JP2006070090A - Toe cap for safety shoes and safety shoes using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cheap, resin-made toe cap for safety shoes that satisfies the specifications of JIS T8101 Class S. <P>SOLUTION: In the toe cap for safety shoes consisting of a fiber-reinforced thermoplastic resin, the toe cap adopts a structure mentioned in the following: when the zenithal line of the outer surface extending from the tip to the end of the toe cap is divided into five equal parts and each dividing line is named in order from the tip side a dividing line A, ditto B, ditto C, ditto D and ditto E, and when the thickness of the toe cap is measured at the three points of both ends and the center of each dividing line and the value, obtained by totalizing the maximum thickness and the minimum thickness in each measured dividing line and dividing the sum by 2, is regarded as an average thickness, the average thickness of the dividing line C region is ≥6.5 mm, the average thicknesses of the dividing line B region and/or the dividing line D region are ≥6.5 mm, and the toe cap thickness in the region other than the dividing line A-E regions is almost equal to the maximum thickness of the dividing line C region or smaller than it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a safety shoe tip and a safety shoe using the same.

  The tip of the safety shoe protects the toes of the toe from impacts and pressures caused by falling heavy objects, and JIS T8101 defines the impact resistance and pressure resistance for each work application. Conventionally, steel materials having excellent strength have been used as the material for the tip of safety shoes. However, since the steel tip has the disadvantages that it is heavy, has poor heat retention, and cannot be incinerated and discarded, in recent years, fiber reinforced resin materials have come to be used as the tip material.

  As the fiber reinforced resin, a resin containing glass fiber is generally used. However, in order to increase the strength of the tip, glass fiber having a long fiber length is preferably added, and the thickness of the tip is increased. It should be thick.

  By the way, as a method for molding a tip using a fiber reinforced resin, there are a compression molding method, a method of injection molding after extruding pellets, and the like. Among these, the injection molding method is excellent in terms of productivity.

  However, once the fiber reinforced resin pellets are produced by the extrusion method, the injection molding method using the pellets requires two steps of pellet extrusion and injection molding, resulting in poor production efficiency. Further, in this method, since the shearing force is applied to the fiber in the two steps of pellet extrusion and injection molding, the fiber length tends to be shortened. For this reason, it is difficult to obtain sufficient tip-core strength by this method.

  On the other hand, the compression molding method in which a fiber resin sheet in which a glass fiber is impregnated with a resin is prepared, and this sheet is placed in a molding die and heated and pressed is not applied with shearing force on the glass fiber. Since this is not cut, it is easy to produce a high-strength tip by this method.

  However, according to this method, since the composition of the fiber resin sheet to be pressurized does not move or flow in the molding die at the time of heat and pressure molding, the fiber resin sheet needs to be placed excessively in the molding die. However, since the fiber resin sheet composition does not move or flow, uneven pressure is likely to occur. For this reason, the strength of the molded product tends to be non-uniform, and it is necessary to cut the surplus resin sheet portion after pressure molding to adjust the shape of the molded product. Moreover, since it is necessary to arrange | position a fiber resin sheet in a shaping die for every press molding, production efficiency is bad. Furthermore, there is a problem that the production of the fiber resin sheet is expensive.

  Here, the following patent documents 1-3 are mentioned as a technique concerning the tip for safety shoes using the reinforced resin material.

JP 2002-85109 A (Abstract)

JP 2003-52409 A (paragraphs 0006, 0007, 0022)

JP 2003-102509 A (paragraphs 0010 to 0013)

  The technique according to Patent Document 1 will be described with reference to FIG. In this technique, a long fiber reinforced thermoplastic resin is used as a material, the thickness of the rising portion a at the tip of the tip is 3.5 mm or more, and the average curvature r of the shoulder b is 20 or less. According to this technology, sufficient strength can be obtained by setting the thickness of the tip portion where the most of the compression and impact load is concentrated (the rising portion a of the tip of the lead core) to be 3.5 mm or more. By setting the average curvature r to 20 or less, most of the compression and impact load is absorbed by the side portion of the tip, particularly the shoulder b and the rising portion a at the tip of the tip, so that the deformation of the rear portion of the ceiling The amount is extremely reduced and can be suppressed within the allowable stress.

  However, as shown in FIG. 4, in this technique, the thickness of the ceiling portion c from the shoulder portion b that absorbs the impact most is small, and there is a risk that the tip is damaged by the compression / impact. Moreover, since it is necessary to produce long glass fiber thermoplastic resin pellets in advance and then produce them by injection molding or compression molding, the production efficiency is poor.

  The technology according to Patent Document 2 is a technology in which a long fiber reinforced thermoplastic resin is used as a material, the reinforcing fiber content of the skirt portion with respect to the main body is 70 to 100%, and the thickness of the tip is 2 to 6 mm. . According to this technique, it is said that a lightweight, homogeneous and high-strength safety shoe toe core can be obtained without causing variations in strength of the molded product and appearance defects.

  However, this technique includes a step of preparing a long fiber reinforced thermoplastic resin fiber pellet material in advance, a step of primarily forming a pseudo tip by placing the pellet material in a pseudo mold and compressing the pellet under heating. Further, the obtained pseudo toe core is placed in a safety shoe toe core molding die, and a process for compressing and molding the safety shoe toe core by heating and pressurizing is required. Since each process is independent, production efficiency is poor. .

  The said patent document 3 is a technique containing the glass fiber whose mass mean fiber length is 0.6 mm or more and whose maximum fiber length is 50 mm, and thermoplastic resins other than thermoplastic polyurethane. According to this technique, breakage / breakage of the glass fiber due to injection molding can be reduced, so that a long glass fiber having a mass average fiber length of 0.6 mm or more can be left in the injection-molded product, whereby S of JIS T8101 It is said that a safety shoe toe that satisfies the grade (for ordinary work) standards can be obtained.

  However, this technique requires a step of impregnating a glass fiber with a thermoplastic resin in advance, a step of mixing and injecting resin and glass fiber to form a pellet, a step of placing the pellet in an injection molding machine and injection molding. Since each process is independent, production efficiency is poor.

  The inventor has intensively studied a tip for resin safety shoes. As a result, the resin and the glass fiber not impregnated with the resin are put into an injection molding machine and directly injected into the core metal mold (direct injection molding method) without sacrificing lightness. It was found that a safety shoe toe core having a strength satisfying the JIS T8101 (S class) standard was obtained.

  It is an object of the present invention to provide a resin toe-leading structure for safety shoes that has sufficient impact resistance and pressure resistance satisfying JIS T8101 (S class) standards and is excellent in productivity. . Another object of the present invention is to provide a safety shoe that is excellent in safety and lightweight by using this tip.

  The present invention according to the toe for safety shoes for solving the above-mentioned problem is a toe for safety shoes made of fiber reinforced thermoplastic resin, and the outer surface zenith line from the tip to the end of the tip is divided into five equal parts. Each divided line segment is divided into a divided line segment A, a divided line segment B, a divided line segment C, a divided line segment D, and a divided line segment E in order from the front end side. When measuring the thickness of the tip in the above, the maximum thickness and the minimum thickness in each of the measured dividing line segment is summed and divided by 2 as the average thickness in the dividing segment region, The dividing wall segment C region has an average thickness of 6.5 mm or more, and the dividing line segment B region and / or the dividing line segment D region has an average thickness of 6.5 mm or more, and the dividing line segment A The tip-core thickness in the region other than the E region is substantially the same as the maximum thickness of the dividing line segment C region. And wherein the or at less.

  The effect of the above configuration will be described with reference to FIG. 1A and 1B are views showing a toe according to the present invention, FIG. 1A is a perspective view seen from the ankle side (terminal side), and FIG. 1B is a view seen from the toe side (tip side) of the foot. FIG. 1C is a longitudinal sectional view taken along a plane including the outer surface zenith line 11 of FIG. In addition, each area | region (AE) of a cross section is called dividing line segment AE area | region.

  As shown in FIG. 1 (a), the toe core 1 is connected to the top surface 1a that protects the toes, the shoulder portion 1b that is greatly curved, is connected to the top surface portion, is connected to the shoulder portion, and rises substantially vertically. It comprises a rising portion 1c and a collar portion 1d that is connected to the rising portion and grounds the tip.

  In such a structure, when a strong impact is applied from the outside, it is most parallel to the outer peripheral line O of the top surface portion 1b, 10mm from the midpoint H of the zenith line 11, and the zenith A line P having a length of 20 mm centered on the line and a line segment P parallel to the outer peripheral line O of the top surface portion 1b, 10 mm from the midpoint H of the zenith line 11, and a length of 20 mm centered on the zenith line A segment Q and a region X (see FIG. 1B) surrounded by two line segments connecting both ends of the line segment P and the line segment Q, and in particular, the intensity of the region along the zenith line 11 is Especially required. This region X absorbs the impact most when an impact is applied to the tip, and prevents the impacted portion (which may be outside the region X) from being destroyed. Therefore, it is preferable to increase the strength by increasing the thickness of the region X, and it is particularly preferable to increase the strength near the zenith line in this region.

  FIG. 1C shows a longitudinal sectional view taken along the outer surface zenith line 11. In FIG. 1C, the entire length of the outer surface zenith line is divided into five equal parts, and these dividing line segments are set as dividing line segments A to E in the order from the toe side to the ankle side. A cross section in the thickness direction of the tip including A to E is referred to as a dividing line segment A to E region. The region X is a region including the dividing line segment C region. Hereinafter, the present invention will be described with reference to FIG.

  In the present invention, the average thickness of the dividing line segment C region is set to 6.5 mm or more. When the thickness of the tip of the fiber reinforced thermoplastic resin is set to this thickness, the strength sufficiently satisfies the JIS T8101 class S (for ordinary work) standard.

  However, if both the dividing line segment B area that supports the dividing line segment C area from the toe side (tip side) and the dividing line segment D area that supports the dividing line segment C area from the ankle side (end side) are low, the dividing line segment C area Even if the strength of only the area is increased, the impact resistance as a whole of the tip does not increase. This is because the dividing line segment B region and the dividing line segment D region also act to absorb a part of the impact applied to the tip. Therefore, in order to increase the impact resistance of the lead core, it is necessary to increase not only the central parting line segment C region but also the strength of the subsequent region. For this reason, in the present invention, the average thickness of the dividing line segment B region and / or the dividing line segment D region is also set to 6.5 mm or more.

  On the other hand, in the present invention, the thickness of the region other than the dividing line segments A to E is approximately equal to or less than the maximum thickness of the dividing line segment C region. it can. The term “substantially equivalent” is used because a manufacturing error is taken into account, and this error is usually within + 10% of the maximum thickness of the dividing line segment C region.

  Here, the outer surface zenith line will be described with reference to FIG. FIG. 2A is a bottom view of the tip, and FIG. 2B is a perspective view of the tip from the toe side. As shown in FIG. 2 (a), a straight line X connecting both ends of the front core ankle is drawn, and a straight line Y parallel to the straight line X and in contact with the fingertip side outer surface of the front core is drawn. The contact P at this time is the tip of the tip. Next, a straight line Z perpendicular to the straight line X and passing through the contact point P is determined. And the line | wire which is perpendicular | vertical to a front-end | tip installation surface (shoe bottom surface) and contains the said straight line Z and the outer surface (except for the heel part) of a front-end | tip center are defined. This intersection line is defined as the outer surface zenith line 11 (see FIG. 2B).

  The safety shoe toe according to the present invention described above has an average wall thickness of 4.0 mm or more as defined in Formula 1 and a minimum wall thickness of the tip is 2.5 mm or more, The maximum thickness of the tip can be 15 mm or less. In addition, the minimum thickness and the maximum thickness mentioned here mean the minimum thickness and the maximum thickness in actual thickness measurement.

(Formula 1)
Total thickness of tip core (mm) = weight of tip core excluding wrinkles (g) / [tip outer surface area (mm ² ) x tip core density (g / mm ³ )]

  An average wall thickness of less than 4.0 mm or a minimum wall thickness of less than 2.5 mm is preferable because a thin area may be destroyed even if the shock absorption capacity in the dividing line segment C area is excellent. Absent. In addition, if the maximum thickness is 15 mm or more, sufficient strength can be obtained, but the weight increases as the thickness increases, and the lightness is impaired. . Further, since more resin is required, the cost is increased accordingly. Therefore, it is preferable to be within the above range.

  Further, in the present invention, the fiber in the fiber reinforced thermoplastic resin is a glass fiber, and the safety shoe tip is directly injection molded by an injection molding machine equipped with a kneading mechanism for glass fiber and resin. It can be set as the structure which is made.

  As the reinforcing fiber contained in the thermoplastic resin, a glass fiber is preferable from the viewpoint of strength and cost, and a lead core using a direct injection molding method is preferable in that a shearing force is applied only once to the fiber. When the direct injection molding method is used, the glass fiber is less bent, so that a high-strength resin tip having long glass fibers is realized, and the direct injection molding method is excellent in productivity. Therefore, according to the above configuration, it is possible to provide a tip having excellent lightness and impact resistance at low cost.

  The present invention relating to a safety shoe for achieving the above object is a safety shoe in which the tip for safety shoe according to the present invention is incorporated in a shoe tip.

  According to the present invention, it is possible to provide a safety shoe toe and safety shoes that are lightweight, excellent in safety, and low in cost.

  The best mode for carrying out the present invention will be described in detail below using embodiments.

(Examples 1 and 2, Comparative Examples 1 and 2)
45 parts by mass of nylon (2020 made by Ube Industries) and 55 parts by mass of glass fiber (fiber diameter 13 μm, fiber length 3 mm) were prepared, using an injection molding machine equipped with a kneading mechanism having the structure shown in FIG. A tip having a wall thickness distribution shown in Table 1 below was prepared. The thickness distribution in each area of the dividing line segments A to E is measured by measuring the thickness at both ends and the center of each dividing line area, and the average thickness is obtained by dividing the sum of the maximum and minimum values by 2. Thickness.

  The total average wall thickness was calculated by the following formula. The surface area was calculated by pasting paper on the entire outer surface of the lead core without gaps, measuring the weight of the paper, and dividing the weight by the product of the specific gravity and thickness of the paper.

Total thickness of tip core (mm) = weight of tip core excluding wrinkles (g) / [tip outer surface area (mm ² ) x tip core density (g / mm ³ )]

  The injection molding machine used above is an injection molding machine for producing an injection-molded product by melt-kneading a reinforcing material such as a thermoplastic resin and glass fiber, a filler, etc. with a heating cylinder 20 and a rotating screw 30. By changing the shaft diameter of the screw 30 stepwise, the material supply zone 301 with a small shaft diameter, the compression zone 302 with a gradually increasing shaft diameter, and the passage of the material with a larger shaft diameter than other zones. This is a device characterized in that it is configured with a measurement zone 303 that suppresses the above. When this apparatus is used, the fiber and the resin are sufficiently kneaded.

  Note that reference numeral 12 in FIG. 3 denotes a hopper for charging the raw material, 32 is a flight, 35 is a backflow prevention valve, and 40 is a tip nozzle. Further, reference numeral 31 denotes a blister ring whose outer periphery is flat and has a diameter larger than the axis of a portion where there is a nearby flight. Since the blister ring 31 is provided, a mixture of molten resin and glass fiber is rapidly compressed when passing through a narrow gap formed between the blister ring and the inner periphery of the heating cylinder. The effect of further promoting the mixing and dispersion of is obtained.

[Physical property test]
45 parts by mass of nylon (2020, manufactured by Ube Industries) and 55 parts by mass of glass fiber (fiber diameter 13 μm, fiber length 3 mm) are prepared, and tensile test (ASTM D368) using an injection molding machine as shown in FIG. Test pieces for bending test (ASTM D790) and Izod impact value test (ASTM D256, with notch) were prepared.

  These test pieces were subjected to a test after absorbing moisture in an equilibrium state at 23 ° C. and 50% RH based on ISO 1110. The tensile strength was tested based on ASTM D368, the bending test was performed based on ASTM D790, and the Izod impact value was tested based on ASTM D256 (notched).

As a result, the tensile strength was 23 kgf / mm ² , the bending strength was 38 kgf / mm ² , and the Izod impact value was 23 kgf · cm / cm ² .

〔performance test〕
The tip resistance produced above was measured for impact resistance based on JIS T8101 standard. As a result, the lead cores according to Examples 1 and 2 satisfied the S class (for ordinary work). On the other hand, the lead cores according to Comparative Examples 1 and 2 were broken by the impact under the S class condition.

  This is considered to be due to the following reason. In Example 1, the average thickness of the dividing line segment C region (region X) that absorbs the most impact is set to a sufficient strength of 6.5 mm or more (8.0 mm). Moreover, the average thickness of the dividing line segment B area which supports the dividing line segment C area from the toe side is formed to be 6.5 mm or more (7.9 mm). Therefore, the dividing line segment C region absorbs most of the impact applied to the tip, and the dividing line segment B region absorbs part of the impact applied to the tip, so that when the impact is applied, the tip core Is not destroyed.

  Moreover, in Example 2, the average thickness of the dividing line segment C region that absorbs the most impact is set to a sufficient strength of 8.1 mm. Moreover, the average thickness of the dividing line segment D area | region which supports the dividing line segment C area | region from the ankle side is formed in 7.0 mm. The dividing line segment C region absorbs most of the impact applied to the tip, and the dividing line segment D region absorbs part of the impact applied to the tip, so that the tip breaks when an impact is applied. Not.

  On the other hand, in Comparative Example 1, the thicknesses of the divided areas A to E are all set to 6.0 mm. For this reason, since the strength of the dividing line segment C region is low and the shock absorption capacity is not sufficient, the total average wall thickness is 5.1 mm, which is thicker than 4.1 mm and 4.3 mm in Examples 1 and 2. Even then, the tip will break in the impact test.

  In Comparative Example 2, the average thickness of the dividing line segment C region that absorbs the most impact is set to a sufficient strength of 7.5 mm, but the dividing line segment B region that supports the dividing line segment C region, The average thickness of the dividing line segment D region is 6.1 mm and 5.8 mm, and the strength is insufficient (impact absorbing ability is insufficient). Therefore, although the dividing line segment C region can absorb most of the impact applied to the tip, both the dividing line segment B region and the dividing line segment D region can hardly absorb the impact applied to the tip, and this is also broken. To.

  In Comparative Example 1, the thickness of all the regions was 6.0 mm, but the average thickness was 5.1 mm. This is an error due to the total average wall thickness obtained from Equation 1 above.

(Other matters)
In the above embodiment, the two divided regions of the dividing line segment B region and the dividing line segment C region or the dividing line segment C region and the dividing line segment D region have an average thickness of 6.5 mm or more. Of course, all three divided regions of the segment B region, the segment line segment C region, and the segment line segment D region may have an average thickness of 6.5 mm or more. In addition, when only two divided areas of the divided line segment B area and the divided line segment C area or the divided line segment C area and the divided line segment D area are set to 6.5 mm or more, the average thickness of the remaining one divided area Is preferably 5.0 mm or more, and more preferably 5.5 mm or more.

  Examples of the resin used for the lead core according to the present invention include polyamide resins such as nylon 6 and nylon 66 which are excellent in strength and inexpensive, but the present invention is not limited to this. For example, general-purpose resins such as polyethylene, polypropylene, AS resin, and ABS resin, and engineering resins such as polycarbonate, PBT, PET, and PPS can be used. Moreover, the polymer alloy which mixed the resin material mentioned above may be sufficient.

  However, the strength of the fiber reinforced resin is greatly affected by the strength of the resin itself (tensile strength, bending strength, Izod impact value, etc.), the blending amount of the glass fiber, the length of the glass fiber, and the like. Therefore, in the case of using a resin with low strength, in the kneading in the direct injection molding method in which the blending amount of the glass fiber is increased, the kneading is performed so that the length of the glass fiber contained in the tip of the molded product becomes long. It is preferable to take measures such as setting conditions.

Here, as an index indicating the strength of the fiber reinforced resin, the tensile strength (kgf / mm ² ), the bending strength (kgf / mm ² ), and the Izod of the fiber reinforced resin based on the test methods in the above examples. The sum of the impact value (kgf · cm / cm ² , with notch) is preferably 65 or more, more preferably 75 or more, and further preferably 78 or more.

Moreover, as a compounding quantity of glass fiber, it is preferable that it is 35-70 mass%, and 40-
More preferably, it is 68 mass%, and it is still more preferable that it is 45-65 mass%. When the glass fiber content is less than 35% by mass, it is difficult to obtain sufficient strength. When the glass fiber content is more than 70% by mass, the amount of glass fiber is excessive, so that the fluidity of the fiber-reinforced thermoplastic resin is deteriorated and injection molding is performed. This is because it becomes difficult.

  Moreover, in the said Example, although the fiber diameter of 13 micrometers and the fiber length of 3 mm were used, it is needless to say that it is not limited to this thickness and length.

  Further, an additive such as an antioxidant, a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, a deodorant, a colorant, a pigment, and an antistatic agent may be contained in the tip of the molded product. . A coupling agent may be used to increase the affinity between the glass fiber and the resin during kneading.

  Moreover, in the said Example, although paper was used for the measurement of a surface area, it is not restricted to paper. Any tape that can easily measure the surface area may be used. For example, a tape that can be easily attached and removed may be used.

  Moreover, in the said Example, preparation of the tip was performed using the low-cost direct injection molding method, However, This invention is not limited to the direct injection molding method.

  As described above, according to the present invention, a lightweight safety shoe tip can be provided with high productivity that satisfies the S class of JIS T8101, and its industrial applicability is great.

1A and 1B are views showing a toe according to the present invention, in which FIG. 1A is a perspective view seen from the ankle side, FIG. 1B is a perspective view seen from the toe side, and FIG. These are the longitudinal cross-sectional views cut | disconnected by the plane containing the outer surface zenith line | wire 11 of FIG.1 (b). FIG. 2 is a drawing for use in explaining the outer surface zenith line, FIG. 2 (a) is a bottom view of the tip, and FIG. 2 (b) is a perspective view of the tip as viewed from the toe side. It is a cross-sectional schematic diagram for demonstrating the structure of the injection molding machine used by the Example and the comparative example. It is sectional drawing which shows the tip of the technique which concerns on patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lead core 1a Top surface part 1b Shoulder part 1c Stand-up part 1d ridge part 11 Outer surface zenith line

Claims (4)

In the tip for safety shoes made of fiber reinforced thermoplastic resin,
Each dividing line segment obtained by dividing the outer surface zenith line from the tip end to the terminal end into five equal parts is divided into a dividing line segment A, a dividing line segment B, a dividing segment segment C, a dividing segment segment D, and a dividing segment. As the line segment E, the thickness of the tip core is measured at each of the dividing line segments at the three points of both ends and the center, and the maximum thickness and the minimum thickness of each measured dividing line segment are summed up by 2. When the divided value is the average thickness in the dividing line segment area,
An average thickness of the dividing line segment C region is 6.5 mm or more,
And the average thickness of the said dividing line segment B area | region and / or the said dividing line segment D area | region is 6.5 mm or more,
The tip-core thickness in the region other than the dividing line segments A to E is approximately equal to or less than the maximum thickness of the dividing line segment C region,
A toe for safety shoes. In the tip for safety shoes according to claim 1,
The total average wall thickness defined by Formula 1 of the tip is 4.0 mm or more,
The minimum thickness of the tip is 2.5 mm or more,
The maximum thickness of the tip is 15 mm or less,
A toe for safety shoes.
(Formula 1)
Total thickness of tip core (mm) = weight of tip core excluding wrinkles (g) / [tip outer surface area (mm ² ) x tip core density (g / mm ³ )] In the tip for safety shoes according to claim 1,
The fiber in the fiber reinforced thermoplastic resin is a glass fiber,
The safety shoe tip is formed by direct injection molding using an injection molding machine equipped with a kneading mechanism for glass fiber and resin.
A toe for safety shoes. A safety shoe comprising the tip of the safety shoe according to claim 1, 2 or 3 incorporated in the shoe tip.

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