Abstract:
Methods and apparatus for sterilization of laboratory equipment, which are particularly suited for sterilization of internal passages of a centrifuge centrate gate assembly.

Description:
PRIORITY CLAIM  
       [0001]    This application claims priority to provisional U.S. Patent Application Serial No. 60/435,255, filed Dec. 23, 2002, the disclosure of which is incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    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  
         [0003]    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.  
           [0004]    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.  
           [0005]    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.  
           [0006]    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.  
           [0007]    The bowl may rotate at speeds sufficient to produce 20,000 g&#39;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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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.  
           [0011]    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.  
           [0012]    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  
         [0013]    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.  
           [0014]    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.  
           [0015]    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.  
           [0016]    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.  
           [0017]    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.  
           [0018]    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, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting.  
           [0019]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a block diagram of one preferred embodiment of the present invention.  
         [0021]    [0021]FIG. 2 is an illustration of a conventional centrate gate configuration.  
         [0022]    [0022]FIG. 3 is an illustration of the centrate gate and valve configuration in accordance with a preferred embodiment of the present invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0023]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a centrate gate  34  internal to a centrifuge body  32 . This gate is configured to allow steam sterilization of any internal passages of the gate cylinder  46  by way of a valve assembly  30 .  
         [0024]    An embodiment of the present inventive apparatus and method is illustrated generally in FIG. 1. The behavior of the centrifuge system  10  of the present invention is controlled by the system controller  12  in conjunction with various temperature sensors  18  and valves  16 . This controller  12  may be a personal computer (PC), an embedded controller or a programmable logic control (PLC) preferably. The controller  12  is responsible for positioning the valves  16  and centrate gate  14  to achieve the desired actions, i.e., raising, lowering and steaming. The steaming cycle is performed in conjunction with the machine steam sterilization.  
         [0025]    Referring to FIG. 2, in a conventional centrate gate configuration  20 , a valve  21  is the only control associated with the centrate gate  24 , centrifuge body  22 , piston  28  and cavity  29  via lines  23 ,  25 . This valve  21  controls the air supply  26  and air exhaust  27  alone.  
         [0026]    Referring to FIGS. 1 &amp; 3, a controller  12  determines that the system temperature has stabilized at its temperature set point. Subsequently, the controller  12  then sequences the valves  16 . This is done to minimize any damage to the piston seals (not shown). During the system&#39;s at temperature hold time the controller  12  alternately raises and lowers the centrate gate  34 . The controller  12  then turns the air off, vents trapped air in the piston  46 , and turns the steam  37  on to allow the steam to flow through the piston cavities  47 . This cycling ensures that all internal surfaces of the piston cavity  47  have direct steam contact during the cycle.  
         [0027]    The centrate gate  34  is an internal part of a centrifuge body  32  usually in the families of industrial production and laboratory units. Its purpose is to isolate the discharged solids from the centrate discharge portion of the centrifuge body  32 . This prevents the possible contamination and loss of product.  
         [0028]    During operation, it is possible to drag liquid and possibly solid particles into the centrate gate cylinder chambers/cavities  47 . If the internal chambers  47  of the gate  34  are not sterilized between product runs, it may be possible to contaminate the next batch with material from the previous batch.  
         [0029]    As depicted in FIG. 3, a preferred embodiment of the invention provides a valve assembly  30  comprising a first control valve  35 , a second control valve  39 , a third control valve  40  and a fourth control valve  41 . These four control valves  35 ,  39 ,  40 ,  41  are used together to control the gate position. The valve assembly  30  is used to allow either steam  37  or air  36  to flow through the control valves  35 ,  39 ,  40 ,  41  to the centrate gate  34 . This invention may also require the centrate gate cylinder  46  to be double ported on both ends and either steam traps or flow orifices connected in series with the valves used to exhaust the piston cavities  47 .  
         [0030]    Again referring to FIG. 3, in the present invention, the centrate gate  34  is still controlled but it is now possible to steam sterilize the internal passages  47  of the gate cylinder  46 . Positioning control is realized by using valves,  31 ,  35  and  41  for the raised position and valves  31 ,  39  and  40  to move the gate to a lowered position. Valve  31  is an air control valve.  
         [0031]    Steaming is accomplished by closing the air control valve  31  and opening valves  35 ,  39 ,  40  and  41 . This allows steam  37  to flow through the cylinder cavities  47  and out the flow or pressure orifices  44 ,  45 . These orifices  44 ,  45  are sized so that there is enough pressure maintained in the gate cavities  47  to reach the desired sterilization temperature. The orifices  44 ,  45  are in communication with an air/condensate exhaust  38 . The temperature elements  42 ,  43  are disposed inline with and between valves  40  and  41  and there respective orifices  44 ,  45  accordingly. These temperature elements  42 ,  43  may be preferably either resistance temperature detectors (RTD) or thermocouples. The temperature elements  42 ,  43  are used to detect when the temperature of the steam exiting the gate chambers  47  has reached the predetermined sterilization temperatures as desired.  
         [0032]    The first step in sterilization is to lower the centrate gate  34 . Next the air  36  to the gate cylinder  46  is turned off and valves  35 ,  39 ,  40  and  41  are opened. After a predetermined time delay the steam control valve  33  is turned on as is the steam  37  for the centrifuge body  32 . When the centrifuge body  32  reaches the predetermined sterilization temperature or set point temperature and the temperature elements  42 ,  43  are at the sterilization temperature as well, the centrate gate&#39;s position is toggled from a lowered position to a raised position. For the duration of the steaming cycle, the centrate gate&#39;s position is toggled up and down about every 30 seconds. This process exposes all internal surfaces to live steam and minimizes cold spots in the gate  34 .  
         [0033]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirits and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.