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关键词：: 10T 桥式起重机总体设计 cad图纸

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10T桥式起重机总体设计

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目录I

序言1

第1章桥式起重机的概述2

1.1 桥式起重机分类及工作特点2

1.2 桥式起重机的用途4

1.3 桥式起重机的基本参数5

1.4 桥式起重机主要零部件6

1.4.1吊钩6

1.4.2钢丝绳8

1.4.3 滑轮和滑轮组10

1.4.4 滑轮组类型及选配原则11

1.5滑轮组及其滑轮组的倍率12

1.6 卷筒13

1.7 位置限位器13

1.8 缓冲器14

1.9桥式起重机发展概述15

1.9.1 国内桥式起重机发展动向15

第2章大车运行机构的设计17

2.1大车运行结构设计的基本思路及要求17

2.2 大车运行机构传动方案的确定17

2.3 大车运行机构具体布置时要注意的问题18

2.4 大车运行机构的设计计算18

2.4.1 大车运行结构的传动方案19

2.5轮压计算及强度验算20

2.5.1计算大车的最大轮压和最小轮压：20

2.5.2 强度计算及校核21

2.6 运行阻力计算23

2.7 选择电动机24

2.8 减速器的选择25

2.9 验算运行速度及实际功率25

2.10 验算启动时间26

2.11 起动工况下校核减速器功率28

2.12 验算起动不打滑条件28

2.13 选择制动器31

2.14 选择联轴器32

2.15 低速浮动轴的验算32

2.16 缓冲器的选择34

第3章起升小车的计算36

3.1 确定机构的传动方案36

3.2小车运行机构的计算37

3.3选择车轮与轨道并验算起强度37

3.4运行阻力计算39

3.5 选电动机40

3.6 验算电动机发热条件41

3.7 选择减速器41

3.8 验算运行速度和实际所需功率42

3.9验算起动时间42

3.10 按起动工况校核减速器功率43

3.11 验算起动不打滑条件44

3.12 选择制动器45

3.13 选择高速轴联轴器及制动轮45

3.14 验算低速浮动轴强度47

3.15 起升机构的设计参数48

3.16 钢丝绳的选择49

3.17 滑轮、卷筒的计算51

3.18 根据静功率初选电动机52

3.19 减速器的选择53

3.20 制动器的选择54

3.21 启动时间及启动平均加速度的验算54

3.22 联轴器的选择55

第4章桥架结构的设计57

4.1 桥架的结构形式57

4.1.1 箱形双梁桥架的构成57

4.1.2 箱形双梁桥架的选材57

4.2 桥架结构的设计计算58

4.2.1 主要尺寸的确定58

4.2.2 主梁的计算60

4.3 端梁的计算66

4.4 端梁的尺寸的确定70

4.4.1 端梁总体的尺寸70

4.4.2端梁的截面尺寸70

第5章端梁接头的设计72

5.1 端梁接头的确定及计算72

5.1.1 腹板和下盖板螺栓受力计算73

5.1.2 上盖板和腹板角钢的连接焊缝受力计算74

5.2 计算螺栓和焊缝的强度75

5.2.1 螺栓的强度校核75

5.2.2 焊缝的强度校核76

第6章焊接工艺设计78

参考文献81

致谢82

摘要

　　　本次毕业设计是针对毕业实习中桥式起重机所做的具体到吨位级别的设计。我国现在应用的各大起重机还是仿造国外落后技术制造出来的，而且已经在工厂内应用了多年，有些甚至还是七八十年代的产品，无论在质量上还是在功能上都满足不了日益增长的工业需求。如何设计使其成本最低化，布置合理化，功能现代化是我们研究的课题。本次设计就是对小吨位的桥式起重机进行设计，主要设计内容是10t桥式起重机的结构及运行机构，其中包括桥架结构的布置计算及校核，主梁结构的计算及校核，端梁结构的计算及校核，主端梁连接以及大车运行机构零部件的选择及校核包括: 轮压计算及强度验算, 运行阻力计算,选择电动机,减速器的选择验算,运行速度及实际功率,选择制动器,选择联轴器,低速浮动轴的验算,缓冲器的选择等计算。还有小车的运行和起升机构零部件的选择及校核包括: 运行阻力计算，选电动机，选择减速器验算起动时间，按起动工况校核减速器功率，选择制动器，选择高速轴联轴器及制动轮，验算低速浮动轴强度，钢丝绳的选择，滑轮、卷筒的计算，联轴器的选择。

关键词: 起重机；大车运行机构；小车运行结构；小车起升结构；桥架；主端梁。

Abstract

　　　The graduation design is aimed at the graduation fieldwork medium-sized crane do specific to tonnage level of design. Our country is the application of the big crane or counterfeit foreign backward technology out of manufacture and has within the plant for many years, some even application or the 70s and 80s products, both in quality and in on the function can't satisfy the growing industrial demand. How to design makes it the lowest cost, decorate rationalization, functional modernization is our topic. This design is on small tonnage design of bridge crane, the main design content is 10t bridge crane structure and operation organization, including bridge structure arrangement calculation and checking the structure of the girder, the calculation and checking, calculated and checked the beam structure, the main girders connection and cart mechanism parts selection and checking including: wheel pressure calculation and intensity checking, running friction calculation, the choice of motor, gear reducer is checked, choose speed and actual power, choose brakes, choose coupling calculating speed floating axis, buffer choice calculation, etc. And car running and lifting mechanism parts selection and checking including: running friction calculation, choose motor, choose reducer, by starting checked start-up time check reducer power, choose working brakes, choose high-speed couplings and brake wheel, the checking low-speed axial intensity, the wire rope floating choice, pulley, drum calculation, coupling choice.

Keywords: cranes; During operation organization; Car running structure; Car hoisting structure; Bridge; Main girders.

序言

　　　桥式起重机是横架于车间和料场上空进行物料调运的起重设备。由于它两端坐落在高大的水泥柱或金属架上，形状似桥，所以俗称“天车”。桥式起重机是现代工业和起重运输中实现生产过程机械化、自动化的重要工具与设备，可减轻操作者的劳动强度，可大大提高生产率。桥式起重机在工矿企业、钢铁化工、铁路交通、港口码头以及物流周转等部门和场所应用的最为广泛，是人们生产生活不可或缺的一种设备。

　　　随着工业的迅速发展和科学技术的不断进步，桥式起重机在结构设计及自动化程度上相继出现了一些新的变化和新的特点，在结构上，国内起重设备已采用计算机优化设计，以提高起重机的机械性能，在起重质量方面逐步向大型化发展，大型桥式起重机正在钢铁、水利、发电等行业不断出现，令人世人瞩目的三峡发电厂安装了两台1200T/125T的桥式起重机，2007年9月，起重量达2万吨的桥式起重机在山东烟台佛士船厂投入使用，它标志这我国起重机行业以达到世界先进水平。

　　　总之，随着科技的迅速发展，国内各种先进的电气控制和机械技术正逐步应用到起重机上，起重机的自动化程度越来越高，结构日趋简单，性能愈加可靠，起重量越来越大，品种也越来越全。

　　　对于起重量大、跨距大的起重设备多采用箱型双梁式，箱型双梁桥式起重机有一个由两根箱型主梁和两根横向端梁构成的双梁桥架，在桥架上运行小车，可起吊和水平搬运各类物件。它适用于机械加工和装配车间、仓库和料场等场所。箱型双梁结构具有加工零件少、工艺性好、通用性好及安装检修方便等优点，因而在生产中广泛使用。

第1章桥式起重机的概述

　　　桥式起重机是桥架型起重机的一种，主要依靠起升机构和在水平面内的两个相互垂直方向移动的运行机构，能在矩形场地及其上空作业，是工矿企业广泛使用的一种其中运输机械。它具有承载能力大、工作可靠性高、制造工艺相对简单的优点。

桥式起重机一般有大车运行机构的桥架、起升机构和小车运行机构的起重小车、电气设备、司机室等机构组成，外形像一个两端支撑在平行的两条架空轨道上平移运行的单跨平板桥。起升机构用来垂直升降物品，起重小车用来带着载荷作横向移动，以达到在跨度内和规定高度内组成三维空间里做搬运和装卸货物用。

桥式起重机是使用最广泛、拥有量最大的一种轨道运行式起重机，其额定起重量从及吨到几百吨。最基本的形式是通用吊钩桥式起重机，其他形式的桥式起重机都是在通用吊钩桥式起重机的基础上派生发展出来的。

1.1 桥式起重机分类及工作特点

　　　桥式起重机的外观像一条金属的桥梁，所以人们称它为桥式起重机。桥式起重机俗称“天车”、“行车”。桥式起重机一般由装有起升机构和小车运行机构的桥架，大车运行机构，操纵室，小车导电装置，起重机总电源导电装置组成。

桥式起重机是在固定的跨间内装卸和搬运物料的机械设备，被广泛用于车间、仓库或者露天场地。

1.桥式起重机的分类

　　　随着工业技术的不断发展，桥式起重机的种类越来越多，根据使用吊具不同，可分为吊钩式起重机，抓斗式起重机和电磁吸盘式起重机，根据用途不同，可分为通用桥式起重机、冶金专用桥式水电站用桥式起重机、大起升高度桥式起重机等。

按主梁结构形式可分为：箱型结构桥式起重机、桁架结构桥式起重机、管型结构桥式起重机。还有型钢和钢板制成的简单截面梁的起重机，称为梁式起重机。

2.桥式起重机的工作特点

　　　起重机是以间隙、周期的工作方式，通过起重吊钩或其他取物装置的起升或起升加移动重物的机械设备。

综合起重机械的工作特点，，从安全技术角度分析，可概括如下：

（1）其中机械通常结构庞大，机构复杂，能完成一个起升运动、一个或几个水平运动。例如，桥式起重机能完成起升呢个、大车运行和小车运行3个运动。在作业过程中，常常是几个不同方向的运动同时操作，技术难度较大。

（2）所吊运的重物多种多样，载荷是变化的。有的重物重达几百吨乃至上前吨，有的物体长达几十米，形状也很不规则，有散粒、热融状态、易燃易爆危险品等，吊运过程复杂而危险。

（3）桥式起重机需要在较大的空间范围内运行，要装设轨道和车轮，活动空间较大，一旦造成事故其影响的范围也较大。

暴露、活动的零部件较多，且常与吊运作业人员直接接触（如吊钩、钢丝绳等），潜在许多偶发的危险因素。

（4）作业环境复杂。从大型钢铁、冶金、石化企业到现代化港口、建筑工地、铁路枢纽等，都有桥式起重机机械在运行；作业场所常常会遇有高温、高压、易燃易爆、输电线路、强磁等危险因素，对设备和作业人员形成威胁。

（5）作业中常常需要多人配合，共同进行。一个操作，要求指挥、困扎。驾驶等作业人员配合熟练、动作协调、互相照应。作业人员应有处理现场紧急情况的能力。多个作业人员之间的密切配合。通常存在较大的难度。

（6）起重机的上述工作特点，决定了他与安全生产的关系重大。如果对起重机的设计制造、安装使用和维修等环节上稍有疏忽，就有可能造成伤亡或设备事故。一方面造成人员的伤亡，另一方面也会造成很大的经济损失。

1.2 桥式起重机的用途

　　　桥式起重机的用途和使用范围很广。它广泛应用在工业企业、港口车站、仓库料场、水电站等国民经济个部门。在冶金企业中，从原料进厂、冶炼轧制到产品出厂都需要大量的桥式起重机、加料起重机、铸造起重机等，如一个300吨转炉炼钢车间所需起重机有几十台。一个大型冶金联合企业用有数百台之多的各种类型起重机。在港口码头上，船舶货物的装卸及搬运作业，主要依靠各种起重机来完成。在一个年吐量为1500多万吨的货物港口，就约100多台各种起重机，其中，桥式起重机占有相当大的比例，在电力工业中，各种水火电站和核电站就需要大起重量的桥式起重机。在机械制造业中，企业车间内部、露天场地、仓库等场合大量应用着各种桥式起重机。

　　　不同类型的桥式起重机所搬运的物料不同：吊钩起重机搬运各种成件物品；抓斗起重机搬运各种散粒物品，如煤、焦炭、砂等；电磁起重机搬运导磁的金属材料，如型钢、钢板、废钢等；两用起重机是为了生产效率，在一台小车上装有可换的吊钩和抓斗或者电磁吸盘和抓斗，但每一个工作循环只能使用其中的一种取物装置，可运送成件、散粒物品或者到此的金属材料，但每次搬运物品时，只能使用其中一种；防爆起重机用于搬运有易爆气体或有易爆介质的车间、库房等场所的成件物品，起重机上的电气设备和有关装置具有防爆特性，以免发生火花；绝缘起重机用于搬运电解车间的各种成件物品，起重机上有关部分具有可靠的绝缘装置，保证安全操作。

1.3 桥式起重机的基本参数

　　桥式起重机的技术参数是桥式起重机工作性能的指标。桥式起重机的主要技术参数包括：起重量、跨度、起升高度、各机构的工作速度以及工作级别等，为了保证桥式起重机的合理使用、安全运行和防止事故的发生，桥式起重机司机必须掌握桥式起重机的技术参数。

主要参数：

起重量

起重量是指被起升重物的质量，用G表示。

（1）额定起重量起重机所允许吊起的最大重物或者物料的质量称为额定起重量，用Cn表示，单位用吨（t）,额定起重量不包括吊钩、吊环之类吊具的质量，但包括抓斗、电磁盘、盛钢桶、料罐之类可分吊具的质量。

（2）总起重量起重机能吊起的重物或物料，连同可分吊具和长期固定在起重机上的吊具或属具（包括吊钩、滑轮组、起重钢丝绳…….）等质量总和，总起重用Gt表示。

跨度和轨距

　　　桥式起重机的大车运行轨道中心线之间的距离称为桥式起重机的跨度，用L表示，单位为m。桥式起重机的小车运行轨道两条钢轨中心线之间的距离为小车轨距，用t表示，单位为m,跨度依厂房的而定。

起升高度

　　　起升高度是桥式起重机取物装置上下移动极限位置之间的距离，用H表示，单位为m。下极限位置通常以工作场地的地面为准，上极限的位置，使用吊钩时以钩口中心为准，使用抓斗时以抓斗最低点为准。

工作速度

　　　工作速度是指起重机个机构（起升、运行）的运行速度，其中：额定起升速度是指起升机构的电动机在额定转速下，取物装置的上升速度；小车额定运行速度是指小车运行机构电动机在额定转速下的小车运行速度；大车额定运行速度是指大车运行机构的电动机在额定转速下的运行速度。各类速度用v表示，单位为m/min。桥式起重机的工作速度根据工作要求而定：一般用途的桥式起重机采用中等的工作速度，这样可以使驱动电机功率不致过大；安装工作有时就要求很低的工作速度；吊运轻件，要求提高生产效率，可取较高的工作速度啊；吊运重件，要求工作平稳，作业效率不是主要矛盾，可取较低的工作速度。

起重机的总质量G

包括燃料、油液、润滑剂和水等在内的起重量各部分质量的总和，单位用t表示。

外形尺寸

外形尺寸指起重机长、宽、高的的尺寸，单位用m表示。第2章大车运行机构的设计

2.1大车运行结构设计的基本思路及要求

　　　大车运行机构的设计通常和桥架的设计一起考虑，两者的设计工作要交叉进行，一般的设计步骤：

1. 确定桥架结构的形式和大车运行机构的传方式；

2. 布置桥架的结构尺寸；

3. 安排大车运行机构的具体位置和尺寸；

4. 综合考虑二者的关系和完成部分的设计。

对大车运行机构设计的基本要求是：

1. 机构要紧凑，重量要轻；

2. 和桥架配合要合适，这样桥架设计容易，机构容易布置，且使总体结构设计和布置不至于过大；

3. 尽量减轻主梁的扭转载荷，不影响桥架刚度；

4. 维修检修方便，机构布置合理，使司机和维护人员上下要方便，便于拆装零件及操作。

2.2 大车运行机构传动方案的确定

大车机构传动方案可分为两类：即分别传动和集中传动，桥式起重机的跨度介于10.5m-32m范围内可用分别传动的方案，本设计采用分别传动的方案。

2.3 大车运行机构具体布置时要注意的问题

1. 联轴器的选择；

2. 轴承位置的安排；

3. 轴长度的确定；

这三者是互相联系的，在设计过程中要考虑到其中各个部分的配合，做到相互兼顾，充分发挥各个零部件的作用。

在具体布置大车运行机构的零部件时应该注意以几点：

（1）因为大车运行机构要安装在起重机桥架上，桥架的运行速度很高，而且受载之后向下挠曲，机构零部件在桥架上的安装可能不十分准确，所以如果单从保持机构的运动性能和补偿安装的不准确性着眼，凡是靠近电动机、减速器和车轮的轴，最好都用浮动轴。

（2）为了减少主梁的扭转载荷，应该使机构零件尽量靠近主梁而远离走台栏杆；尽量靠近端梁，使端梁能直接支撑一部分零部件的重量。

（3）对于分别传动的大车运行机构应该参考现有的资料，在浮动轴有足够的长度的条件下，使安装运行机构的平台减小，占用桥架的一个节间到两个节间的长度，总之考虑到桥架的设计和制造方便。

（4）制动器要安装在靠近电动机，使浮动轴可以在运行机构制动时发挥吸收冲击动能的作用。

　　　参照以上所述，由于所设计的参数级别较大，跨度中等，所以采用分别传动方案。

2.4 大车运行机构的设计计算

设计数据：

　　　起重机的起重量Q=10T，桥架跨度L=16.5m，大车运行速度Vdc=80m/min，工作类型为中级，机构运行持续率为JC%=25，起重机的估计重量G=168KN，小车的重量为Gxc=40KN，桥架采用箱形结构。

　　2.4.1 大车运行结构的传动方案

　　　　经各方面综合考虑传动方案选用分别驱动，其传动路线如下图2-1所示

参考文献

[1] 《起重机设计手册》起重机设计编写组，机械工业出版社，1980

[2] 《机械设计师手册》吴宗泽主编机械工业出版社，2002

[3] 《起重机课程设计》陈道南、盛汉中主编冶金工业出版社，1983

[4] 《焊接手册》中国机械工程学会焊接学会编，机械工业出版社，1992

[5] 《起重运输机械》张质文、刘全德中国铁道出版社 1983年

[6] 《机械原理》孙桓、陈作模高等教育出版社 1996年

[7] 《工程起重机》顾迪民中国建筑工业出版社，1988

[8] 《机械设计》濮良贵、纪名刚高等教育出版社，2000.12

[9] 《机械零件手册》周开勤高等教育出版社，2000.12

[10] 《机械设计课程设计手册》吴宗泽、罗圣国高等教育出版社，2006.5

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内容简介：: 河南理工大学万方科技学院本科毕业论文The Use and History of CraneEvery 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.1. OverviewThe first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first mechanical power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.Cranes exist in an enormous variety of forms each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. For a while, mini - cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships. This article also covers lifting machines that do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.2. HistoryAncient GreeceThe crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane. The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weights handled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favor of using several column drums. Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labor, making the crane more preferable to the Greek polis than the more labor-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria. The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then. Ancient RomeThe heyday of the crane in ancient times came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. We are relatively well informed about their lifting techniques, thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura 10.2, 1-10) and Heron of Alexandria (Mechanica 3.2-5). There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.The simplest Roman crane, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch, could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person). However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for instance, the architrave blocks weigh up to 60 tons each, and one corner cornice block even over 100 tons, all of them raised to a height of about 19 m. In Rome, the capital block of Trajans Column weighs 53.3 tons, which had to be lifted to a height of about 34 m (see construction of Trajans Column). It is assumed that Roman engineers lifted these extraordinary weights by two measures (see picture below for comparable Renaissance technique): First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica 3.5). Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals). This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan. Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans.Middle AgesDuring the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331. Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors. Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ships wheel. To smooth out irregularities of impulse and get over dead-spots in the lifting process flywheels are known to be in use as early as 1123. The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.Structure and placementThe medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier compass-arm wheel had spokes directly driven into the central shaft, the more advanced clasp-arm type featured arms arranged as chords to the wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage. Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground, often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults. Thus, the crane grew and wandered with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft. Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs.Mechanics and operationIn contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place, or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall. Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. While ashlar blocks were directly lifted by sling, lewis or devils clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels. It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control. Harbor usageAccording to the present state of knowledge unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages. The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards. Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. Interestingly, dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe.28 Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century. RenaissanceA lifting tower similar to that of the ancient Romans was used to great effect by the Renaissance architect Domenico Fontana in 1586 to relocate the 361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture. Early modern ageCranes were used domestically in the 17th and 18th century. The chimney or fireplace crane was used to swing pots and kettles over the fire and the height was adjusted by a trammel. 3. Mechanical principlesThere are two major considerations in the design of cranes. The first is that the crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.Lifting capacityCranes illustrate the use of one or more simple machines to create mechanical advantage.The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point called the fulcrum. The principle of the lever allows a heavy load attached to the shorter end of the beam to be lifted by a smaller force applied in the opposite direction to the longer end of the beam. The ratio of the loads weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical advantage. The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. This number is the mechanical advantage. The hydraulic cylinder. This can be used directly to lift the load or indirectly to move the jib or beam that carries another lifting device. Cranes, like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy (in practice slightly less, because some energy is lost to friction and other inefficiencies).StabilityFor stability, the sum of all moments about any point such as the base of the crane must equate to zero. In practice, the magnitude of load that is permitted to be lifted (called the rated load in the US) is some value less than the load that will cause the crane to tip (providing a safety margin).Under US standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2007 Mobile and Locomotive Cranes.Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail.4. Types of the cranesMobileMain article: Mobile craneThe most basic type of mobile crane consists of a truss or telescopic boom mounted on a mobile platform - be it on road, rail or water.FixedExchanging mobility for the ability to carry greater loads and reach greater heights due to increased stability, these types of cranes are characterized that they, or at least their main structure does not move during the period of use. However, many can still be assembled and disassembled.5. Overhead CranesUseThe most common overhead crane use is in the steel industry. Every step of steel, until it leaves a factory as a finished product, the steel is handled by an overhead crane. Raw materials are poured into a furnace by crane, hot steel is stored for cooling by an overhead crane, the finished coils are lifted and loaded onto trucks and trains by overhead crane, and the fabricator or stamper uses an overhead crane to handle the steel in his factory. The automobile industry uses overhead cranes for handling of raw materials. Smaller workstation cranes handle lighter loads in a work-area, such as CNC mill or saw.HistoryAlton Shaw, of the Shaw Crane Company, is credited with the first overhead crane, in 1874. Alliance Machine, now defunct, holds an AISE citation for one of the earliest cranes as well. This crane was in service until approximately 1980, and is now in a museum in Birmingham, Alabama. Over the years important innovations, such as the Weston load brake (which is now rare) and the wire rope hoist (which is still popular), have come and gone. The original hoist contained components mated together in what is now called the built-up style hoist. These built up hoists are used for heavy-duty applications such as steel coil handling and for users desiring long life and better durability. They also provide for easier maintenance. Now many hoists are package hoists, built as one unit in a single housing, generally designed for ten-year life or less.Notable cranes and dates1874: Alton Shaw develops the first overhead crane. 1938: Yale introduces the Cable-King hoist. 1944: Shepard-Niles supplies a hoist for lifting atomic bombs for testing in New Mexico. 1969: Power Electronics International, Inc. developed the overhead hoist variable speed drive. 1983: The worlds biggest overhead crane from Bardella Company starts its operation at Itaipu dam Hydro Power Plant Brazil. 1997: Industry giant P&H files for chapter eleven bankruptcy. Later renamed Morris Material Handling but still using the P&H tradename, they again went bankrupt. 1998: Dearborn Crane supplies two 500-ton capacity overhead cranes to Verson Press of Chicago. The cranes were never used due to Versons bankruptcy. 起重机的用途与历史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。1. 概况第一台具有机械结构的起重机是由古希腊人发明的，并且由人或者是牲畜比如驴，作为动力源。这种起重机被用于大型建筑的建造。这种起重机后来发展成了采用人力踏板驱动的更大型的起重机，用于提升更重的物料。中世纪时港口起重机被用来装卸船上的货物，有的港口起重机为求更大的起重重量和更好的稳定性被造在了石塔里。最早的起重机是用木头制造的，但是工业革命之后，铸铁和钢材就代替了木头用于制造起重机。尽管水磨机和风车都可以利用自然的能源来驱动，但是几个世纪以来，起重机的动力源一直是人力或者是畜力。第一台真正采用机械能量的起重机用的是蒸汽机，最早的蒸汽起重机出现于18到19世纪，有一些甚至到了20世纪末仍能很好地使用。虽然由于能源的供应仍不可及，到现在有一些人力起重机还在使用，但是现代的起重机一般采用的内燃机、电动马达、液压系统能为起重机提供比之前大得多的提升力。起重机的类型多种多样每一种都是量身定做。尺寸由最小的在车间里使用的臂式起重机到用于建造高楼的最高的塔式起重机应有尽有。然而，小型的起重机也被用来建造摩天大楼，目的是为了在高楼中狭小的空间内使用使建造更加方便。最后，我们来看看更加巨型的浮船式起重机，一般用来建造石油钻探平台和打捞沉没的船只。这篇文章也会涉及到之前没有提到，但是也非常常见的的起重机械，比如说堆垛起重机和装卸起重机。2. 历史古希腊时期用来提升重型货物的其中节是古希腊人在公元前六世纪晚期发明的。考古记录显示最早在公元前515年提升夹具和铁制的吊楔开始出现在古希腊人石块结构的神殿里。由于这些是起重设备的核心装置、也由于他们是在石块的重心的中央或者是在离重心上一点距离相等的两头被发现，他们被考古学家认为是起重机当时就存在的确凿证据。绞盘与滑轮的的引入导致了人类之前用斜坡来向高处运送货物的方法被广泛替代。在接下来的两百年中，希腊的建筑都采用了这样新型的提升物料的技术，它利用了一些小型的石块来来代替大块的石头，这样更具实用性。与更早先的古希腊人神殿的建筑材料的尺寸不断变得越来越大趋势相比较，希腊古典庙宇比如帕台农神庙的石块重量都小于1520吨。而且，要把巨型的石柱竖立起来的作业古希腊人实际上更喜欢用好几块像鼓一样的圆柱石块堆叠而成。尽管确切是何时从斜坡运输进入起重机提升技术时代的时间还不是很清楚。但是当时古希腊不稳定的社会局势、和政治情况使得建造神殿更适合雇佣小型的、更加专业的建筑团队而不是像埃及和亚述那样大量使用的没有技术的劳动力。这样的情况使得起重机更像是希腊城邦发明的而非是采用纯劳动力斜坡运送货物的埃及或是亚述那样的独裁国家。文学上第一次的明确的记载滑轮组的复合系统是出现在亚里士多德的机械难题中，但是组成文字可能还要稍晚一些。与此同时，用于建造希腊神庙的石块尺寸再一次开始赶上他们的古代前辈了，这标志着当时更多的久经考验的的滑轮组一定在希腊建筑史上找到了它们的一席之地。古罗马时期起重机械在古代的全盛时期却是在古罗马帝国展开的。当时建筑物的数量激增，而且这些建筑都达到了巨型的尺寸。罗马人采用了希腊人的起重机并将其发扬光大。多亏了那些维特鲁威工程师们撰写的相当冗长的文献和亚历山大大帝的苍鹭的巢，我们才得以如此详细地了解到了它们的其中技术。目前与Haterii的墓碑一起现存于世还有两座公元一世纪晚期、雕刻精细的古罗马脚踏式起重机的浮雕作品。三饼滑车是古罗马最简单的一种起重机，它是由一个单梁吊臂、一个绞盘、一条绳子和一个三个滑轮组成的滑轮组组成的。这样就有能够省下3倍的力。经计算，假设一个人用尽力气能够长时间地提起相当于重50千克的物体那么通过这样的起重机械他可以提升约150千克的物体（3个滑轮X50千克150千克）。更加重型的起重机就拥有五个滑轮（五饼滑车），最大型的起重机会在两根、三根甚至是四根桅杆上面装上三饼和五饼的复合滑轮组（复滑车），这是由最大的负载载荷决定的。复滑车工作的时候两边需要4个人：两边各站两个已经可以提起重约3000千克的物体（3条绳子X5个滑轮X4个人X50千克3000千克）。如果用踏车来代替绞盘的话，最大的起重载荷可以在人工减半的情况下达到两倍6000千克，因为踏车有更大的直径能够提供一个大得多的力矩。这意味着，和建造埃及金字塔时50个人才能通过斜坡搬动2.5吨的石块（50千克每人）的情况相比，罗马的复滑车的提升能力把工作的效率提高60倍（3000千克每人）。然而，大量现存的古罗马建筑中那些石块的重量比复滑车所能操作的负载要重得多。这表明古罗马人全面的起重的能力要远远任何简单的起重机。以Baalbek的Jupiter神庙为例，那些楣梁的石块每块都重达60吨以上，每个檐口的石块甚至达到了100吨以上，所有这些石料都被提升到了19m的半空中。在罗马Trajan之柱的主要石块重达53.3吨，而这些石块必须被提升到34m的高度。（见Trajian之柱）假定古罗马的建筑师们是用两种方法把这么巨型石块提起来的：第一种方法是由苍鹭之巢的暗示得来，首先一座起重塔矗立了起来，它四个桅杆以两条平行的边各一个的方式形成了一个方形的形状，不像一个围起来的塔，而是塔的中间有圆柱体。然后，大量的绞盘被放置在塔周围的地面上，因为虽然绞盘的杠杆比比踏车要低，但是绞盘可以安装在更高的地方由更多的人来驱动（此外还可以用牲畜）。这种大量绞盘的使用也被Ammianus Marcellinus记录和在Circus Maximus起升的Lateranense 方尖塔联系了起来。单个绞盘的最大起重量由在那些大石块上钻的抓取孔的数量决定。就拿Baalbek楣梁上那些重量在55到60吨的石块来说，八个明显的抓取孔表明了每个吊爪允许承受7.5吨的重量，这也是每一个绞盘所要承受的重量。以既定的动作来提升如此重量的物体需要各个施力于绞盘上的各个工作组之间有大力的协调和配合。中世纪时期在中世纪时，随着西罗马帝国的灭亡，西欧洲的科技技术水平一落千丈。这时踏车式的起重机再次被大范围地使用。最早的提到踏车式是大约1225年法国的一部档案文学作品，它在一份手稿上也说明叙述了直到1240年法国人的血统起源。在航海方面，最早使用港口起重机是在1244年的Utrecht、1263年的Antwerp、1288年的Brugge和1291年的Hamburg，而在英格兰踏车式的起重机直到1331年才有所记录。一般来说，采用起重机来垂直运输比传统的方法更加的安全和经济。典型的应用领域就包括港口、矿井。值得一提的是在哥特式大教堂的建造过程中，踏车式的起重机起到了一个不可或缺的重要作用。但是，档案和图画都显示了当时新引进的机械系统如踏车、独轮手推车等却没有完全替代那些楼梯、木桶、手推车等依赖劳动力的生产方法。这样，旧式的和新式的机械在继续在中世纪的建筑和港口共存。除了踏车，中世纪的文献中也记载了由手动驱动带幅轮和曲柄的绞盘的起重机，在15世纪时也是由卷扬机发展成为了类似船轮的系统。为了缓冲这些不规则的冲击力和解决提升过程中的死点问题，调速轮最早于1123年开始投入使用。踏车式起重机具体以何种方式再次被采用的已经无从考证，尽管它再次被使用在建筑领域是被毋庸置疑地认为和哥特式建筑的崛起有相当密切的关系。踏车式起重机的再次出现可能导致了卷扬机的技术发展，因为卷扬机在踏车式起重机的结构和机械方面都有所发展。中世纪的踏车可以看作是罗马Vitruvius De工程师设计品的一个精心改造品，它们可以在很多寺庙馆藏中看到。结构与使用地点中世纪的踏车结构是由一个木轮围绕在一根中心轴上，中心轴的两旁有足够宽的踏板以供两旁的工人踩踏。虽然以前的圆盘臂有轮辐可以直接用来驱动中心轴，但是更为先进的钩状臂更适合作为轮子边缘的弦来使用，这样可以用一个更细的轴来以供一个更大的机械利益。与常理相悖的是，中世纪建筑使用的起重机既不是安装在当时相当不可靠的脚手架上，也不是安装在哥特式教堂那纤细的墙上，那种墙不足以支撑起重机械和载荷的重量。当时的起重机是被安装在建筑物最初的底台上的，经常是在建筑物的内部。每当新的一层建成后，屋顶厚重的横梁和墙连在了一起，起重机被拆卸然后在那些在拱顶建造期间一根一根被搬运上来的顶梁上。这样，起重机就跟着建筑物一起升高和移动，这也是英格兰现存的建筑用起重机都是在保存在教堂的圆顶之上屋顶之下的原因，因为它们是建造完工后保留下来用来起吊屋顶维修的材料的。技巧与操作与现代的起重机相比，中世纪的起重机更像它们在希腊和罗马的祖先，它们主要的用途仅是用于垂直地起吊物体而不同时用于水平地长距离地移动物体。因此起吊的工作也在一个与现在不同的地方进行。比如说在建造建筑时，起重机只能要么直接从底部把石块吊到指定地点，要么是从它放置石块的墙对面的另一边起吊。因为两个工作组

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