Knock Down Signpost Cable-Tension Self-Righting Mechanism
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Solution Overview
Problem
Current knock down signposts face issues with 'sign flutter' due to wind, limited post height, and damage from impacts, requiring replacement of entire assemblies, and cannot utilize low-cost steel or high-strength posts without compromising rebound energy control.
Innovation Solution
A knock down signpost design featuring a lower body member with a spigot and recess allowing 360° articulation, a flexible cable for pretension and indexing, and a low-spring rating mechanism to minimize impact damage and wind resistance, enabling a stable and self-righting post that can withstand higher winds and impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a lightweight plastic post is used to reduce inertia and enable spring-back mechanism, then the post can be recovered after impact, but the post cannot withstand high wind loading and moves under modest wind loading causing sign flutter
Solution Approach 1:
The post system is divided into separate functional components: a lightweight post member for impact recovery, a lower body member with bearing surface for stability, and a cable-tension mechanism for positioning. This segmentation allows each component to be optimized for its specific function without compromising the others.
Solution Approach 2:
The invention changes the physical parameters of the post system by introducing a cable-tension mechanism that applies controlled force to the post. This allows the lightweight post to be held in position against wind loading without requiring the post itself to be heavy, resolving the contradiction between weight and stability.
2Loss of energy
If a low-spring constant is used to control rebound energy and minimize impact damage, then the post absorbs impact energy effectively, but the post moves under modest wind loading
Solution Approach 1:
The cable-tension mechanism acts as an intermediary between the post and the ground. It provides a controlled connection that allows the post to move during impact (energy absorption) while maintaining stability during normal conditions (wind resistance). The tension means can be adjusted to provide appropriate resistance to wind loading without compromising impact absorption.
3Length of moving object
If the post is made taller to improve visibility, then the sign is more visible to drivers, but the post becomes more susceptible to wind loading and impact damage
Solution Approach 1:
The post system separates the height function from the stability function. The post member can be made tall for visibility, while the lower body member and cable-tension mechanism provide the stability needed to resist wind and impact. This segmentation allows the height and stability requirements to be met independently.
Solution Approach 2:
The cable-tension mechanism serves as an intermediary that connects the tall post to the ground, providing stability without limiting post height. The tension means can be configured to provide appropriate resistance to wind loading on taller posts while allowing impact energy absorption through controlled movement.
4Reliability
If the entire assembly is replaced after impact damage, then the signpost is restored to full functionality, but the repair process is time-consuming and costly
Solution Approach 1:
The post system is segmented into replaceable components, particularly the post member which can be independently replaced. This allows only the damaged portion to be replaced rather than the entire assembly, reducing repair time and cost while maintaining full functionality.
Solution Approach 2:
The design allows the post member to be discarded after impact damage and replaced with a new one, while the lower body member and mounting infrastructure are recovered and reused. This selective replacement approach reduces the cost and time of repairs compared to replacing the entire assembly.
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 design effectively reduces damage from impacts, minimizes sign flutter, and allows for taller posts up to 2.8 meters, enabling the use of steel posts while maintaining stability and ease of replacement, with reduced risk of cable damage and improved wind resistance.
Implementation Method 1
a flexible cable passing through said lower body member and said post member, one end of said cable being retained in one of said lower body member and said post member and said cable being pretensioned by tension means located in the other of said lower body member and said post member to urge said lower body and post members into mutual engagement against said articulation
Data Source
AI summary
There is provided a knock down signpost comprising a post member (6) and a lower body member (10) held together by a spring (3) having a preload when the post is vertical, acting two flat surfaces (8) creating an initial resistance to motion off the horizontal. Two steel cables (114) transmit the force of the spring and are spaced apart which allows the cables to act as a non rotation mechanism. Two round protrusions (16) in the post member (6) locate into two matching clearance holes (14) in the lower body for post alignment. A shock tube (4) is fitted over the cable and internal to the spring to prevent over compression and provides a mechanical stop. As the top assembly is rotated chamfered edges (15) of the post member (6) engage and interlock into an annular groove (13) to act as a pseudo-hinge.