Footwear

Abstract

An item of footwear including a sole assembly that comprises at least an outsole and an insole, and further comprising one or more shear force-reducing coupling elements (30) disposed between the insole and the ground. The coupling elements (30) are adapted to permit limited displacement, in a plane parallel, in use, to the ground, of overlying components of the item of footwear. The coupling elements (30) provide less resistance to displacement of overlying components of the item of footwear in a first direction than in a second, reverse direction.

Claims

1. An item of footwear including a sole assembly that comprises a top plate and a baseplate; one or more shear force-reducing coupling elements disposed between the top plate and the baseplate, each coupling element comprising a deformable main body portion extending from the top plate to the baseplate to provide cushioning and to permit limited displacement, in a plane parallel to the baseplate, of the top plate relative to the baseplate, and wherein each coupling element further comprises a stop portion, spaced from one of the top plate and baseplate, to inhibit deformation of said main body in one direction and thereby provide less resistance to said displacement of the top plate relative to the baseplate in a first direction than in a second, reverse direction.

2. An item of footwear as claimed in claim 1, wherein the one or more coupling elements are incorporated into a midsole that comprises the top plate and the baseplate that lie adjacent an insole and an outsole respectively.

3. An item of footwear as claimed in claim 2, wherein the top plate and the baseplate of the midsole are sheets of synthetic plastics material.

4. An item of footwear as claimed in claim 3, wherein the sheets are of foam material or bonded non-woven material.

5. An item of footwear as claimed in claim 2, wherein the top plate and the baseplate members of the midsole have thicknesses of between 2 mm and 5 mm.

6. An item of footwear as claimed in claim 2, wherein the midsole has an overall thickness of between 3 mm and 20 mm, or between 3 mm and 15 mm, or between 5 mm and 12 mm.

7. An item of footwear as claimed in claim 1, which is a shoe.

8. An item of footwear as claimed in claim 2, wherein the top plate and the baseplate are spaced apart and connected by said one or more coupling elements, the one or more coupling elements being adapted to permit limited displacement, in a plane parallel to the ground, of the top plate relative to the base plate, and wherein the coupling elements provide less resistance to displacement of top plate in a first direction than in a second, reverse direction.

9. An item of footwear as claimed in claim 1, wherein the main body and stop portion of the one or more coupling elements are joined at upper parts of the main body and stop portion.

10. An item of footwear as claimed in claim 1, wherein all the coupling elements are arranged in such a way that they favour displacement in the same direction.

11. An item of footwear as claimed in claim 1, wherein coupling elements are disposed in different regions and the coupling elements in different regions are configured to permit movement of the top plate relative to the baseplate in different directions.

12. An item of footwear as claimed in claim 11, wherein coupling elements are arranged at the heel portion and at the forefoot (toe) portion, the coupling elements at the heel portion being configured to permit movement forwards, and the coupling elements at the forefoot portion being configured to permit backwards displacement of the top plate relative to the baseplate.

13. An item of footwear as claimed in claim 1, wherein coupling elements are arranged to permit lateral displacement of the top plate relative to the baseplate.

14. An item of footwear as claimed claim 1, wherein the coupling elements comprise blocks of rubber or other elastomeric material.

15. An item of footwear as claimed in claim 14, wherein the blocks deform more readily in one direction than in the opposite direction as a consequence of the shape of the blocks.

16. An item of footwear as claimed in claim 14, wherein the blocks deform more readily in one direction than in the opposite direction as a result of the interaction of a block with another component that inhibits deformation of the block in one direction.

17. An item of footwear as claimed in claim 16, wherein said component is formed integrally with the block.

18. An item of footwear as claimed in claim 1, wherein the coupling elements comprise inelastic materials configured in such a way that they exhibit resilient deformation.

19. An item of footwear as claimed in claim 18, wherein the coupling element incorporates a spring-like member that is adapted to deform to a greater extent in response to a force applied in one direction than to a force applied in the opposite direction.

20. An item of footwear as claimed in claim 7, which is a running shoe.

21. A midsole for an article of footwear, the midsole comprising a top plate and a baseplate that lie adjacent an insole and an outsole respectively, the top plate and the baseplate being spaced apart and connected by one or more coupling elements, the one or more coupling elements each comprising a deformable main body portion extending from the top plate to the baseplate to provide cushioning and to permit limited displacement, in a plane parallel to the baseplate, of the top plate relative to the baseplate, and wherein the coupling elements each further comprise a stop portion, spaced from one of the top plate and the baseplate, to inhibit deformation of said main body in one direction and thereby provide less resistance to displacement of the top plate in a first direction than in a second, reverse direction.

Description

(1) Embodiments of the invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which

(2) FIG. 1 is a schematic perspective view of a first embodiment of a midsole for a shoe in accordance with the present invention;

(3) FIG. 2 shows an exploded view of the midsole of FIG. 1;

(4) FIG. 3 is a perspective view from above of the midsole of FIGS. 1 and 2, partially cut away;

(5) FIG. 4 is perspective view from below, with baseplate omitted, of a second embodiment of a midsole according to the invention;

(6) FIG. 5 is a perspective view from the side and below of a coupling element forming part of the midsole of FIG. 4;

(7) FIG. 6 is a side view of another coupling element forming part of the midsole of FIG. 4;

(8) FIG. 7 is a perspective view of a third embodiment of a midsole according to the invention, partially cut away to reveal coupling elements within the midsole;

(9) FIG. 8 is a side view of a coupling element forming part of the midsole of FIG. 7;

(10) FIG. 9 is a perspective view of the coupling element of FIG. 8;

(11) FIG. 10 is a view similar to FIG. 7, of a fourth embodiment of a midsole according to the invention;

(12) FIG. 11 is a perspective view, from above and one side, of a coupling element forming part of the midsole of FIG. 10; and

(13) FIG. 12 is a further perspective view, from below and one side, of the coupling element of FIG. 11.

(14) Referring first to FIGS. 1 to 3, a midsole according to the invention is generally designated 1 and comprises a baseplate 10 and top plate 20 that are of uniform extent and are spaced apart. A stretchable side wall 21 depends downwardly from the perimeter of the top plate 20 and is bonded at its lower edge to the perimeter of the baseplate 10. The baseplate 10, wall 21 and top plate 20 thus form an enclosure.

(15) The baseplate 10 is formed with two generally transverse channels 11,12 that divide the baseplate 10 into forefoot, midfoot and heel portions (10a,10b,10c respectivelysee FIG. 2). The channels 11,12 increase the flexibility of the baseplate 10, and hence of the midsole 1 generally, by permitting a limited degree of hinged movement. The channels 11,12 also play a part in permitting the relative movement of the top plate 20 and baseplate 10 in accordance with the invention, as explained below.

(16) The baseplate 10 and top plate 20 may be formed of any of a wide range of suitable materials, and may be of the same or different materials. Most commonly, such materials will be synthetic plastics materials, for instance relatively thin layers of closed cell foam sheet. The side wall 21 may be formed integrally with the top plate 20, or may be a separate component that is bonded to the perimeter of the top plate 20, as it is to the perimeter of the baseplate 10. The side wall 21 is sufficiently flexible to permit limited movement of the top plate 20 relative to the baseplate 10, in the manner described below.

(17) As shown in FIGS. 1 and 2, the top plate 20 has a continuous, planar surface and the baseplate 10 is formed with the transverse channels 11,12 that divide it into three portions. It will be appreciated that it is also possible for the baseplate 10 to have a continuous, planar surface and for channels or similar formations to be present in the top plate 20. Equally, both the top plate 20 and the baseplate 10 may have such formations.

(18) As can be seen most clearly in FIG. 3, in which the top plate 20 is shown partly cut away, the top plate 20 and baseplate 10 are coupled together by a plurality of coupling elements 30. The coupling elements 30 are cylindrical components that are fixed to the underside of the top plate 20 and to the upper surface of the baseplate 10. Typically, the coupling elements 30 will be made of a resilient foam material. FIG. 2 shows coupling elements 30 upstanding from each of the three portions of the baseplate 10, ie the forefoot, midfoot and heel. In most embodiments of the present invention, the midsole is divided into at least forefoot and heel portions, and coupling elements are present in those regions of the midsole. Coupling elements may also be present in the midfoot region.

(19) The effect of the coupling elements 30 is to connect the top plate 20 to the baseplate 10, but in such a manner that slight displacement of the top plate 20 is possible, relative to the base plate 10 and parallel to the plane of the midsole 1. According to the invention, there is less resistance to such displacement in one direction than in the reverse direction. Thus, displacement of the top plate 20 relative to the baseplate 10 may be brought about more readily by a force applied in one direction, typically but not necessarily by a force acting along an axis parallel to the longitudinal axis of the midsole 1, than by a force applied in the reverse direction. In the embodiment of FIGS. 1 to 3, this effect is brought about by virtue of the fact that the force required to widen the channels 11,12 in the baseplate 10 is less than the force required to compress those channels 11,12.

(20) In many embodiments of the invention, coupling elements 30 disposed in the forefoot and heel regions of the midsole 1 are arranged to facilitate displacement of the top plate 20 in opposite directions relative to the base plate 10. For instance, the coupling elements 30 in the heel region may be arranged to permit displacement of the top plate 20 forwards (ie in the direction of motion of the wearer of a shoe incorporating the midsole 1) and the coupling elements 30 in the forefoot region may be arranged to permit displacement of the top plate backwards relative to the baseplate 10. Such preferred relative movement can be achieved by various means, for instance by the use of two or more different materials or by non-symmetrical shaping of the coupling elements 30.

(21) The embodiments illustrated in FIGS. 4 to 12 incorporate different forms of coupling element that themselves provide for the displacement of the top plate of the midsole relative to the baseplate, with less resistance to displacement in one direction than in the reverse direction.

(22) Referring now to FIGS. 4 to 6, a second embodiment of a midsole according to the invention is generally designated 101 and includes coupling elements of the form shown in detail in FIGS. 5 and 6. For greater clarity, the coupling elements are shown in those Figures on somewhat exaggerated vertical scale.

(23) In FIG. 4, the baseplate 110 of the midsole 101 is shown in phantom. This embodiment 101 incorporates a planar top plate 120, the underside of which carries a pair of coupling elements, 130 a,130 b respectively, at each of the heel and forefoot regions of the midsole 101. The coupling elements 130 a,130 b are bonded to the underside of the top plate 120 and to the upper surface of the baseplate 110.

(24) The four coupling elements 130a,130b are identical, and are shown in greater detail in FIGS. 5 and 6, but the coupling elements 130a at the heel and the coupling elements 130b at the forefoot are mounted in opposite configurations, as can be seen from FIG. 4. FIG. 5 shows a perspective view of a heel coupling element 130a, and FIG. 6 is a side view of a forefoot coupling element 130b.

(25) Each coupling element 130a,130b comprises a unitary block of elastomeric material, which is of uniform cross-section and comprises a generally square main body 131 and a generally triangular or trapezoidal stop portion 132. The main body 131 and stop portion 132 are separated by a narrow gap 133 that extends along most of one side of the main body 131, such that the main body 131 and the stop portion 132 have juxtaposed surfaces that are closely spaced apart. The main body 131 and stop portion 132 are joined at their upper parts, above the upper end of the gap 133.

(26) The main body 131 has a generally square central opening 134 that extends fully through the main body 131. Each opening 134 is packed with tubes or rods 135. Typically the tubes or rods 135 are of compressible or elastomeric material, and are packed sufficiently densely within the opening 134 that they substantially fill the opening 134 and are retained within it.

(27) The construction of the coupling elements 130a,130b is such that they provide considerably less resistance to displacement of the top plate 120 relative to the baseplate in the direction of the arrows A1 and A2, in FIGS. 5 and 6 respectively, than in the direction of arrows B1 and B2.

(28) In relation to the coupling elements 130a at the heel of the midsole 101, movement of the top plate 120 in the forwards direction (FIG. 5, arrow A1) is permitted more freely than movement in the reverse direction (FIG. 5, arrow B1). This is significant in the case of, for instance, a midsole 101 incorporated into a running shoe. The foot of a runner will typically strike the ground at the heel. The impulse in the direction of travel (change of linear horizontal momentum) experienced by the wearer of the shoe at each heel strike is the product of the average force and duration of impact. By permitting the top plate 120 to move slightly forwards when the heel strikes the ground, the duration of the impact is prolonged, and hence the horizontal force experienced by the runner in the direction opposite to the direction of travel is reduced. This decreases the risk of acute or chronic injury, as well as reducing fatigue and potentially leading to improved athletic performance.

(29) Movement of the top plate 120 in the opposite direction relative to the baseplate (ie in the direction of arrow B1 in FIG. 5) is inhibited by the stop portion 132 of the coupling element 130a. Such motion causes the gap 133 to close, and the juxtaposed surfaces of the main body 131 and stop portion 132 to impact upon each other.

(30) The coupling elements 130b at the forefoot region of the midsole 101 provide a similar effect during toe-off, at the commencement of a stride. In this case, however, the runner presses against the ground to propel himself forwards, and the effect of the coupling elements 130b is to permit displacement of the top plate 120 backwards (ie in the direction of arrow A2 in FIG. 6). Again, this prolongs the duration of the action, reducing the force experienced by the runner. Movement of the top plate 120 in the opposite direction (arrow B2) is inhibited in the same manner as described above in relation to heel strike, ie by closing of the gap 133 and impact of the main body 131 on the stop portion 132.

(31) In addition to the effect of the coupling element 130a in permitting movement of the top plate 120 relative to the baseplate, the coupling elements 130a,130b provide for cushioning in the manner of a conventional running shoe midsole construction. As the foot hits the ground, as well as the deformation of the coupling element 130a that permits forwards movement of the top plate 120, compressive forces are applied to the coupling element 130a. These forces cause the tubes or rods 135 to be pressed closer together and to reduce in diameter. The tubes or rods 135 may roll over each other in order to accommodate the forces applied to them. The coupling elements 130a thus absorb some of the forces of the impact of the runner's heel on the ground. The coupling elements 130b at the forefoot region of the midsole 101 undergo similar compression during the toe-off phase of the runner's stride.

(32) The arrangement of coupling elements 130a,130b described above is appropriate for a shoe worn by a runner whose gait involves landing on the heel region of the foot (a heelstriker). It will be appreciated that for a runner whose running style involves landing on another part of the foot, eg the forefoot, it may be more appropriate for coupling elements at that part of the foot to have the orientation of the coupling elements 130a.

(33) It will be appreciated that, whilst FIG. 4 shows a midsole 101 with the baseplate omitted, a similar arrangement of coupling elements 130a,130b could be mounted directly on the undersurface of the outsole of a shoe (ie in FIG. 4 the component 120 could represent that undersurface). In such a case, the coupling elements 130a,130b are disposed, in use, between the outsole and the ground, and the shear-reducing relative movement is between the outsole and the ground.

(34) Likewise, similarly modified forms of the first, third and fourth embodiments are possible. Thus, referring again to FIGS. 1 to 3, the baseplate 10 with channels 11,12 may be the undersurface of an outsole. Alternatively, the baseplate 10 may be omitted altogether, in which case the coupling elements 30 will be in direct contact with the ground. In this case, however, the structure of the coupling elements 30 needs to be such that they provide greater resistance to displacement of the overlying components in one direction than in the reverse direction. To achieve that, the coupling elements may not have the form of simple cylinders of a single material, as depicted in FIGS. 2 and 3, but may instead have a geometrical shape that confers upon the coupling elements 30 different bending and stiffness characteristics in different directions, and/or the coupling elements may have a composite structure, different regions of the coupling elements 30 being formed in different materials in order to confer upon the coupling elements 30 the required directionality in their bending characteristics.

(35) Turning now to FIGS. 7 to 9, a third embodiment of a midsole according to the invention is generally designated 201 and comprises coupling elements of the form shown in FIGS. 8 and 9.

(36) As can be seen in FIG. 7, in which the planar top plate 220 is partially cut away, a plurality of coupling elements 230a,230b are bonded to the underside of the top plate 220 and to the upper surface of the baseplate 210, in the forefoot (coupling elements 230a) and heel (coupling elements 230b) regions, as for the first specific embodiment of the invention.

(37) The coupling elements 230a,230b are identical and are arranged in regular arrays, as can be seen in FIG. 7. However, other patterns or arrangements of the coupling elements 230a,230b are possible, to confer different mechanical properties beneficial to the wearer.

(38) The coupling elements at the forefoot 230a and the heel 230b are mounted in opposite configurations, as described for the first specific embodiment of the invention.

(39) FIGS. 8 and 9 show a forefoot coupling element 230a in greater detail. FIG. 8 shows a side view of the forefoot coupling element 230a, and FIG. 9 shows a perspective view from above and one side.

(40) Each coupling element 230a,230b consists of a generally cuboidal block of elastomeric material, with three cut away regions 231a,231b,231c, which define a pillar portion 232. The cut away regions 231a,231b,231c allow the structure to partially and resiliently collapse/deform. Coupling element 230a (FIG. 9) is able to partially and resiliently collapse/deform in directions x, y and z. By partially and resiliently collapse/deform is meant that the cuboidal block may be compressed or deformed under pressure in those directions, and will return to its original configuration when the pressure is removed.

(41) The coupling elements 230a,230b are generally equally deformable in the x and y directions, ie transverse to the longitudinal axis of the midsole 301. However, the construction of the coupling elements 230a,230b is such that, in the z direction, they provide considerably less resistance to displacement of the top plate 220 relative to the base plate 210 in the direction of the arrows C1, in FIGS. 8 and 9, than in the direction of arrows D1.

(42) Movement of the top plate 220 in the opposite direction relative to the base plate 210 (ie in the direction of arrows D1 in FIGS. 8 and 9) is inhibited by the pillar portion 232 of the coupling elements 230a,230b, which prevents its partial collapse by providing an uninterrupted support which extends from top to bottom of the coupling elements 230a,230b.

(43) The coupling elements 230a,230b thus act in a similar manner to the coupling elements 130a,130b of the first specific embodiment of the invention, prolonging the duration of the heelstrike and toe-off actions, and so reducing the force experienced by a runner, as for the first embodiment.

(44) As noted above, modified forms of the third embodiment are possible, in which the baseplate 210 is the ground-contacting surface of an outsole, or is omitted so that the coupling elements 230 are in direct contact with the ground.

(45) Finally, FIGS. 10 to 12 illustrate a shear-reducing midsole according to a fourth embodiment of the invention. The midsole is generally designated 301 and comprises coupling elements of the form shown in FIGS. 11 and 12.

(46) As can be seen in FIG. 10, in which the planar top plate 320 is partially cut away, a plurality of coupling elements 330a,330b are bonded to the underside of the top plate 320 and to the upper surface of the baseplate 310, in the forefoot (coupling elements 330a) and heel (coupling elements 330b) regions, as for the first and second specific embodiments of the invention.

(47) The coupling elements 330a,330b are identical and are arranged in regular arrays, as can be seen in FIG. 10. Again, other patterns or arrangements of the coupling elements 330a,330b are possible, to confer different mechanical properties beneficial to the wearer.

(48) The coupling elements at the forefoot 330a and the heel 330b are mounted in opposite configurations, as for the first and second specific embodiments of the invention.

(49) FIGS. 11 and 12 show a forefoot coupling element 330a in greater detail. FIG. 11 shows a perspective view from above and one side of the forefoot coupling element 330a, and FIG. 12 shows a perspective view from below and one side.

(50) Each coupling element 330a,330b is injection-moulded in rigid plastics material, and is of generally square extent in side view, and of uniform cross-section.

(51) The block has a base part 331 that is affixed to the baseplate 310 and a top part 332 that is affixed to the top plate 320. The base part 331 and the top part 332 are connected by a somewhat flexible upstand 333, at the right hand (as viewed in FIGS. 11 and 12) side of the coupling element 330a. The underside of the top part 332 is curved and, together with the internal side of the upstand 333 and the upper surface of the base part 331, forms a generally circular opening 335.

(52) At the left hand side (as viewed in FIGS. 11 and 12) of the coupling element 330a, an arcuate, generally part-circular, spring element 334 extends upwardly from the base part 331 and follows the correspondingly-shaped curved undersurface of the top part 332. Overall, the spring element 334 subtends approximately 250 of arc, such that it terminates at a position adjacent the approximate mid-point of the upstand 333.

(53) The structure of the coupling element 330a means that there is considerably less resistance to displacement of the top plate 320 relative to the baseplate 310 in the direction of the arrows E1 in FIGS. 11 and 12, than in the direction of arrows F1.

(54) Backwards pressure applied to the top plate 320 of the midsole 301, as occurs during the toe-off phase of a runner's stride, results in a compressive force upon the coupling element 330a, which is accommodated by resilient deformation of the spring element 334, the tip of the spring element 334 being displaced downwardly, effectively reducing the diameter of the generally circular opening 335. It will also be appreciated that a compressive force applied vertically to the coupling element 330a, causing an effective reduction in the diameter of the opening 335, generates some displacement of the top part 332 in the direction of arrow E1.

(55) Forwards pressure applied to the heel part of the midsole, as during heelstrike, has a similar effect on the coupling elements 330b in that part of the midsole 301.

(56) The spring element 334 is much less deformable in response to force applied in the direction of the arrows F1, and hence displacement of the top plate 320 relative to the baseplate 310 of the midsole 301 in that direction (ie backwards at the heel portion of the midsole, and forwards at the forefoot region) is more strongly resisted.

(57) Again, modified forms of the fourth embodiment are possible, in which the baseplate 310 is the ground-contacting surface of an outsole, or is omitted so that the coupling elements 330 are in direct contact with the ground.