Here's a photo of an Italian snaphaunce with two sears.
The reason for two sears is that it evolved from the wheellock mechanism, and that's how it was done.
What I call "Sear 1" in the photo has a rounded nose so it will not stay engaged with the tumbler. The main spring will just pop it right out (this is analagous to the sear on the wheellock that goes through the plate and engages a rounded hole in the back of the wheel).
It can't pop out, however, because to do so the nose must move down, and it is pivoted on that screw in the box-looking thing behind it, which means that the other end of it must move up.
The arrow for "Sear 2" points to where a little raised hook on the back of Sear 1 engages Sear 2, which is hinged right down flush with the lock plate and sticks straight out toward the viewer in the photo. Sear 2 has to move back, allowing that little hook to move up.
The trigger is pivoted way up high in the lock, so when you pull the trigger it pushes horizontally back on Sear 2. This too is analogous to the wheellock, the only difference being that on the wheellock Sear 1 moves horizontally while this one moves vetically.
Another odd feature is that the tumbler stops by impacting the nose of the sear!. Clearly the cock should hit the top edge of the lockplate at the same time. On this lock it doesn't quite. I guess that's why they built that really sturdy box "bridle" to support the sear screw.
This sear mechanism came into use in the early 1600s, then the Italians brought it back in the 1700s to make these heavily carved fancy locks.
Let's see some more snaphaunce mechanisms!
The reason for two sears is that it evolved from the wheellock mechanism, and that's how it was done.
What I call "Sear 1" in the photo has a rounded nose so it will not stay engaged with the tumbler. The main spring will just pop it right out (this is analagous to the sear on the wheellock that goes through the plate and engages a rounded hole in the back of the wheel).
It can't pop out, however, because to do so the nose must move down, and it is pivoted on that screw in the box-looking thing behind it, which means that the other end of it must move up.
The arrow for "Sear 2" points to where a little raised hook on the back of Sear 1 engages Sear 2, which is hinged right down flush with the lock plate and sticks straight out toward the viewer in the photo. Sear 2 has to move back, allowing that little hook to move up.
The trigger is pivoted way up high in the lock, so when you pull the trigger it pushes horizontally back on Sear 2. This too is analogous to the wheellock, the only difference being that on the wheellock Sear 1 moves horizontally while this one moves vetically.
Another odd feature is that the tumbler stops by impacting the nose of the sear!. Clearly the cock should hit the top edge of the lockplate at the same time. On this lock it doesn't quite. I guess that's why they built that really sturdy box "bridle" to support the sear screw.
This sear mechanism came into use in the early 1600s, then the Italians brought it back in the 1700s to make these heavily carved fancy locks.
Let's see some more snaphaunce mechanisms!