Constant Force Skinfold Caliper with Cam Actuator
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Solution Overview
Problem
Existing skinfold thickness measurement devices lack the ability to apply a consistent force and maintain parallelism of end tips, limiting their measurement range and accuracy, especially for thicker skinfold measurements.
Innovation Solution
A device with a constant force actuator comprising a crescent-shaped saddle, drums, bearings, and a cam system that ensures a constant pressure application, combined with a mechanism for maintaining parallelism of end tips through a parallelogram or inextensible cable configuration, allowing for measurements up to 110 mm with enhanced resolution and ergonomic design for wireless communication and tactile interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing skinfold measurement devices are used, then the measurement function is provided, but the force application is inconsistent and measurement accuracy is limited
Solution Approach 1:
The constant force actuator is pre-configured with calibrated spring elements and cam mechanisms that automatically apply the precise required force (e.g., 10g/mm²) when the jaws contact the skinfold. This preliminary setup eliminates the need for operator judgment about force application, ensuring consistent and accurate measurements across all users and measurements.
Solution Approach 2:
The device transforms the variable force application problem into a controlled parameter system where spring constant, cam profile, and jaw geometry are precisely engineered to maintain constant force throughout the measurement range. This allows the force parameter to remain stable while the measurement parameter (skinfold thickness) varies.
2Adaptability or versatility
If conventional skinfold measurement devices are used, then basic measurement is possible, but the measurement range is limited especially for thicker skinfolds
Solution Approach 1:
The device maintains constant force through a third dimension - the vertical movement of the cam follower along the cam profile - while the jaws open horizontally to accommodate varying skinfold thicknesses. This dimensional approach allows the force arm length to remain effective across a wide measurement range (up to 110 mm) without sacrificing precision.
Solution Approach 2:
The parallelism mechanism dynamically adjusts the orientation of the end tips during jaw opening, ensuring they remain parallel to the skin surface regardless of the skinfold thickness. This dynamic adaptation maintains measurement accuracy across the entire measurement range from thin to thick skinfolds.
3Reliability
If a constant force mechanism is added to maintain consistent pressure, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The constant force actuator is self-regulating through the cam mechanism - as the jaws close and the force arm length would naturally vary, the cam profile automatically compensates by adjusting the lever arm geometry. This self-service mechanism maintains constant force without requiring external control systems, sensors, or power sources, thus limiting complexity increase.
4Measurement precision
If end tips are made hinged and oriented to maintain parallelism, then measurement accuracy for various skinfold thicknesses improves, but mechanical complexity increases
Solution Approach 1:
The end tips are designed with asymmetric hinge arrangements where one tip is fixed to its jaw while the other tip is free to rotate on a perpendicular axis. This asymmetric configuration, combined with the parallelism mechanism, allows automatic orientation maintenance without complex active control, reducing the complexity increase compared to symmetric active control systems.
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 achieves accurate and consistent skinfold thickness measurements beyond conventional limits, ensuring uniform pressure and increased user convenience with wireless data transmission and tactile feedback.
Implementation Method 1
the elastic element of the constant force actuator (11D) is based on a constant force spring
Implementation Method 2
a sensor for reading the jaws displacement and converting this displacement into the skinfold thickness measurement
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The object of the present invention is a device for measuring skinfold thickness digitally instrumented for reading the thickness of skin folds and possessing wireless data communication capability with a remote station (for example, a personal computer) in which is installed a software application integrating a database. The developed device utilises working principles distinct from those available in the market, in particular uses a constant force actuator (11) integrated in the device handle (12A), whose primary function is to impose a constant contact pressure between the end tip faces (1A and 1B) and the skinfold under measurement. Another characteristic is related to the increase of the opening limit of the end tips (1A and 1B) by using a large centre distance for the jaws pivot axes, jointly with a cam for compensating the change in the force arm length, the constant force actuator and the orientation mechanism of the clamping faces of the end tips, whereby the application of a constant pressure throughout the whole measuring range is accomplished.