Power Tool Collet Concentricity via Conical Socket
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Solution Overview
Problem
Prior art power tools fail to guarantee accurate concentricity of working implements relative to the output shaft, leading to less accurate working results due to weak thread connections between the collet and the output shaft.
Innovation Solution
A connection device featuring a conical socket portion integral with the output shaft and a radially elastic collet, supported directly by this socket, ensures accurate concentricity by using a snap coupling and axial thrust to lock the working implement, eliminating the need for a thread connection for radial support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thread connection is used to support the collet relative to the output shaft, then the device complexity is reduced and ease of manufacture is improved, but the manufacturing precision and concentricity of the working implement deteriorate
Solution Approach 1:
The invention extracts the thread connection from the radial support function. The thread connection is removed as a support element, and the collet is instead supported directly by a conical surface of the output shaft, eliminating the intermediate threaded portion that compromised precision.
Solution Approach 2:
The connection device is segmented into distinct functional elements: the collet for radial retention, the conical socket for precise positioning and support, and the thread connection solely for axial locking. This segmentation allows each element to perform its specific function optimally without compromising overall precision.
2Adaptability or versatility
If a separate collet with thread connection is used to retain the working implement, then the adaptability and ease of operation are improved, but the reliability of concentricity guarantee deteriorates
Solution Approach 1:
The invention merges the radial support function and the concentricity guarantee into the conical socket portion of the output shaft. The conical surface provides both the positioning geometry and the support structure, eliminating the weak link of the thread connection from the radial support path.
Solution Approach 2:
Instead of using the thread connection to provide radial support (as in prior art), the invention inverts the approach by using the conical surface to provide radial support and positioning, while the thread connection is relegated solely to axial locking, thereby inverting the functional assignment to achieve better precision.
3Device complexity
If the collet is supported via a thread connection, then the device complexity is reduced, but the manufacturing precision and working accuracy deteriorate
Solution Approach 1:
The conical socket portion acts as an intermediary element between the collet and the output shaft. It provides a precise conical surface that mediates the connection, ensuring accurate positioning and radial support without relying on the less precise thread connection for these functions.
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 guarantees high-quality work performance by ensuring precise radial support and concentricity of the working implement, enhancing the accuracy and reliability of operations like drilling, milling, or reaming.
Implementation Method 1
The collet 28 is of a conventional design having a conical outer surface 21 adapted to fit the conical the socket portion 25 in the output shaft 17
Implementation Method 2
The collet 28 is also provided with a number of overlapping longitudinal slots 23 by which is provided a radial elasticity of collet
Implementation Method 3
This axial thrust force urges the collet 28 further into the conical socket portion 25 resulting in a radial compression of the collet 28 and a locking of an attached working implement
Data Source
AI summary
A portable power tool comprising a housing (10) provided with a handle (11) for manual support of the tool, and a rotation motor drivingly connected to an output shaft (17). A connection device (19) is intended for connecting a working implement to the output shaft (17) and comprises a conical socket portion (25) formed integral and coaxially with the output shaft (17) and a working implement locking collet (28), wherein a collet retaining sleeve (29) is carried on the output shaft (17) via a thread connection 30 and has an inner radial flange (24) defining a front opening (27) for introduction of a working implement. The thread connection (30) is intended to enable an axial displacement of the retaining sleeve (29) and to make the latter produce an axial thrust force on the collet (28) via the flange (24). The front opening (27) of the flange (24) has a diameter (d1) that is bigger than the inner diameter (d2) of the collet (28).