Coating processes – Medical or dental purpose product; parts; subcombinations;...
Reexamination Certificate
2002-06-04
2003-07-29
Barr, Michael (Department: 1762)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
C427S002240, C427S008000, C427S358000, C427S434200, C427S434400, C427S434600
Reexamination Certificate
active
06599557
ABSTRACT:
BACKGROUND
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.
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.
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.
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.
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
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.
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.
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.
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.
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 b
Biagtan Emmanuel
Burkett David
Advanced Cardiovascuslar Systems, Inc.
Barr Michael
Fulwider Patton Lee & Utecht LLP
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