Worm Drive Preload Mechanism for Backlash-Free Positioning
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Solution Overview
Problem
Worm drives with fixed play suffer from high friction, wear, and limited precision due to thermal expansion and manufacturing tolerances, making them inefficient and unsuitable for precise positioning applications, and require complex and costly adjustments for changing operating conditions.
Innovation Solution
An adjustable preload mechanism using guide bolts and a spring element between the worm shaft and worm wheel receiving units, allowing for axial movement and compensation for thermal expansion and manufacturing tolerances, minimizing friction and wear while maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed clearance is provided between the worm shaft and worm wheel to compensate for thermal expansion and manufacturing tolerances, then the worm drive can operate smoothly at different temperatures, but this clearance causes gear play and prevents precise positioning applications
Solution Approach 1:
The invention replaces the fixed clearance with a dynamic preload mechanism that actively maintains optimal tooth contact. The receiving unit of the worm shaft is made movable relative to the worm wheel receiving unit, allowing the system to adapt to thermal expansion and manufacturing tolerances dynamically rather than relying on a predetermined fixed clearance. This enables precise positioning while accommodating temperature variations.
Solution Approach 2:
The invention changes the parameter of clearance from a fixed value to a variable parameter that can be adjusted. By providing axial movement capability between the receiving units and applying a preload force, the system can maintain the desired tooth contact parameter under varying operating conditions, thereby achieving both smooth operation and positioning precision.
2Loss of energy
If different materials are used for the worm shaft and worm wheel to reduce friction, then sliding friction is reduced, but the different thermal expansion coefficients lead to increased wear and jamming
Solution Approach 1:
The invention introduces an intermediary mechanism (the movable receiving unit with preload) that mediates between the worm shaft and worm wheel. This intermediary allows the system to maintain optimal contact pressure and accommodate differential thermal expansion between the different materials, preventing jamming and excessive wear while preserving the low-friction benefits of material pairing.
3Loss of substance
If a fixed clearance is used to accommodate manufacturing tolerances, then wear is kept low under normal conditions, but the clearance causes backlash and limits positioning accuracy
Solution Approach 1:
The invention applies a preliminary preload force to the worm shaft receiving unit before operation begins. This preliminary action ensures that the gear teeth are already in optimal contact under load conditions, eliminating backlash. The preload is maintained through the movable connection that compensates for wear over time, keeping the system precision-maintained.
4Manufacturing precision
If the worm shaft receiving unit is made movable with respect to the worm wheel receiving unit to enable preload adjustment, then positioning precision and wear compensation are improved, but the device complexity increases
Solution Approach 1:
The invention segments the worm drive system into two independently movable receiving units - one for the worm shaft and one for the worm wheel. This segmentation allows the worm shaft receiving unit to move axially independently to apply preload, while the worm wheel receiving unit remains relatively fixed. The segmentation enables precise positioning control without requiring complex mechanisms throughout the entire 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
The adjustable preload mechanism reduces friction and wear, enables backlash-free operation, and allows for precise positioning, while simplifying adjustments and reducing maintenance costs by compensating for thermal expansion and manufacturing deviations.
Implementation Method 1
a spring element (10) is arranged between the first receiving unit (2) and a fastening means (12)... the spring element (10) exerts a preload on the first receiving unit (2) by means of a spring force
Implementation Method 2
guide pins (6) for detachably connecting the first receiving unit (2) to the second receiving unit (3)... the first receiving unit (2) is in contact with the worm gear (5) of the second receiving unit (3)
Implementation Method 3
compensating for thermal expansion and manufacturing tolerances... in particular in the case of changed play due to manufacturing tolerances and different thermal expansion coefficients of the materials used for the mechanical components
Data Source
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AI summary
The invention relates to a worm drive comprising a worm shaft and a first receiving unit. The worm shaft is rotatably mounted in the first receiving unit. Furthermore, the worm drive comprises a worm wheel and a second receiving unit. The worm wheel is rotatably mounted in the second receiving unit. The first receiving unit is arranged on the second receiving unit and the rotatably mounted worm shaft is in contact with the worm wheel of the second receiving unit in order to transmit a torque. Furthermore, the worm drive comprises guide pins for detachably connecting the first receiving unit to the second receiving unit. More particularly, the first receiving unit receives at least part of the guide pins and the second receiving unit is connected to one of the guide pins, preferably to a first end of the guide pin. A spring element is arranged on a second end of the guide pin between the first receiving unit and a fastening means.