Counterbalancing Spring Friction Reduction via Stretched Mandrel
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Solution Overview
Problem
Motorized roller shades face high torque and power requirements, especially when rolling up, due to the inefficiencies in conventional torsion springs, which also introduce frictional forces that hinder counterbalancing efficiency.
Innovation Solution
A roller shade system with a pretensioned torsion spring is designed, where the counterbalancing spring is attached to a shade drive unit with an output mandrel that maintains the spring in a stretched state, preventing coil contact and reducing friction, and the spring is pretensioned using a motor to optimize torque assistance throughout the rolling cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional torsion spring is used to counterbalance the roller shade, then the spring builds up torque as it is wound up, but the torque progressively reduces in a linear fashion as the spring winds down, resulting in high torque and power requirements during the rolling up cycle
Solution Approach 1:
The spring is pretensioned before operation begins, storing potential energy in advance. This preliminary action ensures the spring is already under tension when the shade starts rolling up, providing consistent torque assistance throughout the entire rolling cycle rather than requiring high power at the end of the cycle.
Solution Approach 2:
The patent changes the tension parameter of the spring by maintaining it in a permanently stretched state through the output mandrel. This parameter change transforms the spring from a conventional torsion spring with variable torque to one that provides consistent torque assistance, fundamentally altering the torque profile during operation.
2Volume of moving object
If the counterbalancing spring is allowed to coil tightly during operation, then space is saved, but friction between coils increases significantly, reducing counterbalancing efficiency
Solution Approach 1:
The output mandrel serves as an intermediary element between the spring and the drive mechanism. It maintains the spring in a stretched state with coils separated, preventing direct coil-to-coil contact and friction while still allowing the spring to provide counterbalancing force. The mandrel acts as a spacer that eliminates frictional losses.
Solution Approach 2:
The spring is functionally segmented into active coils that provide torque and inactive coils that are separated by the output mandrel. This segmentation allows the active portion to perform its counterbalancing function while the separated coils minimize friction, effectively dividing the spring's function between torque generation and friction reduction.
3Ease of manufacture
If a torsion spring is used without pretensioning, then installation is simpler, but the spring does not provide consistent torque assistance throughout the rolling cycle, requiring higher motor power
Solution Approach 1:
The system performs its own pretensioning through the motorized mechanism. The motor rotates the output mandrel to stretch the spring to the desired tension level, and then the system maintains this tension automatically during operation. This self-service approach eliminates the need for manual pretensioning while ensuring optimal torque assistance.
Solution Approach 2:
The system transitions from a static spring configuration to a dynamic one where the output mandrel can adjust the spring tension. The mandrel's position along the spring's length can be changed to maintain optimal tension throughout the rolling cycle, adapting the spring's performance to the varying load conditions.
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
This solution significantly reduces the torque and power required to roll up and down the shade, maintaining consistent assistance throughout the cycle, minimizing friction and extending battery life in battery-operated systems.
Implementation Method 1
a counterbalancing spring connected to and longitudinally extending between the stationary spring carrier and the rotating spring carrier... As the roller shade is unraveled, tension builds up in the spring. The tension is released when the roller shade is rolled up, thereby assisting the motor in lifting the shade material.
Implementation Method 2
One approach uses a conventional torsion spring comprising a plurality of coils. As a torsion spring is wound up, it builds up torque.
Implementation Method 3
a friction-reducing member extending within the spring between the stationary spring carrier and the rotating spring carrier... maintaining the spring in a stretched state such that the plurality of coils at the active portion of the spring do not contact each other, thereby reducing friction in the spring
Data Source
AI summary
A roller shade comprising a shade drive unit having a counterbalancing spring connected to and extending between a stationary spring carrier and a rotating spring carrier over an output mandrel, wherein the output mandrel comprises a length that maintains the spring in a stretched state such that the plurality of coils at the active portion of the spring do not contact each other when the shade material is at the rolled down position to reduce friction in the counterbalancing spring.