Imperforate bowl: centrifugal separators – With condition responsive means
Reexamination Certificate
2003-12-17
2004-10-05
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
With condition responsive means
C494S013000, C494S025000, C422S026000
Reexamination Certificate
active
06800053
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the sterilization of laboratory equipment. More particularly, the present invention relates to the sterilization of internal passages of a centrifuge centrate gate assembly.
BACKGROUND OF THE INVENTION
In normal centrifuge operation the centrifuge may possibly have contaminants carried into the internal piston cavities of the centrate gate assembly. Since the temperature is not monitored in this area, direct steam injection is needed to ensure complete steaming of the system.
A centrifuge body generally contains a centrate gate internally. This gate serves the purpose of isolating and discharging solids from the centrate discharge portion of the centrifuge. This prevents contamination and loss of any product.
Normally the centrate gate is raised and lowered using a 4-way directional control valve. However, these valves are not suitable for steam operation. The present invention addresses and corrects these shortcomings.
Many different types of centrifugal separators are known for separating heterogeneous mixtures according to “their specific gravities components”. A heterogeneous mixture, which may also be referred to as feed material or liquid feed, is injected into a rotating bowl of the separator. The bowl rotates at high speeds and forces particles of the mixture to separate from the liquid centrate. As a result, a dense solids cake compresses tightly against the surface of the bowl and the liquid centrate forms radially inward from the solids cake.
The bowl may rotate at speeds sufficient to produce 20,000 g's so that the solids may be separated from the centrate. Typically, the liquid feed travels at a relatively slow speed before being introduced through feed holes to the rotating bowl where the liquid feed is instantaneously accelerated to the angular speed of the rotating bowl. However, introducing the liquid feed to the bowl at such high speeds creates shear forces that often destroy a large amount of the solid component of the liquid feed before separation.
While the solids accumulate along the wall of the bowl, the centrate is drained. Once it is determined that a desired amount of the solids has been accumulated, the separator is placed in a discharge mode. In one such discharge mode, a scraper blade extending the length of the rotating bowl is placed in a scraping position against the separator wall and the bowl is rotated at a low scraping speed. Then, the solids are scraped from the sides of the bowl and fall toward a solids collecting outlet. However, such scraping systems do not effectively remove wet or sticky solids which may have the consistency of peanut butter. In such instances, the sticky solids remain stuck on the separator wall and scraper blades or fall from the wall and then reattach to the blades before reaching the collecting outlet. As a result, the solids recovery yield is reduced and the remaining solids undesirably contaminate the separator.
In equipment where potentially infectious specimens are processed and stored, contamination of the interior surfaces of the equipment and of the contents kept there due to spills and breakage of the specimens is an unfortunate but all too frequent occurrence. Removing the contaminated equipment from a busy laboratory for sterilization is often out of the question. Occasional manual cleaning with surface disinfectants has heretofore been the only practical solution. Another, less practical method of disinfecting, at least for smaller equipment, is to immerse it in glutaraldehyde. In some instances, contamination is so extensive that the equipment is discarded entirely and new equipment purchased to replace it.
Complete, in place sterilization of some laboratory equipment has not been possible, particularly in those items of equipment such as cold centrifuges and refrigerators having very cold interior surfaces or two or more zones of surfaces having widely differing temperatures. For example, some centrifuges maintain specimens at temperatures below 10° C. Other areas within the same centrifuge may be at room temperature.
In the centrifuge, airborne contamination is common. It would be desirable to sterilize the interior of the equipment before having to open it to remove the contents to spare the technician the risk of exposure to contamination. It would also be desirable to sterilize without the need of disassembly of the centrifuge.
It is an object of the present invention to provide an apparatus for sterilizing surfaces within equipment without having to disassemble the equipment, thereby decreasing costs and saving time. It is a further object of the present invention, to provide a process where surfaces can be sterilized by way of a novel valve assembly.
SUMMARY OF THE INVENTION
It is therefore a feature and advantage of the present invention to provide an apparatus and method for sterilizing the internal passages or cavities of a centrifuge centrate gate without the need to disassemble the centrifuge.
The above and other features and advantages are achieved through the use of a novel valve assembly as herein disclosed. In accordance with one aspect of the present invention there is provided a method of sterilizing a centrifuge, comprising the steps of lowering a centrate gate; closing an air control valve in communication with a gate cylinder; opening a first control valve, a second control valve, a third control valve and a fourth control valve which are all in communication with the gate cylinder; opening a steam control valve which is in communication with the gate cylinder thereby allowing steam to enter a piston cylinder cavity disposed within the gate cylinder; determining a system temperature; comparing the system temperature to a predetermined temperature; and toggling the centrate gate from a raised position to a lowered position until the predetermined temperature is reached.
In accordance with another aspect of the present invention there is provided an equipment sterilization apparatus, comprising means for lowering a centrate gate; means for closing an air control valve in communication with a gate cylinder; means for opening a first control valve, a second control valve, a third control valve and a fourth control valve which are all in communication with the gate cylinder; means for opening a steam control valve which is in communication with the gate cylinder thereby allowing steam to enter a piston cylinder cavity disposed within the gate cylinder; means for determining a system temperature; means for comparing the system temperature to a predetermined temperature; and means for toggling the centrate gate from a raised position to a lowered position until the predetermined temperature is reached.
In accordance with yet another aspect of the present invention there is provided a centrifuge sterilization apparatus, comprising a controller; a centrate gate disposed within a centrifuge body; a valve assembly in communication with the centrate gate, an air supply and a steam supply; and a plurality of temperature elements in communication with the controller, wherein the controller is configured to operate the valve assembly.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, a
Baker & Hostetler LLP
Cooley Charles E.
Kendro Laboratory Products LP
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