Abstract:
An implantable pump having a bulkhead, a reservoir structure attached to the bulkhead and upper and lower cases attached to the bulkhead by a single outer seal as well as a method of making such a pump is disclosed. The reservoir structure forms a reservoir that contains fluid drug or other medicaments. The upper and lower cases are attached to the bulkhead by first connecting either the upper or lower case directly to the bulkhead. Then, the lower or upper case not attached to the bulkhead is attached to the upper or lower case that had been previously attached to the bulkhead.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of provisional application, U.S. Ser. No. 60/229,067, filed Aug. 30, 2000, entitled “SYSTEM AND METHOD FOR ATTACHING UPPER AND LOWER OUTER CASES IN AN IMPLANTABLE DRUG PUMP”, by Maurice T. Y. Verbeek and Frans Philippens. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to implantable medication delivery devices that are implanted within the body of a patient to deliver drugs or other fluid medicaments and methods of construction of the devices. More particularly, the invention relates to techniques for sealingly attaching upper and lower outer cases to a bulkhead in such medication delivery devices. 
     2. Description of the Related Art 
     When chronic administration of a pharmaceutically active agent is required, an implantable infusion pump (“IIP”)  10 , having a reservoir  12  connected to a catheter  14 , may be the desired delivery means (FIG.  1 ). For example, a IIP-catheter delivery system may be preferred when it is important to deliver the agent to a specific site or when the agent must be administered to spaced sites in tightly controlled, yet minute dosages. 
     Catheter  14  is connected to IIP  10  and carries fluid medicament from the reservoir  12  in IIP  10  to a desired location in a body. The IIP  10  and catheter  14  are implanted within the body. 
     A number of approaches have been followed in the prior art for the dispensing of medical substances in the body. One particularly effective method has been to implant a reservoir of fluid medical substances and a pump in a patient&#39;s body. The reservoir and pump are connected to a catheter that delivers the fluid medical substance to a desired location in the body. 
     A number of reservoirs, pumps and combinations of reservoirs and pumps have been developed. For example, U.S. Pat. No. 3,527,220 shows an implantable drug administrator that operates with a refillable bladder reservoir and a roller pump that is driven by a magnet located outside the body. U.S. Pat. No. 3,951,147 shows a reservoir formed from a bellows enclosed within a housing. The contents of the reservoir are pressurized by a fluorocarbon fluid located in the space between the housing and bellows. The unit continuously dispenses the liquid to the body site through a capillary tube. U.S. Pat. No. 4,146,029 shows a dispenser that dispenses drugs in a predetermined manner which may be modified somewhat by means external to the body. A piston and bellows pumping device is used to dispense the drug. 
     Additional pumps and reservoirs are shown in U.S. Pat. No. 4,931,050, issued Jun. 5, 1990 to Samir F. Idriss entitled “Constant Pressure Variable Flow Pump”; U.S. Pat. No. 4,838,887, issued Jun. 5, 1990 to Samir F. Idriss entitled “Programmable Valve Pump”; U.S. Pat. No. 4,714,462, issued Jun. 5, 1990 to Robert A. DiDomenico entitled “Positive Pressure Programmable Infusion Pump”; U.S. Pat. No. 4,714,462, issued Jun. 5, 1990 to Samir F. Idriss entitled “Passive Shuttle Metering Device For Implantable Drug Delivery System”; and U.S. Pat. No. 5,176,641 issued Jan. 5, 1993 to Samir F. Idriss entitled “Implantable Drug Infusion Reservoir Having Fluid Impelling Resilient Foam Member”. 
     Further pumps and reservoirs are shown in U.S. Pat. No. 5,575,770 issued Nov. 19, 1996 to Gerald S. Melsky and Bradley J. Enegren entitled “Implantable Drug Infusion System With Safe Bolus Capability”; U.S. Pat. No. 4,978,338 issued Dec. 18, 1990 to Gerald S. Melsky and Frank R. Prosl entitled “Implantable Infusion Apparatus”; U.S. Pat. No. 5,908,414 issued Jun. 1, 1999 to Karl-Heinz Otto, Manfred Wieland, Hans Baumann and Jorg-Roger Peters entitled “Implantable Infusion Pump”; and U.S. Pat. No. 5,769,823 issued Jun. 23, 1998 to Karl-Heinz Otto entitled “Implantable Infusion Pump”. The collective teachings of the patents listed above are incorporated herein in their entireties by reference. 
     A typical IIP  10  for storing and delivering fluid medicaments to a desired location in a body according to the present invention is shown in cross-section in FIGS. 2 and 3. As mentioned above, IIP  10  stores and dispenses medical substances from a reservoir  12 . Reservoir  12  is formed by a reservoir structure  16  having a reservoir structure upper end  18  and a reservoir structure terminal end  20 . Reservoir structure  16  is typically a bellows  22  having pleated sides  24  and a substantially planar bottom  26  sealingly connected to the sides  24 . Pleated sides  24  are made up of a series of inwardly directed annular rings  28  and outwardly directed annular rings  30  sealingly connected at inner connection points  32  and outer connection points  34 . In the typical IIP  10 , bellows  22  terminates at its upper end  18  with an ultimate inwardly direct annular ring  36 . Ultimate inwardly direct annular ring  36  terminates in a bellows terminal end  38  so that the bellows terminal end  38  is the reservoir structure terminal end  20  for a bellows type reservoir structure  16 . Bottom  26  is usually circular so that bellows  22  is cylindrical. Because bellows  22  is cylindrical, bellows terminal end  38  is annular. 
     Bellows terminal end  38  is connected to an annular bracket  40 . Viewed in cross-section, bracket  40  has a horizontal leg  42 . Horizontal leg  42  has an inner terminal end  43  and an outer terminal end  44 . Bellows terminal end  38  is connected to bracket  40  at  45  near the inner terminal end  43  by means well understood in the art such as welding. Annular bracket  40  also includes a vertical leg  46 . Vertical leg  46  has an upper terminal end  47  and a lower terminal end  48 . 
     IIP  10  also includes a bulkhead  50  having a top surface  52 , a bottom surface  54  and an outer periphery  56 . IIP  10  includes a metering system  58  usually attached to the top surface  52  of bulkhead  50 . Metering system  58  may take the form of a peristaltic pump, a piston pump, a tubular or micro-machined capillary flow restrictor, a piezoelectric micropump or other metering means as will clear to those skilled in the art. Metering system  58  is connected to reservoir  12  through an output conduit  60 . 
     The bottom surface  54  of bulkhead  50  includes an annular recess  62  extending into bulkhead  50  toward top surface  52 . Recess  62  has an inner vertical wall  64  and a horizontal wall  65  connected together at  66 . Recess  62  also has an outer vertical wall  67  connected to the horizontal wall  65  at  68 . Horizontal leg  42  is about the same length as horizontal wall  66  while vertical leg  46  is about the same length as outer vertical wall  67 . Bellows  22  is attached to bulkhead  50  at recess  62  by bracket  40  as described below. 
     IIP  10  also typically has a primary self-sealing septum  70  through which a drug, fluid or other medicament is placed in the reservoir  12 . A hypodermic needle can be inserted through the skin and through the primary seal-sealing septum  70  into a chamber  72  that is connected to reservoir  12  through an inlet conduit  74 . Through the hypodermic needle, a quantity of a liquid agent, such as a medication, a growth factor, an antisense agent, an ionic solution, one or more antibodies, a hormone, proteins or peptides, viruses, cell suspension, a chemotherapeutic agent or toxin or some drug is inserted into the reservoir  12 . The liquid agent is then delivered from reservoir  12  through the metering system  58  and through catheter  14  that is attached to IIP  10  through a catheter connector  76  that is attached to the metering system  58 . The catheter  14  is positioned to deliver the agent to infusion sites in the patient&#39;s body. 
     IIP  10  may also have a catheter access port septum  78  through which a bolus injection of drug, fluid or other medicament may be administered directly to the patient through the catheter  14 , bypassing the metering system  58 . Catheter access port septum  78  may also be used to take a sample of cerebrospinal fluid (CSF) from catheter  14  or for checking the patency of catheter  14  in the event of a loss of therapeutic benefit. 
     As shown in detail in FIG. 4, IIP  10  also includes an upper case  80  and a lower case  82  that substantially defines the outer dimensions of IIP  10  and protects the inner parts, bellows  22 , bulkhead  50  and metering system  58 , of IIP  10 . Upper case  80  has a substantially flat upper surface  84  and a substantially cylindrical side wall  86 . Side wall  86  terminates in a terminal end  88 . Because side wall  86  is typically cylindrical, terminal end  88  is circular. 
     Lower case  82  has a substantially flat bottom surface  90  and a substantially cylindrical side wall  92 . Side wall  92  terminates in a terminal end  94 . Because side wall  92  is typically cylindrical, terminal end  94  is circular. 
     Upper and lower cases  80 ,  82  are typically attached to the bulkhead  50  at the outer periphery  56  of the bulkhead  50 . This is accomplished by attaching upper and lower cases  80 ,  82  to a protrusion  96  that extends away from the outer periphery  56 . Protrusion  96  has an upper surface  98  and a lower surface  100 . The width of upper surface  98  is the same as the thickness of the material of side wall  86 . Likewise, the width of lower surface  100  is the same as the thickness of the material of side wall  92 . 
     Upper case  80  is brought into contact with protrusion  96  so that terminal end  88  is brought into contact with the upper surface  98  of protrusion  96 . Terminal end  88  is then connected to protrusion  96  by means such as welding at  102  so that a sealed seam is created at  102  between upper case  80  and protrusion  96 . 
     Likewise, lower case  82  is brought into contact with protrusion  96  so that terminal end  94  is brought into contact with the lower surface  100  of protrusion  96 . Terminal end  94  is then connected to protrusion  96  by means such as welding at  104  so that a sealed seam is created at  104  between lower case  82  and protrusion  96 . 
     A propellant chamber  106  is placed between lower case  82  and the reservoir structure  16 . A propellant gas is place in propellant chamber  106 . The propellant gas acts as a pressure-providing means to the reservoir structure  16  that compresses the reservoir structure  16  to discharge the drug or other agent stored in the reservoir  12 . The propellant gas used to drive such a “gas driven” IIP  10  is a fluid that is in phase change between a liquid state and a gas state when, i.e., in equilibrium between phases at around 35-37 degrees (Celsius), which is the usual temperature range of the human body. 
     In a particular type of IIP  10 , metering system  58  takes the form of a tubular or micro-machined capillary flow restrictor. In such a pump, the medical substance is dispensed from the reservoir  12  at a constant rate that depends primarily on the geometry of the tubular or micro-machined flow restrictor. In such a IIP  10 , it is relatively important that the pressure in propellant chamber  106  be maintained at a higher pressure than is necessary in a IIP  10  having a metering system  58  comprising a peristaltic pump, a piston pump or a piezoelectric micropump. For example, the propellant pressure in a peristaltic pump such as the Synchromed® pump manufactured and sold by Medtronic, Inc. of Minneapolis, Minn. is about 0.276 bar (4.00 Psi). On the other hand, the propellant pressure in a constant rate pump having a tubular flow restrictor such as the IsoMed® pump also manufactured and sold by Medtronic, Inc. of Minneapolis, Minn. is about 2.10 bar (30.46 Psi). The reason for a higher pressure in the propellant chamber  106  in a constant rate IIP  10  with a capillary tube flow restrictor is that this higher pressure reduces the variability in flow rates of the drug or other agent due to atmospheric conditions such as barometric pressure. 
     In manufacturing IIP  10 , the bellows terminal end  38  of bellows  22  is attached to the horizontal leg  42  of bracket  40  near the inner terminal end  43  by means such as welding. Since both bellows terminal end  38  and bracket  40  are annular, bellows terminal end  38  is connected to bracket  40  around an annular path as connection point  45  is moved around horizontal leg  42 . At this stage of the manufacturing process, access to connection point  45  is relatively free since bellows  22  has not yet been joined to bulkhead  50 . 
     Once bellows terminal end  38  has been joined to horizontal leg  42  of bracket  40 , bracket  40  is moved onto horizontal wall  66  of recess  62 . As described above, horizontal leg  42  is about the same length as horizontal wall  66 . This allows bracket  40  to be moved into recess  62  so that the inner terminal end  43  of horizontal leg  42  comes into contact with horizontal wall  66 . In this position, vertical leg  46  also comes into contact with outer vertical wall  67 . Bracket  40  is then connected to the recess  62  at lower terminal end  48  by means such as welding around the entire annular lower terminal end  48 . In this way, bellows  22  is sealingly attached to bulkhead  50  at lower terminal end  48  of bracket  40 . 
     The prior art system of connecting upper and lower cases  80 ,  82  to bulkhead  50  at protrusion  96  requires two outer seals  102 ,  104 , respectively. Because there are two seals  102 ,  104 , there is twice the likelihood that a defect will be formed in or develop in a seal than would be present in a single seal. It is therefore desirable to attach upper and lower cases  80 ,  82  to bulkhead  50  with a single outer seal. 
     SUMMARY OF THE INVENTION 
     An implantable pump having a bulkhead, a reservoir structure attached to the bulkhead and upper and lower cases attached to the bulkhead by a single outer seal as well as a method of making such a pump is disclosed. The reservoir structure forms a reservoir that contains fluid drug or other medicaments. The upper and lower cases are attached to the bulkhead by first connecting either the upper or lower case directly to the bulkhead. Then, the lower or upper case not attached to the bulkhead is attached to the upper or lower case that had been previously attached to the bulkhead. 
     It is an object of the invention to create an implantable pump having upper and lower outer cases sealingly attached to form an outer seal. 
     It is a further object of the invention to make such a pump that is relatively easy to manufacture. 
     These and other objects of the invention will be clear from the description of the invention contained herein and more particularly from the description in conjunction with the drawings attached hereto. Throughout this description, wherever referred to, like elements are referred to by like reference numbers and have all the described features and characteristics of the element unless specifically stated otherwise. Further, features of certain embodiments may be applicable to combining with other embodiments as will be clear to those skilled in the art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of the present invention will become more apparent by referring to the following detailed description and accompanying drawings, in which: 
     FIG. 1 is a perspective view of a pump and catheter system. 
     FIG. 2 is a side cross-sectional view of the typical pump of FIG.  1 . 
     FIG. 3 is a close-up side cross-sectional view of the typical pump of FIG.  1 . 
     FIG. 4 is a close-up side cross-sectional view of the connection of the upper and lower cases to the bulkhead in the typical pump of FIG.  1 . 
     FIG. 5 is a side cross-section view of the placement of the lower case with respect to the bulkhead in one embodiment of the present invention. 
     FIG. 6 is a side cross-section view of the connection of the lower case to the bulkhead in the embodiment of FIG.  5 . 
     FIG. 7 is a side cross-section view of the placement of the upper case on the lower case in the embodiment of FIG.  5 . 
     FIG. 8 is a side cross-section view of the connection of the upper case to the lower case in the embodiment of FIG.  5 . 
     FIG. 9 is a side cross-section view of an alternate embodiment of the present invention. 
     FIG. 10 is a side cross-section view of the placement of the upper case with respect to the bulkhead in one embodiment of the present invention. 
     FIG. 11 is a side cross-section view of the connection of the upper case to the bulkhead in the embodiment of FIG.  10 . 
     FIG. 12 is a side cross-section view of the placement of the lower case on the upper case in the embodiment of FIG.  10 . 
     FIG. 13 is a side cross-section view of the connection of the lower case to the upper case in the embodiment of FIG.  10 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An IIP  10  according to the present invention is shown in FIGS. 5-13. IIP  10  in the present invention includes a reservoir structure  16 , preferably in the form of a bellows  22  and metering system  60  as described above. IIP  10  also includes a bulkhead  50 . 
     FIGS. 5-8 shows a particular embodiment of the invention. In this embodiment, the outer periphery  56  does not have a protrusion  96 . Instead, outer periphery  56  has an annular recess  108  that extends around the outer periphery  56  at the lower edge  110  of outer periphery  56 . Recess  108  has a recess top  112  that is closer to the top surface  52  of bulkhead  50  than is the lower edge  110 . A recess vertical wall  116  connects the recess top  112  to the lower edge  110 . Lower edge  110  transitions to recess vertical wall  116  at  118 . Recess top  112  has a width about equal to the thickness of lower case  82 . 
     Recess top  112  is preferably not perpendicular to recess vertical wall  116 . Instead, recess top  112  is preferably obtuse to recess vertical wall  116  for a purpose to be explained hereafter. 
     The side wall  92  near the terminal end  94  of the lower case  82  is modified as follows. An inward bend  120  is formed so that the ultimate end  122  of sidewall  92  near terminal end  94  is substantially parallel, although inwardly displaced, to the side wall  92  of lower case  82  opposite inward bend  120 . The amount of displacement of the terminal end  94  of lower case  82  is about equal to the thickness of the upper case  80 . 
     To assemble IIP  10 , the terminal end  94  of lower case  82  is placed in recess  108  so that the terminal end  94  is located approximately at the recess top  112  (FIG.  5 ). In this position, the inner surface  124  of side wall  92  near the terminal end  94  is in contact with the recess vertical wall  116 . In addition, as described above, because recess top  112  is obtuse to the recess vertical wall  116 , the recess top  112  also forms an acute angle with respect to the terminal end  94  of lower case  82 . As a result, there is a space  125  between the terminal end  94  and the recess top  112 . 
     As described above, the terminal end  94  of lower case  82  is placed in recess  108  to so that the terminal end  94  is located approximately at the recess top  112 . Terminal end  94  is attached to bulkhead  50 , preferably by welding, so that a weld  127  fills the space  125  between the terminal end  94  and recess top  112  (FIG.  6 ). Preferably, when space  125  is filled with the weld  127  to connect terminal end  94  to bulkhead  50 , the weld  127  should be about co-linear with the outside surface  126  of the terminal end  94  of lower case  82 . The weld  127  in space  125  forms a seal between bulkhead  50  and the lower case  82 . 
     After lower case  82  has been attached to bulkhead  50  as described above, the upper case  80  is attached to lower case  82 . This is done by moving the terminal end  88  of upper case  80  into contact with the outer surface  126  of the terminal end  94  of lower case  82  so that the inside surface  128  of upper case  80  is in contact with the outside surface  126  of terminal end  94  (FIG.  7 ). Further, the terminal end  88  is moved to approximately the location of inward bend  120 . This produces a space  130  between the terminal end  88  of upper case  80  and the material of lower case  82  near the inward bend  120 . 
     Upper case  80  is attached to lower case  82 , preferably by welding upper case  80  to lower case  82  in space  130  by a weld  131  (FIG.  8 ). Since space  130  extends entirely around the IIP  10 , upper case  80  is attached to lower case  82  by the weld in space  130  entirely around the outer periphery of IIP  10 . Also, the weld in space  130  should attach upper case  80  to lower case  82  and thereby entirely fill space  130  but should not extend above the outer surface  132  of upper case  80  and outer surface  134  of lower case  82 . As a result, upper case  80  is attached to lower case  82  through a single seal formed by the weld in space  130  instead of the two seals  104 ,  106  required by the prior art IIP  10 . 
     A variant of the invention described above is shown in FIG.  9 . In this embodiment, bulkhead  50  is modified so that the annular recess  62  that extends into bulkhead  50  toward top surface  52  does not have an outer vertical wall  67  connected to the horizontal wall  65  at  68 . Instead, horizontal wall  65  extends from the inner vertical wall  64  to the ultimate outer periphery of bulkhead  50 . 
     In this embodiment, recess  108  is shorter than in the embodiment described above. In all other ways, recess  108  and upper and lower cases  80 ,  82  are as structured and connected as described above. 
     In another variant of the invention described above, as shown in FIGS. 10-13, upper case  80  is attached to bulkhead  50  and lower case  82  is attached to upper case  80 . Again, in this embodiment, the outer periphery  56  does not have a protrusion  96 . Instead, outer periphery  56  has an annular recess  136  that extends around the outer periphery  56  at the upper edge  138  of outer periphery  56 . Recess  136  has a recess bottom  140  that is closer to the bottom surface  54  of bulkhead  50  than is the upper edge  138 . A recess vertical wall  142  connects the recess bottom  140  to the upper edge  138 . Upper edge  138  transitions to recess vertical wall  142  at  144 . Recess bottom  140  has a width about equal to the thickness of upper case  80 . 
     Recess bottom  140  is preferably not perpendicular to recess vertical wall  142 . Instead, recess bottom  140  is preferably obtuse to recess vertical wall  142  for a purpose to be explained hereafter. 
     The side wall  86  near the terminal end  88  of the upper case  80  is modified as follows. An inward bend  148  is formed so that the ultimate end  150  of side wall  86  near terminal end  88  is substantially parallel, although inwardly displaced, to upper case  80  opposite inward bend  148 . The amount of displacement of the terminal end  88  of upper case  80  is about equal to the thickness of the lower case  82 . 
     To assemble IIP  10 , the terminal end  88  of upper case  80  is placed in recess  136  so that the terminal end  88  is located approximately at the recess bottom  140  (FIG.  10 ). In this position, the inner surface  152  of side wall  86  near the terminal end  88  is in contact with the recess vertical wall  142 . In addition, as described above, because recess bottom  140  is obtuse to the recess vertical wall  142 , the recess bottom  140  also forms an acute angle with respect to the terminal end  88  of upper case  80 . As a result, there is a space  154  between the terminal end  88  and the recess bottom  140 . 
     As described above, the terminal end  88  of upper case  80  is placed in recess  136  to so that the terminal end  88  is located approximately at the recess bottom  140 . Terminal end  88  is attached to bulkhead  50 , preferably by welding, so that a weld  155  fills the space  154  between the terminal end  88  and recess bottom  140  (FIG.  11 ). Preferably, when space  154  is filled with the weld  155  to connect terminal end  88  to bulkhead  50 , the weld  155  should be about co-linear with the outer surface  156  of the terminal end  88  of upper case  80 . The weld in space  154  forms a seal between bulkhead  50  and the upper case  80 . 
     After upper case  80  has been attached to bulkhead  50  as described above, the lower case  82  is attached to upper case  80 . This is done by moving the terminal end  94  of lower case  82  into contact with the outer surface  156  of the terminal end  88  of upper case  80  so that the inside surface  150  of lower case  82  is in contact with the outer surface  156  of terminal end  88  (FIG.  13 ). Further, the terminal end  94  is moved to approximately the location of inward bend  148 . This produces a space  157  between the terminal end  94  of lower case  82  and the material of upper case  80  near the inward bend  148 . 
     Lower case  82  is attached to upper case  80 , preferably by welding lower case  82  to upper case  80  in space  157 . Since space  157  extends entirely around the IIP  10 , lower case  82  is attached to upper case  80  by a weld  159  in space  157  entirely around the outer periphery of IIP  10  (FIG.  13 ). Also, the weld  159  in space  157  should attach lower case  82  to upper case  80  and thereby entirely fill space  157  but should not extend above the outer surface  134  of lower case  82  and outer surface  132  of upper case  80 . As a result, lower case  82  is attached to upper case  80  through a single seal formed by the weld  159  in space  157  instead of the two seals  104 ,  106  required by the prior art IIP  10 . 
     The description contained herein is intended to be illustrative of the invention and not an exhaustive description. Many variations and alternatives to the disclosed embodiments will occur to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.