Crane Weathervaning Slip Clutch Torque Control
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Solution Overview
Problem
Tower cranes face instability due to autorotation under unfavorable wind conditions when not in operation, as existing solutions struggle to provide a consistent braking torque that prevents autorotation while allowing wind alignment, and are difficult to adjust for varying wind conditions and crane configurations.
Innovation Solution
A method using an adjustable slip clutch, such as a hysteresis clutch, to provide a constant out-of-operation braking torque that is significantly smaller than the holding torque during operation, ensuring stability by maintaining a uniform braking torque over the entire speed and rotation angle range, eliminating the need for additional brakes and avoiding breakaway torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the slewing gear brake is completely released when the crane is out of operation, then the crane can align itself with the wind direction, but the crane may rotate too quickly under adverse wind conditions and tip over due to autorotation
Solution Approach 1:
The brake torque is adjusted to a specific parameter range when the crane is out of operation. The control device sets the brake torque to be between 10% and 50% of the holding torque required during operation, allowing the crane to resist autorotation while still permitting wind alignment. This parameter adjustment resolves the contradiction by finding the optimal torque level that balances both stability and wind alignment capability.
2Reliability
If an auxiliary brake is installed to prevent autorotation, then crane stability is improved, but the device complexity increases and the brake is difficult to design for varying wind conditions
Solution Approach 1:
The existing slewing gear brake, originally designed for holding the crane during operation, is made multi-functional by enabling it to provide both operation-mode holding torque and out-of-operation braking torque. The control device adjusts the brake torque based on the operational state, allowing the single brake to serve dual purposes: preventing autorotation when parked and maintaining position during operation. This eliminates the need for a separate auxiliary brake system.
Solution Approach 2:
The brake torque is made dynamic rather than fixed. The control device continuously adjusts the brake torque based on the crane's operational state (operation vs. out-of-operation mode). During operation, the brake provides full holding torque; when parked, it provides reduced braking torque (10-50% of holding torque). This dynamic adjustment allows the brake system to adapt to varying wind conditions and operational requirements without adding mechanical complexity.
3Reliability
If a friction brake is used to provide braking torque, then autorotation is prevented, but breakaway torque causes instability during initial rotation from zero speed
Solution Approach 1:
The patent replaces the traditional mechanical friction brake system with an electromagnetic brake system. The electromagnetic brake provides smooth, controlled braking torque without the breakaway torque characteristic of friction brakes. The electromagnetic force can be precisely controlled by adjusting the current, allowing the brake to maintain constant torque during rotation and eliminate the instability caused by static-to-dynamic friction transitions in mechanical brake 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
Prevents autorotation effectively while allowing the crane to align with wind direction, maintaining stability even in changing wind conditions and different crane configurations, with the braking torque being gentle and constant, including at zero speed, without wear or complex adjustments.
Implementation Method 1
an adjustable slip clutch, such as a hysteresis clutch, to provide a constant out-of-operation braking torque
Data Source
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AI summary
A method for weathervaning a crane (1) which has a boom (3) which can rotate about a vertical axis (5), a slewing gear motor (7) and a slewing gear service brake (8) for securing the boom (3) in a rotational position with a securing torque in the crane mode, wherein in the case of a crane which has been decommissioned, the boom is braked against rotation with a decommissioned mode braking torque which is less than the specified securing torque in the crane mode, wherein the decommissioned mode braking torque is applied by a slip clutch (10) in the form of a hysteresis clutch or hysteresis brake which is preferably arranged between the slewing gear brake (8) and the slewing gear drive (7) or between the slewing gear drive (7) and an output gear (11).