A medical infusion device, comprising: a base (121, 221); a catheter hub (141, 241, 331, 431) movable from a first catheter hub position to a second catheter hub position; a flexible catheter (141,241,341) connected to said catheter hub, said catheter being disposed substantially entirely within said base when said catheter hub is in said first catheter hub position and said catheter having a free disposed externally of said base when said catheter hub is in said second catheter hub position; an introducer hub (131, 231, 341, 441, 541) movable between a first introducer hub position and a second introducer hub position; an introducer needle (134, 231, 334) located within said catheter and connected to said introducer hub, said introducer needle being disposed substantially entirely within said base when said introducer hub is in said first introducer hub position and said introducer needle having a free end disposed externally of said base when said introducer hub is in said second introducer hub position; a torsion spring (181, 281, 381, 481, 581) for moving said catheter hub and said introducer hub, said torsion spring initially rotating a disc (171, 271, 503) or drive gear (303, 403) in a rotational direction to move said catheter hub from said first to said second catheter hub position and said introducer hub from said first to said second introducer hub position to facilitate insertion of said catheter, characterized in said torsion spring then further rotating said disc or drive gear in the same rotational direction to move said introducer hub back toward said first introducer hub position to store said introducer needle within said base with said free end of said catheter remaining disposed externally of said base; and a linking arm (151, 251, 351, 451) coupled to said introducer hub and to said disc or drive gear, the coupling between said disc or drive gear and said linking arm being at fixed points on each of said disc or drive gear and said linking arm, said disc or drive gear and said linking arm together forming a rotary crank mechanism for converting rotary motion from said torsion spring to linear motion of said introducer hub. a base (121, 221); a catheter hub (141, 241, 331, 431) movable from a first catheter hub position to a second catheter hub position; a flexible catheter (141,241,341) connected to said catheter hub, said catheter being disposed substantially entirely within said base when said catheter hub is in said first catheter hub position and said catheter having a free disposed externally of said base when said catheter hub is in said second catheter hub position; an introducer hub (131, 231, 341, 441, 541) movable between a first introducer hub position and a second introducer hub position; an introducer needle (134, 231, 334) located within said catheter and connected to said introducer hub, said introducer needle being disposed substantially entirely within said base when said introducer hub is in said first introducer hub position and said introducer needle having a free end disposed externally of said base when said introducer hub is in said second introducer hub position; a torsion spring (181, 281, 381, 481, 581) for moving said catheter hub and said introducer hub, said torsion spring initially rotating a disc (171, 271, 503) or drive gear (303, 403) in a rotational direction to move said catheter hub from said first to said second catheter hub position and said introducer hub from said first to said second introducer hub position to facilitate insertion of said catheter, characterized in said torsion spring then further rotating said disc or drive gear in the same rotational direction to move said introducer hub back toward said first introducer hub position to store said introducer needle within said base with said free end of said catheter remaining disposed externally of said base; and a linking arm (151, 251, 351, 451) coupled to said introducer hub and to said disc or drive gear, the coupling between said disc or drive gear and said linking arm being at fixed points on each of said disc or drive gear and said linking arm, said disc or drive gear and said linking arm together forming a rotary crank mechanism for converting rotary motion from said torsion spring to linear motion of said introducer hub.