Abstract:
There is provided a sole unit having a midsole section and an outsole section. The midsole incorporates a number of cavities which open at their top ends and which are wider at their bottom ends. The outsole section incorporates a number of diaphragm elements which close off the bottoms of the cavities. In some arrangements there is a footbed which has in its underside a number of recesses disposed above each of the cavities, the recesses being linked by channels and incorporating orifices leading to the inside of an article of footwear.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to footwear and more particularly to sole units for boots and shoes. 
       BACKGROUND OF THE INVENTION 
       [0002]    Radford, EP 0122985 entitled “Improvements Relating to Footwear” discloses a sole unit molded from a resilient material, in which sole unit is provided a plurality of cavities and a system of channels formed in the upper surface of the sole unit which interconnect the cavities. At the lower end of each cavity a bulge extends downwardly from the bottom surface of the sole unit at the location of each cavity, so that the pressure exerted by the foot on any bulge expels air from the associated cavity, and the action of walking pumps air from one cavity to another along the channels and in this way absorbs the shocks of impact of the foot with the ground. The cavities are formed substantially wholly in the general thickness of the sole unit. 
       SUMMARY OF THE INVENTION 
       [0003]    According to the present invention, there is provided a sole unit for an article of footwear comprising a midsole section and an outsole section, the midsole section having formed therein a plurality of cavities each of which is open at its top end and is of smaller cross-sectional area at said top end than its bottom end, the outsole section incorporating a plurality of diaphragm elements, each of which closes off the bottom of one of the cavities and is capable of resiliently deflecting relative to its associated cavity to effect a pumping action therein. 
         [0004]    Usually, the sole unit also comprises a footbed disposed above the midsole section, the footbed having a through orifice at the location of the top opening of each cavity. Preferably, the footbed has a number of channels in its underside, said channels interconnecting the cavities of the sole unit. Often, further through orifices lead from the channels to the top side of the footbed and also the area of the underside of the footbed surrounding each orifice is concave. 
         [0005]    In preferred arrangements the cross-sectional area of each cavity continually reduces towards its top end and preferably the cavities are substantially frusto-conical. Conveniently, each diaphragm is defined by a reduced thickness periphery and in addition the lower surface of each diaphragm is domed downwardly so as to protrude below the surrounding portions of the outsole section. 
         [0006]    With some preferred embodiments, the midsole section is formed from a different material to the outsole section. Preferably, the midsole section is formed separately from and is secured to the outsole section. Sometimes the outsole section is formed from a plurality of separate portions which are attached to the midsole section. Preferably, the outsole section is not continuous over the entire footprint of the sole unit. 
         [0007]    It is also possible that valve means are provided to control air flow through and/or between the cavities. In some sole units, the diaphragms are transparent or semi-transparent. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Embodiments of the present invention will now be described by way of example. The description makes reference to the accompanying drawings in which: 
           [0009]      FIG. 1  is a side perspective view of an article of footwear incorporating a sole unit according to the present invention, 
           [0010]      FIG. 2  is an exploded view from below of the sole unit shown in  FIG. 1 , 
           [0011]      FIG. 3  is a lateral cross-sectional view through the assembled sole unit of  FIG. 2 , 
           [0012]      FIG. 4  is a lengthwise cross-sectional view through the heel part of an alternative sole unit according to the present invention, 
           [0013]      FIG. 5  is a lateral cross-sectional view through the heel part shown in  FIG. 4 , 
           [0014]      FIG. 6  is a perspective view of a valve insert shown in  FIGS. 4 and 5 , 
           [0015]      FIG. 7  is a bottom plan view of another embodiment of a sole unit in accordance with the invention, 
           [0016]      FIG. 8  is a top plan view of the upper surface of the midsole section of the sole unit of  FIG. 7 , which has a plurality of channels corresponding to the channels in the footbed lower surface of  FIG. 9 , 
           [0017]      FIG. 9  is a bottom plan view of the lower surface of a footbed, which has a plurality of interconnecting channels corresponding to the plurality of channels of  FIG. 8 , and 
           [0018]      FIG. 10  is a top plan view of the upper surface of the footbed of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to the drawings, there is shown an article of footwear  10  having an upper  11  secured to a sole unit  12 . In this arrangement, the sole unit comprises a footbed  13 , a midsole section  14  and an outsole section  15 . The footbed  13  is molded from a resilient plastics material such as polyurethane but other materials could also be used. In this arrangement, the midsole section is molded from a resilient plastics material such as EVA but again other materials would be suitable. The outsole section  15  comprises a number of natural rubber or synthetic rubber outsole portions  16  but a continuous outsole could also be used, as could other materials. This particular rubber compound has a Shore hardness of between 55 and 65 but other hardnesses could be employed depending on the required characteristics of the footwear. The use of separate outsole portions  16  can also lend itself to the provision of different materials in different parts of the outsole section  15  to produce varied wear/comfort characteristics. 
         [0020]    The midsole section  14  has a plurality of frusto-conical cavities  17  each of which has a small opening at its top end  18  and a wider opening at its bottom end  19 . In addition, there are a number of optional grooves  20  in the underside of the midsole section  14 , the grooves improving the flexibility of the sole unit in chosen areas and giving an element of decoration. The outsole portions  16  are securely bonded to the underside of the midsole section and the outsole portions  16  are shaped so as not to cover the grooves  20 . 
         [0021]    The parts of the outsole portions  16  which cover the bottom ends  19  of the cavities  17  are in the form of diaphragms  21  each of which connects to the surrounding part of outsole portion  16  by means of a peripherally extending portion  22  of reduced thickness. Each reduced thickness portion  22  enables its enclosed diaphragm  21  to resiliently deflect more easily relative to its adjacent cavity  17 . The lowermost surface  23  of each diaphragm bulges downwardly so as to protrude below the surrounding parts of the outsole portion  16 . 
         [0022]    The underside of the footbed  13  has a concave recess  25  positioned above each cavity top end  18  and the recesses  25  are interconnected by means of a plurality of channels  26  formed in the underside of the footbed. In alternative embodiments the plurality of channels are provided in the upper surface of the midsole, or in both the underside of the footbed and the upper surface of the midsole. Alternatively, as seen in  FIGS. 8 and 9 , the plurality of channels  26  are provided in the underside of the footbed  13  and a plurality of corresponding channels  50  are provided in the upper surface of the midsole section  14 . Also, cavities  52  may be provided in the footbed  13  in fluid communication with the channels  26 . 
         [0023]    A through orifice  27  is provided at each recess  25  to effect communication with the top side of the footbed. Further orifices  28  are provided in the channels  26 . Additional through orifices  54  may be provided to extend from cavities  52  in the footbed to the upper surface of the footbed  13 . The action of walking causes the diaphragms  21  to deform resiliently upwards into the cavities  17  and back again thereby pumping air from cavity to cavity via the channels  26  and recesses  25 . This action also causes air to flow through the orifices  27  and  28  to provide a ventilating effect within the upper  11  of the article of footwear. 
         [0024]    In on preferred embodiment, as seen in  FIGS. 8 and 9 , the underside of the footbed  13  and the upper surface of the midsole section  14  are provided with a mating corrugated surfaces comprised of a plurality of interfitting ribs. The use of such a mating surface assists to keep alignment of the above described elements of the footbed  13  and the midsole section  14 . Where mating corrugated surfaces are used, a constant depth of the channels  50  can be obtained by providing a plurality of channel structures  58  in the dips between ribs of the corrugated surface of the upper surface of the midsole section  14 . 
         [0025]    In more advanced embodiments, valve means may be provided to control the flow of air into and/or out of the cavities, or through the orifices  27 ,  28 , or along the channels  26 . The valve means could be one-way mechanisms or could rely on compressive closure of the openings due to weight transfer during the walking cycle. 
         [0026]    One example of a sole unit having a valve arrangement is shown in  FIGS. 4 to 6 . The heel area of the sole unit incorporates an air inlet member  40  which is located generally in the midsole section  14  and which extends laterally in this embodiment. The inlet member  40  is generally tubular and is open to the atmosphere at one or both of its lateral ends  43 . The inside of the inlet member  40  communicates with two of the cavities  17  in the heel area via one-way valves  41 . In this embodiment the one-way valves  41  are in the form of “duck-bill” valves but other types of valves are envisaged. Air can therefore be drawn into the cavities  17  by suction when the diaphragms  21  deform resiliently downwards. The cavities  17  also have one-way valves  42  which control communication with the recesses  25 /channels  26 . Again, in this example the one-way valves  42  are “duck-bill” valves which are ideally carried by the inlet member  40 . 
         [0027]    Fresh air drawn into the cavities  17  as the diaphragms  21  deform downwards is then passed outwardly through the valves  42  when the diaphragms  21  deform upwardly into the cavities  17 . This fresh air is distributed around the sole unit and out through orifices  27  and  28  (not shown in  FIGS. 5 and 6 ). This passage of air can assist ventilation of the shoe and/or can provide a cooling action and/or can assist in the dispersal of moisture and/or odor. 
         [0028]    The precise form and location of the valve system is a matter of design choice and could be provided for more cavities than the two shown. The inlet member and valves need not be separate components but could be molded as part of the midsole. 
         [0029]    In other embodiments, the diaphragms  21  could be formed of a transparent or semi-transparent material such that the inside of the cavities/underside of the footbed can be seen. Contrasting colors in the cavity could produce a desirable decorative effect. 
         [0030]    It will be appreciated that the number of cavities could vary as could their precise shape. Also, the reduced thickness portions  22  which define the shapes of the diaphragms could be omitted or partially omitted if the material of the outsole was already sufficiently flexible. The footbed could be omitted in some types of footwear, for example where an insole is lasted to the upper in which case the midsole would be secured to the lasting margin of the upper. Other modifications will be apparent without departing from the scope of the attached claims.