保护性鞋包头通常被装置在能提供抗冲击和耐压缩作用的成品鞋中。传统的鞋包头一般是钢包头，也有一些是铝制的鞋包头，而近年来，塑料鞋包头或非金属合成鞋包头也逐渐进入市场。
        与钢包头相比，铝制包头及非金属合成包头比较轻，但价格通常也贵得多。然而，它们在特定的用途上确实有它们的优点，包括在对磁敏感的电子厂和石化工业中的使用等。用合成包头和塑料包头的安全鞋也普遍使用在机场，因为它们的非金属特性在通过安检区域的时候可以将对金属的干扰降至{zd1}。
        
        目前，全球根据安全鞋鞋包头具体的保护性能水准有几种不同的测试标准和认证要求。其中包括加拿大依据z195-02标准进行的CSA认证，美国的ASTM F2413-05标准（该标准在近年取代了ANSI Z41-1999标准），以及适用于欧盟地区的个人防护装备（PPE）指令89/686/EEC的相关法规。
        以上所有标准和法规都要求鞋包头作为成品鞋内部的一部分来进行测试评估。
        
        欧洲标准的要求
        个人防护装备指令CE标准的要求包含对成品例如成品鞋和服装的要求，不适用于配件、材料和零部件。因此，鞋包头本身是不可能申请CE标准的。
        然而，鞋包头可被当作零部件来进行测试，使用专门为鞋包头设定的欧洲标准EN 12568：1998的要求和测试方法。此标准的测试条件与成品鞋的测试标准EN ISO 20345相类似，但对冲击压缩后的间隙要求更高，以抵消可能由比较软的鞋底向上挤压而导致的间隙缩小。
        EN 12568标准涵盖了鞋包头抗冲击和耐压缩的性能（如图1和图2），也包括对鞋包头的测量标准，和金属鞋包头的防腐蚀性能。
        封于非金属的鞋包头，其抗冲击性能要通过几种不同的预处理之后进行测试，例如高温和低温预处理后的抗冲击测试以及经过几种不同的化学品处理后的抗冲击测试。
        封于制造销往欧洲市场的成品鞋的制造商而言，我们强烈建议他们只采购符合EN 12568测试标准的鞋包头。可能的话，要求鞋包头的供应商提供其产品通过由ISO 17025标准审核的第三方测试机构（如SATRA）所签发的测试报告。对于非金属鞋包头，欧洲安全鞋标准（EN ISO 20345及EN ISO 20346）要求成品鞋只能使用符合EN 12568标准第4.3款要求等类型的鞋包头。
        先不谈要达到的标准，鞋包头的设计对好的性能来说也是非常重要的。基于“防护空间”原理，鞋包头的设计必须使得它有足够的强度，在一定的范围内限制其破裂或变形，即根据相关标准进行冲击或压缩测试时，鞋包头不会被压碎或被压变形。
        除了鞋包头的材料强度、厚度和形状以外，沿着鞋包头底部边缘形成的褶边宽度也是一个重要因素，因为这个褶边可以帮助鞋包头将其受到的压力转移到支撑它的鞋底上。另外一个重要的特征就是鞋包头的内部深度，鞋包头越深，在冲击时它的可变形量就越大，对穿着者的保护就越好。
        不同标准的耐压缩测试（如ASTM、CSA、EN）都是非常相似的，而抗冲击测试则因冲击包头的形状、冲击的能量以及标准要求的冲击后的最小间隙等因素的不一样而有些许改变。
        明显地，实际使用的鞋包头的规格和性能对任何安全鞋能提供的保护能力是至关重要的因素。然而，安全鞋本身的设计和结构也反过来影响着鞋包头的性能，这就是为什么要从成品鞋上把鞋包头部分取下来做测试，因为只有这样才能测试出鞋包头对穿着者的实际保护水平。
        
        影响鞋包头性能的因素
        鞋包头的性能可能会受到其他各种因素的影响。根据工作中的保护空间原理，不仅是鞋包头必须有足够的强度，鞋底也应该能在受压力或冲击时于鞋包头的褶边下马上形成必要的支撑强度，以便受冲击力可以有效地转移到地面上，而不会导致鞋底上方的鞋包头等其他零配件在受力后陷入鞋底里。
        
        基于这个原因，可以说如果鞋底的配方的硬度相对大些，它对鞋包头的支撑就更有效些。另外一个需要考虑的因素就是，设计的时候鞋底要与鞋包头边缘保持在一直线上，而且鞋底要有齿纹。这是因为鞋底齿纹间的间隔区域不能提供很好的支撑，因此可能的话尽量避免鞋包头边缘与鞋底齿纹的间隔区域重合。
        另外一个可能影响鞋包头保护能力的鞋底设计特征，是鞋底的总厚度朝鞋头的方向逐渐减少，这就增加了鞋头跷度。相反地这会影响鞋包头的保护性能，在受到冲击或撞击的时候前跷的鞋头向前倾，因而使得鞋包头的前壳低于鞋包头后缘。
        因为多数安全鞋鞋包头的设计是通过它的前壳传导冲击力和压力，如果它的前壳被压低到低于鞋包头后缘，那么它的力转移机制就不能有效地起作用，鞋包头后缘就会遭受严重的变形。
        还有一个鞋底组成部分的特征也能影响鞋包头的保护能力，那就是沿鞋底宽度切下，纵横切面看到的鞋面表面的纵断面。此处凹入鞋底的鞋面材料增加了安全鞋鞋包头中间的间隙，因此鞋包头的变形量在受到可能发生的伤害时会更大一些。
        
        脚底的鞋床护垫
        大多数安全鞋都有鞋床护垫，通常是一个合脚的固定鞋垫。然而，如果鞋垫覆盖了鞋底的整个长度，那么毫无疑同地它也延伸到了鞋包头下方的防护空间里。这就减少了鞋包头的内部间隙，而对鞋包头能提供的保护作用产生不良的影响。因此，可以考虑将鞋垫的鞋头部位打薄。一旦鞋包头的内部间隙被评估符合要求，就不要再改变鞋垫。
        
        防穿刺中底
        由于各种原因，防穿刺中底通常不覆盖鞋底的整个宽度，EN ISO 20344系列标准的相关要求也允许防穿刺中底的边缘和拉帮中底的边缘之间有至少6.5mm的距离。然而，在受压缩的情况下，鞋包头的褶边有可能会越过防穿刺中底的外沿而陷入鞋底中。然后防穿刺中底就会在鞋包头里面跷起，并且，因为防穿刺中底此时是平面受力的，它就会向上变形并挤压鞋包头的内部空间。
        为了提高抗冲击和耐压缩测试的性能，防穿刺中底必须固定在鞋底上，使得它xx被压在鞋包头褶边的下面。这样，在测试的时候，它就会成为鞋包头的底座，并阻止鞋包头在被压缩的时候陷入鞋底中。另外，鞋包头的褶边还要xx放置在防穿刺中底板的上面，以防止它在测试的时候移动而跷进鞋包头的褶边里面。
        {zh1}还有重要的一点，在生产过程中要将鞋包头正确地安装在鞋楦上。安装不好的话可能导致鞋包头位移，以致性能的严重不稳定。
        现在，鞋包头种类和所用材料的选择都比以前多了很多。安全鞋制造商就要以既定的产品市场以及产品用途进行选择，并确保鞋类的设计能发挥其{zd0}程度的保护作用。
        
        有关更多安全鞋鞋包头测试的资讯，搜索网站www.satra.co.uk。也可通过电话或电邮直接联络SATRA鞋业有关负责人Lynne Brent。电话：+44 (0) 1536 410 000，电邮：footwear@satra.co.uk
        
        
        作者简介
        Austin Simmons先生于2009年7月1日接替刚退休的Richard Turner，任职SATRA技术中心总裁，Austin从事消费品测试与研究长达20年，并在SATRA工作了12年之久。在2007年，Austin任职SATRA副总裁，直接负责技术中心消费者产品与工业产品部门的战略开发工作。现在，他正在为SATRA所有成员而努力。Austin Simmons先生是SATRA成立90年以来第7任总裁。
        
        Standards for safety footwear toe caps
        
        Protective toe caps are generally fitted to footwear designed to provide impact and compression resistance. Traditionally, these have been made from steel, although aluminium types are available. In recent years, plastic or composite non-metallic materials have also entered the marketplace.
        Both composite and aluminium products are lighter than comparable steel versions, but are generally more expensive. However, they do have advantages in specialist applications, including the magnetic-sensitive electronics and petrochemical industries. Composite or plastic toe caps are also popular for use at airports, as their non-metallic properties minimise disruption when entering scanned security zones.
        Globally, there are several standards and certification requirements for safety footwear which specify protective qualities for toe caps. These include the Canadian CSA certification scheme based on Z195-02, ASTM standard F2413-05 and the Personal Protective Equipment (PPE) Directive 89/686/EEC legislation covering the European Economic Area. All require the toe cap to be assessed as an integral part of the footwear.
        
        European requirements
        The PPE Directive CE-marking requirements cover whole products such as finished footwear and garments, and do not apply to sub-assemblies, materials and components. Therefore, it is not possible to CE-mark toe caps.
        However, toe caps can be tested as components using European standard EN 12568 - 'Requirements and test methods for toe caps'. This uses similar conditions to those applied to the completed footwear when assessed against EN ISO 20345, but requires higher clearances to compensate for potential compromises relating to the softer footwear outsole base.
        EN 12568 covers performance of the cap when subject to impact and compression forces. It also includes criteria for the dimensions and corrosion resistance of the metal. For caps produced from a material other than metal, the impact test is repeated after various types of pre-conditioning, such as at high and low temperatures, plus exposure to a variety of chemicals.
        When making footwear for Europe, manufacturers are strongly advised to only source caps that comply with EN 12568 and, where possible, seek evidence of third party testing from an ISO 17025 accredited test organisation such as SATRA. For non-metallic caps, the European safety footwear standards (EN ISO 20345 and EN ISO 20346) require the footwear to include only those types of cap that comply with clause 4.3 of EN 12568.
        Regardless of the standard to be achieved, the toe cap design is crucial to good performance. Working on the 'defended space' principle, the design must provide adequate strength to limit fracture or distortion to such an extent that toes are not crushed when impacted or compressed in accordance with the standards.
        In addition to material strength, thickness and shape, the width of the flange along the bottom edge of the toe cap is an important element, as this helps transmit forces to the supporting outsole. Another important property of the toe cap is internal depth. The deeper it is, the more it can distort during the impact or crush before starting to impinge on the wearer's toes.
        While the compression tests in the various standards (such as ASTM, CSA and EN) are very similar, the impact tests do vary slightly in terms of the shape of the striker used to impact the cap, the energy of the impact and the minimum clearance required beneath the cap.
        Clearly, the specification and performance of the actual toe cap plays a vital role in the level of protection afforded in any safety footwear. However, the design and construction of the footwear itself can adversely influence the performance of the toe cap, which is why testing it in situ is the only way to determine the true level of protection offered to a wearer.
        Compromising performance
        The performance of toe caps can be compromised in several ways. For the defended space principle to work, not only must it have the necessary strength, but the outsole complex immediately below the cap flange must provide the required support so that the crushing or impact force is efficiently transferred to the ground without the component becoming embedded in the outsole.
        For this reason, the support to a toe cap will be more effective if the outsole is produced from a relatively hard compound. Another consideration when designing the outsole will be the alignment of the back edge of the cap, with any cleats in the outsole. This is because the area directly above gaps in the cleats will not provide a high level of support to the component and, therefore, where possible, the gaps should not coincide with the back edge.
        Another outsole design feature (which can affect toe protection) is a gradual reduction in overall thickness towards the toe, increasing the degree of toe spring. This can adversely affect the performance of the cap during an impact or crushing incident, as the toe spring allows it to roll forward so that the front wall is lower than the back edge.
        Many safety toe caps are designed to transmit forces via the front wall. If this is lowered below the back edge, the force transfer mechanism cannot work effectively and the back edge is subject to severe distortion.
        Another feature of the outsole complex that can affect toe protection is the profile of the upper surface when viewed in cross section across the width of the outsole. Here, a concave upper surface will increase the central clearance depth under the safety cap, thereby allowing more distortion of the product before injury to the toes is likely to occur.