Buffer device and anti-collision device are used to absorb the kinetic energy when the crane or trolley hits the terminal board when the switch fails. Rubber, spring and hydraulic buffer are widely used in this device, and the hydraulic buffer is used on cranes or trolleys with high working speed (such as bridge-carrying trolleys), which can absorb large energy during impact. Some cranes are also equipped with photoelectric anti-collision devices to prevent two cranes running on the same track from colliding. Its simple principle (as shown in the figure) is that when two cranes are close to a certain safe distance, the light wave emitted by the transmitter of crane A is received by the receiver of crane B, and the photoelectric tube generates an electrical signal. After waveform shaping and amplification, relay action and buzzer alarm, the power supply of the operating mechanism is automatically cut off. Two cranes should be equipped with one set each and cooperate with each other.
Windproof device is a device to prevent the crane from being moved or blown down by strong wind, which mainly includes crane rail clamp and crane anchor. Large cranes operating in ports are usually equipped with rail clamps and anchors at the same time. When the crane stops or the wind increases to a certain extent, the rail clamp works; Before the storm, the anchor was operated by the driver. The windproof function of rail clamp is not as good as that of anchor.
The lifting weight limiter can make the weight of the hoisted weight not exceed the specified value, and there are two types: mechanical and electronic. Mechanically use the principle of spring lever; In electronic mode, the lifting weight is usually detected by the pressure sensor, and the lifting mechanism cannot be started when the allowable lifting weight is exceeded. The lift limiter can also be used as a lift indicator.
The lifting moment limiter can make the lifting moment (the product of the gravity and amplitude of the hoisted object) of the jib crane not exceed the specified value, and can receive the weight change signal and the amplitude change signal at the same time. These two signals are combined and amplified by electronic instruments, and then electrically interlocked with the lifting luffing mechanism to prevent the crane from overturning.
Large-span cranes with deflection limiters (generally more than 40 meters, such as carrier bridges and large portal cranes for shipbuilding) are prone to deflection when their running speeds are different on both sides, which will increase the running resistance and make the connecting structure between the bridge and the legs bear additional loads. At this time, the deflection limiter is usually installed on the upper part of the flexible leg. The relative rotation between the crane bridge and the supporting leg can make the cam or bump touch the control switch through the movement of the arm or gear pair. When the crane reaches a certain maximum deflection value (generally three thousandths to five thousandths of the crane span), it can cut off the power supply or automatically correct the deviation.