An insertion mechanism for a drug delivery device. The insertion mechanism includes a proximal end, a distal end, a first opening placed near the proximal end, and a second opening located at the distal end. A needle or cannula assembly is disposed within the housing and has a base having a proximal surface and a distal surface and a needle or cannula coupled to the distal surface. A retraction member is disposed within the housing to hold the needle or cannula assembly in the retracted position until it is moved to the extended position, the retraction member contacting the base. The needle assembly is moved from the retracted position to the extended position when pressure is supplied from the first opening until an amount of pressure P1 exerts an actuating force on the proximal surface of the base that exceeds the drag force of the retracting member. .薬剤送達装置のための挿入機構。挿入機構は、近位端と、遠位端と、近位端の付近に留置された第一の開口と、遠位端に配置された第二の開口と、を含む。針又はカニューレアセンブリはハウジング内に配置され、近位面と遠位面を持つ基部と、遠位面に連結された針又はカニューレと、を有する。引込部材がハウジング内に配置されて、針又はカニューレアセンブリを伸展位置に移動するまで引込位置に保持し、引込部材は基部と接触する。第一の開口から、ある量の圧力Ｐ１が引込部材の抵抗力を超える作動力を基部の近位面に加えるまで圧力が供給されると、針アセンブリが引込位置から伸展位置へと移動される。
