Tube Mill Torque Control for Frozen Charge Detachment
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Solution Overview
Problem
Existing methods for removing frozen charges from grinding pipes in tube mills are laborious and can cause damage due to the risk of the charge dropping and hitting the inner surface, especially in mills with geared drives where negative torque can lead to backlash and mechanical stress on gear teeth.
Innovation Solution
A method and apparatus that control the driving torque applied to the grinding pipe to vary sinusoidally or stepwise about a predetermined increasing reference level, ensuring the torque remains positive and minimizing mechanical stress, facilitating the detachment of frozen charges without causing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manual removal methods (air compressed hammers) are used to remove frozen charge, then the frozen charge can be removed, but the process is laborious and time-consuming
Solution Approach 1:
The patent replaces manual mechanical removal methods (air compressed hammers) with an automated control system that modulates the driving torque of the tube mill. The controller automatically varies the driving torque about a reference level to detach frozen charge, eliminating the need for manual intervention and significantly improving removal efficiency while reducing time consumption.
2Reliability
If negative torque is applied to geared drives during frozen charge removal, then the frozen charge can be detached, but backlash occurs on gear teeth causing mechanical stress and reduced drive train lifetime
Solution Approach 1:
The controller is designed to prevent negative torque from occurring in the first place by modulating the driving torque about a reference level in a controlled manner. The torque variation is designed to detach frozen charge through controlled oscillation rather than through negative torque reversals, thereby preventing backlash and mechanical stress on gear teeth before they can occur.
Solution Approach 2:
The patent applies dynamic modulation of the driving torque rather than static torque application. The controller varies the driving torque dynamically about a reference level, creating controlled oscillations that facilitate frozen charge detachment while maintaining positive torque throughout the cycle, thus protecting the drive train from damage.
3Reliability
If frozen charge is allowed to detach at the highest point of rotation, then detachment occurs naturally, but the charge drops onto the inner surface causing substantial damage
Solution Approach 1:
The controller detaches the frozen charge from the inner wall before the tube mill rotates to the position where the charge would drop and cause damage. By modulating the driving torque to create detachment forces while the mill is in a safe rotational position, the frozen charge is removed preventively, eliminating the harmful dropping effect before it can occur.
Solution Approach 2:
The controlled torque modulation acts as an intermediary mechanism between the frozen charge and the gravitational force that would cause damage. By introducing controlled torque variations as a mediating force, the frozen charge is detached through a controlled process rather than through uncontrolled gravitational dropping, thereby preventing damage to the grinding pipe.
Data Source
AI summary
A method and associated apparatus for detaching a frozen charge from an inner wall of a grinding pipe of a tube mill such as is used for grinding. The method includes controlling a driving device of the grinding pipe to detach a frozen charge from an inner wall of the grinding pipe, which driving device is operable to apply a driving torque to the grinding pipe. Controlling the driving device includes varying the driving torque applied to the grinding pipe around a predetermined reference level.