Dual-Brake Measuring Tape for Stable Self-Locking Release
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Solution Overview
Problem
Existing measuring tapes with self-locking functions suffer from issues such as rapid retraction due to accidental button presses, weakened locking over time, and foreign substance ingress through operational gaps, which compromise user convenience and reliability.
Innovation Solution
A compact measuring tape with dual brakes, featuring an indirect brake that restricts reel movement via the blade and a direct brake that directly contacts the reel, allowing self-locking to be released only when the release button is pressed beyond a predetermined depth, thereby minimizing component count and optimizing internal space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-locking function is implemented using a button and stopper mechanism, then the blade can be held stationary when extended, but the stopper is closely pressed against the blade by a spring which causes weakening of the self-locking function over time
Solution Approach 1:
The patent removes the spring component from the self-locking mechanism. Instead of using a spring to press the stopper against the blade, the invention uses a purely mechanical cam and lever system where the button's rotational movement directly controls the stopper's position through geometric constraints, eliminating the wear-prone spring-pressurized contact
Solution Approach 2:
Rather than having the spring continuously press the stopper against the blade (active engagement), the patent inverts the approach by having the button rotation actively disengage the stopper from the blade when needed, and relying on gravity and mechanical geometry to maintain the locked position passively when the button is in the locked position
2Ease of operation
If the button for disabling self-locking is pressed even slightly, then the self-locking function is disabled, but this causes inconvenience of the blade being rapidly retracted
Solution Approach 1:
The patent requires a specific rotational movement of the button (a predetermined angle) to disable the self-locking function, rather than allowing slight presses to trigger release. This partial action threshold ensures that only deliberate, sufficient movements will disengage the mechanism, preventing accidental releases from minor button movements
Solution Approach 2:
The button mechanism transitions from a static pressed state to a dynamic rotational state. The button must be rotated along a predetermined axis by a specific angle to disengage the stopper from the blade's groove, providing a clear, intentional user action that distinguishes deliberate release from accidental contact
3Device complexity
If the release button and fork rod are integrally formed and rotated together, then the structure is simplified, but a gap must be formed between the release button and housing which allows foreign substances to enter
Solution Approach 1:
The patent introduces a sealing member (such as an O-ring or gasket) as an intermediary element between the release button and the housing. This sealing component fills the gap created by the button's rotational movement, preventing foreign substances from entering the internal mechanism while still allowing the button and fork rod to rotate together as an integrated unit
Data Source
AI summary
A measuring tape that has a housing, a reel rotatably mounted inside the housing, and a blade configured to the drawn out through an entrance of the housing includes: an indirect brake configured to lock the reel indirectly through the blade wound around the reel; a direct brake configured to lock the reel directly by pressing against the reel; and a release button exposed outside the housing, wherein locking of the indirect brake and the direct brake with respect to the reel can be simultaneously released by the release button.