Constant Tension Device for Stringed Instruments
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Solution Overview
Problem
Stringed musical instruments often go out of tune due to changes in string tension caused by stretching or contracting over time and environmental factors, requiring frequent tuning and potentially intrusive or aesthetically undesirable solutions.
Innovation Solution
A spring-based tension device that maintains near-constant tension in strings by using a secondary spring to compensate for changes in primary spring force as the string lengthens or shortens, ensuring minimal audible frequency shifts within a defined operational range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spring is used to apply tension to the string, then the device structure is simple, but the tension varies significantly as the string stretches or contracts
Solution Approach 1:
The tension application system is segmented into two separate springs (primary spring and secondary spring) that independently contribute to the total tension. The primary spring provides initial tension while the secondary spring compensates for length changes, dividing the tension-maintenance function into specialized components that together achieve stable tension.
Solution Approach 2:
The secondary spring is oriented at an angle (approximately 45 degrees) relative to the string axis, introducing a geometric dimension to the tension system. As the string length changes, the angular orientation of the secondary spring changes, converting axial displacement into a compensating force component that stabilizes total tension.
2Reliability
If a secondary spring is added to compensate for primary spring force changes, then the tension stability improves, but the device complexity increases
Solution Approach 1:
The primary and secondary springs are merged into a unified tension application system where their forces combine vectorially. The carrier integrates both spring attachments and combines their force vectors to produce the total tension on the string, achieving stable tension through force superposition rather than requiring separate adjustment mechanisms.
Solution Approach 2:
The carrier serves as an intermediary component that mediates between the two springs and the string. It provides attachment points for both springs and transmits their combined force to the string, allowing the springs to work together indirectly through this intermediate element rather than requiring direct mechanical coupling.
3Reliability
If the carrier moves longitudinally to accommodate string length changes, then the tension compensation works effectively, but the frequency of tension change increases
Solution Approach 1:
The system transitions from a static spring arrangement to a dynamic configuration where the carrier moves longitudinally along with the string length changes. The secondary spring's angular orientation dynamically adjusts as the carrier position changes, automatically modulating its force contribution to maintain constant total tension throughout the operational range.
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 device effectively maintains string tension within a small percentage of the preferred tension, minimizing tuning requirements and maintaining instrument sound and appearance integrity.
Implementation Method 1
a primary spring connected to the string via the carrier and adapted to supply a primary spring force in response to a change in string tension
Implementation Method 2
a secondary spring connected to the carrier and adapted to apply a secondary spring force to the carrier... the axial component of force applied to the carrier by the secondary spring increases in the direction the carrier moves as the guitar string elongates
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
A support is configured to support and apply a constant or near-constant tension onto a wire or string, such as a musical string of a stringed musical instrument. The wire is attached to a carrier that moves axially. One or more springs operate between the carrier and a point that is fixed relative to the carrier and apply a transverse spring force to the carrier. A spring angle is defined between a line normal to the axis and a line of action of each spring. The transverse spring force can have an axial force component and an axial spring rate that is a function of the spring angle. The carrier can be positioned so that the axial spring rate is zero, negative or positive. A primary spring can apply a primary force directed coaxial with the wire. If the wire changes in length the primary force will correspondingly change, as will the axial force component. The transverse spring can be selected so that the axial force component of the transverse spring approximates the change in the force applied by the primary spring so that the axial force applied to the carrier and wire remains generally constant.