Strapping Machine Torque Control via Adjustable Speed Drive
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Solution Overview
Problem
Existing strapping machines face challenges in consistently and effectively tensioning straps around loads due to mechanical wear and variability in tension control, particularly with mechanical clutches and pre-determined voltage methods.
Innovation Solution
A tension control system incorporating a motor assembly, adjustable speed drive, and a manually adjustable voltage divider, allowing for controlled torque application through a programmable logic controller to adjust torque based on load requirements, ensuring consistent strap tension without clutch slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical clutch is used to control strap tension, then the strapping machine can achieve strap tensioning functionality, but the clutch experiences wear and produces variability in tension applied to the strap material
Solution Approach 1:
The patent replaces the mechanical clutch system with an electrical control system. The adjustable speed drive receives a reference signal and controls motor torque electrically, eliminating the mechanical clutch and its associated wear problems. This substitution of mechanical components with electrical/control components directly resolves the contradiction between reliability and manufacturing durability.
2Productivity
If a predetermined voltage is applied to the drive clutch, then the tensioning process can be controlled, but the tension applied to the strap material varies and requires predetermined time for clutch slippage
Solution Approach 1:
The patent implements a dynamic tension control system where the adjustable speed drive continuously adjusts motor torque based on a reference signal. Instead of using predetermined voltage with fixed clutch slippage time, the system dynamically controls the motor assembly to apply precise torque, eliminating the need for predetermined time delays and achieving both fast and accurate tensioning.
Solution Approach 2:
The system uses a reference signal to control the adjustable speed drive, creating a feedback-based control mechanism. The drive monitors and adjusts motor output based on the reference signal, ensuring precise tension control without the variability and time delays associated with predetermined voltage methods and mechanical clutch slippage.
3Device complexity
If the same motor is used for both feeding and tensioning the strap material, then the system can be simplified, but the motor must reverse direction and the clutch slips during tensioning
Solution Approach 1:
The patent replaces the mechanical clutch that must slip during tensioning with an electrical torque control system. The adjustable speed drive controls the motor assembly to apply appropriate torque in both forward and reverse directions without requiring clutch slippage. This eliminates the reliability issue of clutch wear while maintaining the simplified single-motor configuration.
Data Source
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AI summary
A strapping machine is provided to feed a strap around a load, position, tension and seal the strap around the load. The strapping machine includes a surface to support the load in the strapping machine; a strap chute to carry a strap around the load and release the strap from the strap chute; a motor assembly to convey the strap around the strap chute, retract the strap material around the load, and tension the strap around the load; and an adjustable speed drive capable of receiving a first reference signal and a second reference signal, and configured to actuate the motor assembly to apply a first amount of torque to the strap when receiving the first reference signal and to apply a second amount of torque to the strap when receiving the second reference signal. The strapping machine also includes a controller configured to operate the adjustable speed drive in a first mode while conveying the strap around the strap chute and retracting the strap material around the load, and a second mode while tensioning the strap around the load. In the first mode, the adjustable speed drive actuates the motor assembly to apply the first amount of torque to the strap, and in the second mode, the adjustable speed drive actuates the motor assembly to apply the second amount of torque to the strap.