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首页 » 经典英文小说 » The Economy of Workshop Mainipulation » CHAPTER XV. PNEUMATIC MACHINERY FOR TRANSMITTING POWER.
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CHAPTER XV. PNEUMATIC MACHINERY FOR TRANSMITTING POWER.
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Pneumatic machinery1, aside from results due to the elasticity2 of air, is analogous3 in operation to hydraulic4 machinery.

Water may be considered as a rigid5 medium for transmitting power, corresponding to shafts6 and gear wheels; air as a flexible or yielding one, corresponding to belts. There is at this time but a limited use of pneumatic apparatus7 for transmitting power, but its application is rapidly extending, especially in transporting material by means of air currents, and in conveying power to mining machinery.

The successful application of the pneumatic system at the Mont Cenis Tunnel in Italy, and at the Hoosac Tunnel in America, has demonstrated the value of the system where the air not only served to transmit power to operate the machinery but to ventilate the mines at the same time. Air brakes for railway trains are another example illustrating8 the advantages of pneumatic transmission; the force being multiplied at the points where it is applied9, so that the connecting pipes are reduced to a small size, the velocity10 of the air making up for a great force that formerly11 had to be communicated through rods, chains, or shafts. The principal object attained12 by the use of air to operate railway brakes is, however, to maintain a connection throughout a train by means of flexible pipes that accommodate themselves to the varying distance between the carriages. Presuming that the flow of air in pipes is not materially impeded13 by friction14 or angles, and that there will be no difficulty in maintaining lubrication for pistons15 or other inaccessible16 parts of machinery when driven by air, there seems to be many reasons in favour of its use as a means of distributing power in manufacturing districts. The diminished cost of motive17 power when [56] it is generated on a large scale, and the expense and danger of maintaining an independent steam power for each separate establishment where power is employed, especially in cities, are strong reasons in favour of generating and distributing power by compressed air, through pipes, as gas and water are now supplied.

Air seems to be the most natural and available medium for transmitting and distributing power upon any general system like water or gas, and there is every probability of such a system existing at some future time. The power given out by the expansion of air is not equal to the power consumed in compressing it, but the loss is but insignificant18 compared with the advantages that may be gained in other ways. There is no subject more interesting, and perhaps few more important for an engineering student to study at this time, than the transmission of power and the transport of material by pneumatic apparatus.

In considering pneumatic machinery there are the following points to which attention is directed:—

1. The value of pneumatic apparatus in reaching places where steam furnaces cannot be employed.

2. The use that may be made of air after it has been applied as a motive agent.

3. The saving from condensation19, to which steam is exposed, avoidance of heat, and the consequent contraction20 and expansion of long conducting pipes.

4. The loss of power by friction and angles in conducting air through pipes.

5. The lubrication of surfaces working under air pressure, such as the pistons and valves of engines.

6. The diminished cost of generating power on a large scale, compared with a number of separate steam engines distributed over manufacturing districts.

7. The effect of pneumatic machinery in reducing insurance rates and danger of fire.

8. The expense of the appliances of distribution and their maintenance.

In passing thus rapidly over so important a subject, and one that admits of so extended a consideration as machinery of transmission, the reader can see that the purpose has been to touch only upon such points as will lead to thought and investigation21, and especially to meet such queries22 as are most likely to [57] arise in the mind of a learner. In arranging and erecting23 machinery of transmission, obviously the first problem must be, what kind of machinery should be employed, and what are the conditions which should determine the selection and arrangement? What has been written has, so far as possible, been directed to suggesting proper means of solving these questions.

(1.) In what respect are air and water like belts and gearing, as means to transmit power?—(2.) What are some of the principal advantages gained by employing air to operate railway brakes?—(3.) Name some of the advantages of centralising motive power.—(4.) Are the conditions of working an engine the same whether air or steam is employed?

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1 machinery CAdxb     
n.(总称)机械,机器;机构
参考例句:
  • Has the machinery been put up ready for the broadcast?广播器材安装完毕了吗?
  • Machinery ought to be well maintained all the time.机器应该随时注意维护。
2 elasticity 8jlzp     
n.弹性,伸缩力
参考例句:
  • The skin eventually loses its elasticity.皮肤最终会失去弹性。
  • Every sort of spring has a definite elasticity.每一种弹簧都有一定的弹性。
3 analogous aLdyQ     
adj.相似的;类似的
参考例句:
  • The two situations are roughly analogous.两种情況大致相似。
  • The company is in a position closely analogous to that of its main rival.该公司与主要竞争对手的处境极为相似。
4 hydraulic AcDzt     
adj.水力的;水压的,液压的;水力学的
参考例句:
  • The boat has no fewer than five hydraulic pumps.这艘船配有不少于5个液压泵。
  • A group of apprentics were operating the hydraulic press.一群学徒正在开动水压机。
5 rigid jDPyf     
adj.严格的,死板的;刚硬的,僵硬的
参考例句:
  • She became as rigid as adamant.她变得如顽石般的固执。
  • The examination was so rigid that nearly all aspirants were ruled out.考试很严,几乎所有的考生都被淘汰了。
6 shafts 8a8cb796b94a20edda1c592a21399c6b     
n.轴( shaft的名词复数 );(箭、高尔夫球棒等的)杆;通风井;一阵(疼痛、害怕等)
参考例句:
  • He deliberately jerked the shafts to rock him a bit. 他故意的上下颠动车把,摇这个老猴子几下。 来自汉英文学 - 骆驼祥子
  • Shafts were sunk, with tunnels dug laterally. 竖井已经打下,并且挖有横向矿道。 来自辞典例句
7 apparatus ivTzx     
n.装置,器械;器具,设备
参考例句:
  • The school's audio apparatus includes films and records.学校的视听设备包括放映机和录音机。
  • They had a very refined apparatus.他们有一套非常精良的设备。
8 illustrating a99f5be8a18291b13baa6ba429f04101     
给…加插图( illustrate的现在分词 ); 说明; 表明; (用示例、图画等)说明
参考例句:
  • He upstaged the other speakers by illustrating his talk with slides. 他演讲中配上幻灯片,比其他演讲人更吸引听众。
  • Material illustrating detailed structure of graptolites has been etched from limestone by means of hydrofluoric acid. 表明笔石详细构造的物质是利用氢氟酸从石灰岩中侵蚀出来。
9 applied Tz2zXA     
adj.应用的;v.应用,适用
参考例句:
  • She plans to take a course in applied linguistics.她打算学习应用语言学课程。
  • This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。
10 velocity rLYzx     
n.速度,速率
参考例句:
  • Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
  • The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。
11 formerly ni3x9     
adv.从前,以前
参考例句:
  • We now enjoy these comforts of which formerly we had only heard.我们现在享受到了过去只是听说过的那些舒适条件。
  • This boat was formerly used on the rivers of China.这船从前航行在中国内河里。
12 attained 1f2c1bee274e81555decf78fe9b16b2f     
(通常经过努力)实现( attain的过去式和过去分词 ); 达到; 获得; 达到(某年龄、水平、状况)
参考例句:
  • She has attained the degree of Master of Arts. 她已获得文学硕士学位。
  • Lu Hsun attained a high position in the republic of letters. 鲁迅在文坛上获得崇高的地位。
13 impeded 7dc9974da5523140b369df3407a86996     
阻碍,妨碍,阻止( impede的过去式和过去分词 )
参考例句:
  • Work on the building was impeded by severe weather. 楼房的施工因天气恶劣而停了下来。
  • He was impeded in his work. 他的工作受阻。
14 friction JQMzr     
n.摩擦,摩擦力
参考例句:
  • When Joan returned to work,the friction between them increased.琼回来工作后,他们之间的摩擦加剧了。
  • Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体,并使其停止。
15 pistons c10621515a8dfd90d65ed99cc8c6e998     
活塞( piston的名词复数 )
参考例句:
  • Some pistons have seating rings of metal or leather. 有些活塞上有金属或皮革的密封环。
  • A pump uses valves and pistons. 泵使用阀和活塞。
16 inaccessible 49Nx8     
adj.达不到的,难接近的
参考例句:
  • This novel seems to me among the most inaccessible.这本书对我来说是最难懂的小说之一。
  • The top of Mount Everest is the most inaccessible place in the world.珠穆朗玛峰是世界上最难到达的地方。
17 motive GFzxz     
n.动机,目的;adv.发动的,运动的
参考例句:
  • The police could not find a motive for the murder.警察不能找到谋杀的动机。
  • He had some motive in telling this fable.他讲这寓言故事是有用意的。
18 insignificant k6Mx1     
adj.无关紧要的,可忽略的,无意义的
参考例句:
  • In winter the effect was found to be insignificant.在冬季,这种作用是不明显的。
  • This problem was insignificant compared to others she faced.这一问题与她面临的其他问题比较起来算不得什么。
19 condensation YYyyr     
n.压缩,浓缩;凝结的水珠
参考例句:
  • A cloud is a condensation of water vapour in the atmosphere.云是由大气中的水蒸气凝结成的。
  • He used his sleeve to wipe the condensation off the glass.他用袖子擦掉玻璃上凝结的水珠。
20 contraction sn6yO     
n.缩略词,缩写式,害病
参考例句:
  • The contraction of this muscle raises the lower arm.肌肉的收缩使前臂抬起。
  • The forces of expansion are balanced by forces of contraction.扩张力和收缩力相互平衡。
21 investigation MRKzq     
n.调查,调查研究
参考例句:
  • In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
  • He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。
22 queries 5da7eb4247add5dbd5776c9c0b38460a     
n.问题( query的名词复数 );疑问;询问;问号v.质疑,对…表示疑问( query的第三人称单数 );询问
参考例句:
  • Our assistants will be happy to answer your queries. 我们的助理很乐意回答诸位的问题。
  • Her queries were rhetorical,and best ignored. 她的质问只不过是说说而已,最好不予理睬。 来自《简明英汉词典》
23 erecting 57913eb4cb611f2f6ed8e369fcac137d     
v.使直立,竖起( erect的现在分词 );建立
参考例句:
  • Nations can restrict their foreign trade by erecting barriers to exports as well as imports. 象设置进口壁垒那样,各国可以通过设置出口壁垒来限制对外贸易。 来自辞典例句
  • Could you tell me the specific lift-slab procedure for erecting buildings? 能否告之用升板法安装楼房的具体程序? 来自互联网


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