Abstract: A child proof lock which has two parts. The first part is of strap-like construction, is attachable to a surface at one end, has a shaped aperture at the other, and has an elastic portion between the two ends. The second part is also attachable to a surface and includes a rotatably mounted toggle. The toggle is shaped so as to be able to pass through the aperture in the first part only when it has been correctly rotationally oriented. In use the first and second part of the child proof lock are attached to opposite sides of a door opening in a relationship whereby the first part must be expanded to allow the toggle to pass through the aperture. To lock the device the toggle on the second part is correctly rotationally oriented, the first part is expanded and the aperture passed over the toggle. When the first part retracts an abutment on the first part rotates the toggle thus locking the device.

Abstract: An air classifier comprising a rotatable open-ended drum disposed with its axis horizontal or substantially so, for receiving material to be classified, means for creating a stream of air through the drum, means for introducing material to be classified into the drum at or near the upstream end thereof, means in the drum for conveying materially axially of the drum during rotation thereof, the conveying means being in the form of helical vanes of mutually opposite hand arranged in an upstream part of the drum to convey "heavies" in counter-current to the stream of air through the drum and in a downstream part of the drum being arranged to convey "lights" in the direction of the air stream, the two helical vanes being separated by an annular member which projects radially inwards from the inner periphery of the drum.