US20110247237A1

US20110247237A1 - Shoe with Anti-Skid Sole

Info

Publication number: US20110247237A1
Application number: US13/122,818
Authority: US
Inventors: Adam Jara; Amaud Larregain; Olivier Muhlhoff
Original assignee: Michelin Recherche et Technique SA Switzerland; Societe de Technologie Michelin SAS
Current assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2008-10-06
Filing date: 2009-10-06
Publication date: 2011-10-13
Also published as: JP2012504480A; JP5657544B2; WO2010040755A1; CN102238883A; EP2334211A1

Abstract

Footwear with a sole formed from an elastomeric material whose grip is improved on ground where the interface may include an intermediate foreign substance, this sole comprising lugs (31) separated from each other by grooves (35). The walls of the grooves (35) are cut into the thickness of the elastomeric material and delimit patterns with sharp angles in the profile of said lugs (31) which can pierce said foreign substance to establish direct dry contact between the two surfaces. Each lug (31) forms a star-shaped pattern having at least five arms in the form of stems (32) distributed over its, profile and each stem (32) is orientated radially towards the outside of the pattern and terminates in an end. Each stem (32) is separated from its neighbor by a recess (38) in the profile of the lug. Finally, each lug (31) has a stem (32) engaged in a space of the adjacent groove (35) which is delimited by a recess (38) between two neighboring stems in the profile of a second lug neighboring the first lug.

Description

TECHNICAL FIELD

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.

PRIOR ART

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 FIG. 1, of proposed arrangements to increase the grip of the soles of footwear, comprising a relatively supple or flexible sole provided with sculpted patterns having edges for cutting or breaking liquid films which may cover a surface intended for use by pedestrians. These patterns typically include lugs of elastomeric material, such as rubber, juxtaposed in the surface of the sole so as to cover, for example, the whole of the part supporting the front part of the foot, and, in some cases, the whole surface of the heel as well. These blocks are square and are arranged diagonally; that is to say, each block has a diagonal running in the longitudinal direction of the sole. The blocks are aligned to form rows separated by narrow grooves of uniform width which thus form a network of channels intersecting at right angles. Each lug is also divided into four parts by two slits (or “sipes”, as they are commonly known) positioned at right angles and parallel to the edges of the lug, thus forming four elementary blocks. These slits are intended to increase the transverse suppleness or flexibility of each lug of the sculpture and therefore of the sole in general, thus contributing to the breaking of the liquid films. Preferably, the depth of each slit is less than that of the grooves and even more preferably it is in the range from 20% to 80% of the depth of the grooves.
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.

BRIEF DESCRIPTION OF THE INVENTION

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 FIG. 1. The multiple tips terminating the stems of the lugs provide an unusual and unexpected sensation of softness combined with roughness and of “velvety” adhesion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a sculpture of the sole of slip-resistant footwear according to the prior art.

FIG. 2 is a plan view of a first example of a sculpture according to the invention for a slip-resistant sole.

FIGS. 3A and 3B are two illustrations, one in a plan view and the other in perspective, of sculpted patterns according to the invention organized in a different arrangement from that of FIG. 2.

FIG. 4A shows a detailed plan view of a lug of the sculpture of FIG. 3, FIG. 4B shows schematically a profile view of this lug, and FIG. 4C shows a possible position of this lug in a slip-resistant sole.

FIG. 4D shows three sculpted lugs of a sole, illustrating the stem-to-recess coupling.

FIG. 5 is a detail view of the arrangement of the lugs of FIGS. 3 and 4 in a circular portion of sole V-V identified in FIG. 6,

FIG. 6 is a plan view of the general appearance of a sculpture formed by means of the lugs of FIGS. 3 to 5 in a sole of footwear.

FIGS. 7A, 7B, 7C and 7D show four variant embodiments of a sculpture using lugs similar to those of FIGS. 4A and 4B.

FIGS. 8A and 8B are more detailed illustrations of an embodiment of a footwear sole using the sculpted pattern of FIG. 2, FIG. 8A being a three-quarter view from above while FIG. 8B is a perspective wire drawing.

FIG. 9 shows another embodiment of a surface offering slip-resistant properties with a variant of the sculpture according to the invention.

FIGS. 10A to 10F illustrate the explanations of a problem concerning the trapping of foreign bodies in the grooves between the lugs of a footwear sole,

FIGS. 11 and 12 show schematically two solutions to this problem according to the invention.

FIGS. 13A, 13B and 13C show plan views of the implementation of three anti-trapping solutions in an arrangement of lugs with stems according to the invention,

DESCRIPTION OF ONE OR MORE EXAMPLES OF EMBODIMENT

A sole sculpture is shown in FIG. 1, which reproduces, approximately at least, that of the model document filed in the United States under the number US D446912S, mentioned at the beginning of this text as an illustration of the prior art. It is composed of square rubber lugs 11, which project towards the lower face of the sole from a substrate 12 which has a thickness and suppleness suitable for the intended use of the sole. Each of the lugs 11 is divided into four elementary blocks 14 by two slits or sipes or indentations 15 intersecting at right angles. The lugs 11 are separated from each other by two sets of orthogonal grooves 16 parallel to the slits 15, which have suitable dimensions to allow a good flow of the liquid displaced by the sole in contact with the ground. The width of these grooves is normally several times the width of the internal slits 15 of each lug 11.
In FIG. 1, the longitudinal direction of the footwear is orientated from the bottom to the top of the page. Each of the blocks therefore has a diagonal in the longitudinal direction L of the footwear. The blocks 11 form parallel lines in this direction. The diagonals of each line are aligned. Each block has a rubber tip at each of its front and rear ends on this diagonal, each of these tips forming a point of concentration of stresses perpendicular to the ground under the weight of a user, which can break a film of liquid covering the surface of the ground. Similar tips are aligned in the direction l perpendicular to the longitudinal direction L. The arrangement described above has some merits but may still have insufficient grip in some cases. This is because the penetration of the liquid film by the lugs of the sculpture is not always effective and is not followed by sufficient wiping of the surface of the ground to drive away the surface liquid which is being covered by the lug in question and thus to establish a dry contact with the ground, which is necessary in order to achieve a good grip and prevent slipping.
FIG. 2 shows an embodiment of a sculpture which uses the principles of the invention, in which each rubber lug 21 projecting from a sole substrate has the shape of a star with six arms, each of which terminates in a stem 22 directed towards the outside of the lug 21. The embodiment of these lugs is detailed below. It will be noted that, if the longitudinal direction of the footwear (indicated by the arrow L) extends from the bottom to the top of the page, the lugs form alignments in this direction. Each alignment is separated from the neighboring alignment by a groove 24 with an undulating profile. The lugs 21 are also aligned in the direction (indicated by the arrow 1) perpendicular to the longitudinal direction L and form rows separated from each other by a set of undulating grooves 25 in this direction.
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 FIG. 3, using the same conventions concerning the orientation of the pattern with respect to the longitudinal direction L and transverse direction l of the sole, we find that in this example each lug 31 in the form of a star with six arms has two stems 32 orientated mainly longitudinally, in both of its directions, and one stem 33 which is orientated transversely, again in both of its directions. However, if the lugs 31 are aligned as described below, the two alignment networks which they form are not longitudinal and transverse. As explained above, the stems 32 can provide a concentration of stresses on the ground surface and on any impurities covering it, such as films of water, oil or blood. With this arrangement, the density of stem tips capable of initiating the piercing of a slippery coating or film covering the surface of the ground in response to a mainly longitudinal force is higher than in the preceding arrangement in which the orientation of the lugs was different. The advantage of this arrangement is that it produces grooves having a relatively constant cross section. For low rates of surface indentation, this arrangement is preferred for reasons of ease of flow of the contaminants (which are substantially fluids). FIG. 3B provides a clearer idea of the appearance of a slip-resistant surface constructed according to the invention.
With reference to FIG. 4A, it can be seen that a lug 31 of the sculpture of FIG. 3, having six stems such as 32 and 33, is divided into three elementary blocks 36 by three slits 34 proceeding radially outwards from the centre 37 of the lug 31. Each of these slits 34 opens into a groove 35 separating the lug 31 from its neighboring lugs at a recessed point 38 located at the junction of two adjacent stems 32 or 33 on the profile of the lug 31. Each elementary block 36 has two adjacent stems 32 or 33 positioned in a chevron pattern. FIG. 4B is a sectional view of the lug 31 of FIG. 4A which projects from a substrate or support 30 of a footwear sole. The slits 34 which divide the lug 31 meet at its centre 37 in a single slit, visible at 37 in FIG. 4B. It will also be noted that the depth h of the slits such as 34 is smaller than the depth 11 of the grooves 35.
A profile of a footwear sole 41 according to the invention is shown in FIG. 4C, in which a lug pattern 31 as described previously has been deliberately enlarged to emphasize the orientation of the stems 32 and 33 with respect to the longitudinal direction L and the transverse direction I.
FIG. 5 shows the mutual arrangement of the six-stemmed lugs of the type discussed in the preceding examples. The reference numbers used in FIGS. 3 and 4 have therefore been used again. If we refer to a lug 31-A in FIG. 5, its stem 32-1 which has one edge parallel to the direction L “penetrates” into a hollow or recess formed between two stems 32-3 and 32-4 of a lug 31-B neighboring the lug 31-A in the direction L. Conversely, the stem 32-4 of this lug 31-B points in the direction L, but in the opposite direction, and “penetrates” into the hollow formed between the two stems 32-1 and 32-2 of the lug 31-A. There is thus a kind of incomplete nesting between the lugs 31-A and 31-B which is repeated for all the other lugs of the sculpture in this direction. The same observation can be made in respect of the stems 33 in the transverse direction l.
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.
FIG. 5 is an enlargement of the sculpture contained in a circular sector identified by V-V in, FIG. 6, which is a more general illustration of a portion of sole provided with the same pattern. FIG. 6 also shows that the lugs 31 are in fact strictly aligned; that is to say, the pattern of each lug can be obtained by simple displacement or translation of another lug in the same line. In the case of FIG. 6, the lugs of the sculpture are aligned in two directions identified by the arrows 45-45 and 46-46. The direction 45-45 lies at an angle of sixty degrees to the direction 46-46, and neither of these two directions coincides with either of the principal directions L and l of the sole. This enables the regularity of the width of the hollows or grooves between the patterns to be optimized to a certain degree. Other examples of optimization of the uniformity of the grooves for each pattern are described below together with the adjustment of the orientation of the stars with respect to each other (FIGS. 7A and 7B). The choice of the number of slits in each sculpted lug and their orientations within each star also provides a factor for adjusting the performance of the sculpture.
Returning to FIGS. 4A, B and C, we can explain the operation of the sculpture described here, by considering the example of a user taking one step forward. A lug 31 makes contact with the ground from the back to the front, and the two backward-facing stems 32 of the sole begin to be compressed under the weight of the walker. The compression progresses towards the wider part of the stem. If the tip 41 of a stem 32 located towards the rear of the lug 31 of FIG. 4A pierces the film of impurities and makes contact with the dry surface of the ground, then the edges 42 and 43 of the stem cut the film as the stem is compressed. The stem 41 of FIG. 4A belongs to an elementary block 36-1 which includes a second stem and is separated from the other elementary blocks 36 of the lug 31 by a chevron-shaped slit 34. Under the pressure transmitted by the compression of the rubber of this lug, the foreign substances of the film located under the stem 41 are driven forwards and also to the side, towards the surrounding groove, and the rubber of the lug progressively establishes a dry contact with the ground. This results in an increased grip. It should also be noted that, when the compression of the rubber progresses towards the centre of the lug 31, the rubber edging the slit or sipe 34 expands and closes this sipe. The elementary block 45 bears against the walls of the other two adjacent elementary blocks of this lug, thus limiting the deformation of the lugs and allowing the dry contact established in this way to be maintained with sufficient contact pressure. The operation indicated above is the same in all directions.
With reference to FIG. 4D, we shall now explain the meaning of a “stem-to-recess coupling” in this case. This FIG. 4D shows three lugs 211, 212 and 213, each having the shape of a regular star with six arms or stems whose ends which are radially farthest from the geometric centers P1, P2 and P3 of said lugs are located on a circle (C1, C2 and C3 respectively) circumscribing each lug. It can be seen that the lug 212 is in a coupling relationship with the lug 211, since one of its stems 212E is close to a recess 211R formed between two stems 211E of the lug 211 and is inside the circle C1 circumscribing said lug 211. Similarly, the lug 213 is in a coupling relationship with the lug 212 because one of its stems 213E is positioned in a recess 212R and is inside the circle C2 circumscribing the lug 212. In the limiting case, the lug 211 has a stem 211E′ whose end is placed on the circle C2 circumscribing the lug 212.
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. FIG. 10A shows a section of sole having two lugs 88A and 89A separated by a groove 90A. The width of this groove with respect to its depth is such that no foreign body such as a stone can remain trapped in the groove for a long time. FIG. 10B shows the opposite case in which the groove 90B is deeper and narrower than the groove 90A. Clearly, a pebble 93B can easily remain trapped, possibly for a long time, before it is eventually released as a result of the various forces to which the sole is subjected in use. In the latter case, the presence of a pebble will affect the slip-resistant performance on slippery ground. FIG. 10C shows a view from above of the portion of sole of FIG. 10B with a groove 90C running along the edges of two thick parallel lugs which exerts balanced forces on both sides of the pebble 93C, which is trapped in the groove. By contrast, FIG. 10D shows an identical situation with a groove bordered, in an arrangement according to the invention, by two stems 88B and 89D positioned substantially in a head-to-tail configuration. It will be clear from this drawing that a pebble such as 93D trapped in the upper part of FIG. 10D is subjected to unbalanced lateral forces from the walls of the groove 90D during walking. This unbalance causes the pebble 93D to be expelled rapidly from the groove 90D. This is also true in the other illustrated case in which the pebble 93′D is trapped in the lower part of the groove 90D in FIG. 10D; the stresses exerted by the stem 89D, which is thicker at the position of the pebble, are greater than those of the stem 88D which is thinner, and sooner or later the pebble will be released.
FIG. 10E shows an arrangement according to a variant of the invention for helping to prevent the retention of pebbles. The walls 91E and 92E of the groove 90E are inclined at a taper angle, when viewed towards the upper part of the drawing; the taper angle, measured with respect to a line perpendicular to the contact surface of the lug, is more than 0 degrees. They form an obtuse angle with respect to the base 80E. The pebble 93E trapped in a funnel shape tends to be driven towards the outlet from the groove by the inclined walls. A similar result is obtained in the case of FIG. 10F, in which the base of the groove is provided with an elastomeric boss 94F which acts as a stone removing device against any object such as 93F which may be trapped between the walls 91F and 92F. This last arrangement is particularly suitable for spaces where it is not easy to create tapers, for example at an intersection of grooves, as described below,
FIG. 11 is a schematic perspective view of a set of two stems 96-1, bordered by a wall 95-1 inclined at a constant taper angle, and 96-2, bordered by a groove wall 95-2 which is also inclined at a constant taper angle. The two stems are positioned head-to-tail according to the arrangement of the invention and are separated by a groove. FIG. 12 shows schematically, in a plan view, that it is possible, and may be advantageous, to create walls 99 whose taper angle varies along the groove 97 which they delimit. In the illustrated case, the taper angle of the wall increases along the groove up to the end of the stem,
FIGS. 13A, 13B and 13C are plan views similar to those of FIGS. 2, 3, 6 and 7, for example, in which the walls of the grooves between the lugs have a constant taper angle in the variants shown in FIGS. 13A and 13C, and a variable taper angle in FIG. 13B. The layouts of said walls in the base of the sole which defines the base of each groove are visible at 180 and 181 between the lugs 182 and 183 in FIG. 13A, and at 190 and 191 between the lugs 192 and 193 in FIG. 13B. FIG. 13C shows the layout of a stone removing device 195 formed at the intersection of the grooves where a substantial space on the base of the sole is left uncovered by the inclined walls of the grooves.
FIGS. 7A, 7B, 7C and 7D show some possible variant embodiments of the preferred arrangement described with reference to the preceding drawings, provided, notably, for the purpose of adapting the rate of indentation of the sculpture according to the invention. Thus, in FIG. 7A, a lug pattern forming a star with six arms 51, identical to that of FIGS. 3 to 6, is treated differently in the sense that each star has one stem 52 pointing along the axis L and two stems 53 having principal components in the direction of the axis 1. It will be noted that the centers 57 of each group of three neighboring lugs 31 are located on the vertices of an equilateral triangle 58. This is comparable to the case of FIG. 5, in which the centers 37 of neighboring lugs 31 are located on an equilateral triangle 48 shown in mixed lines, whose sides are orientated at 45 degrees, 105 degrees and 165 degrees respectively with respect to the longitudinal direction L. In the arrangement of FIG. 7A, the sides of the equilateral triangle 58 have the same orientation as those of the triangle 48. However, the ratios between the distances of the centers of the lugs and the length (that is to say, the distance of the end of the stem from the centre of the lug) of their stems are different. Consequently, as can be seen, there is a greater separation between the edges of neighboring parallel stems on either side of a groove and a degree of narrowing of the channels formed by the grooves at the positions of the stem tips.
With reference to FIG. 7B, for lug patterns 61 which are again identical, it will be noted that their centers 67 are located on the vertices of equilateral triangles 68 whose sides lie at angles of 15 degrees, 75 degrees and 135 degrees respectively to the longitudinal direction L. Since the dimensions of the lugs 61 and the triangles 68 are identical to those of the lugs 51 and the triangles 58 of FIG. 7A, it is evident that the arrangement of FIG. 713 makes it possible to achieve virtually perfect uniformity of the width of the grooves of the sculpture, admittedly at a rate of indentation which is greater than that of FIG. 7A. The orientation of the meshing triangle of the lugs is therefore a useful parameter for adjusting the uniformity of the grooves and the rate of indentation.
FIGS. 7C and 7D show a method of decreasing the rate of indentation of the sculpture of the preceding FIGS. 3 to 6 and thus of increasing the density of the lugs by cutting back the tips of the stems while retaining a substantial groove width for the discharge of substances of the intermediate film which are to be removed. It would also be possible to round or blunt the stem tips to achieve the illustrated result. It will be noted that this arrangement is such that, with an arrangement identical to that of FIG. 7B, the size of the stars (i.e. the length of the stem E as defined above) can be increased as shown in FIG. 7C and even further as shown in FIG. 7D, in a case in which the discharge capacity required in the grooves is less important. It is known that the decrease in the rate of indentation is a factor allowing the contact pressure on the support surface to be decreased, if all other factors remain constant. In the case of a sole used on a ground, this enables the grip to be increased in dry contact conditions while simultaneously decreasing wear. These aspects of performance are generally considered to be the predominant ones in the design of slip-resistant applications.
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 FIG. 1. The multiple tips terminating the stems of the lugs provide an unusual and unexpected sensation of softness combined with roughness and of “velvety” adhesion.
Such an impression is provided, for example, with a sculpture such as that described with reference to FIG. 5 for a sole of work footwear made from rubber or other elastomeric material having an elastic modulus of rigidity of 2.7 MPa at an elongation of 10%. The distance between the tips of two opposing stems is 8 millimeters, and the angle of aperture of the stems is sixty degrees. The end of each stem is slightly rounded. In this example, the width of the slits 34 is 0.3 millimeters and their length is approximately 2 millimeters. The distance between two parallel edges of two lug stems bordering the same groove in FIG. 5 is 0.9 mm. The height of the sculpture (or the depth of the groove) is 3 millimeters, and the depth of the slits 34 is 2 millimeters. The rate of surface indentation in this example is 40 percent.
FIGS. 8A and 8B show an arrangement of the pattern in the form of a star with six arms of FIGS. 4A and 4B which is appropriate for improving the isotropy of the grip properties of the sculpture. Each lug 81 has six arms terminating in the form of stems. With reference to one of the lugs 81-1, we can identify two neighboring stems 82-1 and 83-1 belonging to two separate elementary blocks 86-A and 86-B in the lug 81-1. If we now examine one of the neighboring lugs, 81-2, on the right of FIG. 8A, and look at the stems 82-2 and 83-2 of the corresponding two elementary blocks 86-A and 86-B of the lug 81-2, we can see that they have been formed by the displacement of the layout of the lug 81-1 including a translation of this layout towards the upper left-hand side of the drawing and a rotation about the axis of the lug through an angle of 30. Similarly, FIG. 8A shows that the lug 81-3 can be formed by translation of the layout of the lug 81-2 in the same direction and rotation by 30° about its axis. The neighboring lugs 81-1 to 81-3 located on an alignment from the right to the upper left therefore have stems orientated in different directions. The same structure is found in the alignments located immediately below and above in FIG. 8A. Thus this structure can be used to multiply the directions of force in which the lugs can act with maximum effectiveness to bite into a skin or film of material interposed between the sole and the ground.
FIG. 8B is a more detailed view of the composition of a lug 81-1 projecting from the substrate of the sole 80, with its stems 82-1 and 83-1 and with slits 84-1 which are not as deep as the grooves 85-1. It will be noted that each lug such as 81-1 has two opposing stems pointing towards two recesses 88-1 and 88-2 belonging to two neighboring lugs, one on each side of the lug 81-1 in the same alignment (in this case from the right to the upper left side). Conversely, the lug 81-1 has two opposing recesses 88-3 and 88-4 which are pointed to by two stems of the neighboring lugs on either side of the lug 81-1 in a second alignment (in this case from the lower right to the top of FIGS. 8A and 8B).
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 FIGS. 7C and 7D, it can be seen that each star-shaped lug 71 has six radial slits 74 similar to the slits 34 of FIGS. 3 to 5, meeting in the centre 75 of each lug 71.
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. FIG. 9 shows an embodiment of a sculpture with lugs in the form of stars with six arms of the type shown in the preceding FIGS. 3 to 5, between which there are interleaved lugs 92 which have an equilateral triangular profile and which are inserted into the sculpture. Each of these lugs 92 therefore has three vertices 96 engaging in spaces formed by recesses 98 between the stems of the lugs 91, and each of these lugs is also provided with three slits or sipes meeting in the centre of the lug 94.
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.

Claims

1- A footwear comprising a sole having a base of elastomeric material of which at least one area is provided with contact lugs which emerge from its lower face so as to come into contact with the ground, and in which these contact lugs are separated from each other by grooves delimiting stems at angles of less than 75 degrees in each contact lug, the contact face of each lug being in the shape of a star with at least five arms distributed over the profile of the contact face, each stem being separated from its neighbor on the lug by a recess pointing towards the centre of the star shape, this sole being 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 of a first stem to a recess separating two neighboring stems in the profile of a second contact lug neighboring the first lug in said area; that is to say, the end of this first stem is positioned inside a circle circumscribing the second lug, and wherein each lug has at least one slit in the thickness of the lug, opening on to its contact surface, each slit having two ends, one of these ends opening into a recess.

2- The footwear according to claim 1 wherein each lug has a plurality of slits and these slits have common ends located within said lug.

3- The footwear according to claim 2 wherein the depth of each slit is between 20% and 80% of the depth of the grooves separating said lugs.

4- The footwear according to claim 3 wherein, in at least one portion of the sole, the orientations of the slits of one lug are offset angularly with respect to the slits of at least one of the neighboring lugs.

5- The footwear according to claim 1 wherein each first lug in the area has:

(i) at least two couplings of its stems to recesses separating neighboring stems in the profile of neighboring lugs, and

(ii) at least two couplings of its recesses between neighboring stems in its profile to stems of neighboring lugs.

6- The footwear according to claim 5 wherein each first lug in the area is surrounded by a set of at least four lugs distributed over its circumference, each of which is associated by a stem-to-recess coupling with the lug surrounded by this set.

7- The footwear according to claim 1 wherein, in at least one area of the sole, each lug (31) can be inscribed in a circle having a diameter of less than 20 millimeters.

8- The footwear according to claim 7 wherein each lug (31) can be inscribed in a circle having a diameter of not more than 10 millimeters and not less than 4 millimeters.

9- The footwear according to claim 1 wherein, in at least one portion of the sole, the star shapes of the neighboring lugs have their orientations offset angularly from each other.

10- The footwear according to claim 1 wherein each stem is delimited by the walls of two grooves and in that the wall of at least one groove separating a stem of a first lug engaged in the recess of a second lug is inclined with respect to the base of the sole at a taper angle of more than 0 degree, this taper angle being measured with respect to a line perpendicular to the contact surface of the lug.

11- The footwear according to claim 10 wherein the taper angle of the wall increases along the groove up to the end of the stem.

12- The footwear according to claim 1 wherein the sole comprises at least one boss acting as a stone removing device, this boss projecting from the base at the intersection of at least two grooves delimiting the ends of two stems.