Back Lock Folding Knife with Safety Locking Function

The problem

In traditional back-lock folding knives, the blade is held open by a spring-loaded arm that engages with a notch in the blade tang. While effective for general use, this mechanism has inherent risks. If the lock face wears down, if debris interferes with the engagement, or if the user inadvertently presses the thumb stud or release tab while gripping the spine, the blade can suddenly close. For tasks requiring sustained pressure or precision cutting, unexpected closure poses a significant safety hazard to the user’s fingers. Additionally, many external safety accessories are bulky, easily lost, or require separate storage, making them impractical for everyday carry.

The solution

This patent describes a folding knife where the standard back-lock mechanism is augmented with a removable safety pin. The pin serves two functions: it acts as a physical barrier to stop the back spring from moving, thereby locking the blade open, and it features an integrated storage system within the handle so it is always available when needed.

1. Handle Assembly: Composed of two opposing flat handle parts connected to form a cavity.
2. Blade and Spring: A rotatable blade sits between the handles, paired with a back spring that includes a locking hook.
3. Aligned Holes: Pin holes are spaced through the back spring’s hook and the handle parts. A separate lock-pin placement hole is also provided in the handle.
4. Internal Spring Wire: A spring wire is mounted inside the handle. It extends into both the pin holes and the storage hole.
5. Clamping Mechanism: The safety pin has a clamping groove. The internal spring wire forms clamping portions that grip this groove, holding the pin firmly in place whether it is engaged in the lock position or stored in the handle.

Who it is for

• Outdoor and Survival Brands: Companies looking to differentiate their fixed-blade alternatives with a folding knife that offers secure lock-up.
• Professional Tool Manufacturers: Makers of utility knives for construction or carpentry where accidental closure could cause injury during heavy-duty tasks.
• High-End EDC (Everyday Carry) Brands: Niche manufacturers targeting users who prioritize maximum safety features over minimal weight.
• Military and Law Enforcement Suppliers: Agencies requiring fail-safe mechanisms for tactical folding knives used in critical situations.

How it works

The main parts

Operating Steps

1. Open the Blade: Rotate the knife body out of the handle. The back spring’s hook engages the blade’s locking groove.
2. Engage Safety Lock: Insert the lock pin through the aligned pin holes in the handle and the back spring’s hook. The internal spring wire clamps the pin’s groove, holding it in place.
3. Locked State: With the pin inserted, the back spring cannot move. The blade is mechanically prevented from closing, regardless of pressure on the release tab.
4. Release Safety: Pull the lock pin out. The spring wire releases its grip.
5. Store the Pin: Insert the pin into the lock-pin placement hole in the handle. The spring wire clamps it here, keeping it attached to the knife.
6. Close the Blade: Press the back spring’s release tab to disengage the hook from the blade and fold the knife closed.

Applications

Heavy-Duty Cutting Tasks

When using a folding knife for batoning wood or prying materials, lateral forces can stress the lock. The safety pin ensures the blade remains rigidly open, protecting the user from sudden collapse.

Precision Work

For carving, whittling, or detailed craft work, consistent blade stability is crucial. The pin eliminates micro-movements or potential slip-offs caused by wear on the standard back-lock surfaces.

Child-Safe Handling

Parents or educators teaching knife skills can insert the pin to create a “training mode” where the blade cannot accidentally close, reducing pinch hazards while learning proper grip and angle.

Maintenance and Cleaning

During deep cleaning or lubrication of the pivot and lock area, the pin can be removed and stored directly in the handle, ensuring the small part is not misplaced among tools or rags.

Where it is less suitable

• Ultra-Minimalist EDC: Users seeking the lightest possible pocket knife may find the added metal pin and internal spring wire slightly heavier than standard designs.
• One-Handed Operation: Deploying and stowing the safety pin requires two hands, making it unsuitable for scenarios demanding immediate one-handed deployment.
• High-Vibration Environments: While the pin is clamped, extreme vibration might theoretically loosen the fit over time without additional thread-locking or retention features not specified in the patent.