Cams - Cams 6.1 Introduction 6.1.1 A Simple Experiment:...

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Unformatted text preview: Cams 6.1 Introduction 6.1.1 A Simple Experiment: What is a Cam? Figure 6-1 Simple Cam experiment Take a pencil and a book to do an experiment as shown above. Make the book an inclined plane and use the pencil as a slider (use your hand as a guide). When you move the book smoothly upward, what happens to the pencil? It will be pushed up along the guide. By this method, you have transformed one motion into another motion by a very simple device. This is the basic idea of a cam. By rotating the cams in the figure below, the bars will have either translational or oscillatory motion. 6.1.2 Cam Mechanisms The transformation of one of the simple motions, such as rotation, into any other motions is often conveniently accomplished by means of a cam mechanism. A cam mechanism usually consists of two moving elements, the cam and the follower, mounted on a fixed frame. Cam devices are versatile, and almost any arbitrarily-specified motion can be obtained. In some instances, they offer the simplest and most compact way to transform motions. A cam may be defined as a machine element having a curved outline or a curved groove, which, by its oscillation or rotation motion, gives a predetermined specified motion to another element called the follower . The cam has a very important function in the operation of many classes of machines, especially those of the automatic type, such as printing presses, shoe machinery, textile machinery, gear-cutting machines, and screw machines. In any class of machinery in which automatic control and accurate timing are paramount, the cam is an indispensable part of mechanism. The possible applications of cams are unlimited, and their shapes occur in great variety. Some of the most common forms will be considered in this chapter. 6.2 Classification of Cam Mechanisms We can classify cam mechanisms by the modes of input/output motion, the configuration and arrangement of the follower, and the shape of the cam. We can also classify cams by the different types of motion events of the follower and by means of a great variety of the motion characteristics of the cam profile. (Chen 82) Figure 6-2 Classification of cam mechanisms 4.2.1 Modes of Input/Output Motion 1. Rotating cam-translating follower. ( Figure 6-2a,b,c,d,e ) 2. Rotating follower ( Figure 6-2f ): The follower arm swings or oscillates in a circular arc with respect to the follower pivot. 3. Translating cam-translating follower ( Figure 6-3 ). 4. Stationary cam-rotating follower: The follower system revolves with respect to the center line of the vertical shaft. Figure 6-3 Translating cam - translating follower 6.2.1 Follower Configuration 1. Knife-edge follower ( Figure 6-2a ) 2. Roller follower ( Figure 6-2b,e,f ) 3. Flat-faced follower ( Figure 6-2c ) 4. Oblique flat-faced follower 5. Spherical-faced follower ( Figure 6-2d ) 6.2.2 Follower Arrangement 1. In-line follower: The center line of the follower passes through the center line of the camshaft....
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This note was uploaded on 02/06/2012 for the course MEEG 439 taught by Professor Scf during the Spring '11 term at The Petroleum Institute.

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Cams - Cams 6.1 Introduction 6.1.1 A Simple Experiment:...

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