Abstract:
A sequential air sampler is provided having a rotatable carrier adapted to support filter cassettes received from a supply magazine at a load station, transport them to a sampling station where gas flow is directed through that cassette, and then be transported to an unload station to be received by a storage magazine. A Geneva driver operated by a single motor provides intermittent rotation to the carrier between fixed positions. A cam rotates in concert with the Geneva driver so that a follower in reciprocating motion pushes up and then pulls down a pair of plungers for simultaneous cassette loading and unloading whenever the carrier is at one of its fixed positions. Magazines have magnetically actuated stoppers to keep the stack of cassettes in place until released. Magazines may also have a retaining lid with a position-adjustable piston to secure cassettes for transport.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to a method and apparatus for sequential air sampling devices for collecting particulate matters and chemical species in the air and other gases. More specifically, this present invention relates to sample filter cassette magazines and automatic filter cassette transfer methods and apparatus. 
       BACKGROUND ART 
       [0002]    In order to protect public health, the United States Environment Protection Agency (EPA) has developed air sampling protocols, including a standardized air sampling system. Under such EPA protocols, in order to collect a series of daily samples a site operator needs to be at an air monitoring site that is equipped with a single event air sampler every day so as to retrieve the sample-loaded filter and install a new filter. 
         [0003]    To minimize inconvenience, many monitoring sites have accommodated sequential air samplers. Currently most sequential samplers use a linear transfer movement mechanism to move successive filter cassettes from a clean filter cassette magazine station to a sampling station and finally to a storage magazine station. For this sequential movement, a filter cassette carrier moves forward and backward by precisely controlled actuators. 
         [0004]    Some systems use several electric linear actuators, stepper motors with belt, or pneumatic actuators to achieve this linear movement. Therefore, these systems often require an accurate control system to correctly position the carrier. 
         [0005]    One broadly available EPA designated sequential air sampler uses a pneumatic actuator and solenoid actuators to move filter cassette from position to position. To activate the pneumatic actuators, lots of complex pressurized air tubes are linked with valves and other control systems. Therefore, the biggest drawback of this system is maintaining leak-free complex pneumatic system. If a malfunction occurs, it would require a lot of time and effort to find the source(s) of the malfunction. 
         [0006]    U.S. Pat. No. 5,898,114 to Basch et al. uses a multi-filter cassette carrier for a sequential air sampler. In U.S. Pat. No. 6,138,521 to Basch et al., the cassette magazines are installed beneath the transfer mechanism. Therefore, it requires a filter cassette lifting mechanism at the supply station and also requires a drop preventing aperture at the storage magazine station. This system uses a pneumatic actuator and couple of solenoid actuators to move filter cassette from position to position, and therefore require precise pneumatic and sequential control and frequent maintenance. 
         [0007]    The system in U.S. Pat. No. 8,192,516 to Yoon et al. uses two step motors, one for moving filter cassettes from station to station and another for moving the filter cassette vertical position. This system also requires precise position control to locate the filter cassette at right positions. 
         [0008]    U.S. Pat. No. 6,167,767 to Mengel et al. uses a Geneva drive for indexing sampler position. 
       SUMMARY DISCLOSURE 
       [0009]    A sequential air sampler is provided which has an automatic rotating filter cassette transfer mechanism with magnetic force driven sample filter cassette magazines to hold multi-stacking filter cassettes in one magazine. All mechanisms of the sequential air sampler move the filter cassette from place to place by use of a Geneva drive, roller follower and cam, lever systems, etc. In particular, the filter cassette moving mechanism simultaneously moves an unloaded clean filter from its supply magazine to the sampling station, and a sample-loaded used filter cassette from the sampling station to a storage magazine station by means of a Geneva driver. A roller-cam mechanism, which rotates together with the Geneva driver, simultaneously pushes up both sampling station and storage magazine station plungers. After the sampling process is finished, the same roller-cam mechanism pulls down both plungers to the lower position. All of these sequential movements operate by a single gear-motor. 
         [0010]    The filter cassette magazine has a stopper which prevents the stack of filter cassettes from dropping out of the magazine until a filter cassette from the stack is specifically released onto the filter cassette carrier, e.g. by using magnets to move a stopper. In that case, the stopper, which is connected at the end of a rod spring, moves outward by magnetic force to release filter cassette(s) at the supply magazine station from the filter cassette magazine onto the carrier. At the storage magazine station, the filter cassette stopper holds sample loaded filter cassettes stacked in safe position. 
         [0011]    A reflectance sensor may be used to detect the presence of filter cassettes in the system. The sequential sir sampler can easily be adapted to accommodate taller filter cassettes (or multi-filter loaded filter cassettes) by replacing spacers between the Geneva drive plates with taller spacers. 
       Advantages 
       [0012]    The present invention uses only one motion power source (gear motor) to move filter cassettes from station to station, and it all happens simultaneously. Both the sealing of a new filter from the filter cassette supply magazine for sampling at the sampling station and the storing of the used filter cassette in a filter cassette storage magazine occur simultaneously after filter cassette movement by the same gear motor. The Geneva drive mechanism&#39;s intermittent or stepping rotation allows precise positioning of filter cassettes, and associated cam wheels have adequate dwelling period, so that the system doesn&#39;t require any accurate electronic positioning system(s). 
         [0013]    The filter cassette magazines have minimal parts (and no moving parts) compared to contacting neighborhood part(s)-like systems (cf. U.S. Pat. Nos. 8,192,516 and 6,138,521). A filter cassette stopper in the filter cassette magazine has adequate free space around the stopper, which keeps it free of jamming. Moreover, a reflectance sensor may be used to sense the presence of a filter cassette and prevent any malfunction. But, if necessary (such as during a sudden power outrage or a malfunction situation), an operator can still easily recover a filter cassette manually simply by lifting a top station holding plate of the transport system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is top perspective view of a sequential air sampler in accordance with the present invention. 
           [0015]      FIG. 2  is bottom perspective view of sequential air sampler in accordance with the present invention. 
           [0016]      FIG. 3  is an expended perspective view of sequential air sampler in accordance with the present invention. 
           [0017]      FIGS. 4, 5 and 6A  are partial expended perspective views of filter cassette moving mechanism with three different positions. 
           [0018]      FIG. 6B  shows open hole shape in the filter cassette carrier. 
           [0019]      FIG. 7  shows roller follower and cam elevational view which change rotational movement to linear movement to drive plungers up and down. 
           [0020]      FIG. 8  is a bottom perspective view of filter cassette magazine. 
           [0021]      FIG. 9  is a cross-cut view of expended filter cassette magazine. 
           [0022]      FIG. 10  shows illustrative embodiment of filter cassette stopper and filter cassette magazine supply station  20  mounting index  21 . 
           [0023]      FIG. 11  shows illustrative embodiment of operation of the filter cassette stopper part. 
           [0024]      FIG. 12  shows illustrative embodiment of filter cassette drop induced by magnetic reaction. 
           [0025]      FIG. 13 through 16  show e filter cassette storage processes. 
           [0026]      FIG. 17  shows perspective view of retaining lid  300 . 
           [0027]      FIG. 18  shows illustrative embodiment of retaining lid  300  with cross cut view of filter cassette magazine  1 . 
           [0028]      FIG. 19  is an expended perspective view of retaining lid  300 . 
           [0029]      FIG. 20  shows illustrative embodiment of winding mechanism of retaining lid  300 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  shows a sequential air sampler having a filter cassette supply station  20 , a sampling station  30 , and a filter cassette storage station  10 . All these three stations are sitting on top of a station holding plate  33 . The center of each station is located the same distance from a Geneva drive output shaft  54 . A supply station filter cassette magazine  1  is sitting at the supply station  20  inside of a supply station mounting index  21 . The supply station mounting index  21  has four magnets  22  at four equally spaced locations around its radial direction. 
         [0031]    The magnets  22  pull filter cassette stoppers  15  (seen in  FIG. 10 ) in an outward direction and let a clean filter cassette F 1  drop into a hole  63  (seen in  FIG. 3 ) of an intermittently rotating filter cassette carrier  51 . 
         [0032]    A storage station filter cassette magazine  1  is sitting at the storage station  10  inside of a storage station mounting index  26 . The inside mounting index  26  has four ball plungers  27  (seen in  FIG. 3 ) on top of the station holding plate  33 . The station holding plate  33  is secured with four fasteners  32  on top of four spacers  52 . 
         [0033]    Referring to  FIG. 2 , from a bottom perspective it can be seen that a gear motor  157  rotates a Geneva drive input wheel  56  with outer cam  115  and inner cam  116 . The outer cam  115  and inner cam  116  move a roller follower  109  back and forward along the guide block  110 . Lever systems  113  and  120 , connected at the end of roller follower  109 , turn the horizontal movement of the roller follower  109  and  124  (see  FIG. 3 ) into vertical movement of a sampling station plunger  103  and a storage station plunger  118 . 
         [0034]      FIG. 3  shows an exploded perspective view of the sequential air sampler and in particular shows how each of the parts are connected to each other. A plunger moving mechanism  100  includes mainly a gear motor  157 , cams  115 ,  116 , a roller follower  109 , and lever systems  113 ,  120 , as well as the plungers  102 ,  118  themselves and other related supporting parts. All parts of the plunger moving mechanism  100  are attached underneath of the lower plate  58 . The shaft of the gear motor  157  is directly connected with the Geneva drive&#39;s input shaft  153 . Shaft  153  rotates the Geneva drive input wheel  56 , as well as the inner-cam  116  and outer-cam  115 . Inner-cam  116  and outer-cam  115  drive the roller follower  109  in a reciprocating motion back and forth horizontally along a guide block  110 . The other side of the roller follower  109  is connected with a sampling station  30  lever system  113 . The purpose of the lever system  113  is to transfer horizontal movement of roller follower  119  into vertical movement of a sampling station plunger  103 . The effort distance between the pins  107  and  108  is longer than the resistance distance between the pins  107  and  111 . Lever system  113  reduces roller follower  109  travel distance to sampling station plunger  103  travel distance, which is the same as the ratio of resistance distance to effort distance. 
         [0035]    A sliding rod  124  is directly connected to the roller follower  109  by a connecting plate  125  and slides the same distance as the roller follower  109 . Sliding rod  124  moves the storage station plunger  118  up and down by means of the lever system  120 . Lever system  120  amplifies the roller follower travel distance  136  as the ratio of effect and resistance distance of lever system  120 . 
         [0036]    The Geneva drive filter cassette transfer mechanism  50  includes a Geneva drive input wheel  56 , a locking wheel  55 , a Geneva drive output wheel  53 , and a filter cassette carrier  51 . This mechanism  50  converts continuous rotary motion of Geneva drive input wheel  56  into intermittent or stepped rotary motion of Geneva drive output wheel  53  between a set of four fixed rotational positions of the carrier that are equally spaced 90 degrees apart. The Geneva drive input wheel  56  and locking wheel  55  are mechanically attached along with a shaft  153 . One rotation of Geneva drive input wheel  56  makes one-fourth rotation of Geneva drive output wheel  53 . The filter cassette carrier  51  also rotates one-fourth of a revolution, along with the Geneva drive output wheel  53 . The filter cassette carrier  51  has four holes  63  at equal 90 degree angle spacing. 
         [0037]    The Geneva drive filter cassette drive mechanism may be secured by two plates  33  and  58  with four fasteners  32  and with four spacers  52 . The top plate  33  accommodates the supply magazine station  20 , the sampling station  30 , and the storage magazine station  10 . 
         [0038]      FIGS. 4, 5 and 6  show the operational steps of the sequential air sampler. In the operation of Geneva drive filter cassette transfer mechanism  50 , when the Geneva drive input wheel  56  is rotated by a gear motor  157  (see  FIG. 3 ) in a clockwise direction, a ball bearing  57  is received in one of the radial slots  70  of the Geneva drive output wheel  53  and engages the side wall of such slot to rotate the Geneva drive output wheel  53  in a counterclockwise direction. When the Geneva drive input wheel  56  rotates a first 90 degree angle with uniform angular speed, the Geneva drive output wheel  53  also rotates a 90 degree angle in the opposite direction with differential angular velocity. Simultaneously, the filter cassette carrier  51  moves a new filter cassette F 1  in the supply magazine station  20  (see  FIG. 3 ) to the sampling station (see  FIG. 3 ). When the new filter cassette F 1  is in the sampling station position, another new filter cassette at the supply magazine station  20  is dropping from the filter cassette magazine  1  into the next filter cassette carrier hole  63  and then waits until the next turn of the carrier. The outer cam  115  and inner cam  116  also rotate with the Geneva drive input wheel  56  simultaneously as well as filter cassette carrier  5  (see  FIG. 5 ). During the first 90 degree rotation  133  of inner-cam  116  and outer-cam  115 , the roller follower follows cam profile line, “dwelling period”  131  (see  FIG. 7 ) and stay without linear movement. 
         [0039]    After ball bearing  57  slips out from the radial slot  70 , the peripheral surface  58  of locking wheel  55  engages with concave surface of Geneva drive output wheel  53  and secures rotational movement until ball bearing  57  slips in next radial slot  70  or 270 degree rotation (see  FIG. 6A ). After a 90 degree turn of the Geneva drive input wheel, the guide bearing  112  slides along with outer cam profile line  131  and moves the roller follower slides toward to rotating center of cams  115 ,  116  until next 130 degree of rotation (see  FIG. 7 ). At this potion, the roller follower  109  moves lever systems  113 ,  120  and pushes up sampling station plunger  103  and storage station plunger  118  to its own highest position. 
         [0040]      FIG. 6B  shows four open holes  63  in the filter cassette carrier  51  forming receptacles for the filter cassettes. The radius  60  is same as a filter cassette and the adjusted radius  62  is larger than filter cassette radius. The radius  62  is big enough to prevent any squeezing of filter cassette when it is dropped from the filter cassette magazine  1 . The radius  60  is located right side or back side of filter cassette  51  rotation direction. Filter cassette is moving against surface having radius  60  to position same as the center of sampling station  30  and storage station  10 . 
         [0041]    With reference to  FIG. 7 , which shows an illustrative embodiment of the roller slide  109  and operation of the cams&#39;  115 ,  116 , there is seen to be two cam plates, an inner cam  116  and an outer cam  115 . A guide bearing  112  attached at one end side of the roller follower slides along with cam-profile  131 ,  132  and converts rotation movement of cams  115 ,  116  to linear motion of the roller follower  109 . Cams  115  and  116  have three cam-profile sections  133 ,  134  and  135 . Whenever the guide bearing  112  is in a dwell period  133 , the roller follower will stay still. At this period of rotation, Geneva drive input wheel  56  rotates the filter cassette carrier by 90 degrees and brings a new filter cassette F 1  from the supply magazine station  20  to the sampling station  30  (see  FIG. 3 ). After another 90 degree rotation, the roller follower  109  slides toward the cams  115  and  116  until next 130 degree of cam rotation  134 . The next 10 degree angle  136  is another dwell period. The roller follower  109  moves a sampling station lever system  113  and sliding rod  124  connected directly with roller follower  109  by connecting plate  125 . The sliding rod  124  moves a storage station plunger  118  up and down. When a sensor  162  indicates slot  127 , it expresses that two plungers  103 ,  118  are in the lowest position and a ball bearing starts engaging with radial slot  70 . When a sensor  160  indicates slot  127 , it expresses that the two plungers  103 ,  118  are in their highest position and ready for an air sampling process. 
         [0042]    Referring to  FIGS. 8 and 9 , as seen from respective bottom perspective and exploded cross-sectional perspective views of the filter cassette magazine  1 , the filter cassette magazine includes a lid  11 , a magazine tube  12 , and a tube holder  13 . The magazine tube  12  is coupled with the tube holder  13  and secured with four set screws  17 . The tube holder  13  has two mounting slots  24  to engage into a supply mounting index  21  and a storage mounting index  26 . The tube holder  13  also has two settle groves  28  for positioning a filter cassette magazine when engaged with storage side mounting index  26  (see  FIG. 8 ). The magazine tube  12  has four rounded slot holes  18  at the bottom with equal space. The slot hole  18  accommodates a filter cassette stopper  15  (see  FIG. 9 ). Each tube holder accommodates four filter cassette stoppers  15 . The filter cassette stopper  15  is attached at the end of rod spring  14  with magnet  16 . The bended part of other end of rod spring  14  is goes into a hole  19  and a recessed narrow slot  18 - 1  secures the rod spring  14  from swinging in a peripheral direction. The portion of the filter cassette stopper extending inside of the magazine tube  12  has two different shapes: a bottom round part and a top flat part. 
         [0043]      FIGS. 10, 11 and 12  illustrate the reaction between magnets  22  installed around supply station  20  mounting index  21  and filter cassette stopper  15 . To mount the filter cassette magazine  1 , first, align the mounting slot with a mounting pin  23 , insert it into the mounting index  21 , and then rotate it in a clockwise or counter-clockwise direction until the magnet  22  and filter stopper magnet  16  are firmly engaged. As soon as magnets  22  pull stopper magnet  16 , the filter cassette stopper moves in an outward direction and releases filter cassette(s) into the empty filter cassette carrier hole  63 . 
         [0044]      FIG. 13  through  FIG. 16  show the filter cassette storage processes. The storage station  20  mounting index  21  doesn&#39;t have a pulling magnet. Therefore, the filter cassette stopper  15  is in a free position. After sampled filter F 1  is carried into magazine storage station  20 , storage station plunger  118  moves upward by lever system  120  (see  FIG. 13 ). As the storage plunger  118  moves upwardly with filter cassette F 3 , filter cassette F 3  pushes four filter cassette stoppers  15  outwardly in a radial direction (see  FIG. 14 ). After the filter cassette F 3  passes the filter cassette stopper  15  position, four filter cassette stoppers return to their free position (see  FIG. 16 ). When the storage plunger  118  moves back downward, the four filter cassette stopper  15  hold filter cassette(s) F 3 , which is stored in the storage station  10  magazine  1 . A reflectance sensor  170  senses the presence of the filter cassette F 3 . The detection distance limit of the reflectance sensor  170  is about one and half of the filter cassette thickness. If the filter cassette is secured by the filter cassette stoppers, reflectance sensor  170  treats there is no filter cassette F 3  remaining in the storage station carrier hole  63  and allows gear motor to rotate the filter cassette carrier  51 . 
         [0045]    The term “ribbon” is here used to designate a piece of concave-convex form of thin flexible metal or plastic ribbon (like tape measure metal tape). 
         [0046]      FIG. 17  shows perspective view of retaining lid  300 . A retaining lid  300  is used to cover bottom of the filter cassette magazine  1  and to secure new and used stack of filter cassettes F 1 s or F 3 s from shaking whenever the filter cassette magazine  1  is transferred place to place. A piston  301  is attached on top of ribbons  304  and  305  moves up and down with ribbons  304  and  305 . Ribbons  304  and  305  contact face to face of the convex side to form a structural column. 
         [0047]      FIG. 18  shows how the retaining lid  300  secures filter cassettes F 1 s or F 3 s from shaking inside the filter cassette magazine  1  whenever filter cassettes F 1 s or F 3 s do not fully fill the inside of the filter cassette magazine  1 . By turning a knob  315  counter-clockwise, a piston  301  moves upward by two ribbons  304 ,  305 . Ribbons  304  and  305  are wound on their own bobbin  312  and  311 , respectively. Bobbin  311  and  312  are connected by gears  313  and  314 . Therefore, bobbins  311  and  312  turn in opposite directions. 
         [0048]    The retaining lid  300  is attached from the bottom of the filter cassette magazine and secured by hooks  306  and  307 . 
         [0049]      FIG. 19  shows an exploded perspective view of the retaining lid  300 . Piston  301  is connected with two ribbons with pin  302 . Two ribbons  304 ,  305  slide through slot hole  321  in the middle of a sealing plate  308 . The sealing plate  308  closes the bottom of the filter cassette magazine  1  and is secured by two hooks  306  and  307 . A holding block  309  holds the bobbins  311 ,  312  and two gears  313 ,  314 . A cover block  310  also supports bobbins  311 ,  312 . Knob  315  is connected directly with bobbin  311 . 
         [0050]      FIG. 20  shows a partial perspective view of winding mechanism. By rotating knob  315 , bobbin  311  and gear  313  rotate in the same direction. Bobbin  312  rotates in the opposite direction simultaneously with gear  314 . Formed ribbons  304  and  305  are secured with bobbins  312  and  311  respectively by screws  317  on the flat surface  319 ,  320  of bobbin  311  and  312  respectively.