Overview
Modern fully mechanized longwall mining faces mostly adopt drum shearers for coal extraction. The domestically produced MLS₃—170 shearer serves as a representative example of such equipment, incorporating advanced mechanical transmission systems to ensure efficient operation in challenging mining environments.
Equipped with cutting teeth mounted on the spiral blades of its cutting drum, the MLS₃—170 shearer efficiently cuts coal as the drum rotates within the coal wall. The cut coal is then loaded into the chute of the face scraper conveyor for removal. This integration of cutting and loading operations demonstrates the sophisticated mechanical transmission design that enables seamless material handling.
The shearer rides on the conveyor's side, utilizing a tensioned traction anchor chain running the full length of the face. This chain engages with the traction sprocket of the shearer's traction unit, and as the sprocket rotates, it pulls the shearer back and forth along the coal wall for continuous mining operations.
Structural Components
Cutting Drum (1)
Equipped with cutting teeth on spiral blades for coal extraction, featuring robust mechanical transmission connections to ensure efficient power transfer.
Scraper Conveyor (2)
Transports cut coal away from the working face, integrated with the shearer through精密 mechanical transmission components.
Cutting Arm (3)
Supports the cutting drum and enables positioning, utilizing mechanical transmission systems for precise movement control.
Coal Deflector (4)
Directs coal onto the conveyor, with adjustable positioning through auxiliary mechanical transmission mechanisms.
Gearbox (5)
Critical component housing the primary mechanical transmission systems that transfer power from the motor to other components.
Electric Motor (6)
Provides power to the entire system, connected through specialized mechanical transmission interfaces to ensure efficient energy transfer.
Control Box (7)
Houses the control systems that manage all mechanical transmission operations and other functions.
Hydraulic Traction Unit (8)
Combines hydraulic power with mechanical transmission elements to drive the shearer along the face.
Traction Sprocket (9)
Engages with the anchor chain, featuring hardened components for reliable mechanical transmission of traction forces.
Height Adjustment Cylinder (10)
Adjusts the drum height, working in conjunction with mechanical transmission systems for precise positioning.
Attitude Adjustment Cylinder (11)
Adjusts the shearer's inclination, integrating with mechanical transmission components for stable operation.
Operational Requirements
Harsh Environment Adaptability
The shearer operates in extremely harsh conditions requiring robust mechanical transmission components that can withstand dust, moisture, and vibration.
High Power Density
Working space is extremely limited, demanding mechanical transmission components with minimal mass per unit power ratio while delivering high performance.
Specialized Performance
Low movement speed combined with heavy loads requires mechanical transmission systems with high gear ratios (i=250~300) and large traction forces (120~400kN).
System Capabilities
- Stepless speed regulation for optimal adaptability to varying coal seam conditions
- Comprehensive and reliable safety protection functions to prevent equipment damage
- Flexible and convenient operation interfaces for efficient control
- Integration of hydraulic and mechanical transmission systems for optimal performance
- Hydraulic actuation for drum height adjustment and attitude control
- Coal deflector flipping mechanisms using dedicated hydraulic systems
- Simple open-loop systems for auxiliary functions independent of the main traction system
- Robust mechanical transmission interfaces between all major components
Hydraulic Traction System
The hydraulic traction system of the MLS₃—170 shearer represents a sophisticated integration of hydraulic power with mechanical transmission technology. This system is responsible for propelling the shearer along the mining face with precise control over speed and direction.
The main pump (1) is an inclined-axis axial piston pump with constant power variable displacement mechanism, while the motor (2) is an inclined-axis fixed displacement piston motor of the same specification as the main pump. This configuration ensures efficient power transfer and control through a combination of hydraulic and mechanical transmission principles.
The constant power variable displacement mechanism of the main pump includes three components: pump position regulator, hydraulic constant power regulator, and motor constant power regulator. These components work in harmony to maintain optimal performance across varying load conditions while protecting the mechanical transmission components from overload.
Key System Components
Pump Position Regulator (15)
The pump position regulator is essentially a manual servo variable displacement mechanism, comprising a speed control rod (15.1), large spring (15.2), spring sleeve (15.3), V-shaped plate (15.4), feedback lever (15.5), servo spool valve (15.6), and variable displacement piston (15.7). This component forms a critical interface between operator input and the mechanical transmission system.
In the free state where the large spring is not compressed, all parts of the regulator are in positions corresponding to the pump's zero displacement. When the handle (21) is rotated or the gear (22) is turned, the speed control rod is moved up or down via a screw and nut mechanism, compressing the large spring in either direction. Assuming the compression amount is x, if the switch piston (16) is in the right position (unlocked) releasing the V-shaped plate, the V-shaped plate will move in the same direction (up or down as shown) by x under the force of the large spring.
This displacement x is transmitted through the feedback lever to actuate the servo spool valve, causing the variable displacement piston to move by x, thus setting the main pump to operate with the corresponding direction and displacement. Therefore, the pump position regulator can be used directly for manual speed regulation and direction change of the motor, demonstrating the integration of manual controls with mechanical transmission systems.
In practice, however, it functions primarily as a setting device for system operating speed and direction, while the hydraulic constant power regulator and motor constant power regulator provide automatic speed regulation within the set speed range, working in conjunction with the mechanical transmission components to maintain optimal performance.
Hydraulic Constant Power Regulator (17)
The hydraulic constant power regulator consists of a small plunger (17.1) and a balancing spring (17.2) installed in the switch piston (16). One end of the small plunger communicates with the high-pressure side of the system, and the hydraulic force it experiences is always balanced with the spring force. Consequently, the extension distance x₁ of the small plunger is proportional to the system's hydraulic pressure, effectively serving as a pressure feedback measuring device for the mechanical transmission system.
Motor Constant Power Regulator (18)
The motor constant power regulator includes a small piston (18.1) with adjustable stroke and a 3-position 4-way solenoid valve (18.2). The axes of these regulator's plunger and piston are colinear and correspond to the neutral position of the main pump. The solenoid valve (18.2) is controlled by current signals measured by a current feedback system, functioning as a relay-type nonlinear control element with a dead zone. The outward extension distance of the small piston (18.1) is x₂. This component works in tandem with the mechanical transmission system to prevent motor overload under varying load conditions.
System Operation
During system operation, the switch piston is always in the rightmost released position under the action of low-pressure control oil. The pump position regulator establishes the basic operating parameters, while the hydraulic and motor constant power regulators continuously adjust the system performance within these parameters. This combination of manual setting and automatic regulation ensures that the mechanical transmission components operate within their optimal performance range while protecting against overload conditions. The main components of this system are represented in the block diagram shown in Figure 8-4, illustrating the integration of hydraulic and mechanical transmission technologies.
Technical Advantages
Performance Benefits
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Optimized Power Transmission
The integration of hydraulic systems with advanced mechanical transmission components ensures efficient power utilization across all operating conditions.
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Constant Power Operation
The dual constant power regulators maintain optimal power output regardless of load variations, protecting both hydraulic and mechanical transmission components.
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Precise Control
Combination of manual and automatic control systems provides operators with precise control over all mechanical transmission functions.
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Robust Construction
All mechanical transmission components are designed to withstand the harsh mining environment, ensuring long service life.
Operational Benefits
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Variable Speed Operation
Stepless speed regulation allows the shearer to adapt to varying coal conditions without compromising the integrity of mechanical transmission systems.
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Comprehensive Protection
Multiple safety systems protect both operators and equipment, monitoring mechanical transmission performance in real-time.
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Ease of Maintenance
Modular design of mechanical transmission components allows for efficient maintenance and repair, minimizing downtime.
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Operator-Friendly Design
Intuitive controls and feedback systems make operation straightforward while providing clear status information about mechanical transmission performance.
Applications and Usage
The MLS₃—170 shearer is designed for application in modern fully mechanized longwall mining operations, where it serves as the primary coal cutting equipment. Its robust design and advanced mechanical transmission systems make it suitable for a wide range of coal seam conditions, providing reliable performance even in challenging environments.
Coal Seam Characteristics
Ideal for medium to thick coal seams where its powerful mechanical transmission systems can efficiently cut and extract coal while maintaining optimal productivity.
Mining Conditions
Performs well in both soft and hard coal formations, with its adjustable mechanical transmission parameters allowing adaptation to varying geological conditions.
Production Requirements
Suitable for high-production mining operations where consistent performance and reliability of mechanical transmission systems are critical to meeting production targets.
The integration of hydraulic systems with precision mechanical transmission components allows the MLS₃—170 shearer to deliver exceptional performance across these applications. Its ability to continuously adjust to changing conditions while maintaining optimal power output ensures maximum productivity and efficiency in coal extraction operations. The system's design philosophy emphasizes the harmonious interaction between hydraulic power and mechanical transmission elements, resulting in a machine that sets industry standards for reliability and performance in modern coal mining.
Conclusion
The MLS₃—170 shearer represents a pinnacle of mining equipment engineering, incorporating advanced hydraulic systems and sophisticated mechanical transmission technologies to deliver exceptional performance in harsh mining environments. Its design addresses the unique challenges of underground coal extraction through a combination of robust construction, precise control systems, and efficient power transmission. The integration of hydraulic actuation with high-performance mechanical transmission components ensures that the shearer can adapt to varying conditions while maintaining optimal productivity and safety. As a representative of modern mining equipment, the MLS₃—170 stands as a testament to the advancements in mechanical transmission and hydraulic control technologies that continue to drive the efficiency and safety of coal mining operations worldwide.
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