Machinery's Handbook, 31st Edition
CAMS AND CAM DESIGN
2371
B
C
34 36:0
2
6 ′′
6 ′
32
4
h
6
30
6 ′′′
A
D E 36
R min
8
0 2 4
6 8 10
12 14 16 18 20 22 24 26 28 30
28
20 °
180 °
60 °
100 °
360 ° (a)
10
26
R max
12
24
(b)
22
14
20
16
18
Fig. 10. (a) Time-Displacement Diagram for Cam to be Laid Out; (b) Construction of Contour of Cam with Radial Translating Roller Follower
Offset Translating Roller Follower: Given the time-displacement diagram Fig. 11(a) and an offset follower. The construction of the cam in this case is very similar to the fore going case and is shown in Fig. 11(b). In this construction it will be noted that the angular position lines are not drawn radially from the cam shaft center but tangent to a circle having a radius equal to the amount of offset of the center line of the cam follower from the center of the cam shaft. For counterclockwise rotation of the cam, points 6 ′ , 6 ″ , and 6 ′″ are located in succession as indicated.
36 : 0
34
B
C
32
2
6 ”
6 ”
30
4
h
28
6
A
D E
6 ””
0
2 4
6 8 10
12 14 16 18 20 22 24 26 28 30
36
100°
20°
180°
60°
26
8
(a) 360°
24
10
(b)
22
12
20
14
18 16
Fig. 11. (a) Time-Displacement Diagram for Cam to be Laid Out; (b) Construction of Contour of Cam with Offset Translating Roller Follower
Swinging Roller Follower: Given the time-displacement diagram Fig. 12(a) and the length of the swinging follower arm L f , it is required that the displacement of the follower center along the circular arc that it describes be equal to the corresponding displacements in the time-displacement diagram. If φ 0 is known, the displacement h of Fig. 12(a) would be found from the formula h = πφ 0 L f /180 ° ; otherwise the maximum rise h of the follower is stepped off on the arc drawn with M as a center and starting at a point on the R min circle. Point M is the actual position of the pivot center of the swinging follower with respect to the cam shaft center. It is again required that the rotation of the cam be counterclockwise and therefore M is considered to have been rotated clockwise around the cam shaft center, whereby the points 2, 4, 6, etc., are obtained as shown in Fig. 12(b). Around each of the pivot points, 2, 4, 6, etc., circular arcs whose radii equal L f are drawn between the R min
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