Safety lock for hydraulically operated pressure die casting machines - where dies cannot be closed if safety grid is open

摘要

The machine has a moving die opened or closed by a work cylinder fed with a pressurised hydraulic fluid by a pipe connected to a main control valve. In the pipe is a 2/2 way valve (5) eg. a cartridge valve, which is operated by a 3/2 way pilot valve (6). If the safety grid employed on the machine is opened, an electric circuit triggers valve (6) to actuate valve (5) so the dies cannot be closed while the safety grid is open. Safty regulations stipulate than a independent valve must be used to stop the flow of hydraulic fluid closing the dies when the safety grid is open, i.e. to prevent accidents to human workers such as the crushing of a human hand between the dies. The invention provides a simple safety device made form conventional components.