Delayed Seat Belt Reel Locking to Reduce Spinal Loads
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Solution Overview
Problem
Conventional passenger restraints, such as shoulder harness systems with pretensioners, often increase spinal loads and require significant structural reinforcement of seats, which is undesirable due to added weight, complexity, and cost, especially in aircraft applications like front row seats without forward structures to limit movement.
Innovation Solution
A seat belt system with a reel lock and sensor configuration that delays the initiation of restraint until the passenger's center of gravity has lowered through a predetermined amount of forward travel, reducing spinal tension without complex mechanisms or excessive structural reinforcement by allowing a controlled amount of forward movement before locking the seat belt reel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shoulder harness systems with pretensioners are used to limit forward movement, then passenger safety is improved, but spinal loads increase and structural reinforcement is required
Solution Approach 1:
The seat belt system allows preliminary forward movement of the passenger before engagement, enabling the passenger's center of gravity to lower naturally. This preliminary action reduces spinal tension before the restraint system engages, eliminating the need for pretensioners while maintaining safety
Solution Approach 2:
The system provides beforehand cushioning by allowing controlled forward travel that lowers the passenger's center of gravity before restraint engagement. This natural movement acts as a cushioning mechanism that reduces the impact forces on the spine when the seat belt eventually engages
2Reliability
If pretensioners are added to reduce spinal loads, then restraint effectiveness is improved, but device complexity increases
Solution Approach 1:
The invention extracts and removes the pretensioner mechanism from the seat belt system. By allowing natural forward movement to occur first, the system achieves effective restraint without the complex pretensioning mechanism, thereby reducing device complexity while maintaining or improving restraint effectiveness
Solution Approach 2:
The system utilizes the passenger's own forward momentum and body movement to achieve the desired restraint effect. The passenger's natural forward travel lowers their center of gravity, and the seat belt engages automatically based on this movement, eliminating the need for active pretensioning mechanisms
3Strength
If structural reinforcement is added to seats to support restraint loads, then seat strength is improved, but weight and cost increase
Solution Approach 1:
By allowing preliminary forward movement that lowers the passenger's center of gravity before restraint engagement, the system reduces the peak loads transmitted to the seat structure. This eliminates the need for heavy structural reinforcement while maintaining adequate seat strength
Solution Approach 2:
The system changes the temporal parameter of restraint engagement by delaying it until after the passenger's center of gravity has lowered. This parameter change reduces the force magnitude transmitted to the seat, allowing use of lighter seat structures
Data Source
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AI summary
For a vehicle seat, for instance an aircraft passenger seat, a seat belt system including a seat belt reel (106) having a rotating shaft (108), a seat belt (110) wound on the rotating shaft, and a lock (112) for locking at least one of the rotating shaft and the seat belt. At least one sensor (114) is operative to output a signal when a sensed parameter exceeds a predetermined magnitude threshold. An activation device (116) is operative to activate the lock. A time delay device (118) electrically coupled to the at least one sensor and the activation device is operative to, upon receiving the signal output by the at least one sensor, activate the activation device upon completion of a time delay after receiving the signal output by the at least one sensor. Further embodiments include shoulder belts forming loops (206) allowing a predetermined amount of forward travel prior to restraining a passenger.