High-Offset Belt Tensioner with Offset Torsion Spring Loading
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Solution Overview
Problem
Traditional high-offset belt tensioners face challenges in effectively counterbalancing the torsion spring force and improving wear resistance, as the spring force is primarily directed inward on the pivot, leading to uneven wear and reduced mechanical advantage.
Innovation Solution
The high-offset belt tensioner design features a flat wire torsion spring with an inner spring hook attached to the pivot tube and an outer spring hook attached to the arm, positioning the spring force radially outward to counterbalance the hub load force and improve wear distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner spring hook is attached to the arm arbor in a traditional ZED-style belt tensioner, then the spring force is directed inward on the pivot, but this causes uneven wear on the bushing and reduced mechanical advantage
Solution Approach 1:
The patent inverts the traditional attachment configuration by making the outer spring hook movable (attached to the arm) and the inner spring hook stationary (attached to the spring case). This reversal moves the spring force application point from the pivot center to a radial offset position, thereby improving mechanical advantage and wear distribution while maintaining the same functional outcome of belt tensioning.
2Stability of the object's composition
If the spring case is mounted to a non-rotatable member, then the spring force direction remains fixed relative to the spring case, but this causes the spring to wind onto the arm arbor and increase pressure on the pivot bushing
Solution Approach 1:
The patent introduces a radial offset dimension to the spring force application point. By attaching the outer spring hook to the arm at a position offset from the pivot axis, the spring force acts at a distance from the pivot center, creating a moment arm that reduces the direct axial pressure on the pivot bushing while maintaining the stabilizing effect of the spring force direction.
3Reliability
If a large bushing is used on the pivot tube to reduce pressure and improve alignment control, then wear is reduced, but the device complexity and size increase
Solution Approach 1:
The patent extracts the wear and pressure management function from the pivot bushing by relocating the spring force application point. This allows the use of a smaller, simpler bushing design while achieving the same or better wear resistance and alignment control through the improved mechanical advantage provided by the offset spring force application.
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 design enhances mechanical advantage by moving the spring force radially outward, reducing wear on the arm and improving the belt tensioner's ability to maintain tension over its lifetime, while also increasing the surface area of pivot bushings for reduced pressure and longer bearing life.
Implementation Method 1
a flat wire torsion spring having an inner spring hook attached to the pivot tube and an outer spring hook attached to the first end of the arm at a position that counterbalances the hub load force
Implementation Method 2
the flat wire torsion spring biases the arm in a belt engaging direction and applies a spring force acting on the arm
Data Source
AI summary
High-offset belt tensioners have a support base with a pivot tube and an arm coupled thereto rotation about a pivot axis. A flat wire torsion spring has an inner spring hook attached to the pivot tube and an outer spring hook attached to a first end of the arm at a position that counterbalances a hub load force. The torsion spring applies a spring force to the arm in a direction that moves with the arm throughout its entire sweep in a belt engaging direction. A first plane of the hub load force is axially offset from a second plane of the spring force, a fulcrum is defined between first and second ends of the arm, and a first lineal axial distance from the fulcrum to the first plane is greater than or equal to a second lineal axial distance from the fulcrum to the second plane.