Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1998-12-02
2001-10-16
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S900000
Reexamination Certificate
active
06303241
ABSTRACT:
TECHNICAL FIELD
This application pertains to a retainer having a replaceable, magnetically retained wear plate for absorbing wear in discharge chutes, conveyors and other locations exposed to moving abrasives such as cement, sand, gravel, etc. Magnets embedded in the retainer are sandwiched between pole pieces which focus the magnetic field and protect the magnets.
BACKGROUND
Wear absorbing plates are commonly used to line chutes, hoppers, trunnions, chain runs, loading decks and other locations which are exposed to excessive wearing. For example, hardened wear plates are used to line surfaces over which cement, sand, gravel, or other abrasives flow. The objective is to reduce the rate of wear caused by such abrasives. Ordinarily, wear plates are formed of high grade steels having better abrasion resistant characteristics than the materials forming adjacent portions of the chute, hopper, trunnion, etc. The wear plate thus extends the useful life of the chute, hopper, etc.
Wear plates are normally affixed at wear points by welding, bolting, riveting, clamping or other relatively permanent means. Such forms of attachment can make it difficult, inconvenient, time consuming, labour intensive and/or expensive to remove and replace a wear plate which has worn out. Particular difficulties can arise if grinders or cutting torches are required to remove a worn out wear plate, for example if there is a hazard of fire or explosion in the adjacent surroundings, as is common in installations such as grain elevators, oil or gas refineries, saw mills, etc. Moreover, wear plates are often located in cramped working spaces which increase the difficulty of removing and replacing a worn out wear plate.
The present invention overcomes the foregoing difficulties by providing a wear plate which can be firmly magnetically retained at a wear point yet readily removed and replaced therefrom. The magnetized wear plate retainer also has impact absorbing characteristics which can improve the wear plate's capability to resist wear.
U.S. Pat. No. 4,340,616 discloses a method for decreasing surface wear by incorporating magnetic material into the surface to provide a sacrificial wear-resistant surface. For example, the wear resistant capability of a pipe which conveys an abrasive slurry can be improved. But this does not address the aforementioned difficulties encountered in removing and replacing a worn out wear plate.
SUMMARY OF INVENTION
The invention provides, in one embodiment, a wear plate retainer having upper and lower layers. The upper layer is formed of a relatively hard, impact and abrasion resistant material such as 80A durometer polyurethane material. The lower layer is formed of a relatively soft, shock-absorbent material such as 55A durometer polyurethane material. A plurality of magnets are embedded within the upper layer to removably and magnetically retain a wear plate atop the upper layer.
Pole pieces are embedded within the upper layer on opposite sides of each magnet and extending above the magnets. The pole pieces protect the magnets from impact forces and focus the magnetic field forces emanating from the magnets.
The magnets are preferably arranged in rows, with adjacent poles of adjacent pairs of magnets within adjacent rows having alternate polarity. The rows are respectively parallel to one another and extend transversely to a direction of material flow across the wear plate.
Advantageously, a plurality of shock-absorbing recesses can be formed in the lower layer.
Another embodiment of the invention requires only a less expensive, easily fabricated single layer of polyurethane material. The single layer may be either a relatively hard, impact and abrasion resistant material or a relatively soft, shock-absorbent material, depending upon which material's characteristics are preferred in the application of interest.
In a further embodiment, one may dispense with the wear plate and employ only a dual layer apparatus having magnets embedded in the lower layer. The apparatus is allowed to magnetically attach itself to a ferrous surface such as a suitable portion of a discharge chute, hopper, trunnion, etc. leaving the softer layer uppermost to cushion the impact of a fragile moving material.
REFERENCES:
patent: 3665355 (1972-05-01), Sasaki et al.
patent: 4529660 (1985-07-01), Heim
Allen Kenneth R.
Rampage Ventures Inc.
Resan Stevan A.
Townsend and Townsend / and Crew LLP
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