Abstract:
An apparatus for selecting a flow rate of a fluid includes a barrel including an output port and a plurality of input ports; and an axle disposed substantially concentrically within the barrel. A plurality of drain channels are formed in an outer surface of the axle, each drain channel having a depth less than a thickness of a wall of the axle. The axle is rotatable within the barrel to provide one of a plurality of flow paths between one of the plurality of input ports and the output port, each flow path at least partially defined by at least one of the drain channels.

Description:
BACKGROUND 
     A flow selector regulates the flow rate of a fluid from a source, e.g., a fluid pump, to a final receiving point, e.g., a patient, through one or more fluid-carrying channels, e.g., polyvinyl chloride (PVC) or silicone-based tubes. In the context of a patient receiving medication, a flow selector allows for adjustment of the dose of medication as deemed appropriate during therapy. Flow selectors have been used in conjunction with fluid pumps that have fixed rates of flow output. 
     SUMMARY 
     In a general aspect, an apparatus for selecting a flow rate of a fluid includes a barrel including an output port and a plurality of input ports; and an axle disposed substantially concentrically within the barrel. A plurality of drain channels are formed in an outer surface of the axle, each drain channel having a depth less than a thickness of a wall of the axle. The axle is rotatable within the barrel to provide one of a plurality of flow paths between one of the plurality of input ports and the output port, each flow path at least partially defined by at least one of the drain channels. 
     Embodiments may include one or more of the following. 
     The axle is formed of a plurality of axle segments, each axle segment having a different radius. 
     The barrel is formed of a plurality of barrel segments, each barrel segment having a different radius, each barrel segment corresponding to one of the plurality of axle segments. An outer surface of each of the plurality of axle segments is in contact with an inner surface of the corresponding one of the plurality barrel segments. At least one gap is present between the axle and the barrel, each gap located at a boundary between one of the plurality of barrel segments and an adjacent one of the plurality of barrel segments. At least one of the plurality of flow paths is further defined by the at least one gap. A drain cavity is formed in the inner surface of at least one of the plurality of barrel segments, at least one of the plurality of flow paths further defined by the drain cavity. Each barrel segment corresponds to one of the plurality of input ports 
     The plurality of drain channels are formed in an outer surface of the plurality of axle segments. Each flow path is defined by no more than one drain channel on each of the plurality of axle segments. 
     The flow rate of the fluid is selected by rotating the axle to a position such that at least one of the plurality of drain channels is aligned with at least one of the plurality of input ports. The flow rate of the fluid comprises the sum of the flow rates of the fluid through the at least one of the plurality of input ports aligned with the at least one of the plurality of drain channels. 
     The apparatus further includes a control knob configured to rotate the axle. The control knob includes a plurality of position identifiers, each position identifier corresponding to one of the plurality of flow paths. The control knob is removable, and wherein rotation of the axle is prohibited after removal of the control knob. 
     The number of flow paths is 2 N −1, where N is the number of input ports. 
     At least some of the plurality of flow paths correspond to different flow rates. 
     The barrel includes a groove configured to receive a stabilizer ring formed on the outer surface of the axle. 
     The flow selector described herein has a number of advantages. Without apertures or holes in the axle, the tooling needed to fabricate the flow selector can be significantly simplified. This simplicity reduces manufacturing cost and/or allows a large number of flow rate combinations to be incorporated into a single device. In cases where a specific flow rate cannot be derived from the combinations of flow rates already available from the fixed number of inlet ports in a particular device, additional inlet ports can be added without presenting significant technical difficulties in the fabrication of the new inlet ports. As new drugs are introduced that require new doses, this flexibility frees the user from the restrictions of adjusting doses to fit into fixed flow rate pumps. In addition, the flow selector can be packaged in a compact, user-friendly design. 
     Other features and advantages of the invention are apparent from the following description and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  are a perspective view and a side view, respectively, of a flow selector. 
         FIG. 2  is a view of a case for a flow selector. 
         FIG. 3A  is a schematic diagram of the barrel of a flow selector. 
         FIG. 3B  is a cross-sectional side view of the barrel of  FIG. 3A . 
         FIG. 3C  is a longitudinal cross-sectional view of the barrel of  FIG. 3A . 
         FIG. 4  is a schematic diagram of the axle of a flow selector. 
         FIG. 5  is a cross-sectional top view of a flow selector. 
         FIGS. 6A-6D  are schematic diagrams of flow paths through a flow selector. 
         FIGS. 7A and 7B  are schematic diagrams of an exemplary flow path involving one input port. 
         FIGS. 8A and 8B  are schematic diagrams of an exemplary flow path involving two input ports. 
         FIGS. 9A and 9B  are schematic diagrams of an exemplary flow path involving three input ports. 
         FIGS. 10A and 10B  are schematic diagrams of an exemplary flow path involving two input ports. 
         FIGS. 11A and 11B  are schematic diagrams of an exemplary flow path involving one input port. 
         FIGS. 12A and 12B  are schematic diagrams of an exemplary flow path involving one input port. 
         FIGS. 13A and 13B  are schematic diagrams of an exemplary flow path involving two input ports. 
         FIGS. 14A and 14B  are schematic diagrams of an exemplary flow path involving no input ports. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1A and 1B , a flow selector  10  combines fluid (e.g., a medical fluid such as a drug) arriving from multiple input ports  21 ,  22 ,  23  into a single output port  24 . The flow rate of fluid exiting from output port  24  is controlled by the internal configuration of flow selector  10 , which can be set by turning a control knob  51  at one end of the flow selector. 
     The input ports  21 ,  22 ,  23  are coupled to fluid sources  21   a ,  22   a ,  23   a , respectively. The fluid sources may be, e.g., tubes each with a different flow restrictor, such as different lumen tubes or glass capillaries with varying orifice sizes. Input ports  21 ,  22 ,  23  and output port  24  can be positioned at any position around the flow selector; the positions of the ports are not limited to the configuration shown in the figures. Referring to  FIG. 2 , the components of flow selector  10  are enclosed in a case  11  that provides a compact, user-friendly design. 
     Referring to  FIGS. 3A-3B , flow selector  10  includes a hollow barrel  12  formed of three stepped sections  27 ,  28 ,  29 . Each stepped section  27 ,  28 ,  29  connects to one of the input ports  21 ,  22 ,  23 , respectively. Referring also to  FIG. 3C , grooves  36 ,  37  corresponding to stepped sections  27 ,  28 , respectively, are formed around about one-quarter of the circumference of barrel  12 . The remaining three-quarters of the circumference of the barrel are in substantial interference contact with the outside edge of an axle disposed within the barrel (axle  40  in  FIG. 4 , discussed below) in order to prevent fluid leakage. Grooves  36  and  37  are in perpetual fluid communication with drain cavities  30 ,  31 , respectively, formed in stepped barrel sections  28  and  29 . 
     Referring also to  FIG. 4 , a stepped axle  40  is disposed within hollow barrel  12 . Stepped axle sections  41 ,  42 ,  43  nest within stepped barrel sections  27 ,  28 ,  29 , respectively. To ensure leak-proof contact between axle  40  and barrel  12 , a stabilizer ring  44  on axle  40  fits snugly within an annular groove  35  (see  FIG. 3B ) on the interior surface of barrel  12 . The axle and barrel are both formed of materials that minimize leakage and facilitate rotation of the axle with minimal binding. The barrel is generally constructed from hard plastics such as Acrylonitrile Butadiene Styrene (ABS) or polycarbonate, while the axle is of material with lubricating characteristics on its surface like high-density polyethylene (HDPE) or polyethylene (PE). 
     Longitudinal drain channels are formed in each stepped axle section  41 ,  42 ,  43 . For instance, stepped axle section  41  includes drain channels  61 ,  62 ,  63 , and  64 , each channel located at a different radial position around the circumference of the axle. Stepped axle section  42  includes drain channels  65 ,  66 ,  67 , and  68 ; and stepped axle section  43  includes drain channels  69 ,  70 ,  71 , and  72  (see also  FIGS. 6A-6D ). As discussed in greater detail below, axle  40  is rotatable within barrel  12  such that one or more of the drain channels can be aligned with a corresponding input port, allowing fluid to flow from the input port into the drain channel. 
     Referring also to  FIG. 5 , on barrel  12 , drain cavities  30 ,  31  are formed in stepped barrel sections  28  and  29 , respectively. Fluid received into the drain channels flows between the interior surface of barrel  12  and the exterior surface of axle  40  via drain cavities  30 ,  31 , to arrive at output port  24 . 
     On one end of axle  40 , a flow selector wheel  14  has position indicators  100 ,  101 ,  102 ,  103 ,  104 ,  105 ,  106 ,  107  disposed around its circumference. Each position indicator is aligned with a set of drain channels and corresponds to a different and unique flow rate of fluid through flow selector  10 , as discussed in greater detail below. Using knob  51  to rotate axle  40 , an operator can select the internal configuration of flow selector  10  that corresponds to a desired flow rate. In some embodiments, knob  51  is removable such that once a desired flow rate is selected, further rotation of axle  40  (and thus further adjustment of the flow rate) is disabled. 
     Referring to  FIGS. 6A-6D , axle  40  is shown from various perspectives to demonstrate the alignment between each position indicator on flow selector wheel  14  and the corresponding set of drain channels. When a given position indicator is selected using knob  51 , the corresponding set of drain channels is aligned with the lateral axis of input ports  21 ,  22 ,  23 , enabling each drain channel in the selected set to receive fluid from the corresponding input port. 
     For instance, referring to  FIG. 6A , position indicator  104  corresponds to a flow path involving only drain channel  61 , which receives fluid from input port  21 . Fluid in input ports  22  and  23  is not allowed to flow through flow selector  10  when position indicator  104  is selected. Position indicator  105  corresponds to a flow path involving drain channels  62  and  71 , which are in communication with input ports  21  and  23 , respectively. That is, by selecting position indicator  105 , the fluid flow rate through flow selector  10  would be equal to the combined fluid flow rate through input ports  21  and  23 . Position indicator  106  corresponds to a flow path involving drain channels  63  and  68 , which are in communication with input ports  21  and  22 , respectively. Referring now to  FIG. 6B , position indicator  102  enables a flow path involving only drain channel  66 , while position indicator  103  enables a flow path involving drain channels  65  and  72 . 
       FIG. 6C  shows that position indicator  101  enables a flow path involving only drain channel  69 . Position indicator  100  does not correspond to any drain channel; thus, selecting position indicator  100  effectively turns off the flow of fluid through flow selector  10 . In  FIG. 6D , it can be seen that position indicator  107  corresponds to a flow path involving drain channels  64 ,  67 , and  70 , which are in communication with all three input ports  21 ,  22 , and  23 , respectively. That is, position indicator  107  corresponds to a maximum flow rate through flow selector  10 . 
     Referring to  FIG. 7B , to facilitate fluid flow along flow selector  10  toward output port  24 , stepped barrel sections  27 ,  28 ,  29  precisely correspond to stepped axle sections  41 ,  42 ,  43 . However, at each transition between steps, a small gap form by the groove along the circumference of the barrel cavity and the edge of the axle is present through which fluid can flow. For instance, a first axle step gap  29   c  located at the transition between the largest stepped sections (stepped barrel section  27  and stepped axle section  41 ) and the medium-sized stepped sections (stepped barrel section  28  and stepped axle section  42 ) allows fluid to exit the drain channel on stepped axle section  41  and flow towards output port  24  via cavity  30 . The gap  29   c  is formed by the groove  36  and the stepped surface  41  of axle. A second axle step gap  30   c  is located at the transition between the medium-sized stepped sections (stepped barrel section  28  and stepped axle section  42 ) and the smallest stepped sections (stepped barrel section  29  and stepped axle section  42 ) and allows fluid to exit the drain channel on stepped axle section  42  via cavity  31 . The gap  30   c  is formed by the groove  37  and the stepped surface  42  of the axle. A third axle step gap  31   c  is located past stepped sections  29  and  43  and allows fluid to exit the drain channel on stepped axle section  43  and flow into output port  24  via cavity  32 . 
     Referring now to  FIGS. 7A and 7B , to illustrate the fluid flow path through flow selector  10 , an exemplary flow path corresponding to position indicator  104  is shown. As shown in  FIG. 6A , position indicator  104  allows fluid flow only from input port  21 ; no drain channel accepts fluid from input ports  22  or  23 . In this configuration, fluid arriving via input port  21  flows into drain channel  61  and into first axle step gap  29   c . From first axle step gap  29   c , the fluid flows into cavity  30 , via second axle step gap  30   c , through cavity  31 , into third axle step gap  31   c , and out of flow selector  10  via an output cavity  32  in output port  24 . Supposing input port  21  is connected to a tube with a 4 mL/hour flow rate, than output port  24  would deliver fluid at a flow rate of 4 mL/hour. 
     Referring to  FIGS. 8A and 8B , another exemplary flow path corresponding to position indicator  106  is illustrated. In this configuration, fluid is received from both input ports  21  and  22  but not from input port  23 . Fluid arriving via input port  21  flows into drain channel  63 , via first axle step gap  29   c  into cavity  30 , via second axle step gap  30   c  into cavity  31 , then through third axle step gap  31   c  and out of flow selector via output port  24 . Fluid arriving via input port  22  flows into drain channel  68 , via second axle step gap  30   c  and into cavity  31 , then through third axle step gap  31   c  and out of the flow selector via output cavity  32  in output port  24 . Supposing input port  21  is connected to a tube with a 4 mL/hour flow rate and input port  22  is connected to a tube with a 2 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 6 mL/hour. 
     Referring to  FIGS. 9A and 9B , another exemplary flow path corresponding to position indicator  107  is illustrated. In this configuration, fluid is received from all three input ports  21 ,  22 , and  23 . Fluid arriving via input port  21  flows into drain channel  64 , via first axle step gap  29   c  into cavity  30 , via second axle step gap  30   c  into cavity  31 , then through third axle step gap  31   c  and out of flow selector via output port  24 . Fluid arriving via input port  22  flows into drain channel  67 , via second axle step gap  30   c  and into cavity  31 , then through third axle step gap  31   c  and out of the flow selector via output port  24 . Fluid arriving via input port  23  flows into drain channel  70 , through third axle step gap  31   c , and out of the flow selector via output cavity  32  in output port  24 . Supposing input port  21  is connected to a tube with a 4 mL/hour flow rate, input port  22  is connected to a tube with a 2 mL/hour flow rate, and input port  23  is connected to a tube with 1 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 7 mL/hour. 
     Referring to  FIGS. 10A and 10B , another exemplary flow path corresponding to position indicator  105  is illustrated. In this configuration, fluid is received from input ports  21  and  23 . Fluid arriving via input port  21  flows into drain channel  62 , via first axle step gap  29   c  into cavity  30 , via second axle step gap  30   c  into cavity  31 , then through third axle step gap  31   c  and out of flow selector via output port  24 . Fluid arriving via input port  23  flows into drain channel  71 , through third axle step gap  31   c , and out of the flow selector via output cavity  32  in output port  24 . Supposing input port  21  is connected to a tube with a 4 mL/hour flow rate and input port  23  is connected to a tube with 1 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 5 mL/hour. 
     Referring to  FIGS. 11A and 11B , another exemplary flow path corresponding to position indicator  101  is illustrated. In this configuration, fluid is only received from input port  23 . From input port  23 , the fluid flows into drain channel  69 , through third axle step gap  31   c , and out of the flow selector via output cavity  32  in output port  24 . Supposing input port input port  23  is connected to a tube with 1 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 1 mL/hour. 
     Referring to  FIGS. 12A and 12B , another exemplary flow path corresponding to position indicator  102  is illustrated. In this configuration, fluid is only received from input port  22 . From input port  22 , the fluid flows into drain channel  66 , via second axle step gap  30   c  and into cavity  31 , then through third axle step gap  31   c  and out of the flow selector via output cavity  32  in output port  24 . Supposing input port  22  is connected to a tube with a 2 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 2 mL/hour. 
     Referring to  FIGS. 13A and 13B , another exemplary flow path corresponding to position indicator  103  is illustrated. In this configuration, fluid is received from input ports  22  and  23 . Fluid arriving via input port  22  flows into drain channel  65 , via second axle step gap  30   c  and into cavity  31 , then through third axle step gap  31   c  and out of the flow selector via output port  24 . Fluid arriving via input port  23  flows into drain channel  72 , through third axle step gap  31   c , and out of the flow selector via output cavity  32  in output port  24 . Supposing input port  22  is connected to a tube with a 2 mL/hour flow rate and input port  23  is connected to a tube with 1 mL/hour flow rate, then output port  24  would deliver fluid at a flow rate of 3 mL/hour. 
     Referring to  FIGS. 14A and 14B , when position indicator  100  is selected, none of the input ports  21 ,  22 , or  23  is aligned with a drain channel and there is no fluid flow through the flow selector. 
     In the embodiment described above, axle  40  includes eight position indicators corresponding to eight unique flow paths. However, the number of position indicators is not necessarily limited to eight, but varies depending on the number of input ports. In general, the number of combinations of input ports (and hence the number of unique flow paths) is 2 N −1, where N is the number of unique input ports. 
     Referring again to  FIG. 1A , in some embodiments, flow selector  10  may be configured in a reverse fashion such that port  24  acts as an input port that receives fluid from a fluid source  24   a  and ports  21 ,  22 , and  23  act as three separate output ports. In this case, the flow selector selects some or all of the ports  21 ,  22 ,  23  through which to output fluid. 
     It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the appended claims. Other embodiments are within the scope of the following claims.