機(jī)械專業(yè)英語董建國第7章

1、Unit 7 Unit 7 TEXT READING MATERIAL Unit 7 TEXT Ball Bearings Ball bearings are used in almost every kind of machine and device with rotting parts. However, such bearings cannot be used indiscriminately without a careful study of the loads and operating conditions. In addition, the bearing must be p

2、rovided with adequate mounting, lubrication, and sealing. Unit 7 A ball bearing usually consists of four parts: an inner ring, an outer ring, the balls, and the cage or separator. To increase the contact area and permit larger loads to be carried, the balls run in curvilinear grooves in the rings. T

3、he radius of the groove is slightly larger than the radius of the ball and a very slight amount of radial play must be provided. The bearing is thus permitted to adjust itself to small amounts of angular misalignment in the assembled shaft and mounting. The separator keeps the balls evenly spaced an

4、d prevents them from touching each other on the sides where their relative velocities are the greatest. Unit 7 Ball bearings are made in a wide variety of types and sizes. The radial bearing is able to carry a considerable amount of axial thrust. However, when the load is directed entirely along the

5、 axis, the thrust type of bearing should be used. The angular contact bearing will take care of both radial and axial loads. The self-aligning ball bearing will take care of large amounts of angular misalignment. An increase in radial capacity may be secured by using rings with deep grooves, or by e

6、mploying a double-row radial bearing. Unit 7 Fig. 7-1 Elements of typical ball bearing Unit 7 Fig. 7-2 Cross section of ball and outer race Unit 7 LEARN TO SPEAK Mr. Zhang: Good morning, Mr. Cheng. Mr. Cheng: Good morning, Mr. Zhang. Mr. Zhang: What are you doing? Mr. Cheng: I am cleaning this ball

7、bearing. Mr. Zhang: What are the essential parts of the ball bearing? Mr. Cheng: The essential parts of the ball bearing are the inner and outer ring, the balls and the separator. Mr. Zhang: Is the bearing standardized? Mr. Cheng: Yes. It is. Unit 7 Mr. Zhang: How to assemble it ? Mr. Cheng: The ass

8、embly of this consists of four stages. Mr. Zhang: Which are the four stages? Mr. Cheng: The first, the inner ring is displaced within the outer, leaving a crescent shape space. The second, put the balls into the space. The third, moved the inner ring back to be concentric the outer, and spaced equal

9、ly around the bearing. The end, installed a separator to maintain spacing of the balls. Unit 7 Mr. Zhang: Is deep-groove ball bearing the most widely used type of radial bearing? Mr. Cheng: Yes. It is. Mr. Zhang: And why? Mr. Cheng: Because although deep-groove ball bearings are designed to carry a

10、radial load, they perform well under a combined radial and thrust load. Mr. Zhang: You are very kind of you. Mr. Cheng: Dont mention it. Unit 7 NEW WORDS AND EXPRESSIONS indiscriminately IndI5skrImIneItlI adv. 隨意地 careful 5keEfJl adj. 小心的，仔細(xì)的 carefully adv. 仔細(xì)地 seal si:l n.&v. 封，密封 sealing si:lIN n.

11、 密封 inner 5InE(r) adj. 內(nèi)部的，在內(nèi)的 ring rIN n. 環(huán)，圈 outer 5aJtE(r) adj. 外部的外面的 Unit 7 cage keIdV n. 籠，籠盒，隔離罩 separator 5sepEreItE(r) n. 隔離罩，隔板，分離器 area 5ZEriE n. 范圍, 面積 curvilinear kE:vI5lInIE(r) adj. 曲線的 groove gru:v n. 溝，槽 v. 開槽 radius 5reIdIEs n. 半徑 itself It5self pron. 它本身，它自己 misalignment misE5laInm

12、Ent n. 不對(duì)準(zhǔn)，偏差 evenly 5i:vEnlI adv. 均勻地，平坦地 able eIbl adj. 有能力的，能干的 Unit 7 axial 5AksIEl adj. 軸的，軸向的 axially adv. 軸向地，與軸平行地 thrust WrQst n. 推力, 牽引力 entire In5taIE(r) adj. 全體的，完全的 entirely adv. 完全地，徹底地 care keE(r) n.，v. 管理，照顧 align E5laIn v. 對(duì)準(zhǔn)，排成直線，排列 self self n. 自己，自行 row rEJ n. 排, 列 Unit 7 angular

13、 misalignment 角位移，角偏差 able to +動(dòng)詞原形 能，會(huì) axial thrust 軸向推力 thrust type of bearing 推力軸承 take care of 照看，留心，處理 self-aligning ball bearing 自位滾珠軸承 double-row radial bearing 雙列徑向軸承 Unit 7 NOTES 1. To increase the contact area and permit larger loads to be carried, the balls run in curvilinear grooves in t

14、he rings. 為了增加接觸面以承受較大的載荷，滾珠在內(nèi)外環(huán)的曲線槽 內(nèi)滾動(dòng)。 動(dòng)詞“permit”后面可用“to v”作補(bǔ)語，即“permit+名詞 +to v”意為“允許(做什么)”。本句中，作賓語的名詞是 “l(fā)oads”，補(bǔ)語“to be carried”是“to v”的被動(dòng)形式，因?yàn)閮烧?之間是被動(dòng)的關(guān)系。 Unit 7 2The bearing is thus permitted to adjust itself to small amounts of angular misalignment in the assembled shaft and mounting. 這樣，軸承可

15、以自動(dòng)調(diào)整以適應(yīng)所裝配的軸和軸承座內(nèi)微量 的角度偏差。 “to adjustto”是“調(diào)節(jié)以適應(yīng)”的含義。 3The separator keeps the balls evenly spaced and prevents them from touching each other on the sides where their relative velocities are the greatest. Unit 7 保持架使?jié)L珠均勻地隔開并防止在其相對(duì)速度最大處相互 接觸。 動(dòng)詞“keep”后面可接“名詞(賓語)+v-ed2(補(bǔ)語)”。如本 句中： keep the ball evenly

16、 spaced 使?jié)L珠均勻地離開 4The angular contact bearing will take care of both radial and axial loads. 向心推力球軸承既照顧到徑向載荷，也照顧到軸向載荷。 “take care of”翻譯為“照看，留心，處理”。本處可引 伸譯作“照顧到”。 Unit 7 5An increase in radial capacity may be secured by using rings with deep grooves, or by employing a double-row radial bearing. 使用深槽環(huán)

17、或雙列徑向軸承則可提高軸承的徑向承載能 力。 介詞“in”在名詞“increase, change”等后面表示 “在方面”。翻譯時(shí)“in”可不譯，而“in”后的名詞， 可譯作“增加”或“變化”等詞的賓語或主語。例如： Unit 7 An increase in accuracy may be secured by grinding. 磨削可以確保提高精度 Tool hardness is affected by the change in its temperature. 刀具的硬度受其溫度變化的影響。 Unit 7 EXERCISES 1Discuss the following quest

18、ions in English: (1) Where are the ball bearings used? (2) How many kinds of ball bearings are there? What are they? (3) How to assemble a ball bearing? 2Use English for replacing Chinese or use Chinese for replacing English: (1) 保持架 (2) 曲線滾道 (3) 角度偏差 Unit 7 (4) Sealing of a ball bearing (5) Assembl

19、e a shaft (6) Relative velocities of ball and groove 3Place a“T”after sentences that are true and an“F”after those that are false. (1) A bearing is a connecter that permits the connected members to either rotate or translate relative to one another but prevents them from separating in the direction

20、in which loads are applied.( ) Unit 7 (2) Bearings support stationary parts, such as shafts and spindles, of a machine and mechanism.( ) (3) The most effective way of increasing bearing load capacity is to increase the ball complement.( ) (4) In deep-groove ball bearings, the races are approximately

21、 four times as deep as the ball diameter.( ) (5) The relative motion in bearings is always opposed by friction, and the work done in overcoming friction is lost power in all machines.( ) Unit 7 (6) in a few applications where operating conditions are mild, the rings and separator can be omitted and

22、loose balls interposed between the shaft and housing.( ) 4Fill the blanks with the words and expressions given below： races, grooves, deep, shallow, radial, spherical, decreasing, increasing, inner, outer, holes. (1) The most effective way of_ bearing load capacity is to increase the ball complement

23、. (2) The_ ring is displaced within the_ ring, leaving a crescent-shapes space. Unit 7 (3) The races in which the balls roll have_ with radii of curvature slightly greater than the radius of a ball. (4) Roll bearings have rollers instead of balls between the_. (5) Ball bearings are categorized into

24、three areas, namely, _ball bearings, angular- contact ball bearings, and thrust ball bearings. (6) The most widely used radial ball bearing is the_ groove bearing. Unit 7 READING MATERIAL Cams Cams are the most versatile mechanisms available. A rotary cam is a part on a machine which mechanically ch

25、anges cylindrical motion to reciprocating motion. Since the cam outline can be given a wide variety of shapes, many different types of motion can be secured. The purpose of a cam is to transmit various kinds of motion to other parts of a machine. Unit 7 Practically every cam must be designed and man

26、ufactured to fit specially requirements. Though each cam appears to be quite different from the other, all the cams work in a similar way. In each case, as the cam is rotated or turned, another part in contact with the cam called follower, is moved either left and right, up and down, or in and out .

27、The follower is usually connected to other parts on the machine to accomplish the desired action. The direction the follower moves depends upon the position of the framework which attaches the cam and follower to the machine. If the follower loses contact with the cam, it will fail to work. Some of the common applications of cams are: Unit 7 (1) Camshaft and distributor shaft of automotive engine. (2)