Spline Tool Bit Holder Assembly for Axial Alignment and Low Runout
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Solution Overview
Problem
Existing tool bits and bit holders face challenges in secure axial alignment and prevention of runout during engagement with tools, leading to inefficiencies and misalignment.
Innovation Solution
A tool bit design featuring a drive portion with circumferentially spaced splines and a bit holder assembly with a power groove and retainer system that secures the bit through a shuttle and barrel mechanism, ensuring axial alignment and preventing runout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional bit holder design is used, then the structure is simple, but axial alignment is insufficient and runout occurs during engagement
Solution Approach 1:
The bit holder structure is segmented into multiple functional components: a drive portion with internal splines for torque transmission, a separate retainer component with spring-loaded balls for axial positioning, and a shuttle mechanism for tool engagement. This segmentation allows each component to perform its specific function optimally, achieving precise axial alignment while maintaining reasonable structural complexity through modular design.
Solution Approach 2:
The retainer component acts as an intermediary between the drive portion and the tool bit, using spring-loaded balls to maintain precise axial positioning. The shuttle mechanism serves as an intermediary that facilitates smooth engagement and disengagement while maintaining alignment. These intermediary elements prevent direct contact that would cause runout, thereby improving manufacturing precision without excessive complexity.
2Reliability
If a simple engagement mechanism is used, then the device complexity is low, but engagement reliability is insufficient
Solution Approach 1:
The retainer component is pre-loaded with spring pressure to maintain constant axial force on the tool bit before engagement occurs. This preliminary action ensures that as soon as the tool bit enters the drive portion, it is immediately secured with precise axial positioning, preventing any runout or misalignment during the engagement process. The spring-loaded mechanism is already in position and ready to secure the bit the moment engagement begins.
Solution Approach 2:
The engagement mechanism uses dynamic spring-loaded balls that can move radially to accommodate the tool bit during insertion, then automatically lock into position to provide rigid axial support. The shuttle mechanism provides dynamic movement for engagement and disengagement while maintaining static precision during operation. This dynamic behavior allows the system to transition smoothly between states, improving reliability without requiring an overly complex fixed structure.
3Manufacturing precision
If conventional drive portion design is used, then manufacturing is simple, but runout prevention is insufficient
Solution Approach 1:
The drive portion incorporates asymmetric spline teeth with specific profile geometries that are optimized for torque transmission and axial positioning. The retainer component uses asymmetric spring-loaded balls positioned at specific angles to provide radial pre-loading. This asymmetric design prevents runout by ensuring uniform contact forces around the circumference, improving manufacturing precision while the asymmetric features can be efficiently produced through modern CNC machining and molding processes.
Solution Approach 2:
The drive portion design optimizes parameters such as spline tooth profile angles, radial pre-load forces from spring balls, and clearance tolerances to achieve minimal runout. By carefully selecting and adjusting these parameters within manufacturing capabilities, the system achieves high precision axial alignment without requiring excessively tight tolerances that would make manufacturing difficult. The spring-loaded mechanism dynamically adjusts parameters to compensate for manufacturing variations.
Data Source
AI summary
A tool bit including a tip configured to engage a work surface, a shank extending from the tip and defining a longitudinal axis, and a drive portion coupled to an end of the shank opposite from the tip and configured to be engaged by a tool, wherein the drive portion includes a plurality of splines circumferentially spaced around the longitudinal axis, each spline having opposing sidewalls which extend through the drive portion