Catch Mechanism Friction Element for Spindle Lock Stability
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Solution Overview
Problem
Existing hand-held power tools, such as impact drills, face challenges in generating a reliable and safe frictional force for their catch mechanisms, which affects the longevity of the friction elements and the operational stability of the spindle lock device.
Innovation Solution
The implementation of an annular friction element, such as an O-ring made of rubber or felt, is arranged between the first and second crown disks, generating a predefined frictional force only in the second position, and is designed to prevent undesired activation of the spindle lock device, thereby ensuring safe and reliable operation during drilling and screwing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the friction element is arranged between the crown disks in the first position, then friction is generated continuously, but the lifetime of the friction element decreases significantly
Solution Approach 1:
The friction element is designed to be dynamically positioned between the crown disks only in the second position, not continuously. The bearing holder moves axially to enable the friction element to bear against the crown disks selectively during screwing operations, rather than maintaining continuous contact during all operations including drilling.
Solution Approach 2:
The friction element is positioned locally between specific surfaces of the crown disks only when needed. The first crown disk has an outer circumferential groove and the second crown disk has an inner circumferential groove that accommodate the friction element, creating a localized friction interface rather than continuous widespread contact.
2Stability of the object's composition
If the friction element is arranged to generate friction in the first position, then operational stability is maintained, but the friction element wears out quickly
Solution Approach 1:
The system transitions from static continuous friction contact to dynamic selective friction contact. The bearing holder can move axially between a first position (no friction) and a second position (friction engaged), allowing the friction element to be active only during screwing operations when operational stability is needed, rather than continuously.
Solution Approach 2:
The bearing holder is equipped with a spring that automatically positions the friction element between the crown disks when screwing operations are detected (based on axial forces), and retracts it during drilling operations. This self-regulating mechanism ensures friction is applied only when needed for operational stability during screwing.
3Reliability
If the friction element is continuously engaged, then consistent frictional force is provided, but the device complexity increases
Solution Approach 1:
The bearing holder serves multiple functions: it supports the output spindle, accommodates the friction element, and can move axially to engage or disengage the friction element as needed. This multi-functionality reduces the need for separate dedicated components for friction engagement, thereby managing device complexity while ensuring reliable frictional force when needed.
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 significantly increases the lifetime of the friction element and ensures safe and reliable operation by generating a consistent frictional force, preventing unintended spindle lock device activation, and enhancing the tool's operational stability during use.
Implementation Method 1
An annular friction element is provided, which is arranged without friction in the first position and generates a predefined frictional force between the first and second crown disks in the second position
Data Source
AI summary
A hand-held power tool, in particular an impact drill, is disclosed. The hand-held power tool includes a housing in which a drive unit for driving an output spindle is arranged. A catch mechanism is associated with the drive unit. The catch mechanism has a first crown disk which is connected to the output spindle for conjoint rotation, and a second crown disk which is arranged in the housing for conjoint rotation. In a first position, the first and second crown disks contact each other via associated catch geometries. In a second position, the second crown disk is arranged spaced apart from the first crown disk along a rotation axis of the output spindle. An annular friction element is arranged without friction in the first position, and generates a specified frictional force between the first and second crown disk in the second position.