Abstract:
Extruded articles, such as tubing or multilumen catheters, having hybrid composition, an axial length and a transverse cross-section orthogonal to the length. The extruded articles have unitary construction and require no assembly. The composition of each cross-section of the article along the length of the article contains a first extrudable material and/or a second extrudable material. The percentage and/or distribution of the two extrudable materials in any cross-section varies along the length of the article in a controlled, continuous or discontinuous manner. The first and second extrudable materials may be an elastomer having different durometers, color or radiopacity. The weight percentage of one of the two extrudable materials in a cross-section may vary abruptly, smoothly and/or periodically along the length of the article. An extrusion die and a method for using the die for making the hybrid, unitary extruded articles is disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates generally to extruded articles and, more particularly, to extruded elastomeric articles and, even more particularly, to hybrid elastomeric extruded articles.  
           [0003]    2. Prior Art  
           [0004]    The term “hybrid article”, as used herein, refers to an extruded article having unitary construction and comprised of two or more extrudable materials having different physical or chemical properties. Such hybrid articles are known in the art and are made by means of extrusion through a two chamber extruder as described, for example in U.S. Pat. Nos. 4,282,876 and 5,196,005. A first chamber contains an elastomer having first properties such as, for example, radiopaque silicone or uncured silicone with air bubbles or a foaming agent incorporated therein. The second chamber contains a radiolucent silicone or a degassed silicone elastomer. The elastomer compositions contained with the two separate chambers are simultaneously forced through a single die orifice. The extruded tubing comprises two axially concentric layers of extrudate. The extruder may further include means for varying the shape and size of the die orifice and thus the extruded article&#39;s outer diameter as disclosed, for example, in U.S. Pat. No. 5,511,965. In this manner, the extruded hybrid article is formed by extrusion then cured by vulcanization.  
           [0005]    U.S. Pat. No. 3,752,617, to Burlis, discloses a method and apparatus for producing tubing having different characteristics along its axial length. In general, &#39;617 provides a method for making tubing either: (a) having a single composition comprising a mixture of extrudable polymers; or (b) having concentric, coaxially disposed inner and outer layers. Burlis also suggests methods for changing the physical properties of the tube as it is extruded. In the first variation, there are two extruders, one for homogenizing and delivering a first polymer to a mixing die and a second extruder for homogenizing and delivering a second polymer to the same mixing die. A sequencing control provides, at various time intervals, an increased flow from one of the extruders and a proportionally decreased flow from the other extruder. The mixture of the two polymers passes through the die and results in an extruded tubing having varying physical parameters along its axial length.  
           [0006]    U.S. Pat. No. 4,385,635, to Ruiz, teaches a hybrid angiographic catheter having a soft, flexible, pliable leading tip zone, a main reinforced length, and an intermediate zone between the tip zone and the main length. The main length is made up of a polyamide such as nylon, and the intermediate zone contains a polyamide which is tapered distally and is jacketed by polyurethane. The soft tip is entirely polyurethane. A method for making the device wherein it has unitary construction is not disclosed.  
           [0007]    U.S. Pat. No. 4,775,371, to Mueller, Jr., discloses a hybrid balloon catheter having a multilayered shaft. The shaft may be structured in such a fashion that the various layers taper axially in one fashion or another, typically to permit the distal section to be more flexible than the proximal section. However, rather than being coextruded, the various layers are independently extruded. The outer layer comprises a polymer tube which may be fitted over the inner layer and constricted thereonto.  
           [0008]    U.S. Pat. No. 5,125,913, to Quackenbush, describes a double-layer medical catheter having an integral soft tip made by the co-extrusion of a relatively rigid inner layer and a relatively soft outer layer. The extrusion equipment is operated to interrupt the supply of the extrudable material comprising the inner, relatively soft layer in order to cause a periodic void in the inner wall as the catheter is extruded. By interrupting the supply of elastomer, a transition in the inner wall thickness occurs at the leading and trailing edge of each void. The void is then cut to produce two soft-tipped catheters.  
           [0009]    In accordance with the forgoing teachings, the need for hybrid catheters is well recognized in the art. In certain applications it is desirable to provide an extruded article such as a catheter wherein the composition of the catheter varies along the length of the catheter while the catheter is of unitary construction. For example, it is desirable to provide an indwelling catheter wherein the durometer of the tip or implanted portion of the catheter is different from the extracorporeal portion of the catheter (Martin, U.S. Pat. No. 5,057,073). Until the present invention, such articles either lacked unitary construction, and have been assembled from separate parts, or the limitations of the state of the art prevented or limited the extrusion of custom hybrid catheters having a complex distribution of elastomers along the axial length thereof. In another application, it may be desirable to provide a unitary catheter or drain having radiopaque markings thereon, the marks being disposed to indicate a distance along the catheter or, in another application, the radiopaque marks may be employed to indicate, in vivo, the position of a transition between different portions of a drain. The continuing need for such hybrid extrudable articles having unitary construction in versatile, custom configurations and a method for making such articles is met by the present invention.  
         SUMMARY  
         [0010]    It is an object of the present invention to disclose a hybrid extruded article having unitary construction. The article has a length in the direction of extrusion and a transverse cross-section orthogonal to the length of the article. A cross-sectional portion of the article is comprised of a first weight of a first extrudable material and a second weight of a second extrudable material wherein the ratio of the first weight to the second weight in cross-sectional portions varies along the length of the article.  
           [0011]    It is another object of the present invention to disclose a hybrid extruded article having unitary construction wherein the article has a length in the direction of extrusion and a transverse cross-section orthogonal to the length of the article. A cross-sectional portion of the article is comprised of a first extrudable material and a second extrudable material wherein the distribution of the first extrudable material in cross-sectional portions varies along the length of the article.  
           [0012]    It is a further object of the invention to provide a method and apparatus operable for making articles meeting the above objectives of the invention.  
           [0013]    The features of the invention believed to be novel are set forth with particularity in the appended claims. However the invention itself, both as to organization and method of operation, together with further objects and advantages thereof may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a plan view of a unitary hybrid article comprising a length of tubing in accordance with a preferred embodiment of the present invention wherein the composition of the tubing varies in a step-wise manner along the length thereof.  
         [0015]    [0015]FIG. 2 a  is a front plan view of an extruder die showing the bridge die positioned for the extrusion of a first composition  11  of an extrudable material from the extrusion die.  
         [0016]    [0016]FIG. 2 b  is a front plan view of an extruder die showing the bridge die positioned for the extrusion of a second composition  12  of an extrudable material from the extrusion die.  
         [0017]    [0017]FIG. 3 a  is a top plan view of an extruder die showing the bridge die positioned for the extrusion of extrudable material  11  from the die.  
         [0018]    [0018]FIG. 3 b  is a top plan view of an extruder die showing the bridge die positioned for the extrusion of extrudable material  12  from the die.  
         [0019]    [0019]FIG. 3 c  is an enlarged top plan view of the extruder die illustrated in FIG. 3 b  showing the bridge die positioned for the extrusion of extrudable material  12  from the die.  
         [0020]    [0020]FIG. 4 is a perspective view of segmented portions of a unitary hybrid article comprising a length of drainage tubing in accordance with a second preferred embodiment of the present invention wherein the distribution and/or amount of a radiopaque extrudable material comprising the drainage tubing varies in a continuous manner along the length thereof.  
         [0021]    [0021]FIG. 5 a  is a top plan view of an extruder die operable for the extrusion of a drainage tubing as shown in FIG. 4 showing the flow channel that conducts the radiopaque extrudable material to the die orifice partially obstructed to restrict the flow of radiopaque extrudable material from the extrusion die.  
         [0022]    [0022]FIG. 5 b  is a front plan view of an extruder die operable for the extrusion of a drainage tubing as shown in FIG. 4 showing the flow channel that conducts the radiopaque extrudable material to the die orifice partially obstructed to restrict the flow of radiopaque extrudable material into the output orifice of the extrusion die.  
         [0023]    [0023]FIG. 6 a  is a top plan view of an extruder die operable for the extrusion of a drainage tubing as shown in FIG. 4 showing the flow channel that conducts the radiopaque extrudable material comprising the stripe to the die orifice partially obstructed to restrict the flow of radiopaque extrudable material from the extrusion die thereby producing a narrow stripe in the extruded drainage tubing.  
         [0024]    [0024]FIG. 6 b  is a front plan view of an extruder die operable for the extrusion of a drainage tubing as shown in FIG. 4 showing the flow channel that conducts the radiopaque extrudable material comprising the stripe to the die orifice fully open to maximize the flow of radiopaque extrudable material from the extrusion die therby broadening the stripe in the extruded drainage tubing.  
         [0025]    [0025]FIG. 7 is a cross-sectional view along section line  7 - 7  of the tubing of FIG. 1 extruded when the flow channel selector control element comprising the extruder die is positioned as illustrated in FIGS. 2 a  and  3   a.    
         [0026]    [0026]FIG. 8 is a cross-sectional view along section line  8 - 8  of the tubing of FIG. 1 formed when the flow channel selector control element comprising the extruder die is positioned as illustrated in FIGS. 2 b  and  3   b.    
         [0027]    [0027]FIG. 9 is a cross-sectional view along section line  9 - 9  of the drainage catheter of FIG. 4 extruded when the radiopaque stripe width control element comprising the extruder die is positioned as illustrated in FIGS. 5 a  and  5   b.    
         [0028]    [0028]FIG. 10 is a cross-sectional view along section line  10 - 10  of the drainage catheter of FIG. 4, formed when the radiopaque stripe width control element comprising the extruder die is positioned as illustrated in FIGS. 6 a  and  6   b.   
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    Turning now to FIG. 1, a hybrid extruded tubing in accordance with an embodiment of the present invention is shown in elevational view at numeral  10 . The tubing  10  has an axial length L and an axial lumen (not visible in FIG. 1, but indicated at  70  in FIG. 7) coextensive with the length L. The tubing  10  is comprised of alternating amounts of two different elastomeric compositions: a first composition  11  and a second composition  12 , coextruded from an extruder die as indicated at numeral  20  in FIGS. 2 a - 3   b.  The relative quantities of compositions  11  and  12  within a cross-sectional area of the tubing  10  vary in their distribution along the axial length L of the tubing  10 . For example, if the tubing  10  is a catheter with a leading end or tip  13  and a trailing end  14 , the composition  11  may be selected to have a durometer, when cured, that is less than the durometer of composition  12  which may form the remaining length of the catheter. In another embodiment, the composition  11  may be radiopaque while the composition  12  is radiolucent. If the percentage of composition  11  varies between 0-100% in discrete incremental distances along the length L, the segments comprised of 100% of composition  11  may be used as markers to determine the position of the tube with respect to tissues within the body.  
         [0030]    An extrusion die  20  adapted for making a unitary extruded tubing in accordance with FIG. 1 is shown in FIGS. 2 a - 3   c.  Turning first to FIGS. 2 a  and  3   a,  a die  20  adapted to extrude the hybrid tubing of FIG. 1 is shown in front view. The die  20  comprises a slidably mounted bridge die plate  25  having an aperture  27  therein. First and second extrudable materials  11  and  12  are contained, under pressure, in reservoirs  21  and  22  having reservoir output nozzles  23  and  24  respectively. The slidably mounted bridge die plate  25  is mechanically or electromagnetically connected to an actuator  26  that controls the position of the aperture  27  with respect to the extrudate reservoir output nozzles  23  and  24 . The actuator, which is preferably programmable, forces the aperture  27  to commute reciprocally between the reservoir nozzles  23  and  24  alternately forcing extrudable materials  11  and  12  past the mandrel  33  (FIG. 3 c ) and through the die aperture  27 . FIGS. 2 a  and  3   a  illustrate the position of the die aperture  27  when first and second extrudable materials  11  and  12  are respectively forced through the aperture  27 .  
         [0031]    Surprisingly, even though the commutation of the die aperture  27  between the output nozzles  23  and  24  causes periodic angular displacement of the die aperture  27  with respect to the direction of extrusion of the tubing  10  during the extrusion process, the structural integrity of the extruded tubing is not compromised. Structural irregularity of the extruded tubing due to mechanical displacement of the die aperture during extrusion is minimized by increasing the distance between the die aperture  27  and the vulcanizer (not shown) that receives the extruded tubing  10 . A distance of 10-20 inches is adequate. For an extrusion speed of 2-6 in./sec., and a transition (commutation) speed of 12 in./sec., the extrudate would travel 2″/sec X0.02 sec=0.04″ during the switching operation. Because the flow of either extrudable material  11  or  12  is completely interrupted for part of that time period, the portion of the extruded elastomeric tubing between the die aperture and the downstream vulcanizer probably stretches during the switching time interval, thereby compensating for the interruption in the flow of extrudable material to the die aperture.  
         [0032]    With reference now to FIG. 3 c,  a portion of the bridge die plate  25  is shown in greater detail positioned to receive second extrudable material  12  as indicated in FIG. 3 b.  The bridge die plate  25  includes a bridge  30  having a mandrel  33  affixed to the bridge  30 . A die  32  having an aperture  27  therein is press-fitted into the bridge die plate  25  to complete the assembly of the bridge die plate. The bridge die plate  25  has a receiving chamber  34  that is in material flow communication with nozzle  24  (not shown in FIG. 3 c ). Second extrudable  12  is forced under pressure into receiving chamber  34  and exits the die aperture  27 . After the desired amount of second extrudable material  12  exits the die aperture  27 , the actuator repositions the bridge die plate  25  in order to establish material flow communication between the receiving chamber  34  and nozzle  23 , permitting the first extrudable material  11  to exit the die aperture  27 . Cross-sectional views of tubing  10  taken along section lines  7  and  8  are presented in FIGS. 7 and 8 illustrating the composition of the tubing  10  formed when the bridge die plate is disposed as indicated in FIGS. 3 a  and  3   b  respectively.  
         [0033]    The “Blake” drain, disclosed in U.S. Pat. No. 4,465,481, has been a mainstay of general surgery since its introduction nearly 20 years ago; providing an efficient, low profile percutaneous drain. The Blake drain normally includes an invasive collection segment having a radiopaque marker integral therewith which enables non-invasive radiographic positioning or re-positioning of the drain segment within the body. A wound drain suitable for insertion into the body and having unitary construction is disclosed by Batdorf et al. in U.S. Pat. No. 5,549,579. The Batdorf drain has a smooth exterior surface and is extruded in a single step to provide a unitary drain having substatially homogeneous elastomeric composition. The Batdorf drain may further comprise a radiopaque marker. Other drains such as, for example, the Jackson-Pratt wound drain are not unitary; comprising a composite structure fabricated by joining separate parts by suitable adhesive means. Such composite drains may disintegrate within the body requiring surgical intervention. While the prior art drains may include a radiopaque marker thereon, it is desirable to provide a drain wherein the radiopaque marker indicates, inter alia, the position of the transition between the collection and the drainage portion of the drain within the body.  
         [0034]    [0034]FIG. 4 is a perspective view of segmented portions of a unitary hybrid article comprising a length of drainage tubing  40  in accordance with a second preferred embodiment of the present invention wherein the distribution and/or amount of a first extrudable material  41 , which is preferably radiopaque, varies in a continuous manner along the length of the drainage tubing. The drain  40  includes a collection segment  42 , a transition segment  43  and a extension segment  44 . The collection segment  42  is adapted to be inserted within a wound or body cavity thereby providing a fluid-conducting drainage port through which bodily fluids accumulating within a wound or body cavity readily enter and pass for removal from the body. The body fluids (not shown) enter the drain  40  through the lateral grooves  45  which are coextensive with the collection segment; beginning at the distal end of the transition segment  43  and terminating at the distal end  46  of the drain. The body fluids pass through the collection segment  42 , into the transition segment  43  and into the extension segment  44  where the fluids are collected by means of gentle suction applied to the proximal end  47  of the drain. The entire drain  40  is a hybrid elastomeric article comprising a radiopaque elastomer  41  and a structural elastomer  48  and having unitary construction. The radiopaque elastomer  41  is present as a single stripe coextensive with the extension portion  44 , bifurcating at the distal end of the transition portion  43 , the bifurcated stripes of radiopaque elastomer  41  thereafter being coextensive with the collection portion  42  of the drain  40 .  
         [0035]    The drain  40  is made by extrusion from an extruder die as shown in FIGS. 5 a - 6   b.  FIG. 5 a  is a top plan view of an extruder die  50  operable for the extrusion of a drainage tubing as shown in FIG. 4 showing the flow channel that conducts the radiopaque extrudable material  41  to the extrusion chamber adjacent to the die aperture partially obstructed to restrict the flow of radiopaque extrudable material from the extrusion die. FIG. 5 b  is a front plan view of the extruder die  50 , the structural elements comprising the extrusion die  50  positioned in accordance with FIG. 5 a.  The radiopaque elastomer  41  is housed within a first pressurized reservoir  51  having a nozzle  52  in material flow communication with an extrusion chamber  53  by means of a valve  54 . A second, structural elastomer  48  is housed within a second reservoir  55  and is forced into extrusion chamber  53 , under pressure, as indicated by the broad arrow. Since the radiopaque elastomer is injected into the extrusion chamber  53  adjacent to the mandrel  56  and die aperture  57 , it is confined to a narrow region around the circumference of the extruded article and forms a stripe thereon.  
         [0036]    The operation of the valve  52  is illustrated in FIGS. 5 b  and  6   b.  With reference to FIG. 5 a,  which shows the valve positioned to form a narrow stripe of radiopaque elastomer  41  on the extruded drain  40 , the valve  52  comprises a slidably mounted rod  60  having a hole  61  bored transversely therethrough. The rod  60  is in mechanical or electromagnetic connection with an actuator  62 . When the rod  60  is retracted in the direction of the actuator, as shown in FIG. 5 b,  the hole  61  is in misalignment with the lumen  63  of the valve  52 , thereby partially obstructing the lumen  63  and restricting the flow of radiopaque elastomer  41  from the reservoir  51 .  
         [0037]    The mandrel  56  is comprised of two coaxially counted members, only the outermost member being shown in FIGS. 5 a - 6   b.  The outermost member is a cylindrical tubing having an axial bore and four prongs on an end thereof adjacent the die aperture  57 . A cylindrical rod having a blunt end is slidable mounted therewithin. Both members of the mandrel are connected to actuators such that when the extension portion  44  of the drain  40  is being extruded, the outer, pronged member is retracted and the blunt-ended inner member projects into the die aperture  57 . When the transition portion  43  of the drain  40  is formed, the outer, pronged member comprising the mandrel  56  is advanced into the die aperture  57  and the blunt-ended inner rod retracted. Only the pronged end of the outermost member of the mandrel  56  partially occludes the die aperture  57  during extrusion of the collection portion  42  of the drain  40 . Cross-sectional views of the extension portion  44  and collection portion  42  of the drain  40  are shown in FIGS. 9 and 10 respectively.  
         [0038]    While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.