Disclosed is a silent mortise lock. The silent mortise lock comprises a fixing plate and an upper cover plate. The side edge of the fixing plate is provided with a stopping plate with a spring bolt hole; the inside of the fixing plate is provided with an inclined spring bolt limit rack, an inclined spring bolt stopping plate, a lock
rudder, an inclined spring bolt, a square spring bolt and an
interlock rod, wherein the inclined spring bolt, the square spring bolt and the
interlock rod are in linkage with the lock
rudder; the
tail end of the inclined spring bolt is provided with a slide bar, which can slide on the inclined spring bolt limit rack and the inclined spring bolt stopping plate in a penetrating mode, and the slide bar between the inclined spring bolt and the inclined spring bolt stopping plate is provided with a front pushing spring which keeps the inclined spring bolt in a spring-out state all the time. The silent mortise lock is characterized in that the
tail end of the slide bar is provided with an upper limit sheet and a
lower limit sheet; a poke rod fixed onto the lock
rudder is arranged between two limit rods; the lock rudder is provided with a buffering
hydraulic cylinder for buffer the rotating speed of the lock rudder. The silent mortise lock has the advantages of, by buffering the rotating speed of the lock rudder through the buffering
hydraulic cylinder on the lock rudder, avoiding the
impact noise due to rapid rebound and reset of a door opening
handle and the inclined spring bolt, and meanwhile, being noiseless, reducing wearing, prolonging the service life and the like.