Tubular product

#General Background and State of the Art

#This invention relates to variable-property products, and methods for making such products.

#A variable-property product is an article that has varied material properties such as stiffness and/or surface frictions and/or elasticity. As an example, medical catheters may be constructed with variable stiffness properties. These catheters have been developed to have different degrees of flexibility throughout their length to satisfactorily meet the requirements of flexibility and also stiffness for manipulation.

#FIG. 1 illustrates a broad structural diagram for the present invention;

#FIG. 2 shows a variable stiffness tubing;

#FIG. 3 shows a multi-polymer jacketed core;

#In the following description of the preferred embodiments reference is made to the accompanying drawings which form the part thereof, and in which are shown by way of illustration of specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope of the present invention.

#An exemplary system of the present invention for making elongated products such as tubing in a tip-and-die assembly with injectors is illustrated in the drawings at FIG. 1. A core 50, such as a continuous wire, is fed from a reel 50a of a wire through a head 51 at a predetermined speed. At the same time, two different polymers, in pellet forms 52a and 52b, are converted into molten polymer streams in two different polymer injectors 53a and 53b respectively. These molten polymers are pushed by the injectors 53a and 53b, one shot at a time, through a flow controller 54 and through the head 51, to form a continuous, multi-polymer jacket around the core, to effectively coat the core. These polymer shots are made in a cyclic, sequential fashion. It is this synchronized, repeating cycles of the polymer shots that keep the polymer jacket continuous on the core 50. The polymer-jacketed core is then cooled down to solidify the polymers, and then measured and collected.

#An example is shown in FIG. 2, where the length 56 is sixty inches, the diameter 57 of the product with the polymer jacket 55 is 0.05 inch and the diameter 58 of the core 50 is 0.03 inch.