Elevator Emergency Stop Device with Dynamic Spring Linkage
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Solution Overview
Problem
Existing emergency stop devices for elevator cars require a large buffer and a mechanism for reliable rope breakage detection, and fail to prevent the rail stopper from being moved up during hoisting machine braking, leading to increased operation time during rope breakage.
Innovation Solution
An emergency stop device with a link, rail stopper, roller guide, and an elastic member with a spring reaction force that remains inactive during hoisting machine braking but reduces to enable rapid rail stopper movement during rope breakage, eliminating the need for a large buffer and reliable detection mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring reaction force is applied to prevent the rail stopper from moving up during hoisting machine braking, then the rail stopper remains stable during normal braking, but the time required to start the emergency stop device operation increases at the time of rope breakage
Solution Approach 1:
The spring reaction force is designed to be dynamic rather than static - it automatically adjusts its magnitude based on the acceleration conditions. During normal braking, the spring maintains a restraining force on the rail stopper. During rope breakage, when acceleration exceeds a threshold, the spring force is overcome and the rail stopper is rapidly released. This dynamic characteristic resolves the contradiction by providing both stability during normal operation and rapid response during emergencies.
Solution Approach 2:
The system changes the parameter of spring reaction force based on acceleration conditions. The spring is selected with specific elastic characteristics that allow it to maintain force under normal braking acceleration but yield when acceleration exceeds the rope breakage threshold. This parameter change enables the system to transition from a restrained state to an active emergency stop state, resolving the time delay contradiction.
2Reliability
If a large spring reaction force is used to prevent false activation during braking, then the rail stopper remains firmly held, but a large-size buffer is required to accommodate the delayed emergency stop response
Solution Approach 1:
The dynamic spring characteristic allows the system to use a relatively small buffer while maintaining firm holding during normal braking. The spring force is sufficient to prevent false activation during standard braking operations but can be rapidly overcome when rope breakage occurs. This eliminates the need for an oversized buffer that would be required if a static, always-active restraining force were used.
Solution Approach 2:
The spring provides preliminary restraining action during normal braking to prevent false activation of the emergency stop device. However, this preliminary action is designed to be overcome by the much larger forces generated during actual rope breakage. This selective anti-action allows the use of a compact buffer while maintaining reliability during normal operations.
3Speed
If the rail stopper is allowed to move up freely during hoisting machine braking, then the emergency stop device can activate quickly during rope breakage, but the rail stopper may be incorrectly activated during normal braking operations
Solution Approach 1:
The spring reaction force parameter is specifically selected to change state based on acceleration thresholds. During normal braking, the spring maintains sufficient force to hold the rail stopper down. During rope breakage, the excessive acceleration causes the spring force to be overcome, allowing rapid rail stopper movement. This parameter-based discrimination resolves the contradiction between quick activation and accurate detection.
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 device effectively prevents rail stopper movement during hoisting machine braking and quickly activates during rope breakage, reducing the need for a large buffer and reliable detection mechanisms, thus enhancing operational efficiency.
Implementation Method 1
an elastic member provided between another end of the link and the car, in which the elastic member has a spring reaction force which prevents the rail stopper from being brought into abutment against the roller guide
Implementation Method 2
the elastic member has a characteristic which causes the spring reaction force to be reduced to bring the rail stopper into abutment against the roller guide when the displacement exceeds a preset threshold value
Data Source
AI summary
An emergency stop device for an elevator car, including: a link configured to be rotated about a rotary shaft installed on a car by movement of a speed governor rope; a rail stopper provided to one end of the link; a roller guide mounted to the car; and an elastic member provided between another end of the link and the car. The elastic member causes a spring reaction force to be reduced to bring the rail stopper into abutment against the roller guide even when the rail stopper is displaced by the link, when the displacement exceeds a preset threshold value due to further displacement by the link along with the movement of the speed governor rope at a time of occurrence of rope breakage.