Composite Worm Gear Fastener for Low-Cost Utility Cover Locking
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Solution Overview
Problem
Existing worm gears for utility covers are typically made of metal, which are expensive, difficult to manufacture, and require precise machining, and may not be used efficiently due to low cycle usage, while also being unnecessarily strong for infrequent operations.
Innovation Solution
A fastener system using a non-metallic material, such as nylon, with a tapered worm gear and bolt design that can accommodate various flange sizes and shapes, allowing for universal compatibility and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic materials are used for worm gears, then strength and durability are improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent replaces expensive metallic worm gears with inexpensive non-metallic (plastic) worm gears that are designed to be replaced periodically. The plastic worm gear serves its function for a limited number of cycles (e.g., 100-1000 cycles) and is then discarded and replaced, eliminating the need for expensive precision machining of metal parts while maintaining adequate performance for the application's low-cycle usage pattern
Solution Approach 2:
The patent changes the material parameter from metal to plastic, fundamentally altering the properties of the worm gear. This material substitution allows for simpler manufacturing processes (injection molding vs. precision machining), reduced cost, and adequate performance for infrequent cycling applications, directly resolving the contradiction between strength requirements and manufacturing complexity
2Reliability
If worm gears are precisely machined to meet specific tolerances, then reliability is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent eliminates the need for precise machining by using plastic worm gears that are molded with adequate tolerances for low-cycle applications. These components are produced quickly through injection molding and are designed to be replaced after a limited service life, thereby achieving reliability for the intended usage pattern without investing time in precision machining operations
Solution Approach 2:
The patent changes the manufacturing process parameter from precision machining to injection molding, and adjusts the tolerance parameter to be less stringent. This combination allows for rapid production of functional components that meet the reliability requirements for infrequent cycling, directly resolving the contradiction between reliability and manufacturing time
3Adaptability or versatility
If worm gear outer width is increased to engage smaller ledges, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent designs the plastic worm gear with a universal geometry that can engage with ledges of various sizes. The worm gear features a standardized outer width and helical tooth profile that accommodates different ledge dimensions through elastic deformation and friction-based engagement, allowing a single design to serve multiple applications without increasing overall device complexity
4Strength
If metallic fasteners are used for secure closure, then strength is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs composite construction by integrating the worm gear and bolt as a unified plastic assembly produced through injection molding. This composite approach eliminates the need for separate metal components and complex metal-fastening mechanisms, achieving adequate strength for low-cycle applications while dramatically reducing manufacturing cost through single-material, single-process production
Solution Approach 2:
The patent replaces expensive metallic fasteners with inexpensive plastic alternatives that are designed for limited-service-life applications. The plastic worm gear and bolt assembly provides sufficient holding strength for infrequent cycling and is replaced as a low-cost unit when wear occurs, eliminating the need for expensive metal components
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 non-metallic fastener system provides cost-effective, efficient, and easy assembly, accommodating different flange sizes and shapes, reducing manufacturing complexity and costs, and ensuring secure closure of utility covers.
Implementation Method 1
The helical portion on an outer surface of the body that extends at least partially between the upper surface and the lower surface
Implementation Method 2
The worm gear is configured to engage the ledge when the fastener is in the locked position
Implementation Method 3
The body is tapered between the upper surface and the lower surface
Data Source
AI summary
A fastener includes a bolt, a worm gear, and a retainer. A bolt shaft has a connecting region proximate to a free end of the shaft. The worm gear has a body with an upper surface, a lower surface, and an aperture that receives the bolt. The worm gear also includes a helical portion on an outer surface of the body. The retainer connects to the connecting region to retain the bolt within the aperture. The fastener can rotate relative to a cover to move from an unlocked position to a locked position where the helical portion engages the flange and limits translational movement of the cover relative to the flange. The body is tapered between the upper and lower surfaces.