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1、Graphical Synthesis of Cam Mechanisms5-3 Plate Cam with Translating Roller(or Knife-edge) Follower5.4 Plate Cam with Oscillating Roller Follower（摆动滚子从动件圆盘凸轮）5.5 Plate Cam with Translating Flat-faced Follower (直动平底从动件圆盘凸轮）其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge5-3 Plate Cam with T
2、ranslating Roller(or Knife-edge) FollowerGraphical methods offer clear physical concepts and can help us to understand the analytical methods其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge1. A plate cam with translating offset knife-edge follower(偏心尖底直偏心尖底直动从从动件件圆盘凸凸轮） is to be designed
3、to accomplish(完成) a motion as follows:h=80mm, o =140, o=100, S =40, S= 80, e=40mm;rise with 3-4-5 polynomial(多项式) motion curve; return with sine acceleration motion curve;The cam rotates counter-clockwise;The minimum radius rP of the cam is 100mm.其它语言学习第10次课53 Plate Cam with Translating Rolleror Kni
4、feedgeAt first: calculate the displacement S of the follower for different values of the cam angle according to the given motion curve. For the return, For the rise, 其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeIf the cam rotates an angle B0OB= counter-clockwise from the beginning, the
5、 follower will rise through a corresponding distance BB=S from the lowest position along its guide way.Suppose that the cam mechanism has been designed according the given motion curve S-.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeCam Rotating Follower Rotating 其它语言学习第10次课53 Plate Ca
6、m with Translating Rolleror KnifeedgeTherefore, motion curve S- can be understood such ways: The cam is stationary. The frame and the follower rotate in the direction opposite to . The follower will rise through a corres-ponding S along the guide-way relative to the frame.This is the principle of in
7、version(反转法).其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeDuring inversion, the extension of the follower guide-way always stays tangent to a circle with radius equal to the offset e and centred at the centre O of the camshaft. This circle is called the offset circle(偏置偏置圆).其它语言学习第10次课
8、53 Plate Cam with Translating Rolleror KnifeedgeDuring inversion, the locus traced by the knife-edge is the cam contour, which is also called the pitch curve(理论廓线).其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe minimum circle centred at O and tangent to the pitch circle is called the
9、 base circle of the cam pitch curve, or prime circle(基圆). 其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe procedure(步骤) to design the pitch curve:其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeNote: (1) The pitch curve can not be drawn in the direction of .(2) The point B
10、can not be located by laying off BB=S along OB.(3) The centre line of the follower is always tangent to the offset circle.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeIf offset e=0, the offset translating follower becomes an in-line translating follower.What will happen if e=0?其它语言学习第1
11、0次课53 Plate Cam with Translating Rolleror KnifeedgeCharacteristics:The roller is always tangent to the cam contour(实际廓线) at all times.2. Graphical Synthesis of Plate Cam with Translating Roller Follower （直动滚子从动件圆盘凸轮）（直动滚子从动件圆盘凸轮）其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe locus of
12、 the roller centre relative to the cam is called the pitch curve(理论廓线）理论廓线） of the cam. The roller is tangent to the cam contour(实际廓线) at all times, and the cam contour is the envelope(包络线）of the family of the roller circles.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe pitch curve
13、(理论廓线) and the cam contour (实际廓线) are parallel(法向等距). The minimum radius of the pitch curve is called the radius rP of the prime circle. Note: the minimum radius of the cam contour is not rP.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeFor the knife-edge follower, the pitch curve and t
14、he cam contour are the same.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeSuppose：A virtual(虚拟的) translating knife-edge follower is welded(焊) to the translating roller follower The knife-edge coincides(重合) with the roller centre. The locus of the knife-edge, or the locus of the roller c
15、entre, or pitch curve, relative to the cam can be designed.其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe process to design the cam contour is:其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge5.4 Plate Cam with Oscillating Roller Follower（摆动滚子从动件圆盘凸轮）（摆动滚子从动件圆盘凸轮）In this me
16、chanism, The angular lift(角行程) of the follower is max. The motion equations can also apply to the oscillating follower so long as S is replaced by and h by max其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe cam contour is obta
17、ined by drawing a smooth curve tangent to the family of all roller circles. 其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeSince the follower arm must have some physical dimensions, the side edge of the straight arm of the follower may interfere(干涉) with the cam contour. It is necessary
18、to check that this will not occur at all positions. To avoid interference, the arm may be designed as a bent(弯曲) rod.其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge5.5 Plate Cam with Translating Flat-faced Follower (直动平底从动件圆盘凸轮）This follower is used often in high-speed cam mechanisms. Th
19、e motion curve of the follower will be restricted since all sections of the cam contour must be convex（凸起）. 其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeInline?Offset？Redundant constraint其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge其它语言学习第10次课53 Plate Cam with Translating
20、 Rolleror KnifeedgeThe cam contour may be drawn as a smooth curve tangent to the family of the position lines of the flat face. 其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeGraphical Synthesis of Cam Mechanisms5-3 Plate Cam with Translating Roller(or Knife-edge) Follower5.4 Plate Cam w
21、ith Oscillating Roller Follower（摆动滚子从动件圆盘凸轮）5.5 Plate Cam with Translating Flat-faced Follower (直动平底从动件圆盘凸轮）其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge(1) Analytical Synthesis of the Pitch CurveLead to a substantial(显著的) saving of time in the design process. 5.6 A Few Questions Shoul
22、d Be Discussed(2) Pressure Angle(3) The minimum radius of the prime circle (最小基圆半径)其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgePressure Angle其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgePressure angle changes during motion so it is necessary to control the value of the m
23、aximum pressure angle max.其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedgepressure angle Return in Return in form-closed force-closed cam mech. cam mech. or rise Translating fol. 2535 7080 Oscillating fol. 3545其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeThe minimum radius o
24、f the prime circle (最小基圆最小基圆半径半径)其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeWhen rP is so small that max is equal to in the rise or in the return, the corresponding rP is called the minimum radius of the prime circle, denoted as (rP)min其它语言学习第10次课53 Plate Cam with Translating Rollero
25、r KnifeedgeReview of Chapter 5Characteristics of Cam MechanismsClassifications of Cam Mechanisms 1. By the cam shape 2. By the motion type of the follower 3. By the shape of the follower end 4. By the manner of keeping the cam and the follower in contact其它语言学习第10次课53 Plate Cam with Translating Rolle
26、ror KnifeedgeReview of Chapter 5Basic Concepts of Cam MechanismsConcept of Follower Motion Curves (从动件从动件运动规律运动规律 )Concept of quasi-velocityConcept of quasi-Acceleration其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeReview of Chapter 5Follower Motion Curves1. Constant Velocity Motion Cur
27、ve2. Constant Acceleration and Deceleration Motion Curve(等加速等减速运动规律)3. 3-4-5 Polynomial (多项式) Motion Curve4. Cosine Acceleration Motion Curve (or Simple Harmonic (谐波) Motion Curve)5.Sine Acceleration Motion Curve (or Cycloid(摆线) Motion Curve)6. Combined Motion Curves其它语言学习第10次课53 Plate Cam with Tran
28、slating Rolleror KnifeedgeReview of Chapter 5Graphical Synthesis of Cam Mechanisms1.A plate cam with translating offset knife-edge follower(偏心尖底直偏心尖底直动从从动件件圆盘凸凸轮）2.Plate Cam with Translating Roller Follower （直动（直动滚子从动件圆盘凸轮）滚子从动件圆盘凸轮）3.Plate Cam with Translating Flat-faced Follower (直直动平底从动件圆盘凸轮）动平底从
29、动件圆盘凸轮）4.Plate Cam with Oscillating Roller Follower（摆动滚（摆动滚子从动件圆盘凸轮）子从动件圆盘凸轮）其它语言学习第10次课53 Plate Cam with Translating Rolleror KnifeedgeHomework1.Please redo the example in slider 3.2.Please analyze the characteristics of each motion curves of cam mechanisms.其它语言学习第10次课53 Plate Cam with Translating Rolleror Knifeedge
