Method and apparatus for detecting overload distortion

1. A method for detecting overload distortion in lifting gear comprising:

(i) providing a hook which is susceptible to overload distortion;

(ii) providing said hook with three reference points at locations thereon defining, in an undistorted state of said hook, an isosceles or equilateral triangle; and

(iii) comparing the dimensions of two sides of said isosceles or equilateral triangle, one of which includes the dimension of said hook which is the more liable to dimensional increase in the case of overload distortion, after subjecting said hook to possible overloading.

2. A method according to claim 1 wherein the step of comparing the dimensions of two sides of said isosceles or equilateral triangle is performed by applying a piece of string or thread across pairs of said reference points defining said isosceles or equilateral triangle.

3. A hook which is susceptible to overload distortion; said hook comprising two reference points thereon defining, in the undistorted state of said hook, a reference length in a portion of said hook which is liable to dimensional increase in the case of overload; said reference length being comparable with known length data after subjecting said hook to possible overloading, in order to determine whether overload distortion has occurred; and said hook comprising, in addition to said two reference points defining said reference length, at least one further reference point that at least partially defines said known length data, said further reference point being provided on said hook and conveniently accessible for reference purposes.

4. A hook according to claim 3 wherein said reference points defining said reference length and said known length data comprises three such points disposed at the corners of an isosceles triangle.

5. A hook according to claim 4 wherein said reference points are disposed at the corners of an equilateral triangle.

6. A hook according to claim 3 wherein said reference points are provided in the form of upstanding projections that extend from a surface of the hook and are formed integrally therewith, the upstanding projections having side surfaces adapted for engagement with blades of an adjustable tool that is adapted to be rapidly adjusted to the dimension of said reference length and for rapid disengagement therefrom and re-engagement with the reference points defining said known data for detection of any difference in dimension.

7. A lifting device comprising:

at least one attachment device for attaching the device to a fixture;

at least one suspension device for suspending from the at least one attachment device; and

at least one hook according to claim 3 .

8. A hook according to claim 3 wherein said reference length is measured between said two reference points and wherein said known length data is measured between a first of said two reference points and said further reference point.

9. A hook according to claim 3 wherein the hook comprises a lifting boss configured to couple the hook to lifting gear, the hook comprising a longitudinal axis that intersects a first of said two reference points and said lifting boss, and wherein a second of said two reference points is located on a first side of said longitudinal axis and said further reference point is located on a second side of said longitudinal axis.

10. The hook according to claim 3 wherein said two reference points and said further reference point are located at corners of an isosceles triangle, and wherein said reference length is a measurement of a first side of said isosceles triangle and said known length data is a measurement of a second side of said isosceles triangle.