Control arrangement

A control arrangement for controlling the size of a gap between first and second components, the control arrangement comprising first magnet means to be provided on the first component, and second magnet means to be provided on the second component, the first and second magnet means being in magnetic interaction with each other across the gap, and the arrangement further including control means in operative association with the first magnet means to control the size of the gap, variations in magnetic flux or force across the gap cause the first magnet means to cause the control means to effect relative movement of the first and second components to vary the size of the gap, wherein the first magnet means is moveable in a first direction to cause the control means to effect relative movement of the first and second components to increase the gap and in a second direction to cause the control means to effect relative movement of the first and second components to increase the gap and in a second direction to cause the control means to effect relative movement of the first and second components to decrease the gap, the first and second magnet means being so arranged that relative movement of the first and second components towards each other moves the first magnet means in the first direction, and relative movement of the first and second components away from each other moves the first magnet means in the second direction.