Handheld Power Tool Locking Switch for Continuous Operation

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Solution Overview

Problem

Existing hand-held power tools require constant user input to maintain operation, leading to user fatigue and inefficiency.

Innovation Solution

A locking switch mechanism with a pivoting handle and sliding block system that allows continuous operation without holding down a power button, utilizing a monostable operating button and a locking switch to maintain motor activation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a power button is used to activate the electric motor, then the motor can be activated and deactivated, but the user must constantly hold down the button during operation, leading to user fatigue and inefficiency

Engineering Contradiction:
Improveuser convenienceVSAvoidcontinuous user input required
Core Design Contradiction:
Ease of operationVSLoss of time

Solution Approach 1:

The locking switch is activated in advance by a single pressing action of the actuating element, which preliminarily sets the switching mechanism to a locked state. This preliminary action eliminates the need for continuous user input during operation, as the latch automatically maintains the closed circuit state without further user intervention.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The switching mechanism serves itself by using the latch and pawl arrangement to automatically maintain the locked position once activated. The pawl engages with the notched element to self-sustain the closed circuit state, and the spring automatically returns the mechanism to its initial state when deactivated, eliminating the need for continuous user control.

Inventive Principle:
Principle #25Self-service

2Ease of operation

If a locking mechanism is added to enable continuous operation, then user fatigue is reduced, but the device complexity increases

Engineering Contradiction:
Improvehands-free operation capabilityVSAvoidlocking switch mechanism
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The locking switch is segmented into distinct functional elements: the actuating element for user input, the pawl for locking engagement, the notched element for positioning, and the spring for resetting. This segmentation allows each component to perform its specific function simply, reducing overall complexity compared to a monolithic locking mechanism.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Instead of requiring continuous activation to maintain operation, the mechanism is inverted to require a single deactivation action. The latch normally maintains the locked state and can be released by a simple pressing action, reversing the conventional approach where continuous input is needed to maintain the active state.

Inventive Principle:
Principle #13The other way round (Inversion)

3Duration of action of stationary object

If the latch engages the operating button to inhibit it in the pressed position, then continuous operation is maintained, but the switching mechanism must be robust against dust and wear

Engineering Contradiction:
Improvecontinuous motor activationVSAvoidswitching mechanism durability
Core Design Contradiction:
Duration of action of stationary objectVSReliability

Solution Approach 1:

The switching mechanism uses simple, easily replaceable mechanical components such as the pawl, notched element, and spring. These components are designed to be robust and durable, but if wear or contamination occurs, they can be easily replaced without affecting the overall tool, ensuring long-term reliability through maintainability rather than complexity.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

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 continuous tool operation without user fatigue, enhancing user convenience and efficiency by allowing hands-free activation and deactivation of the electric motor.

Implementation Method 1

The latch has a spring that applies force to the latch in the opposite direction to the pivoting direction

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 2

The latch has a guide surface on one side facing in the pivoting direction that is inclined relative to the sliding direction

Methodology Applied
Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentEP3802000B1Handheld machine tool
Publication Date: 2025.08.06 HILTI AG
  • EP3802000B1 patent drawingFigure 1~2
  • EP3802000B1 patent drawingFigure 3~4
  • EP3802000B1 patent drawingFigure 5~7

AI summary

The invention relates to a hand-held power tool with a motor-driven impact mechanism (14) and a monostable operating switch (6). A locking switch (28) for the monostable operating switch (6) has a slide direction (36), an actuation knob (35), a latch (29), and a slider block (41). The actuation knob (35) can be moved along the slide direction (36) from a release position into a locking position by the user. The latch (29) can be pivoted between a first position and a second position in a pivot direction (31) perpendicular to the switch direction (23). The latch (29) is not in engagement with the operating switch (6) in the first position and engages into the operating switch (6) in the second position so as to block the operating switch (6) in the pressed position. The latch (29) has a slide surface (40), which is inclined in the slide direction (36), on the face facing the pivot direction (31). The slider block (41) lies against the slide surface (40).