Caster
Casters are used in numerous applications, including shopping carts, office chairs, toy wagons, hospital beds, and material handling equipment.
High capacity, heavy duty casters are used in many industrial applications, such as platform trucks, carts, assemblies, and tow lines in plants.
Casters may be fixed to roll along a straight line path, or mounted on a pivot or pintle such that the wheel will automatically align itself to the direction of travel.
The improved swivel caster was invented in 1920 by Seibert Chesnutt, US Patent 1341630, which was easily manufactured by stamping, and incorporated ball bearings for longer life.
Basic swivel casters were in evidence in Charles Darwin's famous "office chair" as early as the 1840s.
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.
The angle of, and distance between the wheel axles and swivel joint can be adjusted for different types of caster performance.
They are used in a variety of applications including dolly carts, assembly turntables, heavy duty storage racks, holding bins, tow lines, maintenance equipment, and material handling mechanisms.
In early manufacturing, industrial caster bodies were typically fabricated from three separate, stamped metal parts, which were welded to the top plate.
Also, harder wheel materials (e.g., cast iron, high profile polyurethane) are less sensitive to and tend to not track dirt and debris on floors.
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.
They offer capacity and durability comparable to units having sealed precision ball or tapered bearings[citation needed], and are a practical alternative to traditional swivel casters in high-impact situations[why?].
Therefore, in order to accommodate this extra swivel space, lengthening of frame or extending the footrests may be required.
Anytime the caster begins to flutter, it slows the chair and shifts weight to the front wheels.
Parameters such as tire hardness, tread width and shape, the length of the trailing offset (the 'caster') and wheel diameter all affect the effort required to start the platform moving.
A less inflated tire offers more deformation resistance and thus more effort is required to move the attached platform.
[5] Enhancements to traditional caster design include toe guards, track wipers, reinforced legs, steering tubes, swivel locks and brakes, all implemented in an effort to reduce operator injuries in the workplace.
