A roll-imprinting process is presented as a method of manufacturing valve rotors with high index-accuracy and uniquely featured metering edges. Such rotors enable a rotary valve to simulate the superior differential boost characteristics of the more expensive hydraulic reaction valves, particularly in respect of achieving a low differential boost rate in the on-centre region of valve operation, followed by a relative swift ‘turn-around’ to a region of linear boost increase over the remaining operating region of the valve. A slotting process is also presented which enables one-piece valve sleeves to be cheaply manufactured with a high degree of index accuracy.
