Trailer Coupling Tow Hook Cam Track Mechanism

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Solution Overview

Problem

Existing trailer hitches lack a simple and compact design for a retractable and extendable tow hook that does not interfere with driving without a trailer, and they often require complex mechanisms with high wear and large components.

Innovation Solution

A trailer hitch with a tow hook that rotates about at least two non-parallel coupling axes, utilizing a cam track and an adjusting wheel for movement control, which simplifies the design, reduces wear, and minimizes the size of supporting components by using a single cam track on the tow hook and a single adjusting wheel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a retractable tow hook mechanism is implemented, then the tow hook does not interfere with driving without a trailer, but the mechanism becomes more complex and larger in size

Engineering Contradiction:
Improvedriving without trailer interferenceVSAvoidmechanism complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent combines multiple functions into a single integrated mechanism. The adjusting wheel serves both as a drive element and a guiding element, while the cam track integrates both the guiding function and the limiting function into one component rather than separating these functions into multiple components. This merging reduces the overall number of parts and simplifies the mechanism structure.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The cam track serves multiple functions simultaneously: it guides the adjusting wheel during rotation, limits the rotational range to achieve retraction and extension positions, and works with the adjusting wheel to control the tow hook movement. This multi-functionality reduces the need for separate components for each function, thereby reducing complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Device complexity

If a cam track and adjusting wheel mechanism is used, then the design is simplified and component size is reduced, but wear may increase due to contact between moving parts

Engineering Contradiction:
Improvedesign simplicityVSAvoidwear resistance
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The cam track is designed as a curved path on the towing hook that guides the adjusting wheel. The curved geometry allows for smooth rotational movement and distributes contact forces more evenly across the contact surface, reducing localized wear. The spherical bearing head also contributes to smooth movement and even load distribution.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The adjusting wheel acts as an intermediary element between the motor drive and the towing hook movement. It converts rotational motion into controlled movement along the cam track, and the cam track itself acts as an intermediary that guides and limits this movement. This intermediary arrangement allows for controlled contact that reduces wear compared to direct engagement mechanisms.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple coupling axes are implemented for tow hook movement, then the retraction and extension capability is improved, but the mechanism becomes more complex

Engineering Contradiction:
Improvemovement capabilityVSAvoidcoupling mechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges multiple coupling axes into a single integrated system. Instead of providing separate mechanical joints for each rotation axis, the invention uses one rotation axis (the adjusting wheel axis) combined with a cam track geometry that produces the effect of multi-axis movement. The cam track's three-dimensional path guides the adjusting wheel to achieve complex movement sequences including downward tilting, inward pivoting, and upward tilting, all through a single rotational input.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The cam track is designed as a three-dimensional curved path that guides the adjusting wheel through complex spatial movements. By using a cam track with curvature in multiple directions, the mechanism achieves movement along what effectively becomes multiple coupling axes without requiring separate mechanical joints for each axis. This dimensional approach to guiding simplifies the mechanism while maintaining versatility.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 solution provides a compact, low-wear, and efficient mechanism for retracting and extending the tow hook, ensuring it does not interfere with the vehicle's operation without a trailer, while reducing the size and complexity of the hitch's components.

Implementation Method 1

The adjusting wheel is in rolling contact with the cam track in the adjustment engagement

Methodology Applied
Scientific EffectRolling contact: Roller

Implementation Method 2

the transmission of the rotational movement of the adjusting wheel to the cam track and subsequently to the towing hook being able to be based on a frictional engagement of the adjustment wheel and cam track

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 3

the bearing head and the bearing housing form a spherical joint

Methodology Applied
Scientific EffectSpherical joint: Ball

Data Source

PatentEP1894752B2Trailer coupling with extensible and retractable tow hook
Publication Date: 2014.07.09 THULE TOWING SYST
  • EP1894752B2 patent drawingFigure 1~2
  • EP1894752B2 patent drawingFigure 3~4
  • EP1894752B2 patent drawingFigure 5~6

AI summary

The device has a tow hook (1) that projects from a bearing housing and a fastening device. The hook supports the housing and the fastening device around coupling axes such that the hook is selectively movable into an operative position for attaching a trailer or an inoperative position. An adjustable wheel (10) is rotatably supported around an adjusting wheel axis by the housing and the fastening device. The wheel is engaged with the hook at a cam track (9). The hook moves around one of the coupling axes during rotary movement around the wheel axis.