Types of followers :
The followers may be classified as discussed below:
1. According to the surface in contact.
(a)Knife edge follower. When the contacting end of the follower has a sharp knife edge, it is called a knife edge follower.
(b) Roller follower. When the contacting end of the follower is a roller, it is called a roller follower.
i. Prime circle: It is the smallest circle that can be drawn from the centre of the cam and tangent to the pitch curve. For a knife edge and a flat face follower, the prime circle and the base circle are identical. For a roller follower, the prime circle is larger than the base circle by the radius of the roller.
ii. Pitch circle: It is a circle drawn from the centre of the cam through the pitch points.
Classification of cam:
1. Radial or disc cam: In radial cams, the follower reciprocates or oscillates in a direction perpendicular to the cam axis. The cams as shown in above Fig. are all radial cams.
2. Cylindrical cam: In cylindrical cams, the follower reciprocates or oscillates in a direction parallel to the cam axis. The follower rides in a groove at its cylindrical surface. A cylindrical grooved cam with a reciprocating and an oscillating follower is shown in Fig. below (a) and (b) respectively.
i) Trace point : It is a reference point on the follower and is used to generate the pitch curve. In case of knife edge follower, the knife edge represents the trace point and the pitch curve corresponds to the cam profile. In a roller follower, the centre of the roller represents the trace point.
The follower during its travel may have one of the following motions.
1. Uniform velocity,
2. Simple harmonic motion,
3. Uniform acceleration and retardation,
4. Cycloidal motion.
(i) Pressure angle: It is the angle between the direction of the follower motion and a normal to the pitch curve. This angle is very important in designing a cam profile. If the pressure angel is too large, a reciprocating follower will jam in its bearing.
(ii) Pitch point: It is point on pitch curve having the maximum pressure angle.
