Apparatus for making a catheter

Abstract

The present invention concerns a catheter for medical purposes, such as for insertion into a body opening for draining fluids, wherein the catheter comprises a flexible tube having a distal end region wherein the tube is provided with at least one draining opening, characterised in that the peripheral edge on the outside of the tube is provided with a curvature for creating a smooth transition between the exterior surface of the tube and the substantially radially oriented cut constituting the opening side and wherein said curvature is a rounded edge with a curvature radius between 0.2-0.6 mm. The invention further concerns a method of making such catheter and an apparatus for performing this method.

Description

The present invention relates to a method of making a catheter for medical purposes, such as for insertion into a body opening for draining fluids, wherein the catheter comprises a flexible tube having a distal end region wherein the tube is provided with at least one draining opening. The invention further relates to an apparatus for performing such method.

A catheter includes a flexible tube with a distal end, which may be open or closed. The catheter is inserted into a body opening for draining fluids. In particular, the catheter may be a urinary catheter for insertion into a urinary pathway for collecting the fluids in this pathway.

In the distal end region of the catheter, the tube is provided with a number of openings for colleting fluid and draining the body opening, in particular the urinary pathway. A catheter of such kind is known from e.g. U.S. Pat. No. 5,919,170. As shown in this U.S. patent, the openings are preferably elongated to achieve a good fluid collecting capacity. These openings are usually punched into the tube. Examples of such catheters are known from e.g. GB-A-2 230 702 and U.S. Pat. No. 3,995,518.

U.S. Pat. No. 2,972,779 discloses two methods of providing the wall of a tubing of thermoplastic material with elongated holes having a smoothed outer edge. According to one method, the elongated holes are punched out and subsequently the edge is smoothed out in an operation whereby a moving grinding element, such as a rotating grinding wheel, is contacted with the sharp edge of the hole. According to another method, the elongated holes and their smooth edges are provided by punching and moulding by means of a metallic die having a punching element.

US 2005/0192560 A1 describes a method of providing a urology catheter by means of injection moulding. The catheter is provided with a drain eye in the wall of the tubing forming the body of the catheter. The inner and outer edges of the drain eye are smoothed out by forming radii between the wall of the drain eye and the inner and outer wall, respectively, of the tubing.

US 2004/0193143 A1 describes the forming of openings in a catheter by a punching operation. The openings may be rounded by a temperature treatment.

U.S. Pat. No. 4,259,276 describes a method of forming circular holes in thin plastic material. The method is exemplified by the forming of lateral holes in a cannula for epidural anaesthesia. Firstly, a needle is forced along its length through the wall of a nylon tubing to form a pierced aperture in the wall. The needle is withdrawn from the aperture, and drive is applied to the needle to rotate the needle at high speed about its longitudinal axis. The needle is then inserted into the pierced aperture without any drive being applied to the needle, so that contact of the rotating needle with the rim of the aperture produces frictional heating that serves to cause plastic flow smoothing out the contour of the pierced aperture .around the needle.

GB 2 230 702 A describes injection moulding of a catheter having elongated holes with rounded ends.

The catheter must be carefully inserted and removed to avoid damaging the tissue of the pathway. This can be a problem with these known catheters, since the openings have a relatively sharp edge which can damage the soft tissue of the pathway when the catheter is moved longitudinally or rotated in the pathway during inserted or retracted. The catheters are usually produced in PVC or PUR so that a soft flexible tube is provided thereby reducing the risk of tissue damage. However, practical experience with the catheters have revealed that in particular tissue of a urinary pathway may nevertheless be damaged if the catheter is not carefully inserted or retracted from the pathway.

This problem is addressed by a method of making a catheter according to the present invention, wherein the catheter comprises a flexible tube having a distal end region wherein the tube is provided with at least one draining opening, wherein the peripheral edge on the outside of the tube is provided with a curvature for creating a smooth transition between the exterior surface of the tube and the substantially radially oriented cut constituting the opening side and wherein said curvature is a rounded edge with a curvature radius between 0.2-0.6 mm. By the invention, the opening in the tube is provided with a three-dimensional contour in a curved plane congruent with the curvature of the opening in the cylindrical surface of the tube. Hereby, a smooth catheter is provided where the risk of tissue damage is reduced.

The opening is preferably elongated with a longitudinal length substantially corresponding to the diameter of the tube. The catheter tube may be provided with different diameters so that different sizes of catheters may be provided. The drainage openings in the catheter tube are preferably provided with an angle between the opening side wall and the internal surface of the tube is within the range of 64-90°. This provides the catheter with good drainage properties as well as tissue preserving properties.

The catheter tube is made of a medical grade polymer preferably having a Shore A value in the range of approx. 64 to approx. 100, in particular the polymer may be a thermoplastic material, such as a polyester-type thermoplastic polyurethane (TPU) compound having a Shore A value of approx. 94±3, polyvinyichloride (PVC), preferably having a Shore A hardness ranging from 78 to 85, or polyurethane (PUR). By the invention, it is realised that a variety of materials are suitable for the catheter. For instance, the catheter tube may be of polyvinylchioride (PVC) with a hardness measured in Shore A with a value of 64 to 86, preferably 80 to 85 Shore A.

By the invention, there is also provided a method of making a catheter comprising a polymer tube with openings therein, said method for providing openings in a polymer tube of such catheter comprising the steps of:

providing a tube and punching at least one opening in the tube by advancing a cutting member in a substantially radial direction into the wall of the tube;

manipulating the outer peripheral edge region of the at least one opening by rounding the peripheral edge of the punched opening in the tube by advancing a heated forming member into the opening and thereby providing the edges of the opening with a shape corresponding to the shape of the distal end of the forming member, said forming member having a distal end adapted for engagement with an opening of the tube provided adjacent said distal end, wherein said distal end of the forming member is provided with a rounded shoulder transition at the foot of the distal end and with a protrusion extending from said shoulder transition region, said protrusion having a form fitting the opening in the tube, said rounded shoulder being formed with a contour in a curved plane congruent with the curvature of the opening in the cylindrical surface of the tube.

By finishing the opening in a separate after treatment process, the smooth curvature of the edge of the drainage opening is ensured.

In a preferred embodiment of the method, the loose cut-away material after the punching action is removed from the tube. Hereby, it is ensured that residues from the making of the opening do not drop into the inside of the catheter tube.

According to the invention there is also provided an apparatus for manipulating openings in a polymer tube for manufacturing a catheter, said apparatus comprising a movable frame comprising one or more forming stations, each forming station being adapted for receiving a flexible polymer tube with at least one opening, therein through the station and each forming station comprising a forming member, which is mounted in floating arrangement in said forming station, said forming member having a distal end adapted for engagement with an opening of the tube provided adjacent said distal end, wherein said distal end of the forming member is provided with a rounded shoulder transition at the foot of the distal end and with a protrusion extending from said shoulder transition region, said protrusion having a form fitting the opening in the tube, said rounded shoulder being formed with a three-dimensional contour congruent with the curvature of the opening in the cylindrical surface of the tube, and heating means for said forming member, so that said forming member may be heated to a temperature above the softening point of the polymer of the tube and preferably below the melting point of the polymer material of the tube.

In order to ensure a smooth result of the plastic deformation of the edge region of the opening in the tube, the distal end of the forming member is provided with a rounded shoulder transition at the foot of the distal end and with a protrusion extending from said shoulder transition region, said protrusion having a form fitting the opening in the tube, said rounded shoulder being formed with a three-dimensional contour congruent with the curvature of the opening in the cylindrical surface of the tube.

The rounded shoulder region is provided with a curvature radius between 0.2-0.6 mm and preferably the protrusion is elongated with a longitudinal length substantially corresponding to the axial extension of the opening on the tube.

In the preferred embodiment, the forming member is provided in a forming station which is arranged in a movable frame, and each forming station is adapted for receiving a flexible polymer tube through the station, and whereby the forming member is mounted in floating arrangement in a forming station, whereby the forming member is self-aligning when the protrusion is engaging the opening of the tube. This floating arrangement allows for inaccuracies in the positioning of the opening relative to the forming member.

The movable frame preferably comprises an upper section and a lower section where between the at least one forming station is arranged and the upper section is heated to a first temperature, such as 190°-200° C., and the lower section is heated to a second temperature, such as 170°-180° C., which is lower than the first temperature. The holding time of the forming member in contact with the tube is preferably 1 to 5 seconds, more preferably between 1.5 and 2.0 sec. Since there inherently is a heat loss between the movable frame and the shoulder and tip of the forming member, the temperatures applied to the upper and lower sections are somewhat higher than the. preferred temperature which is between the softening point of the polymer of the tube and below the melting point of the polymer material of the tube. This ensures that the deformation of the edge does not result in any deterioration of the surface texture and the material of the tube, e.g. burns or uncontrolled deformations. The forming member is made of metal, such as brass or similar heat resistant material that can withstand the applied heat. By the invention it is realised that the temperature may be even above the melting point of the tube material if the holding time is kept very low, such as below 1.5 seconds.

It is realised that the predetermined temperatures and the holding times are selected in accordance with the specific plastic material used for the tube.

In the following the invention is described with reference to some preferred embodiments shown in the accompanying drawings, in which:

FIG. 1 is a side view of a catheter of the kind the present invention concerns;

FIG. 2 is a detailed view of an axial cross-section of the tip of a catheter according to the invention;

FIG. 3 is a detailed view of a radial cross-section of the tip of a catheter according to the invention through the section B-B in FIG. 2;

FIG. 4a)-e) are further views of a catheter according to the invention;

FIG. 5 is a perspective view of the catheter of FIG. 4;

FIG. 6 is a detailed perspective view of the opening after punching but before the rounding process according to the invention,

FIG. 7 is the same as FIG. 6, but after the method of the invention is performed;

FIGS. 8-10 are three side views of a forming member in an apparatus for making the catheters according to a preferred embodiment of the invention;

FIG. 11 is a side view of a forming member of a smaller size than the forming member shown in FIG. 9;

FIG. 12 is a schematic end view along the catheter tube with two oppositely situated forming members in engagement in the draining openings;

FIG. 13 is a section view along A-A in FIG. 12;

FIG. 14 is a schematic side view of the catheter tube with two oppositely situated forming members in engagement in the draining openings;

FIG. 15 is a section view along B-B in FIG. 14;

FIG. 16 is a section view along C-C in FIGS. 14; and

FIG. 17 is a schematic front view of a forming station in a moveable frame in an apparatus according to the invention;

FIG. 18 is a cross-sectional front view of the forming station in FIG. 17;

FIG. 19 is a cross-sectional side view of the forming station in FIG. 17; and

FIG. 20 is a detailed perspective view of the geometry of the distal end of the forming member and the opening in the tube.

With reference to FIGS. 1 to 5, a catheter according to the invention comprises a flexible tube 1, which is made of a plastic material, preferably polyvinylchloride (PVC) or polyurethane (PUR) and attached to a connector 2. The tube 1 is provided with a number of openings 3 in region of the distal end 4 of the tube 1. This opening 3 serves a drain for collecting fluids outside the tube to flow inside the catheter tube 1 for draining the body space in which the catheter is inserted. The opening 3 has a generally radially oriented side wall 5 (see FIG. 3), and which may be provided with an angular orientation v of between 60-90′ relative to the inner surface of the wall of the tube 1 (see FIG. 2). The opening .3 may involve a slight indentation 6 into the tube inner space. This indentation 6 may be between 0-0.5 mm. The hole 3 is provided with rounded external edges 7, so that a smooth transition between the opening walls 3 and the surface of the tube 1 is ensured.

The openings 3 are punched in the tube using a punching tool (not shown) or other cutting tool. After the opening 3 is cut in the cutting process, the loose tube wall section is removed leaving an opening in the tube 1 where the opening 3 has a sharp outer edge, as shown in FIG. 6. By the finishing process according to the invention, the outer edge is rounded as shown in FIG. 5 and FIG. 7.

For providing the rounded edge 7 on the opening 3, a moveable frame 20 is used; see FIGS. 17 to 19. The moveable frame includes one or more forming stations, where each forming station is adapted for receiving a flexible polymer tube 1 through the station adjacent a forming member 10. The forming station further includes a holding member 11 to which the forming member 10 is fixed. This member is connected to an upper section 21 of the frame 20 by a spring arrangement 26. The holding member 11 is furthermore pivotably connected to the distal ends of a fork-like member 12, so that the fork-like member 12 and the holding member 11 may pivot relative to each other about an axis A substantially perpendicular to the tube 1 above the tube 1. The fork-like member 12 is at its base pivotably connected to a third member 13, where the two members 12, 13 may pivot about an axis B substantially parallel to the tube 1 below the tube 1. This third member 13 is then pivotably connected to a lower member 14 allowing these members 13, 14 to pivot about an axis C substantially perpendicular to the tube 1. This lower member 14 is preferably vertically slidably secured to a lower section 22 of the frame via a spring 25. When the frame 20 is moved relative to the tube 1, the forming member 10 is moved in engagement with the opening 3 in the tube 1. By the pivoting arrangements, the forming member 10 is floatingly arranged in the frame whereby the forming member 10 may be self-centering in the opening 3.

With reference to the FIGS. 8-10 and 11, the forming member 10 has a distal end 33 adapted for engagement with the opening 3 of the tube 1 provided adjacent the distal end 33. The distal end 33 of the forming member 10 is provided with a rounded shoulder transition 32 at the foot of the distal end 33 and with a protrusion 31 extending from the shoulder transition region 32. The protrusion 31 has a form fitting the opening 3 in the tube 1. The rounded shoulder 32 is formed with a three-dimensional contour congruent with the curvature of the opening 3 in the cylindrical surface of the tube 1. It is important to realise that the edge 7 of the opening on the tube 1 extend in a curved plane, i.e. the edge 7 has a three-dimensional extension. As shown in FIGS. 9 and 11, the forming member 10 may be provided with different distal ends in order to adapt a forming member to a specific tube and opening size.

By applying heat to the frame and thereby to the members in the forming station, which are all made of a thermally conductive material, preferably steel or similar metal, the forming member 10, which is made of brass or the like, is heated to a temperature above the softening point of the polymer of the tube and preferably below the melting point of the polymer material of the tube. A first heat source 23 is applying heat to the upper section 21 of the frame 20 and a second heat source 24 is applying heat to the lower section 22 of the frame 20. The first temperature may preferably be between 180-200° C.±10° C. and the second temperature may be between 170-190° C.±10° C. The diameter of the tube may be between 2.0-6.0 mm-and the temperature applied is preferably in the lower range of the temperature range if the diameter is small. The temperature ranges as well as the holding times may vary depending on the type of material and the thickness of the tube wall as well as the diameter of the tube.

When heat is applied to the forming station and thereby to the forming member 10 the forming member 10 is advanced into engagement with the opening 3 in the tube 1 for a predetermined period of time, preferably between 1.5-2.0 seconds. The temperatures applied and the times of engagement, i.e. the holding time, are selected in accordance with the tube material and the tube dimensions. The temperature may be even above the melting point of the tube material if the holding time is kept very low. Hereby, the edge 7 is rounded in a plastic deformation process as the heated forming member 10 is moved into engagement in the opening 3. The protrusion 31 fits into the opening 3 and as the protrusion aligns in the opening 3, the rounded transition 32 thereby advances correctly towards the edge region and thereby creates the desired rounding of the edge 7. The floating arrangement described earlier facilitates the alignment of the forming member 10 in the opening.

As shown in FIGS. 12 to 16, two openings in a catheter made can be processed simultaneously by having two movable frames (not shown) adjacent each other so that a first forming member 10′ is advanced into contact with an opening from a first side of the tube and a second forming member 10″ is advanced into contact from a side opposite the first side.

The form of the edge 7 of the opening 3 in the tube 1 is determined by the geometry of the distal end of the forming member 10, in particular the shoulder transition 32 but also the protrusion 31. The resulting tube opening 3 may be provided with an inclined side surface 5 with an angle v between 60°-90° in the axial direction between the opening side and the inner surface of the tube 1, see FIG. 2. As shown in FIG. 3, the side walls 5 of the opening 3 may have a radial direction in the cross-sectional direction. Moreover, a slight inwardly extending indentation 6 having a radial extension between 0-0.48 mm is also provided in the tube.

EXAMPLES

For different diameter sizes, tests have been made for finding a suitable relationship between temperature, holding time and pressure of the forming member 10. In practice, the pressure may be predetermined as the insertion depth of the distal end of the forming member 10 and may be controlled in relation to the predetermined measurements and tolerances. By testing, the chosen combinations of temperature and time listed in table 1 below are found stabile for manufacturing and optimal with respect to minimizing the process time.

The parameters for the tests were:

The tube material was ESTANE 58212 TPU which is a thermoplastic polyurethane compound with a glass transition temperature of −25° C., an extrusion temperature of 200-210° C. and an injection moulding temperature of 195-205° C.

• • The shape and the temperature of the distal end of the forming member.
  • The time the forming member is making contact with the tube.
  • The insertion depth of the distal end of the forming member in the tube, referred to as pressure).

TABLE 1
ESTANE ® 58212 TPU
	Diameter
	size	Temp.	Time
	CH08	170° C.	1.5 s
	CH10	180° C.	1.7 s
	CH12	180° C.	1.7 s
	CH14	180° C.	1.7 s
	CH16	180° C.	1.7 s
	CH18	180° C.	2.0 s

Compared to the parameters in table 1, by lower temperatures or shorter time or lower pressure (i.e. shorter insert distance) it was found that the rounding was not complete and/or the deformation was not permanent.

Compared to the parameters in table 1, by larger temperatures, the material became too liquidized and melted and by longer time or larger pressure resulted in elevated edges in the transition between the tube and the forming member 10.

In relation to the geometric shape of the distal end of the forming member 10 it was found of imperative importance that the rounding of the edge is a stamp of the forming member by a certain deformation of the tube. Accordingly, the shape of the distal end of the forming member is of most importance for obtaining a satisfactory rounding of the edge of the catheter opening 3. By matching the three-dimensional contour of the edge on the tube when shaping the distal end of the forming member, i.e. with the same dimensions, rounding and sizes, a satisfactory result was considered achieved. Moreover, by forming the distal end of the forming member with appropriate angles and transitions it was found further ensured that no “sharp” edges would occur on the tube.

As indicated in FIG. 20, the contour of the shoulder transition portion 32 of the distal end 33 of the forming member 10 are shaped with two end sections 34 with a “straight” section 35 there between. The corresponding edge contours are marked on the tube opening 3 by 34′ and 35′, respectively. Whereas the straight section 35 is substantially in the same plane, due to the cylindrical shape of the tube and the central straight shape of the opening when viewed from the Y-axis, the ends 34, 34′ are curved out of this plane because of the rounded, semi-circular end portions of the opening again when viewed from the Y-axis. This three-dimensional shape of the distal end of the forming member 10 is found particularly advantageous in order to achieve an opening 3 with an entirely and truly smooth contour.

This geometry ensures that an unacceptable deformation on the inside of the tube is prevented.

The resulting rounded edge along the opening in the catheter tube is in an X-Y and/or Y-Z plane. When viewing the catheter in the Z-direction, such as shown in FIG. 2, FIGS. 46 and 4e, it becomes apparent that the contour of the edge of the opening 3 is curved in an X-Y plane perpendicular to the rounded edge plane at any given place on along the opening. This curvature of the side contour of the opening is due to the cylindrical form of the tube. This in turn means that when the opening is cut the central section, i.e. the straight section 35′ in FIG. 20, becomes lower that the outer contour of the tube view viewed from the side, e.g. as schematically shown in FIGS. 4a, 4c and 4e. The end sections of the opening, i.e. the extremes in the X direction of the opening, curve outwards towards the straight outer contour of the tube itself. By the invention it is realised that it is important to acknowledge and pay attention to this geometric shape when forming the rounded edges on the opening in order to avoid sharp edges and to ensure a truly smooth transition between the outer surface of the cylindrical tube and the inner side wall 5 of the opening 3.

Above, the invention and the different aspects thereof are described with reference to some preferred embodiment. However, by the invention it is realised that other variations and equivalent solutions may be provided without departing from the scope of the invention as defined in the accompanying claims, such as other suitable materials and other process parameters, such as temperature and time, may be chosen in order to achieve a satisfactory result when using tubes in a predetermined material.

The catheter according to the invention may be a urinary catheter, a tracheostomy catheter or any other type of catheters for insertion into a body cavity for draining fluids.

Claims

1. A method of making a catheter comprising a polymer tube with openings therein, said method comprising: providing a tube and punching at least one opening in the tube by advancing a cutting member in a substantially radial direction into the wall of the tube and providing the at least one opening with a three-dimensional edge contour, whereby central, straight sections of the edge contour of the opening become lower than the outer contour of the tube when the tube is viewed from the side, and end sections of the edge contour of the opening curve outwards towards the straight outer contour of the tube itself;manipulating an outer peripheral edge region of the at least one opening by rounding the peripheral edge of the punched opening in the tube by advancing a heated forming member a predetermined distance into the opening and providing the peripheral edges of the opening with a shape corresponding to a shape of a distal end of the forming member, said distal end of the forming member is provided with a rounded shoulder transition portion at a foot of the distal end and with a protrusion extending from said shoulder transition region, said protrusion having a form fitting the opening in the tube, said distal end of the forming member being shaped so that it matches the three-dimensional contour of the edge of the punched opening in the tube, a contour of the shoulder transition portion of the distal end of the forming member is shaped with two end sections with substantially straight sections therebetween, corresponding to the end sections and the central straight sections of the edge contour of the opening, respectively, the substantially straight sections of the contour of the shoulder transition portion extend substantially in the same plane, the end sections of the contour of the shoulder transition portion curve out of said plane;holding said heated forming member in said advanced position for a predetermined holding time; andretracting the forming member.

2. A method according to claim 1, further comprising removing loose cut-away material after the punching action.

3. A method according to claim 1, further comprising providing the forming member in a forming station positioned in a movable frame, the forming member is mounted in floating arrangement in the forming station, the forming member is self-aligning when the protrusion is engaging the opening of the tube received in the forming station.

4. A method according to, claim 1, comprising heating an upper section of the movable frame to a first temperature and heating a lower-section of the movable frame to a second temperature with the forming station between the upper section and the lower section, wherein the second temperature is lower than the first temperature.

5. A method according to claim 1, comprising providing the distal end of the forming member with a rounded shoulder transition with a curvature radius between about 0.2-0.6 mm at the foot of the distal end and with a protrusion extending from said shoulder transition region which is inserted into the opening of the tube, and providing the protrusion is provided with a form fitting the opening in the tube, and forming the rounded shoulder with a three-dimensional contour congruent with the curvature of the opening in the cylindrical surface of the tube.

6. A method according to claim 1, comprising providing the tube made of a medical grade polymer having a Shore A value in the range of about 64 to about 100, and heating the forming member to a temperature above the softening point of the polymer of the tube and below the melting point of said polymer.

7. A method according to claim 1 wherein the predetermined holding time is about 1 to 5 seconds.