US Patent 7462168 Safety pen needle with passive safety shield system

A pen needle shield system according to the invention comprises at least an injection end shield positioned on the injection side of the hub, shielding the injection end of the needle after an injection, or in the event of an accidental triggering. The injection end shield is compressed toward the hub against the pressure of a biasing spring. The injection end shield engages a sleeve, which is arranged coaxially on the hub such that after the injection is administered the biasing spring pushes the injection end shield to cover the injection end of the needle, carrying the sleeve with it. The sleeve engages the hub, locking out the injection end shield in a position in which the injection end of the needle is covered by the injection end shield. The system also may incorporate a non-injection end shield that engages with the hub when a pen injector is unscrewed from the hub to lock out the non-injection end shield in the position protecting the non-injection end of the needle.