A safety device having a tubular support for a needle mount end and a protective shield slidably mounted on the support from a set position, a retracted position and then to a locked position to covers the needle. A locking member mounted on the support, within the shield and a cam follower is engaged with a cam profile on the locking member. Forward axial movement of the support relative to the locking member causes the locking member to rotate relative to the support. The shield has a guide defining a shoulder towards its rearward end and an abutment on the locking member is receivable behind the shoulder when the shield is in its locked position. A spring acts such that when the locking member is turned to engage its abutment with the shoulder of the shield when the latter is in its locked position, so preventing subsequent rearward movement thereof.
