Agitating – Agitator – Stirrer
Reexamination Certificate
1999-03-02
2001-09-25
Soohoo, Tony G. (Department: 1723)
Agitating
Agitator
Stirrer
Reexamination Certificate
active
06293694
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of invention is flow promoting material handling conveyances, such as paddles and buckets, and particularly such conveyances which are for handling abrasive fluid (including dry or wet semi-fluid) materials.
Highly abrasive materials which need to be mixed, moved or otherwise handled are encountered in many industries, such as paper and pulp mills and power utilities. These industries engage in transporting and processing highly abrasive materials such as fly ash and wood pulp.
Fly ash is a combustion byproduct from solid fuels, such as coal. The fly ash is an abrasive fine particulate that has multiple commercial uses, but becomes an airborne pollutant if not handled properly. In paper and pulp mills, wood in the form of trees is reduced to a wood pulp that is very abrasive.
Processing the fly ash and wood pulp requires mixing and conveying the highly abrasive material using various means and methods. A known mixing apparatus, such as a pug mill, reduces a coarse substance, such as fly ash, into a pulp. The pugmills mix the fly ash with water to create a pulpy fluid. These mills commonly use mixing paddles to continuously mix and urge the fluid along the length of the pug mill toward an unloading position. Other known methods to convey fly ash or other abrasive materials incorporate buckets mounted on a continuous conveying belt or chain mechanism. The buckets scoop up the abrasive material and dump it at a destination prior to returning for another load.
The highly abrasive fly ash and wood pulp wears away the paddle and bucket material requiring frequent replacement. In addition to the highly abrasive characteristics of the fly ash and wood pulp, the material tends to stick to conventional paddles and buckets reducing their efficiency.
Known paddles and buckets are made of hardened steel which is abrasion resistant. In abrasive environments, such as pugmills and pugmill unloaders handling fly ash, abrasion resistant overlays can be applied to the steel paddles. These paddles are wear resistant, but material sticks to their surfaces, making cleaning difficult.
In order to resolve the sticking problem, paddles and buckets composed of flow promoting materials such as, Ultra High Molecular Weight—Polyethylene (UHMW), nylon, and urethane, have been developed. These materials have a low coefficient of friction which is flow promoting, but at a cost of reduced abrasion resistance. The ends of the paddles or walls moving through the abrasive material constantly wear away requiring paddle replacement.
Conventional methods of bonding abrasion resistant materials to UHMW have been unsuccessful because of the flow promoting properties of the UHMW. In addition, the difference in expansion and contraction characteristics of the UHMW and abrasion resistant materials renders conventional adhesive means unavailable.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an improvement to a conveyance construction for mixing a flowable abrasive material. The improvement includes a conveyance having a base with a surface made of a flow promoting material for contacting the abrasive material, and an edge. The edge is defined by an abrasion resistant material which is secured to the flow promoting material.
A general objective of the present invention is to provide an improved flow promoting construction for a fluid conveyance such as a mixing paddle or conveyor bucket. This objective is accomplished by securing an abrasion resistant material to an edge of a flow promoting material to provide a conveyance that is flow promoting and wear resistant.
In one useful form, the invention provides a flow promoting conveyance with a moldable ceramic composite fixed to a leading edge of the paddle or bucket. An abrasion resistant ceramic overlay is form fit to the leading edge of the flow promoting conveyance to provide a nonsticking wear resistant conveyance. Holes formed in a tongue portion of the conveyance at its leading edge allow the ceramic composite to bond to itself, creating a form fit mechanical joint with the body portion of the conveyance.
In another useful form, the invention provides a flow promoting conveyance with replaceable abrasion resistant edges. This is accomplished by overlaying a ceramic onto a steel insert which is mechanically attached to the leading edge of a conveyance with flow promoting surfaces.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration preferred embodiments of the invention. Such embodiments do not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims herein for interpreting the scope of the invention.
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Poly Hi Solidur Inc.
Quarles & Brady LLP
Soohoo Tony G.
LandOfFree
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