TOE CAP AND METHOD FOR PRODUCING A TOE CAP

Abstract

The invention relates to a method for producing a toe cap (10) and such a toe cap itself. The toe cap comprises at least one end wall (12) extending in an arch shape and a cover wall (14) extending therefrom that covers the toes on the upper side, wherein the cover wall and the end wall have a base wall thickness G and areas separated from sections of the walls, such as webs in the walls, have a thickness D with 0?D<W, wherein the difference between the volume of the toe cap with areas filled to the base wall thickness W and the volume of the toe cap with the areas of lesser thickness is 5% to 35%, and/or the difference between the area of the toe cap with filled areas and the outer surface of the toe cap without the areas is 20% to 60%.

Claims

1. A method for producing a toe cap, comprising the steps of: 1) specifying a master cap (10) that has at least one defined parameter that is characteristic of a toe cap to be produced, 2) simulating a virtual cap (16) corresponding to the master cap according to a simulation method, 3) simulating the virtual cap in such a way that the value of a first simulated characteristic parameter corresponding to the defined characteristic parameter corresponds to that of the defined characteristic parameter of the master cap or lies within a predetermined tolerance range thereof, 4) modifying the structure of the virtual cap, 5) calculating the value of the simulated characteristic parameter of the structurally modified virtual cap (28) and comparing it with the value of the characteristic parameter according to step 1) and/or step 3), 6) modifying the structure of the virtual cap again, if a) according to step 5), a deviation is determined that lies outside a predetermined tolerance range, and then recalculating the characteristic parameter, or b) if the characteristic parameter lies within the tolerance range, if the structure modified according to step 4) does not meet a specified criterion, 7) if necessary, repeating process steps 4) to 6) until the calculated value of the characteristic parameters lies within the specified tolerance range, 8) producing the toe cap based on the virtual cap (28, 40, 42) having the modified structure, for which the simulated characteristic parameter lies within the predetermined value range of the first simulated characteristic parameter.

2. The method as claimed in claim 1, wherein, in step 2), the finite element method is used and in that preferably a closed body, the wall thickness W of which is uniform over the body, is used as the master cap specified according to step 1).

3. The method as claimed in claim 2, wherein the virtual cap (16) is divided into finite elements such that the value of a first simulated characteristic parameter corresponding to the defined characteristic parameter corresponds to that of the defined characteristic parameter of the master cap or lies within a predetermined tolerance range thereof.

4. The method as claimed in claim 1, wherein, as the at least one specified criterion in step 6) b) arrangement and/or geometry of one or more recesses in an area of the virtual cap (16) is selected which extends above the toes to be covered, wherein preferably upon the modification of the structure according step 6) b), a specification takes place by a user before the simulation to be carried out.

5. The method as claimed in claim 1, wherein the modification of the structure is carried out by changing the mass and/or surface of the virtual cap (16), wherein in particular the modification of the structure according to step 6) is done by at least one measure from the group of formation of through openings, modification of through openings, material removal, material thickening, formation or modification of webs or areas in the virtual cap delimiting through openings or depressions.

6. The method as claimed in claim 1, wherein, in method step 4), areas of the virtual cap (16) are removed and/or material removals take place, wherein in the areas, a force flow does not occur or does not occur significantly or is less in comparison to other areas.

7. The method as claimed in claim 1, wherein, to calculate the simulated characteristic parameter, a simulation of a pressure test and/or a drop test is carried out.

8. The method as claimed in claim 1, wherein the maximum permissible deformation of the cap perpendicular (Z direction) to the contact surface (X-Y plane) of the cap is selected as the characteristic parameter, wherein in particular additionally or alternatively to the maximum permissible deformation, at least one further parameter, in particular a material parameter from the group of tensile strength, yield point, uniform elongation, mechanical stress, and comparison stress is selected.

9. The method as claimed in claim 1, wherein comparison stresses of individual areas are computed of the virtual cap computed according to step 3) and in that modifications of the structure, in particular at least according to step 6) take place depending on the computed values of the comparison stresses.

10. The method as claimed in claim 1, wherein recesses and/or depressions are simulated in areas having a comparison stress of up to 90% of the maximum comparison stress occurring in the simulated cap and/or modifications in the structure do not take place in areas having a comparison stress of more than 90% of the maximum comparison stress occurring in the simulated cap (16), and/or recesses and/or depressions are simulated in areas having a comparison stress between 0 and 1200 MPa and/or modifications in the structure, which corresponds to a size 8 real cap made of metal according to DIN EN ISO 22568-1:2020-01 do not take place in areas of a comparison stress 1200 MPa.

11. The method as claimed in claim 1, wherein the toe cap is produced by injection molding, in particular metal injection molding, in the die casting method, lamination method, or an additive method or a body corresponding to the design of the toe cap is formed by forming, such as deep drawing, wherein recesses can be produced and/or reworked by laser beams, waterjet cutting, or milling, wherein in particular the toe cap is produced from metal, in particular tool steel, or plastic, in particular fiber-reinforced plastic.

12. A toe cap (40, 42), comprising: at least one end wall extending in an arch shape and a cover wall (64) extending therefrom that covers the toes on the upper side, wherein the cover wall and the end wall have a base wall thickness W and areas separated from sections of the walls, such as webs in the walls, have a thickness D with 0?D<W, wherein the difference between the volume of the toe cap (40, 42) with areas filled to the base wall thickness W and the volume of the toe cap with the areas of lesser thickness is 5% to 35%, and/or the difference between the area of the toe cap with filled areas and the outer surface of the toe cap without the areas is 20% to 60%.

13. The toe cap as claimed in claim 12, wherein the difference with respect to the volumes is between 10% and 30%, preferably between 20% and 30% and/or the difference of the areas is between 30% and 60%, in particular between 40% and 60%.

14. The toe cap as claimed in claim 12, wherein the areas have or are through openings (44, 46, 50, 52, 54, 58, 60, 62), wherein in particular the through openings (44, 46, 50, 52, 54, 58, 60, 62) have edge boundaries (48) that are inclined towards at least one surface, in particular towards the outside of the toe cap, and/or groups of areas of lower density, in particular groups of through openings (44, 46, 50, 52, 54, 58, 60, 62) are surrounded by a common edge (56) that is chamfered.

15. The toe cap as claimed in claim 12, wherein recesses (44, 46, 50, 52, 54, 58, 60, 62) and/or depressions (66, 68, 70) are provided in areas of the toe cap (40, 42) having a comparison stress of up to 90% and/or closed areas are provided in areas of the toe cap having a comparison stress of more than 90% and/or in that the toe cap (40, 42) has areas of lesser thickness in regions of a comparison stress between 0 and 1200 MPa and/or has the basic wall thickness in regions of a comparison stress greater than 1200 MPa with respect to a size 8 toe cap according to DIN EN ISO 22568-1:2020-01.

16. The toe cap as claimed in claim 12, wherein the toe that (40, 42) consists of metal, in particular tool steel, or plastic, in particular fiber-reinforced plastic or aramids, and/or in that the toe cap is an injection molded body, in particular a metal injection molded body, a diecast body, a body produced in the lamination method or in the additive method or by deep drawing and formation of recesses by laser beams, waterjet cutting, or milling.

Description

[0063] In the figures:

[0064] FIG. 1 shows a schematic representation of a closed master cap,

[0065] FIG. 2 shows a toe cap simulated using the finite element method corresponding to the master cap,

[0066] FIG. 3 shows the simulated toe cap according to FIG. 2 after a first structural modification,

[0067] FIG. 4 shows the simulated toe cap after a second structural modification,

[0068] FIG. 5 shows a schematic representation of the drop test standard test,

[0069] FIG. 6 shows a schematic representation of the pressure test standard test,

[0070] FIG. 7 shows a simulation result of comparison stress during a drop test on the simulated toe cap according to FIG. 2,

[0071] FIG. 8 shows a result of a simulated pressure test on the simulated toe cap according to FIG. 2,

[0072] FIG. 9 shows another view of the result of the pressure test in relation to the deformation of the simulated toe cap in the Z direction,

[0073] FIG. 10 shows a first example of a structurally optimized toe cap, and

[0074] FIG. 11 shows a second example of a structurally optimized toe cap.

[0075] The teaching according to the invention for producing a toe cap is to be explained based on the figures, wherein in the exemplary embodiment a toe cap is simulated using the finite element method, which is optimized in terms of mass and/or ventilation, to then, based on the CAD-Data from the simulated cap, produce a real toe cap that is used as an inner toe cap, wherein different minimum remaining heights in accordance with DIN EN ISO 22568-1:2020-01 have to be achieved depending on whether the toe cap is used for protective shoes or for safety shoes.

[0076] When simulating corresponding caps, a master toe capalso called a master capaccording to FIG. 1 is assumed, which is a closed body, i.e., the surface is completely closed and the wall thickness W is of constant thickness, i.e., the toe cap 10 has the same wall thickness both in the curved end wall 12 and in the cover wall 14 covering the toes on the upper side. Of course, the master cap can also be a body that already has openings and/or does not have a constant wall thickness.

[0077] An inner edge can extend from the bottom area of the peripheral wall 12, an edge that is angled inwards and lies in one plane.

[0078] The master toe cap is in particular a computer-aided design (CAD) of a real cap, wherein the material characteristics of the real cap are taken into consideration.

[0079] From the master cap 10, a toe cap 16 is simulated using the finite element method, which is divided into a finite number of sub-areas, i.e., finite elements. A subdivision takes place to the extent that the simulated cap 16 has the same value in relation to a characteristic parameter of the master cap 10. The characteristic parameter of the master cap 10 corresponds to the characteristic parameter of a real cap. In particular, the deformation of the cap in the Z direction, i.e., perpendicular to a plane which is spanned by the lower edge of the end wall 12 or the inwardly directed edge, is used as a characteristic parameter. The plane thus extends parallel to a surface on which the edge of the cap rests.

[0080] According to DIN EN ISO 22568-1:2020-01, the deformation in the Z direction cannot be less than 21 mm for a size 8, for example, for a type A metallic inner toe cap intended for protective shoes. For a metallic toe cap for safety shoes, the value is 25 mm. Corresponding toe caps are inserted underneath the upper part of a shoe.

[0081] In order to simulate the toe cap 16, the material parameters of the master cap, i.e., therefore a real cap, were taken into consideration. For example, when using tool steel 1.2709, the tensile strength was specified as 1280 MPa and the yield strength as 1080 MPa.

[0082] The simulated cap 16, which met the value of the characteristic parameter, was then structurally modified, alternatively volume modifications or surface modifications or both volume modification and surface modification being specified as parameters to be modified.

[0083] Area modification means that recesses were introduced into the simulated cap 16, wherein the total area of the recesses is set in relation to the total area of the closed simulated cap 16. For the volume parameter, the volume of the simulated cap 16 was set in relation to the volume of the structurally modified simulated toe cap.

[0084] In order to determine after a structural modification has been made whether it meets the requirements of the master cap, at least in terms of the deflection in the Z direction, in particular also with regard to stress distribution and plastic elongation, corresponding calculations were carried out on the simulated cap and compared with real values.

[0085] A corresponding structurally modified simulated toe cap after a first structural modification can be seen in FIG. 3 and is identified by the reference numeral 18.

[0086] In order to determine the desired parameters, tests were simulated. FIG. 5 shows the model with which a drop test was carried out to determine stress distribution, plastic elongation, and maximum deformation. The impact of a falling body having a mass of 20 kg from a height of 1 m onto the cap 18 was simulated.

[0087] The model had a base plate 22, a holding fork 24, a rounded plate 26, and the falling body 20. The simulated toe cap 16 was positioned on the base plate 22 between the holding fork 24 and the rounded plate 26. Fall body 20, base plate 22, holding fork 24, and rounded plate 26 were rigid bodies made of steel. The test specimen, i.e., the simulated toe cap 18, consisted of tool steel 1.2709.

[0088] The drop test was carried out taking these parameters into consideration. FIG. 7 shows the result on a structurally modified toe cap 28, wherein the tensile strength of 1280 MPa and the yield strength of 1080 MPa were taken into consideration as a reference for the calculated comparison stress. The ranges of different comparison stresses can be seen, wherein the maximum stress was above the failure limit.

[0089] Simulated pressure tests were also carried out on simulated toe caps in accordance with DIN EN ISO 22568-1:2020-01. The simulated setup of the pressure test can be seen in FIG. 6. This shows, purely in principle, the simulated toe cap 16 to be tested, which was positioned between an upper plate 30 and a lower plate 32. The lower plate 32 was made of steel and had a diameter of 150 mm and the upper plate 30 had a diameter of 141 mm. The material was also steel. The material for the simulated toe cap 16 was tool steel 1.2709. During the pressure test, a force of up to a maximum of kN or 20 kN was applied in 1 kN increments.

[0090] An example of a pressure test result for the simulated cap 28 at a force of 15 kN can be seen in FIG. 8, in which the comparison stress in the simulated toe cap 26 is shown.

[0091] FIG. 9 also shows the deformation in the Z direction on a further structurally modified toe cap 34, wherein the characteristics of the tool steel 1.2709 have been taken into consideration with regard to tensile strength and yield point.

[0092] With a force of 15 kN, which acted in addition to the gravitational load, a maximum deformation resulted such that the minimum remaining height in the Z direction, i.e., in the perpendicular to the support surface on the lower plate 32, on which the inwardly directed edge rested of the simulated toe cap 28 on which the simulated test is based met the standard.

[0093] If the finite element method reveals an impermissible deviation from the specified value with regard to the characteristic parameter to be checked, taking into consideration specifications, in particular the specification according to DIN EN ISO 22568-1:2020-01, a further structural modification was made, for example, openings have been enlarged or reduced and/or offset or the thickness of the wall has been modified in areas.

[0094] This will be described by way of example in reference to FIGS. 3 and 4. The simulated cap 18 did not meet the requirement regarding the specified characteristic parameter or parameter, so that a modification in the structure, i.e., a structural optimization, was carried out. The structural modification resulted in the simulated cap 36. A change can be seen in the arrangement of the openings and in particular the closed surface in the middle area of the cover wall 14. Modifications in this regard were made taking into consideration the comparison stresses resulting from the simulation. The simulation showed that for a size 8 metallic toe cap according to DIN EN ISO 22568-1:2020-01, recesses are possible in the areas in which the comparison stress was less than 1200 MPa, whereas in areas above this value recesses are to be avoided.

[0095] During the first structural modification, i.e. in the cap 16, openings were formed in the areas in which no or essentially no force flow was determined in the drop test and in the pressure test on the simulated toe cap 16.

[0096] Structural modifications are made to an extent until a simulated toe cap results that meets the requirements with regard to the characteristic parameter or characteristic parameters that are specified and have to be met by a real cap.

[0097] On the basis of the corresponding simulated toe cap, toe caps are then produced, in particular using the die-casting method, metal injection molding method, lamination method for caps made of fiber composite material, or in additive methods.

[0098] Forming material, such as deep drawing metal, can also be considered as a manufacturing method.

[0099] It is furthermore possible to process or rework the cap by means of laser, water jet cutting, or milling. Recesses can be produced or reworked. The same applies to material thinning.

[0100] The material for caps is metal, preferably steel, in particular tool steel, although fiber-reinforced plastics, for example, can also be used.

[0101] Based on the teaching according to the invention it follows that the volume of a toe cap produced according to the invention can be reduced between 5% and 35% in comparison to one having a closed surface, in particular in the range between 20 and 30%.

[0102] Alternatively or additionally, the surface of the cap can be reduced between 20% to 60%, in particular between 40% and 60%, i.e., a cap having a completely closed surface in comparison to one according to the invention which has recesses, such as openings, or areas of low wall thickness.

[0103] In particular, toe caps are also producible, which allow good ventilation due to the openings, i.e., heat build-up is avoided. Examples of corresponding toe caps 40, 42 are shown in FIGS. 10 and 11. These also illustrate that the type of openings can basically be chosen arbitrarily. The openings in the toe cap 40 are formed by triangles, wherein triangles are combined into groups that are surrounded by a common edge that is inclined towards the surface. Chamfers are therefore present. This is illustrated, for example, by the triangular openings 44, 46 and the common edge 48 surrounding them or by the openings 50, 52, 54 and the common surrounding chamfered edge 56.

[0104] In FIG. 11, the openings are formed by circular openings, some of which are identified by way of example with the reference numerals 58, 60, 62.

[0105] If volume changes, i.e., changes in mass, are primarily achieved due to through openings, reductions can also be achieved by forming depressions in the toe cap alternatively or additionally to through openings, i.e., material removal takes place, as is also illustrated in FIG. 10. In the middle area of the toe cap 40, namely in the cover wall 64, recesses 66, 68, 70 are provided, which result in a reduction in volume and thus mass.