Abstract:
Various blood pumps and methods of manufacture therefor are disclosed. An embodiment of a blood pump comprises a blood-flow lumen having an inlet and an outlet, and a rotor within the blood-flow lumen, the rotor having an impeller for pumping blood through the blood pump. A motor is also provided including a plurality of magnetic poles carried by the rotor, and a stator including a plurality of electrically conductive coils adjacent to and at least partially surrounding the blood-flow lumen. An over-molded monolithic enclosure covers the stator, the enclosure at least partially sealingly enclosing the stator and encasing the blood-flow lumen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/911,852, filed Dec. 4, 2013, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Various blood pumps are known for pumping the blood of a patient to provide assistance to his/her ailing heart. Particularly, implantable, magnetically driven, rotary ventricular assist devices (VADs) are blood pumps which may, if desired, be implanted in the patient to provide assistance in pumping blood for hearts that are afflicted with congestive heart failure or the like. 
     Axial flow pumps for blood have the advantage of narrow width, as compared to radial flow pumps. Typically, an axial flow pump has a cylindrical housing with an inlet, an outlet, and a rotor within the housing having impeller blades attached to the rotor. A set of electrical coils is disposed around the housing to provide a rotating magnetic field which spins the rotor. As the rotor rotates, the impeller blades propel the fluid (e.g., blood) through the inlet of the pump and out of the outlet. Radial flow pumps, such as the HVAD® pump of HeartWare, Inc., the Applicant, also have applicability in pumping blood for patients afflicted with congestive heart failure or the like. 
     Known axial flow pumps for blood have typically been made of suitable biocompatible metals, such as titanium. Generally, the pump is not inherently sealed. Stated another way, pumps of the prior art typically include separate components that require sealing (e.g., through the use of O-rings or other sealing devices) to attempt to establish a sealed environment around the coils. An example of such a prior art pump is shown in  FIGS. 5A-C . Joining of components is not always fully effective and is, in some cases, subject to failure. In addition, the multitude of components makes for a difficult and expensive assembly of the pump since there are multiple seal points to establish. 
     In particular reference to the pump  120  of  FIGS. 5A-C , as can be seen the pump includes a variety of components that require assembly. For instance, as shown in  FIG. 5C , the pump includes upper and lower volute portions  130 ,  132 , a metal casing  134 , a tubular housing  136 , a stator  138 , and a rotor  140 . Various sealing rings  142  are also provided. In its assembled form as shown in  FIGS. 5A-B , the various parts mentioned above must be pieced together and, in many cases, certain parts are adhered or connected together in some manner. For instance, stator  138  is adhered to tubular housing  136  and an epoxy backfill is used to secure stator  138  to metal casing  134  during assembly. Further, sealing rings  142  are utilized in an effort to create a sealed environment for pump  120 . Assembly of pump  120  therefore requires a number of pieces and occupies time and effort to ensure pump  120  operates in a sealed environment. 
     BRIEF SUMMARY OF THE INVENTION 
     A first aspect of the present invention includes a blood pump comprising a pump housing having a chamber with an inlet and an outlet, a rotor within the chamber of the pump housing, the rotor having an impeller for pumping blood through the blood pump, a motor including a plurality of magnetic poles carried by the rotor, and a stator including a plurality of electrically conductive coils adjacent to and at least partially surrounding the pump housing. The blood pump includes an over-molded monolithic enclosure covering the stator, the enclosure and the pump housing cooperatively sealingly enclosing the stator. In some embodiments, the enclosure directly contacts the pump housing at various contact points, thereby securing the pump housing relative to the enclosure. Also, the enclosure may be composed of a biocompatible polymer. 
     A second aspect of the present invention includes a method of manufacturing a blood pump comprising the steps of positioning a stator within a mold, the stator including a plurality of electrically conductive coils for interacting with a rotor, and molding an enclosure around the stator while in the mold so that the enclosure at least partially sealingly encloses the stator and borders a blood-flow lumen of the pump. As with above, the enclosure may be composed of a biocompatible polymer. In embodiments of this second aspect, the stator is sealed off from the flow of blood through the blood pump by molding the enclosure around the stator in the manner described. Thus, the stator can operate freely without contact from possibly harmful fluids that might damage the stator. In an embodiment, the step of molding the enclosure includes molding the enclosure around the stator so that the enclosure forms a unitary part with the stator. 
     A third aspect of the present invention includes a blood pump comprising a structure having a monolithic molded enclosure, the structure defining a blood-flow lumen having an inlet and an outlet, a rotor within the blood-flow lumen, the rotor having an impeller for pumping blood through the blood pump, a motor including a plurality of magnetic poles carried by the rotor, and a stator including a plurality of electrically conductive coils adjacent to and at least partially surrounding the blood-flow lumen, wherein the molded monolithic enclosure covers the stator, the enclosure at least partially sealingly enclosing the stator and encasing the blood-flow lumen. In an embodiment, the enclosure defines the blood-flow lumen. In another embodiment, however, the structure includes a pump housing formed separately from the enclosure, the blood-flow lumen being at least partially defined by the pump housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings: 
         FIG. 1  is an exploded perspective view of a blood pump, according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of a top part of the blood pump of  FIG. 1 ; 
         FIGS. 3A-B  are cross-sectional views of the top part of  FIG. 2 ; 
         FIGS. 4A-B  are cross-sectional views of the blood pump of  FIG. 1 , fully assembled; 
         FIGS. 5A-C  are cross-sectional and exploded views of a prior art blood pump of the type described above; and 
         FIGS. 6A-C  are various exploded, perspective, and cross-sectional views of an existing HVAD® pump, while  FIG. 6D  is a chart detailing the components thereof. 
     
    
    
     DETAILED DESCRIPTION 
     In describing certain features of the present invention, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to any specific terms used herein. 
       FIG. 1  depicts a blood pump  18  according to an embodiment of the present invention. Blood pump  18  includes a pump housing  60 . Housing  60  is a generally tubular structure formed from a non-magnetic material as, for example, a ceramic. The housing  60  has an inner chamber  66  for carrying blood or other fluid through pump  18 , an inlet  62  for accepting the blood, and an outlet  64  for discharging the blood. A rotor  70  is positioned in pump housing  60  for pumping blood or other fluids through pump  18 . A stator  40  ( FIG. 4A ) incorporating a plurality of electrical coils (not shown) surrounds pump housing  60 . The coil arrangement itself may be conventional. For example, the stator may include three sets of coils. Each such set may include two coils disposed on opposite sides of the housing. The sets may be arrayed at equal spacings around the circumference of the housing. The coils are connected to an electrical cable  90 , commonly referred to as a driveline, incorporating electrical leads  90 A ( FIG. 4A ). 
     A monolithic enclosure  20  is, in one embodiment, formed from a biocompatible polymer that is over molded onto pump housing  60  and stator  40  to assist in creating a fully fluid-tight (in some cases hermetic) enclosure, which encompasses the exterior of pump housing  20 , the stator  40 , and the leads  90 A of driveline  90 . Blood pump  18  is therefore operable in a fluid-filled environment, such as the interior of a human or other mammalian body, to pump blood. 
     In one embodiment, upstream and downstream sections  24 ,  26  of pump housing  60  are in direct contact with enclosure to establish a seal at sections  24 ,  26  (e.g., a hermetic seal). For instance, enclosure  20  may be molded around pump housing  60 , as described in more detail below, so that enclosure directly contacts sections  24 ,  26  of pump housing  60  to establish an immediate seal with pump housing  60  at sections  24 ,  26 . Pump housing  60  also includes an inner chamber  66  for carrying blood or other fluid through pump  18 , an inlet  62  for accepting the blood, and an outlet  64  for discharging the blood. In addition, since enclosure  20  contacts pump housing  60  (e.g., at upstream and downstream sections  24 ,  26 ), it is stabilized in the upstream-to-downstream direction relative to enclosure  20 . 
     As shown in  FIGS. 3A-B  and  4 A-B, enclosure  20  defines an inlet  22 . An upper lip  38  may be formed on enclosure  20  for overlying an upstream edge of pump housing  60  (e.g., the edge of its inlet  62 ) so that a seamless transition is provided between inlet  22  of enclosure  20  and inlet  62  of pump housing  60 . Likewise, a lower lip  39  may be formed on enclosure  20  for overlying a downstream edge of pump housing  60  (e.g., the edge of its outlet  64 ) so that a seamless transition is provided between outlet  64  of pump housing  60  and a downstream portion of enclosure  20 . In one embodiment, inlet  62  of pump housing  60  is also reduced in diameter as compared to its outlet  64 , as shown. Although enclosure  20  may be formed with upper and lower lips  38 ,  39  providing seamless transitions, it is also contemplated that pump housing  60  may provide the sole inlet to pump  18  and enclosure  20  may, for example, be molded about a middle section of pump housing  60 . Thus, in this embodiment, the ends of pump housing  60  may protrude somewhat from the ends of enclosure  20 . 
     As shown in  FIGS. 3A-4B , an annular cavity  28  is formed between pump housing  60  and enclosure  20  for housing stator  40 . Cavity  28  circumferentially surrounds pump housing  60  and receives stator  40 . In one embodiment, enclosure  20  is molded around pump housing  60  (e.g., injection molded) while stator  40  is positioned on housing  60  so that molded enclosure  20  contacts stator  40  and precisely forms cavity  28  to conform to the shape of stator  40 . In this manner, stator  40  is secured relative to enclosure  20  and pump housing  60  by virtue of over molding. Stated another way, when enclosure  20  is molded around pump housing  60  and stator  40 , it forms a unitary part with pump housing  60  and stator  40  and secures such components relative to each other. The enclosure also encompasses leads  90 A of drive line  90 . The enclosure defines a driveline conduit  30  projecting away from the housing. The driveline  90  extends out of the enclosure through conduit  30 . Desirably, conduit  30  is formed in the same molding operation used to form the remainder of enclosure  20 . Thus, the material of the enclosure bonds to the exterior of the driveline and forms a seal. Thus, without additional seals or other components, stator  40  and its cavity  28  are effectively sealed from chamber  66  of pump housing  60  and the flow of blood therethrough. A long-lasting fully-sealed environment is therefore established in which pump  18  can operate without the worry of leaking or failure of the sealed environment. Fewer components are also used to establish the sealed environment. As mentioned above, in one embodiment the environment is hermetic. In addition, enclosure  20  may be molded over pump housing  60  and stator  40  so that enclosure  20  contacts other points besides upstream and downstream sections  24 ,  26 , and establishes a seal at those points. 
     In a particular embodiment, enclosure  20  is molded over stator  40  in such a way as to form a cavity  28  with surfaces  29  transverse to an upstream-to-downstream direction ( FIGS. 3A-B ). Surfaces  29  abut the ends of stator  40 , as shown in  FIGS. 4A-B , so that stator  40  is secured in the upstream-to-downstream direction. In other words, surfaces  29  are separated by a distance that is approximately equal to or only insignificantly greater than a distance between the ends of stator  40  so that stator  40  is secured in the upstream-to-downstream direction. Because of this, stator  40  does not need to be secured to pump housing  60 , as is the case in certain prior art pumps. For example, certain prior art pumps include a pump housing that is adhered to the stator (e.g., through adhesion/cure techniques) to further secure it in position. This is the case with pump  120  of  FIGS. 5A-C . With blood pump  18 , no such step is needed. Instead, stator  40  is secured in the upstream-to-downstream direction relative to pump housing  60  by way of molding enclosure  20  over stator  40  and housing  60 . Cavity  28  is likewise formed to facilitate securing stator  40  relative to pump housing  60  and to conform to the shape of stator  40 . Thus, stator  40  remains in position relative to pump housing  60  during operation so that rotor  70  can be appropriately positioned, and remain in position, in chamber  66  of pump housing  60 . 
     As shown in  FIGS. 1 and 4A -B, drive line wires  90  may be connected to stator  40  to control the operation thereof, either prior to or after the molding process for enclosure  20 . Wires  90  may be connected to terminals on stator  40 , for example three ( 3 ) terminals for three-phase operation of stator  40 , and wrapped around stator  40  exiting through cable conduit  30  of enclosure  20 . Wires  90  may also be wrapped about a section of pump housing  60  for strain relief purposes. Drive line  90  extends from stator  40  to a controller (not shown), which provides power for operating stator  40  and blood pump  18 . The controller may be outside of the patient&#39;s body, or may be an internal implantable controller. If an internal controller is used, it may be associated with a battery having inductive charging capabilities for charging the battery for pump  18 . 
     Referring now to  FIGS. 1-2 , enclosure  20  is also molded so as to have an upper volute portion  36  defining part of an outlet of pump  18 . In particular, as shown in  FIGS. 3A-B , upper volute portion  36  is unitary with the rest of enclosure  20 , it being a unitary molded part, and includes a disc-like chamber that is arranged to accept blood or other fluid from outlet  64  of pump housing  60 . Upper volute portion  36  also includes outlet portion  32 , which is roughly semi-tubular in shape. 
     One or more openings  34  is provided in enclosure  20  adjacent upper volute portion  36  so as to connect upper volute portion  36  with a lower volute portion  100 , as shown in  FIGS. 1 and 4A . In particular, one or more rivets, screws, or other fixation mechanisms  110  are inserted through opening(s)  34  to secure upper volute portion  36  to a lower volute portion  100  and form a complete volute having an outlet. Referring to  FIGS. 1 and 4A -B, lower volute portion  100  includes an annular chamber  106  defined by a center post  104  (in some cases domed), and an outlet portion  102  for interacting with outlet portion  32  of upper volute portion  36 . Once lower volute portion  100  is connected to upper volute portion  32  via fixation mechanism(s)  110 , as shown in  FIGS. 4A-B , a complete volute with an outlet for discharging blood is formed. Blood can therefore travel through pump  18 , in particular chamber  66  of pump housing  60 , and exit into the volute to be driven into circumferential flow by center post  104  and subsequently out of the outlet defined by outlet portions  32 ,  102 . In other words, counter pressure generated by rotor  70  may cause blood or other fluid to interact with center post  104  and move circumferentially within the volute and out of its outlet. 
     Rotor  70  may be any suitable rotor for fitting within chamber  66  of pump housing  60  and driving blood through pump  18 . In one embodiment, rotor  70  includes an impeller defining various blades  74  used to impel blood through pump  18 . The blades may have spaces or channels  76  between them for channeling blood through rotor  70 . In addition, one or more hydrodynamic surfaces  72  may be included on rotor  70  for creating a frictionless operation within pump  18 . Stated another way, hydrodynamic surfaces  72  may be included with rotor  70  so that a layer of blood forms a barrier between rotor  70  and pump housing  60  and rotor  70  can rotate within pump housing  60  against the layer of blood in a frictionless or near-frictionless environment. Hydrodynamic surfaces  72  may also act to cause rotation of rotor  70 . Hydrodynamic surfaces of the type disclosed herein are described in detail in U.S. Pat. No. 8,007,254, assigned to the Applicant, HeartWare, Inc., the disclosure of which is incorporated by reference herein. Any of the rotors of the &#39;254 patent may be utilized with blood pump  18 , if desired. Likewise, any of the disclosed stators of the &#39;254 patent could be utilized with blood pump  18  as well. 
     Rotor  70  may be composed of a magnetic alloy, such as platinum cobalt, and may include a plurality of permanent drive magnets for interacting with stator  40 . Again, such drive magnets are described in the &#39;254 patent. Rotor  70  is hydrodynamically and/or magnetically suspended in pump housing  60  by virtue of its interaction with stator  40 , and is operable to rotate within chamber  66  once stator  40  is activator to drive blood through pump  18 . As stator  40  is secured relative to pump housing  60  in the manner described above (e.g., through molding), rotor  70  is also stabilized within chamber  66  during operation. In other words, since stator  40  is secure in the upstream-to-downstream direction, the position of rotor  70  will not be affected by any unintended movement of stator  40 . 
     In use, blood pump  18  is implanted within a patient suffering from, for example, congestive heart failure to assist in pumping of blood from the heart. Blood pump  18  may be positioned to support either a left ventricle of the heart (LVAD) or a right ventricle (RVAD). In some cases, blood pump  18  is implanted into the pericardial space directly adjacent to the heart (e.g., with inlet  22  in either the right or left ventricle at the respective apex). The outlet defined by outlet portions  32 ,  102  is positioned outside of the heart and is attached to a tubular conduit (not shown), referred to as a graft. Where the inlet is positioned in a ventricle, the graft is in turn connected to the aorta to establish blood flow through pump  18  and to the aorta. In some cases, a sewing ring is utilized to mount pump  18  on the heart, and an apical coring tool is used to establish access to the heart. 
     The molding process for pump  18  uses an appropriate biocompatible material, for instance a thermoplastic such as polyether ether ketone (PEEK), a PEEK composite, or any other suitable implantable grade polymer, optionally having one or more of the following properties: rigid, good electrical insulation properties, chemical resistance, and able to withstand sterilization processes (e.g., ETO). While the use of an injection-molding system is described below, it is recognized that any suitable molding system may be used (e.g., transfer molding), and that the description of injection molding herein is only exemplary. In a particular embodiment, after selecting the appropriate material, an injection mold (not shown) shaped to produce the desired exterior shape of enclosure  20  is provided. Pump housing  60  with a stator  40  surrounding it is then inserted into the mold. The mold may have a highly-polished surface finish so as to achieve a smooth exterior surface for pump  18  via the molding process. Proper equipment is used to stabilize pump housing  60  and stator  40  within mold so that such components are not mistakenly moved during the injection molding process. In one embodiment, drive line  90  is also connected to stator  40  while in the mold, and leads  90 A extend out of the mold by some distance so that the entirety of line  90  is not over molded (e.g., to allow for later connection to other components). An alternate embodiment allows for drive line  90  to be connected after the molding process. 
     A shot of the biocompatible material is then heated and forced under pressure into the mold where it surrounds pump housing  60 , stator  40 , and drive line  90  to form enclosure  20 . A unitary part is therefore established comprising pump housing  60 , stator  40 , and enclosure  20 . As described previously, during the molding process enclosure  20  directly contacts and bonds to upstream and downstream sections  24 ,  26  of pump housing  60 , effectively establishing a seal (e.g., hermetic) at those sections  24 ,  26  to seal off stator  40  (and its cavity  28 ) from the rest of pump  18 . The unitary part comprising pump housing  60 , stator  40 , and enclosure  20  can then be attached with the other components of pump  18  (e.g., lower volute  100 , rotor  70 , a controller, etc.) for implantation and use within the patient. 
     Although the foregoing embodiments are described as utilizing certain structures, others may also be employed and are equally contemplated within the scope of the invention. For example, although a separately-formed pump housing  60  is utilized with blood pump  18 , it is not a necessary component and may be omitted, in one embodiment. In this case, stator  40  may be positioned in a mold and a biocompatible material of the type discussed above (or another material) may be molded over stator so as to establish an enclosure  20  that has a continuous lumen through it from an inlet side  22  to an outlet. Thus, instead of supplying pump housing  60  and enclosure  20  to establish a blood-flow lumen, it is contemplated that enclosure itself may be molded over stator  40  in such a way to establish a blood-flow lumen without pump housing  60 . Stated another way, in this embodiment the material of the enclosure also forms the pump housing, and the pump housing is part of the same monolithic element as the enclosure. In certain embodiments, the flow lumen of such an enclosure  20  may also be surface treated or hardened to provide for improved characteristics in the flow-lumen area. Thus, in this embodiment, stator  40  is sealed from the blood-flow lumen (e.g., hermetically), but enclosure  20  itself defines the lumen via the molding process. 
     As another option, while rotor  70  is disclosed as being composed of platinum cobalt, it may alternatively be injection molded (or ceramic injection molded—CIM) out of a biocompatible material. In this instance, a series of permanent magnets may be molded into rotor  70  (e.g., on surfaces of the impeller blades) so that rotor  70  can interact properly with stator  40  and rotate to drive blood through blood pump  18 . In another example, the molded rotor may have a slot(s) in the blades to allow the insertion of a permanent magnet(s) after molding. 
     In a variant of the process discussed above, the enclosure may be formed from a thermosetting polymeric material such as an epoxy, which cures by chemical reaction in the mold. 
     In yet another variant, lower volute  100  may be composed of a metal material (e.g., titanium), any of the biocompatible polymer materials discussed above, or a combination thereof. Indeed, lower volute  100  (or a portion thereof, for instance its center post  104 ) is composed of titanium or another suitable metal in one embodiment to improve the durability of lower volute  100  (and/or the portion made of metal). In particular, center post  104  may be composed of titanium or another suitable metal to increase its durability while the reminder of lower volute  100  may be composed of any of the biocompatible polymer materials noted above. In such an embodiment, center post  104  may be insert molded with the remainder of polymer lower volute  100 . Alternatively, the entirety of lower volute  100  may be metal. 
     Further, while the above-described molding process is disclosed as being usable with an axial flow pump, it is equally usable with a radial flow pump having, for example, a centrifugal pump. Such a pump is offered by the Applicant, HeartWare, Inc., as its HVAD® pump. An existing HVAD® pump of the type described is shown in detail in  FIGS. 6A-C , with the components thereof designated in the chart shown in  FIG. 6D . In one embodiment, it is contemplated that parts  10 ,  12 ,  4 ,  7 ,  8 , and  9  may be molded as a first unitary piece using any of the aforementioned molding processes, and that parts  2 ,  1 ,  4 ,  3 ,  5 , and  6  may be molded as a second unitary/composite piece. Further, the first and second unitary pieces may then be joined together to form the HVAD® device. In addition, although not shown, a centrifugal impeller of the type used in the HVAD® pump may be fitted around center post  11  to pump blood within the cavity created by the first and second unitary pieces ( FIG. 6C ). The centrifugal impeller is operated by front and rear motors  12 ,  3 . In these embodiments, the molding of the first and second unitary pieces can sealingly enclose front and rear motors  12 ,  3  (e.g., without additional parts and/or seals) so that such are isolated from the flow of blood through the HVAD® pump. Other molded combinations beyond that discussed above are also contemplated, of course. 
     In yet another variant, a sensor may be embedded into a portion of enclosure  20  of pump  18  during the molding process. For instance, a sensor capable of taking diagnostic measurements concerning the operation of pump  18  and/or the patient may be embedded into enclosure  20 . In one embodiment, an accelerometer may be embedded in enclosure  20  for determining the positioning of pump  18 . The sensor may be connected to an electrical lead, fiber optic cable, or other suitable connection for conveying the information gleaned via the sensor to the pump  18 &#39;s controller, or to an external system. The sensor alternatively could have wireless capabilities for transmitting such information. Thus, the sensor could allow for ascertaining significant information concerning pump  18 &#39;s operation, its position, or the condition of the patient. 
     While the pump of this invention is also described in terms of a blood pump, it is contemplated that the pump might be used for pumping other fluids as well. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 
     It will also be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims, and that the features described in connection with individual embodiments may be shared with others of the described embodiments. In particular, as understood by one of skill in the art, the features of any dependent claim may be shared with a separate independent or dependent claim, to the extent feasible.