Forming Shoulder for Offset Seam Tubular Bags
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Solution Overview
Problem
The production of tubular bags with laterally offset longitudinal seams is hindered by the complexity of adapting existing bag forming, filling, and sealing machines, as the asymmetrical tube configuration requires oblique welding tool advancement, which is difficult to implement, and the web tends to slide or stretch, complicating the formation and welding process.
Innovation Solution
A device comprising a forming shoulder with a movable longitudinal welding member and counterstay, where the counterstay can extend past or embrace the tube-forming element, and a transverse welding device for compressing the tube, allowing for the creation of tubular bags with laterally offset seams on standard machines by adjusting the forming shoulder geometry and welding tool positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the longitudinal seam is arranged laterally offset in stickpack bags, then the advertising and information space on the bag surface is improved, but the machine complexity and difficulty of implementation increases due to requiring oblique welding tool advancement
Solution Approach 1:
The patent applies asymmetry by positioning the longitudinal seam laterally offset from the center of the bag cross-section. The forming shoulder is designed with asymmetric geometry where the web path lengths from the inlet to the seam location are equalized on both sides, creating a balanced asymmetric configuration that enables lateral seam placement while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs dynamics by making the welding tool movable in a direction that is oblique to the row-like arrangement of stickpacks. The welding tool can advance at an adjusted angle to accommodate the lateral seam position, and the forming shoulder geometry can be modified to optimize web flow and reduce sliding, allowing adaptive adjustment rather than fixed rigid positioning
2Manufacturing precision
If the longitudinal welding member is positioned for lateral seam welding, then the seam location is improved, but the web stability deteriorates due to web sliding and stretching on the forming shoulder
Solution Approach 1:
The patent applies local quality by designing specific regions of the forming shoulder with different geometric characteristics. The shoulder surface includes a first region and a second region with different curvatures or angles, where the web path lengths are equalized. This localized geometric optimization ensures that friction and deformation forces are balanced at critical locations, preventing web sliding while maintaining the lateral seam position
Solution Approach 2:
The patent employs parameter changes by modifying the forming shoulder geometry parameters, specifically the curvatures and angles of the shoulder surface in different regions. By adjusting these geometric parameters, the web path lengths are equalized and the distribution of friction and deformation forces is optimized, thereby stabilizing the web during forming and welding operations
Data Source
AI summary
In a method for producing tubular bags, a forming shoulder for shaping a packaging material web into a tubular bag having a laterally offset longitudinal seam includes a shoulder part and a prism part connected to each other along a shaping edge. Half of the shaping edge facing the incoming packing material web lies in the first and second quadrants of the cross-section of the prism part and the seam is formed in the fourth quadrant. Curvature-free surface lines in the second and fourth quadrants originating from the shaping edge approach each other with increasing distance from the prism part, and the shaping edge angle measured between the surfaces of the shoulder part and the inner face of the prism part decreases from the second to the third quadrant and increases again from the third to the fourth quadrant.