Fastener Attachment Device Backward Ejection Guide
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Solution Overview
Problem
Existing fastener attachment devices are complex, costly, and pose safety risks due to their design, with a high stroke load and the need for frequent replacement of damaged cutters, and they struggle with ejecting connecting bars of varying lengths without disassembling the device.
Innovation Solution
A device with a guide attachment hole for downward ejection of the connecting bar, a simplified feeding mechanism with a rotatable pawl, and a removable needle cap with a scrape pawl for easy cutter placement and removal, allowing for safe operation and adaptability to different fastener assembly lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the connecting bar is ejected backward through the device, then the operator safety is improved, but the device structure becomes more complex
Solution Approach 1:
The device is divided into distinct functional components: a guide attachment with a hole for connecting bar ejection, a pawl mechanism for feeding, and a removable needle cap with scrape pawl. This segmentation allows the ejection function to be implemented through a simple hole in the guide attachment rather than a complex integrated system, resolving the contradiction between safety improvement and structural complexity.
Solution Approach 2:
The harmful connecting bar is extracted and ejected through a dedicated hole in the guide attachment, separating the ejection function from the main device body. This extraction approach allows the connecting bar to be safely removed without requiring complex ejection mechanisms, maintaining device simplicity while improving operator safety.
2Reliability
If a complicated feeding mechanism with multiple parts is used, then the fastener assembly can be fed reliably, but the device complexity increases and stroke load becomes high
Solution Approach 1:
The feeding function is extracted and simplified to a single rotatable pawl mechanism that engages with the fastener assembly. This single-component feeding mechanism eliminates the need for multiple arms and complex structures, reducing device complexity and stroke load while maintaining reliable feeding through the pawl's rotational engagement with the holding pin.
Solution Approach 2:
The pawl is designed with specific local features: a front end that engages the holding pin, a rear end with an arcuate surface that contacts the piston, and an oval slot for pin engagement. These localized structural qualities enable the simple pawl to perform reliable feeding through rotational motion, achieving high reliability without complex overall structure.
3Reliability
If the cutter is fixed to the hollow needle, then the cutting function is stable, but replacing a damaged cutter requires exchanging the entire hollow needle which is uneconomical
Solution Approach 1:
The cutting system is segmented into a removable cutter component and the hollow needle. The cutter can be detached and replaced independently from the needle, allowing economical maintenance where only the damaged cutter is replaced rather than the entire assembly. This segmentation maintains cutting stability through precise positioning features while enabling cost-effective replacement.
Solution Approach 2:
The cutter is designed with dynamic positioning features including an arcuate rear end surface that contacts the needle and engagement structures that allow the cutter to be securely attached yet easily removed. This dynamic design enables the cutter to maintain stable cutting performance when attached while facilitating quick replacement when damaged, resolving the contradiction between stability and ease of replacement.
4Device complexity
If the connecting bar is ejected downward, then the ejection mechanism is simple, but the leading end may hurt the operator and interfere with operation
Solution Approach 1:
Instead of ejecting the connecting bar downward toward the operator, the ejection direction is inverted to backward through the device. The guide attachment includes a hole that directs the connecting bar rearward, away from the operator's hands and face, eliminating the safety hazard while maintaining ejection simplicity through the same basic hole structure.
Data Source
Figure 1A~1C
Figure 2
Figure 3~4
AI summary
A device (10) for attaching fasteners has a casing (11) having a grip (12), a lever (15) supported by the casing rotatably about its upper end and urged forward, a link arm (16) actuated by the rotation of the lever, a piston (19) engaged slidably by the upper end of the link arm, a driving rod (21) slidable with the piston, a hollow needle (22) situated at the leading end of the driving rod and having a slit and a guide (23) formed behind the hollow needle for fitting an assembly (A) of plastic fasteners. A guide attachment (24,25) which can be changed to another is removably held below the assembly fitting guide for guiding a connecting bar in the assembly in the direction of its ejection.