Abstract:
A medical device known as an implantable infusion device is configured for implanting in humans to deliver a therapeutic substance such as pharmaceutical compositions, genetic materials, and biologics to treat a variety of medical conditions such as pain, spasticity, cancer, and many other conditions. The infusion device incorporates a motor coil connector and mechanical sealing system between the clean motor compartment and the potentially corrosive pump compartment that provides a reliable electrical connection between the motor coil and the motor drive electronics. The motor coil connector provides for bonding of a very small diameter coil wire to one end of the connector and a highly corrosion resistant connection at the other end of the connector. Additionally, the motor coil connector and mechanical sealing system provides a seal against harmful corrosion materials that could emanate from the pump compartment and reach the motor compartment and cause malfunction of the motor. The infusion device has a housing, a power source, a therapeutic substance reservoir, a therapeutic substance pump, and electronics.

Description:
FIELD OF THE INVENTION 
     This disclosure relates to a medical device and more particularly to an implantable infusion device also known as an implantable therapeutic substance infusion device or simply an implantable drug pump. More particularly, the invention relates to methods and apparatus for connecting a motor coil to a motor drive circuit while providing sealing against potentially harmful corrosive materials. 
     BACKGROUND OF THE INVENTION 
     Previously the medical device industry has produced a wide variety of electronic and mechanical devices for treating patient medical conditions. Depending upon medical condition, medical devices can be surgically implanted or connected externally to the patient receiving treatment. Clinicians use medical devices alone or in combination with therapeutic substance therapies and surgery to treat patient medical conditions. For some medical conditions, medical devices provide the best, and sometimes the only, therapy to restore an individual to a more healthful condition and a fuller life. One type of medical device is an implantable infusion device. 
     An implantable therapeutic substance infusion device is implanted by a clinician into a patient at a location appropriate for the therapy. Typically, a therapeutic substance infusion catheter is connected to the device outlet and implanted to infuse the therapeutic substance such as a drug or infusate at a programmed infusion rate and predetermined location to treat a condition such as pain, spasticity, cancer, and other medical conditions. Many therapeutic substance infusion devices are configured so the device can be refilled with therapeutic substance through a septum while the device is implanted. Then the time the device can be implanted may not be limited by therapeutic substance stored capacity of the device. An example of an implantable therapeutic substance infusion device is shown in Medtronic, Inc. product brochure entitled “SynchroMed® Infusion System” (1995). 
     The therapeutic substance infused into a patient is stored in the pump in a sealed reservoir. The substance in the reservoir flows from the reservoir via internal fluid handling components to the motor and pump components where it is metered and then flows to the pump output. 
     In a peristaltic pump the substance flows through a compressible tube, one of several fluid handling components, and this tube is slightly permeable to water, and possibly some compounds and ions. Water vapor and other materials that may diffuse through the tube walls and become trapped inside the pump may be corrosive to mechanical or electrical components inside the pump. In particular, electrical components such are electronic circuits and motors are particularly vulnerable to damage and loss of function due to certain types of contamination. 
     Electrically powered implanted infusion devices consume energy delivered typically by a battery, also called a power source. Wires and connections inside the pump carry electrical energy from the power source to the motor. These wires and connections must be designed to be isolated from corrosive materials or made impervious to corrosion by corrosive materials. If this corrosion immunity is not accomplished, the pump will likely need to be replaced due to malfunction prior to the end of its normal service life. Replacement usually requires a costly, inconvenient and potentially problematic surgery for the patient and attending physician. For these reasons there is a need for a pump with various components of the motor coil connector and sealing system inside the pump that are carefully designed to eliminate or minimize potentially detrimental corrosive effects from corrosive materials. 
     BRIEF SUMMARY OF THE INVENTION 
     In a preferred embodiment of an implantable therapeutic substance infusion device motor connector and sealing system, a motor coil connector is configured to provide corrosion resistant reliable electrical connection and mechanical sealing between the clean motor compartment and the potentially corrosive pump compartment. The motor coil connector provides for bonding of a very small diameter motor coil wire to one end of the connector and a highly corrosion resistant connection to the motor drive electronics at the other end of the connector. Additionally in cooperation with the motor coil connector, a motor cover and mechanical sealing o-ring provides a seal against harmful corrosion materials that could emanate from the pump and reach the motor area to cause malfunction of the motor. The infusion device has a housing; a power source; a therapeutic substance reservoir configured for containing a therapeutic substance and being refilled with the therapeutic substance while implanted; a therapeutic substance pump fluidly coupled to the therapeutic substance reservoir, and electrically coupled to the power source; and, electronics electrically coupled to the power source and coupled to the therapeutic substance pump. The electronics include a processor; memory coupled to the processor; an infusion program residing in memory, the infusion program capable of being modified once the infusion device is implanted; and, transceiver circuitry coupled to the processor for externally receiving and transmitting infusion device information. Many embodiments of the therapeutic substance delivery device with motor connection and seal system and its methods of operation are possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the environment of an implantable infusion device embodiment; 
         FIG. 2  shows an implantable infusion device embodiment; 
         FIG. 3  shows an implantable infusion device with catheter embodiment; 
         FIG. 4  shows an exploded view of an implantable infusion device with peristaltic pump embodiment; 
         FIG. 5  shows a schematic block diagram of an implantable infusion device with major electronic blocks embodiment; 
         FIG. 6  shows a block diagram of the electrical connections between the power source and the motor embodiment; 
         FIG. 7  shows a cross section of the motor coil connector assembly embodiment; 
         FIG. 8  shows a cross section of the motor coil connector assembly installed with the motor cover and electrical connections inside the device embodiment. 
         FIG. 9  shows a flow chart for a method to electrically connect and mechanically seal a pump motor coil. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the environment of an implantable medical device known as an implantable therapeutic substance delivery device  30 , also known as a drug pump, having a peristaltic pump with motor connector and seal system embodiment. The therapeutic substance delivery device  30  operates to infuse a therapeutic substance  36  stored in therapeutic substance reservoir  44  at a programmed flow rate into a patient  38 . The therapeutic substance delivery device  30  can be used for a wide variety of therapies such as pain, spasticity, cancer, and many other medical conditions. 
     The implantable therapeutic substance delivery device  30  is typically implanted by a surgeon in a sterile surgical procedure performed under local, regional, or general anesthesia. Before implanting the therapeutic substance delivery device  30 , a catheter  32  is typically implanted with the distal end position at the desired therapeutic substance delivery site  34  and the proximal end tunneled to the location where the therapeutic substance delivery device  30  is to be implanted. The implantable therapeutic substance delivery device  30  is generally implanted subcutaneous about 2.5 cm (1.0 inch) beneath the skin where there is sufficient tissue to support the implanted system. Once the therapeutic substance delivery device  30  is implanted into the patient  38 , the incision can be sutured closed and the therapeutic substance delivery device  30  can begin operation. 
       FIG. 2  shows an implantable therapeutic substance delivery device  30  with motor connector and seal system embodiment with housing  41  and fill port septum  40 .  FIG. 3  shows implantable therapeutic substance delivery device  30  connected to catheter  32  prior to implantation into a patient  38  by a surgeon. 
     The therapeutic substance  36  in pump reservoir  44  inside the pump is a substance intended to have a therapeutic effect such as pharmaceutical compositions, genetic materials, biologics, and other substances. Pharmaceutical compositions are chemical formulations intended to have a therapeutic effect such as intrathecal antispasmodics, pain medications, chemotherapeutic agents, and the like. Pharmaceutical compositions are often configured to function in an implanted environment with characteristics such as stability at body temperature to retain therapeutic qualities, concentration to reduce the frequency of replenishment, and the like. Genetic materials are substances intended to have a direct or indirect genetic therapeutic effect such as genetic vectors, genetic regulator elements, genetic structural elements, DNA, and the like. Biologics are substances that are living matter or derived from living matter intended to have a therapeutic effect such as stem cells, platelets, hormones, biologically produced chemicals, and the like. Other substances are substances intended to have a therapeutic effect yet are not easily classified such as saline solution, fluoroscopy agents, and the like. 
     The therapeutic substance  36  in reservoir  44  can be replenished in some embodiments of the implanted therapeutic substance delivery device  30  by inserting a non-coring needle connected to a syringe filled with therapeutic substance  36  through the patient&#39;s skin into a fill port septum  40  on the therapeutic substance delivery device  30  to fill the implanted device. The contents of the syringe are then injected into the pump reservoir  44 . 
     If the therapeutic substance delivery device  30  requires replacement due to conditions such as power source depletion or other condition, an incision is made near the implanted therapeutic substance delivery device  30 , and the old therapeutic substance delivery device  30  is removed, also known as explanted. After the old therapeutic substance delivery device  30  has been explanted, typically a new therapeutic substance delivery device  30  is then implanted. 
       FIG. 4  shows an exploded view of an implantable therapeutic substance infusion device with motor connection and sealing system comprised of a housing  41 , a power source  42 , a therapeutic substance reservoir  44 , a therapeutic substance pump  46 , and electronics  48 . The housing  41  is manufactured from a material that is biocompatible and hermetically sealed such as titanium, tantalum, stainless steel, plastic, ceramic, and the like. The power source  42  is carried in the housing  41 . The power source  42 , selected to operate the therapeutic substance pump  46  and electronics  48 , may be a lithium ion (Li+) battery, a capacitor, and the like. 
     The therapeutic substance reservoir  44  is carried in the housing  41  and is configured to contain therapeutic substance  36 . The therapeutic substance reservoir  44  is refillable with therapeutic substance  36  while implanted. The therapeutic substance pump assembly  46  is carried in the housing  41 , and is fluidly coupled to the therapeutic substance reservoir  44  and electrically coupled to the power source  42 . The therapeutic substance pump assembly  46  is a pump sufficient for infusing therapeutic substance  36  such as the peristaltic pump with stepper motor drive that can be found in the SynchroMed® Infusion System available from Medtronic, Inc. 
     A stepper motor is an electromechanical device whose rotor rotates a discrete angular amount when an electrical drive pulse is applied to the stator windings. The amplitude and the width of the pulse must be tailored to the electromechanical properties of the motor in order to achieve rotation, rotational stability, and optimal energy consumption. An example is a motor that rotates 180 degrees with the application of a 3 volt, 11.2 millisecond, square pulse. A second pulse is then applied at minus 3 volts to rotate an additional 180 degrees making a complete revolution. 
     The stepper motor is mechanically coupled by gears to the peristaltic roller pump where the rollers rotate in such a way as to squeeze a compressible tube and drive liquid through the tube lumen in one direction. In effect the therapeutic substance  36  from the reservoir  44  flows in the tube and is metered to the patient  38  via catheter  32  to anatomical sight  34 . 
       FIG. 5  shows a block diagram device embodiment. Carried in the housing  41  are the electronics  48 , including the motor drive circuit  620 , coupled to the therapeutic substance pump  46  and the power source  42 . The electronics  48  include a processor  61 , memory  63  coupled to the processor  61 , an infusion program, and transceiver circuitry  62 . The processor can be a microprocessor, an application specific integrated circuit (ASIC) state machine, a gate array, a controller, and the like. The electronics  48  are configured to control the therapeutic substance pump assembly  46  infusion rate and can be configured to operate many other features such as patient alarms and the like. The infusion program and other device parameters and patient information reside in memory  63  and are capable of being modified once the therapeutic substance infusion device is implanted. The transceiver circuitry  62  is coupled to the processor  61  for externally receiving and transmitting therapeutic substance infusion device information. 
       FIG. 6  shows a block diagram of pump motor electrical connections between the power source  610  and the pump motor  660  with respect to the related motor components. Electrical wires  611  connect the power source  610 , carried in housing  41 , to motor drive circuit  620 . Similarly, electrical wires  621  connect the motor drive circuit  620  to motor drive connectors  630 . Motor drive connectors  630  incorporate standard high reliability feed thru technology and maintain a hermetic seal between the motor drive circuit and the peristaltic pump compartment  640 . 
     The peristaltic pump compartment  640  must be traversed by the electrical wires  631  in order to conduct electrical energy to drive the pump motor  660 . The peristaltic pump compartment  640  may have entrapped water vapor as well as ions or compounds which may be corrosive to the electrical wires  631  and  651 , motor coil connector assembly  650 , and pump motor  660 . The connector pin assembly  650  is positioned between the pump compartment  640  and the motor compartment  670 . The entrapped materials are possible due to diffusion of components of the therapeutic substance through the flexible peristaltic pump tube in the pump assembly. The configuration described as follows strives to eliminate or minimize potential corrosion. 
     The motor pin connector assembly  650  and the pump motor cover  641  serve to seal the pump motor  660  and wires  651  from the corrosive pump compartment  640 . Since water vapor, ions, and compounds are sealed from the motor compartment  670 , the potential for corrosion of the pump motor  660  and wires  651  is greatly reduced. Since wires  631 , preferably platinum or similar conductor, and motor drive circuit connectors  630  all are selected to be corrosion resistant, the potential for corrosion in the motor compartment  640  of these important electrical connections is eliminated. 
       FIG. 7  shows the motor pin connector assembly  650  prior to insertion into the therapeutic substance infusion device. The preferred embodiment is an assembly with two of pin  710  in the same assembly. An alternative configuration would be two assemblies with each having a single pin  710 . The motor pin connector assembly  650  is composed of a plastic insulator  750  and two phosphor-bronze pins  710 , two platinum lead wires  631  and two sealing o-rings  740 . In each implantable therapeutic substance infusion device there is one motor pin connector assembly  650  component. 
       FIG. 8  shows motor pin connector assembly  650  inserted into the ferro-magnetic motor coil core  810  where a seal  811  is made at the interface between  650  and  810 . To complete the sealing, the pump motor cover  641  is bonded in place to compress sealing o-ring  740  against motor coil connector assembly  650 . Then the potentially corrosive environment of the pump compartment  640  is sealed from the corrosion vulnerable pump motor compartment  670 . 
     To electrically connect the motor coil  820 , a very small diameter (less than 0.005 inch) motor coil wire  830  is bonded to a much larger (greater than 0.02 inch diameter) motor connector pin  710 . The pin  710  is chosen to accommodate a reliable bond of the very small diameter motor coil wire. The important challenging transition from a very small diameter motor wire to much larger more robust wires in the pump is achieved by configuring the motor connector assembly to include this purpose. The motor pin connector assembly  650  then serves to make the transition from the very small motor coil wire  830  to a much larger diameter motor lead wire  631 . To complete the motor drive wire connections, the motor lead wire  631  integral to the motor pin connector assembly  650  is connected to the motor drive connector  630  that in turn connects to the motor drive circuit  620  via wire  621 . 
       FIG. 9  shows a flow chart for a method to electrically connect and mechanically seal a motor coil. This is result of each of the following 5 steps is illustrated in  FIG. 8 . 
     The first step  910  is attaching a motor coil connector assembly  650  into a motor housing  810 . The next step  920  is bonding a motor coil wire  830  to a connector pin  710 . The third step  930  is bonding a lead wire  631  to a motor drive circuit terminal  630 . The fourth step  940  is placing a motor cover  641  on the motor assembly while contacting the O-ring  740 . The fifth and final step  950  is compressing the O-ring  740  with the motor cover  641  in order to complete the motor connection and seal system  960 . 
     The various components and connections described above comprise a method to electrically connect and mechanically seal a pump motor coil  820 , assuring adequate electrical motor drive is achieved while the motor is safeguarded in a clean motor compartment  670 , isolated from the corrosive pump compartment  640 . In particular, liquid, large molecules and ions may reside in the corrosive pump compartment  640 . These substances are sealed from the corrosion sensitive materials and components such as gears, shafts, bearings, and lubricant in the motor compartment  670 . 
     Thus, embodiments of the implantable infusion device with motor connection and seal system to eliminate or minimize potentially detrimental corrosive effects from corrosive materials is disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiment is presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.