Patent ID: 8347668

Claim:
A differential linkage attachment for handles of a door, the differential linkage attachment comprising a latch bolt biased by a biased driving mechanism to extend out of a door, a dead bolt having a cam slot, a first latch bolt shifting plate, a dead bolt shifting block cooperating with the cam slot of the dead bolt to move the dead bolt in and out, a second latch bolt shifting plate, a first handle ring, and a second handle ring, the first handle ring and the second handle ring being independently set to cooperate with the dead bolt shifting block, a sector convex end of the second handle ring being encircled by and rotatable between opposite ends of a passageway defined in the first latch bolt shifting plate and a sector convex end of the first handle ring being encircled by and rotatable between opposite ends of a passageway defined in the second latch bolt shifting plate, a pulling arm of the first latch bolt shifting plate and a pulling arm of the second latch bolt shifting plate engaging the biased driving mechanism of the latch bolt to retract the latch bolt upon movement of one of the first latch bolt shifting plate and the second latch bolt shifting plate, the first latch bolt shifting plate, the second latch bolt shifting plate, the dead bolt shifting block, the first handle ring and the second handle ring all being rotatable around a common center axis, wherein when the second handle ring moves forward, one of the dead bolt shifting block and the first latch bolt shifting plate is linked to turn around on the center axis, and when the second handle ring moves backward, only the dead bolt shifting block is linked so that the dead bolt extends out to lock the door, and when the first handle ring moves forward, one of the dead bolt shifting block and the second slant bolt shifting plate is linked to turn around on the center axis, and when the first handle ring moves backward, only the dead bolt shifting block is linked so that the dead bolt extends out to lock the door.