String Bed Stiffness Measurement Device Using Spring Deflection
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Solution Overview
Problem
Existing devices for measuring string bed stiffness in tennis rackets are costly, bulky, complex, and lack accuracy and repeatability due to mechanical creep and failure to account for string gauge variations and notching, making them unsuitable for average users.
Innovation Solution
A portable, lightweight device with a force measuring system and adjustable positioning mechanism that uses strain gauges and a stop to ensure consistent deflection measurement, independent of mechanical creep, and accounts for string gauge and notching variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electronic detection and surface movement devices are used to measure string bed stiffness, then measurement capability is provided, but the device becomes expensive, bulky, and not portable
Solution Approach 1:
The patent replaces complex electronic detection systems and motorized surface movement mechanisms with a simple mechanical spring-based deflection measurement system. The measuring device uses a spring element that deflects under applied force, and the deflection amount directly indicates string bed stiffness, eliminating the need for expensive sensors, motors, and electronic control systems.
Solution Approach 2:
The patent employs simple, inexpensive mechanical components such as spring elements and dial indicators that can be easily manufactured and replaced. The design prioritizes cost-effectiveness and simplicity over durability, using components that are cheap to produce and replace if needed, rather than investing in expensive, complex electronic systems.
2Ease of manufacture
If plastic components are used in the measuring device, then manufacturing is easier, but mechanical creep occurs under pressure causing measurement inaccuracy
Solution Approach 1:
The patent changes the material parameter from plastic to metal for components subjected to measurement pressure. Specifically, the spring element and other load-bearing components are made from metal materials that do not exhibit mechanical creep, ensuring measurement accuracy is maintained over time while still allowing for relatively simple manufacturing processes.
3Measurement precision
If fixed deflection distance devices are used, then string bed stiffness can be measured, but the device does not account for racket thickness differences and string gauge differences
Solution Approach 1:
The patent employs a spring-based system where the deflection distance is not fixed but dynamically adjusts based on the string bed's resistance. The spring compresses by an amount determined by the string bed stiffness and the applied force, automatically adapting to different racket thicknesses, string gauges, and string tensions without requiring manual adjustment or pre-programming.
Solution Approach 2:
The measuring device is designed with universal applicability to accommodate various racket types, string gauges, and string tensions. The spring mechanism and dial indicator combination provides a general-purpose measurement system that works across different conditions without requiring device modification, making it versatile for all string bed stiffness measurements.
4Ease of operation
If simple mechanical devices are used, then portability and ease of use improve, but measurement accuracy and repeatability decrease due to mechanical creep
Solution Approach 1:
The patent replaces creep-prone plastic mechanical components with metal components that maintain their dimensional stability under load. The spring element, dial indicator, and other mechanical parts are constructed from metal materials that do not exhibit mechanical creep, ensuring measurement repeatability is maintained while preserving the simplicity and portability of the mechanical device design.
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
Provides consistent, accurate, and repeatable measurements of string bed stiffness, adaptable to different racket sizes and stringing patterns, while being easy to use and cost-effective.
Implementation Method 1
the spring factor and, in particular, the string bed must be taken into account
Implementation Method 2
measuring the force exerted by the deflection
Implementation Method 3
a biasing arrangement connected to the force measuring device and adapted to be connected to the string bed for deflecting the string bed
Data Source
AI summary
A device for measuring stiffness of the string bed of a racket, includes a main body adapted to sit on the string bed; a force measuring device mounted to the main body; a biasing arrangement connected to the force measuring device and adapted to be connected to the string bed for deflecting the string bed in relation to the force measuring device, and causing the force measuring device to output a signal corresponding to the deflection of the string bed; a stop connected to the main body in a manner such that the stop is not acted upon by the deflection of the string bed when deflected by the biasing arrangement and which limits the string bed to a predetermined amount of deflection by the biasing arrangement; a switch to provide an output when the string bed is deflected to at least a predetermined position; a display for displaying the stiffness of the string bed in accordance with the signal output from the force measuring device in response to a change in the output from the switch as the string bed moves from the deflected position to an undeflected position; and a positioning device to repeatably position the string bed stiffness measuring device on the string bed.