The mine hoist is an important "throat" equipment of the mine, which is responsible for the lifting of minerals, the up and down of personnel, the transportation of materials and equipment. With the rapid development of my country's mining industry, new and higher requirements have been put forward for the safe, stable and reliable operation of mine hoists. As a key component of the mine hoist braking system, the work reliability of the brake is directly related to the safety performance of the mine hoist and affects the safe production of the mine. Once the brake breaks down, it will affect the production schedule in the slightest, and lead to the occurrence of vicious accidents.

Since my country independently produced the first mine hoist in 1958, many series of mine hoists have been produced in different years, and their technical level is also very different. With the continuous improvement and development of the technical level of mine hoists, many hoists with a long service life, especially hoist brakes, have become more and more backward in their technical level, with hydraulic cylinder oil leakage, insufficient braking torque, and loose brakes. Unsafe factors such as gate failure have brought hidden dangers to production and seriously threatened production safety.

The author starts with the analysis of the working principle and mechanism of the brake, combined with the actual experience of the brake reform in the work, and elaborates the typical method of the brake technical reform, in order to provide a reference for the reform of the old product of the hoist.

1 The working principle and structure of the brake

According to different working methods, there are mainly two types of brakes: disc brakes and radial block brakes.

1.1 Disc brake

1.1.1 Structure

The disc brake uses disc springs to generate braking force, which is released by hydraulic pressure. The braking torque is generated by pressing the brake shoes against the brake disc from both sides in the axial direction. In order to prevent additional deformation of the brake disc, the main shaft does not bear additional axial force, and the brakes are used in pairs. Disc brakes are divided into hydraulic cylinder front disc brakes and hydraulic cylinder rear disc brakes according to their structure.

(1) Front-mounted disc brake: The hydraulic cylinder is bolted to the integral cast steel bracket, and is fixed on the foundation with anchor bolts through the backing plate. The hydraulic cylinder is equipped with pistons, plungers, adjusting nuts, butterfly springs, etc. The cylinder can reciprocate in the support, and the brake shoes are fixed on the liner.

(2) Rear-mounted disc brake The hydraulic cylinder is composed of brake shoes, liner with cylinder, butterfly spring, hydraulic components, connecting bolts, rear cover, sealing ring and brake body. The hydraulic components are composed of retaining ring, skeleton rubber oil seal, Yx-shaped sealing ring, hydraulic cylinder, adjusting nut, piston and hydraulic cylinder cover. The hydraulic components can be removed and replaced individually.

1.1.2 The necessity of transformation

The "Coal Mine Safety Regulations" (hereinafter referred to as the "Regulations") stipulates: When calculating the braking torque, the friction factor of the brake wheels and brake shoes is generally 0.30～0.35; the braking torque generated by the braking device and the actual lifting maximum load rotation torque The ratio K must not be less than 3.

(1) Front-mounted disc brake The hydraulic chamber where the hydraulic oil is located is close to the front end of the brake. Once the oil leaks, it will easily contaminate the brake disc, reduce the friction factor between the brake shoe and the brake disc, and cannot meet the requirements of the Regulations.

(2) Rear-mounted disc brake It is small in size, light in weight, small inertia, fast in action, good in adjustable performance and high in reliability. It is currently the most popular type of brake used in hoists. However, rear-mounted brakes with a long service life often have the following problems: ①The disc spring is fatigued or broken after repeated stretching and compression, resulting in insufficient disc spring stiffness; ② Piston movement caused by aging of the piston seal and hydraulic oil pollution Increased resistance; ③Oil pollution or blockage of the oil circuit causes excessive residual pressure in the brake system. The above-mentioned problems will cause insufficient positive pressure output by the brake, so that the braking torque produced by it cannot meet the requirements of the Regulations.

Therefore, the front-mounted disc brakes and the rear-mounted disc brakes with long service life and poor braking performance must be modified in the braking system.