Solomon Henry - Lift up night latch with jointed key Patented 1779

Described in the specifications as " A loose bit with wards is joined to to the key, which bit falls when the key is inserted in the lock".

This lock is operated from the inside by a finger lift or knob, and from the outside by a jointed key, which has to be straight in order to enter the tubular keyhole.
Once the key is inserted into the lock it presses up against a spring loaded cover and the jointed portion (the key bit) turns at right angles and can now lift the latch bolt. The key automatically straightens up when withdrawn.