Elevator Safety Circuit Delayed Brake Application
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Elevators with synthetic traction means experience severe deceleration during emergency stops due to increased friction, leading to reduced passenger comfort and potential injury, as existing safety circuits apply brakes immediately, causing abrupt deceleration.
Innovation Solution
An elevator safety circuit with a series chain of safety contacts, a delay circuit comprising a diode, resistor, and capacitor, and a watchdog timer, which introduces a delay in applying the brake during emergency stops, allowing for a controlled deceleration in two phases: immediate motor control followed by delayed brake application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immediate brake application is used in emergency stop, then safety response time is improved, but passenger comfort deteriorates due to severe deceleration
Solution Approach 1:
The emergency stop process is segmented into two distinct phases: Phase 1 involves immediate motor control to initiate deceleration, while Phase 2 involves delayed brake application to complete the stop. This segmentation allows the system to achieve both rapid response and controlled deceleration, resolving the contradiction between safety response time and passenger comfort.
Solution Approach 2:
The system performs preliminary action by immediately controlling the motor to begin deceleration before applying the brake. The delay circuit ensures that the brake is applied only after the motor has already started reducing speed, allowing the deceleration to be more gradual and comfortable while still maintaining rapid overall response.
2Length of moving object
If brake is applied immediately during emergency stop, then stopping distance is reduced, but deceleration force increases causing potential injury
Solution Approach 1:
The stopping process is divided into two phases with different force characteristics. Phase 1 uses motor control to provide moderate deceleration force, while Phase 2 applies brakes to complete the stop. This segmentation maintains a reasonable stopping distance while avoiding excessive deceleration forces that could cause injury.
Solution Approach 2:
The system changes the deceleration parameter over time by first using motor control to reduce speed gradually, then applying brakes to complete the stop. This dynamic parameter change ensures that the deceleration force remains within safe limits throughout the stopping process while achieving an acceptable stopping distance.
3Ease of operation
If delay circuit is added to safety circuit, then deceleration control is improved, but circuit complexity increases
Solution Approach 1:
A delay circuit is introduced as an intermediary element between the safety contacts and the brake control. This intermediary component provides the necessary time delay to enable controlled deceleration without requiring complex control logic or multiple additional components, thus improving deceleration control while minimizing the increase in circuit complexity.
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 safety circuit ensures a more controlled emergency stop, improving passenger comfort by decelerating the elevator car in a gradual manner, reducing the risk of injury and enhancing safety.
Implementation Method 1
The delay circuit may comprise a diode and a resistor arranged between the output of the series chain of safety contacts and the first safety relay and can further comprise a capacitor in parallel across the resistor and the first safety relay. Accordingly, the amount of delay can be set by selecting an appropriate R-C constant for the delay circuit.
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
An alternative elevator safety circuit which can be used in a method to decelerate an elevator car during an emergency stop in a more controlled manner. The safety circuit comprises a series chain of safety contacts (S1-Sn) having an input (T1) connected to a power source (PS) and a first safety relay (7) deriving electrical power from an output (T2) of the series chain of safety contacts (S1-Sn). A delay circuit (13) is arranged between the output (T2) of the series chain of safety contacts (S1-Sn) and the first safety relay (7). Hence, if any of the safety contacts open to initiate an emergency stop, any process controlled by the operation of the first safety relay is delayed.