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Methodology for Crash Locking Tongue (CLT) Component Testing Disclosure Number: IPCOM000241582D
Publication Date: 2015-May-13
Document File: 4 page(s) / 4M

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The Prior Art Database

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Methodology for Crash Locking Tongue (CLT) Component Testing

Crash Locking Tongues (CLTs) have been recently implemented in vehicle restraint systems to redirect some of the chest loads a passenger experiences in a frontal crash to the lap or H-point. Traditionally, the CLT performance is validated through system level sled testing; however the CTL is not easily visible in this set up and its activation can be difficult to distinguish in sled data due to the numerous test factors that could affect its performance. Therefore, to understand the component’s performance and activation characteristics in more detail, a component level test methodology has been developed. This provides insight into the loads required for CLT activation, the time at which the restraint is most effective, and the CLT’s overall performance.


The purpose of a CLT is to cinch the seatbelt and prevent slippage of the seatbelt webbing from the lap to the shoulder portion of the belt during high load scenarios. The cam in the CLT, which rotates from its home position to cinch the webbing, is activated when a minimum differential load between the shoulder and lap loads is reached. The differential load is characterized through this test, as it will not only affect occupant loads, but it will also determine the time the occupant experiences maximum Nij, Fx, Fy, Fz, Mx, My, and Mz, values that are tracked by NHTSA for regulatory safety testing.


The only two production level parts that are required to complete this test are production webbing and CLTs. To aid in determining if any translation or slippage of the webbing through the CLT occurs during the test, the belt should be marked along its length. Removal of the CLT cover is also important so that the rotational movement of the cam can be clearly seen in the films. Once this has been completed, the CLT should be clamped into a fixture at 45*. It should be oriented such that the part of the belt that will be impacted is the lap belt. Then the webbing should be threaded through the CLT and fixed at both ends as seen in Figure 1. The rear clamp for the shoulder load can be adjusted along the lateral fixture to increase or decrease the angle between the lap belt and shoulder belt. If the initial vehicle specific angle is unknown, set the angle between the shoulder and lap belt to 45*.The impactor weight is 200lbs and the initial speed is 3.5mph to simulate a shoulder load between 3-4kN and a lap load from 6-7kN as seen in most barrier tests. The impactor plate center should line up with the center of the lap belt portion of the webbing.  

Figure 1: Set Up Diagram


Figure 2: Close up of CLT in initial position


Figure 3: Test set up


        Figure 2: Close up of CLT in initial position                     

Post- Processing Methodology

The CLT should lock and prevent belt slippage by 20ms to protect the occupant in a vehicle crash. The higher the threshold differential, the lat...