Torque Coupling Spring Retainer for Stable Screwdriver Adjustment

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Solution Overview

Problem

Existing hand-held power tools lack a reliable and efficient mechanism for adjusting torque levels, particularly in screwdrivers, which affects the safety and precision of operations.

Innovation Solution

A torque coupling system with a spring retaining ring and transmission element, featuring bearing points of varying lengths and a toothed connection, allows for adjustable torque levels through a user-operated control element, ensuring secure and robust arrangement of spring elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spring elements are arranged between the transmission element and the spring retaining ring without bearing points, then the structure is simpler, but the arrangement of spring elements is unreliable and unstable

Engineering Contradiction:
Improvereliable arrangement of spring elementsVSAvoidstructure with bearing points
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The spring retaining ring with bearing points acts as an intermediary component between the spring elements and the transmission element. The bearing points provide dedicated engagement locations that securely hold the spring elements, preventing them from shifting or becoming dislodged during operation, thus ensuring reliable arrangement without requiring complex additional structures.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If bearing points with different lengths are provided on the spring retaining ring, then different spring forces can be used for adjustable torque levels, but the device complexity increases

Engineering Contradiction:
Improveadjustable torque levels with different spring forcesVSAvoidspring retaining ring with multiple bearing point lengths
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The spring retaining ring features bearing points with different lengths at specific locations, allowing different spring forces to be applied at different positions. This local variation in bearing point geometry enables adjustable torque levels by selecting appropriate spring forces for specific application requirements, while the rest of the retaining ring maintains a simple circular structure.

Inventive Principle:
Principle #3Local quality

3Ease of operation

If the spring retaining ring is connected to the operating element via toothing for torque adjustment, then torque level adjustment is enabled, but the device complexity increases

Engineering Contradiction:
Improvetorque level adjustment by userVSAvoidtoothing connection between spring retaining ring and operating element
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The toothing connection between the spring retaining ring and the operating element provides a mechanical interface for torque adjustment. By engaging the toothing, the user can rotate the operating element to adjust the precompression of the spring elements, thereby changing the torque level. This mechanical substitution allows direct user control without requiring complex electronic or hydraulic systems.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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

Enables safe, reliable, and easy adjustment of torque levels, enhancing the stability and precision of hand-held power tools by providing a compact and weight-optimized design.

Implementation Method 1

a transmission element (250) acted upon by at least two spring elements (260), wherein the at least two spring elements (260) are arranged between the transmission element (250) and a spring retaining ring (270)

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4344826B1Hand-held power tool with a torque coupling
Publication Date: 2026.05.20 ROBERT BOSCH GMBH
  • EP4344826B1 patent drawingFigure 1
  • EP4344826B1 patent drawingFigure 2
  • EP4344826B1 patent drawingFigure 3

AI summary

In a hand-held power tool, in particular a screwdriver, with a housing in which at least one gearbox (145) and a drive motor for the rotary drive of a tool holder (120) are arranged, and with a torque coupling (135) which has a torque setting unit (139) associated with the gearbox (145), to which a transmission element (250) acted upon by at least two spring elements (260) is associated, wherein a torque level of the torque coupling (135) is adjustable via a user-operated control element (130), wherein the at least two spring elements (260) are arranged between the transmission element (250) and a spring retaining ring (270), and wherein the spring retaining ring (270) is arranged on a side of the transmission element (250) facing away from the gearbox (145) and is connected to the control element (130) for setting a torque level via a toothed connection (271),The spring retaining ring (270) has bearing points (331, 333) assigned to at least two spring elements (260).