WO2015015477A1

WO2015015477A1 - Metal toe cap for safety footwear

Info

Publication number: WO2015015477A1
Application number: PCT/IB2014/063687
Authority: WO
Inventors: Sérgio LUÍS FERREIRA DA COSTA; Nuno RICARDO MAIA PEIXINHO; João PEDRO MENDONÇA ASSUNÇÃO SILVA
Original assignee: Universidade Do Minho; Icc - Indústrias De Comércio E Calçado, S. A.
Priority date: 2013-08-02
Filing date: 2014-08-04
Publication date: 2015-02-05
Also published as: EP3027074A1

Abstract

Metal toe cap for safety footwear including a top wall, a convergent U shaped side wall surface and a bottom wall for the tab region, defining a rear opening for receiving toes of a user. The toe cap is preferably made of the advanced high strength steel grade. The top wall surface combined with a portion of the forming side wall have two ribs shaped to maximize strain hardening properties of the material during the toe cap metal forming process, thus achieving higher strength in localized critical areas of the toe cap. Furthermore, a forward extension is designed in a manner that increases impact resistance in a critical area. The toe cap is manufactured in cold working advanced high strength steel that without complementary thermal treatments to obtain the necessary resistance to both static and impact loading. The safety performance and weight savings of a metal toe cap are improved.

Description

DESCRIPTION

METAL TOE CAP FOR SAFETY FOOTWEAR

Technical field

[0001] The present disclosure relates to a protection toe cap. In particular, the disclosure relates to a metal toe cap model for safety footwear comprising transversal ribs, providing better mechanical resistance to impacts or forces with a substantial weight reduction.

Background Art

[0002] In the field of accident prevention, footwear safety toe cap is well known for being arranged on the front part of the footwear itself, so as to satisfy the requirement of protecting the phalanges of the foot of an operator wearing it, more exemplified in the case of an object accidentally falling onto the foot, or generally, in the case of any occurrence that can subject the tip of the foot to high compression. Specifical ly, safety toe cap of the accident prevention footwear must meets specific mechanical strength requirements according to an extensive series of international standards, which order, amongst other things, the parameters of compression resistance and the impact energy that the aforementioned toe cap must withstands in order to be approved.

[0003] The European Standard requires the performance level of the toe cap component to be integrated into the footwear specimen, dealing with the particular impact and quasi-static compression resistance tests for the certification behaviour response, according to EN12568:2010.

[0004] Among other characteristics, toecaps for safety footwear must normally be able to withstand an energy impact of 200 joules and a compression force of 20 kN. These values are ensured by a structure in the shape of the tip of the footwear, ending in a lip or rim at the bottom of usually a maximum dimension of 10 mm, as shown in the prior art. Toecaps with this format are usually manufactured in the following materials: steel; nylon of the polymer family.

[0005] The mentioned integrated safety toe cap components represent mainly two distinct material and conceptual approaches: metallic and non-metallic models.

[0006] The conventional and traditional safety approach is made by the toecap family largely manufactured in steel and steel alloys usually applied with complementary heat treatments to perform the well-known and associated mechanical strength. This commitment to high structural mechanical behaviour was therefore identified for that type of construction approach. The enhancement of these features, very focused on strengthening models and their protection performances, is highlighted for instance by some applications respectively disclosed in the following documents: US-A 2006/0213086 and EP 1029463. The weight represented by these solutions when a steel unibody is the foremost disadvantage.

[0007] The current level and complexity related to most recent safety solutions and respective developments put emphasis not only in normative commitments but furthermore on the capacity of reducing the weight contribution in the safety footwear class. The toe cap is the heaviest integrant component contributing to approximately 35% of the average weight of a standard safety footwear model, with the particularity to be located in the region farthest from the ankle, and consequently generates the uppermost moment of force helping to make up user comfort parameters. Thus, several problems are inevitably associated with health and fatigue in extended footwear use.

[0008] Alternatively, non-metallic solutions from the representative polymer family have been commonly applied in lightweight reference solutions. Several polymeric models have been presented with the major purpose of weight reduction. The toe cap models disclosed in the documents US 6367170 and EP 2298112 exploited complex composite materials and hybrid structures to a substantial weight saving in comparison with previous metallic toe cap models. Despite of that, its main disadvantage still remains committed to the mechanical resistance behaviour with several problems concerning with stabilization of deformation responses for higher compression and impact load conditions. Consequently, those toe cap solutions are commonly connected to larger conceptual volumes and considerable thickness ranges of the component walls to counterpoise higher rates of deformation. In several ways that affects the global conception of the main integrant parts.

[0009] These facts are mentioned in order to illustrate the technical problem addressed by the disclosure.

Summary of the Disclosure

[0010] The disclosure comprises a metal toe cap for safety footwear, which includes an arcuate peripheral wall that tapers forward, a top wall, and a bottom wall, defining a rear opening for receiving toes of a user.

[0011] The toe cap is preferably made of advanced high strength steel characterized by high strength and positive properties of strain hardening and strain rate sensitivity.

[0012] The top wall and strategic portion of the arcuate peripheral wa ll have ribs defined in the geometry in a manner that maximizes strain hardening properties of the material during metal forming thus achieving higher strength in localized critical areas of the toe cap.

[0013] Furthermore, a forward extension of the stiffening elements is designed in a manner that increases impact resistance in a critical area through geometrical and material properties enhancement.

[0014] The toe cap may be manufactured in cold working advanced high strength steel that does not require thermal treatment to obtain the part resistance to static and impact loading prescribed in standards, i.e. safety footwear standards.

[0015] It is disclosed a metal toe cap for safety footwear comprising:

an arcuate peripheral wall that tapers to the front, a top wall and a bottom wall, which define a rear opening for receiving the toes of the footwear user;

two or more reinforcement ribs extending from the top wall to part of the arcuate peripheral wall, wherein said ribs are a transversal reinforcement of the top-wall and a reinforcement of transition of the arcuate peripheral wall to the top wall.

[0016] It is also described a process for obtaining a metal toe cap for safety footwear comprising:

shaping an arcuate peripheral wall that tapers to the front, a top wall and a bottom wall, which define a rear opening for receiving the toes of the footwear user;

shaping two or more reinforcement ribs extending from the top wall to part of the arcuate peripheral wall, wherein said ribs are a transversal reinforcement of the top-wall and a reinforcement of transition of the arcuate peripheral wall to the top wall.

[0017] In an embodiment, the reinforcement ribs are parallel and transversal in respect of the front-rear direction of the toe cap.

[0018] In an embodiment, the number of reinforcement ribs is 2 to 4, in particular 2, 3 or 4.

[0019] An embodiment further comprises a front reinforcement rib extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

[0020] In an embodiment, the reinforcement rib closest to the front of the toe cap is

"T"-shaped, having two lateral ends extending transversally in respect of the front-rear direction of the toe cap and having a front end extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

[0021] In an embodiment, the ribs taper to arcuate peripheral wall.

[0022] In an embodiment, the metal is Advanced High Strength Steel, AHSS, in particular having a yield strength in excess of 850MPa, further on particular having a yield strength in excess of lOOOMPa.

[0023] In an embodiment, the shaping of the metal toe cap is by cold forming process.

[0024] In an embodiment, the thickness of the metal toe cap is between 0.9mm and 1.5mm, in particular 1.0mm to 1.2mm.

[0025] In an embodiment, the thickness of the metal toe cap is uniform throughout the metal toe cap. [0026] In an embodiment, the bottom wall is a brim extending inwards from the bottom periphery of the arcuate peripheral wall.

[0027] The present disclosure, illustrated in Figures 1 and 2, refers to a metal toe cap component for safety footwear which can complement together the main features of the current solution trends.

[0028] The Advanced High Strength Steel - AHSS grades that gather specific properties and raise its performance to a model solution are performed, whereas the disclosed geometry and related engineering parameters contribute to bring this mechanical strength potential to a new level ahead.

[0029] AHSS are special alloys with ultimate tensile strength values normally above lOOOMPa, that show a superior mechanical strength comparing to conventional alloys, and potentiate the phenomenon of strain hardening of the material and the strain rate sensitivity in a controlled localized and specific geometry model, like that of the present disclosure, with a specific region coupled with a ribbed geometry model in order to better improve the structural deformation model.

[0030] The metal toe cap for safety footwear in accordance with the present disclosure combines a convergent side wall structure, contributing to a lower volume concept, with an exclusive top surface comprising, preferably, two specific and structural ribs of local hardening effect.

[0031] The metal toe cap solution does not require complementary processes of final heat treatments to achieve the respective impact and compression resistance performances. Instead, the advanced level of commitment to outperform previous strengthening states is here described and enhanced by an integrated approach of high strength steel alloys that gather specific properties with newness structural geometric re-design. The local stiffening effects extensively induced by a cold work hardening phenomenon, during the forming process of the new toe cap model, play a key role on the final material properties. All combined enable a controlled increase of the mechanical strength ratio in the range between 50 and 90%, when confronted to referenced solutions in steel and composite materials respectively. The potential for a full optimization of the component weight is thus exponentially improved, apart from others, with demonstrable environmental benefits.

[0032] Preferably, the metal toe cap assumes an uniform thickness range throughout the entire body portion.

[0033] The toe cap model envisaged in this disclosure has been developed to further reduce the component weight (by reducing its thickness), exceeding the reference values of the best polymeric solutions, with a weight reduction regarding the base steel model of around 40%. The optimization of not only the weight of metallic solutions but also the dimensional factors reported for the polymeric solutions, in the order of 30% - 35%, represent a definitive innovation and improvement regarding the performance of current state of the art solutions.

[0034] Further characteristics and advantages of the metal toe cap according to the present disclosure are detailed in conjunction with the accompanying drawings.

[0035] In an embodiment, the metal toecap comprises an arcuate peripheral wall that tapers forward, a top wall, and a bottom wall, defining a rear opening for receiving toes of a user, being the top wall and strategic portions of the arcuate peripheral reinforced with ribs defined in a manner that maximizes strain hardening properties of the material during metal forming thus achieving higher strength in localized critical areas of the toe cap.

[0036] In an embodiment, the metal toecap has ribs in variable number (preferably 2 to 4) that are defined in a manner that reinforces both the top wall transversally and the arcuate peripheral wall in the critical lateral to top transition.

[0037] In an embodiment, the ribs are geometrically defined in a manner that maximizes strain hardening properties of the material during metal forming thus achieving higher strength in localized critical areas of the toe cap. These critical areas for static and dynamic loading are the top wall and the connection between the top wall and the peripheral wall. The extension of the ribs from the top wall to the peripheral wall is important for the geometric and material reinforcement of areas where high bending moments occur. [0038] In an embodiment, a forward extension of the stiffening elements is designed in a manner that increases impact resistance in a critical area through geometrical and material properties enhancement. Geometric improvement is obtained through local increase of moment of inertia while material enhancement is obtained by strain hardening properties of the material used for metal forming.

[0039] In an embodiment, the metal toecap for safety shoes is made of Advanced High Strength Steel alloys. This type of steels has in general specifications for yield strength in excess of 850MPa and within the different commercial grades have designations like: dual-phase (DP); TRIP (Transformation Induced Plasticity); Martensitic. For example, DP1000 is a common reference.

[0040] In an embodiment, the metal toecap for safety shoes is made of Advanced High Strength Steel alloys that have yield strength in excess of 850MPa and thickness range defined between 0.9mm and 1.5mm.

[0041] In an embodiment, the metal toecap for safety shoes is made of Advanced High Strength Steel, alloys that do not require heat treatment for achieving component strength.

[0042] Advantages of the disclosure are thus obtained in particular through the combination of material properties (high strength and strain hardening); and geometry design (geometry improvement combined with local strain hardening),

Brief Description of the Drawings

[0043] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of the disclosure.

[0044] Figure 1 represents a schematic model of an embodiment of the present disclosure.

[0045] Figure 2 represents a computer modelling model of an embodiment of the metal toe cap. [0046] Figure 3 represents schematically a side view of a metal toe cap wherein (1) consists in top surface; (2) and (3) central ribs; (2a), (3a), and (3c) lateral and frontal extensions; (4) side wall and (5) tab region.

[0047] Figure 4 represents schematically a rear view of a metal toe cap wherein (2) and (3) are central ribs; (2a), (2b), (3a), (3b) and (3c) corresponds to lateral and frontal extensions; (4) side wall and (5) tab region.

[0048] Figure 5 represents schematically a top view of a metal toe cap wherein (1) consists in top surface; (2) and (3) central ribs; (2a), (2b), (3a), (3b) and (3c) lateral and frontal extensions; (4) side wall and (5) tab region.

[0049] Figure 6 represents schematically a sectional view of a metal toe cap wherein (1) consists in top surface; (2) and (3) central ribs; (2b), (3b), and (3c) lateral and frontal extensions; (4) side wall; (5) tab region and (6) profile.

[0050] Figure 7 represents schematically a perspective view, in section, of the metal toe cap in accordance with an embodiment of the present disclosure, with the highlighted thickness profile wherein (6) corresponds to the profile.

[0051] Figure 8 represents multiple views of an embodiment of the the metal toe cap - top (A), front (B), right side (C), bottom (D), perspective (E).

Detailed Description

[0052] The metal toe cap in accordance with the present disclosure illustrated in Figures 1 and 2 and further detailed in Figures 3 through 8 assumes a full set of technical features, which intends to outperform in an innovative combined manner, the key advantages of the role and current solutions. The substantial reduction of weight by increasing mechanical strength rates, withal reducing the thickness of the toe cap wall portions and controlling the optimization of the structural volume saving are major identifiable characteristics of the present disclosure.

[0053] The reuse of accumulated knowledge from other applicable areas of im pact loading phenomenon and the application of Advanced High Strength Steels - AHSS, with properties optimized to absorb impact energy, pointed out the guideline to the development of the model described in this disclosure. The material properties stimulated to a superior mechanical strength state-owned with ultimate tensile strength values of approximately 1200MPa, combining in the best manner to potentiate the phenomenon of strain hardening of the material and the strain rate sensitivity in a controlled, localized and specific engineering geometry. This point focused the goal of the development program, the study of a geometric model with a specific region coupled with an exclusive ribbed geometry, performing a located and differentiated increase of over than 25% compared to the base state of material strength. In this context, the full reinforcement potential is exploited by a cold forming process, particularly implemented to reproduce the toe cap model and to maximize all material properties as well, covering a proper application of AHSS grades, such as: Dual-Phase (DP), Transformation Induced Plasticity (TRIP) and Martensitic steel alloys. The particular ribbed model assumes even greater relevance for a thickness reduction end. The new upgrade for a lightweight body design included some complex phenomena^'s such as structural stiffness compensation in order to improve the structural deformation mode. A set of ranges for final thickness values from 1.0mm to 1.2mm is described.

[0054] Referring to Figures 3 through 6, the metal toe cap of the present disclosure is formed by a top surface (1) that differs from the conventional steel toe cap by a new mild lowering effect and mainly by forming the local stiffeners defined as structural ribs (2) and (3). The top surface connects with a convergent side wall portion (4) which closes on the tab region (5). Preferably, the structural ribs are composed by two transversal, parallel, and independent elements. Both present respectively small lateral extensions, (2a), (2b), (3a) and (3b), and the forward region is composed by a specific frontal extension.

[0055] The combined model was studied to increase the performance of impact deformation resistance with a controlled capacity of energy absorption in a critical area through geometrical and material properties enhancement. Particularly, and still regarding to Figures 3 to 6, the reinforced top surface (1) with strategic ribs (2) and (3) defined in a manner that maximizes strain hardening properties of the material during metal forming,, thus achieve higher strength in localized and critical areas of the toe cap as previously referred. Those hardener elements formed across with lateral transitions by (2a), (2b), (3a) and (3b) are important for the geometric and material reinforcement of areas where higher bending moments occur. It is relevant at this point to emphasize these distinguish contributions, and furthermore the sole disposal and the role played mutually by both transversal ribs, with their respective functions, thus defining the accuracy of the final mechanical resistance performance. Combined, the exclusive geometry was calculated to enable an optimized control and to reduce the opening effects of the toe cap body, specifically, the side wall (4) and contributing to restrain slipping effects in tab region (5), during the evolution of the toe cap test deformation. At the same time, the specific forward extension of the stiffening elements (3c) was designed in a manner that increases the overall impact performance, strategically reinforced and elevated in a critical area through geometrical and material properties enhancement. Geometric improvements are obtained through local increase of moment of inertia while material enhancement is obtained by strain hardening properties of the material used for metal forming, as mentioned before.

[0056] The local stiffening concept in accordance with the present disclosure is obtained in this model solution by a particular manufacturing process and thus not increases the thickness, or the inclusion of greater thickness portions, but rather the opposite. It^'s relevant to reassure again this perspective. The present disclosure promotes a mechanism of high structural strengthening that plays with the convergence of thickness reductions. Thus, a final stiffening shell of special steels is gained and formed with optimized material properties. Moreover, It should be emphasized that the main ribbed metal toe cap, is based on a particular metal forming process that do not requires subsequent and complementary heat treatments to achieve the reference component strength as commonly applied on conventional metallic solutions. In this disclosure, the performance is led through the combination of material properties relating to the phenomenon of cold elongation properties (high strength and strain hardening); and geometric design (geometry improvement combined with local strain hardening). The formation of the toe cap shape by a severe cold stamping in a set of specific compressive die tools induces a prompt mechanical strength state that is also expected and potentiated over a suitable AHSS application. This context brings considerable advantages, such as not only environmental benefits as direct cost-effectiveness of the production procedure model, and an ultimate and superior strengthening factor.

[0057] Preferably, the representative profile for the toe cap thickness distribution (6), referring to Figures 5 and 6, shall be uniform, and therefore in this case, all toe cap portions including (1), (2) with (2a) and (2b), (3) including (3a), (3b) and (3c), (4) and (5) have the same thickness value for a range of models between 1mm and 1.2mm. In this context, the weight saving of the metal toe cap in accordance with the present disclosure and the EN framework and compared with conventional steel toe caps is around 40%.

[0058] An embodiment comprises a safety metal toe cap component for safety footwear comprising an exclusive geometric upper surface, a convergent U shaped side wall surface, and a bottom wall for the tab region, defining a proper rear opening. The present toe cap enables a reduction in weight by 40% compared to conventional steel toe cap models and a volume reduction (space saving) of 30% concerning the most referenced polymeric models.

[0059] An embodiment comprises a toe cap wherein the top surface includes an exclusive local stiffening concept using, at least, two independent, parallel and crosswise ribs relating to the ultimate strength properties enhancement. The combined hardness surface also comprises lateral extensions of the ribs and a forward extension to improve impact resistance properties. The toe cap presents the highest rate of mechanical strength.

[0060] An embodiment comprises a toe cap which presents an uniform thickness distribution for models with a range of values between 1mm to 1.2mm.

[0061] An embodiment comprises a metal toe cap model with a similar base surface development of the toe cap model as previously reported, not including the local stiffening concept and the hardness ribs formation. [0062] An embodiment comprises a toe cap which presents an uniform thickness distribution for models with a range of values between 1.4mm to 1.5mm.

[0063] An embodiment comprises a toe cap which is exclusively made from grades of Advanced High Strength Steels - AHSS. Therefore, the applications in the present disclosure of Dual Phase (DP), Transformation Induced Plasticity (TRIP), and Martensitic special alloys with yield strength specifications in excess of 850MPa are part of the disclosure.

[0064] An embodiment comprises a metal toe cap manufactured by a specific and particular metal forming process that allows withholding of the typical set of subsequent heat treatments, commonly used in the application of conventional steel alloys for metallic toe caps. The higher mechanical strength and normative performance are thus guaranteed earlier by an innovative approach in this sector of technical features aforementioned.

[0065] It will be appreciated by those of ordinary skill in the art that unless otherwise indicated herein, the particular sequence of steps described is illustrative only and can be varied without departing from the disclosure. Thus, unless otherwise stated the steps described are so unordered meaning that, when possible, the steps can be performed in any convenient or desirable order.

[0066] The disclosure is of course not in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof.

[0067] The above described embodiments are obviously combinable.

[0068] The following claims further set out particular embodiments of the disclosure.

Date: August 4, 2014

Claims

1. Metal toe cap for safety footwear comprising:

two or more reinforcement ribs extending from the top wall to part of the arcuate peripheral wall,

wherein said ribs are a transversal reinforcement of the top-wall and are a reinforcement of transition of the arcuate peripheral wall to the top wall.

2. Metal toe cap according to the previous claim wherein the reinforcement ribs are parallel and transversal in respect of the front-rear direction of the toe cap.

3. Metal toe cap according to any of the previous claims wherein the number of reinforcement ribs is 2 to 4.

4. Metal toe cap according to any of the previous claims further comprising a front reinforcement rib extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

5. Metal toe cap according to any of the previous claims wherein the reinforcement rib closest to the front of the toe cap is "T"-shaped, having two lateral ends extending transversally in respect of the front-rear direction of the toe cap and having a front end extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

6. Metal toe cap according to any of the previous claims wherein the ribs taper to arcuate peripheral wall.

7. Metal toe cap according to any of the previous claims wherein the metal is Advanced High Strength Steel, AHSS, in particular having a yield strength in excess of 850MPa, further on particular having a yield strength in excess of lOOOMPa.

8. Metal toe cap according to the previous claim wherein the shape of the metal toe cap is obtainable by cold forming process.

9. Metal toe cap according to any of the claims 7-8 wherein the thickness of the metal toe cap is between 0.9mm and 1.5mm, in particular 1.0mm to 1.2mm.

10. Metal toe cap according to any of the claims 7-9 wherein the thickness of the metal toe cap is uniform throughout the metal toe cap.

11. Metal toe cap according to any of the previous claims wherein the bottom wall is a brim extending inwards from the bottom periphery of the arcuate peripheral wall.

12. Footwear article comprising the metal toe cap according to any of the previous claims.

13. Process for obtaining a metal toe cap for safety footwear comprising:

shaping two or more reinforcement ribs extending from the top wall to part of the arcuate peripheral wall, wherein said ribs are a transversal reinforcement of the top-wall and are a reinforcement of transition of the arcuate peripheral wall to the top wall.

14. Process according to the previous claim wherein the reinforcement ribs are parallel and transversal in respect of the front-rear direction of the toe cap.

15. Process according to any of the claims 13-14 wherein the number of reinforcement ribs is 2 to 4.

16. Process according to any of the claims 13-15 further comprises shaping a front reinforcement rib extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

17. Process according to any of the claims 13-16 further comprises shaping the reinforcement rib closest to the front of the toe cap in a "T"-shape, said "T"-shape having two lateral ends extending transversally in respect of the front-rear direction of the toe cap and having a front end extending from the top wall to part of the arcuate peripheral wall in the front of the toe cap.

18. Process according to any of the claims 13-17 wherein the ribs taper to arcuate peripheral wall.

19. Process according to any of the claims 13-18 wherein the metal is Advanced High Strength Steel, AHSS, in particular having a yield strength in excess of 850MPa, further on particular having a yield strength in excess of lOOOMPa.

20. Process according to any of the claims 13-19 wherein the shaping of the metal toe cap is by cold forming process.

21. Process according to any of the claims 19-20 wherein the thickness of the metal toe cap is between 0.9mm and 1.5mm, in particular 1.0mm to 1.2mm.

22. Process according to any of the claims 19-21 wherein the thickness of the metal toe cap is uniform throughout the metal toe cap.

23. Process according to any of the claims 13-22 wherein the bottom wall is a brim extending inwards from the bottom periphery of the arcuate peripheral wall.

Date: August 4, 2014