Patent Publication Number: US-7592155-B2

Title: Filter snapper

Description:
The present application is a divisional of application Ser. No. 10/951,875, filed Sep. 29, 2004 (now U.S. Pat. No. 7,435,576), which claims the benefit of U.S. Provisional Application No. 60/506,733 filed Sep. 30, 2003, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device and a method for separating a filter ring component from a fluid-holding reservoir component of a funnel with minimal operator effort. 
     2. Description of the Background Art 
     In certain sterile operations (e.g., laboratory and manufacturing procedures), it is necessary to regularly monitor fluid supplies, such as water supplies, used in such procedures to ensure that they do not contain unacceptable levels of contaminants, such as biological contaminants. Typical biological contaminants include bacteria and fungi. One method of monitoring fluid supplies involves passing a specified sample volume of a fluid from a fluid supply through a filter, positioning the filter on a contained biological growth medium (e.g., an agar plate), enclosing and incubating the contained biological growth medium, and then observing the level of the biological growth at prescribed intervals of time. Specialized filtration testing systems are manufactured for this purpose. 
     One such filtration testing system is illustrated in  FIGS. 1-3 . This filtration testing system  60  includes a funnel  10  that includes a fluid-holding cup  12  for receiving an amount of a fluid to be tested and a filter ring  20  having a filter  26  (e.g., a filtration mesh) disposed across its opening. More specifically, the cup  12  includes a top end  14 , a bottom end  16  having a width (e.g., diameter) less than that of the top end  14 , and a frusto-conical section  18  The filter ring  20  includes a wide portion  22  and a narrow portion  24  having a width (e.g., diameter) less than that of the wide portion  22 . The filter  26  is disposed generally between the wide portion  22  and the narrow portion  24 . The filter ring  20  is frangibly attached, at frangible connection  28 , to the bottom end  16  of the cup  12 . The frangible connection  28  is constructed and arranged to break upon application to the funnel  10  of a sufficient compressive axial force, thereby permitting the narrow section  24  of the filter ring to collapse into the bottom end  16  of the cup  12 . After the frangible connection  28  is broken, the filter ring  20  and cup  12  can be separated from each other. 
     The system  60  further includes a growth medium plate  30  (e.g., an open-ended agar plate), a lower cover plate  40 , and an upper cover plate  50 . 
     The filter ring  20  can be connected to the growth medium plate  30 . The growth medium plate  30  has a size and shape that conforms to the interior of the wide portion  22  of the filter ring  20 , permitting the plate  30  to be snugly inserted into the wide portion  22  as shown  FIG. 3 . The growth medium plate  30  includes a layer of growth medium  32  supported by a lattice structure  34 . An inner extension  36  is preferably circular and projects away from the growth medium  32  and lattice structure  34 , generally encircling the growth medium  32  and the lattice structure  34 . 
     The lower cover plate  40  has a size and shape that conforms to the interior of the growth medium plate  30 , permitting the lower cover plate  40  to be snugly inserted into the growth medium plate  30  as shown  FIG. 3 . When the lower cover plate  40  is inserted into the plate  30 , a top surface  42  of the lower cover plate  40  makes contact with the inner extension  36 , thereby forming a partial enclosure surrounding the growth medium  32  and the lattice structure  34 . 
     The upper cover plate  50  includes a first extension  52  and a second extension  54 . The first extension  52  has a size and shape that permits that upper cover plate  50  to be secured to the top end  14  of cup  12  by inserting the first extension  52  into the cup  12 . After the cup  12  and the filter ring  20  have been separated from each other, the second extension  54  has a size and shape that permits the upper cover plate  50  to be secured to the narrow portion  24  of the filter ring  20  by inserting the second extension  54  into the narrow portion  24 . 
     The funnel  10 , in combination with the growth medium plate  30 , the upper cover plate  50 , and the lower cover plate  40 , make up the fluid contamination detection system  60  having an overall axial length L. A suitable system of the type shown in  FIGS. 1-3  is the Milliflex™ HAWG 0.45 μM, sterilized filtration funnel available from the Millipore Corporation, Bedford, Mass. (Cat. No. MXHAWG124). This system may further include, for example, a Prefilled Milliflex™ Cassette containing tryptic soy agar available from the Millipore Corporation (Cat. No. MXSMCTS48). 
     In a conventional fluid contamination detection system and procedure, the funnel  10  is placed on a suction mechanism, or vacuum suction, (such as the Milliflex™ Sensor II automatic vacuum available from the Millipore Corporation (Cat. No. MXP520015)), a prescribed volume of fluid (e.g., about 10 mL) is then poured into the cup  12 , and the fluid contents of the cup  12  are drawn through the filter  26  of the filter ring  20 . After the fluid has been drawn through the filter  26 , the growth medium plate  30  is joined to the filter ring  20  so that the growth medium  32  contained within the growth medium plate  30  contacts the filter  26  of the filter ring  20 . Thereafter, the filter ring  20  and growth medium plate  30  are separated from the cup  12 . To separate the filter ring  20  and growth medium plate  30  combination from the cup  12 , the filter  10  and growth medium plate  30  are manually squeezed between the palms and fingers of an operator&#39;s hands to apply an axial compressive force to the filter  10  and growth medium plate  30  that is sufficient to break the frangible connection  28  joining the cup  12  and ring  20  so that the narrow portion  24  of the filter ring  20  collapses into the bottom end  16  of the cup  12 . The filter ring  20  and growth medium plate  30  are then separated from the cup  12 , and the upper cover plate  50  is joined to the open end of the filter ring  20  before incubating the enclosed growth medium plate  30  at a temperature of about 37° C. 
     It is generally desirable to perform this procedure in a laminar flow hood in order to limit exposure of the filter to airborne contaminants that could interfere with fluid monitoring test results. During the incubation phase, the growth medium plate  30  is examined at prescribed time intervals, e.g., 24, 48, and 72 hours, and the number of colonies that have formed on the plate (the bioburden) is determined. Such a fluid contamination detection system is especially important for the clinical diagnostics industry, where the presence of biological contaminants in fluids used to manufacture reagents for commercial test kits could affect the results of assays performed using those test kits. 
     A problem with the fluid contamination detection system and procedure described above is that laboratory and manufacturing facilities might have to perform dozens of fluid contamination detection tests in a day. As a consequence, an operator may be required to repeatedly apply a manual force with their hands to separate filter ring  20  and growth medium plate  30  combinations from corresponding cups  12 , often resulting in discomfort to the operator&#39;s hands or, more seriously, causing repetitive stress injuries, such as carpal tunnel syndrome. Accordingly, there is a need for a device and method that overcome the problems associated with isolating filter ring  20  and growth medium plate  30  combinations in traditional detection systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a novel solution to the repetitive stress problems associated with conventional methods of testing fluids for the presence of contaminants. 
     Thus, one aspect of the present invention is embodied by a device for applying an axial compressive force to a fluid contamination detection system comprising a funnel in order to break a frangible connection joining first and second members of the funnel. The device includes a stop element, a movable platform supported relative to a base, and an actuating mechanism. The platform is disposed in an opposed, spaced-apart relationship relative to the stop element. The platform is movable relative to the stop element between a first position in which the platform is spaced-apart from the stop element by a distance greater than the axial length of the detection system a second position in which the platform is spaced-apart from the stop element by a distance less than the axial length of the detection system. The actuating mechanism causes movement of the platform between the first and second positions. The platform is movable from the first position to the second position during which movement a portion of the detection system contacts the stop element, resulting in an axial compressive force that breaks the frangible connection joining the first and second members of the funnel. 
     Another aspect of the invention is embodied by a filter snapper system which includes a fluid contamination detection system comprising a funnel having first and second members joined to each other by a frangible connection in combination with the device for applying an axial compressive force to the fluid contamination detection system for breaking the frangible connection as described above. 
     Another aspect of the invention is embodied by a method for separating first and second members of a funnel joined to each other by a frangible connection using the device for applying an axial compressive force to the fluid contamination detection system for breaking the frangible connection as described above. The method comprises the steps of placing the funnel on the platform of the device while the platform is in the first position, activating the actuating mechanism, thereby causing the platform to move until a portion of the funnel engages the stop element, applying an axial compressive force to the funnel sufficient to break the frangible connection without damaging the funnel, and separating the first and second members of the funnel from each other. 
     Another aspect of the invention is embodied by a method for detecting the presence of biological contaminants in a fluid. A predetermined amount of a fluid is provided to a funnel which includes a first member defining a fluid reservoir for receiving the fluid, a second member joined to the first member by a frangible connection, and a filter, which is adapted to trap biological contaminants present in the fluid, disposed on the second member. Fluid is passed from the first member of the funnel through the filter disposed on the second member, thereby trapping biological contaminants present in the fluid on the filter. A growth medium plate is joined to the second member of the funnel in such a manner that the filter is in contact with a growth medium contained within the growth medium plate. The funnel is positioned on the platform of the device for applying axial force when the platform is in the first position. The actuating mechanism is then activated, thereby causing the platform to move from the first position toward the second position until a portion of the funnel contacts the stop element. An axial compressive force is applied to the funnel, and the force is sufficient to break the frangible connection without damaging the second member of the funnel. The first and second members of the funnel are separated from each other, and the growth medium plate is sealed by placing a cover plate on an open end of the second member of the funnel. The growth medium plate is incubated for a period of time and under conditions sufficient for biological contaminants trapped on the filter to grow; and the filter is examined after incubating to determine the presence or amount of biological contaminants on filter. 
     Another aspect of the invention is embodied by a method for detecting the presence of biological contaminants in a fluid. The method comprises the steps of providing a predetermined amount of a fluid to a funnel comprising a first member defining a fluid reservoir for receiving the fluid, a second member joined to the first member by a frangible connection, and a filter disposed on the second member and adapted to trap biological contaminants present in the fluid. The fluid is passed from the first member through the filter disposed on the second member, thereby trapping biological contaminants present in the fluid on the filter. The funnel is positioned on a mechanized device constructed and arranged to apply an axial compressive force to the funnel sufficient to break said frangible connection joining the first and second members, and mechanized device is activated, thereby causing the device to apply the axial compressive force to the funnel sufficient to break the frangible connection. After breaking the frangible connection, the first and second members of the funnel are separated from each other. Either before positioning the funnel on the mechanized device or after separating the first and second members from each other, a growth medium plate is joined to the second member of the funnel in such a manner that the filter is in contact with a growth medium contained within the growth medium plate. The second member and the growth medium plate joined thereto are incubated for a period of time and under conditions sufficient for biological contaminants trapped on the filter to grow. The filter is then examined to determine the presence or amount of biological contaminants on the filter. 
     With these and other objects, advantages and features of the invention that may become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims, and the drawings attached hereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. In the drawings, like reference numbers indicate identical or functionally similar elements. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is an exploded view, shown in side elevation, of components of a conventional filtration testing system. 
         FIG. 2  is a plan view of a filter ring of the filtration testing system of  FIG. 1 . 
         FIG. 3  is an exploded view, shown in vertical cross-section, of components of the filtration testing system of  FIG. 1 . 
         FIG. 4  is a perspective view of a filter snapper device according to an exemplary embodiment of the present invention. 
         FIG. 5  is a front elevation view of the filter snapper device according to an exemplary embodiment of the present invention in which a movable platform thereof is in a first position with a filtration testing system, shown in phantom, disposed on the movable platform. 
         FIG. 6  is a front elevation view of the filter snapper device according to an exemplary embodiment of the present invention in which the movable platform is in a second position. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. This embodiment is described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural or logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. 
       FIGS. 4-6  show a filter snapper device  100  according to an exemplary embodiment of the present invention. The filter snapper device  100  comprises a housing  110 , a movable platform  150  mounted within the housing  110 , an actuating mechanism  160  for causing movement of the platform  150 , and a valve  170  for controlling the actuating mechanism  160 . In the illustrated embodiment, the housing  110  and the valve  170  are mounted to a base plate  140 . 
     The housing  110  has a lower portion  112 , a bottom plate  118 , a back plate  120 , and a hood  122 . The lower portion  112  comprises side walls  114 ,  116 . The hood  122  comprises a front plate  124 , top plates  126 ,  128 , side walls  130 ,  132 , and a stop surface  134 . As shown in  FIGS. 5 and 6 , the distance between the side walls  130 ,  132  of the hood  122  is preferably at least as great as the distance between the side walls  114 ,  116  of the lower portion  112 . 
     In an exemplary embodiment, the housing  110  is shown with the side walls  130 ,  132  of the hood  122  separated from the side walls  114 ,  116  of the lower portion  112 . The gap between the hood  122  and the lower portion  112  allows easy access for placement or removal of the testing system  60  (shown in phantom in  FIGS. 5 and 6 ) onto or from the platform  150 . In an alternate embodiment, the side walls  130 ,  132  of the hood  122  could extend to and be continuous with the side walls  114 ,  116  of the lower portion  112 . 
     The housing  110  shown is rectangular with a triangular hood  122  as defined by top plates  126 ,  128 . Alternatively, the housing  110  could be, for example, cylindrical with a conical or hemispherical hood. 
     In the illustrated embodiment, the top plates  126 ,  128  are angled with respect to each other and are connected along upper edges thereof to form a triangular hood  122  so that the housing  110  can be placed under a vertical laminar flow hood while causing minimal disruption of the downwardly directed airflow. As shown in  FIGS. 5 and 6 , the transition from top plate  126  to top plate  128  is preferably rounded, as are the transitions between top plates  126 ,  128  and side walls  130 ,  132 , respectively. Thus, air flowing downwardly over the housing  110  will experience less disruption than if these transitions were sharply angled. 
     The platform  150  is attached to the actuating mechanism  160 , which in turn is attached to bottom plate  118  of housing  110 , and is movable relative to the housing  110  in a reciprocating manner in upward and downward directions. The platform  150  is disposed in an opposed, spaced-apart relationship with respect to the stop surface  134  of the housing  110 . The actuating mechanism  160  may comprise a pneumatic actuator, represented in  FIGS. 5 and 6  by cylinder  162  and shaft (i.e., pneumatic piston shaft)  164  extending from cylinder  162  and attached to platform  150 . The preferred pneumatic actuator for use in the present invention is a single acting, 1½ inch bore, ⅜ inch stroke Flat-1® cylinder available from Bimba Manufacturing Company of Monee, Ill. (Model No. FOS-170.375-3R). The actuator preferably generates a compressive axial force of about 40 pounds-force. 
     The valve  170  is a 3-way valve, preferably a 3-way air switch available from Mead Fluid Dynamics Inc. of Chicago, Ill. as Model No. MV-5. The valve  170  controls air flow from a pressure line  174  connected to a source of pressurized air (not shown), through the valve  170 , to line  176  extending to the pneumatic cylinder  162  coupled to the platform  150 . The source of pressurized air could be a wall-mounted conduit connected to a compressor, or it could be a self-contained pressurized air cannister, which would give the device  100  some level of portability and allow it to be operable where a source of pressurized air is not otherwise available. Bleed line  178  allows air flow from the pneumatic cylinder  162 . 
     A trigger plate  172  is pivotally connected to the valve  170  and can be operated by pressing it downwardly. In a neutral position, the pneumatic cylinder  162  is connected to bleed line  178 , and the shaft  164  is preferably spring biased into a first, downward position (see  FIG. 5 ). Pressing the trigger plate  172  causes the pneumatic cylinder  162  to be connected to the pressure line  174 , thereby pressurizing the pneumatic cylinder  162  to cause the shaft  164  to extend relative to the cylinder  162 , against the spring bias, into a second, upward position (see  FIG. 6 ). Releasing the trigger plate  172  will again connect the pneumatic cylinder  162  with the bleed line  178 , thereby de-pressurizing the pneumatic cylinder  162  and permitting the shaft  164  and the movable platform  150  to return, under the force of the spring bias, to the first position. 
     As opposed to mounting the valve  170  on base plate  140  and operating it by means of the hand-operated trigger plate  172 , cylinder  162  could be controlled by a valve placed on the floor and operated by a foot-operated trigger or plate. The valve of this embodiment is preferably a 3-way valve switch available from LINEMASTER Switch Corporation of Woodstock, Conn. (Cat. No. 3B-30A2-S). 
     Alternatively, the valve can be operated by a robot, a mechanical device, or the like. In an exemplary embodiment, the valve pneumatically actuates the movable platform  150  via pneumatic cylinder  162 . It will be appreciated by those skilled in the art that the movable platform  150  can be actuated by a hydraulic system, electric motor, solenoid, or the like. 
     As explained in more detail above, the pneumatic cylinder  162  cooperates with the valve  170 , and moves the platform  150  with respect to the stop surface  134  between the first and second positions. In the first position, the distance between the platform  150  and the stop surface  134  is greater than the axial length L of the filtration testing system  60 . (See  FIG. 3 ). This is illustrated in  FIG. 5  in which the filtration testing system  60  is placed on the platform  150  with the shaft  164  of the actuating mechanism  160  in the downward position. Although it is preferred that the entire filtration testing system  60 —including funnel  10 , growth medium plate  30 , lower cover plate  40 , and upper cover plate  50 —be placed on the platform  150 , in order to simplify the drawings, growth medium plate  30 , lower cover plate  40 , and upper cover plate  50  are not explicitly shown in  FIGS. 5 and 6 . 
     In the second position, the distance between the platform  150  and the stop surface  134  is less than the axial length L of the funnel  10  and the growth medium plate  30  joined together prior to breaking the frangible connection  28  joining the filter ring  20  to the cup  12 . This is illustrated in  FIG. 6  in which the shaft  164  of the actuating mechanism  160  is in the upward position, the funnel  10  and the growth medium plate  30  combination is in contact with both the platform  150  and the stop surface  134 , and the narrow portion  24  of the filter ring  20  is collapsed into the bottom  16  of the cup  12 . 
     It will be appreciated that separation of the filter ring  20  and the cup  12  from each other is effected by an axial compressive force generated by relative movement of the moveable platform  150  toward the stop surface  134  with the funnel  10 —with or without the growth medium plate  30 , the upper cover plate  50 , and the lower cover plate  40  joined thereto—disposed therebetween. It will be further appreciated that, in this regard, the housing  110  and the orientations of the platform  150  and the stop surface  134  play no roll in the generation of the axial force. That is, the housing could comprise any structure that will support the stop surface  134  in an opposed, spaced relationship with respect to the platform  150 , and it is not necessary to the functioning of the device  100  that the housing include, e.g., the lower portion  112  and/or hood  122 . Furthermore, the relative positions of the stop surface  134  and the platform  150  could be switched, with a moveable platform disposed above a stop surface. In such an arrangement, a dedicated stop surface could be omitted, and the platform could be supported a suitable distance above the base plate  140 , with the base plate  140  functioning as a stop surface. Moreover, in such an arrangement, the filtration testing system  60  would be placed on the stop surface and the platform would be actuated in a downward motion until it contacts and applies the required axial force to the funnel. Alternatively, the filtration testing system  60  could be compressed between two spaced-apart surfaces that are each movable with respect to the other. As a still further alternative, the stop surface and the moveable platform could both be supported—e.g., by the base plate  140 —in a horizontally spaced-apart relation. Such an arrangement would preferably include means for cradling the filtration funnel system  60  to keep it from rolling before being compressed. 
     Having described the structural and functional elements of the filter snapper device  100 , a fluid contamination detection procedure employing the device  100  will be described. 
     After water has been passed through the filter  26 , e.g., using the suction mechanism described above, of the filter ring  20 , the funnel  10  is joined to the growth medium plate  30  such that the growth medium  32  is in contact with the filter  26 . The upper cover plate  50  and the lower cover plate  40  are placed on the funnel  10  and the growth medium plate  30 , respectively, and the funnel  10 , with the growth medium plate  30  joined thereto, is then placed on and supported by the platform  150 , which is in its first position, as shown in  FIG. 5  Alternatively, the funnel  10  may be placed directly on the platform  150  prior to attaching the growth medium plate  30  to the filter ring  20 . The funnel  10  is positioned on the platform  150  by a positioning fence  152  mounted to or formed on the platform  150 . In the embodiment shown, positioning fence  152  is a curved, upstanding wall having a curvature generally conforming to that of the filter ring  20 . The platform  150  is actuated by the valve  170  (via trigger plate  172 ), which supplies air under pressure into the pneumatic cylinder  162 , thereby extending the shaft  164  and moving the platform  150  and the funnel  10  and growth medium plate  30  combination upward from the first position. 
     As illustrated in  FIG. 6 , the platform  150  continues to move the funnel  10  and associated growth medium plate  30  upward until a portion of the filtration testing system  60 , e.g., the upper cover plate  50 , engages or abuts against the stop surface  134 . As the platform  150  continues to move upward toward the second position, an axial compressive force is applied to the testing system  60 . The axial compressive force is sufficient to break the frangible connection  28  joining the filter ring  20  and the cup  12 , thereby collapsing the narrow portion  24  of the filter ring into the bottom end  16  of the cup  12  (see  FIG. 6 ). The axial compressive force is not, however, so great that the filter ring  20  or the growth medium plate  30  is damaged (e.g., cracked, warped, crushed, bent, etc.) in the process. 
     When the valve  170  is released (via trigger plate  172 ), air is permitted to escape the pneumatic cylinder  162  through the bleed line  178  and, consequently, the shaft  164  retracts into the cylinder  162  and the platform  150  returns to the first position so that the cup  12  and filter ring  20  components of the funnel  10  can be removed from the platform  150 . The top cover plate  50  is placed on the open, upper end of the filter ring  20 . The cup  12  can be disposed of in any suitable disposal means. 
     The growth medium plate  30  and associated filter ring  20  are then exposed to conditions sufficient to promote the biological growth of biological contaminants (e.g., bacteria or fungi) that may be present on the filter  26 . For example, the growth medium plate  30  and associated filter ring  20  may be placed in an incubator at 37° C. for a set period of time or times and examined at the end of each period of time for changes, such as the appearance of colony forming units (“CFU”). If, based on this examination, there is an indication that the bioburden (i.e., the number of CFU) of the fluid sample is too high, then the source of the contaminated fluid can be disposed of before it is used in sterile laboratory or manufacturing procedures. 
     To destroy any biological contaminants that may have been deposited on the filter snapper device  100  during the procedure described above, the filter snapper device  100  is preferably washed at the completion of the procedure with a solution made up of 9 parts water and 1 part bleach, followed by a wash with 70% alcohol. Because of the corrosive nature of the bleach solution, the filter snapper device  100  is preferably made of electro polished  316  stainless steel. To facilitate cleaning, all housing joints are welded. To further facilitate cleaning, housing  110  is separated from base plate  140  by spacer elements  142  disposed between the base plate  140  and the bottom plate  118  of the housing  110 . Spacer elements  142  are preferably formed from Delrin® acetyl resin. Similarly, the actuating mechanism  160  is separated from the bottom of the housing  110  by means of spacers  166 —preferably formed from stainless steel—disposed between the bottom plate  118  and the actuating mechanism  160 . Finally, feet  144 —preferably formed from a non-skid elastomer—are disposed on the bottom of the base plate  140  to provide a separation between the base plate  140  and a surface upon which the filter snapper device  100  may be supported. 
     The foregoing has described the principles, embodiments, and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments described above, as they should be regarded as being illustrative and not as restrictive. It should be appreciated that variations may be made in those embodiments by those skilled in the art without departing from the scope of the present invention. 
     Modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described herein.