Abstract
Two types of novel electro-hydraulic floating disc type of switching valves have been investigated. Prototype valves of both types have been built and the basic mode of operation confirmed. Due to the complexity of a detailed description of the valve operation, a quasi-steady state computer model has been adopted which has allowed some of the valve characteristics to be adequately described and has given valuable insight into the operation of valves . The single-disc valve, while having the merit of simplicity, was found to have a significant steady power loss when using a 25mm diameter disc size. Due to this, its main application is thought to be as a miniature pilot or first stage valve, as it could be manufactured to less than half the present size. The double-disc valve, while being more complex, has the important advantages of no quiescent power loss and low sensitivity to particle contamination. It is envisaged that the valve could be made in a range of flow capacities, either as a single- or two-stage device with the 2-position, 3-way porting arrangement preferred for remotely controlled micro-processor applications. Steady-state load flow and pressure characteristics are presented and are shown to agree well with the theoretical model. Experimental switching tests on both valves have established that they can be switched continuously at 50Hz, at supply pressures of 100 bar, from nozzle-to-nozzle, but much higher frequencies can be used for pulse-width-modulation where there is no contact between the disc and the nozzle.