《机械专业英语》课件第8章.ppt

1、Unit 8TEXT LEARN TO SPEAK NEW WORDS AND EXPRESSIONS NOTES EXERCISES READING MATERIAL PROFESSIONAL WORDS AND PHRASES TEXTBall 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

2、the loads and operating conditions.In addition,the bearing must be provided with adequate mounting,lubrication,and sealing.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,

3、the balls run in curvilinear grooves in the rings.The 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 mounti

4、ng.The separator keeps the balls evenly spaced and prevents them from touching each other on the sides where their relative velocities are the greatest.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 t

5、he load is directed entirely along the 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 usin

6、g rings with deep grooves,or by employing a double-row radial bearing.Fig.8-1 Elements of typical ball bearing Fig.8-2 Cross section of ball and outer race srdLEARN TO SPEAKMr.Zhang:Good morning,Mr.Cheng.Mr.Cheng:Good morning,Mr.Zhang.Mr.Zhang:What are you doing?Mr.Cheng:I am cleaning this ball bear

7、ing.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.Mr.Zhang:How to assemble it?Mr.Cheng:The assembly of this consists of four s

8、tages.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 equally around the bearing.The end,installed a sep

9、arator to maintain spacing of the balls.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 radial load,they perform well under a combined radial and thrust lo

10、ad.Mr.Zhang:Thanks very much.Mr.Cheng:Not at all.NEW WORDS AND EXPRESSIONSindiscriminately IndI5skrImIneItlI adv.随意地careful 5keEfJl adj.小心的，仔细的carefully adv.仔细地seal si:l n.&v.封，密封sealing si:lIN n.密封inner 5InE(r)adj.内部的，在内的ring rIN n.环，圈outer 5aJtE(r)adj.外部的外面的cage keIdV n.笼，笼盒，隔离罩separator 5sepEreIt

11、E(r)n.隔离罩，隔板，分离器area 5ZEriE n.范围,面积 curvilinear kE:vI5lInIE(r)adj.曲线的groove gru:v n.沟，槽v.开槽radius 5reIdIEs n.半径itself It5self pron.它本身，它自己misalignment misE5laInmEnt n.不对准，偏差evenly 5i:vEnlI adv.均匀地，平坦地able 5eIbl adj.有能力的，能干的axial 5AksIEl adj.轴的，轴向的axially adv.轴向地，与轴平行地thrust WrQst n.推力,牵引力entire In5t

12、aIE(r)adj.全体的，完全的entirely adv.完全地，彻底地care keE(r)n.&v.管理，照顾align E5laIn v.对准，排成直线，排列self self n.自己，自行row rEJ n.排,列 angular misalignment 角位移，角偏差able to+动词原形 能，会axial thrust 轴向推力thrust type of bearing 推力轴承take care of 照看，留心，处理self-aligning ball bearing 自位滚珠轴承double-row radial bearing 双列径向轴承NOTES1.To in

13、crease the contact area and permit larger loads to be carried,the balls run in curvilinear grooves in the rings.为了增加接触面以承受较大的载荷，滚珠在内外环的曲线槽内滚动。动词“permit”后面可用“to v.”作补语，即“permit+名词+to v.”意为“允许(做什么)”。本句中，作宾语的名词是“loads”，补语“to be carried”是“to v”的被动形式，因为两者之间是被动的关系。2The bearing is thus permitted to adjust

14、itself to small amounts of angular misalignment in the assembled shaft and mounting.这样，轴承可以自动调整以适应所装配的轴和轴承座内微量的角度偏差。“to adjustto”是“调节以适应”的含义。3The separator keeps the balls evenly spaced and prevents them from touching each other on the sides where their relative velocities are the greatest.隔离罩使滚珠均匀地

15、隔开并防止在其相对速度最大处相互接触。动词“keep”后面可接“名词(宾语)+v-ed2(补语)”。如本句中：keep the ball evenly spaced使滚珠均匀地离开4The angular contact bearing will take care of both radial and axial loads.向心推力球轴承既照顾到径向载荷，也照顾到轴向载荷。“take care of”翻译为“照看，留心，处理”。本处可引申译作“照顾到”。5An increase in radial capacity may be secured by using rings with de

16、ep grooves,or by employing a double-row radial bearing.使用深槽环或双列径向轴承则可提高轴承的径向承载能力。介词“in”在名词“increase,change”等后面表示“在方面”。翻译时“in”可不译，而“in”后的名词可译作“增加”或“变化”等词的宾语或主语。例如：An increase in accuracy may be secured by grinding.磨削可以确保提高精度。Tool hardness is affected by the change in its temperature.刀具的硬度受其温度变化的影响。EX

17、ERCISES 1Discuss the following questions 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)曲线滚道(3)角度偏差(4)Sealing of a ball bearin

18、g(5)Assemble 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 dir

19、ection in which loads are applied.()(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 four times

20、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.()(6)In a few applications where operating conditions are mild,the rings and separator can be omitted and loose balls interposed betw

21、een 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.(2)The_ ring is displaced within the_ rin

22、g,leaving a crescent-shapes space.(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 three areas,namely,_ball bearings,angular-contact ball bea

23、rings,and thrust ball bearings.(6)The most widely used radial ball bearing is the_ groove bearing.READING MATERIALCamsCams are the most versatile mechanisms available.A rotary cam is a part on a machine which mechanically changes cylindrical motion to reciprocating motion.Since the cam outline can b

24、e 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.Practically every cam must be designed and manufactured to fit specially requirements.Though each cam appears to be quite different f

25、rom 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.The follower is usually connected to other parts on the machine to accomplish the desired action

26、.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:(1)Camshaft and distributor shaft of automotive engine.(2)Produc

27、tion machine tools.(3)Automatic of record player.(4)Printing machines.(5)Automatic washing machines.(6)Automatic dishwashers.(7)Calculating machines,including computers.Fig.8-3 Types of cams(a)Disk cam；(b)Translation cam；(c)Cylindrical cam；(d)Face cam PROFESSIONAL WORDS AND PHRASESversatile 5v:sEtaI

28、l adj.多用途的，多方面的outline 5Eutlain n.外形，轮廓secure sI5kjuE v.保证，获得 adj.可靠的，安全的manufacture mAnju5fAktFE v.大规模制造，生产fit fIt v.&n.装配，配合follower 5fBlEuE n.从动件，随动件framework 5freimwE:k n.构架，框架attach E5tAtF vt.附上，加上automatic C:tE5mAtIk adj.自动的，机械的dishwasher 5dIFwBFE(r)n.洗碗机，洗碗的人calculate 5kAlkjuleit vt.计算 in contact with 与接触attach to 附在上lose contact with 与脱离接触