Dual-Interlock Safety Belt Buckle for Fall Protection

The problem

Workers at height often use double lanyards to move between anchor points. With standard buckles, disconnecting one belt before securing the other creates a brief period where the worker is unprotected. If the sequence is reversed or if a buckle fails to engage properly due to gloves or fatigue, there is a risk of falling. Existing single-point buckles do not mechanically ensure that one connection remains secure while the other is being manipulated. There is a need for a locking mechanism that manages the engagement and disengagement states of two belts simultaneously to ensure that at least one point of attachment is always active or transitioning safely.

The solution

The patent describes a seat belt buckle comprising a housing, an interlocking assembly, and two tensioning assemblies.

1. The housing contains a mounting hole with two through holes spaced along the X-axis.
2. The interlocking assembly features two locking elements positioned vertically (Z-axis) within the housing. Each element protrudes through one of the through holes.
3. These elements have distinct locked and unlocked positions. A key feature is the mechanical linkage: when one locking element moves toward its locked position, it physically drives the other locking element to reset to its unlocked position.
4. Two tensioning members are located below the locking elements. They are also spring-loaded or repositionable.
5. The hook of a safety belt fits around the outer periphery of one locking element and one tensioning member.
6. When a locking element is in the locked position, its lower end inserts into the corresponding tensioning member. The tensioning member expands or shifts to compress the inner ring of the belt hook, securing it.
7. When the locking element is in the unlocked position, the tensioning member releases its grip on the hook, allowing removal.

Who it is for

• Electrical utility companies: Specifically mentioned in the context of overhead line operations where workers switch between anchors frequently.
• Construction safety equipment brands: Looking for differentiated fall protection hardware that reduces user error during lanyard transitions.
• Industrial maintenance contractors: Teams working on scaffolding or rooftops who require reliable double-lanyard systems.
• Arborists and tower climbers: Professionals who need to maintain constant attachment while moving up or down structures.

How it works

The main parts

The mechanism relies on a specific arrangement of plates and steps to create the interlock.

Operating steps

1. Insert Hook: The user places the safety belt hook over one locking element and its corresponding tensioning member.
2. Press to Lock: The user pushes the locking element down. As it moves, its unlocking rod contacts the opposing locking plate.
3. Interlock Action: This contact forces the opposing plate to rotate away, releasing the other locking element from its clamped state. Simultaneously, the current locking element’s locking step engages with its own plate, holding it in the locked position.
4. Secure Grip: The descent of the locking element pushes the tensioning member outward or downward, causing it to compress the inner ring of the hook, preventing accidental withdrawal.
5. Switch Anchors: To attach the second belt, the user presses the now-unlocked second locking element. This action will mechanically drive the first locking element back to its unlocked position, releasing the first tensioner.

Applications

Overhead Line Maintenance

Electricians working on power lines often need to shift their primary and secondary lanyards. This buckle allows them to clip onto a new anchor point, which automatically frees the old one, reducing the time spent unhooking manually and minimizing the window of exposure.

Tower Climbing

Climbers using double lanyards for continuous protection benefit from the automatic transition. When reaching a new platform or anchor, pressing the second latch secures the climber while releasing the first, streamlining the ascent or descent process.

Construction Scaffolding

On multi-level scaffolds, workers move between sections frequently. The dual-interlock prevents situations where both belts are inadvertently released, as the mechanical design requires one to be engaged to affect the other’s state.

Industrial Roof Work

Roofers installing panels or performing repairs must stay tied off. The robust housing and mechanical tensioning ensure that gloves do not interfere with the basic push-to-lock action, providing a tactile confirmation of security.

Where it is less suitable

• Single-lanyard applications: The dual-interlock complexity offers no benefit if only one belt is ever used.
• High-speed automated assembly: The manual push-and-release cycle is slower than simple snap-in buckles.
• Extreme corrosion environments: While materials aren’t specified, the tight tolerances of the interlocking plates may require more frequent cleaning than simpler open hooks.