HOME

TheInfoList



OR:

In
mechanical engineering Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, an ...
, a cam follower, also known as a track follower, is a specialized type of
roller Roller may refer to: Birds *Roller, a bird of the family Coraciidae * Roller (pigeon), a domesticated breed or variety of pigeon Devices * Roller (agricultural tool), a non-powered tool for flattening ground * Road roller, a vehicle for compa ...
or
needle bearing A needle roller bearing is a special type of roller bearing which uses long, thin cylindrical rollers resembling needles. Ordinary roller bearings' rollers are only slightly longer than their diameter, but needle bearings typically have rollers ...
designed to follow
cam Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
lobe profiles. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; ''stud'' style cam followers use a
stud Stud may refer to the following terms: Animals * Stud (animal), an animal retained for breeding ** Stud farm, a property where livestock are bred Arts and entertainment * Stud (band), a British progressive rock group * The Stud (bar), a gay b ...
while the ''yoke'' style has a hole through the middle.


Construction

The modern stud type follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Company. It replaced using a standard bearing and bolt. The new cam followers were easier to use because the stud was already included and they could also handle higher loads. While roller cam followers are similar to roller bearings, there are quite a few differences. Standard ball and roller bearings are designed to be pressed into a rigid housing, which provides circumferential support. This keeps the outer race from deforming, so the race cross-section is relatively thin. In the case of cam followers the outer race is loaded at a single point, so the outer race needs a thicker cross-section to reduce
deformation Deformation can refer to: * Deformation (engineering), changes in an object's shape or form due to the application of a force or forces. ** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies. * Defo ...
. However, in order to facilitate this the roller diameter must be decreased, which also decreases the dynamic bearing capacity. ''End plates'' are used to contain the needles or bearing axially. On stud style followers one of the end plates is integrated into the inner race/stud; the other is pressed onto the stud up to a shoulder on the inner race. The inner race is induction hardened so that the stud remains soft if modifications need to be made. On yoke style followers the end plates are peened or pressed onto the inner race or liquid metal injected onto the inner race. The inner race is either induction hardened or through hardened. Another difference is that a
lubrication Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubrica ...
hole is provided to relubricate the follower periodically. A hole is provided at both ends of the stud for lubrication. They also usually have a
black oxide Black oxide or blackening is a conversion coating for ferrous materials, stainless steel, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance, for appearance, and to minimize ligh ...
finish to help reduce corrosion.


Types

There are many different types of cam followers available.


Anti-friction element

The most common anti- friction element employed is a ''full complement'' of needle rollers. This design can withstand high radial loads but no thrust loads. A similar design is the ''caged needle roller'' design, which also uses needle rollers, but uses a
cage A cage is an enclosure often made of mesh, bars, or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal or person in captivity, capturing an animal or person, and displayin ...
to keep them separated. This design allows for higher speeds but decreases the load capacity. The cage also increases internal space so it can hold more lubrication, which increases the time between relubrications. Depending on the exact design sometimes two rollers are put in each pocket of the cage, using a cage design originated by RBC Bearings in 1971. For heavy-duty applications a ''roller'' design can be used. This employs two rows of rollers of larger diameter than used in needle roller cam followers to increase the dynamic load capacity and provide some thrust capabilities. This design can support higher speeds than the full complement design. For light-duty applications a ''bushing'' type follower can be used. Instead of using a type of a roller a plastic
bushing Bushing may refer to: *Bushing (bearing), a type of plain bearing * Bushing (electrical), an insulated device that allows a conductor to pass through a grounded conducting barrier *Bushing (isolator), a mechanical device used to reduce vibrationa ...
is used to reduce friction, which provides a maintenance free follower. The disadvantage is that it can only support light loads, slow speeds, no thrust loads, and the temperature limit is . A bushing type stud follower can only support approximately 25% of the load of a roller type stud follower, while the heavy and yoke followers can handle 50%. Also all-metallic heavy-duty bushing type followers exist.


Shape

The outer diameter (OD) of the cam follower (stud or yoke) can be the standard cylindrical shape or be crowned. Crowned cam followers are used to keep the load evenly distributed if it deflects or if there is any misalignment between the follower and the followed surface. They are also used in
turntable A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...
type applications to reduce skidding. Crowned followers can compensate for up to 0.5° of misalignment, while a cylindrical OD can only tolerate 0.06°. The only disadvantage is that they cannot bear as much load because of higher stresses.


Stud

Stud style cam followers usually have a ''standard'' sized stud, but a ''heavy'' stud is available for increased
static load capacity Static may refer to: Places *Static Nunatak, a nunatak in Antarctica United States *Static, Kentucky and Tennessee *Static Peak, a mountain in Wyoming ** Static Peak Divide, a mountain pass near the peak Science and technology Physics *Static el ...
.


Drives

The standard driving system for a stud type cam follower is a slot, for use with a flat head screwdriver. However, hex sockets are available for higher torquing ability, which is especially useful for eccentric cam followers and those used in
blind hole A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of en ...
s. Hex socket cam followers from most manufacturers eliminate the relubrication capability on that end of the cam follower. RBC Bearings' Hexlube cam followers feature a relubrication fitting at the bottom of the hex socket.


Eccentricity

Stud type cam followers are available with an
eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...
stud. The stud has a bushing pushed onto it that has an eccentric outer diameter. This allows for adjustability during installation to eliminate any
backlash Backlash may refer to: Literature * '' Backlash: The Undeclared War Against American Women'', a 1991 book by Susan Faludi * ''Backlash'' (Star Wars novel), a 2010 novel by Aaron Allston * Backlash (Marc Slayton), comic book character * ''Backla ...
. The adjustable range for an eccentric bearing is twice that of the eccentricity.


Yoke

YOKE type cam followers are usually used in applications where minimal deflection is required, as they can be supported on both sides. They can support the same static load as a heavy stud follower.


Track followers

All cam followers can be track followers, but not all track followers are cam followers. Some track followers have specially shaped outer diameters (OD) to follow tracks. For example, track followers are available with a V-groove for following a V-track, or the OD can have a flange to follow the lip of the track. Specialized track followers are also designed to withstand thrust loads so the anti-friction elements are usually
bearing ball Bearing balls are special highly spherical and smooth balls, most commonly used in ball bearings, but also used as components in things like freewheel mechanisms. The balls come in many different ''grades''. These grades are defined by bodies ...
s or of a
tapered roller bearing Tapered roller bearings are rolling element bearings that can support axial forces (i.e., they are good thrust bearings) as well as radial forces. Description The inner and outer ring raceways are segments of cones and the rollers are taper ...
construction.


See also

*
Tappet A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly. An earlier use of the term was for part of the valve gear ...
* Reciprocating motion


References

{{Automotive engine , collapsed Bearings (mechanical) Mechanical engineering