Centrifugal Ball Decelerator for Projection Screen Rolling
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Solution Overview
Problem
Conventional projection screen rolling mechanisms experience rapid rotational speeds, leading to potential damage of the projection screen during the rolling process.
Innovation Solution
A decelerating device comprising a fixed shaft, a tube with internal teeth, a first transmission element with planetary gears, and a driven element with balls that rub against the tube to reduce rotational speed, mitigating damage and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the projection screen is allowed to roll freely using only a torsional spring, then the operation is simple and the screen can be rolled up quickly, but the rotational speed becomes too fast and the projection screen is easily damaged
Solution Approach 1:
A decelerating device is introduced as an intermediary mechanism between the torsional spring and the projection screen. This device includes a driven element with balls that can rub against the tube to provide friction-based deceleration, and a transmission element with planetary gears to control the rolling speed, thereby protecting the projection screen from damage while maintaining operational simplicity
Solution Approach 2:
The decelerating device dynamically adjusts its behavior based on rotational speed. When the tube rotates below a specific speed, the balls remain in cavities and no deceleration occurs. When the rotational speed exceeds the threshold, centrifugal force causes the balls to exit cavities and rub against the tube, automatically providing deceleration to protect the screen
2Reliability
If the rotational speed of the projection screen is reduced to prevent damage, then the projection screen is protected from damage, but the rolling process takes more time and reduces productivity
Solution Approach 1:
The decelerating device changes the friction parameter dynamically based on rotational speed. At normal operating speeds below the threshold, friction is minimal and rolling efficiency is maintained. When speed exceeds the threshold, friction increases automatically to reduce speed and protect the screen, thus maintaining productivity while ensuring protection
3Reliability
If a decelerating mechanism is added to reduce rotational speed, then the projection screen is protected from damage, but the device complexity increases
Solution Approach 1:
The decelerating device is designed to be self-regulating through centrifugal force. The balls automatically move between cavities and contact surfaces based on rotational speed without external control, and the transmission element with planetary gears provides automatic mechanical advantage. This self-service mechanism reduces complexity compared to externally controlled deceleration systems
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 decelerating device effectively reduces the rotational speed of the projection screen, preventing damage and minimizing noise during the rolling process, while also allowing for self-locking functionality for user convenience.
Implementation Method 1
each of the first balls is exposed outside the outer surface of the wheel and rubs against the tube
Implementation Method 2
a torsional spring of the rolling unit connected to the rotation shaft deforms elastically
Implementation Method 3
each of the first balls affected by a centrifugal force is exposed outside the outer surface of the wheel
Data Source
AI summary
A decelerating device includes a fixed shaft, a tube, a transmission element and a driven element is provided. The tube is disposed around the fixed shaft and adapted to rotate about the fixed shaft. The transmission element has a fixed portion fixed at the fixed shaft and a planetary gear revolvably disposed at the fixed portion. The teeth of the tube are geared to the planetary gear. The driven element has a wheel, a sun gear fixed at the wheel and a plurality of balls. The sun gear and the wheel are revolvably disposed at the fixed shaft and in the tube. The planetary gear is adapted to drive the sun gear. The wheel has holes. Each of the holes extends from an outer surface of the wheel facing the tube to the interior of the wheel to form a cavity. The balls are disposed in the holes respectively.