Abstract
Some direct-hydraulic presses have become very complicated owing to the introduction of servo-electric controls, embodying a mass of electrical gadgets, solenoids, micro-switches, etc. In this paper a new, completely hydraulic control system is described which entirely replaces the electrical controls, thereby bringing all maintenance problems within the scope of the hydraulic engineer. Also, with the elimination of electrical delays it is possible to ensure almost instantaneous valve action. The paper deals briefly with packingless piston valves, the avoidance of various forms of lock, and the problems involved in the design, construction and control of large hydraulic presses, the choice of the most advantageous working pressure, and the viscosity of the hydraulic oil.
A detailed description is given of a 1,000-ton direct-hydraulic forging and planishing press, powered by high-speed pumps totalling 665 pump horse-power and controlled by a single-lever, completely hydraulic, remote-control panel. This press makes reversal in
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