LUBRICIOUS LINER IN CATHETER TUBE

A method for assembling a liner in a tube includes placing a liner in a tube, and heating a portion of the liner, called a heated portion, with a local heat source. The heated portion is not more than a third of a total length of the liner. The heated portion is expanded radially outwards so that the heated portion abuts against an inner wall of the tube. The local heat source is repeatedly advanced longitudinally along a desired length of the liner to expand the heated portion radially outwards so that the heated portion abuts against the inner wall of the tube for the desired length.

FIELD OF THE INVENTION

The present invention relates to lubricious liners used in catheter tubes for reducing friction and facilitating sliding an object in the tube, and particularly to expanding or joining the lubricious liner to the inner wall of the tube.

BACKGROUND OF THE INVENTION

There are many surgical or medical procedures, in which an object, such as a wire, a stent, a needle, a surgical tool, an embolic capture mesh, etc., must slide in or through a lumen of a catheter or tube (the terms being used interchangeably). It may be difficult to push the object through the lumen due to friction forces between the object and the inner wall of the catheter, especially if there are bends in the catheter when negotiating certain vasculature.

It is known in the art to reduce the friction by inserting into the catheter a liner made of a lubricious material, for example, a fluorocarbon such as polytetrafluoroethylene (PTFE), to provide a low-friction surface to allow easier sliding of the object through the catheter.

However, due to the non-stick properties of the lubricious liner, it is challenging to join the lubricious liner to the inner wall of the catheter. Therefore, prior art liners are either joined at one or more points of the tube while the rest of the liner is free and floating, or the liner is completely floating in the tube.

Because the liner is floating inside the tube (either partially or fully), and due to assembly constraints, the liner outer diameter (OD) is smaller than the tube inner diameter (ID). This results in a small contact area between the liner and the tube, and allows movement of the liner which can cause the liner to stretch.

SUMMARY

The present invention seeks to provide an innovative method for expanding a lubricious liner radially outwards to an inner wall of a catheter or tube, and as an additional option joining the liner to the tube, as is described more in detail hereinbelow.

In one non-limiting embodiment of the present invention, one portion of the liner is expanded against the inner wall of the tube without joining the tube to the liner, and another portion of the liner is expanded against the inner wall of the tube and joined to the tube. For example, it may be advantageous that the liner is not joined to the tube where there are slots or other cuts in the tube so the tube can bend in different directions, as opposed to an uncut portion of the tube where the liner is joined to the tube. Optionally, the liner can be joined to the cut portion of the tube, if desired.

Even where the liner is not joined to the tube, since the liner is expanded and pressed against the tube, the liner OD is the same as the tube ID, thereby creating a large contact area between the liner and the tube, which diminishes or eliminates stretching of the liner.

There is provided in accordance with a non-limiting embodiment of the invention, a method for assembling a liner in a tube including placing a liner in a tube, heating a portion of the liner, called a heated portion, with a local heat source, the heated portion being not more than a third of a total length of the liner, expanding the heated portion radially outwards so that the heated portion abuts against an inner wall of the tube, and repeatedly advancing the local heat source longitudinally along a desired length of the liner and expanding the heated portion radially outwards so that the heated portion abuts against the inner wall of the tube for the desired length.

In accordance with a non-limiting embodiment of the invention the liner is made of a lubricious material.

In accordance with a non-limiting embodiment of the invention the step of expanding is done by using a solid expander introduced into the liner.

In accordance with a non-limiting embodiment of the invention the step of expanding is done by using a liquid expander.

In accordance with a non-limiting embodiment of the invention the step of expanding is done by using a gas expander.

In accordance with a non-limiting embodiment of the invention a temperature to which the liner is heated is a temperature which softens the liner, but is lower than a melting point of the tube.

In accordance with a non-limiting embodiment of the invention a portion of the liner, called a non-joined expanded portion, is expanded against the inner wall of the tube without joining the tube to the liner.

In accordance with a non-limiting embodiment of the invention a portion of the liner, called a joined expanded portion, is expanded against the inner wall of the tube and the tube is joined to the liner.

In accordance with a non-limiting embodiment of the invention the tube is joined to the liner by heating the tube to a temperature above a melting point of the liner.

In accordance with a non-limiting embodiment of the invention the non-joined expanded portion is where there are slots or other cuts in the tube and the joined expanded portion is an uncut portion of the tube.

DETAILED DESCRIPTION

Reference is now made toFIG.1. It is desired to assemble a lubricious liner10in a tube12. Liner10may be made of a lubricious material, such as but not limited to, a fluorocarbon such as polytetrafluoroethylene (PTFE). Tube12may be made of a metal or polymer, such as but not limited to, stainless steel, nitinol, titanium alloy, nylon, polyether block amide (PEBA), and other materials. Examples of PEBA include the tradenames PEBAX (from Arkema) and VESTAMID (from Evonik Industries). Liner10initially has an OD smaller than the ID of tube12.

Tube12can be an outer layer of a tube assembly. In the context of the invention, it is the layer in which the liner is placed.

An expander14may be used to expand liner10radially outwards. The expander14may be made of a polymer, such as but not limited to, polyethylene terephthalate (PET), but could be made of other materials. Expander14has an OD slightly less than the ID of tube12, the difference between the diameters being the desired final thickness of liner10after its radial expansion.

Alternatively, expander14is not solid, but rather is a pressurized fluid (liquid or gas).

A local heat source16, such as an induction heating ring, resistance coil heating ring, hot air nozzle, torch or others, may be used to locally heat a portion of liner10, called a heated portion18. The heated portion18is significantly shorter in length than the total length of liner10(not more than a third of the total length), such as but not limited to, 5%, 10% or 20% of the total length. Defined in other terms, heated portion18may be a few millimeters in length, or 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 28 mm, 30 mm, 35 mm, 40 mm, or other suitable lengths.

As seen inFIG.1, liner10is initially placed in tube12. Local heat source16heats heated portion18and expander14is introduced in liner10. The local heat source16is gradually advanced longitudinally (in the direction of arrow20) and gradually heats a local area of liner10and tube12. In one option, expander14remains stationary inside the liner and the expander is made of a material that expands radially outwards upon reaching the heated temperature caused by the local heat source16. (For example, expander14could be made of a shape memory material.) The expander14thus causes lubricious liner10to expand radially outwards, and presses the heated portion18of expanded liner10against the inner wall of tube12. In another option, expander14does not expand outwards and is not stationary, but instead is gradually advanced longitudinally (in the direction of arrow20) and gradually expands the heated portion18of lubricious liner10radially outwards and presses the heated portion18of expanded liner10against the inner wall of tube12. In the expanded portion, the liner OD is the same as the tube ID.

The gradual heating and expansion is much more effective than heating a long length of the liner, because the gradual and expanded movement of the liner ensures there are no kinks, wrinkles or tears in the liner10.

The temperature to which the liner is heated by local heat source16is a temperature which softens the liner material to facilitate its expansion, but is lower than the melting point of the tube12. Without limitation, for one example with a PTFE liner and PEBA tube, the heated portion18is expanded with a pressure of 6 bar, and heated to 135° C. with a 28 mm wide heating nozzle, which linearly advances in the direction of arrow20at a speed of 1 mm/sec.

Reference is now made toFIGS.2A,2B,2C, and2D. One portion of the liner10, called non-joined expanded portion22, is expanded against the inner wall of the tube12without joining the tube12to the liner10. Another portion of the liner10, called joined expanded portion24, is expanded against the inner wall of the tube12and the tube12is joined to the liner10. The joining may be done at any temperature above the melting point of tube12. Without limitation, for one example with a PTFE liner and PEBA tube, the heated portion18is expanded with a pressure of 6 bar, and heated to 160° C. with a 28 mm wide heating nozzle, which linearly advances in the direction of arrow20at a speed of 1 mm/sec. The 160° C. temperature melts the tube material (in this example, the PEBA material), thereby welding (adhering) the tube material to the liner material. In another example, the PTFE liner may be an inner liner with an outer layer of PEBA, and the multi-layer liner is placed inside tube12which is made of another material, such as nitinol. In this case, the 160° C. temperature melts the outer layer of the liner material (PEBA), thereby welding (adhering) the outer layer of the liner material to the tube material.

In accordance with a non-limiting embodiment of the present invention, the non-joined expanded portion22is where there are slots or other cuts26in the tube12so the tube12can bend in different directions; this area undergoes high deformations due to different kinds and directions of bending, which may cause plastic deformation of the liner10which could weaken and break or tear the liner10. In contrast, the joined expanded portion24is an uncut portion of the tube12.