Stretch Film Force Measurement Using Torque and Release Angle
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Solution Overview
Problem
Existing force sensors in stretch film testing devices are susceptible to overloading and prone to breaking, making them unreliable for accurately measuring the forces required for stretching and predicting film fracture.
Innovation Solution
A method and device that determine film forces using torque measurements and a release parameter, eliminating the need for force sensors by calculating forces based on torques, spool radii, and the angle at which the film releases from the spool, utilizing sensors like laser or cameras for precise force determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force sensors are used to measure the force on the film during stretching, then the force can be measured directly, but the force sensors are susceptible to overloading and can break easily
Solution Approach 1:
The patent replaces mechanical force sensors with a torque-based measurement system. Torque sensors are used to measure the torque required to rotate the stretch rollers, and from this torque information, the force on the film is calculated using the relationship between torque, roller radius, and film tension. This substitution eliminates the need for direct mechanical force sensing, thereby avoiding the problem of force sensors breaking under overload while maintaining measurement capability.
Solution Approach 2:
The patent introduces torque as an intermediary parameter to indirectly measure film force. Instead of directly measuring force with vulnerable sensors, the system measures torque on the rollers and uses this intermediate measurement to calculate the film force through mechanical relationships. This intermediary approach allows force measurement without direct contact with the high-stress film environment, protecting the measurement system from overload.
2Measurement precision
If force sensors are installed on the stretch rollers to measure transverse force, then the stretch ratio and film quality can be determined, but the sensors are prone to breaking and unreliable
Solution Approach 1:
The patent replaces direct mechanical force sensing with torque measurement and calculation. Torque sensors on the rollers provide reliable data that is processed through mathematical models to determine film tension and stretch characteristics. This eliminates the need for force sensors that are directly exposed to the high-stress film handling environment, thereby improving reliability while maintaining measurement precision through computational methods.
Solution Approach 2:
The patent creates a virtual copy of the force measurement function through computational modeling. Instead of using physical sensors that directly measure force, the system uses torque measurements combined with mathematical models to calculate and represent the force conditions. This virtual copying approach allows the system to infer force information without the physical sensors being subjected to the harsh mechanical environment, thereby improving reliability.
3Measurement precision
If the film is stretched between stretch rollers to determine stretch ratio, then film quality can be assessed, but the force required for stretching can overload and break the film or sensors
Solution Approach 1:
The patent replaces direct force measurement with torque measurement and calculation. By measuring torque on the stretch rollers and using this information to calculate film tension, the system can determine stretch ratio and assess film quality without subjecting physical sensors to the high forces involved in stretching. This substitution protects both the film from sensor-induced damage and the sensors from overload while maintaining measurement capability.
Solution Approach 2:
The patent uses torque as an intermediary parameter to safely measure stretching forces. Torque sensors on the rollers provide a buffered measurement that indirectly reflects film tension without direct exposure to the full stretching force. This intermediary approach allows the system to assess stretch ratio and film quality while protecting the measurement system from the extreme forces that could break the film or sensors.
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
Accurately calculates film forces without damaging the film, providing robust and precise measurements of stretching forces, enabling reliable quality assessment and prediction of film behavior.
Implementation Method 1
measuring a unwinding torque on the unwinding device
Implementation Method 2
The film runs over guide rollers and then over two stretch rollers. The second stretch roller has a greater peripheral speed than the first stretch roller, whereby the film is stretched by a predetermined length percentage.
Implementation Method 3
a measurement of a release parameter in the unwinding device which is indicative of where the film releases from the spool
Data Source
AI summary
A device for measuring a stretching force on a film, including an unwinding station to hold and unwind a spool of stretch film via an unwinding motor, and including a first stretching station with a first driven stretch roller and a second driven stretch roller for imparting a predetermined first stretch to the stretch film. The device includes a second stretching station with a third driven stretch roller for imparting a second predetermined stretch to the stretch film. A sensor is provided in the unwinding station in order to measure a release parameter indicative of where the stretch film releases from the spool. A processor is provided to calculate a first and second force, needed to obtain respectively the first stretch and second stretch, on the basis of the release parameter and an output of the first, second, third torque meters and the unwinding torque meter.