A cam follower is a type of bearing typically used to replicate a specific motion. In a cam and follower system, the cam is a mechanical element often in the form of a flat piece of metal tooled into an oblong shape that rotates or slides. The follower travels along the surface of the cam, tracking the shape by its edge and translating that shape into a movement pattern. The cam follower operates on a very simple principle and can be applied to a wide number of tasks, because although it is basic, it is also highly versatile. Cam follower systems are used in a wide variety of devices, including motor vehicles, moving lawn ornaments, and pumping devices.
Cam and follower system forms
These systems usually take the form of a rotating rod that turns the cam or cams, and followers mounted close by. Where, exactly, the cam follower is mounted and which type of follower is used depends of the purpose of the system, and there are many different configurations available. The follower must be kept in smooth and even contact with the cam, by gravity, a spring, a groove, or other stabilizing method, or it will not be able to translate the movement effectively. Without a stabilizing force on the follower system, the follower may have a tendency to wobble or jitter, potentially causing a malfunction in the device being moved by the cam follower and wearing the follower down more quickly.
Follower and cam designs
Cam followers also have different head designs. A follower with a pointed head will more accurately hold and replicate the motion of the cam, but it is also more likely to wear down more quickly and require replacement. Followers with broader heads will not wear down as easily, but some accuracy will typically be sacrificed. In other applications, the head may have a roller, rather than being flat or pointed, to allow for smoother movement.
There are a number of different types of cam followers, each of which can support different amounts of force and speed applied by the cam. One of the most common types is the needle roller, which contains long, sometimes pointed bearings; these anti-friction elements inside the cam follower allow it to move smoothly and support heavier loads. Another type, the caged roller, is similar, but the needles are separated by a cage; this allows for more lubrication and operation a higher speed, but it cannot support as high a load.
One of the main differences between followers is how they are attached to the device. Stud-style followers include a standard or heavy-duty threaded rod built in, and can typically be mounted quickly and easily. The built-in stud may be convenient, but its strength is limited by how much load that stud can support. A yolk-style follower has a hole in the middle; it is less convenient to mount, but a higher strength pin can be used.
Most cams are made in simple shapes designed to create basic motions — the more complex the shape of the cam, the harder the follower must work to translate it. Many cam follower systems take the shape of a teardrop or have a single jagged inset to create a specific motion. The follower systems used on motor vehicles to control the pistons, for example, usually have a teardrop shape that causes a sharp upward motion, or displacement, as the follower reaches the apex of the teardrop, causing the attached piston to fire.
Uses
Although cam and follower systems are used in a wide variety of mechanical applications, they may be most familiar to many people for their role in cars and other motor vehicles. There are multiple cam follower systems in motor vehicles, one for each cylinder, and they are offset so that all the pistons do not fire at once. The multiple systems can all be mounted on one camshaft, making the most use of the energy used to turn the shaft, rather than dedicating energy to each piston individually. In this case, damage to one cam follower could cause a misfire in the engine.