Compact Drive Unit for Transit Doors with Segmented Gears
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Solution Overview
Problem
Existing drive apparatuses for boarding and unboarding devices, such as passenger doors and retractable steps on public transport vehicles, face difficulties in manual operation during emergencies due to high self-locking phenomena caused by high reduction ratios, making manual movement extremely difficult or impossible.
Innovation Solution
The drive apparatus is designed with a compact construction that divides the overall reduction gear into two individual gears coupled through a disengageable clutch, allowing for manual operation by reducing the self-locking effect, utilizing planetary gears and an electromagnetically releasable brake, with the clutch engaging under a spring and actuated by a Bowden cable for emergency unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high reduction ratio gear is used in the drive apparatus, then the torque transmission efficiency is improved, but the self-locking phenomenon increases making manual operation difficult or impossible
Solution Approach 1:
The patent divides the single high reduction ratio gear into two separate reduction gears with lower individual ratios. The first reduction gear has a ratio of 5:1 to 10:1 and the second has a ratio of 10:1 to 20:1, both coupled through a clutch. This segmentation reduces the self-locking effect of each individual gear while maintaining the overall high reduction ratio for torque transmission.
2Power
If the overall reduction ratio is increased to improve torque transmission, then the power transmission capability is improved, but the device complexity increases
Solution Approach 1:
The gear system is segmented into two distinct reduction stages, each with manageable complexity. The first reduction gear and second reduction gear are separate units connected by a clutch, allowing each to be optimized independently while achieving the cumulative torque multiplication of a much higher overall ratio.
Solution Approach 2:
A clutch is introduced as an intermediary element between the two reduction gears. This clutch allows for controlled engagement and disengagement, providing flexibility in operation and simplifying the control logic compared to a single complex gear system with fixed high reduction ratio.
3Ease of operation
If a disengageable clutch is introduced to enable manual operation, then the manual operation capability is improved, but the device complexity increases
Solution Approach 1:
The clutch serves as a simple intermediary mechanism that can be actuated by a Bowden cable from the exterior. This external actuation method avoids the need for complex internal release mechanisms, keeping the clutch structure relatively simple while enabling easy manual operation during emergencies.
Solution Approach 2:
The manual release mechanism uses a Bowden cable system that replaces complex mechanical linkages. The cable can be pulled from the exterior to disengage the clutch, simplifying the internal mechanical structure while providing reliable emergency release capability.
4Volume of moving object
If a compact axial arrangement is used to reduce space occupation, then the volume is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent arranges the two reduction gears and clutch in an axial configuration along the rotation axis, utilizing the longitudinal dimension efficiently. This axial stacking minimizes the radial space occupation while maintaining adequate clearance for manufacturing tolerances, achieving compactness without excessive precision requirements.
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 manual operation in emergency situations by overcoming self-locking issues, allowing for efficient and accessible manual control of boarding and unboarding devices, while maintaining a compact and aesthetically integrated design.
Implementation Method 1
the first reduction gear with the drive motor and the first clutch half are connected together axially by the action of a compression spring to the second clutch half and to the second reduction gear
Implementation Method 2
In the case of an emergency, a Bowden cable tensions the spring and axially displaces the drive motor, the reduction gear and the clutch half in the outer tube so that the force transmission is interrupted at the clutch
Implementation Method 3
an electromagnetically releasable brake, which acts by the action of a spring upon the driven shaft
Data Source
AI summary
A drive apparatus for boarding and unboarding devices, in particular for passenger doors, boarding ramps, retractable steps and the like on public transport vehicles having an electric drive motor the driven element of which is connected to the input element of a first reduction gear the output element of which is coupled to the actuation devices for the boarding and unboarding devices where the drive apparatus is constructed as a compact drive where the electric drive motor, the first reduction gear and a second reduction gear as well as an energizable clutch are disposed axially behind each other inside a tubular housing between the first reduction gear and the second reduction gear.