Conveyors: power-driven – Conveyor having impinging fluid to feed – shift or discharge... – Having cleaning means
Reexamination Certificate
2002-01-28
2003-06-10
Valenza, Joseph E. (Department: 3651)
Conveyors: power-driven
Conveyor having impinging fluid to feed, shift or discharge...
Having cleaning means
Reexamination Certificate
active
06575292
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a conveyor belt cleaner and tensioner assembly including a conveyor belt cleaner having a scraper blade that provides a constant cleaning angle with a conveyor belt and that is resiliently biased into cleaning engagement with the conveyor belt by a tensioner mechanism.
Conveyor belts transport various types of bulk material such as sand, coal, grain and ores. Conveyor belt cleaners remove conveyed material that continues to adhere to the rotating conveyor belt after the remainder of the conveyed material has been discharged. A scraper blade of a conveyor belt cleaner can be orientated with respect to the surface of the conveyor belt at an obtuse or negative angle, which is referred to as a “peeling” angle, or the scraper blade can be orientated at an acute or positive angle with respect to the conveyor belt which is referred to as a “scraping” angle. It has been found that scraper blades used in connection with conveyor belts conveying certain bulk materials with fines, such as ores, clean the conveyor belt more efficiently when the scraper blades are orientated at a peeling or negative angle with respect to the conveyor belt, rather than at a scraping or positive angle.
Current belt cleaners that have scraper blades disposed at a peeling angle are prone to vibrate or chatter against the belt which lowers the cleaning efficiency of the belt cleaner and can cause damage to the conveyor belt and to the belt cleaner. Another problem with peeling angle scraper blades is that the scraper blades must be precisely aligned with the belt to avoid damaging the belt, and it is difficult to achieve the desired belt to scraper blade contact during installation of a conveyor belt cleaner. Belt damage usually results when one corner of a scraper blade is in engagement with the conveyor belt rather than the entire scraper blade contact area.
A problem that is encountered by both peeling angle and scraping angle conveyor belt cleaners is the tendency of the conveyor belt cleaner or the belt to become damaged when the conveyor belt reverses direction or “rolls back” momentarily. Conveyor belt reversal or roll back happens frequently when the conveyor belt goes through a normal shutdown sequence. The belt thereafter rolls backward from a few inches to a few feet as the belt tension relaxes. This roll back motion tends to catch the scraper blade, forcing the blade backward and bending the arm on which the scraper blade is mounted, or otherwise causing the scraper blade to swivel out of alignment. Sometimes the scraper blades do not swivel back into their original cleaning position when the conveyor belt is restarted, or the damage is so severe to the arm that the belt cleaner no longer functions. Even worse is the potential for damaging the belt when it resumes forward motion if the scraper blade is locked in a position where only a corner of the scraper blade is in engagement against the belt.
The preferred peeling angle or scraping angle with which a scraper blade engages the conveyor belt varies depending upon the type or grade of materials that are being conveyed. Conveyor belt cleaners are typically designed for operating optimally at a single peeling angle or scraping angle and are not adjustable to provide changes in peeling angle or scraping angle to accommodate changes in the type or grade of conveyed material.
Conveyor belt cleaners have also required the use of external tensioners that include a rubber or elastomeric torsion member that is twisted to store a rotational biasing force which pivots the scraper blades into biased engagement with the conveyor belt. These external tensioners add expense to the conveyor belt cleaner, and if the external tensioner fails, all of the scraper blades of the conveyor belt cleaner will fall away from, and out of cleaning engagement with, the conveyor belt. External tensioners also often need to be re-tensioned during the life of the scraper blades as they provided a non-linear output force over their range of operation.
SUMMARY OF THE INVENTION
A conveyor belt cleaner and tensioner assembly adapted to be attached to a cross shaft. The conveyor belt cleaner and tensioner assembly includes a mounting base adapted to be mounted to the cross shaft, and an arm member having a first end and a second end. The first end of the arm member is pivotally attached to the mounting base and thereby to the cross shaft for pivotal movement about a first pivot axis. A scraper blade is attached to the second end of the arm member. A tensioner mechanism includes a first end pivotally attached to the mounting base and a second end pivotally attached to the arm member. The tensioner mechanism is preferably a gas spring tensioner including a housing having a cavity and a ram having a first end located within the housing and a second end located externally of the housing. The ram is extendable and retractable with respect to the housing to thereby pivot the arm member and the scraper blade with respect to the mounting base about the pivot axis. The scraper blade is removably attached to the second end of the arm member and is pivotal with respect to the arm member about a second pivot axis that is generally perpendicular to the first pivot axis. The scraper blade includes an arc-shaped inner surface and an arc-shaped outer surface, each of which is formed by a respective radius which extends from the first pivot axis.
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Barnes & Thornburg
Martin Engineering Company
Valenza Joseph E.
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