Patent ID: 6860018

Claim:
Pruning shears comprised of: first and second crossed pivoted limbs which carry respective cooperating cutting elements at the front ends thereof, and which extend rearwardly to form hand grips for operating the shears; a spring that cooperates with the limbs to apply a force tending to open the shears; and a locking device, the locking device comprising: a manually operable slide button; a tumbler which is pivotally mounted on the first limb, and which is coupled to be moved by the slide button in a first direction to lock the shears in a closed position against the force of the spring with substantially no gap between the cutting elements, and in a second direction to a released position at which the shears may be manually opened and closed; a first cam surface on the tumbler; and a second cam surface on the second limb that interacts pivotally with the first cam surface with no translational motion, the first and second cam surfaces being so shaped and located that, when the shears are locked in the closed position, the tumbler is prevented from moving in the second direction, thereby to provide self-locking, at least one of the cam surfaces being shaped and dimensioned to allow the tumbler to move far enough in the first direction to lock the shears in the closed position, and to maintain self locking, independent of wear, adjustment or manufacturing tolerance in the shears.