A spherical plain bearing is a

bearing Bearing(s) may refer to: * Bearing (angle), a term for direction * Bearing (mechanical), a component that separates moving parts and takes a load * Bridge bearing, a component separating a bridge pier and deck * Bearing BTS Station in Bangkok * ' ...

that permits angular 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. 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 align the bearings to self-align.

Construction

Spherical bearings can be of a

hydrostatic Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...

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 that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Che ...

or PTFE) based liner, or they incorporate a rolling element such as a race of ball-bearings, allowing lower friction.

Application

Spherical bearings are used in countless applications, wherever rotational motion must be allowed to change the alignment of its rotation axis. A good example 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 mov ...

(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. While in practice, spherical bearings are rarely used here, it 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 Constant-velocity joints (also known as homokinetic or CV joints) are mechanical joints which allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. Th ...

s. Spherical bearings are used in

car 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.

References

External links

Spherical bearing 101
With single and double rows of rollers. Bearings (mechanical) {{tech-stub

Construction

Application

See also

References

External links