Hybrid bearing arrangement caster technology
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.
1. A hubless caster with a hybrid bearing arrangement, including:
two wheels, each of the two wheels having a tread portion and a mount portion, the mount portion of each wheel defines a respective slide bearing surface;
a central frame member defining a swivel axis;
a rolling bearing;
a tubular mount member, consisting of a single ring shaped body surrounding an open central corridor defining a rolling axis;
wherein each of the two wheels mounted on the tubular mount member, the tubular mount member being in contact with both of the slide bearing surfaces, such that the two slide bearing surfaces are configured to slide on the tubular mount member when the two wheels rotate relative to the tubular mount member, which enables the two wheels to simultaneously rotate in opposite directions when the hubless caster swivels about the swivel axis; and
wherein the rolling bearing is mounted on the tubular mount member between the two wheels, the rolling bearing directly contacts the tubular mount member and the central frame member, such that the rolling bearing is configured to enable the hubless caster to roll along a straight line with each of the two wheels rotating in a common direction about the rolling axis.
2. The hubless caster of claim 1 wherein the rolling bearing is located at a position axially offset from the two slide bearings, such that there is open space between the rolling bearing and each of the two slide bearings.
3. The hubless caster of claim 1 wherein the rolling bearing is located at a midpoint between the two wheels in an axial direction.
4. The hubless caster of claim 1 wherein the rolling bearing comprises a plurality of ball bearings and the hubless caster is devoid of other ball bearings.
5. The hubless caster of claim 1 wherein the central frame member has a radially interior face having a channel formed therein, the rolling bearing being received in the channel.
6. The hubless caster of claim 1 , wherein the rolling and swivel axes are orthogonal to each other.
7. The hubless caster of claim 1 wherein the open central corridor is open entirely through the hubless caster such that when looking at the hubless caster from a side one can see entirely through the hubless caster by looking through the open central corridor.
8. The hubless caster of claim 1 wherein the two slide bearings respectively are located directly radially inward of the tread portions of the two wheels.
9. The hubless caster of claim 1 wherein the two slide bearings respectively comprise two bearing surfaces configured to slide respectively on two bearing surface areas of the tubular mount member, such that the two bearing surfaces face radially inward while the two bearing surface areas face radially outward.
10. The hubless caster of claim 1 wherein the rolling bearing comprises two metal walls, one rotatable relative to the other, that collectively house a plurality of ball bearings or cylinder bearings.
11. The hubless caster of claim 1 wherein the rolling bearing has a thickness, measured in a radial direction, of less than 0.275 inch.