Basic requirements:
- Understand the composition and function of the main drive of the rolling mill.
- Understand the types of connecting shafts and couplings and the working principle of universal joints.
Coupling shaft and coupling joint
- The purpose of the coupling shaft is to transmit the motion and torque of the motor, reducer, and gear seat to the rollers; on the horizontal rolling mill, the transmission between the frames is also through the coupling shaft.
- Commonly used coupling shafts for rolling mills include plum blossom shafts, universal joints, and arc gear shafts.
- The coupling includes the main motor coupling (from the motor to the reducer) and the main coupling (from the reducer to the gear seat). The most widely used is the gear coupling, and the safety coupling is used for the rolling mill with flywheel to protect the motor.
Structure of the connecting shaft
Cardan shaft
- Slider type universal shaft
This universal joint has a flat head with a hole and a fork head without a groove in the radial bore. A round pin is used instead of a small square shaft. After the round pin passes through the fork head and the flat head, it is fixed with a nut. If the round pin is removed and pulled out, the flat head and the crescent-shaped slider can be removed from the fork head laterally.
- Cross shaft universal joint
Cross-axis universal joints are universal joints with (rolling) bearings. They are widely used in the automotive industry. In recent years, they have been widely used in steel pipe mills, strip mills, and vertical roller mills, and have a tendency to gradually replace slider-type universal joints.
Structure：
It consists of two forks connected to the cross shaft through bearings. The bearings can be rolling bearings or sliding bearings.
Advantages：
Compared with slider-type universal joints, its biggest advantages are low wear, high efficiency, large torque transmission, long life, and smooth transmission. Where possible, cross-axis universal joints should be used first. At present, cross-axis universal joints have been standardized (JB3241–83, etc.)
Arc gear shaft
Compared with the slider type universal joint shaft, the arc gear shaft has the following advantages:
- Because the angular velocity of the arc-shaped gear shaft is almost constant during the movement, and the radial clearance is very small, the transmission is stable, the impact and vibration are small, which is conducive to increasing the rolling speed and improving the product quality.
- High transmission efficiency.
- The meshing part of the gear teeth is easy to seal and lubricate, and the service life is long.
- Compact structure, light weight, easy to install and disassemble, easy to change rollers.
Balancing of coupling shafts
Commonly used connecting shaft balancing devices include three types: spring balancing, weight balancing and hydraulic balancing.
Spring balance device
The spring balance device has a simple structure, but the balancing force changes with the movement of the connecting shaft, which is suitable for the connecting shaft balance of profile and plate rolling mills. When the vertical movement of the connecting shaft is 50-100mm, the spring balance is usually used.
Weight balancing device
Hydraulic balancing device
Connecting shaft
Currently, the most widely used couplings in the main drive of rolling mills are gear couplings and nylon pin couplings.
