Force-Fit C-Shaped Pulley for Axial Stability and Belt Wear
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Solution Overview
Problem
Existing pulley devices for tensioning idlers or runner rollers suffer from early belt wear and radial deformation under heavy loads, due to design flaws such as annular recesses and axial movement, which compromise their rigidity and effectiveness in supporting belts or chains.
Innovation Solution
A pulley device with a C-shaped pulley part design, featuring a frustoconical inner portion force-fitted onto a rotatable outer ring, providing enhanced rigidity and stability through interference fit, and incorporating rolling elements between concentric inner and outer rings, along with annular cages and seals, to prevent axial movement and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If male and female overlapping parts are fastened together to form a cylindrical outer portion, then the pulley structure is formed, but an annular recess is created causing early belt wear
Solution Approach 1:
The pulley is divided into multiple parts: a C-shaped pulley body, an inner portion, and an outer portion. These segmented parts are assembled together to form the complete pulley structure, eliminating the need for overlapping parts that create harmful recesses.
Solution Approach 2:
The harmful annular recess is completely removed from the design. Instead of forming recesses during assembly, the pulley surface is designed to be continuous and recess-free, directly addressing the belt wear problem.
2Ease of operation
If the pulley is tightened to the outer ring of bearing, then the pulley is secured, but the pulley can still slightly axially move during service use
Solution Approach 1:
The design proactively prevents axial movement by incorporating a flange on the inner portion that abuts against the bearing outer ring. This preliminary constraint structure eliminates the need for additional locking mechanisms and ensures stable axial positioning from the start.
3Ease of operation
If the outer part is designed to contact the belt, then belt support function is provided, but the outer part may be deformed radially inwards by bending under belt action
Solution Approach 1:
Different parts of the pulley are given different structural properties: the outer portion has increased radial thickness specifically at the belt contact area to resist bending, while other areas maintain their original design. This localized reinforcement prevents radial deformation without adding unnecessary weight or complexity elsewhere.
4Ease of manufacture
If a C-shaped pulley design is used, then the pulley is easy to install onto bearing, but the pulley may lack rigidity under heavy loads
Solution Approach 1:
The pulley is constructed as a composite structure combining the C-shaped body with separately attached inner and outer portions. This composite design maintains the installation advantages of the C-shape while adding structural elements that significantly improve rigidity and load-bearing capacity.
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
The solution ensures efficient belt or chain support with reduced wear and increased service life, maintaining constant tension and preventing radial deformation even under heavy loads, by providing a robust and easy-to-install pulley device.
Implementation Method 1
The inner portion of said pulley part comprises a frustoconical portion inwardly directed towards the outer ring, said inner portion being force fitted (friction fitted) onto outer cylindrical surface of said outer ring
Implementation Method 2
The bearing is a rolling bearing, at least one row of rolling elements being radially interposed between the inner ring and the outer ring
Implementation Method 3
the pulley part being formed integral and defining an open end on one axial side opposite to the intermediate portion... adapted to avoid an early wear of the belt, and permitting an efficient support of said belt
Data Source
AI summary
A pulley device for supporting a belt of chain tensioning idler or a runner roller includes a bearing having an outer ring mounted for rotation relative to a coaxial inner ring and at least one pulley part that is C-shaped in cross section. The pulley part has an inner portion with a frustoconical inner surface mounted on an outer cylindrical surface of the outer ring, an outer cylindrical portion having an outer cylindrical surface configured to support a belt or a chain, and an intermediate portion extending radially inward from the cylindrical outer portion to the inner portion. The pulley part is integral and has an open end on an axial side opposite the intermediate portion. The frustoconical surface extends inwardly towards the outer ring, and the inner surface is force fitted onto the outer cylindrical surface of the outer ring.