Manhole Frame Handholds for Access Area Expansion
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Solution Overview
Problem
Existing manhole construction methods often compromise access safety due to the placement of step rungs, which reduce the available space for workers, and require costly and time-consuming brick or concrete filling for adjustability.
Innovation Solution
Incorporating handholds into the manhole frame, either by casting them into the frame, welding, or making them mechanically attachable/detachable, with options for vertical or horizontal orientation and flexibility using materials like loose link chain or wire rope, to provide secure access without the need for extensive protrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If step rungs are placed in the manhole adjustment area to continue the ladder, then continuous ladder access is provided, but the available access area for workers is reduced
Solution Approach 1:
The invention extracts the handhold function from the traditional step rung design. Instead of requiring full step rungs embedded in the adjustment area, the patent uses smaller handholds that can be attached to the manhole frame, removing the need for extensive embedding while maintaining access functionality. This reduces the space occupation in the adjustment area.
Solution Approach 2:
The access system is segmented into two types of elements: step rungs for foot placement and handholds for hand gripping. This segmentation allows handholds to be positioned without requiring the same embedding depth and space as full step rungs, thereby preserving more access area while maintaining ladder continuity.
2Length of stationary object
If handholds are placed in the manhole frame adjustment area, then the distance from top of frame to first step rung can be extended to 26 inches, but handholds require embedding space similar to step rungs
Solution Approach 1:
The invention extracts the essential gripping function from the step rung design, creating a simplified handhold that attaches to the frame without requiring the same embedding depth (3 inches) and extension (4 inches) as traditional step rungs. This allows extended spacing while minimizing embedding space occupation.
Solution Approach 2:
Different elements serve different functions with different spatial requirements: step rungs provide foot placement with full embedding, while handholds provide gripping support with minimal attachment. This local differentiation allows optimized space usage in the adjustment area.
3Adaptability or versatility
If traditional brick or concrete filling is used in the adjustment area, then frame adjustability is achieved, but the process is expensive and time-consuming
Solution Approach 1:
The handholds are designed to be pre-fabricated and attached to the manhole frame before installation, or easily attached afterward. This preliminary preparation eliminates the need for time-consuming on-site brick laying or concrete pouring, while maintaining frame adjustability through the flexibility of handhold placement.
Solution Approach 2:
The invention replaces expensive and permanent brick/concrete filling with simpler, more flexible handhold attachments that can be installed quickly and removed if needed. This substitution reduces both material costs and installation time while maintaining the required adjustability.
Data Source
AI summary
A manhole frame having one or more handholds near the entrance to the manhole so that the ladder rungs can be made lower and the access space at the entrance to the manhole thereby increased. The handhold can be cast into the cover-supporting lip, or can be a movable handle which is below the level of the manhole when not in use or extended above ground level when in use.