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A spherical bearing is a bearing that permits rotation about a central point in two orthogonal directions (usually within a specified angular limit based on the bearing geometry). Typically these bearings support a rotating shaft in the bore of the inner ring that must move not only rotationally, but also at an angle. It can either be a
Spherical bearing 101
With single and double rows of rollers. Bearings (mechanical) {{tech-stub
A spherical bearing is a bearing that permits rotation about a central point in two orthogonal directions (usually within a specified angular limit based on the bearing geometry). Typically these bearings support a rotating shaft in the bore of the inner ring that must move not only rotationally, but also at an angle. It can either be a plain bearing
file:NYC 100-driving-axle-friction-bearing.jpg, Plain bearing on a 1906 S-Motor locomotive showing the axle, bearing, oil supply and oiling pad
file:Linear-table with detail numbered.png, A sliding table with four cylindrical bearings
file:GWR Spo ...
or roller bearing
In mechanical engineering, a rolling-element bearing, also known as a rolling bearing,ISO 15 is a bearing which carries a load by placing rolling elements (such as balls, cylinders, or cones) between two concentric, grooved rings called race ...
.
Self-aligning spherical bearings were first used by James Nasmyth
James Hall Nasmyth (sometimes spelled Naesmyth, Nasmith, or Nesmyth) (19 August 1808 – 7 May 1890) was a Scottish engineer, philosopher, artist and inventor famous for his development of the steam hammer. He was the co-founder of Nasmyth, ...
around 1840 to support line shaft
A line shaft is a power-driven rotating shaft for power transmission that was used extensively from the Industrial Revolution until the early 20th century. Prior to the widespread use of electric motors small enough to be connected directly to ...
bearings in mills and machine shops. For long shafts it was impossible to accurately align bearings, even if the shaft was perfectly straight. Nasmyth used brass bearing shells between hemispherical brass cups to allow the bearings to self-align.
Construction
Spherical bearings can be of ahydrostatic
Hydrostatics is the branch of fluid mechanics that studies fluids at hydrostatic equilibrium and "the pressure in a fluid or exerted by a fluid on an immersed body". The word "hydrostatics" is sometimes used to refer specifically to water and o ...
or mechanical construction. A spherical bearing by itself consists of an outer ring and an inner ring and a locking feature that makes the inner ring captive within the outer ring in the axial direction only. The outer surface of the inner ring and the inner surface of the outer ring are spherical and are collectively considered the raceway and they slide against each other, either with a lubricant, a maintenance-free (typically polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a corporate spin-of ...
or PTFE) based liner, or they incorporate a rolling element such as a race of ball-bearings, allowing lower friction.
Applications
Spherical bearings are used incar suspension
Suspension is the system of tires, tire air, spring (device), springs, shock absorbers and Linkage (mechanical), linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support b ...
s, engines, driveshafts, heavy machinery, sewing machines, robotics and many other applications: wherever rotational motion must be allowed to change the alignment of its rotation axis. An example, although this is rarely used in practice, is the drive axle bearings of a vehicle control arm
In automotive suspension, a control arm, also known as an A-arm, is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. In simple terms, it governs a wheel's vertical travel, allowing it to mo ...
(or A-arm) suspension. The mechanics of the suspension allow the axle to move up and down (and the wheel to turn in order to steer the vehicle), and the axle bearings must allow the rotational axis of the axle to change without binding. This is a simple concept that illustrates a possible application of a spherical bearing. In fact, spherical bearings are used in smaller sub-components of this type of suspension, for example certain types of constant-velocity joint
A constant-velocity joint (also called a CV joint and homokinetic joint) is a mechanical coupling which allows the shafts to rotate freely (without an appreciable increase in friction or Backlash (engineering), backlash) and compensates for the a ...
s.
See also
* * * * * – one of the earliest patented applications of this technology *References
External links
Spherical bearing 101
With single and double rows of rollers. Bearings (mechanical) {{tech-stub