fig1 to 4 show a shaft 10 according to a first embodiment of the invention , wherein fig1 is a three - dimensional view , fig2 is a three - dimensional , transparent illustration , fig3 is a longitudinal sectional view , and fig4 is a three - dimensional view showing the shaft 10 in cross - section . the shaft 10 comprises an inner tube 11 and an outer tube 12 , the inner tube 11 being arranged inside the outer tube 12 . the inner tube 11 and the outer tube 12 are flexible and preferably free of openings in a radial direction , respectively . the inner tube 11 and the outer tube 12 are arranged co - axially , i . e . they have a common longitudinal axis . when viewed in cross - section , a spiral wall 13 projects radially from an outer surface of the inner tube 11 to an inner surface of the outer tube 12 . in a longitudinal direction of the shaft 10 , the spiral wall 13 runs helically around the inner tube 11 with the common longitudinal axis of the tubes 11 , 12 as center axis . preferably , the inner tube 11 , the outer tube 12 and the spiral wall 13 are formed monolithically of polymeric material . in more detail , the shaft is produced by twisting the shaft 10 about its longitudinal axis when it is extruded . thus , a central inner tube 11 is formed which is surrounded by a spiral shaped inflation lumen 14 which is formed between the radially outer surface of the inner tube 11 and the radially inner surface of the outer tube 12 . this inflation lumen 14 runs longitudinally through the entire length of the shaft 10 , i . e . from a proximal end 15 of the shaft 10 to a distal end 16 of the shaft 10 . the inside of the inner tube 11 is separated in a fluid - tight manner from the inflation lumen 14 . fig5 and 6 show a shaft 20 according to a second embodiment of the invention , wherein fig5 is a three - dimensional view , and fig6 is a longitudinal sectional view . the shaft 20 comprises an inner tube 21 and an outer tube 22 , the inner tube 21 being arranged inside the outer tube 22 . the inner tube 21 and the outer tube 22 are flexible and preferably free of openings in a radial direction , respectively . preferably , the inner tube 21 and the outer tube are arranged co - axially . when viewed in cross - section , a spiral wall 23 projects radially from an outer surface of the inner tube 21 without contacting an inner surface of the outer tube 22 . also in cross - section of the shaft 20 , the spiral wall 23 has a rounded cross - section , preferably a circular cross - section , the outer circumferences of the inner tube 21 and the spiral wall 23 overlap slightly in the area in which these elements are connected . in a longitudinal direction of the shaft 20 , the spiral wall 23 runs helically around the inner tube 21 with the common longitudinal axis of the tubes 21 , 22 as center axis . preferably , the inner tube 21 and the spiral wall 23 are formed monolithically . the inner tube , the outer tube 22 and the spiral wall 23 are preferably made of polymeric material . the second embodiment of the invention allows , to manufacture the inner tube 21 with the spiral wall 23 formed on it separately from the outer tube . in more detail , the inner tube 21 is produced with the spiral wall 23 formed on it by twisting or rotating the inner tube 21 about its longitudinal axis when it is extruded . the outer tube 22 can simply be extruded without twisting . thereafter , the inner tube 21 can be inserted into the outer tube 22 . thus , a central inner tube 21 is formed which is surrounded by a inflation lumen 24 which is formed between the radially outer surface of the inner tube 21 and the radially inner surface of the outer tube 22 , wherein the inflation lumen 24 has a spiral wall influencing the flow characteristics . this inflation lumen 24 runs in a longitudinally direction through the entire length of the shaft 20 , i . e . from a proximal end 25 of the shaft 20 to a distal end 26 of the shaft 20 . the inside of the inner tube 21 is separated in a fluid - tight manner from the inflation lumen 24 . while the invention has been illustrated and described in detail in the drawings and foregoing description , such illustration and description are to be considered illustrative or exemplary and not restrictive and it is not intended to limit the invention to the disclosed embodiments . the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously .
the application relates to a shaft for medical devices comprising an inner tube and an outer tube , wherein the inner tube and the outer tube extend concentrically with a common longitudinal axis from a proximal end to a distal end of the shaft , and a spiral wall projecting radially outwards from the inner tube . further , the application relates to a catheter having such a shaft .