Swivel casters are well known in which a yoke and a plate are held together by a kingpin so that the yoke and plate are coaxially disposed journalled to each other with a raceway of ball bearings therebetween for rotation about a swivel axis and with the kingpin coaxial with the swivel axis. The kingpin may be a rivet or threaded fastener or the like. Typically, a top washer and a bottom washer may be included to house the bearing. The yoke carries a wheel journalled thereto.
Such kingpin casters suffer the disadvantage that they are prone to failure by failure of the kingpin such that the yoke and plate become able to move axially apart and a sloppiness develops which increases wear. Failure of the kingpin can lead to catastrophic failure with complete separation of the yoke from the plate.
Kingpin casters also suffer the disadvantage that they comprise at least the kingpin, the yoke, the plate and ball bearings and that their manufacture involves handling and assembling of these components.
Kingpin casters suffer the disadvantage that the kingpin typically focuses axially directed forces necessary to hold the yoke and plate axially together radially closer to the swivel axis than the raceway holding the bearings and, thus, is at a disadvantage to resist moment-inducing loading forces tending to act on a wheel carried off center by the swivel axis as is typical in a caster.
Casters which do not have a kingpin are known in which the yoke and plate are made by machining and/or casting processes and in which ball bearings are inserted into a raceway through special access openings machined in the yoke and/or plate. Such kingpin-free caster assemblies have yokes and plates which are expensive to manufacture and to assemble.
USPTO Backgrounds
USPTO Backgrounds