Gravity-Actuated Slack Switch for Hoist Wire Safety
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Solution Overview
Problem
Existing hoist mechanisms for vertically movable doors lack a reliable and simple method for emergency halt in case of hoist wire failure, which can lead to uncontrolled door movement and safety risks.
Innovation Solution
A hoist mechanism with a slack switch arranged in connection with the reel, featuring a pivoting element that uses gravity to switch from a first position allowing normal motor function to a second position that halts the motor when tension falls below a threshold, ensuring safe operation without an external power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a slack switch is added to detect hoist wire tension and halt the motor, then safety and operational reliability are improved, but device complexity increases
Solution Approach 1:
The slack switch is designed to automatically detect tension loss and trigger the emergency halt mechanism without requiring external power sources or complex control systems. The gravity-based pivoting element self-activates when the hoist wire goes slack, making the system self-monitoring and self-protecting.
Solution Approach 2:
The patent replaces electronic tension sensors and powered actuators with a purely mechanical gravity-based pivoting element. This mechanical substitution eliminates the need for external power sources and complex electronics while maintaining reliable tension monitoring functionality.
2Device complexity
If a gravity-based pivoting slack switch is used instead of an electronically controlled tension sensor, then device complexity and manufacturing costs are reduced, but measurement precision may be affected
Solution Approach 1:
The slack switch is designed with specific geometric parameters and mass distribution to ensure that the pivoting element only changes position when tension falls below a predetermined threshold. By carefully selecting the pivot point location, arm lengths, and component masses, the system achieves reliable threshold-based detection without requiring complex measurement electronics.
3Ease of manufacture
If the slack switch uses a gravity-based pivoting mechanism without external power, then ease of manufacture and operational simplicity are improved, but the ability to provide precise control signals is reduced
Solution Approach 1:
The patent extracts the essential safety function from complex electronic control systems and implements it through a simple mechanical pivoting element. By taking out only the critical tension detection and halt triggering functions and implementing them mechanically, the system achieves ease of manufacture while providing sufficient control for safety applications.
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 provides a structurally simple and functionally reliable emergency halt mechanism that ensures safe operation of vertically movable doors by immediately stopping the motor when hoist wire tension decreases, enhancing safety and reducing manufacturing costs.
Implementation Method 1
The slack switch is arranged to move from the first position into the second position by rotating around a pivot pin. The rotation of the slack switch occurs by means of gravity, when the potential energy stored in the slack switch is released.
Data Source
Figure 1
Figure 2a~2b
AI summary
The hoist mechanism of the vertically movable door has a reel (32) fitted around an axis (30), which is rotated by means of a motor, on which reel hoist wire (28) is stored. The hoist mechanism further contains a slack switch for halting the motor when the tension of the hoist wire decreases. The slack switch is arranged in connection with the reel, and it has a rod (52), which is fitted to rest itself against the hoist wire unravelling from the reel and to alter its line of travel. The hoist wire holds the slack switch in the first position as long as its tension exceeds a predetermined threshold value, whereby the motor functions normally. When the tension of the hoist wire falls below the threshold value, for example as a result of the hoist wire breaking, the slack switch moves into the second position, which switches off the function of the motor. The slack switch comprises a first and a second support arm (50a, 50b), which are attached at their first end in a pivoted manner (54) to the structures of the vertically movable door. The rod resting itself against the hoist wire is attached at its ends to the ends of the support arms, and the hoist wire is fitted to travel between the support arms over the rod. The slack switch is arranged to move from the first position into the second position by rotating around the pivot pin (54). The rotation of the slack switch occurs by means of gravity, when the potential energy stored in the slack switch is released. The hoist mechanism according to the invention can be used in vertically movable doors of fabric, which fold upwards.