Thumb safety for exposed hammer firearms

A safety system for firearms of the type in which a hammer may be urged into a cocked position and may then be actuated by operation of a trigger to cause striking of a firing pin, said safety system comprising:

• a hammer pivotally mounted to cause striking of a firing pin, said hammer including a tip projecting therefrom;
• a thumb safety carried by and rotatably mounted with respect to said hammer, said thumb safety including a portion projecting from the hammer and having a surface thereon for engaging said tip projecting from said hammer, a surface for striking the firing pin, and a thumb pressure application surface, said thumb pressure application surface and said surface for engaging said tip of said hammer being aligned with said tip for engagement of said tip by said thumb safety upon rotation of the thumb safety to move said hammer into a selected half-cocked position and a firing position, and upon rotation of the thumb safety away from engagement with said tip to a safe position with the surface on the thumb safety for striking the firing pin out of alignment to engage said firing pin and said thumb safety in position to engage other structure and block engagement of the thumb safety with the firing pin;
• and
• means to semi-fix the position of the thumb safety with respect to the hammer in the firing position and in the safe position, said means comprising semi-spherical detents formed in the thumb safety and a spring-biased ball carried by the hammer and selectively biased into said detents.