Slidably Retractable Tow Bar for Space-Saving Dolly Design

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Solution Overview

Problem

Conventional pivoting tow bars on dollies occupy valuable space during transit when not in use and detaching them increases complexity and reduces robustness and user-friendliness.

Innovation Solution

A slidable and pivotable tow bar mechanism that retracts completely under the load carrying surface, minimizing external dimensions during individual transport and storage, using a guide track and pivoting mechanism configured to pivot about a horizontal axis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the tow bar is pivoted in an upright position to save space, then the space occupation is reduced, but the tow bar still occupies valuable space during transit and when loaded onto a trailer

Engineering Contradiction:
Improvespace occupationVSAvoidoperational convenience
Core Design Contradiction:
Area of stationary objectVSEase of operation

Solution Approach 1:

The tow bar is nested within the chassis structure by retracting it completely under the load carrying surface. The guide track is integrated into the chassis underside, and the tow bar slides within this track to achieve a compact nested configuration that minimizes external dimensions while maintaining operational capability.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The tow bar transitions from a static pivoting mechanism to a dynamic slidable-retractable mechanism. It can be easily extended to the towing position when needed and retracted to the stowed position by sliding along the guide track, providing adaptability between operational and storage states without the space occupation issues of conventional pivoting bars.

Inventive Principle:
Principle #15Dynamics

2Area of stationary object

If the tow bar is made detachable to solve space issues, then space occupation is reduced, but the device complexity increases and robustness decreases

Engineering Contradiction:
Improvespace occupationVSAvoidcoupling complexity
Core Design Contradiction:
Area of stationary objectVSDevice complexity

Solution Approach 1:

The tow bar is merged with the chassis as an integrated component rather than a detachable attachment. The slidable connection combines the functions of the tow bar and its mounting structure into a unified system, eliminating the need for separate couplings and hitch mechanisms while maintaining both robustness and space efficiency.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The guide track serves multiple functions: it guides the tow bar during extension and retraction, provides structural support, and enables the transition between towing and stowed positions. This multi-functional design eliminates the need for separate coupling mechanisms, reducing overall device complexity while maintaining robustness.

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

3Area of stationary object

If the tow bar is made detachable to solve space issues, then space occupation is reduced, but separate handling is required which reduces user-friendliness

Engineering Contradiction:
Improvespace occupationVSAvoiduser-friendliness
Core Design Contradiction:
Area of stationary objectVSEase of operation

Solution Approach 1:

The tow bar and chassis are merged into an integrated system where the tow bar is permanently attached but retractable. This eliminates the need for users to detach and reattach separate components, maintaining user-friendliness while achieving space savings through the retracted configuration.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The dynamic slidable connection allows the tow bar to be easily extended or retracted by a single user without requiring detachment tools or complex assembly operations. The mechanism provides smooth transition between positions while maintaining permanent attachment, combining space efficiency with operational simplicity.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP2778015B1Dolly with slidably retractable tow bar
Publication Date: 2018.10.10 K HARTWALL OY AB
  • EP2778015B1 patent drawingFigure 1
  • EP2778015B1 patent drawingFigure 2
  • EP2778015B1 patent drawingFigure 3

AI summary

The present invention provides an improved dolly which is not only effective in terms of return logistics but also simple in design and easy to use. The novel dolly (100) includes a chassis (110) which has an upper side (111) with a load carrying surface (113), and an opposing underside (112). The dolly (100) also includes a tow bar (120) which is arranged slidably to the underside (112) of the chassis (110) via a pivoting mechanism (130) which is configured to pivot the tow bar (120) about a horizontal axis.