GB2400155A

GB2400155A - A braided tube and forming a funnel

Info

Publication number: GB2400155A
Application number: GB0314503A
Authority: GB
Inventors: Robert Snell; Samantha Martin; Martin Cable; Eleanore Morgan
Original assignee: Ranier Ltd
Current assignee: Ranier Ltd
Priority date: 2003-06-20
Filing date: 2003-06-20
Publication date: 2004-10-06
Also published as: GB0314503D0

Abstract

A radially expandable tube comprises a plurality of flexible filaments braided together. The tube is invaginated to form a funnel. The invention also provides a method of forming a funnel from a plurality of flexible filaments comprising the step of braiding the filaments together to form a radially expandable tube and invaginating the tube to form a funnel. The tube is used in a catheter.

Description

2400 1 55 - 1 A Braided Tube and Method of Forming a Funnel

Description

The present invention relates to a braided tube. More specifically, the invention relates to a braided tube formed from structural filaments and to a method of forming a funnel from such a tube. The invention also relates to a catheter incorporating the braided tube of the invention.

Tubes or pipes formed from braided material are known and are used in many applications. They generally comprise a plurality of threads or filaments that are intertwined, that is to say filaments which are splralled or helically wound in one direction cross over and under filaments which are spiralled or helically wound in the opposite direction.

Braided tubes of the aforementioned type have the advantage that they are flexible and kink resistant as well as having a relatively thin-wall in comparison with non- braided tubes having the same degree of kink resistance and flexibility.

In view of the known properties of braided tubes, they often find particular use in the construction of devices for medical applications. In particular, braided tubes are used in the manufacture of catheters where kink resistance and stiffness must be precisely controlled to facilitate the passage of the catheter through potentially tortuous paths in the body of a patient to reach a treatment site or destination, such as the urinary bladder. The use of a thin-walled tube is particularly advantageous in such applications so that the overall diameter of the tube can be kept to a minimum to reduce discomfort to the patient during or after insertion and to maximise the size of the lumen for rapid drainage of fluids from the body without forming blockages.

To date, conventional braided tubes have been used where kink resistance and flexlbiLty are important factors. However, the Applicant has found that a braided tube, or part of a braided tube, may be formed into a funnel shape that can be used, - 2 for example, in a catheter to retain it in position in a patient or to facilitate the flow of fluids into the tube.

According to the present invention, there is provided a radially expandable tube s formed from a plurality of flexible filaments braided together, wherein the tube is nvaginated to form a funnel.

The term "invaginated" is used in the sense that the tube is drawn back into itself so that It becomes unsheathed. Similarly, it can also taken to mean that the end of the tube can be folded back over itself so that the folded part ensheaths the remaining part of the tube. It will be appreciated that the end of the tube remains open once invag1nated. Because the tube is made from radially expandable material, the point at which the diameter of the tube IS at a maximum when radially expanded forms the mouth of the funnel and remains at this maximum diameter when the funnel is formed. The part of the tube extending away from the mouth of the funnel necks down gradually until it becomes the same diameter as the tube in its relaxed state.

Hence, when a radially expandable tube formed from flexible filaments braided together is invaginated, a funnel shape is formed at the new end of the tube.

In a preferred embodiment, the filaments are braided together at a predetermined braid angle relative to the longitudinal axis of the tube.

In an alternative embodiment, the filaments are braided together at a predetermined braid angle that changes along the length of the tube. Depending on how the braid 2s angle is varied, the shape of the resulting funnel can be controlled.

The present invention also provides a method of forming a funnel from a plurality of flexible filaments comprising the step of braiding the filaments together to form a radially expandable tube and invag1nat1ng the tube to form a funnel.

In a preferred embodiment, the method includes the step of braiding the filaments together at a predetermined braid angle relative to the longitudinal axis of the tube.

The braid angle may also be varied along the length of the tube. Depending on how the braid angle is varied, a funnel having a particular shape may be produced.

In accordance with another aspect of the invention, there is provided a funnel formed from a radially expandable tube according to the invention. Preferably, the funnel is made in accordance with the method of the invention.

The present invention also provides a catheter incorporating a radially expandable tube according to the invention.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 illustrates a side view of a braided tube according to the present Invention; FIGURE 2 illustrates a side view of the braided tube shown In Figure 1 after it has been radially expanded; FIGURE 3 Illustrates a longitudinal cross-sectional view of the braided tube shown in Figure 1, after it has been invaginated to form a funnel at one end thereof; FIGURE 4 is a simplified diagram of the braided tube of Figure 1 to demonstrate the relationship between braid angle and the maximum diameter of the tube or funnel, and FIGURE 5 is a table showing the relationship between braid angle and the maximum diameter of the tube or funnel.

Referrmg now to the drawings, there is shown in Figure 1, a side view of a tube 1 formed from filaments 2 which are loosely braided together so that they can all move relative to each other and allow the tube to expand radially from a diameter dl m a relaxed state to a maximum diameter d2 when an axial compressive force is applied In the direction of arrow "A". Figure 2 shows the tube of Figure 1 in which a portion 3 of the tube 1 has reached its maximum diameter d2 following compression. It will be appreciated that when the compressive force is removed or released, the tube returns to its original relaxed state in which the diameter of the tube Is equal to dl. The tube has ends 4,5.

As can be seen from Figure 3, the tube 1 of Figures land 2 has been mvaginated meamug that the end 5 of the tube 1 has been inverted or rolled inward of itself so that it has become ensheathed by the remainder of the tube. The exact same s configuration IS achieved by inverting or rolling the end 5 outward over itself so that the tube becomes partially unsheathed. When the tube 1 is released in this condition, the funnellike shape so formed is maintained and the tube 1 does not return to its relaxed state shown in Figure 1. The funnel has a mouth portion 6 which IS the point at which the diameter of the funnel is at its maximum value. This 0 diameter is the same as the maximum diameter of the tube 1 when the tube 1 is radially expanded and is equal to d2, as shown in Figure 2.

The maximum diameter of the tube 1, and therefore the maximum diameter of the funnel formed from the tube 1, is related to its braid angle. The braid angle is the angle of the braided filaments relative to the longitudinal axis of the tube. The braid angle is shown in the unexpanded tube of Figure 4 (only one braid filament is shown for the purposes of clarity). The braid angle is represented by "a", the angled length of the braid across the diameter of the tube 1 is designated by "y" and the diameter of the tube before any radial expansion is designated by "x".

If it is assumed that length "y" is the theoretical maximum diameter that the tube can have when expanded, and that the initial diameter "x" of the tube in its relaxed state is equal to 1, then it is possible to calculate the braid angle that IS required in order to provide a funnel having a required maximum diameter using Pythagoras's Theorem which states that: Sin a = x/y Assuming that the diameter of the tube in its relaxed state is equal to 1, then: Sin a = 1/y, and so the maximum diameter of the funnel is given by: y = 1/Sln a. - 5

It is therefore apparent that the braid angle and the maximum diameter of the tube or funnel have an inverse sinusoidal relationship.

s Figure 5 is a table to demonstrate the relationship between selected braid angles and the maximum diameter of the tube, which is equal to the maximum diameter of the funnel. At a braid angle of 15 degrees, the diameter of the expanded tube or the maximum diameter of the funnel is 3. 864 times the diameter of the tube before expansion. Similarly, at a braid angle of 30 degrees, the diameter of the expanded 0 tube or the maximum diameter of the funnel is twice the diameter of the tube before expansion. When the braid angle IS 60 degrees, the maximum diameter of the tube when expanded or the maximum diameter of the funnel is 1.154 times the c diameter before expansion.

By relying on the relationship between the braid angle and the maximum diameter of the funnel, it is possible to select a braid angle to provide a tube having a known maximum diameter and, consequently, a funnel having a maximum diameter.

It will also be appreciated that by making a tube with a non-uniform braid angle along its length, the shape of the funnel can be altered so that shapes other than just conically shaped funnels can be formed.

A particular application of the invention is in the manufacture of catheters for medical use. For example, a catheter may be provided with a retention section for retaining the catheter in position in the body of the patient once it has been inserted. The retention section may be formed from the braided tube of the invention which is maintained in the form in which it is illustrated in Figure 1 during insertion and removal of the catheter and, may be manipulated so that it assumes the funnel shaped configuration shown in Figure 3, once inserted. The funnel shape assists in retaining the catheter in position in, for example, the urinary bladder of the patient and also directs bodily fluids such as urine, in the case of a urmary catheter, into the catheter itself. The present invention realises that the shape of the funnel can be altered by changing the braid angle of the retention - 6 sectlon. The surgeon or other responsible member of the medical staff can then pick an appropriate catheter to suit the patient or bodily cavity in which the funnel is to be located. By selecting an appropriate funnel shape depending On the patient or specific use of the catheter, it will be more comfortable and less painful for the patient.

Many modifications and variations of the invention falling within the terms of the appended claims will be apparent to those skilled in the art and the foregoing description should be regarded as a description of a preferred embodiment only. - 7

Claims

Claims 1. A radially expandable tube comprising a plurality of flexible

filaments braided together, wherein the tube is invaginated to form a funnel. s
2. A radially expandable tube according to claim 1, wherein the filaments are braided together at a predetermined braid angle relative to the longitudinal axis of the tube.
3. A radially expandable tube according to claim 2, wherein the filaments are braided together at a predetermined braid angle that changes along the length of the tube.
4. A radially expandable tube according to claim 2 or claim 3, wherein the maximum diameter of the radially expanded tube is substantially equal to the maximum diameter of the funnel.
5. A radially expandable tube according to any of claims 2 to 4, wherein the braid angle and the diameter of the funnel have an inverse sinusoidal relationship. 2G o
6. A method of forming a funnel from a plurality of flexible filaments Comprlslng the step of braiding the filaments together to form a radially expandable tube and invaginating the tube to form a funnel.

2s
7. A method of forming a funnel according to claim 6, mcludmg the step of braiding the filaments together at a predetermined braid angle relative to the longltudmal axis of the tube.
8. A method of forming a funnel according to claims 6 or 7, including the step of braiding the filaments together at a braid angle that changes along the length of the tube. - 8
9. A funnel formed from a radially expandable tube according to any of claims 1 to5.
10. A funnel according to claim 9, made in accordance with the method of any s of claims 6 to 8.
11. An invaginated tube formed from a plurality of flexible filaments braided together, wherein the maximum diameter of said invagmated tube is determined by the braid angle.
12. A catheter incorporating a radially expandable tube according to any of claims 1 to 6.
13. A catheter according to claim 12, wherein the radially expandable tube can be formed into a funnel using the method according to one of claims 6, 7 or 8.
14. A radially expandable tube substantially as hereinbefore described with reference to the accompanying drawings.
15. A method of forming a funnel substantially as hereinbefore described.
16. A catheter substantially as hereinbefore described.