Rotary Latch Gear Train Actuation and Self-Return
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Solution Overview
Problem
Existing rotary latches with powered actuators are often complex and require modifications to the catch and pawl design, and they struggle with self-return action, especially when controllers dynamically brake the motor.
Innovation Solution
A rotary latch design that includes a gear train with a motor and pinion driving a bevel gear and pinion, which engages an idler gear to drive the pawl to a catch-releasing position, allowing for self-return action using a torsion spring, with the option of a supplemental spring for additional force, and minimal modification to existing latch constructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a powered actuator is added to a rotary latch, then automated actuation is achieved, but device complexity increases and requires modification of catch and pawl design
Solution Approach 1:
The actuator housing is designed to serve multiple functions: it houses the motor, contains the gear train mechanism, and integrates with the existing latch housing structure. This multi-functionality reduces the need for separate components and minimizes overall device complexity while achieving automated actuation
Solution Approach 2:
A gear train with idler gear is introduced as an intermediary mechanism between the motor and the pawl. This gear train translates the motor's rotational motion into the appropriate motion for actuating the pawl, enabling automated operation without requiring direct modification of the catch and pawl design
2Loss of time
If existing spring is used for biasing, then self-return action is achieved, but the mechanism fails when controller dynamically brakes the motor
Solution Approach 1:
The system transitions from a purely passive spring-based return mechanism to a dynamic system where the motor can actively assist the return action. The motor controller is configured to allow the motor to drive the pawl back to the catch-releasing position even when dynamically braking, ensuring reliable operation under various control conditions
Solution Approach 2:
The motor control parameters are adjusted to accommodate dynamic braking conditions. The controller is configured to permit the motor to overcome the dynamic braking force and still drive the gear train and pawl to the required position, changing the operational parameters to maintain reliability
3Ease of operation
If lighter torsion spring is used, then ease of operation is improved, but insufficient force is available for self-return action
Solution Approach 1:
The gear train acts as a mechanical advantage system, providing force multiplication. This allows a lighter torsion spring to generate sufficient force for self-return action through the mechanical advantage provided by the gear ratios in the intermediate transmission system
Solution Approach 2:
The addition of a supplemental spring mounted on the idler gear provides additional force assistance. This supplemental spring works in conjunction with the main torsion spring to ensure adequate force is available for self-return action while maintaining ease of operation
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 simple and adaptable powered actuation of rotary latches with self-return functionality, even when the motor is not powered, and requires minimal modification to existing mechanical latches, ensuring reliable operation across various spring rates.
Implementation Method 1
One or more torsion springs extend principally within a secondary plane located adjacent to the primary plane and extending parallel thereto. The torsion spring has a first hook that extends out of the secondary plane into the primary plane where it engages the catch to bias the catch away from its latched position toward its unlatched position.
Data Source
AI summary
A rotary latch has a housing having first and second posts therein. A catch is mounted for rotation about the first post between latched and unlatched positions. A pawl is mounted for rotation about the second post between a catch-retaining position and a catch-releasing position. When the catch is in the latched position and the pawl is in the catch-retaining position, the pawl engages the catch and prevents it from rotating out of the latched position. When the pawl is in the catch-releasing position the catch is movable to its unlatched position. A motor and gear train mounted in the housing includes an output gear mounted for rotation about the second post. The output gear is in engagement with the pawl such that activation of the motor causes the output gear to rotate the pawl to the catch-releasing position.