Counterweight Slack Detection Switch for Elevator Safety
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Solution Overview
Problem
Elevator systems with tension members having high coefficients of friction allow unsafe levels of slack to propagate, leading to potential catastrophic slippage, as existing technologies fail to effectively prevent slack propagation in these systems.
Innovation Solution
A counterweight slack detection switch comprising a body, belt guides, a lever arm, a deflectable member, and a switch that engages the tension member to detect and prevent unsafe slack levels by actuating a contact when the tension member transitions from a tension to a slack position, communicating this state to the elevator system's controller to stop operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If tension members with high coefficients of friction are used, then frictional traction is improved, but slack propagation increases to unsafe levels
Solution Approach 1:
The slack detection switch detects slack propagation in the tension member before it reaches unsafe levels that could cause catastrophic slippage. By preliminarily detecting the slack condition and triggering an alarm or shutdown, the system prevents the harmful effect of excessive slack accumulation that occurs with high-friction tension members.
Solution Approach 2:
The slack detection switch provides feedback about the tension member's slack condition to the elevator control system. This feedback mechanism allows the system to monitor and respond to slack propagation in real-time, enabling corrective action before the high-friction tension member's slack becomes dangerous.
2Device complexity
If slack detection is not implemented, then device complexity is reduced, but safety is compromised due to unmonitored slack propagation
Solution Approach 1:
The slack detection switch is designed to automatically detect and signal slack conditions without requiring external monitoring or complex intervention systems. The switch itself performs the detection function through its mechanical engagement with the tension member, providing a simple yet effective safety mechanism that serves the system autonomously.
3Productivity
If the counterweight becomes immovable, then elevator operation continues briefly, but unsafe slack levels propagate before detection
Solution Approach 1:
The slack detection switch preliminarily detects slack propagation caused by an immovable counterweight before it reaches dangerous levels. By detecting the slack condition early in the propagation process, the system can trigger an alarm or shutdown that prevents the counterweight issue from developing into a safety hazard, thereby protecting continued operational 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
Effectively prevents unsafe slack propagation by detecting reduced tension in the tension member and triggering a remedial action, such as stopping the elevator car, thereby ensuring safety and preventing excessive slippage.
Implementation Method 1
a deflectable member biasing the lever arm relative to the body
Implementation Method 2
frictional traction between the tension members and the rotating drive sheaves
Data Source
AI summary
A counterweight slack detection switch including a body, a first belt guide mounted to the body and configured to engage a first side of a tension member, a second belt guide mounted to the body and configured to engage the first side of the tension member, a lever arm having a first end and a second end, the first end pivotally mounted to the body, a deflectable member biasing the lever arm relative to the body, a third belt guide mounted to the second end of the lever arm and configured to bias the tension member from a tension position to a slack position, and a switch mounted to the body and configured to contact the tension member when the tension member is in at least one of the tension position and the slack position.