You must have heard this Cam and follower mechanism is in Internal combustion engines. A Cam is a rotating machine element which gives reciprocating or oscillatory motions to another element known as the follower.
Cam and Follower
The Cam and the follower have a line contact and constitute a higher pair.
Higher pair: When the motion between the two elements is partly turning and partly sliding, then the pair is known as a higher pair.
The cam is usually located on shafts and rotates at the uniform speed, whereas the follower motion will be based on the shape of the Cam.
As you already know that these Cam and the follower mechanisms were used for operating the inlet and the outlet valve of the internal combustion engines. These were the simplest and the most important mechanisms inventions in modern machinery today.
These Cams and followers were classified into different categories. Let us discuss them in detail.
Classification of Followers
According to the Surface in Contact
- Knife Edge Follower
- Roller Follower
- Flat Faced or mushroom follower
- Spherical Faced Follower
According to the motion of the follower
- Reciprocating or Transmitting Follower
- Oscillating or Rotating follower
According to the path of motion of the follower
- Radial Follower
- Off-set follower
Let us discuss these in more detail with schematic diagrams.
Knife Edge Follower
Knife Edge follower will have a sharp knife-edge as the contacting edge on to the Cam as shown in the below figure. Due to the very small contacting area for the follower on the cam, there will be excessive wear.
In this knife-edge follower, there will be a considerable amount of side thrust exists in between the follower and the guide.
When the contacting end of the follower is a roller, it is called as the roller follower. The schematic diagram of a roller follower is shown in the below figure.
Between the roller and the follower, there will be a rolling contact, so the wear will be greatly reduced. In roller follower also there will be side thrust exists between the follower and the guide.
Flat Faced or mushroom follower
When the contacting surface of the follower is perfectly flat, then the type of follower is called the flat-faced follower. The schematic representation of the Flat-faced follower is shown in the below figure.
In this flat-faced follower, the side thrust will be still there, but it is very less comparatively. This side thrust can also further reduced by offsetting the follower axis with the cam rotating centre axis as shown in the below figure.
Radial Follower and the Offset Follower
When the motion of the follower is along an axis which is passing through the centre of the Cam, then these types of followers comes under the Radial Followers. The above-mentioned Knife edge follower, roller Follower and flat-faced followers are the radial follower.
Whereas the offset follower is having an offset distance between the axis(Motion Axis) of follower and the centre of the Cam which is already mentioned in the flat-faced follower to reduce the side thrust.
These two radial follower and the offset follower are the classifications according to the path of motion of the follower.
Spherical Faced Follower
When the contacting surface of the follower is of spherical shape, then the follower is called the spherical follower. The schematic representation of the spherical follower is shown below.
In the case of flat-faced followers, when they have used in automobile engines, high surface stresses are produced. in order to minimise the stresses, the flat-faced followers will be machined to spherical shape.
Now let us the classification of these above followers according to the motion of the follower.
Reciprocating or Translating Follower
As we have discussed different follower in the above section which is having the translatory motion towards upward/downward direction, those all come under the Reciprocating or translating follower. Example, shown below.
When the motion of the cam is converted into the predetermined oscillatory motion for the follower, such followers come under the oscillating follower.
Classification of Cams
There were many classifications of Cams but the most important types are
- Radial Cam or Disc Cam
- Cylindrical Cam
Radial Cam or Disc Cam
In radial Cams, either the follower reciprocates or oscillates in a direction perpendicular to the cam axis. All the cam and follower mechanisms that we have discussed in the above section comes under the Radial or Disc cams. One example for the Radial Cam is again shown below
These radial cams or Disc cams are widely used than the Cylindrical cams.
In cylindrical cam, the follower will be reciprocated or oscillates in a direction parallel to the cam axis. The follower rides in the groove at its cylindrical surface. Check the schematic representation of the Cylindrical cam with both the reciprocating follower and the oscillating follower below.
These are the different types of Cams & followers. If you have further thoughts on this topic, please let us know in the comment section below.