Webbing Winding Clutch Structure Without a Separate Stopper

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Solution Overview

Problem

Existing webbing winding devices require a stopper member to restrict the rotation of the torsion shaft with respect to the spool, which increases the number of components and complexity.

Innovation Solution

A webbing winding device design that eliminates the need for a stopper member by using a clutch mechanism with a locking piece portion on the clutch cover, which is locked to the trigger member to restrict rotation of the torsion shaft with respect to the spool.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stopper member is added to restrict rotation of the torsion shaft with respect to the spool, then the rotational restriction function is improved, but the number of components and device complexity increases

Engineering Contradiction:

Improverotational restriction functionVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The clutch cover is designed with an integrated locking piece portion that directly engages with the trigger member, merging the function of a separate stopper member into the clutch cover structure itself. This integration eliminates the need for additional components while maintaining the rotational restriction function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The clutch cover serves multiple functions: it covers the clutch mechanism, provides a locking piece for restricting torsion shaft rotation, and structurally supports the clutch assembly. By making the clutch cover multi-functional, the patent eliminates the dedicated stopper member while preserving all necessary functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If the clutch mechanism is designed with integrated locking functionality, then the number of components is reduced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvenumber of componentsVSAvoidlocking piece engagement precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The locking piece portion is designed with an asymmetric profile featuring a specific engagement shape that mates with the trigger member. This asymmetric design provides inherent alignment features that guide the engagement process, reducing the tolerance requirements compared to symmetric or less-defined engagement geometries.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The locking piece portion is pre-formed as an integral part of the clutch cover during the molding process, rather than being assembled separately. This preliminary formation ensures precise geometric relationships are built-in during manufacturing, reducing the need for high-precision post-assembly adjustments.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250136041A1Webbing winding device

Publication Date: 2025.05.01 KK TOKAI RIKA DENKI SEISAKUSHO

AI summary

A webbing winding device includes: a spool around which webbing to be worn by an occupant is wound and which is rotated in a pull-out direction by the webbing being pulled out; a trigger member provided at the spool; a torsion shaft engaged with the spool and twisted to allow rotation of the spool in the pull-out direction; and a clutch with which the torsion shaft is engaged and the trigger member is engaged, and in which part of a member engaged with the torsion shaft so as to be relatively non-rotatable is locked to the trigger member to restrict rotation of the torsion shaft with respect to the spool, the clutch being operated by being released by actuation of the trigger member and engaged with a lock member to restrict rotation with respect to the lock member.