Power Tool RC Circuit for Thermal Hold After Power-Off

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Solution Overview

Problem

Portable pipe threaders face thermal overload issues due to rising temperatures in components like motors and gearboxes, which can exceed thermal thresholds during operation, leading to potential damage.

Innovation Solution

The implementation of a resistor-capacitor (RC) circuit within the power tool's electrical circuit, which stores voltage proportional to the tool's temperature, allowing the electronic controller to determine temperature post-power off and control tool operation based on temperature thresholds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the power tool operates continuously to maintain productivity, then productivity is improved, but thermal overload risk increases

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoidthermal overload protection

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The RC circuit stores thermal information (voltage proportional to temperature) before a power off event occurs, preserving the thermal state data so that when power is restored, the controller can immediately resume thermal monitoring without losing track of the thermal condition, thus maintaining both continuous operation capability and thermal protection

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If the controller loses thermal information during power off events, then device complexity is reduced, but temperature modeling accuracy deteriorates

Engineering Contradiction:

Improvethermal monitoring systemVSAvoidtemperature modeling accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The RC circuit acts as an intermediary element that bridges the gap between power states, storing thermal information in electrical form (voltage) that can be preserved across power off events and later read by the controller to maintain accurate temperature modeling without requiring complex active monitoring systems during idle states

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively maintains thermal information during power off events, preventing inaccurate temperature modeling and ensuring the power tool operates safely within thermal limits.

Implementation Method 1

The RC circuit arrangement is configured to store a voltage on a capacitor of the RC circuit arrangement. The voltage is proportional to a temperature of the power tool.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20250073884A1Power tool including a circuit for holding a thermal reference

Publication Date: 2025.03.06 MILWAUKEE ELECTRIC TOOL CORP

AI summary

Power tools including a housing, an electrical circuit, and the housing. The housing includes a battery pack interface configured to receive a battery pack. The electrical circuit includes a resistor-capacitor (“RC”) circuit arrangement configured to store a voltage on a capacitor. The voltage is proportional to a temperature of the power tool. The electronic controller is connected to the electrical circuit and includes an electronic processor and a memory. The electronic controller is configured to control a voltage applied to the RC circuit arrangement, and determine, in response to determining a power off event of the power tool has ended, the temperature of the power tool based on the voltage of the capacitor of the RC circuit arrangement. The controller is also configured to control the power tool based on the voltage of the capacitor of the RC circuit arrangement and a temperature threshold.