The present invention relates to footwear equipped with a sole intended to provide the footwear with a good slip-resistant contact with a work surface which may be made slippery by liquid or solid foreign substances. It is applicable to work or sports footwear, for example, which require good gripping qualities on naturally slippery ground and on very smooth natural or synthetic coverings such as Linoleum (registered trademark), varnished tiles, polished stone, and metallic surfaces, particularly when these surfaces are wetted or moistened by a liquid (such as water, oil or blood) or are covered by pools of liquid or are soiled by other types of impurity such as mud or ice.
Falls caused by involuntary slipping are among the most frequent and serious causes of accidents at the present time. This is particularly true of accidents at work, and specialists in the field have been searching for some time for ways of decreasing the frequency and seriousness of these accidents. Notably, a number of safety footwear manufacturers have already begun to market footwear provided with soles designed to impart good slip-resistant properties. Gripping properties of footwear are also highly valued in many forms of sport.
The documented prior art also describes numerous embodiments having the same objective. The model filed in the United States under the number US D446912S provides a good example, illustrated in
U.S. Pat. No. 7,146,752 describes a sole for footwear which also has regular alignments of elastomeric lugs projecting from the surface of the sole base towards the ground. Each lug is formed by patterns in the shape of a star with four arms which are orientated substantially longitudinally, in one direction, and transversely, in the other direction. These lugs are aligned in diagonal rows at approximately 45 degrees with respect to the longitudinal direction, which delimit grooves between them for the discharge of liquids and foreign substances which are displaced by the lugs during the progress of the footwear along the ground. In order to increase the penetration of the edges at the margins of the lugs into the substances covering the ground, the distance between the extremities of the tips at the ends of the arms of each start and the base surface of the sole is made to be greater than the height of the central surface of each lug above this base surface; another option mentioned in the document is that of providing this surface with a concavity which terminates at the margin of each lug in an edge having a cross section forming an acute angle.
U.S. Pat. No. 7,310,894 also illustrates slip-resistant footwear for use in the shower, the sole of this footwear being pierced with apertures intended to allow water to flow through the sole, but also having contact lugs separated by grooves and additionally divided by slits. These slits or incisions can increase the deformation of the lug material when it is in contact with the ground. In one embodiment, each lug is polygonal and is divided into sectors by discharge slits radiating from the centre of the lug towards the vertices of the polygon.
Appreciable results in terms of grip are achieved with these different prior art sculptures. However, systematic studies of slip-resistant footwear by the applicants have shown that the slip-resistant properties of soles can be increased further in terms of the variety of risks of slipping and the circumstances, sometimes difficult to foresee, which may cause slipping. Consequently there are still improvements to be made.
The present invention is intended to improve the prevention of slipping and to limit the sliding to which users may be subject on slippery ground, even if they are equipped with special footwear. Additionally, as in all cases in which the use of an object is intended to achieve a compromise between various kinds of performance, this improved safety must be achieved while maintaining other kinds of performance such as the degree of wear due to use, comfort, and protection of the integrity of the surfaces with which the footwear is in contact. Notably, the protection of the integrity of the contacted surfaces requires the prevention, as far as possible, of the capture and retention of small objects (such as small pebbles) in the grooves or hollows formed in the design of the sculpture of the sole.
For this purpose, the invention proposes safety footwear with enhanced slip-resistant properties for cases of interfaces between the sole and the ground where there is a particularly high degree of slipping, notably when an intermediate foreign substance is present. This footwear comprises a sole having a base of elastomeric material, this sole having an upper and a lower face, the upper face being intended to support the foot of the user of the footwear,
According to the invention, the footwear comprises a sole having a base of elastomeric material, at least one area of which is provided with contact lugs emerging from the lower face of the sole so as to contact the ground, and in which these contact lugs are separated from each other by grooves which delimit stems at acute angles, that is to say at angles of less than 75 degrees. The contact face of each lug is in the shape of a star having at least five alms distributed over the profile of said contact face; each stem is separated from its neighboring stem in the lug by a recess pointing towards the centre of the star shape. This sole is characterized in that, for a plurality of first contact lugs of said area, each of said first contact lugs has at least one stem-to-recess coupling in the form of a coupling between a first stem and a recess separating two neighboring stems in the profile of a second contact lug which neighbors the first lug in said area. In this case, the term “stem-to-recess coupling” is taken to mean that the end of one stem of a first contact lug is positioned in the vicinity of a recess between two stems of a neighboring second lug and within the circle circumscribed about said second lug. The end of a stem can be in the form of a tip formed by an intersection between two faces, or can be of truncated form.
For ease of reference, when two lugs are in the condition described in the preceding sentence, they will be said to be in a condition of “coupling”, by analogy with the case of gearing in which a tooth of a first gear wheel is engaged in the space formed by the recess between two teeth of a neighboring second gear wheel coupled to the first.
In a complementary variant, said first lug has at least one recess separating two neighboring stems in the profile of the lug, which delimits a space of the corresponding groove in which a stem of a neighboring second stem is engaged in said area.
Additionally, in one embodiment, each first lug has (i) at least two couplings of its stems to recesses separating neighboring stems in the profiles of neighboring lugs and (ii) at least two couplings of its recesses between neighboring stems in its profile to stems of neighboring lugs.
The mutual arrangement of the star-shaped patterns according to the invention also has the advantage of providing the sole with good resistance to the retention of foreign bodies such as pebbles in the grooves of the sculpture, because of the head-to-tail arrangement of the arms or stems in the stem-to-recess coupling position in said grooves. Because of the bending flex of the stems, the ejection of foreign bodies (such as small pebbles) is promoted.
Clearly, owing to the characteristics according to the invention as defined above, the density of distribution of the tips or ends of stems in an area of a sole can be increased, as can the density of the edges bordering the lugs along the grooves, which promotes grip, while decreasing the rate of indentation of the sculpture located in this part of the sole. In the following description, the expression “rate of indentation” is used in respect of a sculpture comprising rubber solids which create patterns on the surface and which are separated from each other by hollows, to signify the ratio between the unit surface of the hollows of the sculpted area and the total unit surface in a plan view of a specimen of this sculpture. A reduction in the rate of indentation increases the area of the lug material in contact with the support surface. As this contact area increases and the engagement pressure of the material decreases, the grip improves, as does the wear-resistance of the sole.
Additionally, according to a complementary characteristic of the invention, the resistance to the retention of foreign bodies can be increased by arranging the lateral walls delimiting stems in such a way that, instead of being strictly perpendicular to the base of the sole, they are turned slightly towards the outside of the sole, with a taper angle which tends to drive towards the outside of the sole any foreign body which comes into contact with these walls and which may tend to be trapped between the two opposing walls located on either side of the groove. In an improved arrangement, it is also possible to vary this taper angle along the stem of each lug to accentuate the instability of the trapping action and thus promote the ejection of foreign bodies. It is also possible to form bosses acting as stone removing devices, projecting from the bottom of the groove at the intersections of the grooves.
In one embodiment, the area of the sole in question is provided with a plurality of first lugs, each first lug being surrounded by at least four second lugs distributed around its circumference, and each second lug being in a position of coupling with the first lug. Each of these second lugs is itself surrounded by a set of at least four lugs, including said first lug, and is coupled to these. This provides a high density of packing of the sole with the sculpted lugs in order to achieve good grip and a lower rate of indentation. The lugs of the area in question closely cover the sole with tips which can cut in many directions into the substances interposed between the ground and the sole. Because of the recommended arrangement, this result is achieved without degradation of the other forms of performance expected from the footwear in the desired application.
Highly satisfactory results have been obtained, notably, with footwear provided with a sole in which each first lug in the area has six stems and is surrounded by a set of at least six neighboring lugs distributed around its circumference. Preferably, each of the lugs of this set is in a condition of mutual stem-to-recess coupling with the first lug which they surround; that is to say, each coupling comprises an engagement of a stem of the first lug in a recess of a second lug and a stem of this second lug engaged in a recess of the first lug. The applicant has discovered that the specific geometric properties of this configuration provide numerous benefits in the search for an effective compromise between the various constraints governing the sole during its use.
By using the arrangement according to the invention, it is possible to multiply the directions in which the sole of the footwear has protrusions or edges capable of penetrating foreign substances which are interposed between the sole and the ground and which may cause a loss of grip. This characteristic is reinforced as the number of arms of each lug increases. In an improvement, it is also possible to increase the number of directions in which the stems of the sculpted lugs point by means of an arrangement in which the orientations of the stars of the neighboring lugs are offset angularly with respect to each other.
In another aspect of the arrangement of the sculpted lugs in the sole, a first lug is associated by a stem-to-recess coupling, as defined above, with a second neighboring lug, in an alignment belonging to a first network of globally parallel lines in the sole. Preferably, the profile of said first lug is also associated by stem-to-recess coupling with that of another, second, lug in the sculpture, in a second network of lines globally parallel to a direction other than that of the first network in the area.
The lugs of two neighboring lines of the first and/or second network delimit undulating grooves for the discharge of foreign substances dislodged from the interface between the surfaces in contact in the general direction of this first and/or second network. Advantageously, the width of the grooves between the lugs is substantially uniform in order to create channels which facilitate the outward discharge of slippery particles trapped under the sole. Because of the interleaving of the stems defined above, these grooves may have an undulating shape. It is possible, for example, to increase the regularity of the width of the grooves by using stems whose tips are truncated or blunted or rounded as required, since the pressure created on the very small surface of the edge at the moment when the sole of the user engages the ground will still be considerable,
In one embodiment, each lug is also divided by at least one slit or sipe in the thickness of the lug. This path of this slit can be such that it has one end in the centre of the lug while its other end opens into a recess between two stems in the profile of said lug. It therefore follows a path representing a minimum distance between the centre of the lug and one of the edges of the lug between two stems. In a lug with six stems, three slits can be provided, each following the aforesaid path, with their ends opposite said edge meeting at a common point near the centre of the lug, in a radiating configuration. Said slits preferably divide each lug into a plurality of sectors or elementary lugs, each of which may be in the shape of a chevron in the case of a star with six arms. An advantage of this arrangement is that it decreases the distance through which particles of intermediate foreign substances have to be discharged from each point under the lug towards a hollow in the structure of the sole. The slits also enable the sole to be made more supple perpendicularly to its thickness, while providing more cutting edges to increase the local overpressures and providing for the discharge of intermediate impurities released in this way. For this purpose, the orientation of the radiating patterns of these lugs on the surface of the lugs can also be offset angularly from one lug to the next.
As regards the operation of the slip-resistant footwear, it will be understood that the pressure of the application of an edge of an elastomeric lug to the surface of the ground creates a concentration of compressive stresses in the material of this edge which decreases with the distance from the edges of the lug. The pressure on the ground exerted by the ends of the arms of the stars and the edges of the sculpted lugs can penetrate, and initiate the breaking of, any film of liquid or other intermediate substance between the surface of the lugs and that of the ground. This restores the direct local contact between the material of the lug and that of the ground. In the case of ice, slipping is caused by the creation of a film of water on the surface of the ice, and the problem is therefore the same.
Each stem is compressed progressively, thus promoting the propagation of the force breaking the intermediate film of liquid or other impurities, starting from the ends of the stems. An acutely angled stem is preferable in that it is more effective in breaking the liquid film. Additionally, since each edge is never strictly parallel to the surface of the ground at the moment when the lug engages the ground, there is always a concentration of stress at the point of contact which facilitates the breaking of the film in order to put the material of the lug into contact with the ground.
When the intermediate film has been punctured, the edges of the stem continue to cut it, while driving towards the hollow parts (the grooves and any sipes) the liquid or other impurities present between the surface of the ground and that of the lug. The component of the force exerted by the sole in the plane of the ground develops increased pressure on the edge, which drives away the liquid or other surface contaminant (such as a mixture of dust and liquid) in the manner of a windscreen wiper. The dry contact which is established as a result of this then produces a strong increase in local grip.
The extension of dry contact under the lugs of the sole promotes a good distribution and spread of the forces under the sole. The improvement of the grip greatly reduces slipping. This also leads to a decrease in abrasion, thus increasing the service life. The recommended star shape of the lugs also enables the lugs to be arranged so as to regulate the rate of surface indentation (the ratio of the area of the hollows of the sculpture to its total area), in order to increase the contact surface between the material and the ground. As mentioned above, the largest possible dry contact surface is beneficial in terms of grip and wear-resistance.
In the embodiment of the invention, the angle at the tip of each stem is at least 40 degrees. Similarly, the number of arms forming stems of each star is preferably at least six.
It has been noted that the invention provides a slip-resistant action of very high quality between the ground and the sole of footwear, due notably to the reduced retention of pebbles. The arrangement of the sculpture on the surface of this sole makes it possible to penetrate and drive away effectively any substances that lower the grip coefficient and that are interposed in the contact area, notably liquids in the form of films (moisture) or pools (wetness). Because of this mechanism, therefore, a sufficiently large dry contact surface is created at each step of the user to provide improved grip. In this respect, however, the applicants' research has shown that it is preferable to use patterns which not only have the intrinsic characteristics of shape and angle mentioned above, but are also small enough to multiply the points of engagement in the intermediate slippery substance. Thus, it has been shown that the patterns described above are particularly effective if their sizes are such that they can be inscribed in a circle with a maximum diameter of 20 millimeters, or preferably not more than 10 millimeters, and a minimum diameter of 4 millimeters.
According to the invention, these characteristics are also combined with a dense distribution of the lugs in the sculpted sole. For this purpose, a relatively low rate of indentation is specified, at less than forty-five percent and preferably not more than forty percent, to promote the potential extension of the dry grip contact areas.
Surprisingly, sculptures of footwear soles produced with this type of characteristic have a surface with a very distinctive feel when touched, which is different, all other factors being equal, from that of the prior art soles such as that shown in
A sole sculpture is shown in
In
In this example, the width of each undulating groove varies rather widely. In narrow channels such as 25-1, each of which separates a stem tip 22 and a recess 28 between two stems of a neighboring lug, the width barely exceeds 1 millimeter. Conversely, it widens to about 5 millimeters in arms 25-2 in areas where there is maximum spacing between the neighboring stars. It will be demonstrated that this arrangement is not considered optimal for the use of the invention. At this point it will simply be noted that the average width of the channels formed by the grooves in this example varies from 1 to 5 millimeters, with a mean of 3 millimeters. Each lug can be inscribed in a circle with a diameter of 8 millimeters. These numbers give a general impression of the high density of the distribution of the edges of rubber lugs in the surface of the sculpture with a rate of indentation of the sculpture equal to or less than 45%. This still leaves a considerable area of rubber for establishing an effective grip contact with the ground after the liquid covering the ground has been displaced by the rubber lugs under the action of the successive steps of the user. Concerning the edge density, it will also be noted that each lug 21 is divided into three elementary blocks 26 by a set of three slits, indentations or sipes 23 all of which run from the centre of the pattern and each of which terminates in a recess 28 between adjacent edges on the profile of the lug 21.
It will also be noted that one in every two lugs has two slits such as the slits 22 orientated in the longitudinal direction L and only one slit pointing in the transverse direction l. Additionally, each lug 21 is followed in both the longitudinal direction L and transverse direction l by a lug in which the orientations of the stems are offset angularly by 30° with respect to those of the lug 21 which is considered to be the reference lug in this case. Consequently, the lugs of this sculpture form a set whose stems point in twelve different directions and thus impart to a sole provided with this sculpture a capacity of multidirectional resistance to the risks of slipping by a user walking on slippery ground.
In the arrangement of
With reference to
A profile of a footwear sole 41 according to the invention is shown in
It should also be noted that the grooves 35 between the facing sides of the stems which follow each other in one or other direction in this structure have a relatively uniform width and communicate with each other by forming a network of undulating or zigzag channels along which the liquids or other impurities driven from the contact surface between the lugs and the ground can flow and can be discharged from the sole. The arrangement which is described promotes the formation of channels having a relatively, but not completely, uniform width. It should be noted that there is a wider area such as 43, in the form of a triangle bordered by three different lugs, at each end of a parallel sided groove such as 35-B, Tests have shown that this irregularity is not critical, provided that the containment and discharge capacity of the network of channels is sufficient to collect and discharge all the liquids or other substances driven by the progression of the lugs along the surface of the ground.
Returning to
With reference to
It has been found that the arrangement of sculpted lugs interleaved with each other has another advantage in respect of the safety of the sole in situations in which foreign bodies become trapped between the walls of a groove of the sculpture.
With reference to
According to the invention, which relates, notably, to application to slip-resistant contact between the ground and a user's feet, the aim is to produce a sculpture which can effectively penetrate and drive away any intermediate substances which reduce the grip coefficient between the ground and the user, while retaining a maximum dry contact surface when the first objective has been achieved at each step of the user. The applicants' research has demonstrated in this respect that it is helpful to use patterns which not only have the intrinsic characteristics described above, but which also use sufficiently small patterns to multiply the points of engagement with the intermediate substances, combined with a relatively low rate of indentation, that is to say a rate of less than sixty percent (60%) and equal at the most to thirty percent (30%). It has been found that the patterns described above are particularly effective in sizes such that they are inscribed in a circle having a maximum diameter of 10 millimeters and preferably having a diameter in the range from 2 to 8 millimeters. Finally, these patterns are particularly suitable for preventing the retention of pebbles or other objects in the sole, which may be additional risk factors for slipping.
Surprisingly, sculptures of footwear soles produced with this type of characteristic have a surface with a very distinctive feel when touched, which is different, all other factors being equal, from that of the prior art soles such as that shown in
Such an impression is provided, for example, with a sculpture such as that described with reference to
It is possible to produce a sculpture according to the invention with lugs differing in the arrangement of the slits or Sipes such as 34 as regards their orientation or in the number of slits in each lug, in order to improve the isotropy of the sculpture, that is to say in order to achieve uniform performance of the sculpture in all directions or uniform response to stresses in different directions. It is also possible to make a deliberate choice to differentiate or give priority to certain properties of the sculpture in certain directions, for example in the direction of forward movement for footwear. Thus, in
It is possible not only to change the orientation of the star-shaped patterns from one lug to the next, but also to juxtapose lugs of different sizes in the sculpture according to the desired performance.
Clearly, it is possible to devise other systems for designing and arranging sculptures in which the patterns of neighboring lugs defining the sculpture are of different shapes, having, for example, different numbers of arms or having sizes, orientations and slit systems varying between the lugs of the sculpture.
The invention can thus be applied with star-shaped lugs having, for example, five, six or seven arms, (or even more).
Experience has shown that the preceding arrangements tend to provide a significant improvement in the grip of footwear soles on damp or wet ground or ground covered by liquids such as water, oil or blood, or by any other impurities which may create a sliding contact between the materials from which the ground and/or the footwear soles are commonly made. The invention is particularly suited to the production of slip-resistant soles for work footwear and/or sports footwear.
Clearly, the invention is not limited to the examples described above, and various modifications can be made to it without departure from the scope defined by the appended claims.
Number | Date | Country | Kind |
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0856745 | Oct 2008 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/062985 | 10/6/2009 | WO | 00 | 6/29/2011 |