Retractable Stop for Elevator Overhead Clearance
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Solution Overview
Problem
Modern elevator systems, especially machine roomless types, often have low overhead clearance during maintenance or inspection, posing safety risks for personnel as they lack sufficient space above the elevator car for safe access.
Innovation Solution
An assembly that includes a stop member automatically moving to limit the counterweight's downward movement, triggered by safety devices or sensors detecting personnel on top of the elevator car, ensuring the car does not rise above a certain height within the hoistway, thereby maintaining a safe overhead clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If machine roomless elevator systems are used to reduce overhead structure, then the overhead clearance above the elevator car is reduced, but safety for personnel during maintenance or inspection is compromised
Solution Approach 1:
The stop member is designed to be dynamically positionable between a retracted position (during normal operation) and an extended position (during maintenance/inspection). This dynamic adjustment allows the system to adapt to different operational modes, providing overhead clearance when needed while maintaining normal operation efficiency.
Solution Approach 2:
The stop member acts as an intermediary safety device between the counterweight and the hoistway overhead structure. It mediates the conflict by limiting counterweight descent (and thus car ascent) to a predetermined extent, creating a safety buffer zone without requiring permanent reduction of overhead clearance.
2Reliability
If the stop member is extended to limit counterweight movement, then overhead clearance is maintained, but the range of motion of the counterweight and elevator car is restricted
Solution Approach 1:
The stop member limits counterweight movement to a predetermined extent rather than completely restricting motion. This partial action provides sufficient overhead clearance for personnel safety while allowing the elevator car to still reach most of its normal operational height, balancing safety requirements with operational needs.
3Ease of operation
If a powered actuator is used to move the blocking device, then the stop member can be positioned accurately, but device complexity increases
Solution Approach 1:
The stop member is designed to be manually positionable by maintenance personnel without requiring powered actuators or complex control systems. This self-service approach reduces device complexity while still achieving accurate positioning when needed, as the manual operation is simple and direct.
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 solution effectively maintains a safe overhead clearance above the elevator car during maintenance or inspection, preventing the car from rising too high and ensuring personnel have sufficient space for safe access, enhancing safety in low-clearance elevator systems.
Implementation Method 1
A stop member automatically moves responsive to an indication from the safety device from a retracted position to an employed position where the stop member limits movement of the counterweight in a downward direction
Data Source
Figure 1
Figure 2~4
AI summary
An assembly (30) controls the amount of downward movement of a counterweight (24) within an elevator system (20). By limiting the downward movement of the counterweight (24), a desired overhead clearance above an elevator car (22) can be maintained. A disclosed example includes at least one safety device (80, 84, 86, 88) on top of the elevator car (22) to provide an indication for when a holding member (34) should allow a stop member of the assembly (30) to move into a position to limit the downward movement of the counterweight (24). In a disclosed example, the stop member (32) moves into an employed position by the force of gravity and is manually moveable back into a retracted position when it is not needed. A disclosed example includes a guide member (60) that facilitates controlling the position of the stop member (32) when it is in the employed position.