Elevator Brake Rotor Engagement via Speed Sensing Latch
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Solution Overview
Problem
Elevators face the risk of uncontrolled free fall due to powerhead failures, particularly in residential elevators with limited time to stop or slow motion, posing a risk to people and objects.
Innovation Solution
A brake system for elevator powerheads, including a brake rotor, brake member, actuation lever, biasing member, speed sensing arrangement, and latch arrangement, which engages the brake when a predetermined rotational speed is sensed, preventing the elevator car from falling by stopping or slowing the cable drum rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brake system is added to existing powerheads, then safety against free fall is improved, but device complexity increases
Solution Approach 1:
The brake system is divided into separate functional components: a brake rotor that rotates with the cable drum, a brake member that selectively engages the rotor, an actuation lever with first and second positions, a biasing member, a speed sensing arrangement, and a latch arrangement. This segmentation allows each component to perform its specific function independently while maintaining overall system reliability without excessive complexity.
Solution Approach 2:
The brake member is pre-positioned in the first position where the brake rotor is free to move, and the biasing member is pre-loaded to automatically bias the actuation lever toward the second position. The latch arrangement is pre-configured to maintain the first position until overspeed is detected. This preliminary arrangement ensures that the brake is ready to engage immediately when needed, without requiring complex control systems.
2Measurement precision
If a speed sensing arrangement with latch arrangement is implemented, then overspeed detection capability is improved, but device complexity increases
Solution Approach 1:
The speed sensing arrangement automatically detects when the cable drum rotates at or above the predetermined overspeed threshold. Upon detection, the sensing arrangement triggers the latch arrangement to transition from its first orientation (maintaining the brake in the released first position) to its second orientation (releasing the brake). This self-activating mechanism eliminates the need for external control systems or complex electronics, achieving precise overspeed detection with minimal added complexity.
3Reliability
If the brake member is biased into engagement position, then braking reliability is improved, but ease of operation during normal operation worsens
Solution Approach 1:
The brake system dynamically transitions between two states: during normal operation, the latch arrangement maintains the actuation lever in the first position where the brake rotor is free to move with the cable drum; upon overspeed detection, the latch arrangement automatically releases, allowing the biasing member to drive the actuation lever to the second position where the brake member engages the brake rotor. This dynamic state transition ensures braking reliability when needed while maintaining ease of operation during normal conditions.
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 brake system effectively prevents uncontrolled descent by engaging the brake when an overspeed condition is detected, ensuring safety by retrofitting existing powerheads and providing battery backup for operation during power failures.
Implementation Method 1
The brake member actuation lever has a first position in which the brake rotor is free to move relative to the brake member and a second position in which the brake member is biased into engagement with the brake rotor
Implementation Method 2
engagement of the brake member with the rotor reducing or stopping rotational motion of the rotor and cable drum
Data Source
AI summary
An overspeed brake system for use in an elevator powerhead is provided. A brake rotor is attachable to a cable drum to rotate with a cable drum. A brake member selectively engages the brake rotor upon transition of an actuation lever from a first position to a second position. A biasing member acts on the actuation lever to bias the actuation lever from the first position towards the second position. A latch arrangement has a first orientation maintaining the actuation lever in the first position and a second orientation releasing the actuation lever for transitioning from the first position to the second position. The latch arrangement transitions from the first orientation to the second orientation when a speed sensing arrangement senses that the rotational speed of the cable drum is at least a predetermined rotational speed.