1. Field
Embodiments of the present invention relate to bearing arrangements for rotatably supporting roll shafts in a rolling mill. The invention is particularly suited for, although not limited in use to, high speed rolling mills having so called “cantilevered” roll shafts with axially projecting ends adapted to carry the work rolls.
2. Description of Related Art
As herein employed, “oil film bearing” means a bearing in which the rotating element is supported on a film of oil. “Hydrodynamic bearing” means an oil film bearing which relies on the high speed of the rotating element to pressurize the oil in a wedge-shaped film at the bearing load zone. “Hydrostatic bearing” means an oil film bearing which employs a positive pressure supply of oil to maintain a clearance between the rotating and stationary elements.
In a conventional high speed rolling mill, as depicted in
In addition to having a limited useful life, thrust ball bearings have been found to lack the stiffness required to provide axial precision for the rolling operation. While radial hydrodynamic bearings operate satisfactorily, they have been found to compromise radial precision because the thickness of the oil films supporting the rolls varies in response varying bearing loads.
Broadly stated, embodiments of the present invention address the above described problems by providing an improved bearing arrangement in which both the radial and thrust bearings are oil film bearings.
In exemplary embodiments of the present invention, the thrust bearings may be hydrodynamic bearings, but preferably will comprise hydrostatic bearings. Similarly, although the radial bearings may be hydrodynamic bearings, hydrostatic bearings are preferable.
Optimum stiffness is achieved by employing hydrostatic bearings for both the radial and thrust applications.
These and other features and advantages of present invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.
The components described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components that would perform the same or a similar function as well as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.
In accordance with exemplary embodiments of the present invention, as depicted in
The first and second radial bearings 20a, 20b may be hydrodynamic bearings, but hydrostatic bearings are preferred. Similarly, although the third and fourth thrust bearings 26a, 26b may be hydrodynamic bearings, hydrostatic bearings are again preferred. Maximum stiffness is achieved by employing hydrostatic bearings for the first and second radial bearings 20a, 20b and the third and fourth thrust bearings 26a, 26b.
It is to be understood that while preferred embodiments of the present invention have been described, such embodiments should be considered as illustrative and may be modified by those skilled in the art without departing from the scope of the present invention, as defined by the appended claims.