Drill Depth Stop with Spring-Loaded Anti-Rotation

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Solution Overview

Problem

Traditional depth stop devices for drills used in aircraft manufacturing are prone to deflection and misalignment due to overtightening, leading to inaccurate and repeatable countersunk holes, compromising structural integrity and increasing production costs.

Innovation Solution

A depth stop device featuring a tubular member with grooves and fine pitched threads, secured by a lock screw and anti-rotational member with a spring, which prevents deflection and damage by modulating force and providing an audible click for precise depth adjustment, ensuring the inner sensing sleeve is locked in place without mechanical misalignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a tightening screw is used to secure the depth-sensing sleeve, then the sleeve can be held in place relative to the drill, but the sleeve may deflect or misalign due to overtightening, compromising depth precision

Engineering Contradiction:

Improvedepth precisionVSAvoidoperator skill dependency

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The depth stop device is designed to automatically maintain proper sleeve positioning without requiring operator skill for tightening. The sleeve self-adjusts to eliminate backplay through the rack and pinion mechanism, and the spring-loaded anti-rotational member automatically engages with the gear teeth to prevent rotation, eliminating the need for operator judgment in tightening力度.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The traditional screw-tightening mechanism is replaced with a rack and pinion rotational adjustment mechanism combined with a spring-loaded anti-rotational member. This substitution eliminates the overtightening problem by using a positive engagement system where the spring-loaded member automatically engages with gear teeth, providing consistent positioning without operator skill dependency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Weight of moving object

If the sleeve wall is made thin to reduce weight, then the drill tool weight is minimized, but the sleeve becomes more prone to deflection under screw pressure

Engineering Contradiction:

Improvedrill tool weightVSAvoidsleeve resistance to deflection

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The sleeve design incorporates self-adjusting features including the rack and pinion mechanism that automatically eliminates backplay, and the spring-loaded anti-rotational member that self-engages with gear teeth. These features allow the thin-walled sleeve to maintain positioning accuracy and resistance to deflection without requiring additional material or wall thickness.

Inventive Principle:

Principle #25Self-service

3Reliability

If the lock screw is tightened to secure the depth stop, then the device is fixed in place, but the inner sensing sleeve may be deflected or damaged

Engineering Contradiction:

Improvedepth stop stabilityVSAvoidsleeve deflection and damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The screw-tightening mechanism is replaced with a spring-loaded anti-rotational member that engages with gear teeth through a rack and pinion system. This substitution eliminates direct compressive forces on the sensing sleeve, as the spring-loaded member provides stable fixation through positive engagement with the gear teeth, preventing both deflection and damage while maintaining reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The spring-loaded anti-rotational member provides beforehand cushioning by using spring force to maintain engagement with the gear teeth. This spring mechanism absorbs any excess force that might otherwise deflect or damage the sensing sleeve, while still providing stable fixation of the depth stop position.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The device allows for precise and repeatable drilling of countersunk holes without relying on operator skill, preventing damage and misalignment, thus ensuring accurate assembly and reducing manufacturing costs by maintaining the structural integrity of aircraft parts.

Implementation Method 1

A spring is provided which fits between the lock screw and the anti-rotational member

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

The anti-rotational member has teeth which engage in the grooves of the inner sensing sleeve to fix the inner sensing sleeve in place

Methodology Applied

Scientific EffectMechanical engagement: Mechanical Fastener

Implementation Method 3

The inner sensing sleeve has external fine pitched thread which screw into a second tubular part or outer portion of the sensing sleeve

Methodology Applied

Scientific EffectScrew thread: Screw

Data Source

PatentUS8240960B2Device for producing precise countersinking in drilled holes

Publication Date: 2012.08.14 WEST COAST IND INC

AI summary

A depth stop attached to a drill for producing precise countersinking in drilled holes. The depth stop produces an accurate and precise countersink in drilled holes by limiting the depth to which a drill bit can drill through a work piece. An audible click occurs for every 7.5 micron change in depth in the preferred embodiment. The depth stop is configured such that attempts to over tighten the lock screw which fixes the depth amount will not damage or deflect the working parts of the device thereby producing accurate and repeatable results.