Razor Handle Snap Fit Joint Design for Grip Security
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Solution Overview
Problem
Existing safety razor handles with elastomeric gripping pads face issues with joint security due to inferior creep moduli of commodity thermoplastics, leading to potential disengagement over time and unpredictable impact forces from accidental drops.
Innovation Solution
A safety razor handle design featuring a snap fit joint between a frame and gripping pads, with a bifurcated extension on one pad and a non-deforming extension on the other to prevent disengagement, using thermoplastic elastomeric and non-elastomeric materials for enhanced grip and attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a press fit joint is used between the frame and gripping pad, then assembly is simple and manufacturing is easier, but the joint security deteriorates over time due to creep modulus of thermoplastic materials
Solution Approach 1:
The patent changes the joining mechanism from a press fit joint to a snap fit joint, fundamentally altering how the gripping pad is attached to the frame. This parameter change in the joint type resolves the contradiction by providing both ease of manufacture and high joint security through elastic deformation and engagement features that prevent disengagement over time.
Solution Approach 2:
The gripping pad is constructed as a composite structure with a support layer and a gripping layer, where the support layer provides structural integrity and the gripping layer provides elastomeric grip properties. This composite approach allows each layer to be optimized for its specific function while working together to solve the joint security issue.
2Reliability
If a snap fit joint is used between the frame and gripping pad, then joint security is improved, but manufacturing complexity increases due to deformation requirements
Solution Approach 1:
The patent modifies the snap fit joint design by providing a controlled interference fit between the extension and the slot, rather than requiring large deformations. This parameter change in the interference level allows the joint to be secure while reducing manufacturing complexity and allowing for easier assembly.
Solution Approach 2:
The extension is pre-formed with a specific geometry that includes a protrusion designed to engage with the slot in a predetermined manner. This preliminary preparation of the extension geometry simplifies the assembly process while ensuring secure engagement, thereby reducing manufacturing complexity.
3Object-affected harmful factors
If commodity thermoplastics are used for the support layer, then chemical resistance is improved, but creep modulus deteriorates leading to inferior joint retention
Solution Approach 1:
The gripping pad uses a composite structure where the support layer is made from a thermoplastic material with good chemical resistance, while the gripping layer is made from an elastomeric material with superior creep resistance. This composite approach allows the system to benefit from the chemical resistance of the support layer while the elastomeric gripping layer compensates for the inferior creep modulus through its inherent elastic properties.
Solution Approach 2:
Different parts of the gripping pad have different material properties optimized for their specific functions. The support layer uses a thermoplastic with good chemical resistance for structural support, while the gripping layer uses an elastomer with good creep resistance for maintaining grip pressure. This local differentiation of material properties resolves the contradiction between chemical resistance and creep modulus.
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 snap fit joint provides improved retention and resistance to disengagement, enhancing the security and durability of the handle grip, even under unpredictable impact forces, while maintaining manufacturing advantages.
Implementation Method 1
The elastomeric material provides the user with at least a sense of a more secure grip of the handle in these circumstances
Implementation Method 2
one component part is provided with an extension with a laterally extending protrusion, usually at or near the distal end portion of the extension. During assembly of the two parts the extension undergoes preferably elastic deformation as the lateral protrusion passes around a suitable shelf of the second part before snapping into a mating recess or void of the second part
Data Source
AI summary
A handle for a safety razor is provided that includes an elongated hand gripping structure with a cartridge support structure at an end of the hand gripping structure. The hand gripping structure includes a frame and a first and second gripping pad. Each gripping pad can have a thermoplastic elastomeric gripping layer and a nonelastomeric thermoplastic support layer. The first gripping pad has an extension that cooperates with an opening of the frame to provide a snap fit joint between the frame and the first gripping pad. The second gripping pad has an extension that cooperates with the extension of the first gripping pad to prevent disengagement of the snap fit from the opening of the frame. The extension of the first gripping pad can be bifurcated and the extension of the second gripping pad can be received in the bifurcation.