Mill Shell Liner Bolt Failure Mitigation via Pivot Block
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Solution Overview
Problem
The existing attachment assembly in rotatable mill shells frequently experiences bolt failure due to dynamic loading and pivoting movements of lifter bars, leading to premature wear and downtime in grinding mills.
Innovation Solution
The proposed liner system incorporates a channel plate with lateral extensions and outer arms, along with insert elements positioned between the lateral extensions and the mill shell, which resist outward movement and pivot-induced stress on the bolt, maintaining its alignment and reducing the risk of failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the bolt is allowed to pivot with the channel plate under dynamic loading, then the attachment assembly can accommodate movement, but the bolt experiences increased stress and premature failure
Solution Approach 1:
The patent introduces a pivot block as an intermediary component between the channel plate and the bolt. The pivot block receives the pivoting movement from the channel plate through its curved surface, while its flat opposite surface maintains stable contact with the bolt, preventing the bolt from experiencing direct pivot-induced stress while still allowing necessary movement accommodation.
2Reliability
If the bolt is constrained to remain stationary, then bolt life is extended, but the attachment assembly cannot accommodate dynamic loading movements
Solution Approach 1:
The pivot block serves as a mediator that absorbs the pivoting motion generated during dynamic loading. By positioning the pivot block between the moving channel plate and the stationary bolt, it allows the channel plate to pivot freely while the bolt remains constrained and stationary, thus extending bolt life while maintaining movement accommodation capability.
Solution Approach 2:
The patent resolves the contradiction by separating the movement accommodation function from the bolt in a different dimensional space. The pivot block's curved surface accommodates pivoting movements in one dimension, while the flat surface maintains the bolt in a stationary position in another dimension, effectively decoupling the movement and constraint requirements.
3Device complexity
If the bolt axis is aligned with the channel axis, then the attachment geometry is simplified, but the bolt remains vulnerable to pivot-induced stress during operation
Solution Approach 1:
The pivot block is positioned between the channel plate and the bolt, serving as a mediator that protects the bolt from pivot-induced stress. This allows the bolt to maintain simple alignment with the channel axis for geometric simplicity, while the pivot block absorbs the harmful pivot movements, thus achieving both simplified geometry and improved reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces the risk of bolt failure by restricting outward pivoting movements of the channel plate, thereby extending the bolt's useful life and minimizing downtime in grinding mills.
Implementation Method 1
one or more insert elements positioned between the lateral extension(s) and the inner side of the mill shell, for resisting outward movement of the lateral extension(s) toward the inner side
Implementation Method 2
The outer arm is formed to resist movement of the fixing washer outwardly, toward the inner side of the mill shell
Implementation Method 3
the nut 44, when tightened, urges an outer washer 46 against the mill shell 22, to subject the bolt 36 to tension, thereby pulling the lifter bar 20 outwardly
Implementation Method 4
The attachment assembly also includes a bolt defining a bolt axis and extending between inner and outer ends, the bolt comprising a head at the inner end engageable with the fixing washer
Implementation Method 5
the lip portions 48A, 48B are squeezed between the lifter bar 20 and the mill shell 22 when the nut 44 is tightened on the bolt 36
Implementation Method 6
The limited resilience of the at least partially rubber body 29 is thought to advantageously decrease the rate of wear of the body, because the resilience allows the lifter bar body 29 to absorb some of the dynamic impact of the solid parts of the charge colliding with it
Implementation Method 7
Where the body 29 is a suitable rubber or rubber composite, the channel plate 30 is initially held in place by vulcanization, i.e., by a chemical bond
Implementation Method 8
once the attachment assembly 24 is tightened to secure the lifter bar 20 in place inside the mill shell 22, the lateral extensions 50A, 50B are also mechanically secured to the portions 52A, 52B of the body 29
Data Source
AI summary
A liner system for installation in a rotatable mill shell having an inner side and an opposed outer side, the liner system including one or more lifter bars. The lifter bar includes a body, a channel plate secured to the body and defining a channel axis, including one or more lateral extensions extending transversely from the central portion in relation to the channel axis, and one or more insert elements positioned between the lateral extension and the inner side of the mill shell, for resisting outward movement of the lateral extension toward the inner side. The liner system also includes one or more attachment assemblies, each including a bolt, for securing the lifter bar to the mill shell. The insert elements are configured to maintain the bolt in a predetermined position in which an axis of the bolt is aligned with the channel axis.