Page 472 - Cam Design Handbook

THB14 9/19/03 7:58 PM Page 460

460 CAM DESIGN HANDBOOK

FIGURE 14.6. Involute cam (single lobe for stamp mill).

a stamp mill cam, has been employed for pulverizing crushed ore. The inherent action is
that the point of contact always occurs at the same place on the follower face. Thus, this
face may be made as small as possible within practical limits. Also, if we locate the point
of contact on the line of follower motion, the force components are ideal because the
moments tending to bend the follower stem are minimum. Other curves require large over-
hangs or moments that continuously change with cam rotation.

14.5 ECCENTRIC CIRCLE CAM—TRANSLATING
ROLLER FOLLOWER

Now let us use the eccentric circle cam with a translating roller follower. In Fig. 14.7a we
see an eccentric rotating about its center A, offset by a distance E. Figure 14.7b shows the
equivalent mechanism, the slider crank chain. The crank radius E is distance AB, and the
connecting rod length M is distance BC. Since these distances are constant, the equivalent
mechanism has constant proportions for the complete action of the eccentric circle cam.
Let us now derive the characteristics of this cam action. Let
y e = equivalent mechanism follower displacement measured from crank-end dead center
position, in
M = equivalent mechanism connecting rod length, in
R r = roller follower radius, in
t = angle between connecting rod and follower motion, deg

In this example, y = y e and q = e.
From Fig 14.7b we see the displacement of slider C