In the post on Linus Yale, we went searching for the origins of this brilliant system, which has more than 150 patented versions and dates back to the Ancient Egypt! Now, we’ll “enter” into this marvelously simple contraption that, with its extraordinary efficiency, has characterized the entire history of the key.
Looking inside the lock, we see that it’s divided in two parts: the movable coil, where the key is inserted, and the fixed cylinder which contains it. The two parts are connected by a series of pistons with different lengths, which flow two by two in seats equipped with springs on the top.
When the door is closed, the pistons are completely lowered by the springs and the upper ones lock the coil to the cylinder. By inserting the key, the pistons move up and down, as the keys of a player piano, pushed by the notched outline. When the key is fully inserted, the pistons are lifted in a position with the separation line between the upper ones and the lower ones corresponding with the margin between the coil and the cylinder. Only in this position the coil is free to rotate, making the latch slide to open the door. Easy, isn’t it? But it is even more so if you watch this wonderful animation, which shows the mechanical beauty of a perfect system.
The profile of a flat key resembles the shape of the mountains, with their peaks and elevations, maybe those of the Connecticut where Yale was born, or the image of the pyramids emerging from the sand dunes of Egypt, where the fortune of this magical system began.