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Running the Plows
Parker Chelsea has combined a single PTO and accumulator to replace multiple hydraulic systems
Joseph Ogando, Senior Editor -- Design News, September 21, 2008
HYDRAULIC SYSTEMS & CONTROLSSTORED ENERGY MANAGEMENT SYSTEM,
PARKER HANNIFIN CORP., CHELSEA PRODUCTS DIV.
Snow plow trucks usually have a lot going on from a hydraulics standpoint. Not only is there the heavy plow itself to move but also hydraulically actuated dump beds and spreader augers in the back of the truck. In fact, these trucks have hydraulic demands that traditionally called for two separate hydraulic systems — an underhood clutch pump to run the plow and another power plant for the back-of-the-truck functions.
A new solution from Parker Hannifin's Chelsea Products Div., for the first time, makes it possible to use a simple centralized power plant that can run all the hydraulic functions at once. The use of a centralized system eliminates what are ordinarily difficult packaging and hose-routing headaches.
Parker Chelsea's patent-pending Stored Energy Management System (SEMS) for Class 3, 4 and 5 snow plow trucks performs all the truck functions with a PTO-driven, 2,000-psi centralized hydraulic power plant. “Conventional solutions couldn't handle all the hydraulic functions. They just couldn't get all the flow they needed for simultaneous operations of the plow, spreader and dump bed,” says Mark Bordwell, a project engineer on the SEMS team.
SEMS, however, makes one centralized hydraulic system possible thanks to a combination of innovation. One is the use of the PTO itself, which integrates easily and efficiently with truck transmissions. “They're designed to work with truck transmissions, not an afterthought,” says Bordwell. Clutch pumps, by contrast, had to find a home under the hood and their capabilities were dependent on a properly adjusted, well-maintained serpentine belt.
One thing that potentially weighed against using a PTO was the loss of flow whenever the truck's transmission isn't running. So Parker Chelsea added a 4l, piston spring accumulator to maintain flow when the transmission stops. That's another industry first, according to Bordwell.
Another innovation in the system is a shuttle valve that allows the system to parcel out the hydraulic flow to the various functions around the truck. The valve takes its cues from load sensors on the various hydraulic functions with a controller determining how much flow each function needs at a given time. Bottom line is that the shuttle valve makes it possible for the 2,000 psi system to run the plow, spreader and dump bed simultaneously. “They may slow down a bit under some conditions, but they will all run,” says Bordwell.
