Abstract:
An automated filter changing system comprises a rotatable filter dispensing assembly and a filter clamping assembly. The filter dispensing device receives filter storage magazines in which a plurality of filters are initially stored in the form of connected stacks. The filter dispensing assembly includes a filter separating device having a stationary portion. The filter separating device separates one or more stacks of filters into discrete filter units, such that individual filters are transported sequentially from the filter dispensing device. The filter clamping assembly operates in conjunction with the filter dispensing device to receive one or more individual filter units dispensed therefrom, and provides one or more coupling sites which can fluidly communicate with one or more fluid lines. The filter clamping device couples unused filters to fittings associated with the fluid lines by applying an evenly distributed force to the filters.

Description:
TECHNICAL FIELD  
         [0001]    The present invention generally relates to the filtration of media or fluids in connection with a fluid preparation, sampling, delivery, and/or testing process. More particularly, the present invention relates to the automated inline replacement or “changing out” of used or spent filters with unused or new filters.  
         BACKGROUND ART  
         [0002]    Filter elements of varying types are utilized to filter media or fluids flowing through a fluid line or circuit which forms a part of a fluid handling system. The fluid system may serve any number of processes involving one or more preparation, sampling and analytical tasks. A few examples include high-throughput liquid sample assaying, high-pressure liquid chromatography, and dissolution testing. Filter elements are often installed “in-line” with such systems, and for this purpose can be housed within some type of filter unit equipped with fittings adapted for coupling and decoupling with the circuit in which fluid is moving. As with most engineered devices, it is well-known that filter elements have a limited useful life That is, after a period of service, filters are subject to degradation, clogging and other conditions which render them no longer useful or at least cause them to impede or restrict the performance of the fluid line in which they are installed. Hence, filters must be replaced periodically, preferably according to a predetermined maintenance schedule. Depending on the process with which fluid conveying and filtering are associated, the down-time and effort required in replacing filters can be a significant criterion. It follows that any means by which the task of replacing filters can be automated, or by which the automation of filter replacement can be improved, is welcomed by the pertinent industries.  
           [0003]    One approach to addressing the recognized problems associated with filter replacement is disclosed in U.S. Pat. No. 5,450,982 to Van Den Oever. The embodiments disclosed therein provide an automated filter changing apparatus consisting of a cylindrical filter dispensing device, a cylindrical filter clamping device, a cylindrical filter discharge device, and a means for transporting individual filters to these devices. The devices are arranged in either a linear or rotary arrangement. In the linear arrangement, a motor-powered lead screw and associated slide member are utilized to transport the filters. In the rotary arrangement, a turntable is substituted for the slide member.  
           [0004]    According to the above-cited disclosure, a vertical stack of filters is loaded into a hollow cylinder of the filter dispenser, and the lowermost filter drops into an aperture of the transporting means when the transporting means reaches the appropriate position. The transporting means then moves the filter to a position under the clamping device. The clamping device is a pneumatic ram through which a portion of a fluid sampling line runs. The ram bears down onto the filter and establishes a connection between the filter and the fluid sampling line, so that fluid flowing through the sampling line passes through the filter and thereby becomes filtered. The filter is then transported to the discharge device, where the filter is positioned under a hollow cylinder and over a second pneumatic ram. The second pneumatic ram forces the filter upwardly into the hollow cylinder, and the filter is retained there with the aid of a retaining ring.  
           [0005]    It is believed that there remains a need for a more practical and effective solution to providing an automated method and apparatus for replacing filters, especially filters of the type which operate in-line with a fluid circuit. There is a particular need for automating the replacement of filters which have inlet and outlet fittings extending outwardly from their housings. Such filters are often supplied in a stacked or columnar form in which each filter in the stack is connected to adjacent filters by mating the fittings of adjacent filters together. The present invention therefore provides a novel automated apparatus for changing or replacing filters, especially in-line filters, as described hereinbelow.  
         DISCLOSURE OF THE INVENTION  
         [0006]    The present invention generally provides a filter changing or replacing system comprising a filter dispensing assembly and/or a filter clamping assembly. Each device includes novel attributes which permit the successful implementation of a controlled, automated filter changing process.  
           [0007]    The filter dispensing device can be rotated, such as through the use of a motor and associated shaft. The filter dispensing device is adapted to receive filter storage units such as one or more magazines in which a plurality of filters are initially stored as a connected stack. The filter dispensing device includes a filter separating device having a stationary portion. The filter separating device operates to separate one or more stacks of filters into discrete filter units, such that individual filters are sequentially transported from the filter dispensing device, and preferably to a lateral guide track at which filter positioning devices are provided.  
           [0008]    The filter clamping assembly is adapted to operate in combination with the filter dispensing device and to receive one or more individual filter units dispensed therefrom, and provides one or more coupling sites which can fluidly communicate with one or more fluid lines. The filter clamping assembly is powered and actuated by means such as a motor and associate lead screw. Alternating or cyclical movement of the filter clamping device decouples used filters from fittings associated with the fluid lines, and couples unused filters to those fittings.  
           [0009]    Preferably, a filter position sensing device is provided at the clamping assembly, such as by mounting the sensing device to the lateral guide track, and a clamping position sensing device is additionally provided to monitor the position of a movable portion of the clamping assembly. In this manner, an electronic control unit can be placed in electrical communication with the position sensors and the motors to monitor and control the respective operations of both the filter dispensing device and the filter clamping device, and also coordinate the operations of those devices.  
           [0010]    According to a first embodiment of the present invention, a filter dispensing apparatus comprises a rotary member having a longitudinal axis, and a stationary member. The stationary member includes an annular interior surface disposed in coaxial relation to the rotary member. The stationary member also includes an inlet opening, an outlet opening disposed at an axial distance from the inlet opening, and a channel formed on the interior surface. The channel runs along a generally helical path with respect to the longitudinal axis, and has a varying pitch. The pitch of the channel increases with respect to an axial length of the interior surface. The channel communicates with the inlet opening and the outlet opening.  
           [0011]    According to a second embodiment of the present invention, a filter dispensing apparatus comprises a rotatable shaft, a filter handling device secured to the shaft and defining a first filter path, and a filter separation device. The filter separation device has an annular interior surface fixedly disposed in coaxial relation to the shaft. The filter separation device includes an entry location disposed in communication with the first filter path, an exit location disposed at an axial distance from the entry location, and a channel formed on the interior surface and defining a second filter path. The channel runs along a generally helical orientation with respect to the shaft, with a varying pitch of the channel increasing with respect to an axial length of the interior surface. The channel communicates with the entry location and the exit location.  
           [0012]    According to a third embodiment of the present invention, a filter clamping assembly comprises an actuator device, a first arm, a second arm, a track, and a filter positioning slide. The first arm includes a first fitting disposed in movable relation to the first arm. The second arm is disposed in movable engagement with the actuator device, and includes a second fitting disposed in movable relation to the second arm. The actuator device is adapted to adjust an axial distance between the first arm and the second arm. The track is interposed between the first fitting and the second fitting, and extends along a track direction. The filter positioning slide is slidable along a slide direction transverse to the track direction.  
           [0013]    According to a fourth embodiment of the present invention, a filter clamping assembly comprises an actuator device, a first arm, a second arm, a track, a plurality of first biasing members, and a plurality of second biasing members. The first arm includes a plurality of first fittings, with each first fitting disposed in movable relation to the first arm. The second arm is disposed in movable engagement with the actuator device and includes a plurality of second fittings, with each second fitting disposed in movable relation to the second arm. The actuator device is adapted to adjust an axial distance between the first arm and the second arm. The track is interposed between the first fittings and the second fittings. Each of the first biasing members engages a corresponding one of the first fittings for biasing the movement of that first fitting in relation to the first arm. Each of the second biasing members engages a corresponding one of the second fittings for biasing the movement of that second fitting in relation to the second arm.  
           [0014]    According to a fifth embodiment of the present invention, an automated filter changing apparatus comprises a filter separation device and a filter clamping device. The filter separation device includes a rotary portion and a stationary portion disposed in coaxial relation to the rotary portion. The stationary portion includes an annular interior surface, an exit location and a channel formed on the interior surface. The channel runs along a generally helical path with respect to the rotary portion, with a varying pitch of the channel increasing with respect to an axial length of the interior surface. The channel communicates with the exit location. The filter clamping device includes a filter guide portion communicating with the exit location, a first fitting, and a second fitting movable with respect to the first fitting.  
           [0015]    According to a sixth embodiment of the present invention, an automated filter changing apparatus comprises a filter dispensing device, an actuator device, a first arm, a second arm, and a track. The first arm includes a first fitting disposed in movable relation to the first arm. The second arm is disposed in movable engagement with the actuator device, and includes a second fitting disposed in movable relation to the second arm. The actuator device is adapted to adjust an axial distance between the first arm and the second arm. The track communicates with the filter dispensing device and is interposed between the first fitting and the second fitting.  
           [0016]    According to a seventh embodiment of the present invention, an automated filter changing apparatus comprises a filter dispensing device, a filter positioning track, and a filter coupling device. The filter positioning track communicates with the filter dispensing device and defines a plurality of laterally spaced filter coupling sites. The filter coupling device includes a plurality of first fluid fittings and a plurality of second fluid fittings. Each first fluid fitting is disposed over one of the coupling sites, and each second fluid fitting is disposed under one of the coupling sites.  
           [0017]    According to an eighth embodiment of the present invention, an automated filter changing apparatus comprises a filter dispensing device, a filter positioning track, a filter clamping device, a first position sensing device, a second position sensing device, and an electronic control unit communicating with the first and second position sensing devices. The filter positioning track is disposed in operative communication with the filter dispensing device and defines a plurality of laterally spaced filter coupling sites. The filter clamping device includes a movable member and a plurality of generally oppositely oriented first and second fluid fittings. Each first fluid fitting is disposed over one of the coupling sites, and each second fluid fitting is disposed under one of the coupling sites. The first position sensing device is disposed in operative alignment with one of the coupling sites. The second position sensing device is disposed in operative alignment with the movable member of the filter clamping device.  
           [0018]    According to a ninth embodiment of the present invention, an apparatus for replacing a filter in a fluid line comprises a rotary filter handling device, a stationary filter handling device, a filter guiding device, and a filter clamping device. The rotary filter handling device defines a generally downward first filter path. The stationary filter handling device defines a generally helical second filter path which communicates with the first filter path. The filter guiding device defines a third filter path. The third filter path communicates with the second filter path and is oriented in a generally transverse relation to the first filter path. The filter clamping device communicates with a fluid line, and is adapted for releasable engagement with a filter disposed in the filter guiding device.  
           [0019]    According to a tenth embodiment of the present invention, an apparatus for replacing a filter in a fluid line comprises a filter storage device, a filter clamping device, and means for transposing a plurality of filters from a stacked arrangement in the filter storage device to a sequential, lateral arrangement in the filter clamping device.  
           [0020]    According to an eleventh embodiment of the present invention, an apparatus for connecting a plurality of filters to a plurality of corresponding fluid lines comprises a filter storage device, a filter clamping device, filter conveying means, and clamping force distributing means. The filter clamping device includes a plurality of pairs of inlet and outlet fittings, with each pair of inlet and outlet fittings are adapted for communication with a fluid line. The filter clamping device is adapted to impart a total clamping force to a plurality of filters received in the filter clamping device to connect each filter, under influence of a portion of the total clamping force, in fluid communication with a corresponding one of the pairs of inlet and outlet fittings. The filter conveying means conveys the plurality of filters from the filter storage device to the filter clamping device. The clamping force distributing means distributes the total clamping force to the plurality of filters to reduce variations among the portions of the total clamping force imparted to each filter by the filter clamping device.  
           [0021]    According to a twelfth embodiment of the present invention, an apparatus for connecting a filter to a fluid line comprises a filter storage device, a filter clamping device, filter conveying means, and filter positioning means, The filter clamping device includes an inlet fitting and an outlet fitting, which are adapted for communication with a fluid line. The filter conveying means conveys a filter having first and second fittings from the filter storage device to the filter clamping device. The filter positioning means aligns the first fitting of the filter with the inlet fitting of the filter clamping device, and the second fitting of the filter with the outlet fitting of the filter clamping device.  
           [0022]    It is therefore an object of the present invention to provide an apparatus for dispensing one or more filters to a device which subsequently couples the filter to a fluid line or fluid circuit.  
           [0023]    It is another object of the present invention to provide an apparatus for dispensing a plurality of filters initially provided in a stacked form wherein the fittings of each filter in the stack are typically mated to the fittings of adjacently situated filters, such that the filter stack encounters a separating device which separates each filter from the other filters, and with the result that each filter is dispensed individually with respect to the other filters.  
           [0024]    It is yet another object of the present invention to provide an automated apparatus for replacing one or more existing filters operating within a fluid line with one or more unused filters by dispensing individual, unused filters to a filter clamping device, decoupling the existing filters from the fluid line, positioning the unused filters at appropriate coupling sites of the fluid line, and coupling the unused filters to the fluid line at the coupling sites.  
           [0025]    It is still another object of the present invention to provide a filter changing apparatus which coordinates the operations of a filter dispensing device with a filter clamping device, in part by counting the number of individual filters being loaded into the clamping device and by determining when the clamping device has reached an open state at which used filters can be replaced with new filters.  
           [0026]    It is a further object of the present invention to provide a filter clamping apparatus which permits used filters to be decoupled from a fluid line for subsequent replacement with unused filters, wherein the filter clamping apparatus can evenly distribute the clamping force needed for connecting each filter with inlet and outlet fittings of the fluid line corresponding to that filter.  
           [0027]    It is an additional object of the present invention to provide a filter changing apparatus which includes a filter positioning device that ensures that filters transported by the filter changing apparatus are brought into proper alignment with a filter clamping device.  
           [0028]    Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a perspective view of a filter changing apparatus provided in assembled form according to the present invention;  
         [0030]    [0030]FIGS. 2A and 2B are exploded and assembled side elevation views, respectively, of a filter unit suitable for use in conjunction with the filter changing apparatus illustrated in FIG. 1;  
         [0031]    [0031]FIG. 3 is a perspective view of a rotatable portion of a filter unit separation assembly forming a part of the filter changing apparatus illustrated in FIG. 1;  
         [0032]    [0032]FIG. 4 is a side elevation view of a filter unit storage magazine, with a stack of connected filter units contained therein, adapted for use in conjunction with the filter changing apparatus illustrated in FIG. 1;  
         [0033]    [0033]FIG. 5 is a detailed perspective view of a section of the filter changing apparatus illustrated in FIG. 1, wherein the filter unit separation assembly is shown in partial cutaway view and certain components of the filter changing apparatus have been removed to illustrate a helical path and subsequent lateral path traversed by a series of filter units during operation of the filter changing apparatus;  
         [0034]    [0034]FIG. 6 is a perspective view of the stationary portion of the filter unit separation assembly illustrating an internal threaded or grooved design;  
         [0035]    [0035]FIG. 7 is a perspective partial cutaway view of the stationary portion illustrated in FIG. 6;  
         [0036]    [0036]FIG. 8 is a perspective view of a filter unit clamping assembly forming a part of the filter changing apparatus illustrated in FIG. 1;  
         [0037]    [0037]FIG. 9 is a detailed perspective view of a section of the filter changing apparatus illustrated in FIG. 1 wherein the filter unit clamping assembly illustrated in FIG. 8 has been installed in the filter changing apparatus;  
         [0038]    [0038]FIG. 10 is a detailed perspective view of a section of the filter changing apparatus illustrated in FIG. 1, wherein a portion of the filter unit clamping assembly has been removed to highlight a lateral track forming a part of the filter changing apparatus and components utilized to position filter units in the lateral track;  
         [0039]    [0039]FIG. 11 is a detailed perspective view of a section of the filter changing apparatus illustrated in FIG. 1, wherein a sensing device has been provided in accordance with the present invention;  
         [0040]    [0040]FIG. 12 is a detailed perspective view of a section of the filter changing apparatus illustrated in FIG. 1, wherein another sensing device has been provided in accordance with the present invention; and  
         [0041]    [0041]FIG. 13 is a simplified schematic diagram of an electronic control circuit employed in conjunction with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]    Referring now to FIG. 1, an automated in-line filter changing apparatus generally designated  10  is illustrated in assembled form. By way of example, filter changing apparatus  10  has a structural framework generally including an upper deck  12  and a lower deck  14 . Upper deck  12  is supported above lower deck  14  by one or more spacer members  16 . Broadly stated, filter changing apparatus  10  includes a filter unit storage, separation and dispensing assembly generally designated  50  (hereinafter referred to as “filter separation assembly  50 ”), a filter unit clamping assembly generally designated  100 , and an electronic control unit generally designated  200 . In the embodiment illustrated in FIG. 1, filter separation assembly  50  and filter clamping assembly  100  are supported on upper deck  12 . Filter changing apparatus  10  also includes a filter unit positioning track, generally designated  130 , mounted on upper deck  12 . A series of one or more fluid line fittings  18  are installed in a bracket  21  mounted to lower deck  14 , and are adapted to be coupled with the conduits of a fluid circuit (not shown). Filter changing apparatus  10  further includes a filter unit position sensor generally designated  23  and a filter unit clamping assembly position sensor generally designated  25 , the details and functions of which are described hereinbelow. Preferably, many of the various components of filter changing apparatus  10  illustrated in FIG. 1, with the possible exception of the upper portions of filter separation assembly  50 , are contained within a housing structure with a removable top cover which are not shown for purposes of clarity.  
         [0043]    In a preferred implementation of the present invention, filter separation assembly  50 , filter clamping assembly  100  and electronic control unit  200  operate in conjunction with each other to automate the replacement of “in-line” type filter units. Such filter units can be those typically employed in a fluid sampling or fluid delivery system. Suitable filter units are manufactured by Millipore Inc. and are available from VanKel Technology Group as Part No. 17-4220. The respective exploded and assembled views of FIGS. 2A and 2B illustrate an example of a suitable filter unit, generally designated  30 . Filter unit  30  has Luer-style fittings which, when fitted to flexible conduits or tubing, require only an axial load in order to establish an adequate seal. Exemplary filter unit  30  includes an upper shell portion  32  with a hollow female fitting  32 A, a lower shell portion  34  with a hollow male fitting  34 A, and a filter element  36  housed therebetween. The implementation of filter changing apparatus  10  illustrated in FIG. 1 is useful in many chemistry-related processes wherein filter units  30  are prone to clogging, chemical carry-over or other conditions requiring filter replacement, and wherein it is advantageous that such replacements be controlled and/or timed with relationship to some other device or instrument.  
         [0044]    Referring to FIGS.  3 - 7 , various details of filter separation assembly  50  and related components are illustrated. The exemplary assembly  50  as illustrated herein performs the functions of storing a supply of unused filter units  30 , separating individual filter units  30 , and delivering each individual filter unit  30  to filter clamping assembly  100 . In the preferred embodiment, these functions are integrated into a single assembly which has both rotating and stationary portions, but it will be understood that structurally distinct storage, separation and dispensing subassemblies could be implemented in accordance with the present invention.  
         [0045]    Referring specifically to FIG. 3, filter separation assembly  50  includes a filter unit magazine holding and support device in the form of a filter unit magazine carrousel generally designated  55 , and a rotor  60  attached thereto. Referring to FIG. 4, magazine carrousel  55  is adapted to hold and support one or more filter unit magazines, generally designated  40 , for example eight magazines  40 , which are preferably provided in a tube-like or cylindrical form. As shown in FIG. 4, filter unit magazine  40  includes a magazine wall  42  and open upper and lower ends  42 A and  42 B, respectively. Magazine wall  42  is preferably constructed from a transparent material. Filter unit magazine  40  is adapted to receive and store a plurality of filter units such as filter units  30  in a stacked arrangement, wherein each filter unit  30  is connected or mated to at least one other adjacent filter unit  30  by inserting male fitting  34 A of one or more filter units  30  into female fitting  32 A of an adjacent filter unit  30 . In one exemplary embodiment, each magazine  40  is adapted to store a stack or column of 25 filter units  30  such that when eight magazines  40  are employed, a total of 200 unused filter units  30  can be loaded into filter separation assembly  50 . If desired, magazines  40  can be lengthened in order to hold an additional number of filter units  30 . An end cap  44  can be attached to upper end  42 A of each magazine  40  to close off upper end  42 A. An additional end cap (not shown) can be attached to lower end  42 B to fully confine a stack of filter units  30  within magazine  40  when magazine  40  is not loaded into magazine carrousel  55 .  
         [0046]    Referring back to FIG. 3, magazine carrousel  55  includes an upper rack  57  situated at a distance from rotor  60  by means of one or more elongate spacer members  59 . Upper rack  57  defines recessed sections  57 A shaped to laterally support or at least accommodate the profile of each magazine  40  installed in magazine carrousel  55 . One or more magazines  40  are installed in filter separation assembly  50  by inserting their respective lower ends  42 B into bores  70 A of a barrel portion  70 . Depending on the particular design implemented, barrel portion  70  can be considered as forming a part of either magazine carrousel  55  or rotor  60 . As further shown in FIG. 3, rotor  60  includes upper recessed sections  60 A disposed above barrel portion  70  and lower recessed sections  60 B disposed below barrel portion  70 . Upper recessed sections  60 A are shaped to accommodate the shape of magazines  40 , and lower recessed sections  60 B are shaped to accommodate the shape of filter units  30  traveling out of barrel portion  70 , as described in more detail hereinbelow.  
         [0047]    Referring to FIG. 1 and the cutaway view of FIG. 5, filter separation assembly  50  also includes an internally threaded, annular base block or collar  80  mounted on upper deck  12  below barrel portion  70 , and circumscribing at least a lower portion of rotor  60 . Magazine carrousel  55  and rotor  60  rotate together about the axis of a rotor shaft  65  in the counterclockwise direction indicated by arrow A in FIG. 5, while base block  80  remains stationary. Referring back to FIG. 1, rotor shaft  65  is driven by a stepper motor  67  housed between upper and lower decks  12  and  14  of filter unit changing apparatus  10 . Motor  67  is supported by a bracket  67 A, and appropriate gearing or transmission means (not specifically shown) situated underneath upper deck  12  provide mechanical coupling and rotational speed adjustment between motor  67  and rotor shaft  65 .  
         [0048]    Referring to FIGS. 6 and 7, base block  80  includes a continuous, helical or spiral groove or channel  82  oriented along a generally helical or spiral path leading from a starting point B near the top of base block  80  to a terminal point (not specifically shown) near the bottom of base block  80 . For a purpose to be described hereinbelow, helical groove  82  is characterized by an increasing pitch in the axial direction represented by arrow C. The increasing pitch is illustrated in FIG. 7 by observing the increasing distances D 1 , D 2 , D 3  and D 4  between a lower surface  82 A of helical groove  82  at axially spaced elevation points E 1 , E 2 , E 3  and E 4  shown along the cross-section of base block  80 . To provide an entry point for individual filter units  30  into helical groove  82  and into base block  80  and an exit point therefrom, base block  80  defines a filter unit entry location generally designated  84  and a filter unit exit location generally designated  86 , respectively. Entry location  84  is generally defined between point B and a lip  88 , which lip  88  is defined at a top surface  80 A of base block  80  and protrudes radially inwardly toward the axis of rotor shaft  65 . Exit location  86  is defined by a number of surfaces or edges such as surfaces  80 B and  80 C designed in part to accommodate the profile of filter units  30  exiting therefrom.  
         [0049]    Referring to FIGS.  8 - 10 , filter unit clamping assembly  100  and related components of filter changing apparatus  10  are illustrated in more detail. As will become evident hereinbelow, the primary function of filter clamping assembly  100  is to couple one or more new filter units  30  dispensed from filter separation assembly  50  to a fluid circuit communicating with filter clamping assembly  100  and thereby establish one or more flow paths therethrough, as well as to decouple used filter units  30  from the fluid circuit once such filter units  30  have been in service for a predetermined period of time or number of cycles. For the purpose of description, filter clamping assembly  100  defines one or more fluid coupling sites generally designated CS 1 -CS 8 , respectively (see FIG. 10). The fluid circuit referenced herein can be part of any number of different types of processes, involving various apparatuses situated both upstream and downstream of filter changing apparatus  10 , such as fluid pumps, dissolution testing stations, liquid chromatography devices, and the like.  
         [0050]    Filter unit clamping assembly  100  includes an upper arm  102 , a lower arm  104 , and one or more vertical rails  106  along which upper arm  102  slides with respect to lower arm  104 . In the exemplary embodiment illustrated in FIGS. 1 and 9, lower arm  104  is secured to the underside of upper deck  12  of filter changing apparatus  10 . One or more upper male fittings  108  are movably supported through the thickness of upper arm  102  and are biased by load springs  110 . Likewise, one or more corresponding lower female fittings  112  are movably supported through the thickness of lower arm  104  in coaxial alignment with upper fittings  108 , and are also biased by load springs  114 . There is accordingly a pair of upper and lower fittings  108  and  112  for each coupling site CS 1 -CS 8 , with upper fittings  108  situated generally above lateral track  130  and lower fittings  112  situated generally below later track  130 . The displacement of upper arm  102  with respect to lower arm  104  is driven by a stepper motor  116 , which is mounted between upper and lower decks  12  and  14  of filter changing apparatus  10  as shown in FIG. 1, and an associated lead screw  118 .  
         [0051]    The illustrated driving means is preferred for its strength, speed, reliability, controllability and quietness, and because it does not require continuous power in order to maintain clamping force. It will be understood, however, that other known means such as pneumatic or solenoid-type actuating devices could be provided in the place of stepper motor  116  and lead screw  118  for producing a clamping action with the required clamping force.  
         [0052]    Load springs  110  and  114  ensure that an excessive clamping force exerted by clamping assembly  100  does not damage fittings  32 A and  34 A of filter units  30  or crush filter units  30  and, when more than one filter unit  30  is placed in use in filter clamping assembly  100 , that the clamping force is evenly distributed among the several filter units  30  residing in lateral track  130 . That is, because all upper fittings  108  are supported in a single upper arm  102  in the exemplary embodiment, and all lower fittings  112  are supported in a single lower arm  104 , a fraction of the total clamping force developed by clamping assembly  100  is transferred to each filter unit  30  residing at the coupling sites CS 1 -CS 8 . The design of clamping assembly  100  according to the present invention, however, ensures that this total clamping force is substantially evenly distributed to each filter unit  30 , such that the fractional clamping force imparted to one filter unit  30  is substantially equal to the fractional clamping forces respectively imparted to the other filter units  30 .  
         [0053]    Referring to FIGS. 1 and 9- 11 , filter unit positioning track  130  and associated filter unit position sensor  23  are illustrated. Track  130  is disposed in a lateral orientation with respect to filter separation assembly  50 . Preferably, track  130 , upper fittings  108  and lower fittings  112  are further arranged in a linear orientation, although it will be understood that a curved orientation could be employed without affecting the sequential, side-by-side loading of filter units  30  into filter clamping assembly  100 . Track  130  includes a front guide rail  132  and a rear guide rail  134  which face each other and are mounted on upper deck  12  of filter changing apparatus  10 . Front and rear guide rails  132  and  134  each have opposing channels or grooves  132 A and  134 A which, in conjunction with the spacing between front and rear guide rails  132  and  134 , provide an open track volume with a cross-section shaped to accommodate the cross-sectional profile of filter units  30 . In this manner, filter units  30  can slide laterally through track  130  in a guided manner with their female fittings  32 A oriented upwardly. In addition, at each coupling site CS 1 -CS 8 , respective female fittings  32 A of filter units  30  can become aligned with corresponding male fittings  108  of filter clamping assembly  108 , and respective male fittings  34 A of filter units  30  can become aligned with corresponding female fittings  112  of filter clamping assembly  100 . The open track volume begins at an inlet end (not specifically shown) of lateral track  130  which directly or indirectly communicates with exit location  86  of base block  80 , and terminates at a discharge end, generally designated  138 . A waste receptacle (not shown) can be provided to receive filter units  30  expelled from discharge end  138 .  
         [0054]    Preferably, front guide rail  132  includes a removable top portion  141  (see FIGS. 1 and 11). With top portion  141  removed as shown in FIGS. 9 and 10, it is seen that front guide rail  132  has a plurality of recesses adapted to receive a plurality of filter unit retainer elements or positioning slides  160 . Preferably, at least one filter positioning slide  160  exists for each coupling site CS 1 -CS 8 . Positioning slides  160  move within the recesses of front guide rail  132  along a direction transverse to the direction of lateral track  130 , and are guided along respective posts  162 . Each positioning slide  160  has a generally indented or recessed inner edge  160 A, and includes a spring  164  mounted about its associated post  162  to bias slide  160  inwardly toward lateral track  130 . By this configuration, each positioning slide  160  assists in aligning fittings  32 A and  34 A of each filter unit  30  with correspondingly situated fittings  108  and  112  of filter clamping assembly  100 , such that one or more filter units  30  can be serially or sequentially positioned at coupling sites CS 1 -CS 8  in an indexing fashion.  
         [0055]    As best shown in FIG. 11, at least one filter unit positioning sensor  23  is mounted in a cut-out section of top portion  141  of front guide rail  132  over first positioning slide (herein specifically designated  160 ′) and proximate to first coupling site CS 1  of filter clamping assembly  100 —that is, the first coupling site encountered by filter units  30  as they exit from filter separation assembly  50  into lateral track  130 . Preferably, filter unit positioning sensor  23  is an LED device, and includes a structural gap  23 A across which a light beam is directed and electrically conductive leads  23 B communicating through conduits (not shown) with electronic control unit  200 . Filter unit positioning sensor  23  functions in cooperation with a home sensor flag  170  to detect the arrival and proper alignment of a filter unit  30  at first coupling site CS 1 . Home sensor flag  170  is provided essentially in the form of an elongate structural member as shown in FIGS. 9 and 10, and protrudes upwardly from first positioning slide  160 ′.  
         [0056]    Home sensor flag  170  moves with first positioning slide  160 ′. Thus, as a filter unit  30  moves along lateral track  130  toward the position at first coupling site CS 1 , filter unit  30  initially pushes first positioning slide  160 ′ outwardly from lateral track  130 , thereby building up stored potential energy in associated spring  164 . As filter unit  30  continues to approach first coupling site CS 1 , indented edge  160 A of first positioning slide  160 ′ permits spring  164  to relax. That is, the combination of spring  164  and indented edge  160 A of first positioning slide  160 ′ coact to urge filter unit  30  into the properly aligned position at first coupling site CS 1 , such that fittings  32 A and  34 A of filter unit  30  are aligned with corresponding fittings  108  and  112  of filter clam ping assembly  100 . The displacement of first positioning slide  160 ′ with respect to lateral track  130  and front guide rail  132  causes home sensor flag  170  to break the light beam produced by filter unit position sensor  23  across its gap  23 A, so that filter unit position sensor  23  detects when filter unit  30  has reached the properly aligned “home” position at first coupling site CS 1 . When more than one filter unit  30  is to be employed along lateral track  130 , filter unit position sensor  23  and home sensor flag  170  are also utilized to count the number of filter units  30  that have been advanced along lateral track  130  into alignment with coupling sites CS 1 -CS 8 . Hence, after a predetermined number of filter units  30  have been positioned in filter clamping assembly  100 , an appropriate signal can be generated by electronic control unit  200  to cause filter separation assembly  50  to cease rotation and thus to cease advancement of filter units  30  into lateral track  130 .  
         [0057]    Referring to FIG. 12, clamping assembly position sensor  25  is mounted to upper arm  102  of filter clamping assembly  100  and straddles a threaded lead screw nut  175  through which lead screw  118  is rotatably supported. Preferably, clamping assembly position sensor  25  is of the same design as filter unit position sensor  23 , and thus includes a structural gap  25 A across which a light beam is directed and electrically conductive leads  25 B communicating through conduits (not shown) with electronic control unit  200 . Lead screw  118  serves as the home sensor flag for clamping assembly position sensor  25 . When upper arm  102  reaches its uppermost position with respect to lower arm  104 , the topmost surface of lead screw is disposed below gap  25 A, at which point the light beam is unbroken and clamping assembly position sensor  25  detects that upper arm  102  is “home.” 
         [0058]    Referring to FIG. 13, a simplified schematic diagram of electronic control unit  200  and its associated circuit are illustrated. The primary function of electronic control unit  200  is to control and coordinate the relative motions of filter separation assembly  50  and clamping assembly  100 , according to principles known to those skilled in the art. Electronic control unit  200  can be disposed in a suitable location such as being integrated in filter changing apparatus  10  as shown in FIG. 1, although electronic control unit  200  could be situated in a remote location with respect to filter changing apparatus  10 . Electronic control unit  200  is adapted to receive signals from filter unit position sensor  23  over line  202  and from clamping assembly position sensor  25  over line  204 . Electronic control unit  200  is also adapted to send signals to motor  67  associated with filter separation assembly  50  over line  206  and to motor  116  associated with filter clamping assembly  100  over line  208 . Electronic control unit  200  can also be adapted to receive computer coded commands, and preferably both RS232 and RS485 serial commands, from a secondary control unit  220  over line  210 . Alternately, electronic control unit  200  itself can be adapted to both process inputted commands and condition signals. Secondary control unit  220  can be provided in the form of a CPU-based device, such as a remote computer terminal, or could represent an electronic control device which is part of an additional apparatus situated upstream or downstream of the fluid lines communicating with filter changing apparatus  10 .  
         [0059]    In operation, filter changing apparatus  10  is configured to handle a predetermined number of magazines  40  (e.g., one to eight magazines  40 ), each containing a stack of filter units  30 . One or more magazines  40  are then loaded into a bore or bores  70 A of barrel portion  70  of filter separation assembly  50 . At this point, depending on the rotary position of rotor  60  and magazines  40  relative to base block  80 , the lowermost filter unit  30  of one of the stacks will have come to rest either on top surface  80 A of base block  80  or directly on the initial section of base block groove  82  within entry location  84  (see FIGS. 6 and 7). During normal use, a predetermined number of used filter units  30  are operatively positioned along lateral track  130  at coupling sites CS 1 -CS 8  and clamping assembly  100  is disposed in its fully closed or clamped position. Accordingly, male and female fittings  34 A and  32 A of each used filter unit  30  are mated to corresponding female and male fittings  112  and  108  of clamping assembly  100 , the fluid circuit in which filter changing apparatus  10  is operating is closed, and the fluid flow paths are thus operative.  
         [0060]    If it is determined (either manually or according to a programmed schedule) that working filter units  30  should be replaced with new filter units  30 , electronic control unit  200  either generates a command to change out filter units  30  or receives the command from secondary control unit  220 . Following this command for filter replacement, electronic control unit  200  sends an appropriate control signal to activate clamping assembly motor  116 . Motor  116  powers lead screw  118  to cause upper arm  102  of clamping assembly  100  to travel upwardly, thus opening clamping assembly  100 , decoupling filter units  30  residing in lateral track  130  from fittings  108  and  112  of clamping assembly  100 , and consequently switching the fluid circuit into an open-circuit state. When upper arm  102  reaches its uppermost “home” position shown in FIG. 12, this event is detected by clamping assembly position sensor  25  as described hereinabove, and clamping assembly position sensor  25  sends a transduced signal to electronic control unit  200 . In response, electronic control unit  200  sends an appropriate control signal to activate filter separation assembly motor  67 , which causes rotor  60  to turn filter separation assembly  50  in a counterclockwise orientation about the axis of rotor shaft  65 .  
         [0061]    As rotor  60  rotates magazine carrousel  55  of filter separation assembly  50 , lowermost filter unit  30  of at least one magazine  40  gravitates from barrel portion  70  through entry location  84  into base block groove  82  and is guided by one of lower recesses  60 B of rotor  60 . As generally illustrated in FIG. 5, filter units  30  of other magazines  40  begin to follow the same path. Protruding lip  88  of base block  80  ensures that lowermost filter unit  30  begins to properly travel along the curved path of groove  82 , such that upper shell portion  32  of lowermost filter unit passes underneath lip  88 . As rotor  60  continues to turn, the pitch of groove  82  increases as described hereinabove with reference to FIG. 7. As a result, the rotation of rotor  60  with respect to groove  82  urges the spacing to increase between lowermost filter unit  30  and the filter unit connected to lowermost filter unit  30 . At some point within base block  80 , lowermost filter unit  30  becomes completely disconnected from its associated filter stack. Continued rotation causes separated filter unit  30  to exit base block  80  (and thus filter separation assembly  50 ) through exit location  86  and enter lateral track  130 .  
         [0062]    Referring to FIGS. 5, 9 and  10 , and assuming for the sake of example that eight new filter units  30  are to replace eight old filter units  30 , filter units  30  traveling along lateral track  130  continue to be advanced in indexing fashion through coupling sites CS 1 -CS 8  by the urging of ensuing filter units  30 . Filter unit position sensor  23  detects the presence of each filter unit  30  locking into and passing through first coupling site CS 1 , in the manner described hereinabove. Accordingly, as each filter unit  30  passes through first coupling site CS 1 , filter unit position sensor  23  sends a transduced signal to electronic control unit  200  to enable electronic control unit  200  to count the number of filter units  30  entering lateral track  130  (and hence the number of filter units  30  being loaded into clamping assembly  100 ). In addition, as each filter unit  30  advances into the next indexed coupling site CS 2 -CS 8 , one used filter unit  30  is pushed out from filter changing apparatus  10  through discharge end  138  of lateral track  130  and can then be collected in a waste receptacle if desired. When eight filter units  30  have been counted, electronic control unit  200  issues an appropriate control signal to deactivate filter separation assembly motor  67 . At this point, due to the action of filter unit positioning slides  160  as described hereinabove, each filter unit  30  residing in lateral track  130  is positioned at a corresponding coupling site CS 1 -CS 8  in proper alignment with fittings  108  and  112  of clamping assembly  100 , as best illustrated in FIGS.  10 - 12 . Finally, electronic control unit  200  causes clamping assembly  100  to mate fittings  32 A and  34 A of newly loaded filter units  30  with corresponding fittings  108  and  112  of clamping assembly  100 , and a continuous fluid circuit is thereby reestablished with new filter units  30  automatically installed in-line.  
         [0063]    It will be evident from the foregoing description that filter changing apparatus  10  is useful to transferring one or more filter units  30  from a stacked or columnar arrangement to an individualized or indexed, lateral side-by-side arrangement. In addition, the design of filter changing apparatus  10  and that of its various components as described hereinabove, as well as the interaction of the various components, ensures that the operations and functions performed by filter changing apparatus  10  are not adversely affected by varying situations expected to be encountered in the use of filter changing apparatus  10 . Such situations include (1) a plurality of magazines  40  loaded in magazine carrousel  55  with differing numbers of filter units  30 ; (2) magazines  40  being absent from one or more bores  70 A of barrel portion  70 ; and (3) the occasional failure of a lowermost filter unit  30  of a stack to drop down into entry point  84  of base block  80  during rotation of filter separation assembly  50 .  
         [0064]    It will be further understood that various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.