Impact Wrench Return Stop Prevents Backward Rotation

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Solution Overview

Problem

Conventional drive or impact wrenches require excessive energy to twist and distort screw shafts, leading to inefficient screwing of long screws due to partial conversion of rotary impact energy into thermal energy, and often necessitate predrilling to prevent shaft tearing.

Innovation Solution

A drive or impact wrench equipped with a return stop that prevents backward rotation of the output shaft, allowing a greater portion of rotary impact energy to be used for screwing, reducing the need for initial twisting and distorting of the screw shaft with each impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional drive or impact wrenches are used to screw in long screws, then the screw shaft is repeatedly twisted and distorted with each rotary impact, but the screwing-in process becomes extremely slow and energy is wasted as thermal energy

Engineering Contradiction:

Improvescrewing-in speedVSAvoidenergy conversion to thermal energy

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The return stop performs a preliminary action by preventing backward rotation of the output shaft before the next rotary impact occurs. This maintains the shaft in a pre-twisted state, eliminating the need to repeatedly twist and distort the screw shaft with each impact, thereby dramatically improving screwing-in speed and reducing energy waste.

Inventive Principle:

Principle #10Preliminary action

2Power

If higher rotary impact energy is used to screw in long screws, then the screw shaft is twisted until torsion torque exceeds screwing-in torque, but predrilling becomes necessary to prevent shaft tearing

Engineering Contradiction:

Improverotary impact energyVSAvoidshaft tearing

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The return stop applies a preliminary anti-action by counteracting the backward rotation tendency of the output shaft. This prevents excessive torsional stress from accumulating in the screw shaft, eliminating the harmful effect of shaft tearing that would otherwise require predrilling to prevent.

Inventive Principle:

Principle #9Preliminary anti-action

3Stability of the object's composition

If the output shaft is allowed to rotate backward after each rotary impact, then the resilient torsion decreases completely, but the next rotary impact must first twist the shaft again before screwing can continue

Engineering Contradiction:

Improvetorsion in shaftVSAvoidtime to twist shaft before screwing

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The return stop performs a preliminary action by maintaining the shaft's twisted state between impacts. Instead of allowing the torsion to completely decrease through backward rotation, the return stop preserves the elastic deformation, so the shaft is already pre-positioned for the next screwing-in action, eliminating time loss.

Inventive Principle:

Principle #10Preliminary action

4Productivity

If a return stop is introduced to prevent backward rotation of the output shaft, then more rotary impact energy is used for screwing-in action, but the operator must resist a reverse torque

Engineering Contradiction:

Improvescrewing-in efficiencyVSAvoidoperator resistance torque

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The return stop converts the harmful reverse torque that the operator must resist into a beneficial effect: by preventing backward rotation, it ensures that all rotary impact energy is directed into screwing-in the screw rather than being wasted on twisting and distorting the shaft. The operator's resistance to reverse torque becomes part of the system that maintains shaft tension for efficient screwing.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution enables faster screwing of screws by utilizing more of the rotary impact energy for screwing-in action, reducing the operator's resistance torque and preventing shaft distortion, thus allowing for quicker and more efficient screwing of both short and long screws.

Implementation Method 1

a return stop 16 which cooperates with the output shaft 12 is provided in order to at least partially prevent a backward rotation of the output shaft 12

Methodology Applied

Scientific EffectMechanical constraint:

Implementation Method 2

the screw shaft is turned or twisted or distorted with each rotary impact as a result of the energy which is introduced by means of the drive construction in the screw head relative to the thread until the torsion torque of the shaft is higher than the screwing-in torque of the thread

Methodology Applied

Scientific EffectTorsion:

Implementation Method 3

This energy which turns, twists or distorts the shaft with each rotary impact is in the shaft of the screw at least partially converted into thermal energy

Methodology Applied

Scientific EffectViscous heating: Viscous Heating

Data Source

PatentUS20240342872A1Impact or Impulse Wrench and Method for Screwing in a Screw

Publication Date: 2024.10.17 WURTH INT AG

AI summary

The invention relates to an impact or impulse wrench having a drive motor and an output shaft, an impact or impulse unit being located between the drive motor and the output shaft, and the wrench having a back stop mechanism that cooperates with the output shaft in order to prevent, at least to some extent, reverse rotation of the output shaft.