Patent Description:
A method of welding a sleeve to a tube is known, with the single or multi-lumen tube made of relatively flexible but inextensible material, for example polymeric material such as polyamide, polyether block amide, polycarbonate, or the like, and with the sleeve of consistently elastic material, for example polymeric material such as polyisoprene or polyurethane, assigned to be inflated to make a balloon. The materials of the sleeve and the tube do not allow mutual fusion.

This known method essentially involves the steps of:.

The main disadvantage of the known method consists in the fact that the mechanical constraint by gluing or tying the sleeve to the pipe does not guarantee the tightness of the constraint itself in correspondence with stresses of particular extent.

Another disadvantage of the known method consists in the fact that the mechanical constraint involves a thickening and a discontinuity in the overall diameter of the ends of the sleeve.

A method of welding a sleeve to a tube is also known, with the tube and the sleeve made of materials suitable for mutual welding by fusion.

This latter known method essentially involves the steps of:.

In the common use of the tube with inflatable sleeve obtained by means of this known method, it is usually necessary that the tube has an almost constant cross-section as the pressure and the curvature vary, is made of a sufficiently flexible but inextensible material, and that the sleeve is made of a suitably elastic material so that it can be inflated; a disadvantage of this method lies in the fact that, requiring the use of mutually weldable materials, it restricts the choice to materials which may be unsuitable for making the tube or the sleeve.

Document <CIT> discloses a medical device formed at least in part from a microfibrillar polymer-polymer composite, the microfibrillar polymer-polymer composite comprising a polymer matrix and oriented polymer microfibrils, and method of making the same.

Document <CIT> discloses a length of trilayer, extruded, medical tubing comprising an outer layer, a core layer, and an intermediate tie layer. The outer layer comprises a polymer that is directly bondable, while the core layer comprises a lubricious polymer.

Document <CIT> discloses a catheter comprising a first component and a second component. The first component has a first outer diameter and the second component has a second outer diameter. When a portion of the first component is bonded to a portion of the second component, the first outer diameter is substantially equal to the second outer diameter. A heat shrink material is employed to bond said portion of the first component to said portion of the second component.

The main object of the present invention is to propose a method of welding a sleeve to a tube by fusing the sleeve to the tube, where the sleeve and the tube are made of respective materials that do not allow mutual fusion and welding, for example polymeric materials such as polyisoprene and/or polyurethane for the sleeve and polyamide and/or polyether block amide and/or polycarbonate for the tube.

Another object is to propose a method of welding a sleeve to a tube in which the mechanical and pneumatic tightness of the sleeve on the pipe is extremely effective.

The features of the invention are highlighted hereafter with specific reference to the accompanying schematic and non-scale drawings in which:.

With reference to <FIG>, the present invention relates to a method of welding a sleeve <NUM> to a tube <NUM>, to obtain a device <NUM> of <FIG> assigned to be used, for example, in the medical field as a catheter with inflatable balloon, in the hydraulic field as a probe, in any application where a tube or probe with an inflatable balloon is useful.

The tube <NUM> has at least one outer layer <NUM>, of a first material, which encloses a longitudinal lumen <NUM>, set in fluid communication with the outside of the tube <NUM> also through lateral openings <NUM>, preferably one, of slot or eyelet type. Optionally, the tube <NUM> can have one or more inner layers and/or more lumens, where at least one of the lumens <NUM> is in fluid communication with the outside of the tube <NUM> through said lateral opening or openings <NUM>.

The tube <NUM> can flex adequately in correspondence with a use condition U, for example during its insertion and use inside the body of a patient, bending but without throttling. The cross section of the tube <NUM> remains practically constant as the pressure inside the tube <NUM> and the curvature of the tube <NUM> vary.

The sleeve <NUM> has tubular shape, with two end portions <NUM> opposite and open at respective ends <NUM>. The length of the sleeve <NUM> is greater than the longitudinal dimension of the lateral opening <NUM> of the tube <NUM> to which the ends <NUM> of the sleeve <NUM> must be welded.

The sleeve <NUM> is mainly made of an elastic second material, suitable for inflation but not suitable for welding or fixing by fusion with the first material of the outer layer <NUM> of the tube <NUM>.

Preferably but not necessarily, the method provides to remove the heat-shrink elements <NUM> from the device <NUM>.

In correspondence with the use condition U, the device <NUM> can be inserted into the body of a patient from the side of an insertion end of the tube <NUM> itself; by pressure forcing a fluid F into the lumen <NUM> of the tube <NUM> in communication with the opening <NUM> from its opposite open end, the elastic sleeve <NUM> is assigned to inflate forming a balloon <NUM>, while the tube <NUM>, rigid to transverse deformation, does not change its own dimension.

The outer surface of the outer layer <NUM> of the tube <NUM> can be coated with the third material for example by extrusion, or by spraying, or by means of other processes commonly known to the skilled in the art, to make the outer coating <NUM>.

All the steps of the method can be indifferently carried out manually by an operator or automatically by a machine.

In the preferred embodiment, a polymeric material is for example used for the first material of the outer layer <NUM> of the tube <NUM>, comprising at least one of polyamide (PA), polyether block amide (PEBA), polycarbonate (PC) and/or the like; the second material of the sleeve <NUM> is for example chosen polymeric, comprising at least one of polyisoprene, polyurethane (PU) and/or the like; a polymeric material, for example, is used for the third material of the outer coating <NUM> of the tube <NUM>, comprising at least one of polyisoprene, polyurethane (PU) and/or the like.

In the exemplified case, the second material and the third material are mutually weldable by fusion, but they are not suitable for welding with the first material by fusion, as is commonly known to the expert in the field.

Preferably, the method provides in particular to completely coat the outer layer <NUM> of the tube <NUM> with the outer coating <NUM> of the third material.

The friction and/or interference between the external surface of the tube <NUM> and its outer coating <NUM> are generally sufficient in themselves to mutually anchor and seal the tube <NUM> and the external coating <NUM>.

The heat-shrink elements <NUM>, in an initial condition in correspondence with the step of applying them <NUM> onto the sleeve <NUM>, have an internal diameter equal to or slightly greater than the external diameter of the sleeve <NUM> fitted on the tube <NUM>.

In correspondence with the step of supplying the heat Q to weld the sleeve <NUM> to the tube <NUM>, each heat-shrink element <NUM> distributes this heat Q on its own internal surface, and therefore to the respective underlying end portion <NUM> of the sleeve <NUM>, protecting the latter from local temperature surges which could cause an irreparable degradation in its structural and/or chemical composition.

The temperature of the part of the end portion <NUM> of the sleeve <NUM> affected by the flow of the heat Q increases at least up to the melting temperature of the second material of the sleeve <NUM>; the further propagation of the heat Q through the thickness of the sleeve <NUM> also leads to the possible partial melting of the third material of the outer coating <NUM> of the tube <NUM> directly in contact with the molten part of the sleeve <NUM>; concurrently, the distribution of the heat Q along the heat-shrink element <NUM> causes a longitudinal and diametral shrinking of the latter, which presses on the end portion <NUM> of the sleeve <NUM>, now melted; thanks also to this compression action, therefore, the two molten materials interpenetrate and mix with each other, at least partially, in a welding region <NUM>, leading to the mutual welding of the sleeve <NUM> and the tube <NUM>.

After the welding of the two molten materials, the heat Q initially supplied to the heat-shrink element <NUM> spreads further from the welding region <NUM> to its neighborhood, causing a lowering of the temperature in the welding region <NUM> itself below the melting temperature.

Once the end portions <NUM> of the sleeve <NUM> and the adjacent tracts of the outer coating <NUM> of the tube <NUM> have cooled and are once again in the solid state, it is possible to carry out the step of removing the heat-shrink elements <NUM> from the device <NUM>. This removal can take place in various alternative ways, for example by pulling the heat-shrink elements <NUM> off the tube <NUM> from both its ends, or by longitudinally cutting the heat-shrinking elements <NUM> to sever their lateral surface and thus release them from the tube <NUM>, or by similarly breaking their lateral surface by pulling a tab or sturdy wire, not shown, associated inside the heat-shrink elements <NUM> prior to their application on the sleeve <NUM>.

Once the heat-shrink elements <NUM> have been removed, it is optionally possible to finish the welding regions <NUM> of the sleeve <NUM> to the tube <NUM>, for example by chamfering or tapering the ends <NUM> of the sleeve <NUM> by filing, turning or cutting, especially if these have not been affected by the melting and therefore protrude clearly from the surface profile of the coated tube <NUM>: this could indeed cause discomfort or injuries to the patient in correspondence with the use condition U of the device <NUM>.

The heat Q is preferably supplied to the heat-shrink elements <NUM> by conduction through contact with heating means and/or by convection through a flow of hot gas and/or by electromagnetic radiation.

The heating means are for example resistive elements.

The electromagnetic radiation originates, for example, from incandescent or halogen lamps, which radiate energy in the visible and/or infrared and/or ultraviolet spectra; alternatively and preferably laser sources are used so that the irradiation is more intense, in which case the energy namely the heat Q is supplied to the heat-shrink elements <NUM> in quantities that are well-defined and located with extreme precision. In particular, the use of a pulsed laser allows to concentrate a considerable amount of energy into pulses of reduced duration and extension; this energy propagates through the relatively thin heat-shrink elements <NUM> to the underlying sleeve <NUM> and tube <NUM>, causing the latter to melt and the heat-shrink elements <NUM> to shrink; however, the short duration of the pulse leaves no way for the heat Q to diffuse appreciably in the longitudinal direction, allowing the portions of tube <NUM> and sleeve <NUM> affected by fusion to be well localized.

Referring now to <FIG>, in order for the outer coating <NUM> to adhere more tightly to the outer layer <NUM>, before the coating step, a variant of the method optionally provides for applying on the tube <NUM> an intermediate layer <NUM> of a binding material to chemically bond the outer layer <NUM> and the outer coating <NUM> of the tube <NUM> and/or making them adhere to each other. After the coating step, this intermediate layer <NUM> is interposed between the outer layer <NUM> and the outer coating <NUM> of the tube <NUM>.

The binding material acts as a primer or adhesive between the second material and the third material, being able to chemically and/or mechanically bind to both and thus making them adhere to each other, and is for example a glue (epoxy, acrylic, cyanoacrylate, polyurethane, silicone, and/or similar) or preferably low density polyethylene (LDPE).

In another variant thereof, the method provides for arranging each heat-shrink element <NUM> in such a way that it covers, in addition to at least one already mentioned part of the respective end portion <NUM> of the sleeve <NUM>, also the respective end <NUM> of the sleeve <NUM> and at least an adjacent portion of the outer coating <NUM> of the tube <NUM> not covered by the sleeve <NUM>, for example each heat-shrink element <NUM> being approximately centered on the respective end <NUM> of the sleeve <NUM>. This arrangement is particularly convenient, because by supplying the heat Q to each heat-shrink element <NUM> almost at the respective end <NUM> of the sleeve <NUM> such heat Q propagates both to the end portion <NUM> of the sleeve <NUM> and to the underlying outer coating <NUM> of the tube <NUM> and directly to the outer coating <NUM> adjacent to the sleeve <NUM> but not covered by this. Therefore, part of the end portion <NUM> of the sleeve <NUM>, part of the outer coating <NUM> of the tube <NUM>, and in particular the end <NUM> of the sleeve <NUM> are involved in the fusion. The concurrent compressing action exerted by the heat-shrink element <NUM> thus also involves the discontinuity at the end <NUM> of the sleeve <NUM>, and following the mutual fusion between the sleeve <NUM> and the outer coating <NUM> of the tube <NUM> and the subsequent solidification, the end portions <NUM> of the sleeve <NUM> are welded in a single body to the tube <NUM> in respective welding regions <NUM>, which are tapered or rounded.

In order for the heat-shrink elements <NUM> not to be melted and not to be welded in turn with the sleeve <NUM> or with the outer coating <NUM> of the tube <NUM>, they are preferably made of a material not suitable for fusion with the materials of the sleeve <NUM> and of the outer coating <NUM>. Said material, for example, is a polymeric material that shrinks upon heating, but with a higher melting temperature than that of the materials to be melted; for this reason the preferred choice is polytetrafluoroethylene (PTFE), or for example polyethylene (PE), polyvinyl chloride (PVC), neoprene, and/or similar.

With reference also to <FIG>, the method also comprises the steps of:.

The protective element <NUM> is for example a tubular or planar shaped sheath, such that it can be fitted on or wrapped around the respective end portion <NUM> of the sleeve <NUM> interposing between this and the respective heat-shrink element <NUM>, and with a thin thickness, such as not to significantly alter the distribution of the heat Q from the heat-shrink element <NUM> to the sleeve <NUM> and to the tube <NUM> thereunder. Each protective element <NUM> covers at least a part of the respective end portion <NUM> of the sleeve <NUM> and an adjacent portion of the tube <NUM> not covered by the sleeve <NUM>.

The material of the protective element <NUM> is preferably polyamide or similar material, which cannot be welded by fusion with the materials of the heat-shrink element <NUM>, of the sleeve <NUM> and of the outer coating <NUM> of the tube <NUM>. The length of the protective element <NUM> can be equal, smaller or even greater than that of the respective heat-shrink element <NUM>, provided that, once the protective element <NUM> has been put on, it separates the heat-shrink element <NUM> from the sleeve <NUM> and from the tube <NUM> at least at the end <NUM> of the sleeve <NUM> and at the parts of the sleeve <NUM> and of the outer coating <NUM> assigned to be fused by the externally supplied heat Q.

The function of the protective element <NUM> is essentially to prevent the heat-shrink element <NUM> from welding to the tube <NUM> or to the sleeve <NUM> in correspondence with the supply step of the heat Q.

The protective elements <NUM> can be removed from the device <NUM> in various ways similar to those provided for the removal of the heat-shrink elements <NUM>.

The removal of the protective elements <NUM> preferably takes place after the step of removing the heat-shrink elements <NUM>, but alternatively it can also be carried out before this step, especially if the protective element <NUM> is longer than the respective heat-shrink element <NUM> and therefore protrudes outside of the latter, making it suitable for being grabbed and removed from under the heat-shrink element <NUM>.

Claim 1:
Method of welding a sleeve (<NUM>) to a tube (<NUM>), where the tube (<NUM>) has at least one outer layer (<NUM>) in a first material and at least one lumen (<NUM>) in fluid communication with the outside of the tube (<NUM>) through at least one lateral opening (<NUM>), and where the sleeve (<NUM>) has two end portions (<NUM>) opposite and open at respective ends (<NUM>) and is made of a second material not suitable for fusion with the first material of the outer layer (<NUM>) of the tube (<NUM>); the method comprising the steps of:
- covering at least a tract, including the lateral opening (<NUM>), of the outer layer (<NUM>) of the tube (<NUM>) with an outer coating (<NUM>) of a third material compatible with fusion with the second material of the sleeve (<NUM>);
- putting the sleeve (<NUM>) onto said coated tract of the tube (<NUM>) at the lateral opening (<NUM>);
- applying on at least one part of each end portion (<NUM>) of the sleeve (<NUM>) a respective heat-shrink element (<NUM>);
- supplying each heat-shrink element (<NUM>) with a quantity of heat (Q) which by heating it causes it to shrink and compress the respective end portion (<NUM>) of the sleeve (<NUM>) against the tube (<NUM>), where this quantity of heat (Q) is transmitted to the end portion (<NUM>) of the sleeve (<NUM>) bringing it to a temperature equal to or higher than its melting temperature, obtaining the welding of the sleeve (<NUM>) to the tube (<NUM>) and producing a device (<NUM>) comprising the tube (<NUM>) with the sleeve (<NUM>);
- optionally removing the heat-shrink elements (<NUM>) from the device (<NUM>);
the method being characterized in that it further comprises the steps of:
- prior to the application of the heat-shrink elements (<NUM>), putting onto the portions of the sleeve (<NUM>) and possibly of the tube (<NUM>) assigned for these heat-shrink elements (<NUM>) respective protective elements (<NUM>), of a material that cannot be fused with the materials of the sleeve (<NUM>) and of the outer coating (<NUM>) of the tube (<NUM>);
- removing the protective elements (<NUM>) from the device (<NUM>).