DOPPEL-SICHERHEITSVENTIL

摘要

A double valve of the safety type for the control of equipment such as the clutch/brake of a press. The double valve comprises two four-way valves each having two supply and two working ports and an exhaust port. The valves are shiftable by fluid controlled means through a shuttle check valve. The arrangement is such that when either main valve is faulted, pressure will be removed from the clutch/brake motor and the fluid controlled shifting means will be disenabled due to the lack of synchronism between the main valves. This self monitoring function will prevent repressurization of the clutch/brake motor regardless of whether the unfaulted main valve continues to operate. The main valves are of the open center crossover type to prevent trapping of air at the working port for the clutch/brake motor in intermediate positions of the valves. The self monitoring function is accomplished by connecting both sides of the shuttle check valve, which supplies the fluid controlled shifting means, to exhaust whenever a discrepant main valve position exists, thus insuring that both main valves can no longer be simultaneously shifted to their open positions until the fault is cured. A lockout and reset valve is also shown between the outlet of the shuttle valve and the pilot valves, which further inhibits operation after the system is disenabled until there is a manual reset.