Pneumatic Power Tool Spindle Retraction Torque Limiting Coupling

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Solution Overview

Problem

Conventional pneumatic power tools face issues with spindle and gear jamming due to high rotational speeds, leading to stress and wear, and require a compromise in retraction positioning that can result in incomplete retraction or jamming, especially when working in confined spaces.

Innovation Solution

The implementation of a retraction torque limiting coupling with a lock mechanism that blocks initial retraction to prevent jamming, allowing safe spindle retraction across varying rotational speeds, and a pneumatic system to manage gear transitions, ensuring efficient and jam-free operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the spindle rotational speed is increased to improve productivity, then the drilling operation becomes more efficient, but the spindle and gears may get jammed due to excessive speed

Engineering Contradiction:

Improvedrilling efficiencyVSAvoidjaming risk

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The pneumatic signal is actuated during the last stages of retraction to preemptively stop the motor before the spindle completes its retraction journey. This preliminary action prevents the spindle from reaching positions where jamming would occur due to excessive rotational speed, thereby protecting the system while maintaining high operational speeds during actual drilling

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system prepares for potential jamming by activating the pneumatic signal in advance during retraction. The sensor triggers the pneumatic signal at a predetermined position before full retraction, allowing the motor to be stopped proactively rather than reactively after jamming occurs

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the pneumatic signal is actuated closer to the fully retracted position to ensure complete retraction, then the spindle can reach its final position, but the rotational speed becomes too high causing jamming

Engineering Contradiction:

Improveretraction completenessVSAvoidjaming risk

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A sensor detects the spindle position and provides feedback to the control system. When the sensor detects that the spindle has reached a predetermined position during retraction, it triggers the pneumatic signal to actuate the main valve, creating a feedback-controlled stopping mechanism that prevents jamming while ensuring complete retraction

Inventive Principle:

Principle #23Feedback

3Ease of operation

If the sensor position is placed closer to the fully retracted position to trigger retraction, then complete retraction is achieved, but the tool head length increases reducing workability in confined spaces

Engineering Contradiction:

Improveretraction completenessVSAvoidtool head length

Core Design Contradiction:

Ease of operationVSLength of moving object

Solution Approach 1:

The sensor is integrated within the existing tool head structure in a nested manner, positioned at the predetermined location without extending the overall tool head length. This allows the sensor to trigger the pneumatic signal at the optimal position for preventing jamming while maintaining a compact tool design suitable for confined spaces

Inventive Principle:

Principle #7Nested doll (Nesting)

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

Enables safe and complete spindle retraction across high rotational speeds without compromising tool functionality, reducing wear and improving operational efficiency and compactness.

Implementation Method 1

The second gear transmission includes a retraction torque limiting coupling adapted to be released when the operational torque exceeds a retraction threshold torque

Methodology Applied

Scientific EffectTorque: Torque

Implementation Method 2

the smoothly toothed engagement is held together by means of a spring, the spring having a spring action that corresponds to the retraction threshold torque

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentEP2773486B1Power tool and method of operating an automated drilling operation

Publication Date: 2015.07.01 ATLAS COPCO IND TECHNIQUE AB INTELLECTUAL PROPERTY DEPARTMENT

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AI summary

A power tool (10) comprising a pneumatic motor (13) with an output shaft (16), a spindle (11) that is drivingly connected to the output shaft (16) via a drive gear (23) in order to provide a rotational movement to the spindle (1 1) and via a feed gear (25) in order to provide a translational movement to the spindle (11). A cylinder (32) that governs the gear transmission to the feed gear (25), which cylinder (32) is arranged to be translated between a retraction gearing position and an advancement gearing position. The retraction gearing includes a retraction torque limiting coupling adapted to be released when the operational torque (T) exceeds a retraction threshold torque (TR) in order to terminate the retraction. A lock mechanism (39) is arranged to selectively block the cylinder (32) in the retraction gearing position through engagement between a tooth (57) of a ratchet (40) on said lock mechanism (39) and a shoulder (55) on said cylinder (32). The lock mechanism assures that the cylinder (32) is kept in the retraction gearing position during the initial phase of the retraction of the spindle (11).