WO2025098916A1

WO2025098916A1 - A shoe comprising a slip portion

Info

Publication number: WO2025098916A1
Application number: PCT/EP2024/081020
Authority: WO
Inventors: Thor Buch GRØNLYKKE
Original assignee: Spraino IP ApS
Current assignee: Spraino IP ApS
Priority date: 2023-11-06
Filing date: 2024-11-04
Publication date: 2025-05-15
Anticipated expiration: 2026-05-06

Abstract

A shoe, such as a safety shoe or an occupational shoe, with a tip portion (110) at its forward end and a heel portion at its backward end comprises a shoe upper, and a sole (102) comprising an outsole (104) with a ground-engaging surface (106) for engaging the ground. A tip portion the shoe defines a slip portion (112) having an outwardly-facing surface (114) with a low coefficient of friction, and at least a portion of the ground-engaging surface of the sole in the vicinity of the tip portion of the shoe defines a high coefficient of friction. The outwardly-facing surface of the slip portion does not lie flush with the ground-engaging surface of the outsole when seen in a longitudinal cross-section through the shoe. The slip portion provides the shoe with a tip of low friction material that will have contact to an obstacle or the ground in the event of an adverse event during the swing phase of the gait cycle.

Description

A SHOE COMPRISING A SLIP PORTION

FIELD OF THE INVENTION

The present invention relates to a shoe, such as a sport shoe, tailored to reduce the risk of injuries, compensate disability and enhance performance.

BACKGROUND OF THE INVENTION

From a shoe design point of view, prevention of injuries has hitherto generally focused on enhancement of foot support, as well as on improvement of anti-slip properties of shoes. Despite past efforts, it has however been found that a need remains for further development of a shoe which contributes to reducing the occurrence of injuries and to reduce disability.

The invention is developed to prevent falls and alleviate disability from ground contact that impedes gait. Falls are globally a major public health problem for people with various gait impairments (disabilities, diseases, age, pressure related pain, overuse injuries) and often has many consequences for both the individual and the public. The personal consequences can be fractures which results in long recoveries, and a worsening of life quality. In some cases, a fall can even result in fatality due to head trauma or long recoveries. The fear of falling is also limiting and affects both the person at risk and the relatives. Besides the personal consequences, treatment of a fall has high costs for society and the healthcare system.

Falls in workplaces is a leading cause of acute injury for workers and has an added risk since the falls often happen in a less secure environment. Despite many efforts to make workplaces safer, there are still a considerable burden of injury from these accidents.

Falls often occur due to tripping, which is characterized by unanticipated increased braking force in the anterior region of the shoe and sole. This typically happens when overlooking an obstacle or hitting the ground with the tip of the shoe when correcting your walk as a result of a perturbation or decreased toe clearance. The resulting brake force results in overbalance. If the brake force reaches a certain threshold, the forward propulsion exceeds the compensatory mechanism for regaining control over your balance and will result in a fall.

For persons with reduced toe-clearance, there is a risk of tripping but also gait difficulty arising from unwanted friction in the push off phase and during the swing phase. This may lead to a shuffling gait and difficulty walking outside or other severe limitation in daily activities. In some instances, it can make rehabilitation more difficult and require more aid and thereby reduce autonomy. A less safe shoe and more obstructive shoe can therefore increase the time of the rehabilitation.

In the typical swing phase, there is a plantar flexion of the foot and contact with the ground around mid-swing will often lead to a contact with tip of the shoe at an angle that is not flush with the outsole. This is more so, if the person has a foot drop condition.

Description of the invention

In a first aspect the present invention provides a shoe with a tip portion at a forward end of the shoe, a heel portion at a backward end of the shoe, a lateral edge extending between the tip portion and the heel portion, and a medial edge extending between the tip portion and the heel portion, the shoe extending longitudinally between the heel and tip portions and comprising :

- a shoe upper;

- a sole comprising an outsole with a ground-engaging surface for engaging the ground; and wherein: a tip portion the shoe defines a slip portion having an outwardly-facing surface with a first coefficient of friction;

- at least a portion of the ground-engaging surface of the sole in the vicinity of the tip portion of the shoe defines a second coefficient of friction;

- wherein the first coefficient of friction is smaller than the second coefficient of friction; and wherein the outwardly-facing surface of the slip portion does not lie flush with the ground-engaging surface of the outsole when seen in a longitudinal cross-section through the shoe.

The slip portion provides the shoe with a tip of low friction material that will have contact to an obstacle or the ground in the event of an adverse event during the swing phase of the gait cycle. Due to the low friction coefficient of the outwardly-facing surface of the slip portion the friction between the shoe and the obstacle is low, and hence the braking force will be lower and the deceleration of the lower limb will be less. If the stiffness of the lower limb joint is high, a propulsion of the upper limb will also be reduced.

In the present context, the configuration of the slip portion and the outsole to the effect that the outwardly-facing surface of the slip portion does not lie flush with the ground-engaging surface of the outsole when seen in a longitudinal cross-section through the shoe may be understood to mean that a surface formed by a lower extremity of the slip portion extends discontinuously with respect to the ground-engaging surface of the outsole at a transition between the outsole and the slip portion. As such, in the longitudinal cross-section through the shoe, a curvature or line formed by the outwardly-facing surface of the slip portion does preferably not form a mathematical, i.e. algebraic continuation of a curvature or line formed by the ground-engaging surface of the outsole. For example, at (or in the vicinity of) the transition between the outsole and the slip portion, the ground-engaging surface of the outsole may define a first line or curvature in the longitudinal cross section, whereas at (or in the vicinity of) the transition the outwardly-facing surface of the slip portion may define a second line or curvature in the longitudinal cross section, the first line or curvature having a tangent at the transition with a first slope, and the second line or curvature having a tangent at the transition with a second slope different from the first slope. Alternatively, or additionally, the transition between the outsole and the slip portion may form a step in the sense that the outwardly-facing surface of the slip portion may upwardly offset with respect to the ground-engaging surface of the outsole.

The outwardly-facing surface of the slip portion may be upwardly offset with respect to the ground-engaging surface of the outsole. It may thus be ensured that the ground-engaging surface of the outsole comes into contact with ground during normal gait, so that the non-slip surface only - or predominantly - engages obstacles or elevations in the ground.

The reduction in braking force may further be determined by an angle defined by the slip portion, i.e. an angle defined in the low friction portion. The angle of the shoe tip in anterior- posterior direction can be defined so that if the tip is extended straight anteriorly from the ground-engaging outsole surface, it has a 0 degree angle. Thus, if an angle is 90 degrees or lower, an upper portion of the tip is anterior to a lower portion of the tip near the ground. Tests have shown that the breaking force is particularly reduced at angles of the shoe tip below 80 degrees.

By having a construction with a 90 degree or lower shoe tip angle ("functional angle"), that is when the outwardly-facing surface of the slip portion is upwardly inclined relative to the ground-engaging surface of the outsole, a further reduction of braking force is achieved and self-locking to obstacles can be avoided.

In one embodiment, the slip portion, non-slip portion and/or an interface between the two may be configured such that a lower portion of the slip portion is allowed to flex backwards to a greater extent than an upper portion of the slip portion. Thereby, the functional angle further decreases with pressure. This can be achieved by higher stiffness in the shoe construction behind the outwardly-facing upper portion of the slip portion than in its lower portion. This also has the effect that horizontal forces can be transferred to a vertical force in the respective portions. This will increase the lift provided by the shoe while reducing the braking force.

The shoe may further comprise a non-slip portion at or in the vicinity of an upper transition between the slip portion and the shoe upper, wherein the non-slip portion

- defines an upwardly- or forwardly-facing outer surface of the shoe at or in the vicinity of the upper transition between the slip portion and the shoe upper; has an outer surface friction coefficient greater than the first coefficient of friction; and is backwardly offset with respect to a foremost extremity of the slip portion.

The non-slip portion is preferably placed on the top of the shoe tip. This part of the shoe will thereby have the required friction/traction to stabilize the wearer when sitting on the knees. The non-slip portion is preferably placed so that it does not come in contact with an obstacle in a collision during the swing phase of the gait cycle which would increase the braking force. It is therefore desirably placed behind a 90 degrees vertical line of the most anterior tip of the slip portion of the shoe tip. The non-slip portion can be one large area or made up of several adjacent areas to ensure that the contact in knee-sitting position is with the non-slip portion if the foot is more plantar flexed and more internally or externally rotated.

The non-slip portion, the slip portion and/or an interface between the two are mutually arranged and configured such that the non-slip portion supports the slip portion in the longitudinal direction at or in the vicinity of the upper transition between the slip portion and the shoe upper.

When the slip portion is imparted by a longitudinal force in the backward direction, the nonslip portion and/or an element interconnecting the slip portion and the non-slip portion provides a reaction force in the forward direction.

For the provision of the desired reaction force, the slip portion may be made from a material composition having a first Young's Modulus, and the non-slip portion and/or an element interconnecting the slip portion and the non-slip portion may be made from a material composition having a second Young's Modulus greater than the first Young's Modulus.

The element interconnecting the slip portion and the non-slip portion may be integrally formed with either one of the slip portion and the non-slip portion. The non-slip portion and the outsole may conveniently be made from the material composition to facility production and reduce manufacturing costs.

Embodiments of the shoe according to the present invention may be configured as a safety shoe in accordance with ISO 20345:2021 or as an occupational shoe in accordance with ISO 20347:2021.

The first coefficient of friction may be less than 0.5 as tested according to ISO 13287:2019 by mounting the surface of the area of reduced friction on the sole of the test shoe and using the backward slip on the forepart test without lubricant as according to ISO 13287:2019.

The second coefficient of friction may be more than 0.55 as tested according to ISO 13287:2019 by mounting the surface of the area of reduced friction on the sole of the test shoe and using the backward slip on the forepart test without lubricant as according to ISO 13287:2019.

The slip portion and/or the non-slip portion may be formed integrally with the remainder of the shoe, or they may alternatively be defined by separate elements bonded to a surface of the remainder of the shoe. A plurality of separate, distinct slip and/or non-slip portions may be provided along a tip portion of the shoe in close abutment with one another, or with mutual distances.

Brief description of the drawings

Embodiments of the invention will now be further described with reference to the drawings, in which:

Fig. 1 illustrates a sole for a shoe, including an element at a tip portion of the shoe, the tip portion having a slip portion with reduced friction;

Figs. 2a and 2b show first and second embodiments of an element for a tip portion of an embodiment of a shoe;

Fig. 3 shows a third embodiment of an element for a tip portion of an embodiment of a shoe;

Fig 4 is cross-sectional view of an embodiment of a sole of a shoe and an embodiment of an element at a tip portion of the shoe;

Fig. 4A illustrates a detail of the cross-sectional view of Fig. 4; Figs. 5 and 6 illustrate dimensions of the embodiment of Fig. 4.

Detailed description of the drawings

It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Fig. 1 illustrates a sole 102 for a shoe, comprising an outsole 104 with a ground-engaging surface 106. The shoe comprises an element 108 at a tip portion 110 of the shoe, wherein the tip portion 110 defines a slip portion 112 with an outwardly-facing surface 114 with reduced friction. More specifically, the outwardly-facing surface 114 of the slip portion 112 defines a first coefficient of friction which is smaller than a second coefficient of friction defined by the ground-engaging surface 106 of the sole 104 in the vicinity of the tip portion 110 of the shoe. The sole 102 and element 108 are shown in a longitudinal cross-sectional view in Fig. 4. Fig. 4A shows a detail of Fig. 4.

The outwardly-facing surface 114 of the slip portion 112 does not lie flush with the groundengaging surface 106 of the outsole 102. More specifically, a step is formed in the illustrated embodiment at a transition between the outsole 102 and the slip portion 112 in the sense that the outwardly-facing surface 114 and the slip portion 112 are upwardly offset with respect to the ground-engaging surface 106. Alternatively, or additionally, as shown in the detail in Fig. 4A, at (or in the vicinity of) the transition between the outsole 102 and the slip portion 112, the ground-engaging surface 106 of the outsole 102 may define a first line or curvature in the longitudinal cross section, whereas at (or in the vicinity of) the transition the outwardly-facing surface 114 of the slip portion 112 may define a second line or curvature in the longitudinal cross section, the first line or curvature having a tangent at the transition with a first slope, and the second line or curvature having a tangent at the transition with a second slope different from the first slope. Thus, as illustrated in Fig. 4A, at the transition, a tangent of the slip portion 112 defines an angle Vi with respect to a tangent of the outsole 106.

As shown in Figs. 2-6, a non-slip portion 116 is provided in the vicinity of an upper transition between the slip portion 112 and the shoe upper (not shown). The non-slip portion defines an upwardly-facing outer surface 118 of the shoe in the vicinity of the aforementioned upper transition with a coefficient of friction greater than the coefficient of friction defined by the coefficient of friction defined by the outwardly-facing surface 114 of the slip portion 112. The non-slip portion 116 may preferably be defined by and form a surface of the element 108 at the tip portion 110 of the shoe which defines the slip portion 112.

Figs. 2a, 2b and 3 show respective embodiments of the element 108 for defining the outwardly-facing surface 114 of reduced friction. In Fig. 2b, the element 108a with outwardly-facing surface 114a are shaped slightly differently from the embodiment of Fig. 2a, but otherwise element 108a is functionally identical to element 108. The element 108 and thus the slip portion 112 may be formed integrally with the remainder of the shoe, or it may be provided as a separate element to be bonded to a surface of the remainder of the shoe. In the exemplary embodiment shown in the drawings, a single element 108 is provided which covers a significant portion of the tip portion of the shoe. Alternatively, a plurality of elements may be provided, each of which covers only a part of the tip portion, the elements being provided in close abutment with one another or at mutual distances. For example, two to eight, such as three, four or five separate elements may be distributed across the tip portion of the shoe to jointly extend over approximately the same span as the element 108 shown in Figs. 1-3. In order to provide sliding friction at an upper portion of the slip portion 112, friction portions 115 may be provided at a transition between upwardly and longitudinally extending surfaces of the element 108. Alternatively, the portions 115 may be low-friction portions which have a reduced surface friction compared to the surface friction of the outwardly-facing surface 114 of the slip portion 112. The portions 115 may supplementarily, or alternatively, have reinforcing and/or decorative purposes.

Figs. 5 and 6 illustrate dimensions of the embodiment of Fig. 4. As shown, the outwardly- facing surface 114 of the slip portion 112 may form an acute angle V₂ relative to vertical. As shown, the upwardly-facing surface 118 of the non-slip portion 116 has a rear portion 122 and a connecting portion 120 connecting the rear portion to an upper apex of the element 108. The rear portion 122 and the connecting portion form an obtuse angle V₃.

The element 108 defines a height H in a vertical direction between the rear portion 122 and a lower extremity of the slip portion 112. The slip portion 112 may be longitudinally offset by a distance D from a forward extremity of the sole 102.

Embodiments and features of the invention are further disclosed and discussed in the article by Munk-Hansen, Holsgaard-Larsen, Gronlykke, de Zee and Madeleine "Can shoe tip modifications on safety shoes reduce the braking forces in a trip-simulating, free-body shoe collision test", Footwear Science, Taylor & Francis Online, https://www.tandfonline.com/doi/full/10.1080/19424280.2024.24Q7795, published on 27 September 2024.

Claims

1. A shoe with a tip portion at a forward end of the shoe, a heel portion at a backward end of the shoe, a lateral edge extending between the tip portion and the heel portion, and a medial edge extending between the tip portion and the heel portion, the shoe extending longitudinally between the heel and tip portions and comprising :

- a shoe upper;

2. A shoe according to claim 1, wherein the outwardly-facing surface of the slip portion is upwardly offset with respect to the ground-engaging surface of the outsole.

3. A shoe according to claim 1 or 2, wherein the outwardly-facing surface of the slip portion is upwardly inclined relative to the ground-engaging surface of the outsole.

4. A shoe according to any of the preceding claims, further comprising a non-slip portion at or in the vicinity of an upper transition between the slip portion and the shoe upper, wherein the non-slip portion

- defines an upwardly- or forwardly-facing outer surface of the shoe at or in the vicinity of the upper transition between the slip portion and the shoe upper;

- has an outer surface friction coefficient greater than the first coefficient of friction; and

- is backwardly offset with respect to a foremost extremity of the slip portion.

5. A shoe according to claim 4, wherein the non-slip portion, the slip portion and/or an interface between the two are mutually arranged and configured such that the non-slip portion supports the slip portion in the longitudinal direction at or in the vicinity of the upper transition between the slip portion and the shoe upper.

6. A shoe according to claim 4 or 5, wherein the slip portion is made from a material composition having a first Young's Modulus, and wherein the non-slip portion and/or an element interconnecting the slip portion and the non-slip portion is/are made from a material composition having a second Young's Modulus greater than the first Young's Modulus.

7. A shoe according to any of claims 4-6, wherein the non-slip portion and the outsole are made from the same material composition.

8. A shoe according to any of claims 1-7, configured as a safety shoe in accordance with ISO 20345:2021 or as an occupational shoe in accordance with ISO 20347:2021.

9. A shoe according to any of the preceding claims, wherein the first coefficient of friction is less than 0.5 as tested according to ISO 13287:2019 by mounting the surface of the area of reduced friction on the sole of the test shoe and using the backward slip on the forepart test without lubricant as according to ISO 13287:2019.

10. A shoe according to any of the preceding claims, wherein the second coefficient of friction is more than 0.55 as tested according to ISO 13287:2019 by mounting the surface of the area of reduced friction on the sole of the test shoe and using the backward slip on the forepart test without lubricant as according to ISO 13287:2019.

11. A shoe according to any of the preceding claims, wherein the slip portion and/or the nonslip portion is/are formed integrally with the remainder of the shoe.

12. A shoe according to any of the preceding claims, wherein the slip portion and/or the nonslip portion is/are defined by separate elements bonded to a surface of the remainder of the shoe.