Power Tool Chuck Key Drive Layout for Shorter Torque Coupling
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Solution Overview
Problem
Existing chuck designs for power tools face issues with torque transmission reliability and axial length due to threaded connections and diametrically oriented slots, which limit their effectiveness in transmitting torque and require longer chuck bodies.
Innovation Solution
A chuck design featuring a body with angled passageways and jaws that are non-rotationally coupled to the output shaft using a key drive member system, including radial and axial slots, which enhances torque transmission and reduces the axial length by allowing the jaws to retract beyond the tail portion of the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded connection is used to couple the chuck to the output shaft, then the chuck can be mounted onto the shaft, but the connection can loosen during operation and has limited torque transmission ability
Solution Approach 1:
The coupling interface is segmented into multiple independent key drive members (first key drive member in the chuck body and second key drive member on the output shaft) that engage with each other. This segmentation allows for positive mechanical engagement that prevents loosening while transmitting torque effectively, replacing the single threaded connection with multiple discrete engagement points.
Solution Approach 2:
The key drive members act as intermediary elements between the chuck body and output shaft. Instead of direct threaded engagement, the key drive members mediate the connection, providing a positive mechanical lock that transmits rotational force reliably without the loosening issues inherent in threaded connections.
2Reliability
If a diametrically oriented rear slot is used to couple the chuck body to the output shaft, then the chuck can be mounted, but the chuck body requires increased axial length to accommodate the slot and jaw passages
Solution Approach 1:
The key drive members are positioned in a second plane that is axially forward of the first plane (where the jaw rear ends lie). This dimensional arrangement allows the coupling function to be achieved without extending the axial length of the chuck body, as the key drive engagement occurs in a different axial plane than the jaw retraction space.
Solution Approach 2:
The key drive members are angularly spaced from each other and from the passageways, creating an asymmetric arrangement. This asymmetric positioning allows the key drive engagement to occur without interfering with the jaw passages, eliminating the need for the symmetric diametrically oriented slot design that requires additional axial length.
3Length of moving object
If the jaws are positioned with rear ends in a first plane and the key drive member extends to a second plane axially forward, then the axial length is reduced, but the design complexity increases
Solution Approach 1:
The key drive members serve multiple functions: they couple the chuck body to the output shaft, transmit torque, and their angular spacing from the passageways automatically provides clearance for jaw retraction. This multi-functionality reduces the need for additional structural elements, offsetting the complexity of the multi-plane arrangement with functional consolidation.
Data Source
AI summary
A power tool chuck includes a body with a central bore extending along an axis and configured to receive a tool bit, a plurality of angled passageways, and a plurality of jaws received in the passageways and moveable between an axially forward and radially inward clamping position and an axially rearward and radially outward retracted position. At least one jaw has a rear end lying in a first plane transverse to the axis. A first key drive member coupled to a tail portion of the body is configured to be engaged by a second key drive member on a power tool output shaft to non-rotationally couple the body to the output shaft. The first key drive has a forward end lying in a second plane transverse to the axis. The second plane is axially forward of the first plane when the jaws are in the retracted position.