Page 475 - Cam Design Handbook

THB14 9/19/03 7:58 PM Page 463

SPECIAL CAM MECHANISMS 463

E . 0500
. deg.
t = tan -1 = tan -1 =17 1
m
M . 1 625
14.6 ECCENTRIC CIRCLE CAM—TRANSLATING
FLAT-FACED FOLLOWER

The eccentric is a type of cam. It is a circular member having its center of rotation offset
from its geometric center. The follower may be flat-faced or roller type. A translating flat-
faced follower will be discussed. The eccentric represents the simplest cam mechanism
possible. Its zero pressure angle eliminates the problem of the follower jamming.
In Fig. 14.8a we see an eccentric rotating about point A with its geometric center at a
distance E. In Fig. 14.8b we see the equivalent mechanism which is the Scotch yoke mech-
anism in which the follower movement is a simple harmonic function. Let
y = follower displacement, in
y e = equivalent mechanism follower displacement, in
q = cam angle of rotation for displacement y, rad
e = crank angle of rotation (equivalent mechanism) for displacement y e = rad
E = distance from cam center to circular-arc center of curvature, in
h = 2E = maximum displacement of follower, in
w = cam and equivalent mechanism angular velocity, rad/sec
In this example, y = y e and q = e. From Fig. 14.8b we see that the follower
displacement

(a) Cam and follower. (b) Equivalent mechanism.
FIGURE 14.8. Eccentric circle cam—translating flat-faced follower.