Automatic Strap Retracting Mechanism for Wheel Restraints
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Solution Overview
Problem
Existing wheel restraint devices require manual and slow retraction of the fastening strap after use, complicating the operation and reducing efficiency.
Innovation Solution
An automatic strap retracting mechanism with a rotatably connected reel, ratchet, and locking piece driven by a coil spring, allowing the reel to automatically wind the strap back onto the reel without manual intervention, and a locking mechanism that prevents the strap from loosening or retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manual retraction of the fastening strap is used, then the device structure is simple, but the operation is complicated and retraction speed is very slow
Solution Approach 1:
The coil spring is pre-compressed during the strap extension phase, storing elastic potential energy. When retraction is needed, this pre-stored energy automatically drives the reel to wind the strap back, eliminating the need for manual retraction effort and significantly increasing retraction speed.
Solution Approach 2:
The system uses its own operational phases to charge the spring during extension, and the spring automatically performs the retraction function without external intervention. The mechanism serves itself by converting the extension phase into energy storage and the retraction phase into energy release, making the system self-operating.
2Reliability
If a ratchet locking mechanism is added to prevent strap loosening, then the strap security is improved, but the device complexity increases
Solution Approach 1:
The locking function is merged with the existing ratchet structure that already exists in conventional retractors. The pawl-ratchet mechanism is integrated into the reel assembly, allowing the strap to be securely locked in the extended position without requiring separate locking components, thus maintaining simplicity while improving reliability.
3Ease of operation
If an automatic retraction mechanism with spring is implemented, then the operation becomes easier and faster, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The coil spring serves multiple functions: it provides the driving force for automatic retraction, stores energy during the extension phase, and can be integrated with the reel mounting structure. This multi-functionality reduces the need for separate components, simplifying the overall manufacturing process despite the added automation capability.
4Reliability
If the locking piece includes both pawl and locking rod with specific angles, then the strap can be securely locked during extension, but the device complexity increases
Solution Approach 1:
The locking piece employs asymmetric geometry with the pawl and locking rod positioned at specific non-symmetric angles relative to the reel axis. This asymmetric design allows the components to engage with the ratchet teeth in specific directions only, providing reliable one-way locking during extension while maintaining a compact and simple overall structure.
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
Enables quick and easy operation of both retracting and pulling out the fastening strap, reducing manual effort and increasing efficiency by utilizing a coil spring to automatically rotate the reel and a locking mechanism that prevents unwanted strap movement.
Implementation Method 1
a coil spring (5) connected to the reel (2) and capable of driving the reel (2) to rotate in the direction of strap tightening to wind in and retract the fastening strap (21)
Implementation Method 2
a ratchet (3) fixed onto the reel (2), the ratchet tooth surfaces of which consist of a locating surface (31) used to lock the direction of strap loosening
Implementation Method 3
When the pawl detaches from the locating surface and the fastening strap is pulled out, the locking piece can swing to allow the locking rod to abut on the guiding surface
Data Source
Figure 1
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Figure 3
AI summary
In the present automatic strap retracting mechanism for wheel restraint devices, the wheel restraint device comprises a shell (1), and a reel (2) is rotatably connected inside the shell. A ratchet (3) is fixed to the reel, and the tooth surface of the ratchet consists of a locating surface (31) and a guiding surface (32). A locking piece(4) is also hinged to the shell, and the locking piece has a pawl (42). The automatic strap retracting mechanism comprises a coil spring which is connected to the reel and can drive the reel to rotate in the direction of strap retracting and wind in and retract the fastening strap. The locking piece also comprises a locking rod (43). When the pawl detaches from the locating surface and the fastening strap is pulled out, the locking piece can swing to allow the locking rod to abut on the guiding surface.