Scissor Catch Strap Layout for Precise Opening Limitation
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Solution Overview
Problem
Conventional scissors with compact design and high cutting capacity face challenges in accurately limiting the opening width to ensure continuous cutting performance, as the proximity of pivot points reduces available space for end stops, leading to imprecise and high-effort opening limitation.
Innovation Solution
A catch strap is designed as an opening limiter positioned outside the scissor head and pivot axes, allowing precise definition of the maximum opening width by articulating it on the holding device, which secures the closed position and enables high cutting performance with minimal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pivot points of scissor arms and handles are positioned close together to achieve compact design, then the overall size and weight are reduced, but the available space for opening limitation devices is greatly reduced or eliminated
Solution Approach 1:
The catch strap is positioned on a side relative to the second pivot axis that faces away from the side containing the first pivot axis, utilizing the lateral dimension rather than the longitudinal dimension. This dimensional repositioning allows the opening limitation function to be implemented without increasing the overall length of the scissors, thereby maintaining compactness while providing necessary space for the limitation mechanism.
Solution Approach 2:
The catch strap serves multiple functions: it acts as an opening limiter for the scissor head, sets the maximum opening width, and maintains structural integrity. By combining these functions into a single component positioned strategically, the design avoids adding separate devices that would increase overall size, thus resolving the contradiction between compactness and functional completeness.
2Manufacturing precision
If conventional end stops are used for opening limitation, then the maximum opening width can be restricted, but the precision and ease of setting the end stop are compromised
Solution Approach 1:
The catch strap's geometry is specifically designed with parameters (length, position relative to pivot axes, articulation points) that directly determine the maximum opening width. By adjusting these geometric parameters during manufacturing, precise opening limitation is achieved without requiring complex adjustment mechanisms, thereby maintaining both precision and ease of manufacture.
Solution Approach 2:
The catch strap automatically limits the opening width through its geometric design and articulation mechanism, without requiring external adjustment devices or complex setting procedures. The maximum opening width is inherently defined by the strap's position and dimensions, making the system self-regulating and eliminating the need for separate end stop setting operations.
3Reliability
If the scissor head is opened too far without proper limitation, then the pretension between cutting edge and counter blade is lost, but implementing limitation devices increases structural complexity
Solution Approach 1:
The catch strap is articulated to allow dynamic movement during normal operation while automatically engaging to limit the opening width. This dynamic design enables the strap to accommodate the cutting motion and maintain pretension during operation, while automatically preventing excessive opening that would lose pretension, thus ensuring reliability without adding static structural complexity.
Solution Approach 2:
The catch strap acts as an intermediary element between the scissor head and the handles, mediating the opening motion. It allows necessary movement for cutting operations while intervening to prevent excessive opening, thereby maintaining cutting performance through pretension without requiring direct complex limitation mechanisms on the cutting edges themselves.
Data Source
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AI summary
The invention relates to scissors comprising a cutting head (48) having a first scissor leg (34) and a second scissor leg (42), which are pivotably hinged around a first swivel axis (64) and a holding apparatus (12) having a first handle (14) and a second handle (16), which are pivotably hinged around a second swivel axis (66), wherein the first scissor leg is pivotably hinged to the first handle around a third pivot axis (68) and the second scissor leg is pivotably hinged to the second handle around a fourth pivot axis (70), wherein a sprag (80) is provided, which is arranged on one handle and acts on the other handle, wherein the sprag is designed as an opening limiter for the cutting head.