Rotating Tow Hook Assembly with Spring Reset
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Solution Overview
Problem
Existing tow hooks on vehicles concentrate shear forces during towing, potentially leading to stress concentrations and damage, and do not effectively retract to protect against impacts.
Innovation Solution
A tow hook assembly with a flange and extensions that distribute shear forces along a post, and a spring mechanism to automatically reset the hook to an extended position after impact, reducing force transmission and allowing retraction behind the bumper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tow hook is fixed rigidly to the vehicle frame, then the towing force transmission is strong and reliable, but the stress concentration and potential damage to the frame increases
Solution Approach 1:
The tow hook is designed to rotate relative to the base between extended and retracted positions, transforming the rigid fixed connection into a dynamic movable connection. This allows the hook to absorb impact forces through rotation rather than transmitting all stress directly to the frame, resolving the contradiction between reliable force transmission and frame durability.
Solution Approach 2:
The connection between the tow hook and vehicle frame is segmented into multiple components: the base fixed to the frame, the rotatable hook, the post, the flange, and the spring. This segmentation allows different parts to handle different functions - the base provides stable mounting, the hook provides towing capability, and the spring provides shock absorption, thereby protecting the frame from stress concentration.
2Ease of operation
If the tow hook remains in the extended position, then it is always ready for towing operations, but it exposes the vehicle frame to impact damage from objects
Solution Approach 1:
The tow hook automatically transitions between extended (ready for towing) and retracted (protected from impact) positions based on operational needs. The spring mechanism enables this dynamic positioning, allowing the hook to be exposed when needed and retracted when not in use, thus resolving the contradiction between operational readiness and impact protection.
Solution Approach 2:
The spring mechanism automatically returns the tow hook to the extended position after it has been impacted or moved to the retracted position. This self-service feature eliminates the need for manual intervention to reset the hook, maintaining towing readiness while minimizing exposure time to potential impacts.
3Device complexity
If a single post supports the tow hook, then the structure is simple, but the shear force concentration on the post increases
Solution Approach 1:
The single post supporting structure is segmented into multiple load-bearing elements: the post, the flange, and the spring. The flange distributes the load across multiple attachment points on the post, and the spring provides additional load distribution and shock absorption. This segmentation reduces shear force concentration on any single point while maintaining structural simplicity.
Solution Approach 2:
The flange acts as an intermediary element between the tow hook and the post, distributing the shear forces across multiple attachment points. The spring serves as another intermediary that absorbs and distributes impact forces. These intermediary elements reduce the stress concentration on the post while maintaining overall structural simplicity.
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
The assembly effectively distributes towing forces, reducing stress concentrations and automatically resets to minimize damage from impacts, enhancing both towing efficiency and pedestrian protection.
Implementation Method 1
A spring is connected to the post and one of the extensions. The spring positioned to bias the hook toward the extended position.
Data Source
AI summary
An assembly includes a vehicle frame, a base fixed relative to the vehicle frame, and a hook supported by the base and rotatable relative to the base between an extended position and a retracted position. One of the hook or the base has a flange and the other of the hook or the base has a pair of extensions. The flange is between the extensions. A post is fixed relative to the flange and engages both extensions. A spring is connected to the post and one of the extensions. The spring is positioned to bias the hook toward the extended position.