The invention provides a caster including two wheels, a central frame member, and a mount member. The two wheels are mounted on the mount member. The caster has a hybrid bearing arrangement comprising both a rolling bearing and two slide bearings. The rolling bearing is located between the central frame member and the mount member and is configured to enable the caster to roll along a straight line with each of the two wheels rotating in a common direction about a first axis. Each of the two slide bearings is located between the mount member and a tread portion of a respective one of the two wheels. The slide bearings are configured to enable the two wheels to simultaneously rotate in opposite directions when the caster swivels about a second axis orthogonal to the first axis. In some embodiments, the caster is a hubless caster.

The invention provides a caster including two wheels, a central frame member, and a mount member. The two wheels are mounted on the mount member. The caster has a hybrid bearing arrangement comprising both a rolling bearing and two slide bearings. The rolling bearing is located between the central frame member and the mount member and is configured to enable the caster to roll along a straight line with each of the two wheels rotating in a common direction about a first axis. Each of the two slide bearings is located between the mount member and a tread portion of a respective one of the two wheels. The slide bearings are configured to enable the two wheels to simultaneously rotate in opposite directions when the caster swivels about a second axis orthogonal to the first axis. In some embodiments, the caster is a hubless caster.

Disclosed is a secondary clamping device for a wheel. Two bearings and a spacing ring are closed in a base by a bearing end cover, a shaft sleeve is mounted on the bearings, a linear bearing and a gland are fixed on the shaft sleeve, a positioning pin is fixed at the top of the floating shaft, two ends of the spring A are respectively connected with the positioning pin and the linear bearing, and the positioning pin can move up and down under the action of the spring A. A pull rod is fixed on the gland, the outer wall of the floating column is connected with the inner hole of the shaft sleeve, two ends of the spring B are respectively connected with the gland and the floating column.

Disclosed is a secondary clamping device for a wheel. Two bearings and a spacing ring are closed in a base by a bearing end cover, a shaft sleeve is mounted on the bearings, a linear bearing and a gland are fixed on the shaft sleeve, a positioning pin is fixed at the top of the floating shaft, two ends of the spring A are respectively connected with the positioning pin and the linear bearing, and the positioning pin can move up and down under the action of the spring A. A pull rod is fixed on the gland, the outer wall of the floating column is connected with the inner hole of the shaft sleeve, two ends of the spring B are respectively connected with the gland and the floating column.