Rotating Shaft Locking Mechanism for Power Tools
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power hand tool shaft locking mechanisms either weaken the shaft by grinding flats or provide inadequate engagement points, leading to inconvenient operation and potential wear on gears.
Innovation Solution
An elongated locking member with a spindle lock configuration that engages a hex-shaped bushing on the armature shaft, biased to remain unlocked until manually activated, providing secure locking without damaging the shaft or gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If flats are ground on the shaft to enable wrench engagement, then the shaft can be held stationary for nut removal, but the shaft strength is weakened requiring larger diameter stock
Solution Approach 1:
The locking function is segmented from the shaft itself and transferred to a separate hexagonal bushing component. The bushing is press-fit onto the shaft, providing the locking interface while the shaft remains intact and strong. This allows the shaft to maintain its full structural integrity while still enabling wrench engagement through the external hexagonal shape of the bushing.
2Ease of operation
If one or two holes are created in the gear hub for pin insertion, then the shaft can be locked during blade changes, but there are only one or two engagement points resulting in inconvenience for quick locking
Solution Approach 1:
The locking mechanism transitions from discrete point engagement (1-2 holes) to continuous circumferential engagement (6 hexagonal faces). The hexagonal bushing provides six engagement points around its perimeter, allowing the wrench to engage at any rotational position, effectively creating a continuous locking capability that speeds up the blade change operation.
3Ease of operation
If a complementary gear locking element is used to engage the output gear, then the shaft can be locked, but unnecessary wear is created on the gear reducing its useful life
Solution Approach 1:
The locking function is extracted from the gear system entirely. Instead of using a gear-to-gear locking mechanism that causes wear, the invention uses a hexagonal bushing press-fit onto the shaft that engages with a wrench. This separates the locking function from the drive gear, eliminating wear on the output gear and preserving its life while still providing effective shaft locking.
4Ease of operation
If a locking element is designed to engage the output gear, then shaft locking is achieved, but damage risk to the output gears increases during operation
Solution Approach 1:
The locking mechanism is extracted from the gear engagement system and relocated to a separate hexagonal bushing component. This bushing engages with an external wrench rather than with the output gear teeth, completely eliminating the risk of gear damage during operation. The shaft can be locked or unlocked without any contact between locking elements and the output gear.
Data Source
AI summary
A locking mechanism for a rotary power tool that includes an elongated locking member that is retained by, and is at opposite first and second end portions within, at least one of a motor housing and a gearbox end casting and being slideable between unlocked and locked positions, the locking member first end portion being accessible by a user to move the locking member to the locked position. The locking member also includes a locking portion intermediate the first and second end portions that is configured to engage the non-circular configured portion of a rotatable armature shaft and prevent rotation thereof when the locking member is in its locked position. A biasing element is also included and configured to bias the locking member toward said unlocked position.