A weight-case accumulator may be described as a vertical inverted hydraulic cylinder, whereby the piston rod is fixed and the cylinder is allowed to move vertically throughout its stroke. The cylinder body has an attachment that is filled with iron slag, or similar, to provide weight. The cylinder is charged via the hydraulic pump and, when full, operates a deflecting valve (not shown) to arrest further cylinder movement and deflect water from the pump (at no pressure) back to the supply tank.
The hydraulic control valve would be operated to enable force to be applied via the main rams onto the steel plate to be formed. The accumulator would descend as pressurised fluid was transferred to the main cylinders. Upon completion of the pressure stroke, the hydraulic control valve would be operated to reverse the main ram direction and high pressure fluid would be transferred via the drawback rams to return the main ram. The hydraulic pump would remain in operation throughout this time.
The capacity of the accumulator, measured in gallons of water, is the total annular volume of the cylinder. The available hydraulic pressure is the total weight/annular area, measured in pounds/sq. in. (or psi).
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