A kind of metering formula syringe,System comprising pinhead sleeve group,Shot sleeve group,Injection putter group and metering ring,Pinhead sleeve group connects flask for medicinal preparations to group,Shot sleeve group is arranged on the outside of what flask for medicinal preparations,And removable group group connect pinhead sleeve group,Injection putter group is arranged in what shot sleeve group with its body of rod socket metering ring,The metering formula syringe loads flask for medicinal preparations injection Hou every time,Pinhead sleeve group can be abandoned together with flask for medicinal preparations dismounting,Shot sleeve group,Injection putter group is combined with metering ring, can be reused,And by the thread groove between metering ring and the body of rod and interfere screw thread convex block matching construction,And the ratchet slot of metering ring is combined with the snap-on in shot sleeve group,When making to dismount flask for medicinal preparations every time and pull injection putter group to Hou,Automatic count reuses number,When reaching preset access times,Metering ring can not rotate again,Injection putter group can not Hou draw use,The metering formula syringe is avoided excessively to reuse,Ensure safety in utilization.一種計次式注射器，係包含針頭套組、注射套筒組、注射推桿組與計次環，針頭套組用以組接藥劑瓶，注射套筒組套設於藥劑瓶外側，且可拆組地組接針頭套組，注射推桿組以其桿體套接計次環而設置於注射套筒組內，該計次式注射器每次裝填藥劑瓶注射後，可將針頭套組連同藥劑瓶拆除拋棄，注射套筒組、注射推桿組與計次環之組合則能重複使用，並藉計次環與桿體間之螺紋槽與干涉螺紋凸塊匹配構造，以及計次環之棘齒槽與注射套筒組中之彈扣組合，使每次拆裝藥劑瓶而向後拉動注射推桿組時，自動計數重複使用次數，到達預設的使用次數時，計次環無法再旋轉，注射推桿組無法後拉使用，避免該計次式注射器過度重複使用，確保使用安全性。
