Clinging wet and sticky paper is no longer a problem for refuse collectors, thanks to the latest development by refuse collection vehicle makers Trio Engineering of Gloucester, centred around a two-speed hydraulic valve developed Hy-Pro.
Trio build special vehicles for collecting rubbish to be recycled which include a trough at waist level into which operative do a kerbside sort of the refuse. When the trough is full a hydraulic arm lifts and tips it so that the contents fall into separate hoppers.
The company has been building such vehicles since refuse classification for recycling began with a few pioneer councils 8-10 years ago. The design has been evolving ever since as requirements change and to improve performance. Hy-Pro, or Hydraulic Projects from Dawlish in Devon, has been involved since the start (indeed they have been supplying valves for Trio’s skip loaders for many years) and has developed bespoke valves for each new iteration of the design. In fact the valve controls all hydraulic functions, including the main tipper ram used to empty the vehicle at the recycling depot and the tail door.
One problem vehicle operators regularly experience is that sometime rubbish adheres to the trough, rather than falling into the hoppers during the lift and tip cycle. If not cleared this rubbish can build up and compromise efficiency, and even if this is not the case its continuing presence in the trough can be very demoralising to the collectors.
To ensure the trough empties completely it has become common practises to momentarily reverse the hydraulic drive several times when the arm is in the raised position, effectively shaking out the paper. Although this clears the blockage, it causes shock loads through the entire vehicle and hydraulic system.
Extensive tests at Trio have shown the vehicle and hydraulics to be amply robust to withstand this treatment indefinitely. However many councils have received alarmed complaints from residents and passers-by who find the rocking vehicle unnerving, so Trio decided to look for a solution.
“We looked at several options, such as coating the inside of the trough with Teflon and profiling it in such as way that paper could not stick,” recalls Colin Storey, Trio’s Chief Engineer, “but it was not long before we decided that the answer lay in the hydraulics. We called in Hy-Pro and asked if they could produce a two-speed valve.”
The idea was that if the ‘shaking’ could be done at half speed the shock loads would virtually disappear and the paper would still be dislodges just as effectively.
Hy-pro, were confident that they could produce the ideal design; they already produce many two-speed valves for other customers, so it was really only a matter of configuring known technology toy suit the particular situation. The solution they proposed was to adopt Hy-Pro solenoid valves using several elements from their V5-60 G1/2 sectional spool valve range, including a switchable two-speed valve.
The V5-60 solenoid valve is internally piloted and to overcome the harshness associated with standard direct acting solenoid valves a damping orifice is incorporated into the pilot line. This creates a smooth operation, but it also maintains a positive feel to the control system, allowing fingertip control for shaking the trough while eliminating judder within the system.
The V5-60 is rugged enough to be used in very arduous environments such as on automotive recovery vehicles, agriculture and refuse management, where the ability to mix solenoid and manual control is essential. Its flow rate is up to 60 litres per minute at 210 bar, yet it is compact and low profile.
“When you expect vehicle designs to evolve, as we did when recycling started, its always a good idea to go for compact valves. It’s a sure bet that extra requirements will eventually be put on the hydraulic system, so with a small valve you’re more likely to have room to accommodate the additional spools,” says Storey.