A detachable needle assembly is provided with a needle shield supported for telescoping movement on the needle hub, with the sliding-fit surface on which the shield moves being separated by a majority of the cross-section of the hub from the feed passage through the hub, or with the shield being movable...http://www.google.de/patents/US5312347?utm_source=gb-gplus-sharePatent US5312347 - Hypodermic needle shield
