INJECTION DEVICE

摘要

An injection device (1) includes a syringe (7) having a needle (23), a barrel (21) and a plunger (25). The device is arranged to provide an automatic injection cycle including advancing a needle for insertion, dispensing liquid from the barrel and retracting the needle. The device includes a drive coupling arrangement between a driving spring (13) and the syringe (7). The drive coupling arrangement includes a first part (15) and a second part (17). A drive force is selectively transmitted or not transmitted between the first and second parts in use depending upon their relative rotational positions such that when the first and second parts (15, 17) are in a first relative rotational position during the dispensing stage a driving force is transmitted to the plunger to drive the plunger into the barrel, and when the first and second parts (15, 17) are in a second relative rotational position during the retraction stage no force is transmitted to the plunger to allow the plunger and the syringe to retract. The drive coupling arrangement transmits a driving force from spring (13) to drive forward the syringe during a needle advancement stage to advance the needle and during the dispensing stage drives the plunger (25) into the barrel (21) for dispensing liquid depending upon the configuration of the drive coupling arrangement.