Self-Energizing Gripper for Strapping Machines
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Solution Overview
Problem
Conventional self-energizing grippers for strapping machines are sensitive to strap thickness, deform the strap due to a small contact area, and fail to securely grip thicker straps, requiring adjustments and potentially causing refeeding issues.
Innovation Solution
A self-energizing gripper with a parallelogram link arrangement and a flat, planar gripping surface that maintains contact area parallel to the strap, using a biasing element and cam mechanism to ensure secure gripping without deformation across varying strap gauges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a curved gripping surface is used to increase contact area, then the contact area between gripper and strap is increased, but the strap is deformed and the gripper becomes sensitive to strap thickness
Solution Approach 1:
Instead of using a curved gripping surface that conforms to the strap, the patent uses a flat gripping surface that maintains a constant distance from the pivot point. This inverted approach prevents strap deformation while still providing adequate contact area through the flat surface geometry.
Solution Approach 2:
The patent changes the geometric parameters of the gripping surface from curved to flat, and adjusts the pivot point location to optimize the gripping action. This parameter change eliminates strap deformation while maintaining effective contact area through the flat surface design.
2Adaptability or versatility
If the pivot location is adjusted for different strap gauges, then the gripper can properly self energize with different strap thicknesses, but the device complexity increases
Solution Approach 1:
The patent designs a universal gripper with a fixed pivot point and flat gripping surface that can accommodate multiple strap thicknesses without requiring adjustment. The geometry is designed to work across a range of strap gauges, eliminating the need for complex adjustment mechanisms.
Solution Approach 2:
Instead of adjusting the pivot location for different strap gauges, the patent uses a fixed pivot point with optimized geometry that naturally adapts to different strap thicknesses. The flat gripping surface and pivot positioning create a universal solution that works across varying strap parameters without mechanical adjustment.
3Force
If a single pivot lobed element is used for self-energizing grip, then the gripper can capture the strap with mechanical advantage, but the contact area is small and the gripper is sensitive to strap thickness
Solution Approach 1:
The patent inverts the conventional approach by using a flat gripping surface instead of a curved one, and positioning the pivot point to create mechanical advantage while maintaining a larger contact area. This inversion resolves the trade-off between gripping force and contact area.
Solution Approach 2:
The patent transitions from a point-contact or line-contact gripping surface to a surface-contact geometry with the flat gripping element. This dimensional change increases the contact area while the pivot point placement maintains the mechanical advantage for self-energizing action.
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 gripper effectively secures straps of varying thickness without deformation, maintaining a larger contact area and reducing sensitivity to strap gauge variations, ensuring reliable operation and efficient refeeding.
Implementation Method 1
a biasing element operably connected to the links to urge the gripping element to the closed gripper position
Implementation Method 2
A cam element can be mounted to one of the links such that contact with the cam urges the gripping element to the open gripper position
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A self-energizing gripper (12) is configured for use in a strapping machine (10) that includes a rigid surface (42) along which a strapping material (5) traverses and against which the strapping material is clamped. The self-energizing gripper (12) includes first (38) and second (40) links mounted at respective first ends to the strapping machine (10) for pivotal movement and a gripping element (34) pivotally mounted to respective second ends (48, 50) of each the first (38) and second (40) links. The gripping element includes a substantially planar gripping element surface (36). The first (38) and second (40) links are mounted to the gripping element (34) for pivotal movement of the gripping element along an arcuate path toward and away from the rigid surface (42) and the gripping element (34) surface remains parallel as the gripping element moves along the arc between an open gripper position and a closed gripper position.