elements  20  with respect to each other is determined by the requirement that they do not interfere with each other when they deflect, otherwise they may lose their greater flexibility with respect to the first profile elements  10 .  
     [0027] In the embodiment shown in FIGS. 1 and 2, the first profile elements  10  have an essentially sickle-shaped design and are oriented, as are the second profile elements  20 , essentially perpendicularly to the longitudinal axis  5  of the sole  1 . Such an arrangement supports, in particular, a forwardly directed push-off of a wearer of the shoe  2 . Other possible shapes and orientations of the first profile elements  10  are possible, for example a Z-like shape and/or an orientation parallel to or at an acute angle to the longitudinal axis  5  of the sole  1 .  
     [0028] Further details of a sole  1  according to the invention are shown in FIGS. 1 and 2. To support not only a forwardly directed push-off, but also the sideways grip of the shoe  2 , additional first profile elements  11  may be arranged along the medial and lateral edges of one or more of the midfoot part  6 ,  7  and forefoot part  8 ,  9 , where their orientation follows essentially the course of the edge of the sole  1 . One or more separate profile elements  12  are arranged perpendicularly to the longitudinal axis  5  of the sole  1  in the medial forefoot part  9 , which provides good grip in the last phase of the step cycle.  
     [0029] Additionally, the medial and center part of the forefoot can be provided as a stable rolling-off surface  31  extending upwardly from the sole  1  over the front part of the upper  3  of the shoe  2 , thereby increasing the life of the shoe  2 . In the embodiment shown in FIG. 2, the rolling-off surface  31  is ribbed with relatively thick ridges; however, other profile shapes are possible.  
     [0030] Between the forefoot part  8 ,  9  and the midfoot part  6 ,  7  of the sole  1  and extending from the medial to the lateral side is a continuous groove-like indentation  40 . This indentation  40  allows the bending stiffness of the sole to be selectively reduced in this region in order to reduce impairment of the natural rolling-off movement of the foot with the toes.  
     [0031] Additional ribs  50  may be provided in the rear area of the midfoot part  6 ,  7  close to the arrangement of the first and second profile elements  10 ,  20 . The additional ribs  50  may have a mirror-inverted orientation and arcuate shape with respect to the first profile elements  10 . Thus, forward sliding is effectively avoided during the landing phase of a step cycle when the foot contacts the ground. Whereas the profile elements  10 ,  20  primarily support the forwardly directed push-off, the additional ribs  50  serve to decelerate the shoe during landing on the ground. In some embodiments, the additional ribs  50  have metal surfaces to improve their grip on soft ground.  
     [0032] A reinforcing element  60  may be disposed between the midfoot part  6 ,  7  and the heel part  15 . The element  60  supports the arch of the foot and may increase stability of the shoe  2 . Whereas the parts of the sole  1  described until now are made out of more or less flexible materials and serve for improving the grip of the shoe, the reinforcing element  60  is preferably a rigid structural element of the sole  1  and is preferably made out of a stable plastic material. The reinforcing element  60  is disposed on the medial side of the sole  1  and has a three-dimensional shape. In the embodiment shown in FIG. 2, the reinforcing element  60  extends into the midfoot and heel parts  6 ,  7 ,  15 ; however, the degree of the extension may vary. It is also possible that the reinforcing element  60  extends over the complete width of the sole  1  to the lateral side.  
     [0033] The heel part  15  of the sole  1  may include on its lateral side  16  a damping element  70 . This may be desirable, because most athletes first contact the ground with this part of the sole, which typically is where the greatest stress arises. It is, however, also possible that the damping element  70  extends over the complete heel part  15  or just the medial side  17  of the heel part  15 . The surface of the damping element may include a combination of first and second profile elements  10 ,  20  according to the invention. For the sake of simplicity, the embodiment shown in FIG. 2 has a simple grooved profile. In some other embodiments, additional ribs  80  may be arranged on the medial side of the heel part, which by their inclined orientation help avoid sideways sliding of the shoe immediately after the first ground contact.  
     [0034] Having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. The described embodiments are to be considered in all respects as only illustrative and not restrictive. Therefore, it is intended that the scope of the present invention be only limited by the following claims.