Automobile Safety Belt Lock Tongue with Self-Locking Slider

The problem

Conventional safety belt lock tongues secure the webbing primarily through friction and mechanical retention at the holding part. During severe collisions, extreme forces can cause the webbing to slip slightly within the tongue before the retractor locks fully. Even minor slippage can increase the distance the occupant moves forward, potentially aggravating injuries to the chest and shoulder area. There is a need for a tongue design that actively engages the webbing more securely as tension increases, without requiring additional complex mechanisms or external power sources.

The solution

The patent describes a lock tongue body fitted with a self-locking slide block. This block slides along the body toward the holding part where the webbing is normally retained. An engagement part is located on the end surface of the slide block opposite the holding part, creating a first gap between them. The slide block includes a stop block around which the safety belt webbing passes and turns back.

As the webbing is drawn tightly—such as during a sudden deceleration—the tension pulls the webbing against the stop block. This force drives the self-locking slide block to slide toward the holding part. The first gap narrows until the engagement part meshes directly with the webbing pressed against the holding part. This interlocking action enhances the locking function, securing the webbing more effectively than friction alone.

Who it is for

• Automotive Tier-1 suppliers seeking advanced restraint components that improve passive safety metrics without increasing system complexity.
• Seat belt manufacturers looking to differentiate their product lines with enhanced anti-slip mechanisms for high-performance or heavy-duty vehicles.
• Commercial vehicle fleets prioritizing occupant safety in trucks and buses where higher masses generate greater inertial forces during braking or impacts.
• Aftermarket safety upgrade providers offering retrofit solutions for older vehicles lacking modern pretensioner technologies.

How it works

The main parts

Operating steps

1. Normal State: The webbing passes through the first gap, bypasses the stop block, and turns back. The slide block rests near its starting position.
2. Tension Applied: When the belt is pulled tight, the webbing exerts force on the stop block.
3. Sliding Action: This force drives the self-locking slide block to move along the lock tongue body toward the holding part.
4. Gap Closure: The first gap decreases as the block advances.
5. Engagement: The engagement part meshes with the webbing against the holding part. Interlocking structures (tooth-like/honeycomb) secure the webbing, preventing further slip.

Applications

Passenger cars

In standard sedans and SUVs, this tongue provides added security during emergency braking or moderate collisions, reducing webbing slip that could compromise airbag effectiveness.

Commercial trucks

Heavy-duty vehicles generate significant momentum. The self-locking feature ensures the driver remains firmly restrained during abrupt stops, protecting the spine and shoulders from excessive forward movement.

School buses

Frequent hard braking requires reliable restraint systems. The passive engagement mechanism activates automatically under load, ensuring consistent protection for passengers without relying on electronic sensors.

Construction equipment

Off-road vehicles experience rough terrain and sudden jolts. The robust interlocking design maintains belt integrity even when subjected to vibration and unexpected shifts in load.

Where it is less suitable

• Low-speed urban shuttles: Vehicles operating exclusively below 20 mph may not generate sufficient tension to trigger the full benefit of the self-locking mechanism compared to standard tongues.
• Legacy retrofit markets: Older vehicle frames may require specific bracket modifications to accommodate the new slide block geometry if original tongues were designed for simple friction fit.