15 July, 2024

Eaton system delivers precise steering control to four-way sideloaders

28 November, 2019

Eaton has delivered a valve system to sideloader manufacturer Bulmor GmbH. By specifying Eaton CMA Advanced Mobile Valve with Independent Metering in its new series of four-way sideloader forklifts, the company is reported to have achieved far superior steering control over earlier systems.

For its latest four-way sideloader, which offers customised height and width to help maximise storage capacity, Bulmor sought an electrohydraulic mobile valve capable of overcoming a number of challenges. A key functional requirement was for precise control of the four independently steered drive wheels under various load conditions.

As well as safe and smooth load control, the four-way sideloader features a mast shift function that can sometimes suffer from an overrunning condition where load inertia takes over control. Along with this challenge, Bulmor also wanted to reduce energy consumption of the overall machine.

The answer arrived in the form of an Eaton seven-bank variable-inlet CMA090 valve, which is configured with Eaton’s Pro-FX Configure software plus a DPS2-12 differential pressure valve. Chosen for its product performance and flexibility, the advanced CMA mobile valve with independent metering offers a sophisticated technology platform that streamlines and simplifies everything from design and set-up to operation and optimisation.

“All four wheels must follow a given steering algorithm without any delay or variance, regardless of load conditions,” Bulmor’s Thomas Goesweiner explained. “Here, the CMA valve’s flow control is providing the best steering performance we’ve ever achieved.”

Single-acting cylinder reduces the number of valve banks

The CMA’s integral flow share feature with priority selection for the steering system also eliminates the need for a remote priority valve. In cases where the supply flow is less than that required by the sideloader, this feature ensures power on demand to the steering system. System architecture is further simplified as the single spool operation for the single-acting cylinder reduces the number of valve banks; two banks are effectively combined into one.

Actuator advantage

Eaton’s CMA valve also addresses the challenge of overrunning conditions, whereby the direction of the desired velocity is in the same direction as external forces that can cause loss of load control and unsafe operation, typically during downhill operation or vehicle braking. While most applications use various conventional valves to create the opposing hydraulic force, the CMA valve system applies a load differential calculation to determine if the direction of load is the same or opposite direction as the desired velocity. Through port pressures and the areas on each side of the actuator, CMA valves can assign the load differential to be either passive or overrunning. For the latter, the control applies a meter-out strategy and will hold constant pressure on the upstream port.

Regarding efficiency, the CMA valve system continuously monitors the flow balance at the inlet port of the valve set, along with the pressure and temperature of the oil. The valve then controls and modulates the pressure governed by the DPS2 regulator valve with varying logic, thereby reducing the flow margin applied to the sideloader‘s variable-speed pump. Additionally, as the power loss of a priority valve has been eliminated by the integral flow-share feature, CMA valves effectively reduce any wasted energy. The reduction of power losses allows a longer operating time or more load cycles with a single battery charge; the sideloader rarely has to go to the charging station. Furthermore, the lower power requirement reduces the thermal load on the electric drive of the hydraulic pump. This leads to lower operating temperatures of the electrical components; interruption due to high temperatures can be avoided, resulting in higher efficiency and productivity.

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