Strong-box lock tumbler system - has surfaces at ends of curved section against which key tongue first bears

摘要

The lock has a curved section in the keyhole against which the key bears during operation. At each end of the curved section (6) where it joins onto adjacent sections of the keyhole (4) faces (7) are formed, against which the key tongue first bears, irrespective of the shape of the steps (9a-d) on it. The faces can have a very small radius in relation to that of the curved section, and they can be undercut (8) where they join onto the keyhole corners (5). USE/ADVANTAGE - Strongbox-lock tumbler system in which the key shape cannot be deduced from the wear marks.