Elevator Rescue via Gravity-Driven Brake Release
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Solution Overview
Problem
Conventional automatic rescue operation systems for elevators face challenges in determining the correct direction for rescue runs, leading to increased peak currents and energy consumption, especially when load weighing devices fail or provide incorrect signals, resulting in potential misdirection of the elevator car.
Innovation Solution
The system performs a power-limited automatic rescue run by lifting the brake without providing holding torque, allowing gravity to guide the car in the lighter direction, and synchronizing the hoist motor with the car's motion to control the rescue run, eliminating the need for precise load balancing and reducing peak current requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If load weighing devices are used to determine the light direction for rescue runs, then the system can attempt to drive the car in the correct direction, but the peak current and energy consumption increase significantly when load weighing fails or provides incorrect signals
Solution Approach 1:
Instead of using load weighing devices to determine the light direction and risking erroneous attempts to drive in the heavy direction, the invention inverts the approach by releasing the brake and allowing gravity to naturally guide the car in the correct direction. This eliminates the need for load weighing signals and prevents erroneous reverse-direction attempts, thereby reducing peak current and energy consumption while improving reliability.
Solution Approach 2:
The invention converts the potential harm of load weighing failure into a benefit by using gravity as the primary guiding force. By releasing the brake and allowing the car to move under gravity's influence, the system transforms the uncertainty of load weighing into a reliable gravitational guide, ensuring the car moves in the light direction without requiring accurate load measurements.
2Use of energy by moving object
If the brake is lifted and the car is allowed to move by gravity, then the peak current requirements are reduced, but the system must handle cases where the car does not move due to balanced loads
Solution Approach 1:
The invention implements feedback by sensing whether the car is moving after the brake is released. If the car is not moving (indicating a balanced load condition), the system responds by supplying backup power to the hoist motor to drive the car in the selected direction. This feedback mechanism simplifies the overall system by using simple motion sensing rather than complex load weighing, while still handling the balanced load case effectively.
Solution Approach 2:
The system allows gravity to self-guide the car movement without requiring active control during the initial phase. By releasing the brake and letting gravity take over, the system reduces the need for complex active control and power management, simplifying the overall device while maintaining effectiveness in unbalanced load conditions.
3Reliability
If backup power is dimensioned to deliver peak hold current for maximum load, then the system can handle any load condition, but the size and cost of the backup power supply increase significantly
Solution Approach 1:
The invention inverts the conventional approach of dimensioning backup power for peak hold current by instead allowing gravity to provide the primary driving force. By releasing the brake and using gravity to move the car, the system reduces the backup power requirements from peak hold current levels to much lower levels needed only for synchronized motor control and handling balanced load cases, significantly reducing the size and cost of the backup power supply.
Solution Approach 2:
The invention changes the operating parameters of the backup power system by transitioning from a high-power hold-current mode to a low-power gravity-assisted mode. By dimensioning the backup power supply based on the reduced power needs of the gravity-driven system rather than peak electrical drive requirements, the system achieves the same reliability with a much smaller and less expensive power supply.
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 approach reduces the size and cost of the backup power supply, minimizes energy storage needs, and avoids erroneous attempts to move the car in the heavy direction, ensuring safe and efficient rescue operations without relying on accurate load weighing signals.
Implementation Method 1
If a significant imbalance in weight exists between the car and a counterweight, gravity will cause the car to move into the light direction
Data Source
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AI summary
When main power to an elevator system 10 is lost, an automatic rescue operation is performed using power from a backup power source 46. A rescue run for an elevator stopped between floors is initiated by lifting a brake 28 and allowing the elevator car 12 to move by gravity. If the car 12 moves as a result of a weight imbalance between the car 12 and a counterweight 14, operation of the hoist motor 24 is synchronized with sensed movement of the car 12 to generate electricity. If weight is balanced so that the car 12 does not move, backup power is supplied to the hoist motor 24 to apply a motor torque to drive the car 12 in a selected direction during the rescue run.