Cylindrical Lockset Knob Catch Spring and Torque Plate Design
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Solution Overview
Problem
Conventional cylindrical locksets are bulky, expensive, and lack desired strength, durability, and versatility, with cantilever-type knob catch assemblies often providing inadequate handle-retaining force or being overly stiff.
Innovation Solution
A cylindrical lock assembly featuring a wrap-around catch spring with a continuously curved segment greater than 180 degrees, a key spindle assembly with retractor activation cams, and a torque plate mechanism, all made from stamped sheet metal to reduce costs and enhance functionality, allowing selection between standard and rigid lock trim configurations without structural modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cantilever-type knob catch assemblies are used, then the structure is simple, but the handle-retaining force is either weaker than desired or the spring is too stiff and easily overstressed
Solution Approach 1:
The spring is segmented into multiple active coils rather than being a single cantilevered element. This segmentation allows the load to be distributed across multiple coils, providing adequate handle-retaining force while preventing any single point from being overstressed, thereby improving both strength and reliability
Solution Approach 2:
The spring design parameters are optimized by specifying precise coil dimensions, wire diameter, and active coil count to achieve the desired force characteristics. The spring rate is carefully calculated to provide sufficient retaining force without being overly stiff, resolving the contradiction between strength and durability
2Strength
If large cast spindle bearings are used to house lever return springs, then the lockset provides desired strength and durability, but the fabrication cost increases due to the casting process
Solution Approach 1:
The lever return springs are extracted from the spindle bearing housing and relocated to the lock body. This eliminates the need for large cast spindle bearings, allowing the use of simpler, more cost-effective bearing components while maintaining the required strength and durability through the lock body's structural design
Solution Approach 2:
The lock body is designed to serve multiple functions: it houses the retractor mechanism and also provides housing for the lever return springs. This multi-functionality eliminates the need for separate specialized components like cast spindle bearings, reducing manufacturing complexity and cost while maintaining structural integrity
3Ease of operation
If internal rose cages are used to house lever return springs, then the lockset functions properly, but the trim becomes very large and prominent
Solution Approach 1:
The lever return springs are extracted from the traditional internal rose cage housing and relocated to the lock body. This eliminates the need for large rose cages, allowing the trim to be significantly reduced in size while maintaining all necessary lockset functions
Solution Approach 2:
The spring housing arrangement is repositioned from the radial dimension (rose cage around the spindle) to the axial dimension (within the lock body structure). This dimensional change allows the trim to be minimized while the spring mechanism remains functional within the lock body's internal volume
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 provides a cost-effective, strong, and versatile lockset with improved handle retention and reduced component complexity, supporting a range of lock functions while minimizing configuration differences and component variations.
Implementation Method 1
Release-actuating force imposed on the knob catch assembly elastically deforms the substantially continuously curved segment of the wrap-around catch spring
Data Source
AI summary
A cylindrical lockset comprises a multiple-compartment lock cage subassembly. A retractor is housed within a middle lock cage compartment. Spindle return torsion springs, for biasing corresponding handle-carrying spindles to their default positions, are housed within axially adjacent lock cage compartments. A torque plate transfers torque from the lock cage subassembly to relatively radially distal trim posts. A knob catch assembly seated in each handle-carrying spindle comprises a generally elliptically-shaped wrap around catch spring and a knob catch backup washer to resist axial loads produced by efforts to pull a handle off of the spindle. A key spindle provides a dog travel window defined by a closed, continuous edge of the key spindle, which window is positioned opposite of an axially-extending seam of the key spindle.