起重机的用途与历史

起重机的用途与历史(中文6300字,英文3700字)
每当我们看到一台正在运作的起重机，我们都会惊讶不已，这些机器有时硕大无比，能把成吨的货物提升到半空中。看到这些庞然大物的时候我们心理都带着一种惊愕，有时甚至是有一点恐惧的心情，我们会去想如果吊着着的东西掉下来了或者是起重机吊错了位置会发生什么样恐怖的事情。起重机的确是一种令人着迷的机械系统，无论是成人或者是孩子无不为止惊叹。起重机的种类五花八门，并且历史悠久。起重机是用一个或者几个简单的机器来组成一个机械结构并用于运送那些人无法搬动的物品。一般来说，起重机由一个卷筒、一束金属绳或者是一条金属链组成用来同时提升、放置或者是水平移动货物。起重机的工作领域一般是在需要装卸货物的运输业、需要搬运建材的建筑业和需要组装重型设备的制造业。

The Use and History of Crane
Every time we see a crane in action we remains without words, these machines are sometimes really huge, taking up tons of material hundreds of meters in height. We watch with amazement and a bit of terror, thinking about what would happen if the load comes off or if the movement of the crane was wrong. It is a really fascinating system, surprising both adults and children. These are especially tower cranes, but in reality there are plenty of types and they are in use for centuries. The cranes are formed by one or more machines used to create a mechanical advantage and thus move large loads. Cranes are equipped with a winder, a wire rope or chain and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight, in the construction industry for the movement of materials and in the manufacturing industry for the assembling of heavy equipment.