上充通大学 Shanghai Jiao Tong University Advantages of Different Transmissions3 Advantages of Gear Drives 1.Gear drives are more compact than chain or belt drives because center distances are minimum. 2.Gears have greater speed capabilities than either belts or chains. 3.Gears have a greater range of speed ratios than chains. 4.Gears can better transfer high power at high speed than either belts or chains can. 5.Metal gears do not deteriorate with age,heat or oil and grease and they do not develop static electric charges. 11
11 Advantages of Different Transmissions3 Advantages of Gear Drives 1. Gear drives are more compact than chain or belt drives because center distances are minimum. 2. Gears have greater speed capabilities than either belts or chains. 3. Gears have a greater range of speed ratios than chains. 4. Gears can better transfer high power at high speed than either belts or chains can. 5. Metal gears do not deteriorate with age, heat or oil and grease and they do not develop static electric charges
上游充互大学 Shanghai Jiao Tong University Flexible Transmission Elements2 lectric otor V-belt drive Gear reducer Chain drive Driven machine (a)Sketch of combination drive (b)Photograph of an actual drive installation.Note that guards have been removed from the belt and chain drives to show detail
12 Flexible Transmission Elements2
上游充互大学 Shanghai Jiao Tong University Objectives of this Lecture Describe the basic features of a belt drive system Describe several types of belt drives Specify suitable types and sizes of belts and sheaves to transmit a given level of power at specified speeds for the input and output sheaves Specify the primary installation variables for belt drives,including center distance and belt length 13
13 Objectives of this Lecture Describe the basic features of a belt drive system Describe several types of belt drives Specify suitable types and sizes of belts and sheaves to transmit a given level of power at specified speeds for the input and output sheaves Specify the primary installation variables for belt drives, including center distance and belt length
上泽充通大学 Shanghai Jiao Tong University Types of Belts2.4 Table 4-1 Belt Type Figure Joint Flat Yes 整 Round Yes V None Timing None 14
14 Types of Belts2,4 Table 4-1
上游充互大学 Shanghai Jiao Tong University 切边平带 Types of Belts2.4 .Flat or Round Belt Table 4-2 >Simplest type >Often made from leather or rubber-coated fabric. >Crowned pulleys are used for flat belts,and grooved sheaves for round belts. >Driving force is limited by pure friction between belt and sheave. >Some designers prefer flat belts for delicate machinery 包布平静 Because belt will slip if torque tends to rise to a level high enough to damage the machine
15 Types of Belts2,4 •Flat or Round Belt Simplest type Often made from leather or rubber-coated fabric. Crowned pulleys are used for flat belts, and grooved sheaves for round belts. Driving force is limited by pure friction between belt and sheave. Some designers prefer flat belts for delicate machinery ⁼ Because belt will slip if torque tends to rise to a level high enough to damage the machine. Table 4-2