Dual-Cylinder Crank Locking for Intuitive Bolt Position Feedback

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Solution Overview

Problem

Existing locking devices with dual locking cylinders are unintuitive and prone to user error, as the direction of key rotation for locking or unlocking is counterintuitive and the state of the lock bolt is not clearly indicated, leading to potential unintentional unlocking or failure to lock.

Innovation Solution

A locking device with independent outer and inner locking cylinders and a two-part crank mechanism, where the crank elements rotate independently and are fixed to drive plates, ensuring a clear rotational direction for locking and unlocking, with a latching connection to secure the lock bolt in desired positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a one-piece crank handle with hourglass-shaped recess is used to engage both drive plates, then the locking mechanism can be compact and integrated, but the key rotation direction becomes counterintuitive and the user cannot deduce the lock bolt position from key movement alone

Engineering Contradiction:
Improvecrank mechanism integrationVSAvoidintuitive operation and position indication
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The crank handle is divided into two separate crank elements (first and second crank elements) that can rotate independently relative to each other. Each crank element is associated with a separate drive plate, allowing each to be operated independently by its own key. This segmentation resolves the contradiction by enabling intuitive operation for each drive plate while maintaining compact integration through their shared connection to the lock bolt.

Inventive Principle:
Principle #1Segmentation

2Device complexity

If the locking bolt is positioned below the crank handle, then the structure is simplified, but the key rotation direction becomes counterintuitive to users accustomed to other locking devices

Engineering Contradiction:
Improvestructural simplicityVSAvoidintuitive rotation direction
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

By separating the crank handle into two independently rotatable crank elements, each can be positioned and oriented to provide intuitive rotation directions. The first crank element responds to the outer drive plate and the second to the inner drive plate, allowing each key operation to follow natural rotational expectations while maintaining the simplified structural arrangement of having the lock bolt below the crank elements.

Inventive Principle:
Principle #1Segmentation

3Device complexity

If a single crank handle engages both drive plates, then the device requires fewer components, but the user cannot determine whether the lock bolt is already in the desired position after key insertion

Engineering Contradiction:
Improvenumber of componentsVSAvoidlock bolt position indication
Core Design Contradiction:
Device complexityVSLoss of information

Solution Approach 1:

The independent rotation capability of the two crank elements provides tactile and visual feedback to the user. When a key is inserted and rotated, the user can feel and observe whether the corresponding crank element rotates freely (indicating the lock bolt needs to be moved) or is already blocked (indicating the lock bolt is in the desired position). This segmented approach maintains component efficiency while restoring position indication information.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The independent crank elements provide immediate mechanical feedback to the user during key rotation. The resistance encountered during rotation, the final stopping position, and the engagement state of each crank element with its drive plate all provide feedback about the lock bolt's current position and the success of the locking operation, eliminating the information loss present in single-crank designs.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP4571018B1Locking device with a crank driven by plate lock cylinders
Publication Date: 2026.04.22 ROTO FRANK FENSTER & TURTECHNOLOGIE GMBH
  • EP4571018B1 patent drawingFigure 1
  • EP4571018B1 patent drawingFigure 2
  • EP4571018B1 patent drawingFigure 3

AI summary

In summary, the invention relates to a locking device (10) for displacing a lock bolt (30), which has an outer locking cylinder (14), in particular an outer Scandinavian oval locking cylinder (14), and an inner locking cylinder (16), in particular an inner Scandinavian oval locking cylinder (16). Furthermore, the locking device (10) has a lock case (12), the lock bolt (30), and an at least two-part crank (60). The crank (60) has a first and a second crank element (32, 34), which can be used independently of one another to displace the lock bolt (30) from a release position to a blocking position and vice versa. The first crank element (32) is arranged in a rotationally fixed manner on a first driver plate (52) of the outer locking cylinder (14), while the second crank element (34) is arranged in a rotationally fixed manner on a second driver plate (54) of the inner locking cylinder (16).To move the lock bolt (30), a key (18) must be inserted into a key receptacle (20) of the respective locking cylinder (14, 16). Furthermore, the invention relates to a method for carrying out a locking operation, in particular of the aforementioned locking device (10).