Elevator Speed Limiter Dual Pendulum Triggering
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Solution Overview
Problem
Conventional speed limiters in elevator installations have limitations, including fixed trigger values, high spring forces leading to vibrations and noise, and inadequate accessibility for installations without engine rooms, resulting in delayed safety brake activation and compromised travel comfort.
Innovation Solution
The design introduces two separate pendulums with different moments of inertia and biasing forces acting on a common cam disc, allowing for distinct and adjustable trigger values for pre-contact speed and safety brake activation, along with phase-displaced control cams to reduce vibrations, and electrical/electronic speed monitoring for remote triggering and resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single pendulum with fixed parameters is used, then the structure is simple, but the trigger values cannot be adjusted for different operational phases
Solution Approach 1:
The single pendulum system is segmented into two separate pendulums (first and second pendulums), each with independently adjustable parameters. This allows the first pendulum to be optimized for assembly phase triggering while the second pendulum handles normal operational triggering, providing adaptability without requiring complex adjustment mechanisms in a single system.
Solution Approach 2:
The speed limiter system is designed to perform multiple functions through two pendulums: one dedicated to assembly phase safety monitoring with lower trigger values, and another for normal operation with higher trigger values. This multi-functional design eliminates the need to reconfigure a single pendulum system for different operational phases.
2Reliability
If high spring forces are used for triggering, then the safety brake activation is reliable, but vibrations and noise increase
Solution Approach 1:
The triggering function is segmented between two separate pendulums with different spring force requirements. The first pendulum uses lower spring forces appropriate for assembly phase operations, while the second pendulum uses higher spring forces for normal operation. This segmentation allows each pendulum to operate in its optimal force range, reducing unnecessary vibrations and noise.
Solution Approach 2:
The system changes the parameter of spring force by using two different pendulums with differently biased springs. The first pendulum has a lower biasing spring force suitable for reduced-speed assembly operations, while the second has a higher biasing spring force for normal-speed operations. This parameter differentiation reduces harmful vibrations and noise by matching spring force to operational context.
3Speed
If the speed limiter is designed for high-speed operation, then the rated speed capability is improved, but the travel comfort deteriorates due to increased vibrations
Solution Approach 1:
The speed monitoring function is segmented into two independent pendulum systems operating at different sensitivity levels. The first pendulum monitors at lower speeds during assembly with minimal vibration impact, while the second pendulum monitors at higher normal operating speeds. This segmentation allows the system to maintain high rated speed capability while isolating vibration-generating events to only when truly necessary.
Solution Approach 2:
The system changes the operational parameters by using two pendulums with different moments of inertia and spring forces. The first pendulum is optimized for low-speed assembly phase detection, while the second is optimized for high-speed normal operation. This parameter differentiation enables the elevator to achieve high rated speeds while maintaining travel comfort, as the sensitive first pendulum does not generate vibrations during normal high-speed operation.
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 enables rapid and independent triggering actions, reduced vibrations and noise, improved safety, and remote operation of the speed limiter, enhancing travel comfort and accessibility in installations without engine rooms.
Implementation Method 1
The lobes or the control cam acts or act, depending on the rotational speed of the cam disc, counter to the inertia and/or the force of a return spring on a mass which runs by a roller on the cam track or control cam
Implementation Method 2
a mass which runs by a roller on the cam track or control cam. This mass is usually designed as pawl or as a rotatably mounted pendulum with a pendulum nose
Implementation Method 3
This blocking of the cable pulley of the limiter cable in turn has the consequence that a friction force builds up between the cable pulley and the limiter cable and in turn triggers, as a second safety step, the safety brake device
Data Source
AI summary
A speed limiter for an elevator system includes: at least one speed limiter wheel having a first radial cam with lobes, and at least a second, phase-shifted radial cam with lobes; a first mass, which is rotatably arranged in a first pivot bearing and which together with a first roller rolls on the first radial cam such that the first mass follows a first oscillating motion when the speed limiter wheel rotates; and a second mass, which is rotatably arranged in a second pivot bearing and which together with a second roller rolls on the second radial cam such that the second mass follows a second oscillating motion when the speed limiter wheel rotates.