Abstract:
Apparatus and methods for coating elongated medical devices, such as guidewires and catheters, incorporating infrared (IR) heating tools for curing the coating while the medical devices are still in place on the coating apparatus. Coating and curing may be accomplished evenly in a dipping machine by utilizing IR heaters having heating heads with openings, the heating heads being mounted for the extension of such elongated medical devices through their openings so that the heating heads are in generally surrounding juxtaposition to the elongated medical devices. The voltage supply to the IR heaters may be selectively adjusted so as to match the wavelength of the generated IR heat to the energy absorbing capability of the particular coating solution being utilized for proper timed absorption of the infrared energy.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention as disclosed relates generally to the application and curing of coatings on elongated, cylindrical shaped or tubular items. In particular, the invention is directed to apparatus and processes for applying coatings to medical devices such as guidewires, catheters and pacemaker leads and for the curing of the applied coating in a very effective and efficient manner.  
       BACKGROUND OF THE INVENTION  
       [0002]     Manufacturers of intravenously insertable medical devices such as guidewires, catheters and pacemaker leads traditionally apply coatings to those medical devices for various purposes. For example, friction reducing coatings are applied to the external surface of catheters and guidewires in order to enhance lubricity to facilitate the insertion of those devices within the veins and arteries of patients.  
         [0003]     It is common practice to move the freshly coated medical devices to remotely located ovens to cure the coating by the application of heat, after the coating process has been completed. This approach to the coating and curing procedure has presented particular difficulties, including damage to the wet or uncured coated devices as they are being transported manually or robotically to curing ovens, as well as the substantial amount of processing time required to move the coated devices into and out of curing ovens. The ovens themselves represent a very substantial capital investment.  
         [0004]     There exists a need for a coating and curing machine and process which is capable of effectively and efficiently coating medical devices and curing the coating at a single workstation by the use of a heating device which can be adjusted to accomplish the proper curing of different coating solutions.  
       SUMMARY OF THE INVENTION  
       [0005]     Having in mind the foregoing shortcomings with respect to existing coating and curing systems for medical devices, I have developed machines and processes for coating elongated, wire-like medical devices such as guidewires, catheters and pacemaker leads, utilizing infrared (“IR”) heating tools. The wavelength of the infrared heat generated during the curing process may be controlled by varying the voltage supplied to the heating tool. This permits matching the infrared wavelength of the heat source to the IR absorption rate of the particular coating solution being utilized to accomplish optimum drying and curing efficiency.  
         [0006]     The infrared heating tools preferably take the form of nickel-chromium heating elements encapsulated in quartz and configured to define an opening within which an elongated medical device may be removably received. The IR heating elements are mounted in a housing which advantageously contains a variable frequency voltage regulator.  
         [0007]     In a preferred embodiment for dip coating applications, an array of the heating tools is mounted on a dip coating machine of the known type in which guidewires or catheters are vertically supported for reciprocal vertical movement, downwardly into receiving coils where they are coated, and upwardly through guide funnels. The wire-like medical devices are coated by dipping them in a curing solution contained within the coil of receiving tubing for each guidewire. The heating tools are positioned to substantially encircle the guidewires, separately, so that as the guidewires are elevated after the coating step, the coating is cured by time-controlled upward movement past the IR heating elements.  
         [0008]     These and other objects and advantages of the invention will become readily apparent as the following description is read in conjunction with the accompanying drawings wherein like reference numerals have been used to designate like elements throughout the several views. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a front perspective view of the coating and curing machine of this invention, showing a carrier bar for elongated medical devices in its raised position;  
         [0010]      FIG. 2  is a front perspective view of the coating and curing machine of  FIG. 1  showing the carrier bar in its lowered, coating position;  
         [0011]      FIG. 3  is a rear perspective view of the coating and curing machine;  
         [0012]      FIG. 4  is a fragmentary, perspective view of a clip device utilized to secure elongated medical devices in place for coating on the machine;  
         [0013]      FIG. 5  is a side elevation view of the coating and curing machine, partially in section, with the carrier bar in its lowered position; and  
         [0014]      FIG. 6  is a perspective view of one of the infrared heating tools utilized to cure the coating. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Referring now to the drawings, there is shown in  FIGS. 1-3  the improved coating and curing machine of this invention, designated by reference numeral  1 . The machine is of the dip coating type utilized for coating elongated medical devices such as guidewires, catheters and pacemaker leads. For that purpose, a mounting member in the form of a vertically movable carrier bar  2  is slidably supported for vertical movement on a pair of vertically extending guide rails  4 ,  6 . Attached to the carrier bar  2  are a plurality of arms  8  serving as support devices for the releasable attachment of a plurality of elongated medical devices  10 . For that purpose, attachment heads  12  are provided on the outer ends of arms  8 . One suitable form of attachment head is shown in  FIG. 4  and comprises a clip having a pair of resilient spring jaws  14 , which may be urged apart for the insertion of an elongated medical device, and which then bias inwardly to provide a friction clamping action. For that purpose, attachment heads  12  may be made out of suitable rubber or plastic material. Alternatively, various forms of spring clips or collets may be used to releasably secure in place the upper ends of elongated medical devices.  
         [0016]     In  FIGS. 1 and 2 , a plurality of elongated medical devices, such as guidewires or catheters  14 , are shown secured in place on support arms  8  in a generally vertical orientation on coating and curing machine  1 . It is to be noted that the coating and curing machine of this invention is adapted to coat wire-like medical devices of any kind, including guidewires, catheters and pacemaker leads which are flexible enough to permit their intravenous insertion in patients.  
         [0017]     For coating purposes in the dip type of coating machine disclosed, one or more coating tubes  16  are provided in the lower tank portion  18  of the machine  1 , as shown in  FIGS. 2 and 5 . Tubes  16  may be configured as coils as shown in  FIG. 5 , or otherwise wound as desired, for example, in a helical configuration. Tubing  16  is flexible, to accommodate the insertion of flexible, wire-like medical devices  10 . Tubing  16  can be made from suitable plastic material. The innermost ends of coating tube  16  are closed, with the upper, receiving ends  20  being open for the reception of wire-like medical devices  10 . At their upper ends, coating tubes  16  are preferably provided with funnels or receiving cups  22 . Tubes  16  are filled through funnels  22  with a desired coating solution. In practice, a particular coating solution will be selected for the particular material and type of medical device being coated. For example, to enhance the lubricity of guidewires and catheters, a coating solution suitable for that purpose will be utilized. Typically, the coating solution may have a silicone base with a solvent added. The solvent serves to create adhesion to the wire-like medical device during a curing process, and the solvent evaporates during curing. The tubes  16  will normally be filled with the coating solution to a level near the top of funnels  22 .  
         [0018]     As may best be understood by reference to  FIGS. 2 and 3 , a drive mechanism is provided for moving carrier bar  2  upwardly and downwardly in sliding movement on guide rails  4  and  6 , carrier bar  2  having bearing blocks  24  and  26  mounted at its opposite ends for that purpose. The drive mechanism may preferably comprise a drive screw  28  on which a follower nut  30  is threadedly engaged. A D.C. drive motor  32  may be mounted as shown at the top of the machine in coupling engagement with screw  28 . As shown in  FIG. 3 , bearings  34  and  36  rotatably support drive screw  28 . Carrier bar  2  is attached to follower nut  30  by a mounting plate or bracket (not shown). The front panel wall  33  of the machine housing is provided with a vertical slot  35  as shown in  FIG. 2  to permit the passage and reciprocal vertical movement of the nut attachment bracket with carrier bar  2 . It will be appreciated that by the use of a reversible drive motor  32 , nut  30  may be made to move upwardly and downwardly on screw  28 , and thus to translate carrier bar  2  in the desired vertical direction for coating and curing.  
         [0019]     The heating and curing of a wet coating applied to wire-like medical devices  10  is advantageously carried out on the same machine  1  in which the coating operation takes place. This is accomplished by the use of one or more infrared (IR) heating tools  38  positioned as shown in  FIGS. 1, 2  and  5  between the movable mounting member or carrier bar  2  and the coating tubes  16 . Preferably, heating tools  38  are positioned at a predetermined, common vertical location, in a generally horizontal plane, so as to locate their heating heads  40  in close proximity to the receiving ends  20  of coating tubes  16 . As shown in  FIGS. 2 and 5 , heating heads  40  are located directly above funnels  22  in proximity thereto.  
         [0020]     As is shown most clearly in  FIG. 6 , the heating tool  38  is preferably contained within a housing  46  having mounting flanges  48  and  50 . Both of those flanges are shown in  FIG. 5 . In the embodiment shown, heating tools  38  are secured in a laterally spaced, fixed vertical position in the arrangement shown in  FIGS. 1, 2  and  5 . The flanges  48 ,  50  of each heating tool are attached by fasteners or adhesive to a vertical bracket plate  52 , with the rear end of bracket plates  52  being secured by welding or otherwise to the front wall panel  33  of the coating and curing machine. Mounting brackets  52  are notched to provide an L-shape, so that the lower end of the mounting brackets can pass under carrier bar  2  when it is in its lowermost position as shown in  FIGS. 2 and 5 . It is to be understood that rather than firing the heating tools  38 , they can be mounted for vertical movement so as to achieve the desired relative movement between the coated wire-like devices and the heating heads to accomplish heating and curing of the applied coating.  
         [0021]     Referring again to  FIG. 6 , it will be seen that the heating tool  38  is provided with a pair of heating elements  40 ,  42 . Those heating elements are preferably of the type comprising nickel chromium wire heating elements encased in quartz tubes, such heating elements being commercially available from Eraser International Ltd. of Andover, England. The heating elements  40  and  42  are preferably arcuate shaped as shown to define an opening therebetween into which and through which a wire-like medical device may be inserted. The split ring configuration of the heating elements shown in  FIG. 6  permits the wire-like medical devices to be inserted between the split-apart ends of the heating elements and into the opening between the two heating elements. As shown in  FIGS. 1 and 2 , one or more of the wire-like medical devices  10  may be removably attached at their upper ends to attachment heads  12  and positioned within the apertured heating elements  42 ,  44  of heating heads  40 . In the mounting of the wire-like devices, their lower ends are centered within funnels  22  of coating tubes  16 .  
         [0022]     In the course of a coating and curing operation, one or more of the wire-like medical devices  10  is first removably secured as described to the support arms  8 . At this time, carrier bar  2  will be at its elevated position as shown in  FIG. 1 . Each of the coating tubes  16  will have been filled to near the top of funnels  22  with a desired coating solution appropriate for the particular devices being coated. Motor  32  of the drive mechanism is then actuated to rotate screw  28  in such a direction that follower nut  30  translates downwardly, and carries bar  2  with it. In this way, the wire-like devices such as catheters or guidewires are lowered into coating tubes  16 . After the medical devices have remained in the coating solution within the tubes  16  for a predetermined period of time, the heating tools  38  are electrically actuated so that the heating elements  42 ,  44  generate IR heat energy. Drive motor  32  is then again actuated in a reverse direction to raise carrier bar  2  and to lift the coated medical devices  10  vertically and withdraw them from the coating tubes  16 . The speed of drive motor  32  is closely controlled to provide a predetermined extraction rate of the coated medical devices. That rate will be very slow, such as on the order of two inches per second. The extraction rate of the medical devices, in combination with the time during which they are left in the coating solution within tubes  16  controls the wall thickness of the coating applied. A complete, even coating is provided over the entire outer surface of the wire-like medical devices.  
         [0023]     The centering of the wire-like devices within the apertured heating heads  40  ensures the even application of infrared heat around the entire peripheral surface of those devices so as to get even heating and curing of the coating. As the medical devices pass through the heating heads, between arcuate heating elements  42  and  44 , the heating and curing of the applied coating is carried out, with that process being completed, by the timed elevation of carrier bar  2 , when that bar reaches the top extremity of its travel path as shown in  FIG. 1 .  
         [0024]     The timing interval for dip coating within the coating tubes  16 , as well as the sequential, timed actuation of the IR heaters and the lift motor may be controlled by a programmable timer. Heating elements  42 ,  44  may be energized a few seconds before motor  32  or substantially simultaneously therewith, at the beginning of the medical device extraction and lift cycle. Alternatively, actuation of the drive motor  32  on the lowering and raising cycles, and of the heating tools may be accomplished manually.  
         [0025]     As an advantageous feature, a voltage regulator is provided within housing  46  of the heating tool  38 . Such a voltage regulator is indicated by reference numeral  54  in  FIG. 6 . Preferably, the voltage regulator is of the adjustable frequency type. The voltage regulators of each of the heating tools  38  are connected to a common power supply or bus bar  56 , as indicated schematically in  FIG. 6 . A programmable, frequency modulated voltage regulator incorporating a microprocessor may be utilized. For that purpose, a signal receiving window  58  is provided in the sidewall of housing  46  to receive signals from a remote computer or CPU. Such a computer may be utilized to initially program the voltage regulator within a frequency range to determine the parameters of the infrared heat energy generated. Also, the remote computer may then be utilized, on site, to send a signal adjusting the frequency, and thus the voltage output of voltage regulator  54 , so as to generate infrared energy at a desired frequency. This is particularly beneficial because it permits adjusting the infrared heat generated by the heating tools to a particular wavelength matching or compatible with the infrared absorption rate of the particular coating solution applied. In this way, manufacturers of coated medical devices may establish effective quality control of the heating and curing process so as to ensure even and complete heating and curing of the applied coating.  
         [0026]     After the coating and curing process has been completed on machine  1 , the coated and cure-dried medical devices may be quickly and easily removed by releasing attachment heads  12 . Efficiencies of coating and curing elongated devices are achieved by incorporating the heating and curing tools in the same machine within which the coating operation takes place.  
         [0027]     It will be understood by those skilled in the art that the coating and curing apparatus, and related process, disclosed herein may be modified in various ways without departing from the spirit and scope of the invention as defined by the following claims.