Transit Door Operator with Drum Cam Emergency Release
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Solution Overview
Problem
Existing door operators for transit vehicles face challenges in limited mounting space and the need for a manual release mechanism that can be operated with minimal force, while ensuring doors cannot be opened by passengers leaning against them during vehicle movement.
Innovation Solution
An electric door operator system with a rotatable input shaft driven by an electric motor, featuring a teeter assembly with journal bearings, gear engagement mechanisms, and a mechanical release mechanism that allows for axial movement of pinions and gears to enable manual door opening with minimal force, incorporating a drum cam and disengagement lever for emergency release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a mechanical release mechanism is added to allow manual door opening, then emergency accessibility is improved, but device complexity increases
Solution Approach 1:
The release mechanism is nested within the existing door operator structure. The cable actuates a lever that rotates a cam, which then lifts the pinion gear off the drive shaft. This nested arrangement allows the emergency release function to be integrated into the compact door operator without adding external complexity.
Solution Approach 2:
The mechanical release mechanism is designed to be self-actuating through cable tension. When the cable is pulled, it automatically triggers the sequence of lever rotation, cam engagement, and pinion disengagement without requiring additional power sources or complex control systems.
2Reliability
If an electric motor with brake is used to prevent door opening during vehicle movement, then safety is improved, but the force required for manual release increases
Solution Approach 1:
The cam mechanism is pre-positioned in the housing to receive the pinion gear. When the release cable is actuated, the cam rotates into position and automatically lifts the pinion off the drive shaft, preparing the path for manual door opening before the actual pulling force is applied by the passenger.
Solution Approach 2:
The cam acts as an intermediary mechanism between the release cable and the pinion gear. It translates the small force applied to the cable into a larger lifting motion that overcomes the brake force, reducing the manual release force requirement to under 20 pounds.
3Adaptability or versatility
If the mounting space is reduced to fit vehicle door constraints, then adaptability is improved, but the mechanism becomes more difficult to manufacture
Solution Approach 1:
The door operator is divided into modular segments: motor assembly, brake assembly, gear train, and housing. Each segment can be manufactured and tested independently, then assembled into the compact configuration required for vehicle door mounting. This segmentation maintains ease of manufacture while achieving space efficiency.
Solution Approach 2:
The mechanism utilizes three-dimensional spatial arrangement within the housing, stacking components vertically and radially rather than only linearly. The cam mechanism rotates in a vertical plane while the pinion gear engages radially, effectively using multiple dimensions to pack the mechanism into a compact footprint.
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 system effectively manages door operation with efficient torque transfer and minimal back-drive force, allowing passengers to manually open doors in emergencies with a 20-pound pull force, while preventing accidental opening by passengers during vehicle movement.
Implementation Method 1
An electric motor is secured to the input shaft for driving the input shaft
Implementation Method 2
an electric brake mounted to the input shaft
Implementation Method 3
a teeter mounted thereon with journal bearings at at least one end thereof for engagement with drive bars
Implementation Method 4
A first stage pinion positioned on the input shaft... An output gear is fixed to the output shaft for driving the output shaft
Data Source
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AI summary
An electric door operator for opening and closing one or a spaced pair of transit vehicle passenger doors for being mounted over an opening for the doors. A rotatable input shaft has an electric motor secured to the input shaft for driving the input shaft, a worm centrally positioned on the motor shaft, and an electric brake mounted to the input shaft at an end opposite of the electric motor. A drum cam lifts a pinion from a worm gear disconnecting the worm gear from an output gear train in an emergency.