Variable Spring Rate Chassis for Interchangeable Door Locksets
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Solution Overview
Problem
Conventional door locksets require distinct chassis configurations for knob and lever interfaces, making it impractical to switch between the two without purchasing a new handle set, as the spring design must balance internal forces and user comfort differently for each type.
Innovation Solution
A lockset apparatus with a common chassis featuring a spindle, spring collar, and dual torsion springs that can be configured for either knob or lever interfaces by adjusting the handle's engagement with the spindle and spring collar, allowing for interchangeable return torque mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single spring design is used for both knob and lever interfaces, then manufacturing complexity is reduced, but the spring cannot satisfy the different torque requirements of each interface type
Solution Approach 1:
The spring system is made dynamically configurable through a collar mechanism that can be positioned at different locations along the spring. This allows the same physical spring to provide different effective torque characteristics: when the collar is positioned closer to the spindle, it provides lighter torque suitable for knobs, while positioning the collar farther from the spindle increases the effective torque for lever interfaces. This dynamic adjustment resolves the contradiction by enabling one spring design to satisfy multiple torque requirements.
Solution Approach 2:
The invention changes the effective parameter of the spring system by varying the collar position along the spring length. This parameter change (collar location) modifies the mechanical advantage and effective torque without requiring a different spring. The collar acts as a variable leverage point, transforming the same spring into different torque-providing configurations to match either knob or lever interface requirements.
2Reliability
If distinct chassis configurations are manufactured for knob and lever interfaces, then each interface type receives optimized spring design, but product variety increases requiring separate handle set purchases
Solution Approach 1:
The chassis is designed with universal functionality to support both knob and lever interfaces using the same spring mechanism. The collar's adjustable position along the spring enables the single chassis to adapt to different interface types, eliminating the need for separate chassis configurations. This multi-functionality allows consumers to interchange handle types without purchasing new handle sets, while still receiving interface-optimized performance.
Solution Approach 2:
The spring system is segmented into adjustable segments by the collar mechanism. The collar divides the spring into functional segments that can be selectively engaged, allowing the same chassis to configure the spring differently for knobs versus levers. This segmentation enables flexibility and adaptability without requiring entirely separate chassis designs.
3Force
If a heavier spring is used for lever interfaces to counteract the offset center of mass, then lever return torque is sufficient, but the spring becomes too strong for comfortable knob operation
Solution Approach 1:
The collar position is dynamically adjusted based on the interface type: for lever interfaces requiring higher return torque, the collar is positioned farther from the spindle to increase mechanical advantage; for knob interfaces requiring lighter operation, the collar is positioned closer to the spindle to reduce effective torque. This dynamic positioning allows the same spring to provide appropriate force levels for different interfaces without compromising user comfort.
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
Enables flexible and cost-effective conversion between knob and lever interfaces without needing separate locksets, reducing manufacturing complexity and user installation time, while distributing return torque loads to extend spring life and reduce manufacturing variations.
Implementation Method 1
a first biasing element rotationally urging the spindle toward a spindle home position
Implementation Method 2
a second biasing element rotationally urging the spring collar toward a spring collar home position
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An apparatus including a chassis assembly having a housing, a spindle rotatably mounted to the housing, a spring collar rotatably mounted to the housing, a first biasing element rotationally urging the spindle toward a spindle home position, and a second biasing element rotationally urging the spring collar toward a spring collar home position. The apparatus may further include a handle mounted on the chassis such that the chassis biases the handle to a handle home position with a return torque. The handle is engaged with the spindle such that the first biasing element contributes to the return torque. In certain embodiments, the handle may further be engaged with the spring collar such that the second biasing element contributes to the return torque.