Knife Connecting Device Automatic Blade Retraction Mechanism
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Solution Overview
Problem
Existing knives with blade carriers that move between safety and cutting positions lack a simple yet safe mechanism for automatic return to the safety position after use, potentially leading to accidental injuries.
Innovation Solution
A knife design featuring a connecting device with joints that allows the blade carrier to be moved from a safety to a first cutting position and then to a second cutting position, where it can automatically return to the safety position due to a restoring force when the actuating device is no longer actuated, utilizing a combination of translational and rotational movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the blade carrier is moved to a first cutting position by the actuating device, then the blade protrudes for cutting, but the blade carrier cannot automatically return to the safety position when the actuating device is released
Solution Approach 1:
The connecting device transitions from a rigid connection in the first cutting position to an unstable intermediate position that allows automatic return. The distance between joints changes dynamically: in the first cutting position the joints are at a first distance that maintains the blade carrier in the cutting position, but when the actuating device is released, the connecting device moves to an intermediate position where the joints are at a second distance, allowing the blade carrier to return to the safety position automatically.
Solution Approach 2:
The connecting device acts as an intermediary mechanism between the actuating device and the blade carrier. It includes intermediate positions that mediate the transition between the cutting position and safety position. The connecting device with its variable joint distances creates an unstable intermediate state that facilitates automatic return while maintaining controlled cutting operation.
2Stability of the object's composition
If a support element is used to hold the blade carrier in the cutting position, then the blade remains stable during cutting, but the construction becomes more complex
Solution Approach 1:
Instead of a fixed support element, the patent uses a dynamic connecting device where the distance between joints varies. The connecting device provides stability when needed (at the first distance in cutting position) and enables automatic return when the actuating device is released (at the second distance). This dynamic approach replaces complex static support structures with a simpler variable-geometry mechanism.
Solution Approach 2:
The connecting device changes its geometric parameter - the distance between the first joint and second joint. By varying this distance between a first distance (for stable cutting position) and a second distance (for automatic return), the system achieves both stability and simplicity without requiring additional support elements.
3Productivity
If the connecting device allows the blade carrier to move between positions, then the knife is functional, but accidental injuries may occur if the blade does not retract
Solution Approach 1:
The connecting device is designed with an unstable intermediate position that preemptively counteracts the risk of accidental injury. When the actuating device is released, the connecting device automatically transitions to the intermediate position, which causes the blade carrier to retract to the safety position before any accidental contact can occur. This preliminary anti-action ensures the blade is retracted as soon as cutting is not actively being performed.
Solution Approach 2:
The connecting device serves as a safety intermediary that mediates between the actuating device and the blade carrier. The unstable intermediate position acts as a safety buffer, ensuring that when the actuating device is released, the blade carrier automatically returns to the safe position, preventing accidental injuries while maintaining full cutting functionality when needed.
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
The knife (10) has a connecting device (17) fixedly connected to a blade support (12) by a pivot (G2) and to an actuating element (19) of an actuator (16) by another pivot (G4). The pivots include respective spacings in respective orientations of the connecting device. The blade support is arranged in cutting position and safety position in respective orientations of the connecting device when the actuator is found in actuating position. A blade (13) projects partially out of a housing (11) in cutting position.