The main function of the pinch roller is to pinch the wire coming out of the water-cooling section and smoothly send it into the spinning machine. In order to meet the requirements of high-speed pinch, the design of pinch roller is constantly improved. The current mainstream design is integrated parallel transmission, horizontal cantilever pinch and pneumatic control pinch action. The pinch roller can use the waste tungsten carbide roller ring of the finishing mill, and is equipped with a clamping limit position adjustment device to prevent the two rollers from colliding. In order to meet the speed requirements of the reducing sizing machine, the highest design speed of the most advanced pinch roller in the world can reach 140m / s and the guaranteed working speed is 120m / s. When rolling wires of different specifications, the pinch rollers in front of the wire spinner play different roles:
(1) In the production of small-sized wire rod, the rolling speed is generally high. At this time, the rolling of high-speed wire rod from the finishing mill to the spinner will cause jitter due to the following reasons:
1) The cooling nozzle in the water tank sprays high-pressure water on the wire moving forward at high speed.
2) The straightness of the rolling center line installed by the unit is not good.
3) The impact caused when the wire enters the guide guide, conveying guide groove and wire feeding pipe interface of the unit.
4) Uneven pinch by pinch roller.
If this jitter is not eliminated, it will be extremely unfavorable to the smooth operation of the wire rod, make the loop of the wire reeling machine not good, affect the subsequent process, and may induce steel jamming, disordered wire and large wear of parts and components of the whole unit or the finishing rolling unit. In general, a pinch roller is set in front of the spinning machine to eliminate the jitter. The pinch roll uses two high-speed rotating roller rings to clamp the rolled material with appropriate clamping force, and the linear speed of the roller ring is higher than the linear speed of the last working frame of the finishing mill in a certain proportion, so that the rolled material between the pinch roll and the finishing mill is in a tension state with a certain amount of tension to eliminate jitter.
(2) In the production of large-sized wire rod, the rolling speed is generally low. At this time, after the end of large-sized wire rod is separated from the finishing mill, it is difficult to ensure that the original speed passes through the water cooling section and the guide groove by relying on its own inertia. Therefore, the pinch will pinch the tail of large-sized wire at this time to ensure that the rolled material enters the wire drawing machine at a constant speed.
The motors of the pinch bar and the spinning machine are arranged on one side of the rolling line, and both are driven by gears.
The pinch roller is composed of transmission gear, input shaft, intermediate shaft, roller shaft and bearing pedestal box. The pinch roller is driven in parallel by cylindrical gear to achieve single-stage or multi-stage speed increase. An intermediate gear drives the gears on the upper and lower shafts in the pinch roller gear box, so that the upper and lower rollers synchronously pinch the wire in the same direction. The pinch action of the roller is completed by pressing down the cylinder. The transmission gear is in the form of straight or helical cylindrical gear. The speed of the roller shaft of the pinch roller working at high speed can reach more than 10000r / min.
The pinch roller has two structures of single-stage and multi-stage transmission. No matter how many stages of speed increase, the high-speed shaft is supported by oil film bearing and subjected to radial force. The axial direction depends on two disc angular contact balls for bearing positioning. The pinch roller box with single-stage transmission is compact and simple in structure, but has poor heat dissipation and small space for disassembly and maintenance. The multi-stage transmission pinch roller box has complex structure and many lubrication points. However, the box structure is large and the heat dissipation effect is not affected.
