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1990 - Volume #14, Issue #4, Page #09
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Add on cushion valve protects hydraulic motors and cylinders

Bob Zimmerman, Oak Bluff, Manitoba, installs a 2-line Gresen cushion valve in front of hydraulic motors and cylinders to protect them from hydraulic motor failure caused by sudden shock loads.
"Original hydraulic systems usually work alright until something unusual happens, such as when you jam the cornbine reel on a clump of dirt," says Zimmerman. "Last year's short grain crop really caused some operators a lot of grief. Every time the reel stopped suddenly, the surge load instantly overloaded the hydraulic motor. The result often was a broken hydraulic motor."
Zimmerman says the Gresen valves are available at most hydraulic supply stores. He buys his out of an auto supply catalog. "'The valve shouldn't be set too much higher than your peak operating pressure, so if you're in doubt, just tee in a pressure gauge to check the normal operating pressure. You can order a valve preset at any pressure up to 3,500 psi."
The cushion valve is equipped with dual ball/spring relief valves, and the strength of the spring determines the re-lief point. Regular fittings are used to connect the valve into the feed lines. The two lines into the motor are connected to one side of the cushion valve, then two new short lines are used to connect the valve to the motor. There's no "in" or "out" side to the valve so it's a straight connection. The valve can be located in-line or mounted on the frame near the motor. "When the motor stops suddenly, the instant pressure peak in the `in' line will push the relief valve open, allowing oil to bypass to the other line," says Zimmerman. "There's no cavitation in the system - oil moves over to the other side without creating a void or open space with air bubbles. You can also buy a cushion valve with adjustable valves for extra fine tuning or to supply different relief pressures on the lines."
Zimmerman originally bought the cushion valve to control violent pressure surges in the hydraulic cylinder that swings combine-unloading augers in and out. "Farmers like the speed at which the auger swings out, but don't like the violent stop at the end of travel," says Zimmerman. "With a dual cushion valve `in' line mounted just ahead of the swing cylinder and set just above working pressure, the instant overload blows over to the other side of the cylinder. In this case, we're protecting the auger more than the cylinder. It's easy to install as you don't have to modify any parts of the main hydraulic system."
Contact: FARM SHOW Followup, Bob Zimmerman, P.O. Box 42, Oak Bluff, Manitoba, Canada ROG 1NO.
(Reprinted with permission from Grain News, Winnipeg, Canada).
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1990 - Volume #14, Issue #4