Mobile loaders are essential equipment for the loading and unloading of containerized and palletized cargo into and from the holds of aircraft. Such loaders often employ two platforms. One platform, usually referred to as the bridge, provides an interface with the sill of the cargo door. The bridge is supported on a hydraulic lift, which provides a high degree of control and stability and allows the height of the bridge to be adjusted to correspond to the height of the aircraft cargo door. Once the bridge is positioned, it typically remains in a substantially constant position with respect to the aircraft, although it is known to make slight adjustments to the height of the bridge to compensate for shifts in the height of the aircraft cargo door as the plane is loaded or unloaded. Although the balance of the following discussion is presented in terms of a loading process in which cargo is placed onto an aircraft, it will be understood all concepts apply equally to unloading processes.
The second platform, hereinafter referred to as the platform, cycles up and down during the loading process, delivering cargo to the bridge. The platform is typically raised and lowered by means of hydraulic systems acting through mechanical linkages that ensure that the platform maintains a substantially horizontal attitude. For example, a pair of chains powered by hydraulic cylinders may cooperate with a platform squaring or stabilizing scissors to ensure that the platform moves vertically during raising and lowering. Cargo loaders of this type are known in the art.
The decks of the platform and bridge sections of cargo loaders are typically provided with an array of some type of friction-reducing device, so that containers and pallets can be easily slidably moved across the deck. In addition, the decks are provided with one or more powered devices for applying a motive force to the cargo. The powered devices may be wheels, rollers, belts or the like. Because of the nature of the loading process, which may entail lateral, longitudinal and rotational movement, the friction reducing devices on the surface rotate in whichever direction is required to achieve the desired movement, or at least not impede the desired movement. Thus, suitable friction reducing devices may be casters, rollers, wheels, or some combination thereof, and may be actuable in and out of engagement with the underside(s) of the cargo. One type of friction reducing device that is known for such omni-directional applications is a roller wheel, which essentially comprises a wheel hub having an axis and a plurality of peripheral rollers, with the peripheral rollers rotating about individual axes that are normal to the axis of the hub. A roller wheel may be mounted on a shaft which is rotated selectively in either rotational direction. In addition, roller wheels are known in which peripheral rollers are mounted on the hub in two rows, with the peripheral rollers in one row being staggered from the peripheral rollers in another row. Staggering the rollers relative to each other provides for constant contact of at least one peripheral roller of one of the wheels with a load-bearing surface at all times. Examples of roller wheels can be found in U.S. Pat. Nos. Des. 309,254, 318,791, U.S. Pat. Nos. 1,305,535 and 3,465,843. A complex roller assembly is disclosed in U.S. Pat. No. 4,223,753.
A significant problem with conventional roller wheels, and particularly dual hub roller wheels, is that the monolithic wheel hub is provided with a central bore for receiving the axle, which rotates with the wheel hub about the hub axis. This means that any installation, removal, repair or replacement of a roller wheel requires access to one end of the axle and requires that removal of the roller wheel from the axle be accomplished by sliding the roller wheel axially along the axle until it reaches and slides off the end of the axle. This type of access to the roller wheels may be acceptable during initial assembly, or in instances where the axle length is not great. However, in circumstances where the roller wheel is part of a complex assembly, or where the axle itself is relatively long, the need to remove a roller wheel from the axle in this manner becomes undesirable. An undesirable amount of disassembly and associated labor are thus expended replacing worn roller wheels and reinstalling new or refurbished roller wheels. The burden is particularly great when several roller wheels are mounted on a single axis, as it necessitates removal and subsequent replacement of all roller wheels between the defective wheel and the axle end.
Hence, it is desired to provide a roller wheel that can be quickly and easily installed on a drive axle without requiring access to the axle end. The desired roller wheel should also be durable and able to withstand the severe loading involved in cargo transfer.