Low Profile Ladder Rack With Coplanar Bar Linkage
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Solution Overview
Problem
Existing ladder rack systems for vehicles increase wind resistance and violate height restrictions at job sites due to their elevated height profile, as the stationary and movable bars are stacked during transport, leading to inefficiencies and access issues.
Innovation Solution
A modified 4-bar linkage system where the stationary and movable bar members are positioned side-by-side with coplanar top surfaces when closed, reducing the overall height of the ladder rack by over 50%, and incorporating a connecting rod and hydraulic cylinder to facilitate the transition from a rooftop to a side-mounted position, minimizing wind resistance and accommodating height-restricted areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the stationary and movable bars are stacked during transport, then the ladder rack can effectively carry loads on the vehicle roof, but the overall height increases resulting in greater wind resistance and noise
Solution Approach 1:
The patent repositions the movable bar from a vertical stacking arrangement to a horizontal side-by-side arrangement with the stationary bar. This dimensional change allows the top surfaces of both bars to be coplanar during transport, reducing the overall height profile while maintaining load carrying capability on the vehicle roof.
Solution Approach 2:
The patent employs a 4-bar linkage mechanism with rigid links that enables dynamic reconfiguration of the bar positions. The linkage allows the movable bar to transition between a coplanar position during transport and a lowered position for loading/unloading, optimizing both aerodynamic efficiency and operational functionality.
2Device complexity
If the stationary and movable bars are stacked during transport, then the ladder rack structure is compact, but the height above the vehicle roof violates height restrictions at job sites like parking garages
Solution Approach 1:
The patent changes the spatial arrangement from vertical stacking to horizontal alignment, placing the movable bar side-by-side with the stationary bar. This creates a coplanar top surface configuration that reduces overall height to comply with parking garage and job site height restrictions while maintaining structural functionality.
Solution Approach 2:
The 4-bar linkage mechanism provides dynamic adaptability, allowing the rack to maintain a low coplanar profile during transport and then lower the movable bar when approaching height-restricted areas or during loading operations, ensuring compliance with various height constraints.
3Object-affected harmful factors
If the movable bar is positioned coplanar with the stationary bar, then wind resistance and noise are reduced, but the mechanism requires additional components like connecting rods and hydraulic cylinders
Solution Approach 1:
The patent integrates multiple functions into unified components. The connecting rod serves both as a structural element and as part of the 4-bar linkage mechanism. The hydraulic cylinder is positioned to provide both actuation force and structural support, reducing the need for separate mounting brackets and adjustment mechanisms.
Solution Approach 2:
The hydraulic cylinder is designed to perform multiple functions: it acts as the actuating force for the 4-bar linkage, provides structural support for the movable bar, and can serve as a mounting point for additional equipment. The connecting rod simultaneously maintains structural integrity and enables the kinematic motion required for the coplanar positioning.
Data Source
AI summary
A ladder rack for a motor vehicle similar to what is shown in U.S. Pat. No. 6,764,268, but differing therefrom in that the top surfaces of the stationary bar member and the movable bar member are coplanar and in a side-by-side relationship when the load being carried is atop the vehicle's roof rather than being stacked, one-above-the-other, as in the prior art. As such, the ladder rack of the present invention exhibits a reduced height profile.