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Review
Living in a modern city, each of us is inseparable from elevators in our daily lives. The invention of the elevator can be traced back to ancient Greece in the 3rd century, when people used simple ropes and pulleys to lift people and things. In 1852, the American Otis invented the world's first modern elevator that relied on steam power to lift and lift.
Since the birth of elevators, their own safety has been a concern. It is said that when the elevator suddenly loses control and falls rapidly, as long as it jumps on the spot in the moment before landing, it can slow down the impact and save your life, but is this really the case?
Elevator safety devices
After the invention of the modern elevator, safety has been significantly improved after hundreds of years of continuous improvement. Modern people come into contact with elevators, and a complete safety system has been established to deal with most emergencies.
The first is the speed limiter, which can monitor the operating speed of the elevator car at all times. When the running speed of the car exceeds 115% of the rated normal speed of the elevator, the device will be triggered, and a signal will be sent to cut off the power of the elevator, and the brake will be emergency braked at the same time, forcing the car to slow down and stop.
When the speed limiter fails and the brake cannot be made, the safety gear of the elevator will be opened, and the safety gear will be mechanically braked to firmly fix the car on the elevator rail.
When there is an extreme situation, the car falls or rushes to the top,
will trigger. The shock absorber and spring device, like a car's airbag, converts the impact potential energy of the car into elastic potential energy, thereby slowing down the car and achieving smooth braking.
Speed limiter, safety gear, buffer and other protective devices together form the safety circuit of the elevator. The safety loop will monitor the operating status of the position of the car, and when the car goes up and down, the electrical signal will be transmitted to the elevator control system, and the control system will feedback the corresponding signal to keep the elevator running.
In the event of an emergency, the safety device is triggered to achieve safe braking. In addition, there are many devices and sensors in the elevator system, such as overload protection devices, which prevent the elevator doors from closing to ensure safety when the elevator is overloaded, and door locking devices, which prevent the car from starting to operate when the elevator doors are not closed.
Elevator fall experiment
Although the modern elevator system has complete safety protection, there are still many elevator accidents every year due to mechanical failures, illegal operation and negligent maintenance.
It is said that if the elevator falls rapidly, it can slow down the impact and save your life by jumping up quickly before the elevator hits the ground. Regarding this rumor, an American popular science program "Rumor Buster" has done relevant experiments.
The program team found an abandoned elevator in a hotel to simulate the whole experiment, all the protective devices on the elevator were removed, and a quick release device was also installed on the steel cable.
The program team found a dummy to act as an experimenter, and judged whether the human body could withstand the impact of the elevator fall through the sensor data on the dummy at the time of the fall.
The program team installed a sensor on one member's leg to make the member jump multiple times. Through the measurement, the average take-off speed of a person is about 2.5 m/s. Next, the program team made a spring take-off device on the dummy, which can drive the dummy to jump at a speed of 3.8 meters per second.
After everything is ready, the program team puts the dummy into the elevator, and the jumping device on the dummy is connected to the rope at the top of the elevator, and when the elevator falls to 1.8 meters above the ground, the jumping device will be activated.
As the latch was pulled out, the entire elevator fell from the 28-metre-high roof, and the dummy jumping mechanism was successfully activated. Afterwards, the program team opened the elevator and found that the entire dummy had been torn apart, and it was obvious that it was impossible for people to survive in this situation.
The program team measured that the speed of the elevator reached 23 m/s when it fell, and the take-off speed of the dummy in the elevator was 0.9 m/s. Obviously, the speed of the dummy cannot counteract the impact of an elevator fall, and it is not feasible for ordinary people to save their lives by jumping.
Moreover, when the elevator falls rapidly, it will be in a relatively static state with people, forming a short period of "weightlessness", in this case, it is difficult for people to complete the jump by borrowing force.
The right response
Since jumping to save our lives is the wrong thing to do, how do we deal with dangerous situations when we take the elevator?
When taking the elevator, you must choose the elevator equipment with perfect equipment and maintenance to avoid taking the elevator that is in disrepair and aging equipment.
The elevators with qualified devices are equipped with perfect safety protection devices, and generally rarely falls, and more failures are that the elevator stops running and passengers are trapped in it.
When you encounter trapped elevators, you must stay calm and avoid excessive behavior, such as forcibly tearing down the door and jumping around. You should press the elevator alarm bell in time, or contact the staff by phone and wait for rescue.
When calling for help is fruitless and you cannot contact the outside world, you should conserve your physical strength, avoid shouting, and intermittently slap the elevator door or wall with your hands or soles to make a noise and wait for rescue.
When all the safety devices of the elevator fail and it is inevitable to fall rapidly, the best way to deal with it is to face the elevator door, with the back of the head against the wall, in a straight line, the legs in a bent position, and the hands firmly grasp the elevator handrail. If you don't have armrests, you should hold your head and neck with your hands to minimize the impact on your body.
end
In general, a qualified elevator is very safe, and the internal protection device can cope with a variety of sudden dangerous situations. Even if there is an extreme situation of the elevator falling, the elevator does not guarantee its own safety when it lands and jumps, and it is the right way to adopt a more scientific self-rescue posture.
We should also pay more attention when taking the elevator and use the elevator in accordance with safety regulations, so as to minimize the probability of danger.
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