Patent Publication Number: US-2020276403-A1

Title: Rotors for use in caustic environments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application No. 62/812,939, filed Mar. 1, 2019, the contents of which are hereby incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Operation of respiratory therapy systems such as positive airway pressure (PAP) devices, ventilators and other such systems, often require impellers operating at high rotational speeds in caustic environments. Such caustic environments may include corrosive fluids (e.g. ferrous material debris suspended in fluid a humidifier). Traditional impellers operating at high rotational speeds require balancing to ensure quiet operation and longevity of the components due to non-uniform forces caused by an unbalanced impeller. Balancing an impeller is a time consuming process that increases the manufacturing cost of an impeller. Furthermore, secondary assembly operations necessary in balanced systems significantly increase manufacturing costs of impeller assemblies due to the continual skilled handling needed to join and balance components. These secondary assembly operations are a source of assembly error and lead to a higher likelihood of failure due to inevitable human error. 
     Additionally, corrosive fluids in such caustic environments are destructive to metals or materials used to seal magnets within an impeller assembly. Such corrosive fluids may be present within respiratory therapy systems. Such fluids may prevent the operation of a wide range of rotor and impeller assemblies in respiratory therapy systems due to the corrosive effects and wear on components in continuous operation. 
     SUMMARY 
     Disclosed herein are approaches for addressing various of the problems and shortcomings of the state of the art, as identified above. More particularly, disclosed herein are assemblies and methods for providing a rotatable impeller assembly for pumping caustic fluids in a medical device. In the devices and methods described herein provide an impeller assembly with a sealed magnetic ring and physically locked structural components that prevent rotation of the magnetic ring. In the devices and methods described herein, an impeller magnet is sealed from external environments and corrosive fluids, the structural components of the assembly are locked in place, and the rotor is automatically balanced. The devices and methods described herein thus eliminate the need for periodic centering and balancing of the rotor, resulting in a streamlined manufacture and robust assembly, while providing for a more versatile rotor capable of being run in a broad range of fluids. 
     In one embodiment, there is provided a rotatable impeller assembly for pumping caustic fluid byproducts in a medical device. The assembly comprises a rotor comprising a rotor cup. The assembly also comprises an impeller having a rotor contacting surface and impeller blades. Additionally, the assembly comprises a magnetic ring seated within the rotor cup, the magnetic ring comprising a first contact surface that is configured to mate with an inner surface of the rotor cup, and a second contact surface that is configured to mate with the rotor contacting surface of the impeller, the magnetic ring thereby being locked in position by the inner surface of the rotor cup and the rotor contacting surface of the impeller so as to prevent any independent rotation of the magnetic ring relative to the rotor cup and the impeller while automatically balancing the rotor. Further, the rotor contacting surface of the impeller is attached to the rotor cup to hermetically seal the magnetic ring within the impeller assembly. 
     In another embodiment, there is provided a method of manufacturing an impeller assembly for pumping caustic fluid byproducts in a medical device, the impeller assembly comprising a rotor and an impeller. The method comprises providing a rotor cup and positioning an impeller onto the rotor cup, the impeller having a rotor contacting surface and impeller blades. The method then comprises seating a magnetic ring within the rotor cup, the magnetic ring comprising a first contact surface that is configured to mate with an inner surface of the rotor cup, and a second contact surface that is configured to mate with the rotor contacting surface of the impeller. Further, the method comprises locking the magnetic ring between the inner surface of the rotor cup and the rotor contacting surface of the impeller so as to prevent any independent rotation of the magnetic ring relative to the rotor cup and the impeller while automatically balancing the rotor. The method also comprises forming a seal between the impeller and the rotor cup thereby sealing the magnetic ring within the impeller assembly. 
     In certain implementations, the inner surface of the rotor cup comprises a continuous ridge that mates with a corresponding groove formed in the first contact surface of the magnetic ring, thereby locking the magnetic ring in a fixed position relative to the rotor cup. In some implementations, the continuous ridge comprises an O-ring. In other implementations, the magnetic ring comprises anti-rotation features to prevent the independent rotation of the magnetic ring relative to the rotor cup and the impeller. In certain implementations, the rotor contacting surface of the impeller comprises a tapered surface having at least one angle that complements at least one angle formed on the second contact surface of the magnetic ring, thereby locking the magnetic ring in a fixed position relative to the impeller. In some implementations, the impeller assembly is automatically centered and balanced once the magnetic ring is locked in a fixed position. 
     In other implementations, the hermetic seal locks the rotor, magnetic ring and impeller in position within the impeller assembly to prevent any independent rotation. In some implementations, the magnetic ring is formed by injection molding a slurry of plastic and magnetic material. In certain implementations, the rotor contacting surface of the impeller is attached to the rotor cup by spin welding or ultrasonic welding. In other implementations, the impeller is formed by overmolding a polymer material onto the rotor cup with the magnetic ring seated therein, the overmolding hermetically sealing the magnetic ring between the rotor cup and the impeller. In some implementations, wherein the impeller and rotor cup comprise polyphenylene sulfide (PPS). In certain implementations, the magnetic ring comprises neodymium. 
     In other implementations, the medical device comprises a respiratory therapy device. In some implementations, the respiratory therapy device is configured to deliver high velocity respiratory fluid to a patient. 
     Numerous examples are available for adapting and implementing the assemblies and methods described herein. For example, respiratory therapy devices may include Assist/Control Ventilation, Intermittent Mandatory Ventilation, Pressure Support Ventilation, Continuous Positive Airway Pressure (CPAP) treatment, Non-Invasive Positive Pressure Ventilation (NIPPV), and Variable Positive Airway Pressure (VPAP). The therapy is used for treatment of various respiratory conditions including Sleep Disordered Breathing (SDB) and Obstructive Sleep Apnea (OSA). However, the rotors described herein may be used in other applications such as vacuum applications (medical or otherwise), heart pumps, and irrigation systems, for example. 
     Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1A  shows an illustrative balanced rotatable impeller assembly for pumping caustic fluids in a medical device, according to an embodiment of the present disclosure; 
         FIG. 1B  shows an illustrative side-view of the rotatable impeller assembly of  FIG. 1A ; 
         FIG. 2  shows a cross-sectional view of the rotatable impeller assembly of  FIG. 1A  taken along the line A-A indicated in  FIG. 1B ; 
         FIG. 3  shows an illustrative magnetic ring of the rotatable impeller assembly of  FIG. 1A , according to an embodiment of the present disclosure; 
         FIG. 4  shows an illustrative rotor cup of the rotatable impeller assembly of  FIG. 1A , according to an embodiment of the present disclosure; 
         FIG. 5  shows an illustrative overmolded rotatable impeller assembly for pumping caustic fluids in a medical device, according to an embodiment of the present disclosure; and 
         FIG. 6  an illustrative flowchart of a method of manufacturing a rotatable impeller assembly according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     To provide an overall understanding of the assemblies and methods described herein, certain illustrative implementations will be described. Although the implementations and features described herein are specifically described for pumping caustic fluid byproducts in a medical device, it will be understood that all the components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to respiratory therapy devices, including low flow oxygen therapy, continuous positive airway pressure therapy (CPAP), mechanical ventilation, oxygen masks, Venturi masks, and Tracheostomy masks. Furthermore, it should be noted that while certain implementations are discussed herein within regards to manufacturing impeller assemblies, these various implementations may be used in various combinations to create respiratory therapy systems or other pumps. 
       FIG. 1A  shows a impeller assembly  100  according to an embodiment of the present disclosure.  FIG. 1B  shows a side view of the impeller assembly  100 . Impeller assembly  100  comprises an impeller  110  and a rotor  120 . Impeller  100  comprises a fluid facing surface  130  on which impeller blades  140  are formed. Impeller  110  may be coupled to the rotor  120  at a rotor contacting surface  135 . Impeller assembly  100  is rotatable about a central axis (not shown) that is perpendicularly orientated with respect to the surface  130  of the impeller  110  and runs through the entire assembly  100 . While the impeller  110  is illustrated as having radially symmetric blades  140 , any configuration of blades may be used within the scope of the present disclosure. Impeller  110  may also comprise holes  145  that extend straight through the assembly  100  for additional stability and balance during rotation. 
       FIG. 2  shows a cross-section  200  of the impeller assembly  100 , taken along the line A-A in  FIG. 1B . As mentioned, the impeller assembly comprises an impeller  110  coupled to a rotor  120 . As can be seen in more detail in  FIG. 2 , the rotor  120  comprises a magnetic ring  150  seated in a rotor cup  126 . The rotor cup  126  comprises a hollow central void  122  in which a ball bearing sits during rotation of the impeller assembly  100 . The magnetic ring comprises a first contact surface  152  that is configured to mate with the inner surface of the rotor cup  126 . By mate what is meant is that the first contact surface  152  aligns parallel with the inner surface of the rotor cup  126 . As shown in  FIG. 2 , the first contact surface  152  comprises a tapered or sloped surface that aligns with the geometry of the inner surface of the rotor cup  126 . The magnetic ring  150  also comprises a second contact surface  154  that is configured to mate with the rotor contacting surface  135  of the impeller  110 . As with the first contact surface  152 , the second contact surface  154  may be tapered or sloped and aligns with the rotor contacting surface  135  of the impeller  110 . 
     As can be seen the various sloped angles of the rotor contacting surface  135 , first contact surface  152  and second contact surface  154  of the magnetic ring  150 , and the inner surface of the rotor cup  126  ensure that the magnetic ring  150  is held in a fixed position when the impeller  110  and the rotor cup  120  sandwich the magnetic ring  150 . In some embodiments, the inner surface of the rotor cup  126  may be provided with a ridge  124  that mates with a corresponding groove in the first contact surface  152  of the magnetic ring  150 . In some embodiments, this ridge  124  may be implemented as an O-ring. In such embodiments, when the impeller  110  is brought into contact with the rotor  120 , the orientation of the first contact surface  152  and second contact surface  154  of the magnetic ring  150 , the rotor contacting surface  135 , and the groove  124  lock the position of the magnetic ring  150  thereby preventing the magnetic ring from independently rotating within the assembly. Such locking of the magnetic ring  150  ensure that the impeller assembly is balanced during operation (in a pump, for example). In some embodiments the impeller  110  and the rotor cup  126  may comprise polyphenylene sulfide (PPS). Once the impeller  110 , the rotor  120  and the magnetic ring  150  are in place as shown in  FIG. 2 , the assembly is subject to spin welding or ultrasonic welding to form a hermetic seal between the impeller  110  and the rotor  120  with the magnetic ring  150  encapsulated therebetween, thus protecting the magnetic ring  150  from caustic environments in which the impeller assembly  100  is made to operate. 
       FIG. 3  shows an exemplary magnetic ring  300  similar to ring  150  shown in  FIG. 2 . Magnetic ring  300  is formed by injection molding a slurry of plastic and magnetic material. In some embodiments, the magnetic material comprises neodymium. As can be seen in  FIG. 2 , the magnetic ring body  310  comprises a structure and geometry that complements that of the inner surface of the rotor cup  126  and the rotor contacting surface  135  of the impeller  110 . Here the top surface  320  of the magnetic ring  300  mates with the rotor contacting surface  135  of the impeller  110  (tapered surfaces not shown). Similarly the bottom surface  330  of the magnetic ring  300  mates with the inner surface of the rotor cup  126 . Additionally, as shown in  FIG. 3 , as an alternative to tapered surfaces shown in  FIG. 2 , anti-rotation features  340 - 342  may be formed on the top surface  320  of the magnetic ring  300 . Such features  340 - 342  may include dimples or etched depressions on the top surface  320  of the magnetic ring  300 . These anti-rotation features  340 - 342  may be coupled with corresponding features formed on the rotor contacting surface  135  of the impeller  110 . Such coupling ensures that when the impeller assembly rotates, the magnetic ring  300  is held in a fixed position within the assembly without independently rotating. Minimizing such rotation ensures that the impeller assembly is balanced during operation. 
       FIG. 4  shows an exemplary rotor cup  400  similar to cup  126  shown in  FIG. 2 . The rotor cup  400  comprises a cup body  410  having an inner surface  420 . As mentioned in relation to  FIG. 2 , the inner surface of the rotor cup  420  has a geometry (slope and taper) that matches that of the first contact surface  152  of the magnetic ring  150 . In some embodiments, the inner surface  420  of the rotor cup  400  may comprise a ridge  430  (such as an O-ring, for example) which locks the position of the magnetic ring when seated in the rotor cup  400 . 
       FIG. 5  shows a cross-section of a further exemplary embodiment an impeller assembly  500  according to the present disclosure. The impeller assembly  500  comprises an impeller  510  coupled to a rotor  520 . A magnetic ring  550  is seated within the rotor  520 , as has been described in relation to  FIG. 2 . The rotor  520  comprises a hollow central void  540  in which a ball bearing sits during rotation of the impeller assembly  500 . The impeller assembly  500  may also comprise holes  545  that extend straight through the assembly  500  for additional stability and balance during rotation. In  FIG. 5 , the impeller  510  is formed by overmolding a polymer material, such as PPS (for example), over the rotor  520  and magnetic ring  550 . Such overmolding enables the rotor contacting surface  530  of the impeller  510  to conform to the features of the magnetic ring  550 . Such features may include the anti-rotation features  340 - 342  in  FIG. 3 . Impeller blades  540  are formed on the fluid contacting surface of the impeller  510 . Overmolding the impeller  510  also forms a hermetic seal with the rotor cup  520  thereby sealing the magnetic ring  550  within the impeller assembly  500 . Such a hermetic seal ensures that the magnetic ring  550  is isolated from any caustic environment to which the impeller assembly  500  is exposed. 
       FIG. 6  illustrates an exemplary method  600  of manufacturing an impeller assembly, such as any of the impeller assemblies, and internal components thereof, as described in the foregoing description, according to an embodiment of the present disclosure. The method  600  begins at step  610  in which a rotor cup is provided. Exemplary rotor cups  126 ,  400  and  520  have been described in the foregoing in relation to  FIGS. 2, 4 and 5 . A magnetic ring is then provided within the rotor cup after which an impeller is positioned onto the rotor cup containing the magnetic ring (step  620 ). Exemplary magnetic rings  150 ,  300  and  550  have been described in the foregoing in relation to  FIGS. 2, 3 and 5 . Next, in step  630 , once the impeller is positioned, the assembly is compressed so as to fixedly seat the magnetic ring within the assembly structure. Features such as the O-ring and tapered surfaces that have been described in the foregoing facilitate such fixed arrangement of the magnetic ring. Once seated, the magnetic ring is locked in place within the impeller assembly and is prevented from independently rotating within the rotor cup (step  640 ). In step  650 , a hermetic seal is formed between the impeller and the rotor so as to encapsulate the magnetic ring within the impeller assembly. Such a hermetic seal may be achieved by spin welding or ultrasonic welding. For embodiments in which the impeller is overmolded onto the rotor, the hermetic seal is automatically formed with the overmolding process. 
     The foregoing is merely illustrative of the principles of the disclosure, and the apparatuses can be practiced by other than the described implementations, which are presented for purposes of illustration and not of limitation. It is to be understood that the apparatuses disclosed herein, while shown for use in high flow therapy systems, may be applied to systems to be used in other ventilation circuits. 
     Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented. 
     Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.