Refractory bearing

Abstract

At least one bearing insert is secured within a metallic housing to form a wear resistant bearing. In operation, the bearing insert engages a journal and provides a wear-resistant surface. The housing defines a cavity for receiving the bearing insert. The cavity preferably expands radially so that the bearing insert remains secured in the cavity. The bearing insert can comprise a refractory ceramic. The bearing insert is secured within the cavity by any suitable means, such as thermal shrink-fit. A thin layer of sacrificial metal protects the bearing insert during initial start-up. The sacrificial metal wears to expose the bearing insert. Further wear exposes a larger area of the refractory bearing insert. A second bearing insert can be disposed opposite to the first so that rotating the housing can expose the second bearing insert to the journal.

Claims

1. A refractory bearing comprising: a) at least one bearing insert comprising a refractory material; and b) a housing having a radius and an inner surface, the inner surface defining at least one cavity for receiving the bearing insert, the cavity separated from the inner surface by a sacrificial layer.

2. The refractory bearing of claim 1, characterized by the bearing insert comprising a refractory ceramic.

3. The refractory bearing of claim 2, characterized by the refractory ceramic selected from a group consisting of sialon, zirconia, and combinations thereof.

4. The refractory bearing of claim 1, characterized by the housing comprising a cylinder.

5. The refractory bearing of claim 1, characterized by the cavity enlarging radially, whereby the bearing insert is secured in the cavity.

6. The refractory bearing of claim 1, characterized by the cavity defining a cylindrical shape and the bearing insert comprising a cylinder.

7. The refractory bearing of claim 1, characterized by the housing defining a plurality of cavities for a plurality of bearing inserts.

8. The refractory bearing of claim 7, characterized by the plurality of bearings comprising a first bearing insert and an opposite bearing insert, the opposite bearing insert disposed on the inner surface opposite to the first bearing insert.

9. The refractory bearing of claim 8, characterized by the first bearing insert comprising a plurality of bearing inserts.

10. The refractory bearing of claim 8, characterized by the opposite bearing insert comprising a plurality of bearing inserts.

11. The refractory bearing of claim 1, characterized by the bearing insert being shrink-fitted into the cavity.

12. The refractory bearing of claim 1, characterized by the bearing insert secured in the cavity by a positive mechanical interlock.

13. The refractory bearing of claim 1, characterized by the sacrificial layer being less than 5 mm thick.

14. The refractory bearing of claim 1, characterized by the sacrificial layer being less than 1 mm thick.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a longitudinal view of a housing with refractory inserts of the present invention.

(2) FIG. 2 is a cross-sectional view of the insert of FIG. 1.

(3) FIG. 3 is a magnification of FIG. 2.

(4) FIG. 4 shows alternative refractory shapes.

(5) FIG. 5 is a longitudinal view of an alternative embodiment having a housing with refractory inserts.

(6) FIG. 6 is a cross-sectional view of the insert of FIG. 5.

(7) FIG. 7 is a longitudinal view of an alternative embodiment having a housing with refractory inserts.

(8) FIG. 8 is a cross-sectional view of the insert of FIG. 7.

(9) FIG. 9 is a magnification of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIGS. 1-3 show a housing 1 having an inner surface 5 with a bearing insert 2 embedded just below the inner surface 5 so that a thin sacrificial layer 3 is between the bearing insert 2 and the inner surface 5. The housing can comprise a cylinder. The housing 1 can comprise a temperature- and chemical-resistant metal such as, for example, type 316L stainless steel. The housing 1 can receive a roll or journal capable of rotation. The bearing insert 2 can comprise a suitable refractory ceramic such as, for example, sialon or zirconia. FIG. 1 shows a plurality of bearing inserts 2. The bearing inserts 2 are placed just below the inner surface 5 of the housing 1 so that the inserts 2 are covered by the sacrificial layer 3. The sacrificial layer 3 between the inside surface 5 of the housing and the bearing insert 2 is sacrificial, i.e. it is quickly consumed by contact with the rotating roll or journal. The sacrificial layer 3 protects the bearing insert 2 during initial startup. The sacrificial layer will be less than about 5 mm thick and preferably less than about 1 mm.

(11) The bearing insert will be placed in a cavity defined by the housing. The cavity will enlarge radially so that the bearing insert remains secured in the cavity, especially as wear occurs, and reduces the likelihood that the bearing insert will fall out. Conveniently, the bearing inserts can be cylindrical or other suitable cross-sections. A cylindrical shape facilitates production of the bearing inserts and requires little tooling before use. For example, refractory ceramics are commonly extruded in tubular form as smooth cylinders. The invention anticipates, however, that other shapes could be used such as shown in FIG. 4.

(12) In an embodiment, the bearing insert is shrink-fitted into a cavity of the housing to provide additional fixity in service. This technique is beneficial when the bearing insert has a lower thermal expansion coefficient than the housing. For example, a typical refractory ceramic will expand less than a metal. Heating the metal housing will increase the size of the cavity and subsequent shrinkage when the housing decreases in temperature will increase the frictional fit of this embodiment.

(13) FIG. 5 shows an alternative embodiment. The bearing inserts 2 are constrained with a positive mechanical interlock 11. The mechanical interlock can include a plate welded to the end of the housing 1. See longitudinal cross-section in FIG. 6. In an embodiment, a relief cut (not shown) is made into the housing and the retainer can be secured to the housing inside this relief cut.

(14) FIGS. 7-9 show an alternative embodiment in which the housing includes a plurality of sets of bearing inserts, namely a first bearing insert 21 and an opposite bearing insert 22. As shown, the first bearing insert and the opposite bearing insert both comprise a plurality of inserts. The first bearing 21 will wear, and conveniently the housing can be rotated so that the opposite bearing insert 22 engages the roll or journal. The sacrificial layer has preserved the opposite bearing insert when not in use. This feature permits, for example, multiple galvanizing campaigns from a single housing thereby reducing production downtime.

(15) A cylindrical profile reduces costs and necessary parts. Additionally, modified configurations permit additional curvature coverage for special cases where angle of force changes during operation.