Views: 34 Author: Site Editor Publish Time: 2018-07-05 Origin: www.fuchun-casting.com
A pillow block is a pedestal used to provide support for a rotating shaft with the help of compatible bearings & various accessories. Housing material for a pillow block is typically made of cast iron or cast steel.
A pillow block usually refers to a housing with an included anti-friction bearing. A pillow block refers to any mounted bearing wherein the mounted shaft is in a parallel plane to the mounting surface, and perpendicular to the center line of the mounting holes, as contrasted with various types of flange blocks or flange units. A pillow block may contain a bearing with one of several types of rolling elements, including ball, cylindrical roller, spherical roller, tapered roller, or metallic or synthetic bushing.
Bearings used with pillow block housings usually are self- aligning to compensate for angular misalignments. Pillow blocks are available with many different bearing types, including:
Plain bearings are used to constrain, guide, or reduce friction in linear applications. They use a sliding action instead of the rolling action used by ball, roller, and needle bearings. Plain bearings can be constructed of a variety of materials, but are typically bronze, a graphite-metal allow, or plastic. Metal plain pillow block bearings must be lubricated properly to reduce wear and friction. Bronze plain bearings may also be either impregnated with oil or self-lubricating.
Ball bearings have a ball as the rolling element. They are used to provide smooth, low friction motion in rotary applications. Construction consists of an inner and outer ring, balls, and usually a cage or ball separator. Ball pillow block bearings feature an inner and outer ring and balls. They may be equipped with a cage or ball separator.
Roller bearings have a roller as the rolling element. They are used to provide smooth, low friction motion in rotary applications. Construction consists of an inner and outer ring, rollers, and usually a cage or roller separator. There are three principal types of roller bearings used in pillow blocks:
Tapered-roller bearings use conical rollers that run on conical races. They can support both radial and axial loads as well as carry higher loads than ball bearings due to having greater contact area. Tapered-roller bearings contain an inner ring (cone), an outer ring (cup), a cage, and rollers. They have high radial and axial load capacities when used at low to intermediate speed levels. The thrust level of tapered-roller pillow block bearings is about 60% of the radial capacity. They are usually more expensive.
Spherical- roller bearings are self-aligning, double-row, combination radial and thrust bearings. The rolling element in these pillow block bearings has a crowned or spherical shape. Spherical-roller pillow block bearings are superior when dealing with high loads and loads that require tolerance to shock; however, they have limited speed capabilities.
Cylindrical-roller bearings are bearings with high radial capacities and moderate thrust loads. They can be crowned or end-relieved for reduced-stress concentrations. Cylindrical-roller pillow block bearings produce low friction and allow for high-speed.
Needle-roller bearings have a needle roller as the rolling element. They are similar to cylindrical roller bearings but have a smaller diameter-to-length ratio. By controlling the circumferential clearance between rollers, or needles, rolling elements are kept parallel to the shaft axis. Needle roller bearings are designed for radial load applications where a low profile is desired.
Hydrodynamic bearings are fluid film bearings that rely on a film of oil or air to create a clearance between the moving and stationary elements. Hydrodynamic pillow block bearings maintain high stiffness, load capacity, and long bearing life, but are considerably more complex and expensive than standard rolling element pillow block bearings.