MXPA97010061A

MXPA97010061A - Beeting of catheters by gradiente term

Info

Publication number: MXPA97010061A
Application number: MXPA/A/1997/010061A
Authority: MX
Inventors: Douglas Field J; Ahlstrom Roger
Original assignee: Johnson & Johnson Medical Inc
Priority date: 1996-12-13
Filing date: 1997-12-11
Publication date: 1999-01-11

Abstract

The present invention relates to a method for forming a beveled tip in a catheter, said method being characterized in that it comprises the steps of: a) placing a tubular catheter in a pin that extends inside said tubular catheter in such a way that said pin extends beyond the tip of the catheter, b) heating a mold having an internal surface complementary to a desired external beveled tip surface of the catheter, said mold when heated has a high temperature zone and a low temperature zone away from said high temperature zone c) inserting the pin and the catheter together inside said mold in such a way that the pin reaches at least one distal end of the internal surface to form a space defined at least partially by the pin and the internal surface, d) continue to advance said catheter inside the space in such a way that the high temperature zone causes the material of the catheter softens and flows until said material makes contact with the zone of low temperature, said zone of low temperature causes that the material becomes more viscous and acts as a dike avoiding additional flow of said material and allowing the formation of the tip beveled without excessive burring and; e) removing said catheter from the mole

Description

BISELPDQ OF CATHETERS BY THERMAL GRADIENT FIELD OF THE INVENTION The present invention relates to methods for forming ducts, such as catheters, with a bevelled tip, in order to facilitate insertion; and, in particular, relates to methods for forming beveled tips in intravenously inserted intravenous catheters.

BACKGROUND OF THE INVENTION It has long been known that a beveled tip in a peripherally inserted catheter is an advantage in that it facilitates the insertion of the catheter into a patient's body. Intravenous catheters are used to infuse blood, plasma, drugs or other fluids into a patient's body, as well as to draw blood or allow the introduction of other objects, such as minor catheters, through an opening in the skin. When they are manufactured as original preforms, the catheters are cut from piping material or are extruded from said materials. The tubing material, or the extruded catheter tube frequently has a blunt tip, abrupt end, which would cause trauma when inserted. Accordingly, many peripherally inserted catheters are beveled, from a distance from the distal tip; for example, a three-degree taper may be used, and a taper at the 27-degree end, since a small portion of the varied tip is used to facilitate insertion when a needle passes into the patient, carrying the tube. of catheter. Many methods for tapering a catheter tip are known in the art; for example, U.S. Patent No. 4,661,300, entitled "nethod and flparatus for Flashless Tipping of an IV Catheter" ("Method and apparatus for non-lost tip formation in an intravenous catheter") shows a method of molding in which one end of the catheter US Pat. No. 5,397,512, 5,425,903 and 5,404,422 show a laser method for forming a beveled tip in a catheter, wherein the taper of tree degrees is initially formed in a catheter and the taper is formed posterior 27 degrees by means of a laser that makes contact with the catheter tube and that erodes the surface in order to form the necessary taper.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to the provision of a thermal gradient within a mold to form catheter tips. The thermal gradient is such that, in a first portion of the mold, a portion of higher temperature is provided, which causes the polymeric material of the catheter tube to melt and flow. A second portion of lower temperature is provided, which allows the flowing polymeric material to become more viscous or to begin to re-harden and act as a containment to prevent further flow of the polyrnomeric material present in the mold. In order to achieve this, a mandrel or needle is used to position and support the catheter tube to which the tip is to be formed; a tip former die which is tapered in its internal configuration is heated. The tip former die has been provided with an external configuration that can provide sufficient heating to melt the catheter and also allow rapid cooling to allow at least a portion of the mold to cool. This mold is mounted on a carriage that moves towards the mandrel or the needle. The mandrel or needle moves through the entire die until it protrudes and the hot die acts to soften the catheter tube material and then is cooled to allow the material to fill the entire internal space of the die. Air-focused cooling can be used in a concurrent manner to rapidly cool the material, which creates the change in viscosity necessary to allow complete filling of the internal die shape. The external shape provides the thermal gradient that will be created within the internal configuration of the mold. This allows the material to be heated to flow and be cooled quickly to fill the internal space of the die. The tip forming die can be configured with two or more materials of different thermal conductivity, in an alternative way, to provide the thermal gradient for plastic types to stop the flow within the die. Historically, focused heating can provide precise placement of the heating source, which will allow the entire internal configuration of the die to be filled without creating any loss.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the appended figures, in which: Figure 1 is a sectional view of a mold and a mandrel used in a tip forming operation. Figure 2 is a sectional view of a tipped catheter formed using the method of the present invention. Figure 3 is a partial sectional view, enlarged to show the tip area of the mold used in the method of the present invention; and Figure 4 is a sectional view of an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY As part of a normal function, catheter former, a catheter preform is formed having a body that fits in the shape of a hub connected to a distally extending tubular portion, which is intended to be received within the body of a catheter. patient. This preform, before having a necessarily beveled tip provided therein, is used as a material that goes into the operation of the present invention. The preform is received on a concentric pin. For example, for a 20 gauge catheter, a pin of 0.716 nm in size is inserted into the catheter tube and extends beyond the end of the catheter. Preferably the pin is made of stainless steel or other metallic material that can be machined with precision in terms of size and shape. Preferably the material of the pin is softer than the material of the mold, which reduces the damage or wear to the mold. The catheter tube 1 and the pin 2 are moved concurrently with one another, substantially as a unit, at least in one embodiment of the present invention. A mold 3 having at least two portions is provided: a portion 4 of higher temperature and a portion 5 of lower temperature are separated, for example, by means of a ceramic insulator 6. The portion of higher temperature 4 is preferably made of stainless steel or other conductive metal and is selected in terms of its characteristics as a mold material and, at the same time, in terms of its thermal conductance and its retention (ie, its specific heat). The insulator 6 (FIG. 4) is preferably ceramic and is selected so as to decrease or prevent the transfer of heat from the higher temperature portion 4 to the lower temperature portion 5. Preferably the lower temperature portion 5 is made of ceramic (Figure 1) or titanium alloy (Figure 4), such as an alloy with 6% aluminum, 4% vanadium; and is selected from a size that has a lower thermal mass than portion 4 of higher temperature. The portion 5 of lower temperature has an opening 7 defined therein, through which the pin 2 will pass. If a pin with a size of 0.716 mm is used, an opening with a diameter of 0.723 rnm in diameter is formed, for provide a free space for the pin and to allow air and gas to escape as the plastic advances in the mold. The inner surface 8 of the high temperature portion has formed therein a cylindrical surface 9 and a tapered surface 10. The tapered surface 10 is formed to the shape of a cone having a three degree taper, thus forming a smooth taper towards the end of the catheter material, when molded. Part 5 of lower temperature can be made ceramic, thus eliminating the need for a separate ceramic insulator. The inner surface 11 of the portion of lower temperature has formed in it a frustoconical surface 12, complementary to a tapered portion at 27 °, desired in the distal tip of the catheter. As can be seen now, when the pin 2 is in place within the mold 3, the outer surface of the pin 2 forms, together with the cylindrical surface 9, the tapered surface 10 and the tapered surface 12, a shape having a space that forms the desired tip configuration of the catheter. That is to say, the inner surfaces of the mold and the outer surface of the pin form complementary surfaces for the catheter to be formed. The mold 3 has a tapered outer surface 13. As can be seen in Figure 1, the tapered outer surface 13 has a portion with a small relief, formed adjacent to the portion 5 of lower temperature. A heating block 14 is provided for heating the mold. The heating block 14 is constructed as a large thermal mass in order to rapidly transfer the heat to the mold. The mold 3 is received within a complementary taper within the heating block, so that the outer surface 13 makes contact with the heating block and, therefore, receives heat transfer from the heating block to the mold. The space 5fl between the lower temperature portion 5 and the heating block prevents or substantially reduces the amount of heat transferred from the heating block to this portion of the mold. When the lower temperature portion is made of ceramic, the space 5fl is advantageous but it is more advantageous in the embodiment of figure 4. As it can be easily seen, therefore, once the mold is heated to its proper temperature, the higher temperature portion has received a portion of the heat transferred from the heating block while the lower temperature portion has received a reduced portion of very little heat transfer from the heating block. In that way, the mold is brought to a condition having a temperature gradient from the portion 4 of higher temperature to the portion 4 of lower temperature. The mold and the heating block are shown in contact during the molding operation in the figures. However, in use, they are separated prior to insertion of the catheter to allow cooling of the mold to re-solidify the polymer. After the complete molding operation, the mold is again brought into contact with the heating block to heat it for the next molding operation. In a preferred embodiment for a catheter made of ethylene / propylene fluoropolymer material, the higher temperature portion is approximately 301-343 ° C and the lower temperature portion is approximately 55.5 ° C lower. Subsequently, the pin 2 is inserted inside the mold. In a preferred embodiment, the pin has previously received the catheter tube 1 therein, and when the pin passes through the mold and exits at the distal end of the mold (i.e., the end adjacent to the lower-temperature portion) , the catheter material is forced into the space defined by the pin and the cylindrical surface 9, the tapered surface 10 and the tapered surface 12. The catheter is made of a thermoplastic material, such as a fluorinated ethylene / propylene or polyurethane. In the case of a fluorinated ethylene / propylene polymer material, having a softening temperature of 287 ° C, the highest temperature portion of the mold is heated to approximately 301-343 ° C. When it contacts, or is moving in the vicinity of this higher temperature portion, the catheter tube 1 softens and begins to flow. As used here, flowing does not necessarily imply the meaning of a liquid state; but rather a malleable state that allows easy plastic deformation of the material due to heating and softening of the material. As the catheter is advanced within the mold space, the flowing catheter material extends along and conforming to the tapered surface 10 until it meets the inner surface 11. The inner surface 11 is at a sufficient temperature less than the inner surface 10, to allow the catheter material to begin to harden again, or at least become more viscous than in the high temperature portion 4 of the mold. In this way, the material that is received along the interior surface 11 begins to act as a retention that prevents the additional flow of the material and allows the total filling of the mold itself without excessive loss. The pin 2 is selected to be slightly smaller than the opening 7 and can pass through it with a slight clear. This light clearing allows the escape of the gases that are in front of the catheter material, inside the mold. However, the mold material does not flow beyond the interior surface 11, since the colder temperature causes the catheter material to flow more viscous and, therefore, less susceptible to escape. through the small clear provided in the tip of the mold. It can be easily seen that the high temperature and low temperature portions of the mold can be provided merely by the shape of the mold, rather than by different materials. For example, the low temperature portion of the mold may have fins cut into it, so as to favor the cooling of the mold in that area, while the high temperature portion of the mold has a large thermal mass to provide a deposit of thermal energy, thereby decreasing its cooling capacity. In that way, the cooled area of the low temperature portion of the mold would provide the temperature gradient from the higher temperature portion, surrounded by the thermal mass, in order to create the dam effect of the flowing thermoplastic material. In an alternative embodiment, the pin 2 may be permanently located within the mold or may be passed through the mold from the distal end, inside the mold; so that the catheter is subsequently placed on the pin, passing the tip of the pin through the distal end of the catheter material, sliding the catheter along the pin until it engages the inner surface of the mold, and further forcing the catheter inside the mold, so that the softened material flows from the higher temperature portion to the lower temperature portion. After the formation of the catheter end product, the pin can be removed through the upper part of the mold (the end of the distal mold of the catheter insert) and subsequently, or before removal of the pin, the cast catheter. The invention has been described above with reference to its preferred embodiments. The claims that follow are directed to the invention; however, many variations can be made with respect to those described in the preferred embodiment, while retaining the spirit and scope of the claims that follow.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. A method for forming a beveled tip in a catheter, characterized in that it comprises: a) placing a pin in a tubular catheter, so that the pin extends beyond the tip of the catheter; b) heating a mold having an internal surface complementary to the desired external tip surface of the catheter; said mold has a zone of higher temperature and a zone of lower temperature, away from the zone of higher temperature; c) inserting the pin and the catheter into the mold, so that the pin reaches at least one distal end of the mold-forming surface to form a space defined at least partially by the pin and the surface of the mold; d) continue advancing the catheter inside the space, so that said area of higher temperature causes the material of the catheter to soften and flow until the material makes contact with the area of lower temperature, with which the material of the catheter stops flow.

2. The method according to claim 1, further characterized in that the mold is heated by contacting an outer surface of the mold with a heating block at a temperature higher than the mold, to transfer the heat to the mold.

3. The method according to claim 2, further characterized in that the mold is made of a first material in the area of higher temperature and a second material that has lower thermal conductance, in the area of lower temperature.

4. The method according to claim 2, further characterized in that the mold is formed to provide less heat transfer from the heating block to the zone of lower temperature, than the transfer of heat to the zone of higher temperature.

5. The method according to claim 2, further characterized in that the mold is formed to cool the zone of lower temperature faster than the zone of higher temperature.

6. The method according to claim 4, further characterized in that the mold makes contact with the heating block along said zone of higher temperature and does not contact the heating block along the zone of lower temperature.

7. The method according to claim 1, further characterized in that the pin and the catheter are removed from the mold.

8. The method according to claim 1, further characterized in that the pin is removed from the mold and the catheter is then removed from the mold.

9. The method according to claim 1, further characterized in that the mold has an insulating zone between the high temperature zone and the low temperature zone.

10. A method for forming a beveled tip in a catheter, characterized in that it comprises: a) heating a mold having an internal surface complementary to the desired external tip surface of the catheter; the mold has a pin that extends from it, to receive said catheter therein; the hot mold has a zone of higher temperature and a zone of lower temperature, away from the zone of higher temperature; b) inserting the pin into a tubular catheter and advancing the catheter into the mold; c) continue advancing the catheter inside the mold, so that the area of higher temperature causes the material of the catheter to soften and flow until the material makes contact with the lower temperature zone, whereupon the material of the catheter stops flowing. catheter.

11. The method according to claim 10, further characterized in that the mold is heated by contacting an outer surface of the mold with a heating block, at a temperature higher than that of the mold, to transfer heat to the mold.

12. The process according to claim 10, further characterized in that the mold is made of a first material in the area of higher temperature and a second material that has a lower thermal conductance in the area of lower temperature.

13. - The method according to claim 10, further characterized in that the mold is made of a first material in the area of higher temperature and a second material that has lower specific heat in the area of lower temperature.

14. The method according to claim 11, further characterized in that the mold is formed to provide heat transfer years from the heating block to the area of lower temperature than the transfer of heat to the zone of higher temperature.

15. The method according to claim 11, further characterized in that the mold is formed to cool the zone of lower temperature faster than the area of higher temperature.

16. The method according to claim 11, further characterized in that the mold makes contact with the heating block along the zone of higher temperature and does not contact the heating block along the zone of lower temperature, during heating.

17. The method according to claim 10, further characterized in that the catheter is subsequently removed from the mold.

18. The method according to claim 10, further characterized in that the pin is removed from the mold and the catheter is then removed from the mold.

19. The method according to claim 10, further characterized in that there is an isolator provided in the mold, between the high temperature zone and the low temperature zone.

20. The method according to claim 10, further characterized in that cooling air is blown onto the mold to cool the mold and resolidify the catheter.

21. The method according to claim 20, further characterized in that the cooling air is focused, at least in part, on the portion of lower temperature.