Viscous Rotor Speed Control With Variable Shear Gap
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Solution Overview
Problem
Existing irrigation sprinkler systems face challenges in maintaining a constant rotational speed due to variations in nozzle size or pressure, leading to significant changes in braking torque and rotational speed, and they often require axial movement of the shaft, which can cause water intrusion and seal wear.
Innovation Solution
The system automatically adjusts the gap between the rotor and the housing in response to changes in rotational speed, using an impeller-like feature and a spring mechanism to create axial forces that balance and control the rotor's position, thereby varying the shear gap and braking torque, while preventing axial movement of the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the gap between the rotor and housing is decreased to increase braking torque, then the braking torque increases, but the rotational speed control precision deteriorates due to excessive sensitivity to speed changes
Solution Approach 1:
The patent applies dynamics by making the gap between the rotor and housing variable rather than fixed. The gap automatically adjusts in response to changes in rotational speed, allowing the system to optimize braking torque at different operating conditions. This dynamic adjustment resolves the contradiction by preventing excessive sensitivity while maintaining adequate braking torque across the operating range.
Solution Approach 2:
The patent changes the physical parameter of the gap dimension from a fixed value to a variable parameter that responds to rotational speed changes. By modifying this geometric parameter dynamically, the system achieves both adequate braking torque and acceptable speed control precision, resolving the technical contradiction between these two requirements.
2Force
If the shaft is allowed to move axially to adjust the rotor position, then the braking torque can be adjusted, but water intrusion and seal wear increase
Solution Approach 1:
The patent extracts the axial movement function from the shaft and assigns it to the rotor itself. The rotor is designed to move axially within the housing while the shaft remains stationary, thereby separating the movement requirement from the sealing interface and eliminating water intrusion and seal wear issues.
Solution Approach 2:
The patent introduces an intermediary mechanism (the movable rotor) that allows gap adjustment without requiring shaft movement. The rotor acts as a mediator between the stationary shaft and the housing, enabling braking torque adjustment while maintaining seal integrity at the shaft-housing interface.
3Force
If the shaft moves into the housing to adjust rotor position, then the braking torque increases, but seal friction and wear increase due to pressurization
Solution Approach 1:
The patent extracts the pressurization effect from the shaft movement and relocates it to the fluid circuit system. By using a pump to pressurize the fluid rather than relying on shaft insertion, the system achieves the necessary forces without creating excessive seal friction and wear at the shaft-housing interface.
Solution Approach 2:
The patent replaces the mechanical shaft insertion method with a fluid pressure-based system. Instead of using mechanical movement to adjust rotor position and pressurize the fluid, the system uses a pump to control fluid pressure, thereby eliminating the harmful mechanical friction and wear at the seal interface.
4Device complexity
If a fixed gap design is used, then the device complexity is reduced, but the rotational speed control precision deteriorates under varying pressure and nozzle conditions
Solution Approach 1:
The patent applies dynamics by transforming the fixed gap into a variable gap that automatically adjusts with rotational speed changes. This dynamic characteristic allows the system to maintain precise rotational speed control across varying operating conditions without requiring complex external control mechanisms.
Solution Approach 2:
The patent implements self-service by designing the gap to automatically adjust in response to rotational speed changes without requiring external control systems. The system uses its own operating parameters (rotational speed) to trigger the gap adjustment, thereby achieving precise control while minimizing device complexity.
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 allows for precise control of the sprinkler's rotational speed within a narrow range, minimizing changes in braking torque due to nozzle size or pressure changes, and prevents axial movement-related issues like water intrusion and seal wear.
Implementation Method 1
As the shaft and rotor rotate, the viscous fluid is sheared between the rotor and the housing. As the shear rate increases, the braking torque that retards the shaft rotation also increases.
Implementation Method 2
The rotor is designed with an impeller-like feature to create an axial force when it is rotated in the viscous fluid. The magnitude of the axial force is optionally proportional to the rotational speed of the rotor.
Implementation Method 3
A spring mechanism is optionally located within the housing in such a way as to resist the axial force of the rotor. The axial force of the rotor optionally compresses the spring mechanism until the spring force matches the axial force being generated by the rotation of the shaft and rotor.
Data Source
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AI summary
A rotational speed control device (10) includes a housing (16) containing a viscous fluid and a shaft (14) disposed in the housing (16) and rotatable relative to the housing (16). A rotor (12) may be movable axially on the shaft (14) depending on the rotating speed of the shaft (14). The rotor (12) is biased in a low torque direction. A braking torque between the rotor (12) and the housing (16) and/or between the rotor (12) and a drive control ring (1102) is varied according to an axial position of the rotor (12) on the shaft (14). The device (10) may incorporate bypass channels (1116) to control a circulating pressure of the viscous fluid.