Patent ID: 7308730

Claim:
A base member for swivel caster comprising: a fixed base including a ring member with a protrusion on a center thereof, a plurality of hemispherical first raceways being lathed in an inward surface of the ring member; a rotation base pivoting a wheel and engaging with the fixed base, a connecting portion being formed on the rotation base, a plurality of hemispherical second raceways being lathed in an outward surface of the connecting portion, a support cavity being defined through a center of the rotation base, assembling holes being defined in the connecting portion and communicating with the support cavity and the second raceways; and a hollow staff being made of elastic material, an outward peripheral of the staff fining for the support cavity, a guiding portion being formed on a forward edge of the staff; wherein the connecting portion of the rotation base telescopically engage to the ring member of the fixed base, the second raceways of the rotation base and the first raceways of the fixed base communicate with each other and together make up of ball raceways, and during assembly, a plurality of rolling balls are extended through the assembling holes and loaded into the ball raceways, then a plurality of biasing balls are loaded in the assembling holes, and the staff is inserted into the support cavity and blocks the assembling holes, therefore the swivel caster is assembled in a way that the rotation base is rotatable and swivelable and guides the rolling balls freely.