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Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill...

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Gears and Cams Chapter 17
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Page 1: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

Gears and Cams

Chapter 17

Page 2: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

2Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Objectives

• Define the characteristics of a spur gear, worm gear, and bevel gear

• Calculate the gear ratio and rpm of two mating gears, given the pitch diameters

• Define the principal spur gear terms• Draw a spur gear

Page 3: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

3Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Objectives (cont.)

• Describe the relationship between a cam profile and a displacement diagram

• Draw a cam profile, given a displacement profile drawing

• List the types of cam followers

Page 4: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

4Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Understanding Gears

• Gears are used to transmit power and rotating or reciprocating motion from one machine part to another

• ANSI/AGMA publishes detailed standards for gear design and drawings

Page 5: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

5Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Spur Gears

• Proportions and shapes of gear teeth are well standardized

• The most common geometric form used in gears today is the involute profile• Involute means “rolled inward”

Page 6: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

6Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Page 7: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

7Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Constructing a Base Circle

Page 8: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

8Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

The Involute Tooth Shape

Page 9: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

9Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Spacing Gear Teeth

• Teeth are spaced around the periphery by laying out equal angles

• The number of spaces should be twice the number of teeth, equal to the tooth thickness at the pitch circle

Page 10: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

10Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Spacing Gear Teeth

Page 11: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

11Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Rack Teeth

• Gear teeth formed on a flat surface are called a rack

Page 12: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

12Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Working Drawings of Spur Gears• Since teeth are cut to a standard

shape, individual teeth are not typically shown

Page 13: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

13Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Spur Gear Design

• Spur gear design normally begins with selecting pitch diameter

• The size of the teeth (diametral pitch) depends on:• Gear speeds• Gear materials• Horsepower to be transmitted• Tooth form

Page 14: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

14Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Worm Gears

• Worm gears are used to transmit power between nonintersecting shafts that are at right angles to each other

• A worm is a screw with a thread shaped like a rack tooth

• Worm wheels are similar to helical gears cut to conform to the shape of the worm

Page 15: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

15Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Worm Gears

Page 16: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

16Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Working Drawings of Worm Gears• In assembly drawings, gear teeth

are omitted and the gear blank represented conventionally

• On detail drawings, the worm and gear are usually drawn separately

Page 17: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

17Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Bevel Gears

• Bevel gears transmit power between shafts whose axes intersect at any angle

• Bevel gear teeth have the same involute shape as teeth on spur gears but are tapered toward the cone apex

Page 18: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

18Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Bevel Gears

Page 19: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

19Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Bevel Gear Terminology

Page 20: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

20Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Working Drawings of Bevel Gears• Working drawings for bevel gears

give only the dimensions of the gear blank

• Data necessary for cutting teeth are given in a note or table

Page 21: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

21Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Cams

• Cams can be used to produce irregular motions• A shaft rotating at uniform speed

carries the cam• A reciprocating member, called the

follower, presses a roller against the curved surface of the cam

• Rotating the cam causes the follower to reciprocate a cyclic motion according to the cam profile

Page 22: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

22Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Cams

Page 23: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

23Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Displacement Diagrams

• A displacement diagram is a curve showing the displacement of the follower as ordinates on a base line that represents one revolution of the cam

• The motion of the follower as it rises or falls depends on the shape of the curves in the displacement diagram

Page 24: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

24Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Displacement Diagrams

Page 25: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

25Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Cam Profiles

Page 26: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

26Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Cylindrical Cams

• When the follower movement is in a plane parallel to the cam shaft, a cylindrical cam must be employed

Page 27: Gears and Cams Chapter 17. 2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper.

27Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Cylindrical Cams


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