Trigger Guide Features Prevent Cocking in Power Tools

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Solution Overview

Problem

Handheld power tools often face issues with trigger cocking and binding during operation, which can lead to reduced precision and control, especially in applications requiring exact control of output.

Innovation Solution

The design incorporates a housing assembly with parallel guide features that limit the trigger member to a linear slide path, preventing cocking and binding by ensuring the trigger member is mounted between two housing members with guide features only on one lateral side, and includes a noncontact switch system using a Hall Effect sensor and magnet for actuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional trigger mounting is used without guide features, then the trigger member can move freely, but the trigger cocks and binds during operation reducing precision and control

Engineering Contradiction:

Improvetrigger operation reliabilityVSAvoidtrigger slide path precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The guide features are segmented into multiple parallel features (upper and lower guide features) that are spaced apart along the heightwise axis. This segmentation provides distributed constraint points that collectively prevent cocking and binding while maintaining manufacturing feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The guide features act as intermediary elements between the trigger member and housing assembly. These intermediary guide features transmit and constrain the trigger's motion, ensuring linear movement while isolating the trigger from direct contact that could cause cocking.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If guide features are added to both lateral sides of the trigger member, then cocking is inhibited, but the device complexity and assembly difficulty increase

Engineering Contradiction:

Improvetrigger stabilityVSAvoidguide feature complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The guide features are positioned asymmetrically, with parallel upper and lower guide features located only on the first lateral side of the trigger member. This asymmetric arrangement provides sufficient constraint to prevent cocking while avoiding the complexity of symmetric guide features on both sides.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The guide features are extracted and concentrated on only one lateral side of the trigger member rather than distributing them on both sides. This extraction reduces the overall complexity of the trigger assembly while maintaining the necessary constraints for reliable operation.

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If complex trigger mounting structures are used to prevent cocking, then trigger control is improved, but the assembly time and manufacturing cost increase

Engineering Contradiction:

Improvetrigger alignment precisionVSAvoidassembly time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The guide features are merged directly into the housing members as integral features rather than being separate components. This merging eliminates the need for additional assembly steps to install separate guide rails or brackets, reducing assembly time while maintaining precise trigger alignment.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The housing members serve multiple functions: they provide structural support, contain internal components, and incorporate the guide features for trigger alignment. This multi-functionality reduces the total number of parts and simplifies the assembly process while ensuring precise trigger control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances the precision and control of handheld power tools by preventing trigger cocking and binding, simplifying assembly, and providing a reliable noncontact switch system for actuating the drive motor.

Implementation Method 1

a noncontact switch system including a Hall Effect sensor mounted on or in the housing assembly, and a magnet mounted on the trigger member for movement therewith relative to the Hall Effect sensor

Methodology Applied

Scientific EffectHall Effect: Hall Effect

Data Source

PatentEP2691215B1Handheld power tools with triggers and methods for assembling same

Publication Date: 2016.11.23 INGERSOLL RAND CO

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AI summary

The housing assembly has a grip portion having a heightwise axis. The housing assembly includes a housing member having parallel upper and lower housing guide features spaced apart along the heightwise axis. The trigger member is mounted in the housing assembly to slide along a slide axis transverse to the heightwise axis. The trigger member includes parallel upper and lower trigger guide features spaced apart along the heightwise axis and mated with the upper and lower housing guide features. The upper and lower housing guide features and the upper and lower trigger guide features cooperate to limit the trigger member to a linear slide path relative to the housing assembly and inhibit cocking of the trigger member about a lateral axis transverse to each of the heightwise axis and the slide axis.