Baluster Shoe Interference Fit Design

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Solution Overview

Problem

Existing decorative shoes for balusters face issues with mechanical fastening systems that can damage the finish, misalignment due to draft angles, and inability to adapt to varying stairway slopes, leading to aesthetic and functional deficiencies.

Innovation Solution

The solution involves assembling decorative shoes from two sections with compressive elastic means, such as sheets, rods, or O-rings, to create an interference fit with the baluster shaft, eliminating the need for mechanical fasteners and allowing for adjustable alignment without damaging the finish or requiring complex custom components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a set screw mechanical fastening system is used to secure the decorative shoe, then the shoe can be held in place, but the finish of the shoe can be chipped or damaged and the set screw may not tighten properly

Engineering Contradiction:

Improvesecuring the shoe in placeVSAvoiddamage to shoe finish

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes the set screw mechanical fastening system from the decorative shoe design. Instead of using a set screw to secure the shoe to the baluster, the invention extracts this harmful mechanical element and replaces it with an interference fit system where the shoe is secured solely by friction between the shoe's internal surface and the baluster shaft, eliminating the risk of finish damage from set screw contact

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical set screw fastening system with a friction-based interference fit system. The shoe includes an opening with a diameter slightly less than the baluster shaft diameter, creating a friction fit that secures the shoe without requiring mechanical fasteners that could damage the finish

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If the shoe is made with a draft angle for molding, then the shoe can be easily manufactured, but the shoe becomes misaligned relative to the baluster shaft

Engineering Contradiction:

Improvemolding the shoeVSAvoidalignment of shoe to baluster shaft

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the dimensional parameters of the shoe opening to create an interference fit. The opening diameter is specified as 0.002 to 0.005 inches less than the baluster shaft diameter, creating sufficient friction to secure the shoe while allowing for minor alignment adjustments. This parameter change eliminates the need for draft angles while maintaining manufacturability

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a fixed angle shoe design is used, then the shoe can be manufactured with a standard angle, but the shoe cannot adapt to varying stairway slopes

Engineering Contradiction:

Improvemanufacturing standard angle shoesVSAvoidadaptation to different stairway angles

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent introduces adjustability to the shoe design by incorporating a slot or groove in the baluster shaft that receives a protrusion on the shoe, allowing the shoe to be positioned at different angles. This dynamic adjustment capability enables the same shoe design to adapt to various stairway slopes while maintaining secure attachment through the interference fit system

Inventive Principle:

Principle #15Dynamics

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

This design ensures secure, aesthetically pleasing installation of decorative shoes across a range of stairway angles without mechanical fasteners, preventing damage and ensuring proper alignment, thus overcoming the limitations of existing solutions.

Implementation Method 1

compressive elastic means, such as sheets, rods, or O-rings, to create an interference fit with the baluster shaft

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

create an interference fit with the baluster shaft, eliminating the need for mechanical fasteners

Methodology Applied

Scientific EffectInterference fit: Friction

Data Source

PatentUS11225798B1Decorative shoe for balusters

Publication Date: 2022.01.18 MOELLER DAVID W

AI summary

Improved decorative shoes for balusters that cover and conceal the attachment points of the balusters to the tread, floor, or rail surfaces and secure themselves in place without the need for mechanical fasteners or adhesives. The baluster shafts can be retained within central holes in the shoes by the use of compressive elastic means such as flexible sheets, rods, strips, O-rings or the like to produce an interference fit when the shaft is inserted in the holes. The shoes can be produced in both flat and angled versions.