Anti-Torque Rotor Interface for Bearing Failure Control Continuity
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Solution Overview
Problem
The existing anti-torque rotor systems in helicopters are prone to uncontrollable failures due to damage in the antifriction bearing, which can lead to hazardous situations, and there is a need for a simpler and cost-effective solution to detect failures and maintain control even in failure conditions.
Innovation Solution
The anti-torque rotor design incorporates a bearing with a double ring of balls and a transmission unit that includes a sensor system to detect failures and an interface with antifriction coatings to prevent twisting moments from causing undesired rotation, allowing for continued control by activating a redundant transmission path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single antifriction bearing is used to transmit axial load from the control rod to the control element, then the device complexity is reduced, but the reliability deteriorates because bearing failure causes complete loss of control
Solution Approach 1:
The patent divides the single bearing into two separate bearings arranged in series. The first bearing transmits axial load from the control rod to the control element, while the second bearing transmits axial load from the control element to the mast. This segmentation allows the system to maintain control functionality even if one bearing fails, as the other bearing can still transmit the axial load necessary for control operation.
Solution Approach 2:
The patent implements a locking device that activates beforehand when bearing failure is detected. The locking device includes a locking element that can engage with a locking surface to prevent relative rotation between components. When a bearing fails and allows unintended rotation, the locking device detects this rotation and engages the locking element to lock the control element, preventing further damage and maintaining control stability.
2Ease of operation
If the antifriction bearing allows free rotation between control element and control rod, then the ease of operation is improved, but the reliability deteriorates when rolling bodies are damaged causing unintended twisting moment transmission
Solution Approach 1:
The patent introduces a locking device as an intermediary between the control element and the control rod. This locking device includes a locking element that can engage with a locking surface to prevent relative rotation. During normal operation, the locking device remains disengaged, allowing free rotation for ease of operation. When bearing failure causes unintended rotation, the locking device engages to prevent further rotation and protect against twisting moment damage.
Solution Approach 2:
The locking device is designed to counteract the harmful effect of unintended rotation before it can cause damage. The locking element is positioned to engage with the locking surface when rotation exceeds a certain threshold, providing preliminary protection against twisting moment transmission to the control rod and preventing catastrophic failure.
3Volume of moving object
If rolling bodies are made small to reduce bearing size, then the volume is reduced, but the reliability deteriorates due to increased susceptibility to damage from foreign bodies and lubrication loss
Solution Approach 1:
The patent uses two separate bearings instead of one large bearing, which allows each bearing to have smaller, more numerous rolling bodies. This segmentation distributes the load across multiple smaller rolling bodies, reducing the impact of individual rolling body damage while maintaining a compact overall bearing size. The smaller rolling bodies are less susceptible to damage from foreign bodies and lubrication loss.
4Ease of manufacture
If no locking device is used to prevent relative rotation, then the ease of manufacture is improved, but the reliability deteriorates when bearing failure causes progressive twisting moment damage to the control rod
Solution Approach 1:
The locking device serves as an intermediary protection mechanism between the bearing and the control rod. It includes a locking element that can engage with a locking surface on the control element. During normal operation, the locking device remains inactive and does not interfere with bearing function. When bearing failure occurs and causes unintended rotation, the locking device engages to prevent further rotation, protecting the control rod from progressive twisting moment damage while adding minimal manufacturing 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 design effectively reduces the risk of rotor uncontrollability by preventing damage from twisting moments and ensuring controllability even in bearing failure conditions, without adding complexity or cost, by using sensors and antifriction coatings to manage failure states and maintain control.
Implementation Method 1
a plurality of rolling bodies, which roll in respective raceways defined by the radially inner and outer rings
Implementation Method 2
an interface with antifriction coatings to prevent twisting moments from causing undesired rotation
Data Source
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AI summary
An anti-torque rotor (4) is described for a helicopter (1), comprising: a mast (6) rotatable about a first axis (A); a plurality of blades (8) hinged on the mast (6), extending along respective second axes (B) transversal to said first axis (A) and rotatable about respective said second axes (B) to alter the respective angles of attack; a control element (16) sliding and rotating with respect to the mast (6), and operatively connected to said blades (8) to cause the rotation of said blades (8) about respective second axes (B) following a translation of said element (16) along the first axis (A); a control rod (10) sliding axially along first axis (A) with respect to the mast (6) and angularly fixed with respect to the first axis (A); and a connection element (17) interposed between the control rod (10) and the control element (16), sliding along the first axis (A) with respect to the mast (6) and integrally with the control rod (10); the anti-torque rotor (4) further comprises an interface (18, 93) made of an antifriction material interposed between said control rod (10) and said connection element (17). (Figure 4)