Power Tool Housing Insert for Clamping Force and Leak Control
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Solution Overview
Problem
Pneumatic and hydraulic power tools face issues with creep and stress relaxation in plastic housings, leading to reduced clamping force over time and potential fluid leaks, which are exacerbated by the added weight and size of stress-reducing ribs.
Innovation Solution
An insert made of a material resistant to creep and stress relaxation, such as metal, is coupled to the housing to receive fasteners, distributing the clamping force and maintaining it over the tool's life, while being bonded to the housing to prevent backing out, thus eliminating the need for weight-increasing ribs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ribs are added to the housing to reduce stress and prevent creep, then the reliability is improved, but the weight and size of the tool increase
Solution Approach 1:
The housing is segmented into two material zones: a plastic housing body and a metal insert positioned at the fastener location. This segmentation allows the plastic housing to maintain overall structural integrity while the metal insert specifically addresses stress concentration and creep at the critical fastener interface, eliminating the need for additional ribs that would increase weight.
Solution Approach 2:
Instead of uniformly reinforcing the entire housing with ribs, the invention applies local quality by placing a metal insert only at the specific location where fastener stress concentration occurs. This localized reinforcement provides the necessary creep resistance and stress distribution exactly where needed, without adding weight to the entire tool structure.
2Ease of manufacture
If plastic housing is used, then the ease of manufacture is improved, but the ability to maintain clamping force over time deteriorates due to creep and stress relaxation
Solution Approach 1:
The invention employs composite materials by combining plastic housing with a metal insert. The plastic housing provides ease of manufacture and corrosion resistance, while the metal insert provides superior mechanical properties for maintaining clamping force. This composite approach allows the tool to benefit from both material types without requiring the entire housing to be made of metal, which would compromise ease of manufacture.
Solution Approach 2:
The metal insert acts as an intermediary element between the plastic housing and the fastener. It mediates the stress and clamping force interaction, protecting the plastic housing from direct exposure to high fastener loads that would cause creep and stress relaxation. The insert transfers and distributes these forces in a manner that preserves the plastic housing's manufacturing advantages while ensuring reliable clamping force maintenance.
3Reliability
If metal insert is used instead of plastic, then the clamping force maintenance is improved, but the manufacturing complexity increases
Solution Approach 1:
The housing structure is segmented into a plastic body and a metal insert component. This segmentation allows each component to be manufactured separately using optimal processes for each material, then assembled together. The simplicity of the insert design (a basic geometric shape receiving the fastener) minimizes the added manufacturing complexity while maximizing the reliability benefit.
Data Source
AI summary
Inserts disposed in a housing of a pneumatically or hydraulically powered tool having a motor adapted to rotate a drive lug in either of first and second rotational directions. The insert is composed of a material resistive to creep and/or stress relaxation. The insert contacts fasteners applying a clamping force to the tool and remove the housing from the load path of the clamping force, thereby reducing the possibility of fluid leaks.