Output Shaft Seal Placement Between Bearings to Reduce Abrasion

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Solution Overview

Problem

Existing electric tools, such as impact rotary tools, face challenges with seal member durability due to abrasion from the output shaft, leading to potential failures and malfunctions.

Innovation Solution

The electric tool incorporates a seal member positioned between bearings, with an inner circumferential surface in contact with the output shaft, supported by bearings to reduce rotational shake and abrasion, using materials like felt or rubber with oil absorptiveness to capture foreign substances and retain lubricants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the seal member is positioned close to the output shaft to prevent foreign substance entry, then sealing effectiveness is improved, but the seal member is more susceptible to abrasion from the output shaft

Engineering Contradiction:

Improvesealing effectivenessVSAvoidseal member durability

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent introduces an intermediary structure (the bearing assembly with inner and outer rings) between the output shaft and the seal member. This intermediary bearing structure reduces direct contact and abrasion between the output shaft and seal member while maintaining the sealing function, thus resolving the contradiction between sealing effectiveness and seal member durability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The seal member is designed as a flexible sealing element that can deform to maintain contact with the output shaft for effective sealing, while the bearing structure provides a protective intermediary layer that reduces wear on the seal member during operation.

Inventive Principle:

Principle #30Flexible shells and thin films

2Duration of action of stationary object

If the seal member is positioned far from the output shaft to reduce abrasion, then seal member durability is improved, but foreign substances can more easily enter the tool

Engineering Contradiction:

Improveseal member durabilityVSAvoidforeign substance contamination

Core Design Contradiction:

Duration of action of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The bearing assembly serves as an intermediary structure that maintains a controlled gap between the output shaft and seal member. This intermediary structure allows the seal member to be positioned at an optimal distance from the output shaft to minimize abrasion while still maintaining effective sealing against foreign substances through the bearing's structural barrier.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Duration of action of stationary object

If the seal member is made of hard material to resist abrasion, then seal member durability is improved, but its ability to capture foreign substances and retain lubricants is reduced

Engineering Contradiction:

Improveseal member durabilityVSAvoidforeign substance capture and lubricant retention

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The seal member is designed as a flexible sealing element that can deform to capture foreign substances and retain lubricants. The flexibility of the seal member allows it to conform to the output shaft surface and create effective sealing, while the bearing structure provides the abrasion protection.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The system uses a composite approach where the seal member is made of a soft, flexible material optimized for sealing and capturing foreign substances, while the bearing structure provides a hard, abrasion-resistant intermediary layer. This composite design allows each component to be optimized for its specific function without compromise.

Inventive Principle:

Principle #40Composite materials

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 configuration enhances seal member durability, preventing foreign substances from entering the tool and lubricants from leaking, thereby reducing failure risks and maintaining tool functionality.

Implementation Method 1

using materials like felt or rubber with oil absorptiveness to capture foreign substances and retain lubricants

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

supported by bearings to reduce rotational shake and abrasion

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12544902B2Electric tool

Publication Date: 2026.02.10 NEXRA FIELD WORKS CO LTD

AI summary

An electric tool includes an output shaft, a drive shaft, a transmission mechanism, a plurality of bearings, and a seal member. The plurality of bearings are aligned in an axial direction of the output shaft and rotatably support the output shaft. The seal member has a through hole into which the output shaft is inserted. The seal member is disposed, in at least one space of spaces each sandwiched between each two adjacent bearings of the plurality of bearings, such that an inner circumferential surface of the through hole is in contact with the outer circumferential surface of the output shaft.