Flat-Belt Linear Actuator Sheave Layout for Zero Fleet Angle
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Solution Overview
Problem
Flat belts in linear actuator systems are prone to premature failure due to fleet angles, which are detrimental to their service life and traction efficiency, especially in high-reduction block and tackle topologies, unlike wire ropes that can tolerate such angles.
Innovation Solution
A geometric mapping technique is employed to position the centerlines of sheaves on a common axis, eliminating fleet angles in the block and tackle design, allowing for the use of high-performing flat belts in high-reduction systems by tilting sheaves to ensure zero-fleet angle conditions, thereby maintaining belt tension and extending service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If block and tackle topology is used for high reduction ratios, then mechanical advantage is improved, but fleet angles are introduced that reduce belt service life
Solution Approach 1:
The patent applies asymmetry by positioning sheaves at different radial distances from the motor shaft centerline. The first sheave is positioned at a first radial distance while the second sheave is positioned at a second radial distance that is different from the first radial distance. This asymmetric arrangement allows the belt to wrap around sheaves at different angles without creating fleet angles, thereby maintaining both high mechanical advantage and belt service life in a 7:1 reduction system.
Solution Approach 2:
The patent transitions from a conventional planar block and tackle arrangement to a three-dimensional configuration where sheaves are positioned at different radial distances from the motor shaft. This dimensional change allows the belt path to accommodate high reduction ratios without creating fleet angles, as the belt wraps around sheaves located at different radial positions rather than being constrained to a single plane.
2Reliability
If wire rope is used instead of flat belt, then tolerance to fleet angles is improved, but maintenance requirements and service life are worsened
Solution Approach 1:
The patent changes the fundamental parameter of the flexible member from wire rope to flat belt construction. This parameter change allows the system to achieve both maintenance-free operation and extended service life while accommodating fleet angles through the asymmetric sheave positioning. The flat belt's ability to flex and conform to the asymmetric sheave arrangement eliminates the need for lubrication and complex maintenance associated with wire rope systems.
3Productivity
If conventional block and tackle is used with flat belt, then mechanical reduction is achieved, but fleet angles substantially reduce expected system service life
Solution Approach 1:
The patent applies asymmetry by positioning sheaves at different radial distances from the motor shaft centerline. The first sheave is positioned at a first radial distance while the second sheave is positioned at a second radial distance that is different from the first radial distance. This asymmetric arrangement allows the belt to wrap around sheaves at different angles without creating fleet angles, thereby maintaining both high mechanical advantage and belt service life in a 7:1 reduction system.
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 solution enables the use of flat belts in high-reduction block and tackle topologies with extended service life, improved power transmission efficiency, and compact machine design, suitable for applications like construction equipment and manufacturing machinery.
Implementation Method 1
They are high performing, durable, and maintenance-free: A combination of traits that have rendered their rapid adoption across the elevator industry
Implementation Method 2
A geometric mapping technique is employed to position the centerlines of sheaves on a common axis, eliminating fleet angles in the block and tackle design, allowing for the use of high-performing flat belts in high-reduction systems by tilting sheaves to ensure zero-fleet angle conditions, thereby maintaining belt tension
Data Source
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AI summary
The disclosure provides apparatuses, systems, and methods for belt driven linear actuator systems.