Gersan Establishment

Timothy James Osgood

Martin Philip Gouch

David Antony Homer

Peter Armstrong Aked

Ian W Bowler

David William Beal

Stephen P Holloway

Robert W Ditchburn, Deceased

Ewan Howden Croucher

Nigel R Cook

Eric Jozef Blondeel

For blocking or polishing a natural or synthetic stone having a Mohs hardness greater than about 5, a blocking head has a body, a mounting member which can move vertically with respect to the body, and a rotary spindle driven by a motor. The mounting member is carried by a leaf spring whose position is altered by a parallel linkage whose arm is driven by a motor. In this way, the spring can for soft landing apply an upwards bias opposing the gravitational force of the mass of the mounting member. When the stone is in contact with the scaife, the deflection of the spring measures the force on the stone, and this deflection is detected by an LVDT. Subsequently, the spring can apply a downwards bias to augment the working force. A microprocessor is responsive to the output of the LVDT and controls the motor so that the force applied to the stone complies with a predetermined program.

Working a natural or synthetic hard stone such as a gemstone

In order to provide an accurate sort into many different classes, objects are dropped through a viewing zone and viewed in the same instant by a number of viewers. Each viewer provides electronic signals representative of three basic shape features, namely blockiness, symmetry and convex hull deviance, together with a total count of edge-breakthroughs. For each basic shape feature, the maximum, minimum and mean are obtained for all the viewers, except the minimum convex hull deviance signal. These signals, together with the edge-breakthrough count, are each subjected to a linear transformation to provide a normalized shape parameter which is then assigned a value of 0 to 15 for each class being sorted on the basis of the expected occurrence of that parameter in that class. Each pair of secondary shape parameters so determined is used to derive from a respective table a decision value. The shape class of the object is ascertained on the basis of a majority vote for all the shape decision values.

Shape sorting

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Basingstoke, United Kingdom

Timothy James Osgood