VG rope brake - complies with EN 81-A3
The VG rope brake can be operated in bidirectional mode. The brake is attached directly to the lift ropes and acts as an ‘overspeed protection means’ or ‘speed reducing element’ in the sense of Section 9.10 of EN 81-1 1998.
The VG rope brake combines the tried and tested technology of the “brake shoe” principle with the patented VG connection mechanism.
The brake shoe has two torsion springs, but is kept apart from the lift ropes by a DC electromagnet. The brake shoe is triggered by a speed regulator or a device for detecting uncontrolled movements. Using the VG rope brake in bidirectional mode meets all of the requirements in Clause 9.10 of DIN EN 81-1 1998, Clause 5.9.4 of BS DIN EN 81-80:2003 and Item 53 of the same standard related to significant dangers.
Further information directly from the manufacturer.
How it works:
When the brake tongue is triggered, the lift rope is clamped between the mobileand the fixed tongue. The subsequent movements of the lift rope ensure that the brake tongue kicks in fully and generates the braking force. The contact pressure on the rope is kept to a minimum to prevent damage to the lift ropes.
The brake includes a safety contract, which is incorporated into the safety circuit of the lift control system. The lift can only be put back into operation once the brake has been inspected and reset.
The brake is loosened or reset by manually raising the lift cabin and turning the installed handle. If the lift cabin cannot be raised manually, the brake tongue can be released by unscrewing the four external M12 x 25 hexagonal screws which hold the mobile tongue to the side panels of the structure. Tighten the bolts again after resetting the brake.
Installation of the VG rope brake:
The VG rope brake is installed with supports which make it possible to align the brake and make fine adjustments to it. It can be positioned parallel or at right angles to the lift ropes. The supports must be capable of withstanding the breaking force calculated by the application program with an appropriate safety buffer.
We recommend fitting the VG rope brake close to thesheave or the deflection pulley(s).
A bidirectional device can be fitted between the traction pulley and the deflection pulley as long as there is enough space between them. The minimum distance between the axle line of the pulley and the top of the rope brake tongue is 400 mm, with a maximum clearance of 1 mm. If the distance to the pulley is increased, the clearance can be increased to a maximum of 5 mm.
A bidirectional device can also be fitted on the caror the counterweight rope. Individual “downwards”brakes can also be fixed to the car and counterweight ropes (see illustration to the right).
The dimensions of the VG rope brake are determinedon the basis of a groove and friction formula in accordance with DIN EN 81 in order to calculate static and dynamic forces. The formulas are based on information about the rope speed and the groove profile of the brake tongues that grip the rope. Determining the necessary brake forces and therefore the right rope brake involves looking at a wide range of parameters. The parameters are used to define a suitable tongue shape and spring stack on a case by case base.
Dimensioning of the VG rope brake is achieved by means of a groove and friction formula according to EN81, in order to determine static and dynamic forces. The formulas are based on the cable speed and the groove profile of the gripping brake shoes.
In order to be able to determine the necessary braking forces and thus the correct rope brake, various parameters must be queried. According to the parameters, the appropriate jaw geometry and spring stack are individually defined.
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