Septic Tank Lid With Offset Access Port
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Solution Overview
Problem
Large openings in septic tanks pose a safety hazard for children, as they can easily fall into the tank, and existing solutions to prevent this, such as using secure fasteners or weighty lids, increase complexity and cost, which is undesirable for plastic tanks competing with concrete tanks.
Innovation Solution
A circular lid with a smaller, offset port that allows passage of a suction hose while preventing child access, secured by hard-to-remove fasteners, reducing the need to remove the entire lid during maintenance and enhancing access for sludge suction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If large openings are provided in the tank lid, then maintenance access and manufacturing access are improved, but child safety deteriorates as children can easily fall through
Solution Approach 1:
The lid is segmented into two functional components: a large outer lid providing maintenance access and a smaller inner port providing controlled access for pumping operations. This segmentation allows the large opening to remain for worker access while the smaller port maintains child safety by being too small for a child to pass through.
Solution Approach 2:
The hazardous function (large opening that children could fall through) is extracted from the essential function (access for maintenance). The smaller port is extracted as a separate access point that provides sufficient access for pumping operations without posing the same safety hazard.
2Object-affected harmful factors
If secure fasteners or weighty lids are used to prevent child access, then child safety is improved, but device complexity and cost increase
Solution Approach 1:
Instead of making the entire lid complex and heavy, the safety function is localized to the smaller port area. The port's limited size inherently provides safety, while the rest of the lid maintains simple construction suitable for plastic tanks.
Solution Approach 2:
The lid design transitions from symmetric large openings to an asymmetric configuration with a smaller, offset port. This asymmetry allows the port to be positioned for optimal pumping access while maintaining safety, without requiring the entire lid structure to be redesigned with complex fastening systems.
3Ease of manufacture
If the port is centered on the lid, then manufacturing is simplified, but access for sludge suction at the far end of the tank is reduced
Solution Approach 1:
The port is deliberately positioned asymmetrically (offset from the center) to optimize its location for pumping operations. This offset positioning allows the suction hose to reach the far end of the tank more effectively, and the asymmetry is incorporated directly into the molded lid design, maintaining ease of manufacture.
Data Source
AI summary
A tank suited for use as a septic tank or for otherwise holding or treating water has a top hatchway large enough to enable an adult person to enter the tank. The hatchway is closed by a lid which has a port with a removable cover, where the port that is large enough to enable through-passage of a suction line for cleaning the tank, but small enough to prevent a child from entering the tank. Preferably the port area is less than 6 percent of the effective area of the lid and the centerline of the port lies at a location which is between 20 to 80 percent of the radius of the lid.