Hydraulics on the cutting edge

March 20, 1997
From farms to fairways, fluidpower systems are getting more efficient, economical, and easier-to-use

Whether supplying systems for backyard mowers or the largest agricultural tractors, fluid-power manufacturers are working harder than ever. That’s because customers want it all — quiet, efficient, reliable, and economical systems that are easy to assemble and use.

Hydraulic-system suppliers have responded to these wide-ranging demands in a number of innovative ways. Here’s a closer look.

More control
According to Dave Miller of Vickers, Troy, Mich., controllability is a major issue when it comes to large agricultural equipment. “Right now, in North America, we’re in the middle of a shift from hydromechanical, or manual, controls to electronics,” says Miller.

For example, a combine with manual controls means a nonstop workout for the operator, he says. That’s because cutter-head height and speed depend on the vehicle ground speed and which crop is being harvested. “He constantly has to adjust the height to cut material as close as possible without digging into the ground. It gets very tiresome, and a sloppy operator can pick up a lot of extra debris, move too fast and overrun material, or move too slow and have lousy overall productivity,” he says.

“Today, that’s all done electronically,” says Miller. Vickers supplies a complete package that coordinates the height and speed of the header with ground speed, reducing operator fatigue and enhancing productivity.

And today, he adds, most hydraulic controls are stand-alone systems. As an example of a next-generation system, he cites Vickers recently introduced EMV valve, a proportional, load-sensing control with integrated electronics. This system can integrate hydraulic controls with those of the engine and transmission, producing numerous benefits, says Miller.

For example, EMV’s ability to change valve control characteristics on the fly, as the harvesting conditions change, is more efficient than current systems. This technology may lead to smaller, more fuel-efficient engines than traditionally used in off-road equipment.

Electronics also allows Vickers to tailor the valve to each customer’s specific applications, even though the mechanical hardware remains essentially the same, producing manufacturing economies.

“You’re also going to see a lot of onboard, real time diagnostics. And that’s part of the productivity issue,” adds Miller. In the past, farmers traditionally waited until something broke before making repairs. “Today, we’re trying to give them the capability to foresee problems developing,” he says.

Higher efficiency
While manufacturers of smaller equipment typically take a different approach, customer demands are much the same. “Users are certainly looking for higher efficiency and ultimately lowers fuel costs,” says Mike Scott of Commercial Intertech’s Ultra Hydraulics Div., Columbus, Ohio. The company designs its Powermax gear pump line, found on equipment such as mowers and turfcare machines, with just that in mind, he says.

“We believe we have one of the highest efficiency products on the market,” says Scott. Key to high volumetric efficiencies, typically around 98%, is controlling gear-tip leakage, he says. The body-to-gear geometry is arranged such that during production test and run-in, the gears wipe barely perceptible tracks in the body. This results in virtually zero clearance between gear tips and body, producing a near perfect tip seal under normal operating conditions.

In addition, he says, Ultra configures standard products to exactly match customer specifications. For example, a pump may be rated for 4,000 psi. However, if the customer’s application only requires 2,500 psi, they optimize the unit for that pressure. Performing run-in at higher pressure would needlessly cut away more material, allowing additional leakage and lowering efficiency.

Another issue is manufacturing efficiency, which has a direct bearing on the cost of a machine. For example, the Ariens EZ Rider zero-turn mower is a consumer machine and pricing is critical. According to the company’s Jim Schuh, that’s a major reason Ariens opted for the right-angle hydrostatic transaxle from Eaton’s Hydraulics Div., Eden Prairie, Minn.

“Labor in installing hydraulic systems can be considerable,” he says. This unit increases production-line efficiency by combining a pump, motor, and axle in one compact envelope, says Schuh, eliminating the assembly time and plumbing required to install three separate components.

It also makes for a more-compact design, he adds. “Our machine isn’t any smaller because of it, but it frees up space.” This, he says, leads directly to more design flexibility, reduces the possibility of component wear, and makes maintenance easier.

According to Eaton officials, the transaxle is ideal for lawn and garden applications. A single control handles forward, reverse, and speed — no shifting is necessary. In addition to offering hydrostatic dynamic braking the transaxle features an integral wet brake for emergency stops or parking.

Durable designs
Other important issues today include liability and warranty costs, making component reliability essential. For example, says Gary Ellertson of Jacobsen, a steering-system failure not only causes machine downtime, it potentially raises serious product-liability issues.

That, he says, is why they use the HGF Hydraguide from Parker Hannifin’s Ross Div., Greeneville, Tenn., a hydrostatic steering unit designed for light construction and lawn-andgarden applications.

According to Ross engineers, the unit provides 20% more power than previous versions while maintaining the same frame size, and it features a lower pressure drop compared with competing steering systems. This equates to higher system efficiency and lower fuel consumption. Lower temperatures also lessen the need for a heat exchanger to cool the hydraulic fluid, and can extend system life.

The HGF also minimizes “play” or loose steering, so the driver has better control and is less fatigued at the end of the day. And by minimizing internal leakage, equipment holds its line and is less likely to drift when running across side hills.

The Vehicle Systems Div. of Commercial Intertech, Minneapolis, Minn., is also making life easier on vehicle operators with its 108 Series power unit. A Toro consumer mower, for instance, uses the miniature power unit to raise and lower the cutting deck.

“We automated a manual function, and turned it into a pushbutton operation,” explains Commercial’s Greg Reardon. Instead of pulling lever arms up and down, a toggle switch connected to the power unit controls positioning. This is an example of manufacturers looking to simplify their machines, he says. “And part of that plays into the fact there are a lot of women operators as well, and the decks get pretty heavy,” he adds.

The compact, self-contained unit includes an electric motor, gear pump, reservoir, internal valving, load-hold checks, and relief valves. The unit used by Toro, for example, has internal relief valves set at 1,000 psi up and 400 psi down. Integral load-holding checks in each direction hold the mower deck in position when the toggle switch is released.

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