Английский язык. Теория механизмов и машин. Профессиональная составляющая языковой подготовки. Горбенко М.В - 96 стр.

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96
VI. CAMS AND CAM DESIGN
Classes of Cams.—
Cams may, in general, be divided into two classes:
uniform motion cams and accelerated motion cams. The uniform motion
cam moves the follower at the same rate of speed from the beginning to
the end of the stroke; but as the movement is started from zero to the
full speed of the uniform motion and stops in the same abrupt way, there
is a distinct shock at the beginning and end of the stroke, if the
movement is at all rapid. In machinery working at a high rate of speed,
therefore, it is important that cams are so constructed that sudden shocks
are avoided when starting the motion or when reversing the direction of
motion of the follower.
The uniformly accelerated motion cam is suitable for moderate
speeds, but it has the disadvantage of sudden changes in acceleration at
the beginning, middle and end of the stroke. A cycloidal motion curve
cam produces no abrupt changes in acceleration and is often used in
high-speed machinery because it results in low noise, vibration and
wear. The cycloidal motion displacement curve is so called because it
can be generated from a cycloid which is the locus of a point of a circle
rolling on a straight line
.
2
Cam Follower Systems.—The three most used cam and follower
systems are radial and offset translating roller follower, Figs. 1a and 1b;
and the swinging roller follower, Fig. 1c. When the cam rotates, it
imparts a translating motion to the roller followers in Figs. 1a and 1b and
a swinging motion to the roller follower in Fig. 1c. The motion of the
follower is, of course, dependent on the shape of the cam; and the
following section on displacement diagrams explains how a favorable
motion is obtained so that the cam can rotate at high speed without shock.
2
Jensen, P. W., Cam Design and Manufacture, Industrial Press Inc.
Fig. 1a. Radial Translating
Roller Follower
Fig. 1b. Offset Translating
Roller Follower
Fig. 1c. Swinging Roller
Follower

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