According to the December 05 issue of this site, the protective shoe covers are usually installed in finished shoes that provide shock and compression resistance. The traditional shoe heads are usually steel heads, and some are aluminum shoe heads. In recent years, plastic shoe heads or non-metallic shoe heads have gradually entered the market.
Compared to steel toppings, aluminum toppings and non-metallic synthetic toppings are lighter, but they are often much more expensive. However, they do have their advantages in specific applications, including use in magnetically sensitive electronics and petrochemical industries. Safety shoes with synthetic toe caps and plastic toe caps are also commonly used at airports because their non-metallic properties minimize metal interference when passing security screening areas.
At present, there are several different test standards and certification requirements for the specific protection performance level of safety shoes and shoes in the world. These include Canada's CSA certification under the z195-02 standard, the United States' ASTM F2413-05 standard (which has replaced the ANSI Z41-1999 standard in recent years), and the Personal Protective Equipment (PPE) Directive 89/686 applicable to the European Union. /EEC related regulations.
All of the above standards and regulations require that the shoe covers be part of the interior of the finished shoe for test evaluation.
Requirements for European Standards The requirements of the Personal Protective Equipment Directive CE include requirements for finished products such as finished shoes and clothing, and do not apply to accessories, materials and components. Therefore, it is not possible to apply for the CE standard.
However, the shoe toe cap can be tested as a part, using the requirements and test methods of the European standard EN 12568:1998 specifically set for the shoe toe cap. The test conditions of this standard are similar to those of the test standard EN ISO 20345 for finished shoes, but require higher clearance after impact compression in order to counteract the gap reduction that may result from a relatively soft shoe sole squeezing upwards.
The EN 12568 standard covers the impact resistance and compression resistance of the shoe toe cap, as well as the measurement criteria for the shoe toe cap and the corrosion resistance of the metal shoe toe cap.
Sealed in non-metallic shoe toe, its impact resistance through several different pre-treatment tests, such as high-temperature and low-temperature pre-impact test and after several different chemical treatment shock test.
In the case of manufacturers of finished shoes manufactured for the European market, we strongly recommend that they only purchase shoe covers that meet the EN 12568 test standard. If possible, suppliers of shoe covers are required to provide test reports issued by third-party testing agencies (eg SATRA) whose products are audited by the ISO 17025 standard. For non-metallic shoe covers, the European safety footwear standard (EN ISO 20345 and EN ISO 20346) requires that only shoe heads that meet the requirements of EN 12568, paragraph 4.3, are used in finished shoes.
Regardless of the standards to be achieved, the design of shoe covers is also very important for good performance. Based on the "protection space" principle, the design of the shoe toe must be such that it has sufficient strength to limit its rupture or deformation within a certain range, that is, when the impact or compression test is performed according to the relevant standards, the toe cap cannot be crushed or be Pressure deformation.
In addition to the material strength, thickness, and shape of the shoe head, the width of the hem formed along the bottom edge of the shoe head is also an important factor because the hem can help the shoe to transfer its pressure to the sole that supports it. Another important feature is the depth of the interior of the shoe's baotou. The deeper the shoe's baotou, the greater its amount of deformation upon impact, and the better the protection of the wearer.
Different standards of compression resistance test (such as ASTM, CSA, EN) are very similar, and the impact resistance test is different due to the impact of the shape of the head, the energy of the impact, and the minimum clearance after the impact of the standard requirements and other factors Something changed.
Obviously, the specifications and performance of the actually used shoe covers are the most important factors that any safety shoes can provide. However, the design and structure of the safety shoes themselves also adversely affect the performance of the shoe heads, which is why the heads of the shoes are removed from the finished shoes for testing, because only then can the actual protection of the wearer be detected. Level.
Factors Affecting Footwear Performance The performance of shoe covers may be affected by various other factors. According to the principle of protecting space in work, not only the shoe head must have sufficient strength, but also the shoe sole should be able to form the necessary supporting strength immediately under the hem of the shoe head under pressure or impact so that the impact force can be effectively transferred. Going to the ground, it will not cause other parts such as the shoe head on the sole to fall into the sole after being stressed.
For this reason, it can be said that if the formula of the shoe sole is relatively hard, its support to the shoe head is more effective. Another factor that needs to be taken into consideration is that the sole of the shoe should be kept in line with the edge of the shoe cover when designing, and the sole should have teeth. This is because the spacing area between the spurs of the sole does not provide a good support, so if possible, avoid the overlap between the rim of the shoe toe and the spacing between the scallops of the sole.
Another sole design feature that may affect the ability of the shoe to protect the head of the shoe is that the total thickness of the sole gradually decreases toward the toe of the toe, which increases the toe of the toe. On the contrary, this will affect the protection performance of the shoe cover. When subjected to impact or impact, the front toe of the shoe is tilted forward, so that the front cover of the shoe cover is lower than the rear edge of the shoe cover.
Because the design of most safety shoes is designed to transmit impact force and pressure through its front shell, if its front shell is pressed lower than the rear edge of the shoe head, then its force transfer mechanism cannot work effectively. The trailing edge will suffer serious deformation.
There is also a feature of the sole component that can also affect the protection ability of the shoe toe cap, which is cut along the width of the sole, vertical and horizontal section view of the surface of the upper surface. The shoe upper material that is recessed into the sole here increases the gap in the middle of the head of the safety shoe, so that the amount of deformation of the shoe head is greater when it is subject to possible damage.
Footbed pads The majority of safety shoes have a footbed pad, usually a fixed footbed. However, if the insole covers the entire length of the sole, then no doubt it also extends into the protective space under the head of the shoe. This reduces the internal clearance of the shoe toe and has a detrimental effect on the protection provided by the shoe toe cap. Therefore, it may be considered to thin the toe area of ​​the insole. Once the interior clearance of the shoe toe has been assessed to meet the requirements, do not change the insole.
Anti-puncture midsole For various reasons, the puncture-resistant midsole usually does not cover the entire width of the sole. The relevant requirements of the EN ISO 20344 series also allow at least 6.5 mm between the edge of the puncture-resistant midsole and the edge of the midsole. distance. However, in the case of compression, the hems of the shoe cover may slip past the outer edge of the anti-puncture midsole into the sole. Then the anti-puncture midsole is picked up inside the shoe cover and, because the anti-puncture midsole is under a flat force, it deforms upwards and presses against the interior space of the shoe toe.
In order to improve the performance of impact resistance and compression resistance tests, the anti-puncture midsole must be fixed to the sole so that it is fully pressed under the heel of the shoe cover. Thus, at the time of testing, it will become the base of the shoe head and prevent the shoe head from sinking into the sole when it is compressed. In addition, the hem of the shoe toe should be placed completely on top of the puncture-proof bottom plate to prevent it from moving into the hem of the shoe toe during the test.
Finally, there is an important point, in the production process to correctly install the shoe cap on the shoe last. Poor installation may result in displacement of the shoe's toe, causing serious instability in performance.
Nowadays, the types of shoes and the choice of materials used are much more than before. Safety shoe manufacturers have to choose from the established product market and product use, and ensure that the design of the footwear can play its maximum degree of protection.
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