A cam follower, also called a trail follower, [1] is a professional kind of roller or needle bearing made to follow cams. Cam followers come in a huge selection of different configurations, however the most defining attribute is the way the cam follower mounts to its mating part; stud style cam supporters use a stud as the yoke style has a opening through the center. [2]
The first cam follower was invented and trademarked in 1937 by Thomas L. Robinson of the McGill Manufacturing Company. [3] It replaced using simply a standard bearing and bolt. The brand new cam followers were simpler to use because the stud had been included plus they could also handle higher tons. [
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CAM AND MECHANISMS
A cam mechanism consists of three elements: the cam, the follower (or follower system), and the framework. The follower is in direct contact with the cam. The cam may be of varied designs. The follower system includes all the elements to which motion is imparted by the cam. This can be connected right to the follower, or linked through linkages and gearing. The framework of the device facilitates the bearing surfaces for the cam as well as for the follower.
A CAM changes the input movement, which is usually rotary movement (a rotating action), to a reciprocating movement of the follower. They are found in many machines and toys
WHAT MAY BE THE CONCEPT BEHIND CAM?
A CAM is a rotating machine element gives reciprocating or oscillating movement to another aspect known as follower. The cam and follower has a spot or lines contact constitute a higher set or you can say that it is the mechanicl component of a machine that can be used to transmit the action to the another component of the device called the follower, by way of a recommended program by direct contact. The contact between them is preserved by an external force which is generally provided by the planting season or sometimes by the weight of the follower itself, when it's sufficient. Cam is the driver member and the follower is the motivated member. The follower is at direct connection with the cam.
CAM MECHANISM CONTAIN THREE MECHANISMS
CAM:It might be of several shapes
FOLLOWER: It offers all the elements to which movement is imparted by the cam. This may be connected directly by the cam. This can be connected directly to the follower, or linked through linkages and gearing.
FRAME: The body of the machine facilitates the bearing surfaces for the cam as well as for the follower.
APPLICATIONS OF CAM AND FOLLOWERS
Cam and follower are trusted for operating inlet and exhaust valve of I C engine motor.
These are used in wall structure clock.
These are being used in feed system of automatic lathe Machine.
These are used in paper cutting machine.
Used in weaving textile machineries.
The cam mechanism is a functional one. It can be designed to produce almost infinite types of motioning the follower.
It is utilized to transform a rotary motion into a translating or oscillating motion.
On certain occasions, additionally it is used to convert one translating or oscillating motion into a different translating or oscillating action.
Cams are used in a wide variety of computerized machines and equipment.
The certain usuages of cam and fans that includes textile machineries, pcs, producing presses, food processing machines, internal combustion motors, and countless other automated machines, control systems and devices. The cam system is indeed a very important aspect in modern mechanization.
CLASSIFICATION OF CAMS
Based on the physical shape
Disk or dish cams
Working of the disc cam with reciprocating follower.
Working of the disk cam with oscillating follower.
Cylindrical cam
Translating cam
CLASSIFICATION OF FOLLOWES
(i) Predicated on surface in contact
(a) Knife advantage follower
(b) Roller follower
(c) Flat encountered follower
(d) Spherical follower
(ii) Predicated on type of motion
Oscillating followe
Translating follower
(iii) Based on type of action
Radial (in line) follower
(b) Off-set follower
Cams can be easily classified into two main groups
Group a:
Cams that impart action to the follower in a planes based on the axis of rotation of the cam (as does a cylindrical cam).
Group b:
Cams that impart movement to the follower in a planes at 90 degrees to the axis of rotation, as with face or edge cams. Most cams get into this category.
TYPES OF CAMS
Eccentric cam:
A round cam is categorised as an eccentric cam because
the axis of rotation of the cam is offset from the
geometric center of the circular disc.
Concentric disc:
A concentric disc mounted on a rotating shaft would
have its axis of rotation coinciding with its geometric
center.
PROFILE Forms OF SOME CAMS:
PEAR-SHAPED CAMS:
These type cams are often used for handling valves. For instance, they are being used on motor car camshafts to operate the engine motor valves. A
follower controlled by way of a pear-shaped cam remains motionless for about half a trend of the cam. At that time that the follower is
stationary, the cam is in a dwell period. Through the other half revolution of the cam, the follower rises and then comes. As the pearshaped cam is symmetrical, the go up motion is equivalent to the fall motion.
Edge cams
It must be loved that this type of cam, where the follower is in touch with the advantage of the cam disk, is only with the capacity of imparting positive action to its follower in one path, that is, through the rise portion of the cam activity. During the semester portion of the cam movement the follower must be taken care of in contact with the cam either by the mass of the follower and its
mechanism or, more usually, with a spring and coil. Both methods have their advantages.
Box cams
A groove can be milled when confronted with cam discs. As the cam rotates, a follower located in the groove has its action led by the groove. This type of cam is called a field cam.
Cylindrical cams:
Cylindrical cams are used when motion has to be transmitted parallel to the axis of rotation of the cam. The cylindrical or barrel cam consists of a revolving cylinder with a helical (screw molded) groove in its curvedsurface. A follower with a tapered roller end is found in the groove. As the cylinder turns, the follower steps in a direct range parallel to the axis of the rotation barrel cam.
This type of cam is often used to guide thread on sewing machines, looms and cloth making machines.
CIRCULAR CAMS:
These cams are sometimes called eccentric cams. The cam account is a circle. The guts of rotation of the cam is often from the geometric centre of the group. The circular cam produces a simple form of motion called a simple harmonic motion. These cams can be used to produce motion in pumps. Round cams can be used to operate steam engine unit valves. As the cam is symmetrical, the surge and fall movements will be the same.
HEART SHAPED CAMS:
This cam triggers the follower to go with a homogeneous velocity. Heart-shaped cams are essential when the follower movement must be homogeneous or constant as, for example, in the system that winds thread consistently on the bobbin of your sewing machine. A heart-shaped cam can be utilized for winding line evenly on the past of any solenoid.
UNIFORM ACCELERATION AND RETARDATION CAMS:
A cam molded as shown manages the action of the follower such that it moves with consistent acceleration and retardation. The follower benefits and looses speed at a continuous rate. Standard acceleration and retardation cams are used to controls the motion of linkages in sophisticated machinery.
Types of Cam Followers
There are three types of cam enthusiasts, and since the kind of follower affects the account of the cam it is useful considering the benefits and drawbacks of each type. The three types will be the knife-edge, the roller follower and the flatfoot or mushroom follower.
The Knife Border Follower:
This is the easiest type, is seldom used due to the fast rate of wear. When it is adopted, it is almost always for reciprocating action, operating in slides and there is considerable side thrust, this being truly a component of the thrust from the cam.
The Roller Follower:
This eliminates the problem of quick wear because the sliding effect is basically replaced by a roller action. Some sliding will still take place due to the varying peripheral acceleration of the cam account, because of the changing radius of the point of contact. Please note also that the radial position of the contact between your cam and the roller, in accordance with the follower centre, will change corresponding to whether a
rise or fall motion is taken place: this truth should be considered when making the cam account. Again, with the roller follower, sizeable side thrusts can be found, a drawback when working with reciprocating movements. This part thrust will be increased when working with small rollers.
The Flat Feet or Mushroom Follower:
This has the advantage that the sole part thrust present is the fact that because of the friction between your follower and the cam. The issue of wear is not so great as with the knife-edge follower, because the point of contact between the cam and follower will move over the face of the follower in line with the change of shape of the cam. A strategy to lessen further the result of wear is to design the
follower to manage to axial rotation and organize the axis of the follower to lay to one area of the cam. Thus the connection with the cam will tend to cause rotation of the follower. The cam profile, to work with a flatfoot follower, must be convex at all parts, in order to avoid the corners of the follower digging in to the cam profile. The minimum cam radius should be as small as possible to reduce sliding velocity and friction.
All three types of cam enthusiasts can be mounted
in the following ways:
1) In-line with the cam centre line,
2) Offset from the cam middle line, or
3) Attached to a swinging radial arm.
CAM-VALVE
CAM TERMINOLOGY
Trace point:
A theoretical point on the follower,
corresponding to the point of an fictitious knife-edge follower.
It is utilized to create the pitch curve.
In the situation of a roller follower, the trace
point reaches the guts of the roller.
2. Pitch curve:
The path made by the track point at the follower is
rotated in regards to a fixed cam.
3. Working curve:
The work surface of the cam in contact with the follower. For
the knife-edge follower of the plate cam, the pitch curve and the working curves
coincide. Inside a close or grooved cam there is an inner profile and an outer
working curve.
4. Pitch group:
A group from the cam center through the pitch point. The
pitch circle radius is used to compute a cam of minimum size for a given
pressure angle.
5. Prime circle (reference circle):
The smallest group from the cam center
through the pitch curve.
6. Base group:
The smallest circle from the cam centre through the cam profile
curve.
7. Stroke or put:
The most significant distance or angle through which the follower
moves or rotates.
8. Follower displacement:
The position of the follower from a specific zero
or slumber position (usually its the positioning when the follower associates with the
base circle of the cam) with regards to time or the rotary position of the cam.
9. Pressure angle:
The viewpoint at any point between your normal to the pitch
curve and the instantaneous route of the follower motion. This viewpoint is
important in cam design since it symbolizes the steepness of the cam
profile.
Some question occurs regarding cam and enthusiasts:
When is a set confronted follower preferred as compared to roller enthusiasts and
why?
Flat faced enthusiasts are preferred to roller fans where space is limited
for eg: cams with smooth followers are being used to use valves of a car engine however in case of stationary and oil motors, roller supporters are preferred because more space can be found.
What data is plotted on displacement diagram of cam and follower motion?
Ans:Story of linear displacement i. e. lift up or heart stroke (s) of follower (on Y axis
direction) versus angular displacement (ё) of the cam for one rotation (on X
axis direction)
