Exit Device Assembly With Cam-Driven Vertical Rods

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Solution Overview

Problem

Existing exit devices require significant input force to actuate latches, necessitating precise rod lengths and complex mechanisms, which can be cumbersome and inefficient.

Innovation Solution

An exit device assembly featuring an intermediate transmission assembly that translates input into rotational movements of vertical rods, reducing the required input force and allowing for more compact design through a chassis-guided rotation of upper and lower latches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional linear transmission mechanisms are used to actuate latches, then the latch can be secured reliably, but significant input force is required and the mechanism becomes complex

Engineering Contradiction:

Improvelatch securityVSAvoidinput force required

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent changes the motion parameter from linear translation to rotation. The intermediate transmission assembly converts the linear motion of the rod into rotational motion of the vertical rod, which then actuates the latch. This parameter change reduces the input force required while maintaining reliable latch engagement through the rotational cam mechanism.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The intermediate transmission assembly serves as an intermediary mechanism between the input rod and the latch. It includes a rod, vertical rod, and cam mechanism that mediates the force transmission, converting linear motion to rotational motion and reducing the direct force requirement on the latch actuation system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If precise rod lengths are specified to achieve proper latch actuation, then the latch can be actuated accurately, but the device becomes complex and difficult to manufacture

Engineering Contradiction:

Improverod length precisionVSAvoidmechanism complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent introduces dynamic elements including a rotatable vertical rod and cam mechanism that can accommodate variations in rod length. The cam profile is designed to work with the rotational motion, allowing the system to function effectively across a range of rod lengths without requiring extremely precise manufacturing tolerances.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The transmission mechanism is segmented into distinct components (rod, vertical rod, cam, latch) that can be independently manufactured and assembled. This segmentation allows for easier manufacturing and adjustment, reducing the need for highly precise single-piece components.

Inventive Principle:

Principle #1Segmentation

3Force

If complex transmission mechanisms are used to reduce input force, then the force required is reduced, but the device becomes more complex

Engineering Contradiction:

Improveinput force requiredVSAvoidmechanism complexity

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent merges the transmission and actuation functions into a compact intermediate transmission assembly. The rod, vertical rod, and cam are integrated into a single assembly that performs both force reduction and rotational actuation, reducing overall device complexity compared to separate mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces a complex multi-stage mechanical transmission system with a simpler cam-based rotational mechanism. The cam profile inherently provides the force multiplication and motion conversion, eliminating the need for multiple gears, linkages, or other complex mechanical elements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution reduces the force needed to actuate latches, enabling a more efficient and compact exit device operation with reduced mechanical complexity.

Implementation Method 1

an intermediate transmission assembly, the intermediate transmission assembly including an input that translates in response to the push bar receiving the push to move the push bar toward the door. Further, the intermediate transmission assembly includes a rotatable output undergoing a rotation about a rotational axis in response to the translation of the input

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS12442223B1Exit device assembly

Publication Date: 2025.10.14 DORMAKABA USA INC

AI summary

An exit device including an intermediate transmission assembly transmitting the translation of an input into a rotational vertical rod output is disclosed. An upper door latch receiving a rotational vertical rod input to actuate an upper door latch from a latched position to an unlatched position is further disclosed. A lower latch receiving a rotational vertical rod input to actuate a lower latch from a latched position to an unlatched position is additionally disclosed.