Retractable Pavement Marker With Dynamic Impact Absorption
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Solution Overview
Problem
Existing depressible reflective pavement markers are prone to damage from traffic and snowplow impacts, and their installation methods do not adequately prevent damage or facilitate maintenance.
Innovation Solution
A resilient pavement marker system with a housing embedded in the pavement, a piston carrying a replaceable reflector assembly, and a resilient biasing member, secured by a retainer with lead-in threads and a compliant adhesive forming a mechanical adhesive lock, which allows the marker to retract and absorb impacts while ensuring easy maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid surface mounted marker is used, then the marker is simple to install, but it is highly susceptible to damage from vehicle tires and snowplow blades
Solution Approach 1:
The marker employs a movable reflector assembly that can dynamically change position between protruding above the pavement surface for visibility and retracting below the surface to avoid damage. The biasing member enables automatic movement between these states based on external forces, transforming a static structure into a dynamic one that adapts to traffic and snowplow conditions.
Solution Approach 2:
The marker is divided into separable components including the housing, movable reflector assembly, piston, and biasing member. This segmentation allows the reflector assembly to be independently replaced when damaged, simplifying maintenance while protecting the main housing structure from damage.
2Reliability
If a retractable marker with beveled surface is used, then impact resistance is improved, but the marker still suffers damage from repeated blows and requires complex maintenance procedures
Solution Approach 1:
The beveled upper surface of the housing works with the movable reflector assembly to create a dynamic impact response. When snowplow blades or vehicle tires apply force, the reflector assembly automatically depresses along the beveled plane and retracts into the housing, converting harmful impact forces into useful retraction motion that protects the reflector.
Solution Approach 2:
The reflector assembly is made separable from the housing through the removable piston and retainer mechanism. This allows damaged reflectors to be quickly replaced by simply removing the piston and retainer, eliminating the need to replace the entire housing assembly and significantly reducing maintenance time and complexity.
3Ease of manufacture
If adhesive bonding alone is used to secure the housing, then installation is simple, but the housing can be extracted by road traffic impacts and vibrations
Solution Approach 1:
The solution combines two retention mechanisms: adhesive bonding and mechanical interlocking. The contoured outer surface of the housing works with the contoured inner surface of the opening to create a mechanical adhesive lock that prevents housing extraction, while adhesive provides additional bonding strength. This combination ensures the housing remains securely installed despite traffic impacts and vibrations.
4Strength
If fine pitch threads are used for the retainer, then thread engagement is sufficient, but the number of rotations required for fastening is excessive
Solution Approach 1:
The retainer employs different thread characteristics in different zones: lead-in threads with coarser pitch for rapid initial engagement and positioning, followed by finer pitch threads for secure final fastening. This local differentiation of thread quality allows the majority of the fastening process to occur quickly through the coarse lead-in section, reducing overall maintenance time while maintaining adequate engagement strength.
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 system effectively withstands traffic and snowplow impacts, reduces maintenance needs, and minimizes pavement spalling, providing reliable and cost-effective delineation of traffic lanes with quick and easy repair options.
Implementation Method 1
a resilient biasing member urging the piston upwardly to raise the reflector assembly above the road surface
Implementation Method 2
An adhesive bonds the housing within the opening in the pavement
Implementation Method 3
The adhesive is compliant and energy absorbing, to mitigate spalling around the edge of the opening in the pavement
Data Source
AI summary
A retractable, reflective pavement marker for delineating traffic lanes of roadways and a method of installing the same that provides improved protection from potentially damaging vehicle tires, snowplows, and environmental conditions. The marker incorporates a reflector assembly mounted to a piston that is depressible within a housing. A biasing member returns the reflector assembly to its normal position above the road surface. A compliant adhesive cooperates with an adhesive lock formed between the housing and the opening to ensure that the marker is reliably retained within the pavement. The adhesive and a chamfered opening prevent pavement spalling due to external forces. The housing includes a removable retainer through which the piston is reciprocally received. The retainer includes a plurality of coarsely pitched lead-in threads that cooperate with a threaded housing. Multiple lead-in threads provide sufficient thread engagement, while substantially decreasing the number of rotations to achieve full engagement.