Abstract:
Occlusion assemblies facilitating occlusion of flexible tubing are disclosed. Occlusion assemblies may be associated with or form part of a medical infusion device and may facilitate fluid handling by such devices. Occlusion assemblies may position and immobilize tubing. Occlusion assemblies comprise a tubing occluder constructed and positioned to apply a force to tube(s) to occlude the tubes. Occlusion assemblies may be configured to include a single tube in certain cases, and in other cases to occlude multiple tubes, whether an odd number of tubes or an even number of tubes. Occlusion assemblies may include automatic actuators and in certain cases also include a manual actuator to provide an override function. Occlusion assemblies may include safety features, for example, to prevent a release of occlusion force on the tubing and/or convenience features, for example a retainer mechanism to hold the tube occluder in a non-occluding position.

Description:
FIELD 
       [0001]    The present specification generally describes occluder devices for occluding flexible tubing, particularly in medical infusion systems. 
       BACKGROUND 
       [0002]    Medical devices, such as hemodialysis machines, medical infusion pumps, plasmapheresis devices, and the like, often require the use of tubing to facilitate the flow of fluids, e.g., to or from a patient using such device. Such tubing in many instances is made of a flexible material and is designed to be collapsible in order to facilitate peristaltic pumping and/or occlusion of fluid flow via collapse of the lumen of the flexible tubing. A variety of tubing clamps and tubing occlusion devices are known. Certain of these devices can be integrated into a medical infusion device and automatically controlled. In certain applications, medical infusion devices must handle fluids that include ingredients that, due to leakage or other factors that may lead to presence of the fluid on the external surfaces of the tubing, can become sticky and or result in fouling or failure of certain conventional tubing occluder designs. 
       SUMMARY 
       [0003]    Described herein are occlusion assemblies configured to facilitate the opening and closing by occlusion of flexible tubing. In particular embodiments, the occlusion assemblies are associated with or form part of a medical infusion device, such as a hemodialysis device, peritoneal dialysis device, plasmapheresis device, etc., and may be controllably and automatically operated to facilitate fluid handling by such devices. The occlusion assemblies may be designed to position and immobilized the tubing and may include a frame or other support feature providing tubing guides and/or configured for attachment to or integration with a fluid handling assembly of a device of which they are part or with which they are used. The occlusion assemblies comprise a tubing occluder, which may be a mechanism constructed and positioned to apply a force to the tube(s) associated with the occlusion assembly to occlude the tubes and to release the force to allow the tubes to open for fluid flow. The occlusion assemblies and tubing occluders may be configured to include a single tube in certain cases, and in other cases to occlude multiple tubes, whether an odd number of tubes or an even number of tubes. Certain occlusion assemblies are specifically configured for occluding one or more pairs of tubes and may include tubing occluders having a separate occluding member for occluding each of the pair of collapsible tubes. The occlusion assemblies may include automatic actuators for operating the tubing occluders, and in certain cases also include a manual actuator to provide an override function. The occlusion assemblies may include a door designed and positioned to cover at least a portion of the tubes to be occluded and tubing occluder mechanism. Such occlusion assemblies may include safety features, for example, to prevent a release of occlusion force on the tubing when the door is not in a closed position and/or convenience features, for example a retainer mechanism to hold the tube occluder in a non-occluding position when the door is open with the tube occluder in the non-occluding position. 
         [0004]    In one aspect, a variety of occlusion assemblies for occluding at least one collapsible tube of a medical infusion device are described. In certain embodiments, the occlusion assembly is configured for occluding at least one pair of collapsible tubes and comprises, for each pair of collapsible tubes, a first occluding member and a second occluding member, the first occluding member positioned adjacent to a first collapsible tube of the pair and the second occluding member positioned adjacent to a second collapsible to the pair, when the tubes are installed in the occlusion assembly for operation. The first occluding member and the second occluding member are further positioned adjacent from each other such that a space is defined between them. These space is on an opposite side of each occluding member then is the collapsible tube to which it is adjacent. The occlusion assembly further comprises a spreader positioned within the space between the occluding members and movable from a first position to a second position, wherein movement from the first position to the second position causes the spreader to force at least a portion of the first and second occluding members to move apart from each other to increase the size of the space between them and forced a tube-contacting portion of each occluding member against the collapsible tube to which it is adjacent to occlude the collapsible tube. The occlusion assembly further comprises at least one actuator constructed and positioned to move the spreader between the first and second positions. 
         [0005]    In certain embodiments the occlusion assembly is configured for occluding at least one collapsible tube and comprises a frame comprising a tubing guide configured for positioning the collapsible tube, a tubing occluder mounted to the frame and comprising an occluding member constructed and positioned to controllably occlude or release occlusion of the collapsible tube, a door hingeably mounted to the frame and positioned to cover at least a portion of the collapsible tube and tubing occluder when in a closed position and to provide user access to the collapsible tube when in an open position, and a switch configured and positioned to detect when the door is in a closed position and to permit operation of the tubing occluder to release occlusion of the collapsible tube only when the door is in the closed position. 
         [0006]    In certain embodiments and occlusion assembly for collapsing at least one collapsible tube comprises a tubing occluder comprising an occluding member constructed and positioned to controllably occlude or release occlusion of the collapsible tube, and automatic actuator operatively coupled to the tubing occluder to cause essentially linear motion of at least a portion of the tubing occluder to cause the occluding member to move from an occluding position to a non-occluding position, and an override mechanism operatively coupled to the tubing occluder to cause essentially linear motion of at least a portion of the tubing occluder to cause the occluding member to move from an occluding position to anon-occluding position upon manual operation of the override mechanism by a user. 
         [0007]    In certain embodiments, and occlusion assembly for occluding at least one collapsible tube comprises a frame comprising a tubing guide configured for positioning the collapsible tube, a tubing occluder mounted to the frame and comprising an occluding member constructed and positioned to controllably occlude or release occlusion of the collapsible tube, a door hingeably mounted to the frame and positioned to cover at least a portion of the collapsible tube and tubing occluder when in a closed position and to provide user access to the collapsible tube when in an open position, and a retainer mechanism engaged by the door when the door is in the closed position and configured to permit operation of the tubing occluder to occlude or release occlusion of the collapsible tube when the door is in the closed position and configured to engage and retain the tubing occluder in a non-occluding configuration when the door is opened while the tubing occluder is positioned in the non-occluding configuration. 
         [0008]    In another aspect a method of operating an occlusion assembly for occluding at least one pair of collapsible tubes of a medical infusion devices disclosed. In one embodiment, the method involves moving a spreader of the occlusion assembly from a first position to a second position, wherein the spreader is positioned within a space defined between a first occluding member and a second occluding member to cause the spreader to force at least a portion of the first and second occluding members to move apart from each other to increase the size of the space between them and force a tube-contacting portion of each occluding member against a collapsible tube to which it is adjacent to occlude the collapsible tube. 
         [0009]    Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and/or inconsistent disclosure, the present specification shall control. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The accompanying drawings are schematic are not intended to be drawn to scale. In the figures, each identical, or substantially similar component that is illustrated in various figures is typically represented by a single numeral or notation. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In the drawings: 
           [0011]      FIG. 1  shows an exploded, perspective view of an occlusion assembly from a front angle in accordance with an embodiment of the present disclosure; 
           [0012]      FIG. 2  shows an exploded, perspective view of the occlusion assembly of  FIG. 1  from a back angle; 
           [0013]      FIG. 3  shows a front, perspective view of the occlusion assembly of  FIG. 1  with the door open and the button pressed to illustrate loading of a tube; 
           [0014]      FIG. 4  shows a close-up perspective view of the occlusion assembly of  FIG. 1 , showing the door engaging a switch when the door is closed; 
           [0015]      FIG. 5  shows the front of the occlusion assembly of  FIG. 1  without the door and frame to illustrate the arms fully occluding flexible tubes; 
           [0016]      FIG. 6  shows the front of the occlusion assembly of  FIG. 1  without the door and frame to illustrate the arms in a non-occluding position; 
           [0017]      FIG. 7  is a rear/top perspective view of the occlusion assembly of  FIG. 1  with an actuator arm in a fully retracted position; 
           [0018]      FIG. 8  is a rear perspective view of the occlusion assembly of  FIG. 1  with an actuator arm in a fully extended position; 
           [0019]      FIG. 9  shows a side perspective view of several working parts of the occlusion assembly of  FIG. 1  in a non-occluding state; 
           [0020]      FIG. 10  shows a side perspective view of several working parts of the occlusion assembly of  FIG. 1  in an occluding state; 
           [0021]      FIG. 11  shows a side, cross-sectional view of an actuator of the occlusion assembly of  FIG. 1 , illustrating a location for a main spring for the assembly; and 
           [0022]      FIG. 12  shows the occlusion assembly of  FIG. 1  mounted in a front panel assembly of a hemodialysis apparatus in accordance with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    In accordance with one aspect of the disclosed invention, an occlusion assembly for compressing at least one flexible tube, for example a pair of flexible tubes is described. The occlusion assembly includes a tube occluder comprising a mechanism configured to occlude fluid flow within one or more flexible tubes, and in certain embodiments one or more pairs of flexible tubes. In certain embodiments, the tube occluder of the occlusion assembly comprises at least one occluding member, and in a specific embodiment comprises an occluding member for each section of tubing placed within the assembly. In certain such embodiments, each occluding member is pressed or otherwise forced or urged into an occluding position by an element that slides along a side of the occluding member, causing the occluding member to pivot at its proximal end and to translate toward the tubing at its distal end. In an embodiment, the element is positioned between two occluding members and acts to spread the distal ends of the occluding members away from each other as they press against their respective tubes. In a preferred option, a main spring urges the spreading element toward the distal ends of the occluding elements into an occluding position. The spreading element may be moved against the biasing force of the main spring into a non-occluding position near the proximal ends of the occluding elements either manually through a button and linkage assembly coupled to the spreading element, or by control of a controller activating an actuator that is also coupled to the spreading element. A hinged door may be configured to cover the occluding elements and their respective sections of tubing. Activation of the actuator may be prevented if the door is not properly closed over the occluding elements. Optionally, a retention element to hold the spreading element in a non-occluding position may be enabled when the door is in an open position. Enabling the retention element allows the spreader to be held in a non-occluding position without continued application of force by a user on the button or by continued activation of the actuator. The retention element may be disabled when the door is closed, so that the spreading element may be free to be moved into and out of an occluding position, either manually or via the actuator. 
         [0024]      FIGS. 1 and 2  show exploded, perspective views of an occlusion assembly  700  in accordance with an embodiment of the present disclosure.  FIG. 1  shows an exploded, perspective view of the occlusion assembly  700  from a front angle and  FIG. 2  shows an exploded, perspective view of the occlusion assembly  700  from a back angle. 
         [0025]    The occlusion assembly  700  receives a pair of tubes  705  and is configured to occlude the tubes  705  using a pinching action at approximately the same level along the length of assembly  700 . The pinching action reduces the size of an inner fluid pathway of each tube  705  to restrict the flow of fluid therethrough. The occlusion assembly  700  may be used with an infusion pump, in a dialysis machine, in hemodialysis, in peritoneal dialysis, in hemofiltration, in hemodiafiltration, in intestinal dialysis, and the like. 
         [0026]    The occlusion assembly  700  includes a frame  701 . In some embodiments, the frame  701  includes tabs or snaps  709  for securing the frame to corresponding slots on a front panel of a blood filtration device, such as a hemodialysis apparatus. 
         [0027]    The frame  701  includes anvils or blocks  702  and  703  against which a tube  705  is compressed by the occluding ends  713  of a pair of occluding arms  710  and  711 , and a tube guide  704  to position each tube  705  against blocks  702  and  703 . The tube guide  704  and blocks  702  and  703  are configured to each position a tube  705  in a predetermined position adjacent to each of the blocks  702  and  703 . The occlusion assembly  700  also includes a door  706  which is pivotally mounted to the frame  701 . The door  706  can shut against the frame  701  to secure the tubes  705  between each of the blocks  702  and  703  and the tube guide  704 . The door  706  includes a latch  707 , which may be co-molded with or otherwise attached to the door  706  via a hinge, such as for example a resilient, flexible base portion (e.g., via a living hinge)  708  to secure the door  706  to the frame  701  in a closed position. As shown in  FIGS. 1 ,  3 , and  4 , a latch  707  may be pressed laterally to release a catch  740  from engagement with a corresponding slot  741  on frame  701  to open the door  706 . 
         [0028]    The occlusion assembly  700  includes two arms  710  and  711 . The first arm  710  includes a pivoting end  712  and an occluding end  713 ; likewise, the second arm  711  includes a pivoting end  714  and an occluding end  715 . The two arms  710  and  711  operate together to occlude the tubes  705  when a manual actuator, such as button  716 , is released (or in other embodiments engaged) and door  706  is closed, or when an actuator  717  is deactivated 
         [0029]      FIG. 3  shows a front, perspective view of the occlusion assembly  700  with the door  706  open and the button  716  pressed to illustrate release of occluding arms  710  and  711  to permit loading and unloading of the tubes  705  in accordance with an embodiment of the present disclosure.  FIG. 5  shows the front of the occlusion assembly  700  of  FIG. 1  without the door  706  and frame  701  to illustrate the arms  710  and  711  fully occluding the tubes  705   a, b  in accordance with an embodiment of the present disclosure. As shown in  FIG. 5 , a wedge element or spreader  722  contacts the facing sides of occluding arms  710  and  711 , which under spring force can apply pressure to occluding arms  710  and  711  to press the occluding ends  713  and  715  of occluding arms  710  and  711  against a portion of tubes  705   a, b . A user may release the occluding arms  710  and  711  by pressing button  716 , which causes spreader  722  to withdraw away from occluding arms  710  and  711 , releasing the pressure of spreader  722  being applied to the distal ends of occluding arms  710  and  711 . In some aspects, the manual actuator (e.g. button  716 ) acts as an override mechanism to an automated actuator (such as, for example, a pneumatically operated piston/cylinder apparatus) connected to a tubing occluder element (e.g., the spreader  722 ). The manual actuator is operatively coupled to the tubing occluder to cause essentially linear motion of at least a portion of the tubing occluder, moving the occluding member from an occluding position to a non-occluding position upon manual operation of the override mechanism by a user. 
         [0030]    Similarly, activation of an actuator may release occluding arms  710  and  711  by causing spreader  722  to withdraw away from the occluding ends  713 ,  715  of occluding arms  710  and  714 . In one embodiment, as shown in  FIG. 1 , spreader  722  may be formed of, co-molded with, attached to or connected to a carriage assembly  723 , which in turn is connected to an actuating arm of the actuator (see, e.g.,  FIGS. 7-9 ). The actuator may comprise, for example, a motor and gear assembly (e.g., rack and pinion assembly or worm-type gear assembly), a solenoid, a hydraulic cylinder or a pneumatic cylinder, among others. In a preferred embodiment, the actuator comprises a pneumatic cylinder  717  that causes an actuating arm comprising a piston arm  742  to extend linearly against a spring force (which in an embodiment may be a coil spring  745  within cylinder  717  as shown in  FIG. 11 ). As shown in  FIG. 11 , in a perspective side view of a pneumatically operated linear actuator  717 , piston arm  742  is connected to carriage  723 . When activated by pneumatic pressure, actuator  717  extends piston arm  742  and moves carriage  723  and attached spreader  722  in a direction that withdraws spreader  722  from engagement with the distal ends  713 ,  715  of the occluding arms  710  and  711 . (For clarity, occluding arm  711 , frame  701 , door  706 , block  703  and tube guide  704 , among other elements, have been removed from  FIGS. 9-11 ). Preferably, a main spring that is either external or internal to cylinder/actuator  717  may apply a biasing force to piston arm  742  or carriage  723  to cause spreader  722  to move occluding arms  710  and  711  to an occluding position. In the event of a loss of power or pneumatic pressure, the occluding arms  710  and  711  will default to an occluding mode, preventing the flow of fluid through tubes  705 . As illustrated in a cross-sectional view of occlusion assembly  700  in  FIG. 11 , in an embodiment, a coil spring  745  may be placed within the cylinder  743  to provide a biasing force against which piston  744  may move piston arm  742  under pneumatic pressure. Pneumatic pressure may be supplied to linear actuator  717  from a pressure source (e.g., a tank pressurized by a pump) regulated by an intervening electromechanical valve under control of an electronic controller. 
         [0031]    As shown in  FIGS. 5 and 10 , when the linear actuator  717  is fully retracted, the carriage  723  carries spreader  722  along the facing sides of the occluder arms  710  and  711  to rotate them into an occluding position. The first arm  710  pivots about its pivoting end  712  to cause the occluding end  713  to press against first tube  705   a  that is restrained by block  702  (see  FIG. 5 ). The second arm  711  pivots about its pivoting end  714  such that the occluding end  715  can press against second tube  705   b  which is restrained by block  703 . 
         [0032]      FIGS. 6 and 9  show occlusion assembly  700  in a non-occluding state (frame  701 , door  706 , blocks  702 ,  703 , and other elements removed for clarity). When the button  716  is pressed or the linear actuator  717  is activated, the carriage  723  and attached spreader  722  move distally away from the actuator  717 , allowing occluder arms  710  and  711  to rotate about pivot points  712  and  714  into a non-occluding position. The elastic resilience of the tubes  705   a.b  may cause the arms  710  and  711  to pivot towards each other. In some embodiments of the present disclosure, small magnets (not explicitly shown) embedded in the arms  710  and  711  pull the arms  710  and  711  towards each other to facilitate the retraction of the occluding ends  713  and  715  away from the tubes  705 . In other embodiments, small springs (not shown) may bias occluding arms  710  and  711  to pivot toward each other, the spring constants being weak enough to be overcome by the main spring (e.g., spring  745 ) biasing carriage  723  or spreader  722  into retracted (occluding) positions. 
         [0033]      FIG. 4  shows a perspective side view of the occlusion assembly  700  of  FIG. 1  (frame  701  removed for clarity) showing the door  706  engaging a switch  720  when the door  706  is closed in accordance with an embodiment of the present disclosure. As shown in  FIG. 4 , the hinge portion  708  of latch  707  is coupled to an engagement member or catch  740  that can snap into a cooperating slot  741  of the frame  701  (see, e.g.,  FIGS. 1 and 3 ). As the door  706  is closed, a portion of the catch  740  of latch  707  of the door  706  engages a spring-loaded switch  720 , which in an embodiment includes a spring arm  737  of the switch  720 . 
         [0034]    Engagement of switch  720  by closure of door  706  signals an electronic controller (not shown) that the door  706  is properly closed, and that linear actuator  717  may be activated to release occluders  710  and  711  to allow fluid to flow through tubes  705 . The door  706  closure signal may also cause the controller to perform other functions, such as, for example, instructing a pump coupled to the tubes  705  to begin pumping fluid within tubes  705 . 
         [0035]      FIG. 7  shows the back of the occlusion assembly  700  of  FIG. 1  with the linear actuator  717  in a fully retracted position (i.e., in the occluding position) in accordance with an embodiment of the present disclosure.  FIG. 7  shows the back side of the occlusion assembly  700  in the same configuration as shown for the front view of occlusion assembly  700  in  FIG. 5 .  FIG. 7  shows several working parts of the occlusion assembly  700  of  FIG. 1  to illustrate the operation of the actuator  717  and carriage  723  in accordance with an embodiment of the present disclosure. The carriage  723  moves with the extension or retraction of the piston arm  742  or with the actuation of the button  716 . The carriage  723  includes guides  724  attached to or co-molded with the carriage  723 . The guides  724  guide the carriage  723  as it moves via actuation of the piston arm  742  or with the actuation of the button  716 . The guides  724  interface with tracks  725  of the frame  701  (see, e.g.,  FIG. 2 ). 
         [0036]    In an optional embodiment, when door  706  is open, actuation of button  716  by a user or activation of actuator  717  by a controller causes carriage  723  and spreader  722  to move into a non-occluding position, and a retaining element or assembly allows the non-occluding position to be held without further force being applied either by the user or by the actuator  717 . In an exemplary embodiment shown in  FIG. 7 , the carriage  723  may incorporate a latching pin  726  to cooperate with a slot or hole in a retention member  718 . The retention member  718  includes a surface  727  positioned to be contacted by pins  738  located on the inside of door  706  when it is closed (see, e.g.,  FIGS. 2 and 3 ). Through holes  739  (see, e.g.  FIGS. 1 and 3 ) allow pins  738  to contact a portion of retention member  718  to displace it in a rearward direction. In the illustrated embodiment, pins  738  contact front plate  727  of retention member  718 . Retention member  718  also includes a surface having a slot or hole  729  positioned to receive the head of a latching pin  726 , which in the illustrated embodiment comprises a horizontal plate  728  defining a receiving portion  729 . Retention member  718  is arranged to slide within grooves or guides of the frame  701  (not shown) in response to contact by the pins  738  when the door  706  is closed or opened (see, e.g.  FIG. 2 ). A spring  730  mounted on the frame  701  may be biased to urge the retention member  718  forward to a stop feature (not shown) on the frame  701  so that opening the door  706  allows the retention member  718  to slide forward, re-aligning the receiving portion  729  in relation to the latching pin  726 . When the door  706  is closed (see  FIG. 1  or  2 ), the pins  738  on the door  706  press against the front plate  727  which compresses the spring  730  such that the receiving portion  729  of the horizontal plate  728  is positioned directly over the latching pin  726 . Upon alignment of the receiving portion  729  with the latching pin  726 , the area of the receiving portion  729  is large enough to allow the latching pin  726  to be released by the retention member  718 , thereby allowing the carriage  723  to be subject to the spring force of the main spring  745  in the actuator  717 . If pneumatic pressure is not then being applied to the actuator  717 , the carriage  723  is then free to move into an occluding position. The retention member  718  in the disabled state (i.e., inoperative state) allows the latching pin  726  to move freely through the receiving portion  729  as the carriage  723  moves between the fully extended position and the fully retracted position. 
         [0037]      FIG. 8  is a rear view of the occlusion assembly  700  with the actuator  717  activated, and the piston arm  742  in an extended position to place the occluding arms  710 ,  711  in a non-occluding state. In this view, the head of the latching pin  726  is noted to be above the plane of the horizontal plate  728  of the retention member  718 , and the recessed region  731  of the latching pin  726  is noted to be aligned with the receiving portion  729  of the retention member  718 . In this illustration, door  706  is in a closed position, implying that the receiving portion  729  is in a sufficiently rearward position to prevent the latching pin  726  from being latched into the retention member  718 . 
         [0038]    When the door  706  is sufficiently opened, the pins  738  of the door  706  do not press against the front plate  727  and the spring  730  applies a force on the front plate  727  such that the receiving portion  729  of the retention member  718  is positioned to allow the latching pin  726  to engage an edge of the receiving portion  729  and latch to the retention member  718 . The latching pin  726  moves into the receiving portion  729  pulling the front plate  727  rearward against the force of the spring  730  when the receiving portion  729  is positioned to latch to the latching pin  726 . When the head of latching pin  726  moves sufficiently through the receiving portion  729 , a recessed region  731  below the head of latching pin  726  becomes co-aligned with the horizontal plate  728  which moves as the edge of the receiving portion  729  moves into the recessed region  731  under the force of the spring  730  as applied to the front plate  727 . When the pins  738  of the door  706  sufficiently engage the front plate  727 , the receiving portion  729  is positioned to release the latching pin  726  from the latch  718 . Thus, when the door  706  is open, the carriage  723  and spreader  722  can be held in a non-occluding position without the continuous application of force by the actuator  717  or by a user pressing against the button  716 . This permits a user to load and unload tubing from occlusion assembly  700  without simultaneously having to apply force on the button  716 . However, upon the closing of the door  706 , the retention member  718  is no longer operative, and in the absence of continued application of force by either the actuator  717  or through the button  716 , the carriage  723  and spreader  722  will move into a position to cause the occluding arms  710  and  711  to rotate to an occluding position. 
         [0039]      FIGS. 9 and 10  show a side perspective view of several working parts of the occlusion assembly  700  of  FIG. 1 , with frame  701 , blocks  702 ,  703 , tube guide  704 , door  706 , occluding arm  711  and other parts removed for clarity. In  FIG. 9 , the piston arm  742  is fully extended in accordance with an embodiment of the present disclosure.  FIG. 9  shows the latching pin  726  latched onto the retention member  718 . That is, assuming that door  706  is in an open position, the horizontal plate  728  is positioned by the force of spring  730  to engage the recessed region  731  of the latching pin  726 . 
         [0040]      FIG. 10  shows a side, perspective view of the occlusion assembly  700  of  FIG. 1  with the piston arm  742  in a fully retracted position, with certain elements removed as in  FIG. 9  for clarity. In this example, the latching pin  726  is shown to be completely disengaged from the retention member  718 ; and in the absence of an activating force on the actuator  717  or a pressing force on the button  716 , the piston arm  742 , carriage  723  and spreader  722  are free to retract under the force of a main spring  745  (see  FIG. 11 ) biased against the extension of piston arm  742 . The spreader  722  then moves toward the occluding ends  713 ,  715  of the occluding arms  710 ,  711 . In an embodiment, as shown in  FIGS. 9 and 10 , the button  716  pivots about a pivot  732  to raise a lever arm  733  when the button  716  is pressed. The lever arm  733  is pivotally connected to a connecting member  734  via a proximal pivot  735 . The connecting member  734  in turn is pivotally connected to the carriage  723  via a distal pivot  736 . When the button  716  is pressed or the piston arm  742  moves the carriage  723  toward the retention member  718 , the connecting member  734  moves with the carriage  723 , rotating the button  716  about the pivot  732  as shown in  FIG. 9 . 
         [0041]      FIG. 12  shows the occlusion assembly  700  of  FIG. 1  used in a front-panel assembly  911  of a dialysis system in accordance with an embodiment of the present disclosure. The occlusion assembly  700  occludes flexible tubes  901 ,  902  through which blood flows to and from a patient. The right side tube  902  carries blood from a patient into a blood pump assembly  1000  and the left side tube  901  carries blood from a dialyzer  14  back to the patient after passing through an air trap  19 . The occlusion assembly  700  can occlude the flow of blood through both of these patient tubes  801 ,  802  simultaneously. 
         [0042]    The tubes  901 ,  902  are connected to a blood pump cassette or assembly  1000 . The blood pump cassette  1000  is a modular unit that may be mounted onto and dismounted from the front-panel assembly  911 . Both of the patient tubes  901 ,  902  may be provided as an assembly with the blood pump cassette  1000  and air trap  19 , and may be loaded into the occlusion assembly  700  when the blood-pump cassette  1000  is mounted onto the front-panel assembly  911 . In this embodiment, the occlusion assembly  700  forms a permanent part of the front panel assembly  911 . 
         [0043]    When the occlusion assembly  700  is in the non-occluding state, pumps located on blood pump cassette  1000  may be activated to pump blood from a patient through the right tube  902 , up through the blood pumps and through a dialyzer  14 . Blood processed by the dialyzer  14  then returns to the patient via tube  901  after first passing through an air trap  19  and an air-in-line detector  823 . 
         [0044]    While several embodiments of the invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and structures for performing the functions and/or obtaining the results or advantages described herein, and each of such variations, modifications and improvements is deemed to be within the scope of the present invention. More generally, those skilled in the art would readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that actual parameters, dimensions, materials, and configurations will depend upon specific applications for which the teachings of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described. The present invention is directed to each individual feature, system, material and/or method described herein. In addition, any combination of two or more such features, systems, materials and/or methods, provided that such features, systems, materials and/or methods are not mutually inconsistent, is included within the scope of the present invention.