Elevator Safety Gear Tripping via Lightweight Actuator
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Solution Overview
Problem
Conventional elevator overspeed governors are unable to reliably trip the safety gear at speeds lower than the gripping speed, particularly when the elevator moves unintentionally from the floor level, and require large forces and costly modifications to prevent creeping, which can lead to malfunctions.
Innovation Solution
A lightweight actuator is used to control the connection of the brake to the rope sheave, allowing the safety gear to trip at a speed lower than the gripping speed, with a separate force means disconnecting the actuator from the rope sheave, and the overspeed governor's internal structure sets a distance for free rotation to prevent unnecessary gripping, enabling adjustable tripping forces and reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional overspeed governors are used to trip the safety gear, then the safety gear can be tripped at high speeds, but it cannot reliably trip the safety gear at speeds lower than the gripping speed
Solution Approach 1:
A lightweight actuator is introduced as an intermediary mechanism between the rope sheave and the safety gear tripping mechanism. This actuator translates the rotational movement of the rope sheave at low speeds into the necessary activation force for the safety gear, enabling reliable tripping below the conventional gripping speed without requiring the full force of overspeed conditions
Solution Approach 2:
The tripping mechanism is segmented into separate functional components: the rope sheave for speed monitoring, the lightweight actuator for motion translation, and the safety gear activation system. This segmentation allows the actuator to specialize in low-speed motion detection and transmission, while the safety gear handles the tripping function, enabling operation at speeds below the conventional gripping threshold
2Reliability
If locking devices are added to prevent creeping, then the permitted length of unintended movement can be controlled, but the device complexity and cost increase
Solution Approach 1:
The lightweight actuator serves multiple functions: it enables low-speed tripping activation, provides creeping prevention through controlled movement permission, and acts as a force amplifier. By making the actuator multi-functional, the system achieves creeping prevention and low-speed tripping capabilities without adding separate locking devices, thus avoiding increased device complexity
Solution Approach 2:
The actuator is designed to automatically distinguish between permitted creeping movement and unintended movement requiring tripping. Through its mechanical design with defined dead zones and activation thresholds, the actuator self-regulates when to permit movement and when to trigger safety gear activation, eliminating the need for external control systems or complex locking mechanisms
3Reliability
If large forces are applied to creep monitoring appliances, then the permitted movement can be strictly controlled, but the appliances become expensive and prone to malfunction
Solution Approach 1:
The system uses a spring-loaded counterbalancing mechanism that offsets the gravitational force acting on the elevator car during creeping. The spring force is calibrated to match the weight of the car, creating a balanced system where the actuator only needs to detect small deviations from the equilibrium position rather than counteract the full weight, significantly reducing the force requirements on the monitoring appliance
Solution Approach 2:
Instead of applying full braking force or large counteracting forces to prevent all movement, the system applies a lightweight actuator that only engages when movement exceeds a small predetermined threshold. This partial action approach allows permitted creeping within safe limits while triggering safety gear activation only when necessary, reducing the force requirements on the monitoring appliance while maintaining reliability
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 solution allows reliable and efficient tripping of the safety gear at lower speeds, preventing elevator creeping, is cost-effective, and adaptable to various overspeed governors, ensuring fail-safe operation with minimal modifications and reduced precision requirements.
Implementation Method 1
a brake (5), the brake force of which can be set to be suitable, is fixed to the axle (2) next to the rope sheave (3)
Implementation Method 2
two eccentric cams (15) situated above the brake disc (6)... are mounted on a turning bearing, said cams being connected by two curved, essentially symmetrically-shaped centrifugal weights (16)
Data Source
Figure 1
Figure 2
AI summary
Safety gear of an elevator tripped at a speed lower than the gripping speed of the elevator. Tripping of the safety gear in an overspeed situation is arranged to occur by means of the rope driving the overspeed governor via a rope sheave (3) . Connection of the brake (5) or other device that slows the rope sheave to the rope sheave (3) is controlled using an actuator, which disconnects from the movement of the rope sheave when the brake or other device that slows the rope sheave connects to brake the movement of the rope sheave.