Abstract:
An apparatus and corresponding method for automatically changing out a filter cartridge in a continuous air monitor. The apparatus includes: a first container sized to hold filter cartridge replacements; a second container sized to hold used filter cartridges; a transport insert connectively attached to the first and second containers; a shuttle block, sized to hold the filter cartridges that is located within the transport insert; a transport driver mechanism means used to supply a motive force to move the shuttle block within the transport insert; and, a control means for operating the transport driver mechanism.

Description:
STATEMENT REGARDING FEDERAL RIGHTS 
   This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 

   FIELD OF THE INVENTION 
   The present invention relates generally to continuous air monitors, and, more particularly, to an apparatus that provides for automated filter change-out in a continuous air monitor. 
   BACKGROUND OF THE INVENTION 
   The Canberra Instrument Company, Inc. currently produces the Alpha Sentry CAM, and the Canberra Aquila Technologies Group currently produces the alpha-ECAM for the radiological air monitoring community. The present invention is an apparatus that provides for automated filter change in continuous air monitors (CAMs); including, the Alpha Sentry CAM and the Alpha Environmental Continuous Air Monitor (ECAM) utilizing the Quick Change Filter Cartridge (QCFC) filter holder. 
   The fact that the Alpha Sentry CAM and the ECAM use the Quick Change Filter Cartridge for handling filters created a unique opportunity to design a simple retrofit filter changing apparatus for these CAMs. The QCFC not only holds and positions the filter in the CAM head, it also provides the porous filter backing disk, so once the filter is inserted into the cartridge and the cap pressed on, all handling, positioning, or sealing requirements are taken into account except for insertion of the cartridge into the CAM head. 
   The user is enabled to pre-load a number of filter cartridges with pre-cut filter paper and insert them in the subject invention. Following initiation of the filter change process, all subsequent filter changes are executed automatically under the control of the embedded controller or PC in the CAM or ECAM. The user can initiate filter change just as is currently provided for in the CAM/ECAM user interface program, or by the detection of a condition such as unacceptably low flow using the built-in flow meter signal, at which time a filter change sequence would begin. In either circumstance, the actual process of used filter cartridge extraction and storage, and insertion of a fresh filter, would be carried out by the present invention without user handling. Thus, the present invention makes possible autonomous filter change outs at remote sites using the built-in network communication capability of the monitor. 
   Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
   SUMMARY OF THE INVENTION 
   In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes an apparatus and corresponding method for automatically changing out a filter cartridge in a continuous air monitor. The apparatus includes: a first container sized to hold filter cartridge replacements; a second container sized to hold used filter cartridges; a transport insert connectively attached to the first and second containers; a shuttle block, sized to hold the filter cartridges that is located within the transport insert; a transport driver mechanism means used to supply a motive force to move the shuttle block within the transport insert; and, a control means for operating the transport driver mechanism. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
       FIG. 1  is a pictorial illustration of one embodiment of a CAM filter cartridge that the present invention can be used to replace automatically. 
       FIG. 2  is a pictorial illustration of one embodiment of a feed container used to store replacement CAM filter cartridges. 
       FIG. 3   a  is a pictorial illustration of a top loading feed container embodiment. 
       FIG. 3   b  is a pictorial illustration of a bottom loading feed container embodiment. 
       FIG. 4  is a pictorial illustration of a one-piece bottom loading feed container. 
       FIG. 5  is a pictorial illustration of an embodiment of a shuttle block. 
       FIGS. 6   a  and  6   b  are pictorial illustrations of an embodiment of a latching mechanism. 
       FIG. 7  is a pictorial illustration of a transport insert. 
       FIG. 8  is a flow chart describing the method of removing a spent cartridge and replacing it with a fresh cartridge. 
       FIG. 9  is a pictorial illustration of another embodiment of a feed container. 
       FIGS. 10   a  and  10   b  are pictorial illustrations of another embodiment of a shuttle block and feed container. 
   

   DETAILED DESCRIPTION 
   The present invention was created to meet an expressed need for automated filter changing capability, where remote environmental settings or adverse conditions may make filter changing a costly and time-consuming process. The present invention makes it possible to reduce the support time requirement in a monitored facility or environmental monitored network by allowing a week&#39;s or a month&#39;s supply of filters (depending on dust loading conditions) to be set up at one time. 
     FIG. 1  shows one embodiment of a CAM filter cartridge that is used for collecting radiological air samples. In this embodiment, a filter cartridge  10  is round with beveled edges that allow proper centering under a detector within a CAM during mechanical handling. However, any shape configuration may be used for filter cartridge  10 , so long as the shape does not interfere with smooth handling during mechanical operations. Generally, air monitor filters used in real-time monitoring applications exhibit a circular geometry, ranging in size from 1″ to 8″. 
     FIG. 2  shows one embodiment of feed container  20 , which is sized appropriately to hold replacement filter cartridges  10 . Replacement filter cartridges  10  are stacked within feed container  20 , where the vertical dimension of feed container  20  is the only limiting factor on the number of cartridges that may be stored. Also, shown is latch  45 , which separates one filter cartridge  10  from the stack of cartridges at a time for transport into an attached CAM. 
   Referring now to  FIG. 3   a , feed container  20  is connectively attached in a gravity feed position to transport insert  50 . Transport insert  50  is an enclosed rectangular tray (metal or plastic) sized to fit into and connectively attach to CAM  5 . Transport insert  50  serves as a guide element for cartridge shuttle block  40 , located within insert  50 , and provides a moving platform chassis on which the operations of loading, shuttling, and discharging filter cartridges  10  occurs. Discharge container  30  is also connectively attached to transport insert  50 , and serves the function of holding replaced filter cartridges  10  until collected by personnel. 
     FIG. 3   b  shows another embodiment of the present invention, where feed container  20  is placed below transport insert  50  and spring  25  is used to supply the upward motive force to load new replacement cartridges into cartridge shuttle block  40 . 
   Feed container  20  is used for loading and staging of replacement filter cartridges  10  and discharge container  30  is used for accumulation of discharged filter cartridges  10 . Both feed container  20  and discharge container  30  are of suitable diameter to accept filter cartridges for used in automated filter changes. Note that in an alternative embodiment, feed container  20  and discharge container  30  may be manufactured as one piece, as shown in  FIG. 4 . 
     FIG. 5  shows an embodiment of shuttle block  40  used to capture and transfer used and replacement cartridges  10 . This embodiment would be used for replacement cartridges  10  that exhibit a circular design. Other embodiments may be fashioned for other cartridge  10  geometries. Shuttle block  40  may comprise any suitable material (i.e., metal or plastic) sized to fit within transport insert  50 , with a defined central opening to accept and capture filter cartridges  10 . 
     FIG. 6   a  shows an embodiment of a latching mechanism that functions to capture and stage cartridges  10  in feed container  20  during the loading process, such that only one cartridge  10  is inserted into radiation monitor  5  at a time. Latch piece  45  is mounted on block piece  44  to facilitate a spring-loaded approach to insertion and recovery of latch piece  45  from between cartridges in feed container  20 . In this embodiment, latch  45  includes two finger projections  41  that slide between successive cartridges  10  in feed container  20  and hold non-selected stack of cartridges  10  from moving, while the selected cartridge  10  is loaded into shuttle block  40  into CAM  5 . 
   Referring now to  FIG. 6   b , backpiece  49  is secured to transport insert  50 , and springs  48  push latch piece  45  towards feed container  20  as shuttle block  40  moves towards CAM  5 . When shuttle block  40  is moving back towards discharge container  30 , pins  42  that protrude down through holes  46  into the interior of transport insert  50 , are engaged by formed pieces  39  (reference  FIG. 5 ) on the back of shuttle block  40 . Thus, as shuttle block  40  continues movement towards discharge container  30 , latch piece  45  is pushed away from feed container  20 , allowing the stack of replacement cartridges to moved down by the pull of gravity, and thereby readying another cartridge  10  for replacement use. 
     FIG. 7  shows an embodiment of transport insert  50 . As previously stated, shuttle block  40  (not shown) is located within transport insert  50  and is coupled to transport driver mechanism means  60 , which may be, as in this embodiment, motor  62  with pulley  64  and belt  66 . Other motive means may be used as driver mechanism, to include a screw drive driven by a stepper motor or digital pulse control of a small motor or servomotor. Motor  60  is typically controlled using microprocessor  65 , or other suitable electrical/mechanical control means known to those skilled in the art, to achieve proper positioning of shuttle block  40  during operation. Slots  52  allow pins  42  (reference  FIG. 6   a/b ) to extend down to make contact with shuttle block  40 . 
     FIG. 8  is a flow chart describing the method of removing a spent cartridge and replacing it with a fresh cartridge: 
   In Step  100 , a computer program interrupt generated by a flow sensor signal, programmed elapsed time signal, or user command signals microprocessor  65  to initiate a filter change out operation. The interrupt is usually based on a flow sensor measurement of reduced volumetric flow below a user-defined low-flow level, but also is frequently initiated by a user-initiated filter change command. 
   In Step  110 , microprocessor  65  initiates disengagement of used filter cartridge  10  from CAM  5 , typically this is performed by removing a vacuum condition within CAM  5  that holds cartridge  10  in place. 
   In Step  120  a signal from controlling microprocessor  65  initiates movement of shuttle block  40  that contains used/spent filter cartridge  10  from CAM  5  along transport insert  50  until shuttle block  40  reaches discharge container  30 . During this movement, shuttle block  40 , engages pins  42 , and pushes latch piece  45  away from feed container  20 , allowing the stack of replacement cartridges to move down. 
   In Step  130 , once centered over discharge container  30 , used filter cartridge  10  simply drops into discharge container  30  from shuffle block  40 . 
   In Step  140 , a signal is sent to the microprocessor to reverse movement of shuttle block  40 . The signal may be generated by any means known to those skilled in the art, for example from a limit switch, optical rotation encoder, or a computer program that logs the progress of shuttle block  40 . 
   In Step  150 , shuttle block  40  moves back towards CAM  5 , and springs  48  provide the motive force to slide latch piece  45  back to, and insert in, feed container  20 , thereby isolating a replacement cartridge from the stack of replacement cartridges. 
   In Step  160  the isolated replacement cartridge moves into shuttle block, either by gravity feed or some other motive force like a spring. 
   In Step  170  shuttle block  40  moves along transport insert  50  and into CAM  5 , providing a fresh filter cartridge for use. Note that an infra-red LED beam interrupt system could be used to detect filter movement out of the stack in the cartridge feed tube. The interrupt system would indicate that the stack supply has been exhausted (providing a “stack empty” signal), and in addition, it would take care of the situation where a cartridge got stuck in the process of loading, in which case an “service error” signal would be generated. 
   Finally, in Step  180 , microprocessor  65  initiates engagement of replacement filter cartridge  10 , typically by creating a vacuum condition within CAM  5 . 
     FIGS. 9 ,  10   a , and  10   b  show another embodiment for selecting a replacement cartridge from a stack of fresh cartridges. In this embodiment, spring loaded latch  75 , located on shuffle block  70  swivels, depending on the direction of motion of shuttle block  70 . As shuttle block  70  moves towards feed container  60 , latch  75  is in the upright position shown in both  FIGS. 9 and 10   b . As latch  75  moves into and through feed container  60  towards CAM  5 , latch  75  pushes a replacement cartridge out of feed container  60  and over opening  55 , where the replacement cartridge drops down into shuttle block  70 . Shuttle block  70  then continues on, as in the first embodiment, into CAM  5 . Feed container  60  includes lip feature  62  that holds cartridges  10  in feed container  60 , serving the same function as latch piece  45  ( FIG. 6   a ) in the previous embodiment. Notch  64  allows the passage of latch  75  through feed container  60 , while latch  75  is in the upright position. 
   When moving a used/spent cartridge towards discharge container  30 , shuttle block  70  must move under feed container  60 . In order to perform this operations, latch  75  is designed with a curved surface that contacts the replacement stack of cartridges  10  in feed container  60  and swivels towards shuttle block  70  and below feed container  60 , in order to allow shuttle block  70  to move freely below feed container  60 . Once latch  75  exits from beneath feed container  60 , spring  77  provides the motive force to push latch  75  back into the upright position. 
   The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. 
   The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.