| The NG 40 hydraulic overload safety device (double point version shown) prevents damage by quickly diverting hydraulic pressure from the main press cylinder when an overload occurs. |
Presses are probably the earliest application of industrial hydraulics. According to Fluid Power — The Hidden Giant, by John J. Pippenger, P. E., the first known patent for a hydraulic press was granted on April 30, 1795 to Joseph Brahmah. Once the power of hydraulics was harnessed for industrial production, undoubtedly, safety concerns would have quickly followed.
Today’s presses benefit from 200 years of safety development, not only to protect people, but to protect work pieces and the machines themselves. Producers and operators of mechanical presses require reliable machines that avoid injury and damage in case of overload. A cost-saving solution with high operating reliability that doesn’t compromise speed of the press is offered by Voith Turbo GmbH & Co., Crailsheim, Germany.
The key to Voith Turbo’s hydraulic overload safety device is its extremely short reaction time. It is used for hydraulic pre-stressing of the main press cylinder and is normally positioned between press’s connecting rod and press ram. In case of overload, pressure is diverted from the cylinder, thereby causing the press to abort the stroke without damage.
The working pressure of the hydraulic cylinder is quickly transmitted into a central overload valve by integrating a pilot valve into the device. Short reaction times and reproducible behavior with varying numbers of strokes and force characteristics are the result.
The system is hermetically sealed, and features adjustable press force with minimal pressure peaks. The hydraulic overload safety device is available in NG 16, NG 25, NG 40, and NG 63 sizes and can be applied in presses with one or two connecting rods.