电梯毕业设计外文翻译电梯安全.doc

ELEVATOR SAFETY: GIVE THE MINER A BRAKE
ABSTRACT
Over a five-year period, there were at least 18 documented cases of ascending elevators striking the overhead. In some cases, theaccidents resulted in serious injuries or fatalities. These accidents occurred on counter weighted elevators as a result of electrical,mechanical, and structural failures. Elevator cars are fitted withsafeties that grip the guide rails and stop a falling car; however,these devices do not provide protection in the upward direction.
Rules and regulations applying to elevator safety have come under review in response to these accidents. Some governing authoritieshave already revised their regulations to require ascending caroverspeed protection. This paper will discuss basic elevator design, hazards, regulations, and emergency braking systems designed toprovide ascending car overspeed protection. In addition, a case-studyreport on a pneumatic rope brake system installed and tested on a mineelevator will be discussed.
I NTRODUCT I ON
Elevators incorporate several safety features to prevent the carfrom crashing into the bottom of the shaft. Safeties installed on thecar can prevent this type of accident from occurring when the machine brake fails or the wire ropes suspending the car break. However, the inherent design of the safeties render them inoperative in the ascending direction.
In the upward direction, the machine brake is required to stop the cage Irvhen an emergency condition occurs. Under normal operation, the machine brake serves only as a parking braked to hold the cage at rest. However, when an emergency condition is detected, modern elevator control system designs rely solely on the machine brake to stop the car.
In the United States mining industry, the accident history has proven that this is not the best control strategy [2], [3]. These accidents occurred when the retarding effort of the drive motor was defeated when the mechanical brakes were inoperative. This allowed the