| 摘要 |
A mortice latch which largely overcomes the problems of wear and breakdown in operation comprises a casing consisting of a top case (2) and a bottom case (1); a latch bolt assembly reciprocally mounted in the casing and comprising a bolt head (7), a bolt lathe (8) and a bolt end-stop (9); a latch bolt follower (23), pivotally mounted in the casing, and a return spring (33). The follower (23) has a first curved arm (25) provided at its end with an arcuate surface (26) which is engageable with the latch bolt end-stop (9) and a second curved arm (28) which is provided with a cylindrical socket (29). A roller (31) is freely pivotally mounted in the socket (29) and the return spring (33) is mounted on a shaft (32) which extends from the roller (31). The shaft (32) extends through an aperture in a strip (17) projecting from the bottom case (1) and one end of the spring (33), which takes the form of a coil spring, bears against the strip (17) while the other end of the spring bears against a stop (34) on the shaft (32). The engagement of the roller (31) in the socket (29) of the follower provides a ball and socket type action and is such that very little wear takes place and any that does is fully compensated. The latch bolt can still be operated even in the event of failure of the return spring (33). A dead bolt assembly may also be fitted to the mortice latch if desired.
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