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SOLVING THE “telehandler problem”

  • Magazine Article
  • 20TOFHP02_04
Published February 01, 2020 by SAE International in United States
  • English

Two-stage overcenter valves create stability in machines with highly dynamic loads.

A common challenge engineers face in the application of counterbalance or overcenter valves is machines with a high degree of load dynamics. Vehicles with slender booms, multiple booms, wear pads with varying frictional forces or pneumatic tires are all subject to higher levels of load dynamics. Concrete pumps are a common example as they require multiple long, slender booms to deliver concrete to the work site. Rough-terrain forklifts or telescopic handlers with pneumatic tires are other examples.

In a telehandler, the long cylinder can act as a capacitor and store energy when fully extended. The pressure within the cylinder will rise to system pressure at the end of the stroke, and a counterbalance valve will reseat and lock system pressure in the cylinder irrespective of the load-induced pressure.