Abstract:
An item of footwear, in particular for sport, includes a sole, a double-crossbow shaped elastic structure, having an upper wall and a lower wall which define an empty space inside them. The elastic structure is placed in the sole so as to elastically react under the weight of a foot. An element extends from one of the walls and is suitable for going into abutment against the opposite wall when the crossbow structure is not compressed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention refers to sports footwear, and more specifically, footwear used for running, or for playing tennis. 
       RELATED ART 
       [0002]    In the footwear field, many shoes are known for sport activities in general, comprising shock absorbing devices or devices that store kinetic energy, like for example, springs or elastic materials. 
         [0003]    The objective is to dissipate some of the energy every time the foot of the athlete touches the ground, thus avoiding shocks, or to elastically accumulate the energy and send it back in the direction of movement when the foot comes off the ground. 
         [0004]    An example of such devices is described in EP0359421. 
       SUMMARY 
       [0005]    In this document, a sports shoe is described comprising a double crossbow spring, in the area under the heel, in particular an elastic-resilient helical-shaped element. 
         [0006]    Such an element is a single separate piece, and is inserted and integrated in a through cavity of the sole. The elastic response of the element is given by the material which forms it, and by its geometric shape. 
         [0007]    However, these two degrees of freedom may not be sufficient to fully modulate the elastic behavior of the element and therefore of the sole. 
         [0008]    If the aforementioned element is made in a material and/or shape which yields too much, it is difficult to avoid it yielding entirely when it bears a heavy load. If the element is made in a more stiff material and/or shape, the response of the sole can be insufficient thus tiring the user and/or exposing him/her to risks of possible trauma whilst reducing the efficiency of movement and reducing the stability of the sole on the ground. 
         [0009]    One purpose of the invention is to improve the prior art. 
         [0010]    Another purpose of the invention is to obtain footwear which has an improved elastic response with respect to the prior art. 
         [0011]    A further purpose of the invention is to obtain a further degree of freedom on which to act to modulate the elastic response of the footwear. 
         [0012]    Yet another purpose of the invention is to simplify the manufacture of footwear made in this way. 
         [0013]    Yet another purpose is to obtain a valid compromise between the protection of the athlete and his/her performance ensuring him/her that the elastic response of the controlled elasticity shock absorbing system is in the direction of its movement and that the energy collected by the system itself is exploited for such an effect. 
         [0014]    Such purposes are obtained by footwear for practicing sport comprising a sole having a double-crossbow shaped elastic structure, having an upper wall and a lower wall which define an empty space inside them. The elastic structure is placed in the sole so as to elastically react under the weight of the foot, such that it comprises an inner element which extends from one of the walls and which is adapted for going into abutment against the opposite wall when the crossbow structure is compressed. 
         [0015]    Said inner element acts to give controlled shock absorption. 
         [0016]    The inclination of the same inner element with respect to the sole allows energy to be given back in the walking/running direction. 
         [0017]    Said inner element acts as an element for controlling the inclination of the foot on the front plane avoiding hyperpronation or, for example in tennis, hyper inclination of the tibiotarsal (supination). 
         [0018]    The shape of the crossbow structure, preferably elliptical or similar, is preferably obtained by using high resilient materials which have good elastic capability. By modifying the thicknesses of the structure at its walls, its mechanical characteristics can be modified to suit the sport technology that it will be applied to. 
         [0019]    The inner controlling element can be inserted in the heel area and also in the area of the fifth metatarsal, extending the effect of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Further characteristics and advantages of the invention shall become clearer from the description given as an example of footwear, together with the attached drawings in which: 
           [0021]      FIG. 1  shows an exploded view of the sole of footwear according to the invention. 
           [0022]      FIG. 2  shows the sole of  FIG. 1  assembled; 
           [0023]      FIG. 3  shows a side view of a variant of the sole of footwear according to the invention; 
           [0024]      FIG. 4  shows a component of the sole of  FIG. 3 ; and 
           [0025]      FIG. 5  shows an exploded view of the sole of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0026]    Footwear according to the invention comprises a sole  10  formed, in sequence, by two parts of tread  12   a ,  12   b  made in rubber or thermoplastic, a heel insert  14 , a first midsole element  20  and a second midsole element  16 . 
         [0027]    The first midsole element  20  is enclosed between the second midsole element  16  and the heel insert  14 , and is formed in a single piece of plastic material. In the portion, which once assembled, is located under the heel of the user, the first midsole element  20  has a double crossbow-shaped elastic structure  22 , with a substantially oval section, which forms a through-opening in the sole  10 . 
         [0028]    The structure  22  has an upper convex wall  26  and a lower convex wall  24 , which face one another. 
         [0029]    From the surface of the wall  26 , a fin or tooth  30  extends out cantilevered, inclined with respect to an axis X that is almost vertical, which substantially corresponds to the axis along which the structure  22  deforms when it is compressed. In such a situation, the walls  24 ,  26  come closer together and the structure  22  reacts to the external force with an elastic reaction in the opposite direction After a certain compression of the structure  22 , the fin  30  touches the opposite wall  24  and slows down or opposes further compression of the structure  20 . 
         [0030]    It should be understood that the selective intervention of the fin  30  in the compression phase of the structure  20  alters its elastic response on the foot, in particular avoiding excessive yielding and by providing a faster elastic return. 
         [0031]    The position of the fin  30  can vary according to the desired dynamic response. Several fins can be used, arranged in same, opposite, and/or symmetric or antisymmetric manner with respect to the walls  24 ,  26  or to the axis X. Each combination will provide its own special dynamic response. 
         [0032]    It should be noticed that the solution of the invention has the versatility of adapting to different usage requirements by being able to be applied to sports even involving different athletic movements. The invention does not have the mere purpose of absorbing the impact and the energy it produces, but to give it back in the direction of movement thus optimizing the use of the footwear. 
         [0033]    The difference in thickness of the walls or their asymmetric shape enable total elasto-mechanic control of the crossbow structure. 
         [0034]      FIG. 3  shows a sole variant  50 , which comprises two tread parts  56   a ,  56   b  in rubber or in thermoplastic, a first midsole element  54 , a second midsole element  60  and a third midsole element  56 . 
         [0035]    The second midsole element  60  is enclosed between the first and third element, and it is formed in a single piece of plastic material. Similar to the previous variant, in the portion which once assembled is located under the heel of the user; the second midsole element  60  has a double crossbow-shaped elastic structure  72 , which is the same as the structure  22 . The structure  72  therefore has an upper convex wall  76 , a lower convex wall  74 , which face each other, and a fin or tooth  80 , positioned like the fin  30  and having an identical function. 
         [0036]    The midsole element  60 , unlike the element  20 , has another two crossbow-shaped structures indicated with  90 ,  95 . 
         [0037]    The first structure  90  is arranged alongside the structure  72 , roughly under the area  10  corresponding to the back of the heel, and is formed by an upper convex wall  92  and a lower convex wall  94 , which face one another. The walls  92 ,  94  are not parallel and define a cylindroid-shaped opening with an oval base which becomes narrower towards the inside of the element  60  extending inside it for a certain depth. 
         [0038]    The second structure  95  is arranged outside the foot, roughly under the metatarsal  15  area, and is formed by an upper convex wall  96  and a lower convex wall  98 , which face one another. The walls  96 ,  98  are not parallel and define a cylindroid-shaped opening with an oval base which narrows towards the inside of the element  60  extending inside it for a certain depth. 
         [0039]    Therefore, while the structure  72  passes through the sole  50  from one side to the  20  other, the structures  90 ,  95  only involve the edge thereof. 
         [0040]    The function of the structures  90 ,  95  is to modulate and/or improve the response of the sole  50  to stress. The structure  90  ensures an elastic return action when there is an impact or pressure at the heel of the user, whereas the structure  95  ensures said action when there is an impact or pressure on the metatarsal area outside the foot. 
         [0041]    The structures  90 ,  95  can be present together, or singularly, according to the desired dynamic response of the sole  50 . 
         [0042]    Other structures similar to  90 ,  95  can be distributed along the perimeter of the sole, in the parts which undergo most stress in the particular sports activity. 
         [0043]    In general, the dynamic response of a sole according to the invention can be changed by varying many parameters, including:
       the thickness and/or the length and/or the width and/or the position and/or the inclination of the fin  30 ,  50 ;   the material the fin  30 ,  50  is made with, which affects the overall elastic behavior of the structure  22 . The material can be different from that which forms the midsole element  20 ,  60 , and the fin  20  in this case is coupled with the walls of the crossbow structure with suitable fixing means, like for example, adhesive, rivets or also through over-injection;   the material the structures  22 ,  72 ,  90 ,  95  are made with, which affects their overall elastic behavior. The material can be different from that which forms the midsole element  20 ,  60 , for example, by over-injecting lamellar elements to form the upper and lower walls of the crossbow structure;   the width and/or the position and/or the opening size and/or the opening shape of the structures  22 ,  72 ,  90 ,  95 . For example, the walls of the structure can be divergent so as to form an opening in the sole with its width increasing outwards, or with a substantially constant section.       
 
         [0048]    The present invention thus conceived can undergo numerous modifications and variants all covered by the scope of protection of the claims.