Replaceable Shopping Cart Tire Assembly
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Solution Overview
Problem
Shopping cart wheels with prior art tires face issues of noise, vibration, and premature failure due to flat spots or gouges, leading to early disposal of entire wheel assemblies, which contributes to material waste and increased operational costs.
Innovation Solution
A replaceable tire system for shopping cart wheels using push-in half-rivets and T-tongue/groove end joints that allow easy installation and removal of tires without the need for specialized tools, ensuring secure attachment and minimizing noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the entire wheel assembly is discarded when the tire becomes defective, then the cart can be quickly replaced, but material waste increases and operational costs rise
Solution Approach 1:
The wheel assembly is divided into separable components: the rim assembly (including hub and bearing) and the tire. The tire can be removed and replaced independently from the rim assembly, allowing only the defective tire to be discarded while reusing the intact rim and bearing components. This segmentation resolves the contradiction by enabling selective replacement rather than complete assembly disposal.
Solution Approach 2:
The patent enables recovery and reuse of valuable components (rim and bearing assembly) by discarding only the worn tire. The rim assembly is designed to be retained and reused multiple times with different tires, thereby reducing material waste and operational costs while maintaining cart productivity.
2Ease of operation
If a non-replaceable tire design is used, then the wheel assembly is simpler, but the tire cannot be easily replaced when defective
Solution Approach 1:
The wheel assembly is segmented into a rim with passageways and a separate tire that can be independently installed and removed. The tire includes engagement features (protrusions) that interact with the rim's passageways, allowing simple tool-free attachment and detachment. This segmentation enables easy tire replacement while adding minimal structural complexity.
Solution Approach 2:
The tire and rim are designed with self-aligning engagement features where the tire's protrusions automatically align with and snap into the rim's passageways during installation, and can be easily released by applying force to disengage them. This self-service mechanism eliminates the need for specialized tools or complex fastening systems, achieving ease of operation with minimal added complexity.
3Reliability
If the tire is securely attached to the rim, then the wheel assembly is reliable, but the tire cannot be easily removed for replacement
Solution Approach 1:
The tire-rim connection transitions from a static permanent bond to a dynamic reversible engagement. The tire protrusions engage with the rim passageways to provide secure attachment during operation, but can be easily disengaged by applying sufficient force to overcome the engagement resistance. This dynamic connection maintains reliability during use while enabling easy removal for replacement.
Solution Approach 2:
The engagement design creates a balanced state where the tire is securely held during normal operation but requires only moderate additional force to release. The geometric relationship between protrusions and passageways ensures that the same structural features provide both secure attachment and easy removal, achieving equipotentiality between reliability and ease of repair.
4Object-affected harmful factors
If a soft tire material is used to reduce noise and vibration, then the ride is quieter, but the tire may deform more easily under load
Solution Approach 1:
The tire is constructed from composite materials combining soft elastomeric components for noise reduction with reinforcing elements (such as fabric layers or rigid ribs) to maintain structural integrity under load. This composite structure allows the tire to provide quiet operation while resisting deformation from cart weight and operational forces.
Solution Approach 2:
The tire design incorporates regions of different material properties: softer material in contact patches for noise reduction and vibration damping, while incorporating stiffer reinforcing structures in load-bearing areas. This local quality variation allows the tire to simultaneously reduce harmful noise/vibration and maintain adequate strength under load.
Data Source
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AI summary
The disclosure addresses a series of interactions between wheel rims and a number of different replaceable tire segments to cover the wheel rims. The disclosure teaches more than one way to engage the one or more tire segments to wheel rims and to form seams between ends of the one or more tire segments. The tire segments may be removed and replaced so that the wheel rim and wheel bearing may be used longer than the useful life of the tire segments.