Improvements in or relating to apparatus for the detection of cracks

881,765. Flaw detection apparatus. GENERAL ELECTRIC CO. Ltd. Dec. 3, 1959 [Dec. 3, 1958], No. 39005/58. Class 40(3). An apparatus for the detection of cracks in the surfaces of glass bodies comprises means for holding the body stationary in an examining position, means for directing light on to a part of the surface whilst the body is so supported, detecting means including a photocell for receiving light from or through the surface, and means for moving at least part of the detecting means relative to the surface, the photocell output being used to operate indicating means if a crack is present in the surface. For the inspection of the necks of bottles, which may be mounted on a conveyer, a cage 6 is lowered over the bottle neck 15 and light from a lamp 10 directed via mirrors 12, 13, 14 on to the neck 15. A mirror 16, shown for convenience opposite to mirror 14 but in practice displaced by about 30 degrees from it, receives the reflected light and passes it to a photocell 20 which is shielded from light direct from lamp 10 by shield 22. By rotating, and if necessary lowering, the cage 6 with the mirrors and shield the whole of the bottle neck is inspected. The photocell output is used to control an indicator which may form part of a rejection device.