Pressure controlled safety device for hydraulic lifting device - uses electromagnetically operated control valve in non-return valve to hold pressure while load is being lowered

摘要

The device is used for hydraulic shovels, and includes a pressure transducer in the hydraulic supply line to the working cylinder to actuate non-return in the case of reduced hydraulic pressure. The non-return valve has a control valve operated by an electromagnet. When the operators control lever is in the load lowering position a cam operates a switch which connects the electric supply to the contacts of the pressure transducer in the hydraulic supply line, so that the pressure transducer is effective only when the load is to be lowered. A controller directs the operation of the cylinder, and a hydraulic fluid reservoir is provided.