Abstract:
An implantable drug infusion device includes a pump tube for holding a liquid to be pumped. A race is configured to support the tube. A roller assembly is configured to compress the tube against the race at one or more points along the path, and the roller assembly includes at least one roller. A tube guide is operably connected to the roller assembly to align the pump tube with respect to a corresponding roller.

Description:
RELATED APPLICATIONS 
     The following applications are related to the present application: “Implantable Drug Delivery Device with Peristaltic Pump Having a Bobbin Roller Arm”, assigned Ser. No. 09/835,208, and “Implantable Drug Delivery Device with Peristaltic Pump Having Retractable Rollers, assigned Ser. No. 09/834,874, both of which are being filed herewith. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an implantable drug delivery device for infusing a therapeutic agent into an organism, and more particularly, relates to an improved peristaltic implantable pump using tube guides for improved alignment of a fluid tube. 
     2. Description of the Related Art 
     Implantable drug infusion devices are well known in the art. These devices typically include a medication reservoir within a generally cylindrical housing. Some form of fluid flow control is also provided to control or regulate the flow of fluid medication from the reservoir to the outlet of the device for delivery of the medication to the desired location in a body, usually through a catheter. These devices are used to provide patients with a prolonged dosage or infusion of a drug or other therapeutic agent. 
     Active drug infusion devices feature a pump or a metering system to deliver the drug into the patient&#39;s system. An example of such a drug infusion pump currently available is the Medtronic SynchroMed programmable pump. Additionally, U.S. Pat. Nos. 4,692,147 (Duggan), 5,840,069 (Robinson), and 6,036,459 (Robinson), assigned to Medtronic, Inc., Minneapolis, Minn., disclose body-implantable electronic drug administration devices comprising a peristaltic (roller) pump for metering a measured amount of drug in response to an electronic pulse generated by control circuitry associated within the device. Each of these patents is incorporated herein by reference in their entirety for all purposes. Such pumps typically include a drug reservoir, a fill port, a peristaltic pump having a motor and a pumphead to pump out the drug from the reservoir, and a catheter port to transport the drug from the reservoir via the pump to a patient&#39;s anatomy. The drug reservoir, fill port, peristaltic pump, and catheter port are generally held in a housing, or bulkhead. The bulkhead typically has a series of passages extending from the drug reservoir and through the peristaltic pump that lead to the catheter port, which is typically located on the side of the housing. The peristaltic pumps use rollers which move along a pump tube, thereby moving liquid through the tube. 
     The prior art delivery devices, however, are limiting in that the tube may not be properly aligned with respect to the rollers, leading to inefficient occlusion of the tube. Prior art solutions to the alignment problem include placing wings along the tube, which may lead to an increased height of the device, compromise the tubing geometry, and increase the cost and complexity of manufacture of the tube. 
     It is an object of the present invention to provide an implantable drug infusion device which reduces or wholly overcomes some or all of the difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of preferred embodiments. 
     SUMMARY OF THE INVENTION 
     The present invention provides an implantable drug infusion device which features a peristaltic pump having a new configuration, in which a roller assembly of the peristaltic pump includes a tube guide to properly align a pump tube with respect to rollers of the roller assembly. 
     In accordance with a first aspect, an implantable drug infusion device includes an implantable drug infusion device including a pump tube for holding a liquid to be pumped. A race is configured to support the tube along a path. A roller assembly is configured to compress the tube against the race at one or more points along the path, and the roller assembly includes at least one roller. At least one tube guide is operably connected to the roller assembly to align the pump tube with respect to a corresponding roller. 
     In accordance with another aspect, an implantable drug infusion device includes a bulkhead having a race. A pump tube having an inlet and an outlet is positioned within the race. A roller assembly is configured to compress the tube against the race at at least one point along the path, and the roller assembly includes at least one roller. A drive assembly drives the roller assembly relative to the tube along the path so as to move a liquid through the tube. At least one tube guide is operably connected to the roller assembly to align the pump tube with respect to a corresponding roller. 
     From the foregoing disclosure, it will be readily apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this area of technology, that the present invention provides a significant advance over the prior art. Preferred embodiments of the implantable infusion device of the present invention can significantly improve the alignment of a pump tube with rollers of the device. This will allow for increased manufacturing flexibility, decreased cost of tube manufacture, reduced height of the device, and improved performance. These and additional features and advantages of the invention disclosed here will be further understood from the following detailed disclosure of preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Preferred embodiments are described in detail below with reference to the appended drawings. The accompanying drawings, which are incorporated into and form a part of this specification, together with the description, serve to explain the principles of the invention. The drawings are not drawn necessarily to scale, are only for the purpose of illustrating a preferred embodiment of the invention, and are not to be construed as limiting the invention. Some features of the implantable drug infusion device depicted in the drawings have been enlarged or distorted relative to others to facilitate explanation and understanding. The above mentioned and other advantages and features of the invention will become apparent upon reading the following detailed description and referring to the accompanying drawings in which like numbers refer to like parts throughout and in which: 
     FIG. 1 is an exploded perspective view of an implantable drug infusion device in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of a pumphead assembly of the implantable device of FIG. 1; 
     FIG. 3 is a section view, taken along lines  3 — 3  of FIG. 2, of a trailing arm of the implantable device of FIG. 1; and 
     FIG. 4 is perspective view, partially cut away, of the implantable device of FIG. 1, shown in its assembled state; 
     FIG. 5 is a section view, taken along lines  4 — 4  of FIG. 3, of the implantable device of FIG. 1; 
     FIG. 6 is an exploded perspective view of the roller assembly of FIG. 1; 
     FIG. 7 is a section view, taken along lines  7 — 7  of FIG. 2, of a trailing arm of the implantable device of FIG. 1; 
     FIG. 8 is an elevation view of a trailing arm of the implantable device of FIG. 1; and 
     FIG. 9 is a plan view of the roller assembly and pump tube shown in place within the race of the implantable device of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, an implantable drug infusion device  2  in accordance with the invention comprises a bulkhead  4  containing a number of chambers and cavities sized and configured to house various subsystems of the implantable drug infusion device. In particular, bulkhead  4  has a first chamber  6  sized and configured to house a peristaltic pumphead assembly  8 . A second chamber  10 , sized and configured to house a motor assembly  12  which drives pumphead assembly  8 , is positioned adjacent first chamber  6  and separated therefrom by a wall  13 . Other chambers of bulkhead  4  house a battery and the electronic circuitry (not shown) used to operate implantable drug infusion device  2  and to control the dosage rate of the medication into the body. 
     Pumphead assembly  8  includes a compression member, such as roller arm assembly  20 , for compressing a pump tube  14  having an inlet  16  and an outlet  18 . First chamber  6  has a generally circular wall  24  defining a pump race  19 . Pump tube  14  is placed in first chamber  6  in close proximity to wall  24  so that roller arm assembly  20  may force the tube against the wall, thereby forcing medication to move through the tube in a known peristaltic manner. Flanges  21  extending outwardly from pumphead assembly  8  are received in recesses  23  formed in first chamber  6 , supporting pumphead assembly  8  in first chamber  6 . Inlet  16  is placed in a pump inlet cavity  26  formed in bulkhead  4 . Pump inlet cavity  26  is connected to the pump race  19  by a pump inlet race ramp  28 . Pump tube outlet  18  is placed in a pump outlet cavity  30  formed in bulkhead  4 . Pump tube outlet cavity  30  is connected to the pump race  19  by a pump outlet race ramp  32 . In a preferred embodiment, both pump inlet race ramp  28  and pump outlet race ramp  32  have an arcuate geometry. A cover (not shown) is also provided for bulkhead  4  to provide protection for the components of drug infusion device  2 . Motor assembly  12  includes a motor (not shown) which drives a four-stage gear assembly  13 , only the fourth stage of which is visible. Teeth  15  are formed on the periphery of the fourth stage of gear assembly  13 . 
     Bulkhead  4  has an integral fill port cavity  34 , sized and configured to house a septum and components to retain the septum. Drugs are injected through the septum to fill a reservoir (not shown) contained within a lower portion of bulkhead  4 . A pathway is formed between the reservoir and pump inlet cavity  28 , through which drugs are introduced into pump tube  14 . The drugs exit pump outlet cavity  30  and travel through another pathway formed in bulkhead  4  to a catheter port on the periphery of bulkhead  4  from which the drug exits the device  2  and enters the anatomy of the individual. The structure of the septum, retaining components, pathways, and catheter port are known to one of skill in the art and are not shown here. 
     Referring now to FIG. 2, pumphead assembly  8  is shown in exploded form. Pumphead assembly  8  includes a drive gear  40  with teeth  44  formed about its periphery. A support plate  42  is positioned below drive gear  40 . Flanges  21  extend outwardly from support plate  42  and, as described above, are received in recesses  23  of bulkhead  4 , and preferably welded thereto. Roller arm assembly  20  is positioned below support plate  42 . Drive shaft  46  extends axially through apertures in roller arm assembly  20 , support plate  42 , and drive gear  40 , and is retained by retaining screw  48 . Drive shaft  46  is supported for rotation at its lower end by lower bearing  50 , and at a central location, between roller arm assembly  20  and support plate  42 , by upper bearing  52 . 
     Roller arm assembly  20  comprises a central hub  53  having an aperture  55  through which drive shaft  46  extends. Flats  57  on drive shaft  46  mate with flats  59  of aperture  55  such that roller arm assembly  20  rotates as drive shaft  46  rotates. A plurality of trailing arms  54  are each pivotally secured by a pin  56  to hub  53 . Trailing arm  54  comprises upper plate  51  and lower plate  61 . A roller  58  is pivotally secured to each trailing arm  54  by an axle  60 . As seen in FIG. 3, axle  60  extends between upper and lower plates  51 ,  61 . Axle  60  passes through an inner race  63  of roller  58 . Inner race  63  is extended vertically to provide clearance between an outer race  65  of roller  58  and upper and lower plates  51 ,  61 . In the illustrated embodiment, roller arm assembly  20  is shown with three trailing arms  54  and three corresponding rollers  58 , however, the number of trailing arms  54  and rollers  58  may be greater or lesser than three. 
     As seen in FIGS. 4 and 5, teeth  15  of gear assembly  13  drivingly engage teeth  44  of drive gear  40 , thereby causing rollers  58  to move about race  19 , compressing and occluding tube  14  as they move and forcing the drug therethrough in known peristaltic fashion. As noted above, inlet race ramp  28  and outlet race ramp  32  each have an arcuate geometry, which reduces the torque required as each roller  58  engages pump tube  14  during rotation of roller arm assembly  20 . 
     Referring back to FIG. 2, each trailing arm  54  and its corresponding roller  58  is adjustably biased outwardly by a biasing member, such as spring  62 . In a preferred embodiment, spring  62  is a coil spring. As seen in FIG. 5, spring  62  is oriented to facilitate the occlusion, or compression, of tube  14  by roller  58 . Since manufacturing tolerances on the system components, i.e., roller  58 , tube  14  and race  19 , can result in variations in the gap A between roller  58  and race  19 , the biasing action of spring  62  can advantageously minimize the variation in load placed by roller  58  on tube  14 , greatly increasing the compliance of the system. Thus, for an incremental change in the gap between roller  58  and race  19 , the incremental load required is reduced. For example, in prior art devices, where the system compliance is accounted for by the tube itself, a 0.001″ decrease in a radial direction of the race could incur a 150 g load increase on roller  58 . With the present invention, however, spring  62  may be sized with a spring rate such that for a 0.001″ decrease in the race, a 1.5 g increase in load is realized. In a preferred embodiment, spring  62  is formed of a highly corrosion resistant and fatigue resistant alloy. Suitable materials include cobalt alloys and stainless steel. In other preferred embodiments, a nitinol shape memory alloy may be used for spring  62 . 
     Roller arm assembly is shown in exploded form in FIG.  6 . As noted above, roller arm assembly  20  comprises three trailing arms  54  pivotally secured by a pin  56  to hub  53 . Hub  53  comprises upper plate  86 , lower plate  88 , and center plate  90 . Rods or rivets  92  extend through apertures  94 ,  95 , and  96  formed in upper plate  86 , center plate  90 , and lower plate  88 , respectively. Pivot pins  56  extend between upper plate  51  and lower plate  61  of each trailing arm  54 . Hooks  100 ,  102  formed on upper plate  86  and lower plate  88 , respectively, of hub  53 , capture pivot pins  56  of trailing arms  54 . A first end  104  of each spring  62  seats on mounting plate  106  of trailing arm  54 . A second end  108  of each spring  62  seats about a rib  110  formed on center plate  90  of hub  53 , as can be seen more clearly in FIG.  7 . The force of spring  62  exerted outwardly from hub  53  keeps pin  56  seated within hooks  100  and  102 , thereby maintaining trailing arms  54  in position on hub  53 . By using hooks  100  and  102  to capture pins  56  of trailing arms  54  rather than apertures, the manufacturing costs of hub  53  can be reduced, and very close tolerances can be achieved, improving manufacturing flexibility. 
     As seen in FIGS. 6 and 8, a tube guide  66  is connected to trailing arm  54  and is formed of an upper blade  68  and a lower blade  70 . In another preferred embodiment, tube guide  66  may be connected directly to hub  53 . A rear portion  69  of upper blade  68  is inclined downwardly, with respect to a longitudinal axis L of pump tube  14  (shown here in dashed lines), toward a trailing edge  73  of upper blade  68 . A rear portion  71  of lower blade  70  is inclined upwardly, with respect to a longitudinal axis L of pump tube  14 , toward a trailing edge  75  of upper blade  68 . Tube guide  66  serves to help keep pump tube  14  properly aligned and centered vertically with respect to rollers  58 . By using tube guide  66  to align the pump tube any tendency for the pump tube to migrate up or down with respect to the rollers is minimized. 
     As seen in FIG. 9, pump tube  14  is positioned between roller assembly  20  and race  19 . As roller assembly  20  rotates in the direction of arrow C, rollers  58  compress pump tube  14  against race  19 , forcing drug through the pump tube  14 . Pump tube  14  is aligned with respect to each roller  58  by a tube guide  66  which is immediately in front of the roller  58  and a tube guide  66  which immediately follows the roller  58 . Thus, pump tube  14  is aligned both prior to and after encountering each roller  58 , ensuring proper alignment of the pump tube. As each roller  58  passes a section of pump tube  14 , the pump tube is occluded by being squeezed by roller  58  against race  19 , thereby increasing the vertical height of the pump tube at this point, seen in FIG.  8 . Pump tube  14  springs back to its normal cross-section after roller  58  passes, allowing the more closely spaced portions  69 ,  71  of upper and lower blades  68 ,  70  to guide pump tube  14 . This alignment of pump tube  14  with respect to rollers  58  is advantageously accomplished without the need to modify the geometry of the pump tube, providing for reduced manufacturing costs for the pump tube. 
     In light of the foregoing disclosure of the invention and description of the preferred embodiments, those skilled in this area of technology will readily understand that various modifications and adaptations can be made without departing from the scope and spirit, of the invention. All such modifications and adaptations are intended to be covered by the following claims.