A pulley is a small wheel with a groove around the shaft and can be rotated around the axis.A simple machine consisting of a grooved groove that can rotate around a central shaft and a flexible rope that crosses the disk (rope, tape, steel rope, chain, etc.) is a simple machine that can revolve around the central axis, called a pulley.The pulley is the deformation of the lever, which belongs to the simple mechanism of the lever type.
The pulley group is a simple machine assembled by a number of dynamic pulleys and fixed pulleys. It can both save force and change the direction of force.The labor force of the pulley is determined by the number of ropes, and the mechanical efficiency is determined by the gravity of the pulled object, the gravity of the pulley and the friction.
The function of the pulley and pulley group
The pulley supports and guides the rope movement and plays the two roles of guiding and balancing.The pulley group is composed of a certain number of moving pulley and fixed pulley. It has the characteristics of both moving and fixed pulleys, and the pulley is divided into two kinds of pulleys and moving pulleys.The fixed pulley only changes the direction of the force.
A moving pulley can save power.Therefore, the pulley group can not only change the direction of the force, but also save the force.And it can be used as a deceleration or growth device.A larger pulley block should be used to reduce the pulling force of the wire rope when the weight is larger. When the weight is lighter, a smaller pulley block should be adopted to reduce the number of wire rope’s wear and improve the work efficiency.
The pulley group composed of wire rope, fixed pulley and movable pulley is an important part of crane lifting mechanism.According to the role of the pulley, it is divided into two kinds of force – saving pulley group and speed – speed pulley group.The pulley group is divided into two types: single joint pulley group and double pulley group.
Standard for pulley scrap
- With one of the following circumstances, the pulley should be scrapped.
- crack (no repair welding);
- The uneven wear of the wheel trough is 3mm;
- The wear of the thickness of the wall of the wheel is 20% of the original size.
- the reduction of the diameter of the bottom of the groove up to 50% of the diameter of the wire rope because of wear and tear.
- The other conforms to the discarded conditions.
Overhaul of pulley group
- single girder bridge crane and maintenance block, check for cracks;
- the repair of the pulley grooves;
- the inspection of the shaft hole;
- assembly;
- no crack in the pulley shaft, 30% of the original diameter of the neck, and no more than 5% coning, which should be replaced by this value.
- check the groove of the pulley with the sample plate, and the radial wear should not exceed 30% of the wall thickness. Otherwise, it should be scrapped.Shall not exceed the standards can repair, overhaul after using model checking, the bottom, and lateral clearance should be no more than 0.5mm, the deviation of the center line and the pulley wheel groove center line should be less than 0.2mm, the rope groove center deviation on the contour surface should be less than 1mm;
- after the overhaul of the single beam bridge type crane, the shaft hole is allowed to have a defect of not more than 0.25CM2, and the depth should not exceed 4mm.
- after assembly, the hand should be flexibly rotated with the hand, and the lateral swing should not exceed D/1000.The nominal diameter of the D- pulley.
