Expandable Collet Ball Locking for Stable Drill Plate Attachment
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Solution Overview
Problem
Existing secure attachment methods for drilling devices to drill plates in aeronautics are prone to sliding during operations, especially when drilling hard materials or with worn cutting tools, leading to quality issues due to insufficient friction and increased forces required for attachment.
Innovation Solution
An expandable collet with locking balls is used, which expands to securely attach the drilling device to the drill plate, ensuring stable friction and preventing sliding through a conical bore mechanism driven by a cylinder assembly, allowing efficient locking and unlocking with controlled pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional expandable collet is used to attach the drilling device to the drill plate, then the attachment can be secured through friction, but the drilling device may slide during drilling operations when hard materials are drilled or cutting tools are worn out
Solution Approach 1:
The attachment system is segmented into multiple independent locking balls (typically 3-4 balls distributed around the circumference) that work together to prevent sliding. Each ball engages with corresponding features on the drill plate, distributing the locking function across multiple points rather than relying on a single friction-based contact point.
Solution Approach 2:
The locking balls act as intermediary elements between the expandable collet and the drill plate. These balls transfer and amplify the expansion force into radial locking forces that prevent sliding, serving as a mechanical mediator that converts axial expansion into lateral locking action.
2Reliability
If the size of the cylinder assembly is increased or greater pressure is applied to prevent sliding, then attachment stability improves, but available space is reduced and mechanical fatigue of components increases
Solution Approach 1:
The system replaces a purely friction-based mechanical attachment with a mechanical interlocking system using locking balls. This substitution transforms the attachment mechanism from relying on continuous friction contact to discrete mechanical engagement points, achieving more reliable sliding prevention with the same or smaller cylinder assembly.
Solution Approach 2:
The system changes the fundamental parameter of attachment from friction coefficient dependence to geometric interlocking. By transforming the attachment mechanism from friction-based to ball-locking-based, the system achieves stability independent of friction parameters, allowing smaller cylinder assemblies to achieve the same or better reliability.
3Reliability
If a quarter-turn bayonet system with shoulder screws is used to prevent sliding, then attachment stability improves, but the system becomes bulky and incompatible with small distances between drill plate holes
Solution Approach 1:
The expandable collet with locking balls serves multiple functions simultaneously: it provides secure attachment through ball locking, allows quick insertion and removal through simple expansion/contraction, and maintains a compact size. This multi-functional design replaces the specialized bayonet system while achieving similar or better performance across multiple criteria.
Solution Approach 2:
The attachment system uses dynamic expansion and contraction of the collet to control the state of the locking balls. During insertion, the collet is contracted to allow easy entry; during operation, expansion engages the locking balls for stable attachment. This dynamic transition enables reliable attachment without the bulk of static interlocking features.
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 provides a compact, reliable, and high-quality attachment method that maintains drilling precision and reduces the forces needed for secure attachment, ensuring repeatable drill-hole depths and preventing tool breakage during detachment.
Implementation Method 1
an expansion cone housed inside the conical bore of the expandable ring, the external peripheral outline of which is complementary to the conical bore; means for the driving in translation of the expansion cone within the conical bore along the longitudinal axis between at least: a releasing position in which the cone is shifted to the largest-diameter side in the conical bore of the expandable ring so much so that this ring is in a relaxed state; a locking position in which the cone is shifted to the smallest-diameter side of the conical bore of the expandable ring so much so that this ring is situated in an expanded state
Implementation Method 2
The axial force applied to the expansion cone generates contact pressure between the expandable collet and the positioning bore in which it is housed in a locking position. This contact pressure and the associated friction must be sufficient to counter the reaction torque and the thrust forces along the drilling axis transmitted to the drill during a drilling operation
Data Source
AI summary
A device for securely attaching a drilling device to a drill plate provided with a plurality of positioning bores. The attachment to the drill plate including an expandable collet with balls.