Curtain Rigging Limit Switch With Chain-Insert Stop Hold
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Solution Overview
Problem
Existing stage curtain rigging systems lack an effective mechanism to reliably stop heavy curtains at predetermined positions without risking motor damage or curtain movement resumption, which can cause further damage.
Innovation Solution
A rolling sprocket with offset pivot and spring tension engages chain links, activating a kill switch to stop the motor when the curtain reaches the desired position, using inserts to prevent sprocket engagement in chain interstitial spaces, ensuring the switch remains activated until the curtain stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional limit switch is used to stop the curtain, then the motor can be deactivated at a predetermined position, but the heavy curtain may resume movement due to momentum, causing further damage
Solution Approach 1:
The kill switch is activated in advance by the rolling sprocket contacting the chain insert before the curtain completes its movement. This preliminary action ensures the motor is deactivated while the curtain is still in motion, allowing the curtain to coast to a complete stop under friction and gravity, preventing any resumption of movement that could cause damage.
Solution Approach 2:
The rolling sprocket acts as an intermediary mechanism between the chain and the kill switch. It translates the linear movement of the chain into rotational motion that engages the kill switch, providing a reliable mechanical connection that ensures the switch is activated at the precise moment needed to stop the curtain.
2Reliability
If the kill switch is activated immediately when the sprocket contacts the insert, then the motor stops, but the heavy curtain may continue moving and the switch may deactivate, allowing movement to resume
Solution Approach 1:
The kill switch mechanism is designed to remain activated dynamically throughout the curtain's deceleration phase. The switch is engaged by the rolling sprocket and remains in the activated state until the curtain comes to a complete stop, at which point the chain tension releases and allows the switch to reset. This dynamic behavior ensures the motor remains deactivated throughout the entire stopping process without requiring complex timing circuits.
3Ease of operation
If the sprocket engages the chain normally, then the chain moves freely, but the sprocket may not reliably activate the kill switch at the precise terminal position
Solution Approach 1:
The chain insert serves as an intermediary element that transforms the normal chain movement into a precise trigger signal for the kill switch. The insert protrudes from the chain at a specific location, ensuring that when the rolling sprocket contacts it, the switch is activated at the exact terminal position. This maintains free chain movement while achieving precise positioning control.
Solution Approach 2:
The chain insert is placed at a specific location on the chain to create a localized trigger point. This local modification allows the sprocket to engage the chain normally for most of its travel while providing a precise activation point for the kill switch when the insert contacts the sprocket at the terminal position.
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 stops heavy stage curtains at precise positions, preventing motor and curtain damage by ensuring the kill switch remains activated until the curtain comes to a complete stop, even with the weight and momentum of the curtains.
Implementation Method 1
Spring tension on the swingarm maintains contact between the rolling sprocket and the chain
Data Source
AI summary
The limit switch uses a rolling sprocket mounted on an offset pivot point mounted in a housing in combination with inserts into individual links of the chain. The sprocket engages the chain using spring tension on the pivot point and rolls along the chain as the chain moves with the teeth of the sprocket inserting into the chain link spaces. An insert is attached in a chain link and positioned such that when the curtain reaches the desired terminal position, the inserts are at the point where the sprocket contact the insert. The insert blocks the cog of the sprocket which pushes the sprocket away from the chain and inwardly into the interior of the housing. Inside the housing the limit switch that is activated—either by contact or other means. The activation of the kill switch stops the motor and thus the movement of the curtains.