Mortise Lock Latch Retraction Under Offset Load and Stall
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Solution Overview
Problem
Conventional stepper motor linear actuators in mortise locks face issues with offset loads, leading to excessive wear, reduced efficiency, and premature failure due to side loading forces, and are often bulky, complicating latch bolt retraction.
Innovation Solution
A motor assembly with a PCB, microprocessor, and actuation housing that accommodates offset loads, includes a shaft and actuating element offset from the motor shaft, and uses a two-cycle operation to detect and overcome stall conditions, applying varying power levels for efficient latch bolt retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional stepper motor linear actuators are used in mortise locks, then the motor can be offset from the centerline of the latch bolt to avoid interference, but this creates side loading forces which add additional load to the latch and motor, causing premature failure
Solution Approach 1:
The patent introduces a side-loading bearing as an intermediary component between the motor shaft and the latch bolt. This bearing specifically accommodates and absorbs the side loading forces generated by offset motor positioning, preventing these forces from being transmitted to the motor and latch mechanism. The bearing acts as a mediator that resolves the conflict between maintaining offset positioning for interference avoidance and preventing premature failure from side loading.
Solution Approach 2:
The motor assembly is segmented into distinct functional components: the motor itself, the side-loading bearing, the actuating element, and the latch mechanism. This segmentation allows each component to perform its specific function independently - the motor generates rotational motion, the bearing handles side loading, the actuating element transmits force to the latch, and the latch provides the locking function. This modular approach enables optimized performance for each component without compromising the others.
2Ease of manufacture
If conventional linear actuators are used, then the motor can operate with standard axial loading design, but the actuators are often large and cumbersome to incorporate within a mortise lock
Solution Approach 1:
The patent merges multiple functions into a single compact motor assembly unit. The side-loading bearing, actuating element, and motor are integrated into a unified assembly that fits within the mortise lock housing. This combining of components reduces the overall volume compared to using separate conventional linear actuators while maintaining ease of manufacture through a standardized assembly process.
3Productivity
If the latch bolt is retracted quickly to prevent door operators from pulling the door open, then security is improved, but additional loading forces can inhibit successful operations of the latch bolt
Solution Approach 1:
The side-loading bearing is pre-installed and positioned to accommodate lateral forces before the latch bolt retraction operation begins. This preliminary preparation ensures that when the motor applies force to retract the latch bolt quickly for security, the bearing is already in position to absorb any side loading forces that may arise, preventing operational failure during the rapid retraction.
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 ensures efficient and reliable latch bolt retraction despite offset loads, reduces wear, and maintains motor assembly longevity by detecting and adjusting power and speed to overcome stall conditions.
Implementation Method 1
Stepper motors convert pulsing electrical current, controlled by a stepper motor driver, into precise one-step movements of a gear-like toothed component around a central shaft
Implementation Method 2
the microprocessor is configured to detect a stall signal as the motor assembly performs the initial cycle operation, the stall signal indicating failure of a latch bolt retraction parameter
Data Source
AI summary
A mortise lock and motor-assisted method of operating. The mortise lock comprises a case, a lever arm, a latch bolt having a linkage, a PCB having a controller and a microprocessor, and a motor assembly. An actuating element including a projection is disposed outside the motor assembly to move the latch bolt from the extended to retracted positions. The microprocessor is configured to detect a stall signal during the motor assembly's initial cycle operation indicating failure of a latch bolt retraction parameter. Upon detection of the stall signal, the controller causes the motor assembly to perform a second cycle operation to move the latch bolt from the extended position to the retracted position.