1 resulting in the construction of the lift cage falling accidents mainly due to
Construction of the lift cage causes a lot of accidents fall, summed up in the following categories:
Brake torque (1) driving means is not enough, the safety factor is too small;
(2) single drive and dual (multiple) drive problems;
(3) Anti-fall safety device reliability is poor;
(4) violation of the deduction for the procedures, do not follow the product instructions, cage overload operation;
(5) drives the pinion gear meshing with the rack at the back is not installed by the wheel, or by wheel lock-piece eccentric shaft;
(6) is not set counterweight;
(7) Other accidental causes;
Analysis and comparison of the second drive means safety devices
2.1 hoists brake drive device
The brake is set cage floors were docked device, currently used are basically two: one is the standard JWZ200 type of block brake, braking torque of 160N · m, belong to a mature product, its disadvantage is that shape large size, brake wear, such as repair and maintenance of improper likely to fail. This brake is used on most of the 1980s domestic production of construction hoist, now rarely used, will be phased out; the other is the late '80s reference ALIMAK import prototype development, which is linked with the drive motor chip friction brake. It is linked with the drive motor pull type friction brake. Characteristic of this brake is compact, small size, the gap between the brake pads easily adjusted. Currently domestic construction lift its present are using this brake.
For cage securely docked on the hunchback layer to ensure it does not fall, brake system must have adequate braking torque, for without counterweight cage braking torque shall meet the requirements of the following formula:
Cage on line: M1 = (((G + Q) · R) / i) · k cage downward when: M2 = (((G + Q + Q1) · R) / i) · k
Where: M1-- cage on line braking torque (N · m); M2-- cage downward braking torque when the (N · m); Q-- hoists rated load (kg); Q1-- cage downward inertial force when the (N); G-- hoists weight (kg); i-- reducer transmission ratio, planar double enveloping hourglass worm, the worm reducer, i = 42 / 3; k-- braking torque safety factor, according to the provisions of GB / T10054-96 of k> = 1.75; R-- drive pinion pitch circle radius (m).
Cage at rated load (without counterweight, rated load of 1000kg), to securely docked in the desired location, to ensure that cage did not fall by the calculated braking torque M of 195N · m.
This shows that the two brake braking torque are small, in order to overcome the brake braking torque and ensure the safe operation of small cage without falling, be sure to use dual-drive or counterweight.
2.2 drive (single drive and multi-drive)
Setting the number of the drive, depending on the size of the weight of the cage and the rated load. Early on, the construction of the lift cage falling accident occurred several cases, it is considered unreliable single drive, only the use of dual-drive cage in order to ensure safe operation. In fact the problem is not the safe operation of the cage by a number of groups drive unit to decide.
2.3 Anti-fall safety device
When the drive cage failure and fall, limiting the running speed of the cage and allowed to stop the fall of a mechanical device called anti-fall safety device. At present most of the domestic use of generic ALIMAK construction elevator company's second-generation product - tapered drum friction type anti-fall safety device. Its role is to process the cage when running at rated speed, anti-fall safety device pinion shaft on the rail frame rack in follow state; when the cage for some reason overspeed operation, mounted on the gear shaft pellet on centrifugal force to overcome the spring force outwardly thrown inside the outer cone teeth engage friction cone friction drive rotates, the role of the butterfly spring group increases within, friction drag torque between the outer cone, to the degree that the cage stopped running. Braking slip cage stroke 0.25-1.2m, so smooth braking, no significant impact, extended stay hoists, steel and other life.
The anti-fall safety device is characterized by a brake torque, up to 3000N · m or more; compact structure, small size, relatively safe and reliable. It is currently supporting the main products on the domestic construction elevator.
According JG5058-95 "construction elevator # anti-fall safety device" provisions, anti-fall safety device can only be used within the valid calibration period, the effective calibration period of two years. Cause anti-falling safety device failure often excessive use of fixed term, not sent to the professional testing unit for repairs and testing in a timely manner, some wearing parts due to long use and wear, fatigue and other factors make the anti-fall safety device ineffective.
Over the years the repair and testing recalibration deadline anti-fall safety device view, there are some anti-dropping security housing water, so that the brake band long been immersed in water and rotten; and brake band surface sticky oil, these are greatly reduced coefficient of friction brake with a direct impact on the braking torque, it loses anti-fall function.
2.4 does not operate correctly
Violation of rules, do not overload the use of prescribed product brochures, causing the cage falling accidents. At present most of the domestic construction elevator cage overload not set limits protector. Related to this side of the central design principle of the papers had been reported in the journal, but really applied to the product quality clearance minimal. There are specially designed for future research institutes and factories collaboration, conduct research, so that the cage overload protection limits apply to the construction of the lift as soon as possible.
Round of questions by 2.5 drive pinion meshing with the rack at
Drive pinion with the rack rail rack meshing, known from the forces, in addition to the upward or downward vertical force, as well as the level of mutual repulsive force, that is to say away from the drive pinion rack force. Drive unit earlier production, generally not provided near devices. Since the drive plate rigidity and pinion deformation and improper meshing other reasons, led the drive pinion out of engagement with the rack surface causes the cage fall. A construction elevator on the Shanghai Baoshan Iron and Steel in 1993 is due to the use of the site on the trench reason the cage fall, causing dead and another injured in a major accident.
In addition, some Although equipped by round, but not by the eccentric shaft wheel locking plate, in the course of an eccentric axis automatic relocation so by wheel achieve its proper role.
2.6 counterweight problem
The purpose is to use the counterweight to balance the cage of some or all of the weight, the drive motor power under the same circumstances, can increase the carrying capacity of hoists, which play a major role in energy conservation. However, due to the construction of the lift cage falling accident about 90 percent are in Canada section or without counterweight situation occur, so some people come counterweight to ensure the safe operation of hoists conclusions. In fact, from the operating principle of rack and pinion lift construction, the counterweight can only play a role in saving energy. From domestic and foreign production drop machine construction program, the counterweight and without counterweight there, but without heat treatment of the role of construction elevator balance even more.
3 Make sure the key issues of construction of the safe operation of the lift cage
(1) To ensure the quality of device drivers brake and improve braking torque. Currently brake friction braking torque piece used generally in about 100N · m, braking torque is small, it needs to be further enhanced braking torque, brake torque safety factor k> = 2.
(2) currently use the vast majority of construction hoist friction cone type anti-fall safety device. From the use of the situation, more stable performance, is a relatively safe and reliable anti-fall safety device. But the problem is in the course must follow JG5058-95 requirements. Anti-fall safety device when in use. At least once every three months drop test rated load. To verify the reliability of the anti-fall safety device. In addition, anti-falling safety device can only be used within the valid calibration period. It must be sent promptly after the expiration of the professional testing unit for maintenance and testing, re-calibrated before use after expiration date. At the same time to strengthen in the course of maintenance, especially in the housing to prevent water seepage and brake belt sticky oil, in order to ensure its reliability and in enough braking torque.
(3) To install the cage overload protection device to ensure the safe operation of hoists. As mentioned earlier, the current limit cage overload protection device used on small, especially the installation of such safety devices on domestic construction hoist is less. We look forward to develop a simple, practical, safe and reliable cage overload protector to promote the use restrictions.
(4) drive pinion meshing with the rack at the back of the rack must be installed by the wheel. To ensure that the drive pinion meshing with the rack by the right. At the same time by an eccentric shaft wheel industry to use the locking plate firmly secured.