Four-bar linkage

A four-bar linkage, also called a four-bar, is the simplest movable closed-chain linkage. It consists of four bodies, called bars or links, connected in a loop by four joints. Generally, the joints are configured so the links move in parallel planes, and the assembly is called a planar four-bar linkage. Spherical and spatial four-bar linkages also exist and are used in practice.Universal joint.Tractor steeringBennett four-bar linkage.Crank-rocker stops at the limit positions and at min/max transmission angleFixed and moving centrodes of a four-barCoupler cognates of a crank-rocker four-barfour-bar type (Ackerman) steering linkageFour-bar function generatorTurning coupler four-bar linkagesParallel four-bar linkagesGalloway (deltoid or kite) four-bar linkageFolding crank-rocker four-bar linkage A four-bar linkage, also called a four-bar, is the simplest movable closed-chain linkage. It consists of four bodies, called bars or links, connected in a loop by four joints. Generally, the joints are configured so the links move in parallel planes, and the assembly is called a planar four-bar linkage. Spherical and spatial four-bar linkages also exist and are used in practice. Planar four-bar linkages are constructed from four links connected in a loop by four one-degree-of-freedom joints. A joint may be either a revolute, that is a hinged joint, denoted by R, or a prismatic, as sliding joint, denoted by P. A link connected to ground by a hinged joint is usually called a crank. A link connected to ground by a prismatic joint is called a slider. Sliders are sometimes considered to be cranks that have a hinged pivot at an extremely long distance away perpendicular to the travel of the slider. The link that connects two cranks is called a floating link or coupler. A coupler that connects a crank and a slider is often called a connecting rod.