Tension Head Cam Biasing for Steel Strapping Tension Control
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Solution Overview
Problem
Existing strapping machines lack a mechanism to effectively relax strap tension during the welding cycle, which is necessary for proper welding and subsequent operations, and do not provide a way to reset the tension head for subsequent strapping cycles.
Innovation Solution
A self-actuating tension head with a drive wheel, tension wheel, and pinch wheel configuration that allows for controlled tensioning and rollback of the strap, utilizing a cam and biasing element to manage the energizing angle and normal force, enabling precise tension release and repositioning for welding and feeding cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tension head maintains constant tension on the strap during the strapping cycle, then the strap remains securely tensioned for sealing, but the welding cycle cannot properly function because the strap tension must be relaxed a predetermined distance
Solution Approach 1:
The tension head transitions from a static constant-tension design to a dynamic system that automatically adjusts tension based on operational phase. The cam mechanism converts rotational motion into controlled linear displacement, enabling the tension wheel to move between engaged and disengaged positions relative to the pinch wheel, thereby providing both tension maintenance and relaxation functions
2Force
If the tension head provides strong engagement between the tension wheel and pinch wheel for effective tensioning, then the strap is properly tensioned, but the tension head cannot reset to the initial position for subsequent operations
Solution Approach 1:
The cam mechanism implements periodic action by converting continuous rotation into cyclic engagement and disengagement of the tension wheel with the pinch wheel. During the tensioning phase, the cam profile maintains strong engagement, and during the reset phase, it automatically disengages the wheels, enabling repeated operational cycles without manual intervention
3Force
If the energizing angle between the pivot arms is maintained at a large value for strong wheel engagement, then tensioning force is maximized, but the strap cannot be rolled back for welding operations
Solution Approach 1:
The cam mechanism dynamically changes the energizing angle parameter throughout the operational cycle. During tensioning, the angle is maintained at an optimal value for maximum force transmission, and during rollback, the angle is reduced to allow the tension wheel to disengage and permit strap movement, thereby controlling both force magnitude and strap displacement
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
Enables precise tension control during strapping and welding cycles, allowing for proper strap alignment and feeding, while maintaining the tension head in the correct position for subsequent operations, ensuring efficient and accurate strapping machine performance.
Implementation Method 1
a biasing element, such as a spring, that is configured to bias the cam
Implementation Method 2
A cam is mounted to the tension wheel and is configured for engagement with a cam follower to rotate the first pivot axis to move the tension wheel out of engagement with the pinch wheel
Implementation Method 3
The tension wheel can include a high friction surface
Data Source
AI summary
A self-actuating tension head for a strapping machine for feeding a steel strapping material around a load, tensioning the strapping material and sealing the strapping material to itself has a tension wheel biasing element. The tension head includes a body defining a strap path therethrough, a drive wheel, a tension wheel and a pinch wheel. The strap path extends between the tension wheel and the pinch wheel. The drive wheel is a fixed distance from the tension wheel. The drive and tension wheels are operably engaged with one another. A pivoting link operably connects the drive and tension wheels. The link pivots about the drive wheel axis of rotation. A cam is operably mounted to the tension wheel, and engages a cam follower to pivot the link to move the tension wheel into and out of engagement with the pinch wheel. The tension wheel biasing element cooperates with the cam to maintain the cam in a position relative to the cam follower.