Shredder Knife Asymmetry for Axial Thrust Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current shredder designs face high production and maintenance costs due to the generation of significant axial thrust from equally-oriented force reactions on fixed knives, requiring oversized and expensive thrust-bearings, which limits the structural simplicity and efficiency of the machine.
Innovation Solution
The shredder design balances reaction forces on fixed knives by positioning them in a way that the axial thrust is canceled out, using a table with metal sheets that support fixed knives orthogonally to the shaft axis, allowing for a more balanced distribution of forces and reduced bearing loads, and enabling the use of larger or thinner metal sheets based on the angle of inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed knives are positioned with equally-oriented force reactions on the same face of rotating knives, then material cutting effectiveness is improved, but axial thrust on the shaft increases requiring expensive and bulky thrust-bearings
Solution Approach 1:
The patent applies asymmetry by positioning fixed knives on both faces of the rotating knife in opposite orientations. Specifically, fixed knives are arranged such that one set acts on the first face of the rotating knife while another set acts on the second face, creating an asymmetric force distribution that balances the axial thrust. This allows the force reactions to counterbalance each other, eliminating the need for bulky thrust-bearings while maintaining cutting effectiveness.
2Strength
If shafts and knives are oversized to handle the axial thrust, then structural strength is improved, but production and maintenance costs increase
Solution Approach 1:
The patent employs the counterweight principle by arranging fixed knives to create opposing force reactions that balance the axial thrust. The fixed knives are positioned such that the force generated on one face of the rotating knife is counterbalanced by an equal and opposite force on the other face. This force balancing allows the use of normally sized shafts and knives without oversizing them for thrust handling, thereby reducing production and maintenance costs while maintaining adequate structural strength.
3Device complexity
If vertical metal sheets are used to support fixed knives orthogonally to the shaft axis, then structural simplicity is improved, but flexibility in knife disposition is limited
Solution Approach 1:
The patent applies dimensionality change by transitioning from supporting fixed knives only on vertical metal sheets (one-dimensional support) to using inclined metal sheets that provide support in multiple orientations (multi-dimensional support). The inclined sheets allow fixed knives to be positioned at various angles and locations relative to the shaft axis, enabling more flexible knife dispositions while maintaining structural simplicity. This dimensional expansion of the support structure provides greater adaptability in knife arrangement.
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 reduces the need for heavy-duty bearings, lowers production and maintenance costs, extends the working life of rotating knives, and allows for a more modular and cost-effective shredder design with improved material processing efficiency.
Implementation Method 1
the material to be chipped is hooked by the rotary knife and sliced against the adjacent fixed knife
Implementation Method 2
the comminuted parts fall by gravity and are collected below the table
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A shredder machine (MC) for waste material is disclosed. It comprises a table (60) equipped with fixed knives (22, 24); a shaft (30a) rotatably mounted on the table and equipped with an array of rotating knives (20a) which are axially spaced and radially projecting from the shaft; wherein the rotary knives have a face (36a) adjacent to, and adapted to cooperate with, a fixed knife (24) for cutting the material. To prevent axial imbalance of forces, the machine comprises a pair of fixed knives (22, 24) where one (22) is adjacent to, and adapted to cooperate with, a face (28a) of a rotating knife and the other (24) is adjacent to, and adapted to cooperate with, the opposite face (36a) of the same rotating knife.