Abstract:
The method for manufacturing a blood filter adapted to be disposed in a blood vessel comprises, in the invention, the steps of a) providing a thin wall comprising a biocompatible material, b) producing in said thin wall a series of essentially parallel elongated sections, for defining the elongated legs, and having the elongated legs joined to each other, at a first end of the elongated sections, wherein step b) comprises the steps of producing adjacent essentially parallel strips comprising a first strip and a second strip separated by a slot, the strips extending essentially parallel the axis and each slot being interrupted at a distance from a second end of the elongated sections, so that the first and the second strips are connected to each other at said second end, by a continuous zone of said thin wall, and having the first strip of the elongated sections joined to each other, at said first end thereof.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a process for manufacturing a blood filter adapted to be disposed within a blood vessel of a mammal body. A specific blood filter is also concerned. 
     Blood filters are already known. 
     For manufacturing blood filters, elongated legs are typically created, together with at least a head for joining the legs together, locally. The legs typically extend round an axis of the filter and are radially movable with respect to the axis and the head, between a first, radially restricted position and a second, radially expanded position in which the legs are diverging from the axis (located farer therefrom than in the first position, along a portion of their length). 
     Examples of such blood filters can be found in U.S. Pat. No. 4,688,553 or U.S. Pat. No. 5,344,427. 
     So, the prior art discloses the following steps for manufacturing a blood filter: 
     (a) using a wall comprising a biocompatible material, and 
     (b) for defining the legs of the blood filter, creating through said wall a series of elongated, essentially parallel sections having a first free end and a second opposed end. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the invention is to improve the steps of manufacturing blood filter. 
     The following objects are especially expected: 
     reducing the steps of assembling the different portions of the filter (legs, head . . . ), 
     reducing the risks possibly induced by local, mechanical constraints created during the steps of manufacturing the blood filter, 
     improving the cohesion between the above-mentioned different portions of the filter, 
     potentially reducing the costs for manufacturing the filter, 
     using possible synergies between the blood filters and the stents or stent grafts. 
     To that aim, an important feature of the invention recommends to make use of the following steps of manufacturing: 
     (c) in at least some of the wall sections materialized during the above-mentioned step (b), adjacent, essentially parallel strips (having a non circular transversal section) are created, said strips comprising at least a first strip and a second strip separated by a slot, the strips extending essentially parallel the axis and the slots interrupting at a distance from the first free end of the corresponding wall sections, so that the first strips are integral with the second strips at said first free end, while the second strips are freely movable from the first strips all along the slots (and especially at the second end of the wall sections), 
     (d) and the first strips are connected therebetween, at the second end. 
     Even if reducing the mechanical constraints within the blood filter as manufactured is an important object, the invention preferably recommends a further step of angularly shifting the second strips with respect to the first strips, so that in the second position, the first strips are angulated with respect to the axis of the blood filter, while the second strips extend substantially parallel the axis. 
     It is to be noted that such an &lt;&lt;angular shifting&gt;&gt; is typically comprised between 30° and 40°, what induces less mechanical constraints in the blood filter than folding back sections of a metallic wire for forming an air pin, as disclosed in U.S. Pat. Nos. 4,688,553, 5,344,427 or 5,383,887. 
     Further, welding a wire and a metallic plate as in FR-A-2 764 503 is avoided. 
     For angularly shifting the corresponding strips, the strips can be mechanically moved or a thermal treatment together with a shape-memory material, such as a super-elastic metallic alloy (NiTi) can be used for shifting said strips and for having the first strips moved between the first and second positions. 
     For improving the reliability of the filter while limiting the costs of manufacturing, it is further recommended, during the step (a), to use an essentially tubular wall and, during step (b), to connect all the first strips one to the others by using a connecting element to which every first strip is fixed, at said second end, the first strips being regularly disposed round the axis. 
     With reference to the blood filter, the following distinctive features are to be noted: the wall sections &lt;&lt;cut&gt;&gt; in the original wall individually have the shape of a plate (showing a non circular section) and comprise at least two strips separated by a slot which is interrupted at a distance from the first end, so that the first strips are integral with the second strips at said first end, so that said firststrips define the legs of the blood filter and the second strips define centering elements for centering the blood filter within the blood vessel. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 diagrammatically shows a laser cutting machine adapted for cutting the tube shown on 
     FIG. 2 (enlarged view), 
     FIG. 3 diagrammatically shows the tube of FIG. 2 after the cutting process, 
     FIG. 4 shows a partial view of a filter manufactured according to the invention, the filter being in its radially expanded position (enlarged view), 
     FIG. 5 shows a way for obtaining a blood filter according to the invention from a flat plate such as illustrated on FIG. 6, 
     FIGS. 7 and 8 diagrammatically show two solutions for maintaining the head of the filter in a curved position round the axis of said filter, 
     FIGS. 9,  10  and  11  diagrammatically show three embodiments of the legs and centering elements of the blood filter, 
     FIG. 12 diagrammatically shows how to cut the shape illustrated on FIG. 9, from a thin tubular wall, and 
     FIG. 13 shows an invaginated tubular wall. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     On FIG. 1, a laser cutting machine is shown. Such a machine can be used for manufacturing a blood filter from a continuous, solid wall having the shape of a tube. 
     Laser cutting is already disclosed in EP-B-0 714 641 (column 9, line 24-column 10, line 9): a thin, essentially tubular wall having a small diameter (such as a cylindrical, metallic tube having a constant section, as referenced  1  on FIG. 2) is disposed round a rotatable mandrel  3  of a numerally driven machine  5  provided with a shaft  7  having a laser  9 , such as a Nd laser. Tube  1  is disposed round the mandrel  3 , then rotated and longitudinally moved (along the axis  11 ) with respect to the laser beam. Portions of the tube material are selectively removed by the laser beam, according to the required shape which presently corresponds to the diagrammatical illustration of FIG.  3 . 
     Cutting the wall can be operated by using another process: for example, the wall can be &lt;&lt;cut&gt;&gt; by chemical etching or by a hot knife, or even by using a CO 2  laser (see U.S. Pat. No. 5,421,955, column 6, line 31-column 7, line 32). A chemical etching process is disclosed in EP-A-0 709 067 (column 2, line 38-column 3, line 28). 
     On FIG. 3, the blood filter comprises elongated, essentially parallel sections of wall, such as referenced  13  and  15 . The elongated sections are essentially parallel the longitudinal axis  17  of the filter (which corresponds to the axis  11  of the tube). 
     Angularly, the elongated sections  13 ,  15  are regularly disposed round the axis. 
     Therefore, what is true in the present description with reference to a specific elongated section (such as referenced  13 ) is also true for the other elongated sections. The elongated section  13  comprises two strips of wall  19 ,  21 , separated by a slot  23  essentially parallel the axis  17 . Slot  23  is interrupted at a distance from the free end  19   a  of the first strip  19 , while it opens at the opposed end,  21   b , so that the two strips  19 ,  21  are connected (or joined) only near, or at, the free end  19   a  (by a zone of wall  25 ), while said strips are free of moving one with respect to the other, along the slot  23  (and especially at the end  21   b  which thus defines a free end for the second strip  21 ). 
     If the proximal end of the filter, opposed to the above-mentioned &lt;&lt;free end&gt;&gt;  19   a  (also called distal end), is referenced  19   b , it will further be noted that all the &lt;&lt;first strips&gt;&gt;, such as  19 , are connected (or joined) together by a connecting means which is presently defined by a strip (or band)  27  of wall extending transversally (especially perpendicular) the axis  17  along which the wall section and strips extend. The strip  27  is integral with all the first strips (such as  19 ) and connects them one to the other, in the immediate vicinity of the proximal end  19   b.    
     On FIG. 4, an illustration more in conformity with a real blood filter than the illustration of FIG. 3, is shown. However, only some of the wall sections as cut are illustrated, for sake of clarity. 
     It is also to be noted that on FIG. 3, the blood filter can be considered as illustrated in its &lt;&lt;radially restricted state&gt;&gt;, (viz. the state it holds within the introducing catheter), whereas on FIG. 4, the filter is in its &lt;&lt;radially expanded stated &gt;&gt;, viz. as it holds within the vessel for filtering any blood clots therein. 
     Especially on FIG. 4, it is shown that the first strips of the wall, such as  19 , define legs which are inclined with respect to axis  17 , whereas the &lt;&lt;second strips&gt;&gt;  21  define centering (or stabilizing) integrated elements. 
     The angulation α, in such a radially expanded state, of the legs such as  19  with respect to the axis  17 , may be of about 30° to 40°. The angulation α is substantially identical to angulation β corresponding to the angulation between the legs and the centering elements (which have to be directed parallel the axis  17 , along a generating line of cylinder having a constant section). 
     The apex of angulation α is located at the proximal end  19   b  of the filter (typically called &lt;&lt;filter head&gt;&gt;). The cone of filtration defined by the legs opens up to the distal end  19   a  where the legs are far away one from the others, in the radially expanded state of FIG.  4 . 
     The following material (or covering) can be cited for the original wall 1: stainless steel, nitinol® which is a super elastic alloy having a thermal memory shape, titanium, or even plastic material (such as thermoplastic polymer). So, the state illustrated on FIG. 4 can be reached by the natural elasticity of the strips  19 ,  21 , or further to a variation of temperature if a thermal memory alloy is used. 
     Two structural differences can be found between the illustrations of FIGS.  3  and  4 : on FIG. 4, the first strips, such as  19 , are connected to one another, near the end  19   b , by using a complementary member  29 . Further, the anchors such as  31   a ,  31   b , are integrated to the centering elements  21 . 
     The complementary member  29  is a metallic, partially hollow cap within which the legs are welded. With such a connection, the legs  19 , before being connected one to the other by the cap  29 , are independent. Those independent legs (which then have a free end  19   c ) are disposed in a close position at said end and are connected to the cap  29  which thus, define the connecting head of the legs. 
     The creation of the integrated anchors  31   a ,  31   b  is clearly illustrated on FIG. 5 which shows an embodiment (not the best mode) for manufacturing the filter illustrated on FIG. 4, from a flat plate, such as the plate referenced  30  on FIG.  6 . 
     On FIG. 5, the flat wall  30  is already &lt;&lt;cut&gt;&gt;, viz. slots defining the strips having a plate shape (thus showing a non circular section) have been created for defining the legs and integrated centering elements of the filter. 
     On FIG. 5, the parallel wall sections defined by the cuts of the plate begin from the upper connecting band  27 . The resulting parallel wall sections, such as those referenced  13 ,  15 , one more time, comprise a first strip  19  having a reduced width referenced  33   a ,  33   b , said first strip extending at the axial end  19   a  (opposite the band  27 ) by a second strip (such as  21 ) integral with the first strip (the hairpin connection zone between the first and second strips is referenced  25 ). 
     At the level of the reduced width  33   a ,  33   b , the second strips have also a reduced width for defining the corresponding integrated anchors, such as  31   a ,  31   b.    
     Towards the proximal end  19   b , the second strips  21  are interrupted at a distance from the end, so that the second (&lt;&lt;backward&gt;&gt;) strips are shorter than the first (&lt;&lt;frontward&gt;&gt;) strips. Thus, hollow spaces, such as  36   a ,  36   b  are materialized through the wall. 
     After having created such a shape, the first strips  19  are angularly shifted with respect to the transversal band  27 , whereas the second strips  21  are maintained substantially parallel the axis  17 . 
     Before that step, or after, the resulting shape is rolled on itself round the axis  17 . 
     Thus, a blood filter having elongated legs showing the shape of a substantially frustoconical shape, having an axial opening through its band  27  (head) and a free end  19   a  where, in such a radially expanded state, the filter shows its larger diameter, is created. 
     A welding  35  can be used for maintaining the filter rolled on itself, at its head zone  27 , where the two opposed ends  37   a ,  37   b  of the wall can overlap, as illustrated on FIG.  7 . 
     Alternatively, FIG. 8 shows that those two ends can face each other, with no fixation means therebetween. 
     On FIGS. 9,  10  and  11 , are diagrammatically illustrated some among other possible shapes for the legs and centering elements of the blood filter. 
     So, on FIG. 9, a &lt;&lt;W&gt;&gt; shape is shown comprising two lateral strips  39  defining the legs of the filter. Each strip  39  is integral with a central centering member  41  having the shape of an inverted &lt;&lt;V&gt;&gt;. Two slots  40   a ,  40   b  define an inverted &lt;&lt;V&gt;&gt;, so that they are essentially parallel to the axis  42 . 
     Such shapes can be created for example from the tube  43  of FIG. 12 in which strips are cut as illustrated, the strips being thereafter slightly angularly shifted for obtaining the required filter shape. 
     On FIG. 10 is illustrated a central elongated leg having a zigzag shape (so essentially parallel to the axis  47  of the filter). Said elongated leg  45  is integrally connected with two lateral centering members  47   a ,  47   b , at the end  45   a.    
     On FIG. 11, two legs  49 ,  51  are diagrammatically illustrated. Those two legs are integrally connected with a continuous, transversal band  53  and extend, at an end opposite said band (respectively referenced  49   a  and  51   a ), in centering members having an inverted &lt;&lt;V&gt;&gt; shape, respectively referenced  149  and  151 . 
     Those examples show that various shapes can be created for the legs and the centering elements (or members) of the filter. An important feature is to draw one or a series of leg(s) and centering element(s) from an original wall in which the required shape is &lt;&lt;cut&gt;&gt; (viz. created), together with at least one slot essentially parallel the axis of the blood filter (which axis can be considered as the same than the axis of the blood vessel, once the filter is implanted in said vessel). 
     It is further to be noted that the tubular wall of FIG. 2 could be changed to an invaginated tubular wall  60  (especially a frustoconical wall) such as the wall illustrated on FIG.  13 .