Airport Trolley (AZC0009)

Size: 75 * 32
Material: Rubber
Weight: 55KG load

Casters may be fixed to roll along a straight line path, or mounted on a pivot such that the wheel will automatically align itself to the direction of travel.
Rigid casters
A basic, rigid caster consists of a wheel mounted to a stationary fork. The orientation of the fork, which is fixed relative to the vehicle, is determined when the caster is mounted to the vehicle. An example of this is the wheels found at the rear of a shopping cart in North America. Rigid casters tend to restrict vehicle motion so that the vehicle travels along a straight line.
Swivel casters
A swivel caster.
Like the simpler rigid caster, a swivel caster incorporates a wheel mounted to a fork, but an additional swivel joint above the fork allows the fork to freely rotate about 360° , thus enabling the wheel to roll in any direction. This makes it possible to easily move the vehicle in any direction without changing its orientation. Swivel casters are sometimes attached to handles so that an operator can manually set their orientation.
Additionally, a swivel caster typically must include a small amount of offset distance between the center axis of the vertical shaft and the center axis of the caster wheel. When the caster is moved and the wheel is not facing the correct direction, the offset will cause the wheel assembly to rotate around the axis of the vertical shaft to follow behind the direction of movement. If there is no offset, the wheel will not rotate if not facing the correct direction, either preventing motion or dragging across the ground.
When in motion along a straight line, a swivel caster will tend to automatically align to, and rotate parallel to the direction of travel. This can be seen on a shopping cart when the front casters align parallel to the rear casters when traveling down an aisle. A consequence of this is that the vehicle naturally tends to travel in a straight direction. Precise steering is not required because the casters tend to maintain straight motion. This is also true during vehicle turns. The caster rotates parallel to the turning radius and provides a smooth turn. This can be seen on a shopping cart as the front wheels rotate at different velocities, with different turning radius depending on how tight a turn is made.
The angle and distance of the wheel axles and swivel joint can be adjusted for different types of caster performance.
Braking and locking casters
A swivel caster with a wheel lock. The vertical swivel on this type of caster can not be locked in position.
Caster central locking mechanism on an old Stryker hydraulicstretcher. Shown in the locked position with the center cam rotated downward. The lever handle may be operated by hand or foot. A rod extends underneath to the opposite side to actuate another cam, and with another operating handle. Note this type of central locking mechanism isn't directly part of the caster itself, and could be applied to nearly any type of standard swivel caster.
Common inexpensive casters may include a brake feature, which prevents the wheel from turning. This is commonly achieved using a lever that presses a brake cam against the wheel. However a swivel caster is still able to move around slightly, in a small circle rotating around offset distance between the vertical shaft and the center of the locked wheel.
A more complex type of swivel caster, sometimes called a total lock caster, has an additional rotational lock on the vertical shaft so that neither the shaft can rotate or the wheel can turn, providing very rigid support. It is possible to use these two locks together or separately. If the vertical shaft is locked but the wheel can still turn, the caster becomes a directional caster, but one which may be locked to roll in one direction along any horizontal axis.