The hob is mainly composed of a cutter ring, a cutter body (set), a cutter shaft, a bearing, a floating seal, and an end cover.
1) Knife ring
In the middle hard rock formation shield method, the rock is crushed by the hob cutter ring, and the cutter ring is the key component of the hob. The cutter ring should have high mechanical strength, good wear resistance and impact toughness. .
Knife rings are generally divided into two categories: steel cutter rings and insert cutter rings. The steel cutter ring material is mostly alloy die steel or alloy structural steel. The insert cutter ring needs to be clamped with hard alloy, and the material is required to have good toughness and coordination. Therefore, high-strength alloy structural steel is often used.
The hob bearing is mainly tapered roller bearing. The bearing clearance, pre-tightening force and installation torque are different under different working conditions.
3) Floating seal
The purpose of the seal is to ensure that the lubricant in the cavity of the hob does not leak and prevent foreign matter from entering. The sealing effect is very important to ensure the normal operation of the hob and prolong the working life. The floating seal consists of two meshed metal sealing rings and two elastic composite rubber sealing rings for good sealing.
The metal sealing ring is the main part in the sealing device, and its structure and quality determine the sealing performance. The metal sealing ring is made of high hardness and wear resistant high chromium molybdenum cast iron material, and the "O type" sealing ring is made of NBR.
4) Body and spindle
The cutter body of the hob supports the main shaft and has certain strength and toughness. The material is usually made of medium carbon alloy structural steel.