For connecting high pressures and flows, a safety valve includes a first main stage which, in a rest position, connects a fluid outlet to a first relief outlet and, in a switched position, connects a fluid inlet to a fluid connection for a second main stage. The second main stage, in a rest position, connects the fluid outlet to a second relief outlet and, in a switched position, connects the fluid connection to a fluid outlet. Both main stages are configured as seat valves having multipart tappets and, when the first main stage is connected, a first tappet part that is actuated counter to a spring load, in a first movement portion, initially sealingly abuts a second tappet part, as a result of which a relief passage to the first relief outlet is closed.

For connecting high pressures and flows, a safety valve includes a first main stage which, in a rest position, connects a fluid outlet to a first relief outlet and, in a switched position, connects a fluid inlet to a fluid connection for a second main stage. The second main stage, in a rest position, connects the fluid outlet to a second relief outlet and, in a switched position, connects the fluid connection to a fluid outlet. Both main stages are configured as seat valves having multipart tappets and, when the first main stage is connected, a first tappet part that is actuated counter to a spring load, in a first movement portion, initially sealingly abuts a second tappet part, as a result of which a relief passage to the first relief outlet is closed.

The lifting mechanism includes a battery, an electric machine, a hydraulic pump, an oil tank, a hydraulic cylinder, a work platform and a proportional valve or switch valve. In the energy-regeneration mode, the hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, thus in turn driving the electric machine to operate as a generator and charge the battery. In the present application, the hydraulic pump operates to increase a pressure in a hydraulic line between the hydraulic pump and the proportional valve or switch valve before the proportional valve or switch valve is switched from a unidirectional communication position to a bidirectional communication position. When the proportional valve or switch valve is switched from the unidirectional communication position to the bidirectional communication position, by increasing the pressure in the hydraulic line, it could be avoided that the volume of hydraulic fluid has low pressure is compressed because the hydraulic fluid has low pressure is communicated with hydraulic fluid has high pressure; therefore a state of sudden drop of the work platform is avoided, and safety performance and operating experience of the lifting mechanism is improved.

For connecting high pressures and flows, a safety valve includes a first main stage which, in a rest position, connects a fluid outlet to a first relief outlet and, in a switched position, connects a fluid inlet to a fluid connection for a second main stage. The second main stage, in a rest position, connects the fluid outlet to a second relief outlet and, in a switched position, connects the fluid connection to a fluid outlet. Both main stages are configured as seat valves having multipart tappets and, when the first main stage is connected, a first tappet part that is actuated counter to a spring load, in a first movement portion, initially sealingly abuts a second tappet part, as a result of which a relief passage to the first relief outlet is closed.

For connecting high pressures and flows, a safety valve includes a first main stage which, in a rest position, connects a fluid outlet to a first relief outlet and, in a switched position, connects a fluid inlet to a fluid connection for a second main stage. The second main stage, in a rest position, connects the fluid outlet to a second relief outlet and, in a switched position, connects the fluid connection to a fluid outlet. Both main stages are configured as seat valves having multipart tappets and, when the first main stage is connected, a first tappet part that is actuated counter to a spring load, in a first movement portion, initially sealingly abuts a second tappet part, as a result of which a relief passage to the first relief outlet is closed.

[Object] To make it possible to detect, with a single pressure sensor, a malfunction of two solenoid valves for switching flow paths and to quickly and reliably exhaust residual pressure in an air device through a solenoid valve. [Solution] A residual pressure exhaust air circuit 1 includes: a main flow path 9 through which air from an air source 2 is supplied to an air cylinder 100; an exhaust flow path 10 through which air in the air cylinder 100 is exhausted; a first sensor 8 for detecting a malfunction of solenoid valves 12, 13; a detection flow path 11 through which air from the air source 2 is supplied to the first sensor 8; and the two solenoid valves 12, 13 that switch communication states among the main flow path 9, the exhaust flow path 10, and the detection flow path 11. The two solenoid valves 12, 13 are formed of two-position valves having first positions 12a, 13a at the time of OFF and second positions 12b, 13b at the time of ON and are synchronously ON/OFF controlled. When the two solenoid valves 12, 13 do not operate in synchronization with each other, the air from the air source 2 is supplied to the first sensor 8 to detect a malfunction of the two solenoid valves 12, 13, and at the same time, the air in the air cylinder 100 is exhausted through the solenoid valve 12, 13.