| 摘要 |
An improved mortise lock includes a case, a latch bolt including a tailpiece, and a retraction lever for retracting the latch bolt. The retraction lever includes a nose portion in engagement with the tailpiece to define a tailpiece contact point, a pivot portion pivotally mounted on a pivot in the case, and a mid-portion intermediate the nose and pivot portions. The mid-portion includes spaced apart side walls defining a yoke. Inside and outside operating hubs are mounted in the case for independent rotation and are aligned in coaxial relation. Each operating hub is rotatable in at least one direction toward a rotated position and is formed to include a hub camming surface. The mortise lock further includes a cam follower for riding on the hub camming surfaces during rotation of the hubs to cause the retraction lever to pivot and retract the latch bolt in response to rotation of either the inside or outside operating hub. The cam follower includes a roller and a shaft for rotatably supporting the roller in the yoke to engage the hub camming surface to define a floating hub contact point. The tailpiece and hub contact points cooperate to define an effective lever arm of substantially constant dimension therebetween irrespective of the direction of hub rotation.
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