prevent the fluid from escaping through the interfaces of the fluid pneumatic connections in the articulate joint center element 40 is provided with a central cylindrical recess 44 having sections varying in diameter for purposes that will be described reference being had now to fig8 of the drawings a fastening element such as bolt 28 can be inserted coaxially along axis 20 of rotation portions 46 48 of this center recess are shaped so to fit complementally with the outside diameters of center portions respectively 50 52 of the conduit 12 preferably a water tight but rotatable connection between the center element 40 and conduit 12 is accomplished the outside wall 54 of center element 40 should then be seated so to provide with wall 58 of conduit 12 a cylindrical passageway 56 this substantially cylindrical passageway 56 should curve as seen better in fig3 of the drawings so to present a constant cylindrical area of pneumatic connection between passageway 56 and tapered chamber 32 in operation the fluid flowing through the unique swivel assembly described herein operates as follows fluid enters ingress conduit 12 according to the arrow 14 as seen in fig3 of the drawings as the tapered chamber becomes smaller progressively fluid is forced into the passageway 56 through the substantially annular orifice 24 of the chamber 22 when the fluid first flows through.