A cannula insertion device (1) is disclosed. The device includes a needle carriage (10), a rail device (82, 84, 86, 88) on which the needle carriage (10) is slidable, a yoke (54) having a channel (546), a linkage (20) connected to the needle carriage (10) and extending into the channel (546), a torsion spring (30) with one end connected to the linkage (20), and locking device (90) for locking the torsion spring (30) in tension and maintaining the needle carriage (10) and the linkage (20) in a locked position prior to activation. Upon release of the locking device (90), the tension of the torsion spring (30) is released, which causes the linkage (20) to move in the channel (546) and slide the needle carriage (10) along the rail device (82, 84, 86, 88). A catheter carriage (60) may also be provided for actuation by the linkage (20).
