Thermal Actuator with Bistable Latch for Zero-Power Position Holding
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Solution Overview
Problem
Thermal and electrothermal actuators require continuous electric power to maintain stable angular positions, leading to high energy consumption and mechanical stress, especially in applications where long-term force exertion is necessary.
Innovation Solution
A thermal or thermoelectric actuator device with a movable member equipped with stopping and engaging means, allowing it to hold a rotary or angular movement without continuous power, using a combination of a rack and pinion mechanism with elastomeric coupling surfaces and a spring system to achieve stable positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous electric power is supplied to maintain stable angular positions, then the actuator can hold positions reliably, but energy consumption increases and mechanical stress increases
Solution Approach 1:
The patent applies periodic action by using a bistable mechanism that alternates between two stable positions. The actuator only consumes energy during transitions between positions, not during position holding. The mechanism uses a spring-loaded latch system that periodically engages with teeth on the pinion to maintain positions without continuous power supply.
Solution Approach 2:
The patent replaces the electrical holding system with a mechanical bistable system. Instead of using continuous electrical power to maintain position, the invention uses a mechanical latch with spring force and geometric constraints (teeth engagement) to create two stable equilibrium positions, eliminating the need for continuous energy input.
2Reliability
If continuous electric power is supplied to maintain stable angular positions, then the actuator can hold positions reliably, but mechanical stress on the actuator increases
Solution Approach 1:
The bistable mechanism creates periodic engagement cycles where the latch only interacts with the pinion teeth during position transitions. During position holding, the mechanical latch bears the load through its geometric constraints and spring force, not the actuator, significantly reducing continuous mechanical stress and preventing premature failure.
Solution Approach 2:
The patent substitutes the actuator's continuous force output with a passive mechanical latch system. The latch uses spring force and geometric interlocking (teeth engagement) to hold positions, transferring the holding function from the active actuator to the passive mechanical system, thereby reducing stress on the actuator components.
3Stability of the object's composition
If abutment elements are used to physically stop the movable part, then stable positions are achieved, but the actuator must remain operational and consume power
Solution Approach 1:
The patent segments the position holding function from the position actuation function. The abutment elements (latch and teeth) are separated as distinct mechanical components that provide passive position stability, while the actuator only provides active force during transitions. This segmentation allows stability without continuous power consumption.
Solution Approach 2:
The mechanical latch acts as an intermediary between the actuator and the controlled member. It receives the actuator's periodic motion and converts it into stable position holding through geometric constraints and spring force, eliminating the need for the actuator to remain operational during position maintenance.
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 actuator device reduces energy consumption by only requiring power for position switching, maintaining stable angular positions without continuous power, and withstands high mechanical stresses without thermal excitation or electric power.
Implementation Method 1
subject to the elastic reaction of a spring for repositioning the movable shaft or piston when the electric supply or excitation stops
Implementation Method 2
which is moved by the wax expanding when heated by an electric resistor
Data Source
AI summary
A device is described wherein an actuator (3, 4; 103, 104) drives a member, such as a rack (6) meshed with a pinion (5), between two stable positions. For this purpose, elements for stopping the movable member are provided, which cooperate with elements present on the outer housing (2, 21), in which the actuator and the movable member (5, 51) are arranged, for holding at least one of said stable conditions. The device of the invention ensures low energy consumption because the actuator (3) only operates for moving the movable member from one stable position to the other.