Abstract:
A method and apparatus for applying a polymer coating on an elongated substrate, preferably an elongate intracorporeal device in the form of a guidewire. An extrudable polymer cartridge is moved by a cartridge advancement mechanism into a guide chamber which is heated at an end with a die or orifice through which a desired portion of a guidewire may pass and be coated. Parameters such as guide chamber temperature, pull speed and force exerted by the cartridge advancement mechanism may be controlled with a computer program in order to achieve repeatable results. The guide chamber, extrudable polymer cartridge, die, and push tube may all be made from polymer components which can be reused or disposed of after a single use. The extrudable polymer cartridge may have a variety of configurations including multiple layers of different materials, eccentric shapes, multiple lumens for multiple elements to be drawn through and coated and asymmetric disposition of different materials with respect to the longitudinal axis as viewed in a transverse cross section which can give bending properties having a preferred direction in the coated guidewire or device.

Description:
BACKGROUND  
         [0001]    This invention relates to an apparatus and method for applying a polymer coating to a desired length of an elongate member, preferably to an elongate intracorporeal device. More specifically, the invention relates to a method and apparatus for applying a polymer coating to a desired length of an intracorporeal guiding device or guidewire. The invention can also be used to apply a polymer coating to a length of any other suitable device such as a vascular stent, cardiac pacing leads, catheter tubings, braided or solid electrical wire, coaxial cable or the like.  
           [0002]    In a typical prior art process for applying a polymer coating over an elongate member, an extrusion machine is used which has a heated die head with channels leading to a heated chamber within the die head. Melted polymer is forced into the chamber with a lead screw which forces solid polymer, usually in the form of pellets, into the heated chamber. The elongate member to be coated is passed through the back end of the die head into the chamber and out of an orifice in an extrusion die which is attached to the extrusion head. The elongate member is then pulled through the die as melted polymer is forced into the die head and onto the elongate member. Normally, the orifice in the die will be larger than the elongate member so that a desired amount of the melted polymer remains on the elongate member after passing through the orifice. After passing through the orifice, the melted polymer on the elongate device cools and the coating process is complete.  
           [0003]    A prior art process such as that described above is well suited in many cases for coating long lengths of durable elongated members or substrate. The equipment used is large, expensive and cumbersome and can damage a fragile substrate being pulled through the device, such as a guidewire distal section with a small diameter helical coil. In addition, the amount of effort and expense required for a given set up often does not justify small runs of material. Also, the equipment is not well suited for coating short lengths of discrete elongated members, such as guidewires or the like, because adjusting the settings to achieve desired coating dimensions and parameters is usually a process that requires several minutes of running time in order for equilibrium of the dynamic to be established and stabilization of the process to occur. This often requires running many feet of substrate through the die head prior to stabilization which is not possible with a guidewire which is only several feet long.  
           [0004]    Another difficulty exists in trying to vary the coating parameters dynamically in a controlled fashion in order to achieve a coating which has varying parameters such as a transverse dimension along an axial direction. As mentioned above, the usual coating equipment of the prior art is large and cumbersome and it is impractical to vary parameters such as temperature of the die, speed of pull, and pressure exerted on the melted polymer over short lengths of an elongate member substrate.  
           [0005]    What has been needed is an apparatus suitable for applying a variety of polymer coatings to a discrete length of a fragile intracorporeal device substrate with quick response time for variation in extrusion parameters. What has also been needed is an apparatus suitable for coating an elongate intracorporeal member that has automatable control of extrusion parameters such as die temperature, pull speed and pressure applied to melted polymer which can produce repeatable control of diameter and other dimensions of the polymer coating applied. In addition, it is desirable to have an apparatus suitable for reliably applying a polymer coating with a constant outer transverse dimension to a substrate which varies in transverse dimension or diameter along its axial length.  
         SUMMARY  
         [0006]    The invention is directed to an apparatus for applying a polymer coating to an elongate intracorporeal device, specifically, a guidewire. In one embodiment, the apparatus can have a guide chamber with an input end having an input port and an output end. An extrusion orifice is disposed at the output end of the guide chamber and is in fluid communication with the guide chamber. The extrusion orifice can be configured to allow an elongate intracorporeal device or other substrate to pass through or be pulled through the extrusion orifice with a desired thickness or configuration of polymer coating on the elongate intracorporeal device or substrate. The orifice can be configured to leave a fixed thickness of polymer over the elongate intracorporeal device, or the orifice can be shaped so as to leave a desired profile or configuration of polymer coating on the device, e.g., an orifice having an oval, square or triangular cross section.  
           [0007]    A heater member is disposed in thermal communication with the guide chamber and serves to heat a desired portion of the guide chamber. A cartridge advancement mechanism is disposed adjacent the guide chamber. In use, an extrudable polymer cartridge is placed within the guide chamber of the apparatus. The cartridge advancement mechanism can be configured to axially translate the extrudable polymer cartridge into the guide chamber in a direction of extrusion, i.e., a direction from the input end of the guide chamber to the output end of the guide chamber. The extrudable polymer cartridge can have a lumen extending longitudinally through the cartridge with the lumen being sized or configured to accept the elongate intracorporeal device. The lumen of the extrudable polymer cartridge is typically sized to allow the elongate intracorporeal member to slide freely within the lumen.  
           [0008]    In another embodiment, a guide chamber is formed by a guide tube with the guide chamber being disposed within the guide tube. The guide tube has an input end with an input port in fluid communication with the guide chamber and an output end. A die having an extrusion orifice is disposed at the output end of the guide tube such that the extrusion orifice is in fluid communication with the guide chamber. The extrusion orifice of the die can be configured to allow an elongate intracorporeal device to pass through the die with a desired configuration of polymer coating on the member. A heater member is disposed in thermal communication with the guide tube for heating a desired portion of the guide tube or die.  
           [0009]    A push tube is disposed at least partially and slidably within the guide chamber. The push tube has a contact end, an attachment end, a longitudinal axis and at least one inner lumen extending substantially parallel to the longitudinal axis of the push tube. The inner lumen of the push tube is configured to accept a desired elongate intracorporeal device. In use, an extrudable polymer cartridge, having similar properties to the extrudable polymer cartridge discussed above, can be disposed within the guide chamber between the extrusion orifice of the die and the contact end of the push tube.  
           [0010]    In another embodiment, a puller is disposed adjacent the output end of the guide tube. The puller can be configured to be temporarily secured to a desired portion of the elongate intracorporeal device and apply a force and movement in the direction of extrusion on the device. A push tube actuator is disposed adjacent the input end of the guide tube and is configured to apply a force and movement on the extrudable polymer cartridge disposed within the guide chamber. Specifically, the push tube is disposed between the extrudable polymer cartridge and the push tube actuator and mechanically couples the push tube actuator to the extrudable polymer cartridge. A computing machine may be electronically connected to a temperature sensor coupled to the heater member, the puller and the push tube actuator. The computing machine can be used to repeatably control the temperature of the heating member, the rate of axial movement of the elongate intracorporeal device in a direction of extrusion by controlling the rate of axial movement of the puller, and the rate of feed or axial movement in the direction of extrusion of the extrudable polymer cartridge by controlling the rate of movement or force applied to the push tube in the direction of extrusion.  
           [0011]    One of the advantages of the apparatus for applying a polymer coating is that many of the components of the apparatus can be manufactured from disposable polymer materials that are made to be modular and avoid the need for cleaning of components. For example, both the guide tube and the die can be made from a variety of high temperature polymers such as polyimide (PI), polytetraflouroethylene (PTFE), liquid crystal polymer (LCP) and polyetheretherkeytone (PEEK). This allows a subassembly consisting of the guide tube, die and extrudable polymer cartridge to be loaded into a corresponding guide tube assembly for each elongate intracorporeal device to be coated. When the device has been coated, the subassembly can be disposed of and a new subassembly loaded into the guide tube assembly. This eliminates the need for time consuming cleaning operations and allows the use of varying die configurations and extrudable polymer cartridge materials from one elongate intracorporeal device to the next.  
           [0012]    Another advantage of the apparatus for applying a polymer coating is the ability to reliably maintain concentricity of the coating applied to the elongate inctracorporeal device. Where such concentricity is desired, the use of an extrudable polymer cartridge having an inner lumen which is concentric to a longitudinal axis of the cartridge provides centering of the elongate intracorporeal device prior to passing through the extrusion orifice. As the extrudable polymer cartridge is melted at the output end of the guide chamber and applied to the elongate intracorporeal device, the unmelted portion of the cartridge immediately adjacent a melt zone of the extrudable polymer cartridge continuously provides centering of the elongate intracorporeal device within the guide chamber and extrusion orifice. Also, the melted portion of the extrudable polymer cartridge at the melt zone can be applied evenly in a radially inward direction from all sides of the elongate intracorporeal device in embodiments of the invention where the inner lumen of the extrudable polymer cartridge is concentric with the longitudinal axis of the cartridge. This can also facilitate maintaining concentricity of the polymer coating.  
           [0013]    In use, an extrudable polymer cartridge is placed in the guide chamber of the guide tube between the extrusion orifice and the contact end of the push tube. An elongate intracorporeal device is loaded into the die, at least of a portion of the inner lumen of the extrudable polymer cartridge and optionally the inner lumen of the push tube. The elongate intracorporeal device is then temporarily secured to the puller and the heater member activated. When the portion of the extrudable polymer cartridge adjacent the die attains a desired temperature and viscosity, the puller and cartridge advancement mechanism, typically consisting of a push tube actuator, are activated. This advances both the elongate intracorporeal device and extrudable polymer cartridge in the direction of extrusion, i.e. in a direction from the input end of the guide chamber to the output end of the guide chamber.  
           [0014]    The coating process can be terminated in several ways. The process may be terminated when an end or extremity of the elongate intracorporeal device is drawn through the output end of the guide chamber and die. This method will typically coat the entire end or extremity of the elongate intracorporeal device. Alternatively, the advancement of the extrudable polymer cartridge can be stopped by deactivating the cartridge advancement mechanism while continuing to advance the elongate intracorporeal device in the direction of extrusion. In this way, the melted extrudable polymer cartridge is no longer feeding into the extrusion orifice and coating the elongate intracorporeal device. Also, the amount of material in the extrudable polymer cartridge may be limited to suffice for coating only a desired portion of an elongate intracorporeal device. As the extrudable polymer cartridge is advanced in the direction of extrusion and polymer coating is applied, the cartridge gets shorter. The process continues until the contact end of the push tube hits the die and melted polymer material is no longer fed into the extrusion orifice and the coating process stops, although the elongate intracorporeal may continue to be pulled or advanced in the direction of extrusion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is an elevational view in partial section of an apparatus for applying a polymer coating to an elongate intracorporeal device having features of the invention.  
         [0016]    [0016]FIG. 2 is an elevational view in partial section of the guide tube assembly shown in FIG. 1 taken along lines  2 - 2  in FIG. 1.  
         [0017]    [0017]FIG. 3 is a transverse cross sectional view of the guide tube assembly shown in FIG. 2 taken along lines  3 - 3  in FIG. 2.  
         [0018]    [0018]FIG. 4 is a transverse cross sectional view of the guide tube assembly shown in FIG. 2 taken along lines  4 - 4  in FIG. 2.  
         [0019]    [0019]FIG. 5 is an elevational view in longitudinal cross section of the die in the guide tube assembly shown in FIGS.  1 - 4 , having features of the invention.  
         [0020]    FIGS.  6 A- 6 C are transverse cross sectional views of the die shown in FIG. 5 taken along lines  6 - 6  in FIG. 5, having various extrusion orifice configurations.  
         [0021]    [0021]FIG. 7 is an elevational view in partial section of a tandem apparatus for applying a polymer coating to an elongate intracorporeal device having features of the invention.  
         [0022]    [0022]FIG. 8 illustrates an elevational view in section of a guide tube assembly having features of the invention.  
         [0023]    [0023]FIG. 9 is a transverse cross sectional view of the guide tube assembly of FIG. 8 taken along lines  9 - 9  in FIG. 8.  
         [0024]    [0024]FIG. 10 illustrates an extrudable polymer cartridge having features of the invention.  
         [0025]    [0025]FIG. 11 is a transverse cross sectional view of the extrudable polymer cartridge of FIG. 10 taken along lines  11 - 11  in FIG. 10.  
         [0026]    [0026]FIG. 12 illustrates an extrudable polymer cartridge having features of the invention.  
         [0027]    [0027]FIG. 13 is a transverse cross sectional view of the extrudable polymer cartridge of FIG. 12 taken along lines  13 - 13  in FIG. 12.  
         [0028]    [0028]FIG. 14 illustrates an extrudable polymer cartridge having features of the invention.  
         [0029]    [0029]FIG. 15 is a transverse cross sectional view of the extrudable polymer cartridge of FIG. 14 taken along lines  15 - 15  in FIG. 14.  
         [0030]    [0030]FIG. 16 illustrates an extrudable polymer cartridge having features of the invention.  
         [0031]    [0031]FIG. 17 is a transverse cross sectional view of the extrudable polymer cartridge of FIG. 16 taken along lines  17 - 17  in FIG. 16.  
         [0032]    [0032]FIG. 18 illustrates an extrudable polymer cartridge having features of the invention.  
         [0033]    [0033]FIG. 19. is a transverse cross sectional view of the extrudable polymer cartridge of FIG. 18 taken along lines  19 - 19  in FIG. 18. 
     
    
     DETAILED DESCRIPTION  
       [0034]    FIGS.  1 - 4  illustrate a polymer coating apparatus  10  for applying a polymer coating  11  to an elongate intracorporeal device  12 . A guide tube assembly  13  is removably secured to a guide tube assembly mount  14 . The guide tube assembly mount  14  is secured to a mounting surface  15 , which can be an even vertical surface, but which can have any desired configuration or orientation. A heater member  16  is secured in thermal communication with a guide tube housing  17  of the guide tube assembly  13  and serves to supply heat energy to a desired portion of the guide tube assembly  13 . The guide tube assembly  13  includes a guide tube housing  17  which has an input end  18  and an output end  19 . The output end  19  has a threaded portion  22  and the input end  18  has a retainer lip  23 . A retainer cap  24  is threaded onto the threaded portion  22  of the output end  19  of the guide tube housing  17 .  
         [0035]    The guide tube housing  17  can be made of a conductive material such as stainless steel, a machineable insulative material such as Vespel® or any other suitable material. A guide tube  25  having an input end  26  , an output end  27  and a guide chamber  28  disposed within the guide tube  25  is disposed within the guide tube housing  17 . The input end  26  of the guide tube  25  is disposed against the retainer lip  23  of the guide tube housing  17 . A die  31  having an input end  32  and an output end  33  is disposed within the guide tube housing  17  with the input end  32  of the die  31  against the output end  27  of the guide tube  25 . An optional centering insert  34  having an input end  35  and an output end  36  is disposed within the guide tube housing  17  with the input end  35  of the centering insert  34  against the output end  33  of the die  31 . The retainer cap  24  with a center hole  37  is threaded onto the threaded portion  22  of the guide tube; housing  17  to hold the guide tube  25 , die and centering insert  34  within the guide tube housing  17 .  
         [0036]    In one embodiment, the guide tube  25  has a length of about 0.5 to about 5 inch, specifically about 1.0 to about 3.0 inch. The guide tube  25 , die  31  and centering insert  34  can have an outer diameter of about 0.03 to about 0.2 inch, specifically about 0.05 to about 0.1 inch. The guide tube  25  of the embodiment can have a wall thickness of about 0.005 to about 0.015 inch. In other embodiments, the length, outer diameter and wall thickness of the guide tube  25  can vary significantly from the dimensions given above to suit the desired application. The guide tube  25 , die  31  and centering insert  34  can be disposable and made from a high temperature polymer such as PI, PTFE, LCP or PEEK.  
         [0037]    As best shown in FIG. 1, a puller  40  is disposed adjacent an output end  41  of the guide tube assembly  13  and has a clamp  42  aligned with the longitudinal axis  43  of an inner lumen  44  of the die  31  for temporarily securing the elongate intracorporeal device  12  to the puller  40 . The clamp  42  temporarily secures a desired portion of the elongate intracorporeal device  12  to the puller  40  such that the elongate intracorporeal device  12  is centered within the inner lumen  44  of the die  31 . The puller  40  is slidably disposed on a puller track  45  and has motor  46  which mechanically engages the puller track  45  and moves the puller  40  parallel to a longitudinal axis  47  of the guide tube assembly  13 .  
         [0038]    A cartridge advancement mechanism  51  consisting of a push tube actuator  52  and a push tube  53  is disposed adjacent an input end  54  of the guide tube assembly  13 . The push tube actuator  52  is mechanically coupled to the push tube  53  with the push tube  53  having a contact end  55  and an actuator end  56 . The push tube  53  is configured to have the contact end  55  slidably disposed within the guide chamber  28  of the guide tube  25  and apply force to an extrudable polymer cartridge  57  disposed within the guide chamber  28  in a direction of extrusion. The direction of extrusion is defined to be from the input end  54  of the guide tube assembly  13  to the output end  41  of the guide tube assembly  13  as indicated by arrows  58 .  
         [0039]    The push tube actuator  52  is slidably disposed on a push tube actuator track  61  such that a longitudinal axis  62  of an inner lumen  63  of the push tube  53  is aligned with the longitudinal axis  43  of the die  31  and longitudinal axis  64  of an inner lumen  65  of the extrudable polymer cartridge  57 . A push tube actuator motor  66  is disposed on the push tube actuator  52  and mechanically coupled to the push tube actuator track  61  so as to enable the motor  66  to axially translate the push tube actuator  52  on the push tube actuator track  61  along a longitudinal axis  47  of the guide tube assembly  13 .  
         [0040]    The elongate intracorporeal device  12  is disposed within an inner lumen  67  of the centering insert  34 , the extrusion orifice  68  of the die  31 , the inner lumen  65  of the extrudable polymer cartridge  57  and the inner lumen  63  of the push tube  53 . The elongate intracorporeal device  12  is also shown as being disposed along the longitudinal axis  47  of the guide tube assembly  13 . Other configurations may be used where the elongate intracorporeal device  12  is offset from the longitudinal axis  47  of the guide tube assembly  13 .  
         [0041]    A computer  71  is in electrical communication with an electronic control unit  72  which is in electrical communication with a temperature sensor  73  disposed in thermal communication with the heater member  16 , a puller position indicator  74  disposed on the puller  40 , and a push tube actuator position indicator  75  disposed on the push tube actuator  52 . The temperature sensor  73  provides an electrical signal to the computer  71  indicating the temperature of the heater member  16 . The puller position indicator  74  provides an electrical signal to the computer  71  indicating the position of the puller  40  relative to the output end  41  of the guide tube assembly  13 . The push tube actuator position indicator  75  provides an electrical signal to the computer  71  indicating the position of the push tube actuator  52  relative to the input end  54  of the guide tube assembly  13 . In addition, the computer  71  is electrically coupled to the control unit  72  such that a signal from the computer  71  can control the amount of power to the heater member  16 , the speed and direction of translation of the puller  40  and the speed and direction of translation of the push tube actuator  52 .  
         [0042]    In this way, the computer  71  can be programmed to repeatably control the temperature of the heater member  16 , the rate of pull of the elongate intracorporeal device  12  through the guide tube assembly  13  and the rate of feed of the extrudable polymer cartridge  57  into the guide chamber  28  in the direction of extrusion. This enables the computer  71  to repeatably control the entire coating process for consistent coating results. The computer  71  may be a standard personal computer, or any suitable substitute such as a custom integrated circuit or the like. In addition, the function of the computer  71  could be carried out with standard analog circuitry of suitable configuration that would provide a desired and repeatable heater member  16  temperature, rate of pull of the puller  40  and rate of feed of the push tube actuator  52 .  
         [0043]    In use, the retainer cap  24  is removed from the guide tube housing  17 . The guide tube  25  is loaded into the guide tube housing  17  from the output end  19  of the guide tube housing  17  until the input end  26  of the guide tube  25  contacts the retainer lip  23  of the guide tube housing  17  and the contact end  55  of the push tube  53  enters the guide tube chamber  28  at the input end of the guide tube  25 . The extrudable polymer cartridge  57  is then loaded into the guide chamber  28  at the output end of the guide tube  25  until it contacts the contact end  55  of the push tube  53 . Next, the die  31  is loaded into the guide tube housing  17  with the input end  32  of the die  31  adjacent the output end  27  of the guide tube  25 . The centering insert  34  is then loaded into the guide tube housing  17  with the input end  35  of the centering insert  34  adjacent the output end  33  of the die  31 . The retainer cap  24  is then replaced which confines the guide tube  25 , extrudable polymer cartridge  57 , die  31  and centering insert  34  within the guide tube housing  17 .  
         [0044]    The elongate intracorporeal device  12  is then inserted through the inner lumen  67  of the centering insert  34 , the extrusion orifice  68  and inner lumen  44  of the die, the inner lumen  65  of the extrudable polymer cartridge  57 , and at least a portion of the inner lumen  63  of the push tube  53 . The elongate intracorporeal device  12  is then temporarily secured to the puller  40  by the clamp  42 . The coating cycle is then started by supplying power to the heater member  16  which heats a desired portion of the die  31 , guide tube  25  and extrudable polymer cartridge  57  which are adjacent and in thermal communication with the heater member  16 .  
         [0045]    Thermal energy from the heater member  16  may be coupled to the die  31  alone, the die  31  and the output end  27  of the guide tube  25  or the die  31  and any desired portion of the guide tube  25 . Also, it may be useful in some embodiments to generate a temperature gradient along the centering insert  34 , die  31  and guide tube  25 . In one embodiment, it is preferable to concentrate most of the thermal energy on the die  31  and output end  27  of the guide tube  25 .  
         [0046]    As thermal energy is transferred to the extrudable polymer cartridge  57 , it can begin to soften or melt at a melt zone  57 A. When the portion of the extrudable polymer cartridge  57  adjacent the die  31  approaches a desired temperature or viscosity or both, force in the direction of extrusion is applied to the extrudable polymer cartridge  57 . This pushes the melted or softened polymer material in the melt zone  57 A of the extrudable polymer cartridge  57  into the input end  32  and inner lumen  44  of the die  31  and onto the elongate intracorporeal device  12 . When the force in the direction of extrusion is initiated on the extrudable polymer cartridge  57 , the elongate intracorporeal device  12  is simultaneously advanced in the direction of extrusion so that as the extrudable polymer cartridge  57  is heated, melted, and forced into the die  31 . The melted extrudable polymer cartridge  57  is applied to the moving elongate intracorporeal device  12  in a radially inward direction as indicated by arrows  57 B. As shown in FIG. 2, the extrudable polymer cartridge  57  is applied evenly at the melt zone  57 A from all directions as indicated by arrows  57 B. The evenly distributed inward radial force helps maintain the concentricity of the polymer coating  11  if the lumen of the extrudable polymer cartridge is concentric with the longitudinal axis  64  of the extrudable polymer cartridge  57  and longitudinal axis  43  of the die  31 . The coating process is carried out continuously until a desired portion of the elongate intracorporeal device  12  has been coated. The process may be terminated by exhaustion of the extrudable polymer cartridge  57 , cessation of the force in the direction of extrusion on the extrudable polymer cartridge, or passage of an extremity  76  of the elongate intracorporeal device  12  through the die  31 .  
         [0047]    In the embodiment of the polymer coating apparatus  10  shown in FIG. 14, the force in the direction of extrusion on the extrudable polymer cartridge  57  is applied by the contact end  55  of the push tube  53  which is mechanically coupled to the push tube actuator  52 . One alternative to using push tube actuator motor  66  to apply force and motion to the push tube actuator  52  is to apply a substantially constant force in the direction of extrusion on the push tube actuator  52  with an optional constant force spring  77 . The constant force spring  77  may be secured to any suitable portion of the push tube  53 , push tube actuator  52 , guide tube assembly mount  14 , or mounting surface  15 . A suitable trigger mechanism can be used to initiate the force from the constant force spring  77  in the direction of extrusion at the appropriate time in the coating cycle.  
         [0048]    When the coating cycle is finished, the elongate intracorporeal device  12  is removed from the guide tube assembly  13  and the puller  40 . The retainer cap  24  of the guide tube housing  17  is removed as well as the spent die  31 , centering insert  34 , guide tube  25  and extrudable polymer cartridge  57 . The push tube  53  is then reset to its original position and a new guide tube  25 , extrudable polymer cartridge  57 , die  31  and centering insert  34  loaded into the guide tube housing  17 . It may be possible to reuse the die  31 , guide tube  25  or centering insert  34 . Also, the new guide tube  25 , die  31  and extrudable polymer cartridge  57  may be loaded into the guide tube housing  17  in one connected modular unit or subassembly in order to lessen the time between coating cycles.  
         [0049]    The temperature range of the heater member  16 , die  31  and desired portion of the guide tube  25  used for the process of the polymer coating apparatus  10  can vary significantly depending on the desired result, size and material composition of the elongate intracorporeal device  12  and material composition of the extrudable polymer cartridge  57 . For coating an elongate intracorporeal device  12  consisting of a guidewire, in order to yield a finished outer diameter of about 0.012 to about 0.016 inch, a temperature range of about 340 to about 390 degrees Fahrenheit, specifically about 350 to about 380 degrees Fahrenheit is typical if using polyurethane for the extrudable polymer cartridge  57  material.  
         [0050]    As the temperature of the heater member  16  is changing as the coating process is started, it may be desirable to trigger axial movement of the elongate intracorporeal device  12  in the direction of extrusion just prior to reaching the desired target temperature. For example, if the ultimate target temperature of the heater member  16  is about 365 degrees Fahrenheit, then the puller  40  may be triggered by programming of the computer  71  to start the puller  40  moving in the direction of extrusion when the heater member  16  reaches a temperature of about 362 degrees Fahrenheit.  
         [0051]    The rate of speed of pull of the elongate intracorporeal device  12  through the guide tube assembly  13  can vary considerably depending on many factors including the size and durability of the elongate intracorporeal device  12 , the temperature of the heater member  16  and the material of the extrudable polymer cartridge  57 . For the example given above, with an elongate intracorporeal device  12  of stainless steel having a desired finish outer diameter of about 0.012 to about 0.016 inch, using polyurethane for the extrudable polymer cartridge  57 , a typical rate of pull can be from about 0.25 to about 1.0 cm/second for durable portions of the member  12 , and about 0.05 to about 0.15 cm/second for more fragile portions of the member  12 , such as portions of the elongate intracorporeal device  12  covered by a helical coil which is subject to mechanical deformation. In one embodiment, the force applied to the extrudable polymer cartridge  57  by the push tube  53  via the push tube actuator  52  can be from about 0.5 to about 10 pounds, specifically about 1.0 to about 2.0 pounds.  
         [0052]    In another embodiment, the cartridge advancement mechanism  51 , described above as consisting of a push tube actuator  52  coupled to a push tube  53  can be replaced with a substantially constant force spring coupled to the push tube so as to apply a substantially constant force in the direction of extrusion on the extrudable polymer cartridge  57  during the coating process. The amount of force can be similar to the forces noted above with regard to the push tube actuator  52  embodiment.  
         [0053]    FIGS.  5  -  6 C illustrate an enlarged view of the embodiment of the die  31  shown in FIGS. 2 and 4. The die  31  can be made from a variety of materials, including high temperature polymers such as PI, PTFE, LCP and PEEK. The die  31  can also be made from metal or any other suitable material. The die  31  has an input end  32 , an output end  33  and an inner lumen  44 . An extrusion orifice  68  is disposed at an output extremity  78  of the inner lumen  44 . The length  79  of the inner lumen  44  of the die  31  can vary significantly depending on the desired result and numerous other factors. In one embodiment, the length of the inner lumen  44  can range from about 0.02 to about 0.5 inch, specifically about 0.05 to about 0.08 inch. A transverse dimension of the inner lumen  44  and extrusion orifice  68  of the die  31  in said embodiment can be from about 0.01 to about 0.25 inch, specifically about 0.011 to about 0.015 inch.  
         [0054]    The die  31  has an outer transverse dimension similar to an outer transverse dimension of the guide tube  25 . An input taper  81  at the input end  32  of the die  31  has an input taper angle  82 . An optional output taper  83  at the output end  33  of the die  31  has an output taper angle  84 . Output taper angle  84  and input taper angle  82  can be from about 15 degrees to about 180 degrees, i.e. a flat cut end with no taper, specifically, from about 35 to about 45 degrees, and more specifically, from about 36 to about 40 degrees. Although the extrusion orifice  68  of the die  31  shown in FIG. 5 has a round cross section as shown in FIG. 6A, the cross section of the extrusion orifice  68  can have any desired configuration or shape such as the square configuration shown in FIG. 6B or the elliptical configuration shown in FIG. 6C. Any other suitable extrusion orifice  68  configuration or cross sectional shape can be used to achieve a desired result.  
         [0055]    [0055]FIG. 7 illustrates a tandem polymer coating apparatus  86  having a first polymer coating apparatus  87  in line with a second polymer coating apparatus  88 . The various components of the first and second polymer coating apparatus  87  and  88  can have components similar to the components of the polymer coating apparatus  10  of FIGS.  1 - 4 , and are numbered accordingly. A single puller  89  can be used for the tandem polymer coating apparatus  86  . By using a tandem coating apparatus  86 , multiple layers of polymer coating may be applied to a single elongate intracorporeal device  12  by drawing the elongate intracorporeal device  12  through the first and second polymer coating apparatus  87  and  88  in serial in a direction of extrusion indicated by arrow  91 . Multiple coatings may be applied so as to be axially coextensive on the elongate intracorporeal device  12 . Multiple coatings may also be applied to separate axial portions of an elongate intracorporeal device  12  or such that the multiple coatings overlap each other by a desired amount. Although FIG. 7 depicts a tandem coating apparatus  86  having two polymer coating apparatus  87  and  88  in serial, any desired number of polymer coating apparatus may be used.  
         [0056]    [0056]FIGS. 8 and 9 illustrate another embodiment of a guide tube assembly  95  having features of the invention. The guide tube assembly  95  includes a guide tube  96  having an input end  97  and an output end  98  disposed partially within a guide tube housing  101 . The guide tube  96  can be made from a variety of polymer materials, specifically, high temperature polymer materials such as PI, PTFE, LCP and PEEK. The guide tube housing  101  has an input end  102  and an output end  103 . The guide tube housing  101  also has a central inner lumen  104  which is configured to accept the guide tube  96 . The central inner lumen  104  of the guide tube housing  101  has a retainer lip  105  at the input end  102  of the guide tube housing  101  which is configured to prevent the guide tube  96  from exiting the input end  102  of the guide tube housing  101  without blocking or interfering with a guide chamber  106  disposed within the guide tube  96 . The central inner lumen  104  of the guide tube housing  101  is capped at the output end  103  with a retainer cap  107 . The retainer cap  107  has a retainer cap top  108 , a threaded portion  109  and a retainer cap insert  112 . The retainer cap  107 , when secured to the guide tube housing  101 , confines the output end  98  of the guide tube  96  within the central inner lumen  104  of the guide tube housing  101 .  
         [0057]    Disposed within the output end  98  of the guide tube  96  is a die  113  which has an input end  114  and an output end  115  and which can have the same configuration, dimensions and materials as the die  31  shown in FIGS.  5 - 6 C. Disposed within the guide tube  96  adjacent the input end  114  of the die  113  is an extrudable polymer cartridge  116  having an input end  117  and an output end  118 . An inner lumen  121  extends along a longitudinal axis  122  of the extrudable polymer cartridge  116 . A push tube  123  having a contact end  124  and an actuator end  125  is disposed within a guide chamber  126  of the guide tube  96  with the contact end  124  adjacent the input end  117  of the extrudable polymer cartridge  116 . A push tube actuator rod  127  with an actuator rod tip  128  is disposed partially within the guide chamber  126  with the actuator rod tip  128  disposed adjacent the actuator end  125  of the push tube  123 .  
         [0058]    A heater member  131  is disposed within the guide tube housing  101  about the output end  98  of the guide tube  96 . The heater member  131  has a heater member housing  132 , heater rods  133  and heater lead wires  134  which supply power to the heater rods  133 . The heater member housing  132  can be made from stainless steel or any other suitable material which can withstand high temperatures. It may be desirable to use a material which readily conducts heat for the heater member housing  132 . The heater member  131  is held in place within the guide tube housing  101  by a guide tube housing cap  135  disposed at the output end  103  of the guide tube housing  101 .  
         [0059]    The guide tube housing cap  135  can be secured to the guide tube housing  101  by screws  136 . The guide tube housing  101  has cooling air channels  137  disposed within the housing  101  fed by air lines  138  to allow air to be circulated about the heater member  131  and cool the heater member  131  after a polymer coating process has been completed. Thereafter, a new guide tube  96 , die  113 , extrudable polymer cartridge  116  and push tube  123  can be inserted into the guide tube assembly  95 . The optionally disposable components of the guide tube assembly  95  including the guide tube  96 , die  113 , extrudable polymer cartridge  116  and push tube  123  may be replaced separately, or all at once as a modular subassembly.  
         [0060]    The guide tube  96 , die  113 , extrudable polymer cartridge  116  and push tube  123  are replaced by removing the retainer cap  107 , withdrawing the spent guide tube  96 , die  113 , extrudable polymer cartridge  116  and push tube  123 , and then replacing a new guide tube, die, extrudable polymer cartridge and push tube. The retainer cap  107  is then secured to the guide tube housing  101 .  
         [0061]    The guide tube housing  101 , guide tube housing cap  135  and retainer cap top  108  can all be made from a high strength machineable polymer insulator, such as Vespel® which is a polyimide resin based composite, or any other suitable material. An insulative material can be used for the guide tube housing  101 , guide tube housing cap  135  and retainer cap top  108  in order to facilitate handling by the operators of the device who must handle the various components of the polymer coating apparatus during its operation.  
         [0062]    The guide tube assembly  95  shown in FIGS. 8 and 9 is used in a manner similar to that discussed above with regard to the embodiment of the guide tube assembly  13  shown in FIGS.  1 - 4 . The coating process parameters discussed above with regard to the embodiment of the guide tube assembly  13  shown in FIGS.  1 - 4 , including, but not limited to, temperatures, pull speeds, rates of feed, forces on the extrudable polymer cartridge  57 , and the like, and structures and alternative structures used to implement those parameters, can all be the same or similar for the embodiment of the guide tube assembly  95  shown in FIGS. 8 and 9.  
         [0063]    FIGS.  10 - 19  illustrate various configurations of extrudable polymer cartridges having features of the invention. Specifically, FIGS. 10 and 11 illustrate an extrudable polymer cartridge  141  having an input end  142  , an output end  143  , and a plurality of longitudinal segments  144  which may be made of polymers having different compositions. Polymer composition of the longitudinal segments  144  may vary in material type, shore hardness, color, radiopaque doping concentrations and the like. An inner lumen  145  extends from the input end  142  to the output end  143  and is concentric with a longitudinal axis  145 A of the extrudable polymer cartridge  141 . The extrudable polymer cartridge  141  can be molded with the longitudinal segments  144  molded into place adjacent each other. Alternatively, the longitudinal segments  144  could be molded or extruded separately, and subsequently bonded or fused together. Also, the longitudinal segments  144  could be molded or extruded separately and put into a guide chamber  28  or  126  of the invention without being bonded or fused together.  
         [0064]    As used herein, the term polymer, as used with regard to polymer coatings, cartridges and the like, is intended to be interpreted broadly and include all polymers, prepolymers and the like which are suitable for use as a coating of an elongate intracorporeal device. Some materials suitable for the extrudable polymer cartridge  141 , and all extrudable polymer cartridges discussed herein, can include polyurethanes, including polyurethane thermoplastic elastomers; polyamides (nylons); polyethers; polyesters; polyacetals; acrylics; methacrylics; cellulosics; fluoropolastics; epoxies; keton-based resins and polymers; polyimide based resins and polymers; bismaleimides; nitrites; polyarylates; polycarbonates; liquid crystal polymers; terephthalate resins and polymers including polybutylene terephthalate and polyethylene terephthalate; polyetherimides; polyolefins including polyethylenes, polypropylenes, polybutylenes, polybutadienes; polyvinyls including polystyrenes and polyvinyl chlorides; elastomers especially thermoplastic elastomers; silicones; rubbers; ionomers; ceramers; dendritic polymers; and derivatives, copolymers, multipolymers, blends and/or mixtures of any of the previous listed resins and polymers within each group and between each group. This latter includes polyether block amide elastomers such as COPA and PEBAX.  
         [0065]    Any of the aforementioned polymers may be loaded with additives to control the physical properties such as flexural modulus, hardness, and radiopacity. The shore hardness of an embodiment of extrudable polymer cartridge  141  and embodiments of other extrudable polymer cartridges discussed herein can range from about 50A to about 55D, preferably about 80A to about 50D, and more preferably about 85A to about 95A.  
         [0066]    [0066]FIGS. 12 and 13 show an extrudable polymer cartridge  146  having an input end  147 , an output end  148 , a first lateral segment  149  and a second lateral segment  150 . An inner lumen  151  extends from the input end  147  to the output end  148  and is concentrically located within the extrudable polymer cartridge  146 . The extrudable polymer cartridge  146  can be formed by molding or extruding the cartridge  146  in its final form. In addition, the first and second lateral segments  149  and  150  could be formed independently and then fused or bonded together, or placed within a guide chamber  28  or  126 of the invention together without being fused or bonded together.  
         [0067]    [0067]FIGS. 14 and 15 illustrate an extrudable polymer cartridge  153  having an input end  154  and an output end  155  with an inner lumen  156  extending from the input end  154  to the output end  155 . The inner lumen  156  has a longitudinal axis  157  which is substantially parallel to a longitudinal axis  158  of the extrudable polymer cartridge  153  and laterally offset from the longitudinal axis  158  of the extrudable polymer cartridge  153 .  
         [0068]    [0068]FIGS. 16 and 17 show an extrudable polymer cartridge  161  having an input end  162  and an output end  162 . The extrudable polymer cartridge  161  has a first concentric layer  164  and a second concentric layer  165  disposed about the first concentric layer  164  . An inner lumen  166  extends from the input end  162  to the output end  163  and is disposed concentrically within the extrudable polymer cartridge  161 . The first concentric layer  164  may have a different polymer composition from the second concentric layer  165 .  
         [0069]    [0069]FIGS. 18 and 19 show an extrudable polymer cartridge  167  having an input end  168  and an output end  169 . A first inner lumen  170  extends from the input end  168  to the output end  169  which may be disposed substantially concentric within the extrudable polymer cartridge  167  and which is substantially parallel to a longitudinal axis  171  of the extrudable polymer cartridge. A second inner lumen  172  extends from the input end  168  to the output end  169  and is also substantially parallel to the longitudinal axis  171  of the extrudable polymer cartridge  167 . The second inner lumen  172  has a longitudinal axis  173  which is offset from the longitudinal axis  171  of the extrudable polymer cartridge  167 . The first inner lumen  170  would can encompass an elongate intracorporeal device during an extrusion process. The second inner lumen  172  could be used to encompass a secondary elongate element such as a wire, fiberoptic, small diameter tubing or the like. The use of such an extrudable polymer cartridge  167  would facilitate application of a polymer coating to a plurality of elongate members which could be drawn through guide chambers  28  or  126  and extrusion orifice  68  during a coating process.  
         [0070]    Unless otherwise described herein, conventional materials and manufacturing methods may be used to make the guiding members of the present invention. Additionally, various modifications may be made to the present invention without departing from the scope thereof. While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.