Centrifuge screen

Details Centrifuge screen Centrifuge screen

2001-10-16

2003-12-16

Prince, Fred G. (Department: 1723)

Liquid purification or separation

Filter

Movable medium

C210S380100, C210S497010, C210S497300, 12

Reexamination Certificate

active

06663774

ABSTRACT:

BACKGROUND AND SUMMARY OF THE INVENTION
For example, the present invention relates to filtering devices, and particularly to centrifuges which utilize a screen to separate a solid from a liquid. More particularly, the present invention relates to centrifuges having screens which separate fine, particulate matter out of a liquid.
A conventional sugar refining process employs a centrifuge to separate sugar crystals out of raw molasses. The centrifuge includes a spinning drum having a truncated conical basket, which tapers towards its bottom. The walls of the truncated conical basket are lined with a screen material. In a typical sugar refining process, a raw molasses product containing sugar crystals is poured into the center of a centrifuge spinning at a very high rate—e.g. 1750 rpm. As the raw product containing sugar crystals is poured into the center of the centrifuge, centrifugal force pushes the raw molasses through the screen material, through the basket, and out of the centrifuge. However, the sugar crystals are too big to pass through the screen and are left behind. As the raw molasses pass through the screen, the spinning of the centrifuge forces the sugar crystals up the walls of the centrifuge. The sugar crystals work their way up the screen, eventually passing up and over the perimeter of the screen. In this way, sugar crystals are filtered out of liquid raw molasses product and are collected as they pass over the lip of the spinning screen.
To separate sugar crystals from raw product, the screen employed must be very fine. That is, the openings in the screen must be very small to prevent the sugar crystals from passing through the screen along with the liquid, raw molasses. Conventional sugar processing screens have been formed by “etching” a very thin metal plate. A metal plate may be etched with openings sized small enough to separate sugar crystals from liquid molasses. For example, a metal plate may be etched with a laser to form very small slits in the plate. The plate is then formed into a conical shape which fits within the walls of a centrifuge basket.
The greater the number of slits cut into a conventional sugar processing screen, the greater the “open area” of the screen. A large number of slits, spaced closely together, produces a relatively large “open area” in the screen, which increases the screen's production. However, the slits in a typical sugar processing screen weaken the overall screen and subject it to fatigue. Additionally, sugar crystals may lodge in the slits of a conventional sugar processing screen, thereby reducing its performance. A sugar processing device having a screen which is durable and has a fine opening, high open area would be welcomed by those in the sugar processing industry. Additionally, other industries that utilize such processes as coal dewatering and driller mud dewatering, etc. would welcome a fine opening, high open area centrifuge screen.
According to the present invention, a centrifuge screen comprises a series of fine filter wires spaced closely together and mounted generally perpendicularly to a series of underlying support rods.
In preferred embodiments, the filter wires have a V-shaped profile with a width of approximately 0.020 inches. The mating points of the support rods also have a V-shaped profile with a width of approximately 0.060 inches. The filter wires are spaced approximately 0.0035 inches apart and the support rods are spaced approximately 0.38 inches apart. However, it will be understood by one of ordinary skill in the art that different dimensions may be used to create a fine opening, high open area centrifuge screen used, for example, to separate crystalline sugar from liquid raw molasses.
Additional features and advantages will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.


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U.S. Filter Johnson Screens, Rugged, Dependable Screens for Mineral Processing, Apr. 1998, New Brighton, MN.

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