Conveyors: power-driven – Conveyor having impinging fluid to feed – shift or discharge... – Having cleaning means
Patent
1995-04-10
1996-11-05
Terrell, William E.
Conveyors: power-driven
Conveyor having impinging fluid to feed, shift or discharge...
Having cleaning means
B65G 4510, B65G 4516
Patent
active
055707742
DESCRIPTION:
BRIEF SUMMARY
This invention relates to belt scrapers, being belt scrapers of the kind used to scrape caked material from conveyor belts.
BACKGROUND TO THE INVENTION
Conveyor belts are in common use in mines, for the transport of ore to and from crushing, milling, and comminuting machines. Dust and fine particles of crushed ore can become caked very firmly indeed to the belt, especially if moisture is present.
Scraping caked material from mine conveyor belts is well-known to be a most demanding task. The task is usually approached on the basis of pressing a scraper blade against the (moving) face of the belt. The scraper blade gradually wears down under the abrasive conditions, and one of the problems of belt-scraping lies in providing a scraper blade of sufficient length that the blade has a long service life between replacements.
The conventional approach to the problem that the blade has only a short life is to press the blade against the belt with less force. The invention is aimed at providing an economical scraper in which the blade has a long service life, yet in which the blade is pressed against the belt with sufficient force for excellent scraping.
U.S. patent publication no U.S. Pat. No. 5,048,667 (MORIN, 17-Sep.-91) shows a scraper assembly in which the scraper blade is of flexible plastic material, which is rolled into a coil. This arrangement has led to a scraper assembly in which the scraper blade need only be changed on, say, an annual basis, as against the every-six-weeks replacement which has tended to be the industry standard in the most demanding situations.
One of the problems that has arisen in regard to these coiled-blade scraper assemblies is that the blade can tend to stick or "freeze" to the inside of the blade housing. As is shown in '667, the coiled blade is contained inside a cylindrical housing. The inherent stiffness of the blade material means that the blade tends to try to unroll itself within the housing; in fact, the blade tends to uncoil itself until the material of the blade lies in direct touching contact with the inside of the housing.
Once the blade has unrolled itself as much as it can inside the housing, the friction of the blade material against the inside of the housing builds up, and this friction can make it difficult for the blade to move and rotate within the housing.
If the blade is allowed to unroll inside the housing, ie if the blade is allowed to unroll itself and make frictional contact against the inside wall of the housing, the force required to drive the blade out of the housing therefore increases; not only is the need for the increased force a disadvantage, but another disadvantage is that some of the controllability of the pressure of the blade against the belt is lost.
It may be noted that the friction is caused by the tendency of the belt to uncoil itself, rather than by the pressure forcing the blade against the belt.
In the said patent '667, the blade is driven out of the housing and against the belt by means of fluid pressure inside the housing. One benefit of this system is that the reaction to the belt contact force is not supported by direct touching contact between the coil and the housing, which eliminates a source of what would be a considerable friction. However, the material of a scraper blade, even though able to be wound into a coil, nevertheless is characterized as being very stiff and intractable; where the material does touch the housing as a result of its trying to uncoil itself, the friction arising from that contact can be considerable.
Thus, in '667, the blade is forced out of the housing in such a manner that the actuation force on the blade does not give rise to a frictional resistance proportional thereto: the friction that arises simply due to the tendency of the blade to uncoil itself inside the housing, is the problem with which the invention is concerned. The problem exists because the coil of blade material tends to unwind itself until it comes into contact with the housing, or with whatever is present that prevents it unwinding
Reichard Dean A.
Terrell William E.
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