Self-locking adjustable spanner - has fixed and moving arms, and slider forming knee joint with moving arm

摘要

The adjustable spanner with a fixed arm (1) and moving arm (13) includes a knee joint giving a locking action on e.g. a nut (E) screwed onto a bolt (B). Below the fixed jaw (3) is an adjustable jaw (5) mounted on a slider (8) which can travel along the fixed arm. The slider has a pin (12) at the bottom, acting as a hinge for the adjustable arm. Between the two arms is turnbuckle (15) which is adjusted to give the required grip on the nut, by matching its size. With the adjustable arm swung outwards, the jaws do not grip the nut. When the arm is moved inwards, and the spanner turned, the rounded end at the top of the arm rotates inside the slider against a curved recess under the adjustable jaw forming a knee joint with a locking action.