Rotary Knob Torque Coupling for Low-Force Assembly Retention
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Solution Overview
Problem
Existing household appliance control elements, such as rotary switches, often require additional components like leaf springs for torque transmission, which increase complexity and costs, and do not allow precise control over trigger and onset forces.
Innovation Solution
A control element with a rotating shaft and rotary button connected via a torque transmission device featuring inclined contact areas, eliminating the need for a leaf spring by using a groove spring connection, allowing for precise definition of trigger power through geometric design of intervention and counter-intervention sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If additional components like leaf springs are used for torque transmission, then the control element can be assembled, but the device complexity and manufacturing costs increase
Solution Approach 1:
The patent integrates the torque transmission function directly into the actuating shaft by forming a groove spring connection through injection molding. The actuating shaft combines multiple functions (rotation, torque transmission, and positioning) into a single component, eliminating the need for separate leaf springs and reducing overall device complexity
Solution Approach 2:
The actuating shaft is designed to be self-sufficient by incorporating the groove spring connection directly into its structure. The injection-molded groove creates an integrated torque transmission mechanism that eliminates dependency on external components, making the actuating shaft a self-contained functional unit
2Manufacturing precision
If conventional coupling methods are used, then assembly is possible, but precise control over trigger and onset forces cannot be achieved
Solution Approach 1:
The patent enables precise force control by varying geometric parameters of the groove spring connection, specifically the inclination angles of the contact surfaces. By adjusting these angles, the trigger force and onset force can be precisely defined and controlled without changing the overall coupling mechanism complexity
Solution Approach 2:
The groove spring connection employs asymmetric contact surfaces with different inclination angles (first angle and second angle). This asymmetry allows differential control over the insertion force and removal force, enabling precise definition of trigger and onset forces while maintaining a relatively simple coupling structure
3Ease of operation
If the rotary knob is easily inserted, then user operation is convenient, but the connection may not be secure enough
Solution Approach 1:
The groove spring connection creates a dynamic coupling mechanism where the elastic deformation of the actuating shaft allows easy insertion during assembly, while the same elastic properties provide secure retention during operation. The connection transitions from a compliant state during insertion to a locked state during use
Solution Approach 2:
The groove spring connection utilizes curved, inclined contact surfaces instead of flat or直角 interfaces. The arc-shaped engagement geometry allows smooth insertion through elastic deformation while maintaining secure connection through the geometric interlocking of the curved surfaces
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
This design reduces material and assembly costs, improves force coordination, and enhances the consistency of trigger performance across varying temperatures, providing a process-proof solution for the control element.
Implementation Method 1
the engagement section has a first contact surface inclined at a first angle to a rotation axis of the actuating shaft, and the counter-engagement section has a second contact surface inclined at a second angle to the rotation axis
Data Source
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AI summary
The invention relates to a household appliance (1), in particular a household cooking appliance, with a control element (9) for operating the household appliance (1), wherein the control element (9) comprises a rotatable actuating shaft (11) for actuating the control element (9), a rotary knob (20), and a torque transmission device (14) arranged between the actuating shaft (11) and the rotary knob (20) for transmitting a torque (M) from the rotary knob (20) to the actuating shaft (11), wherein the torque transmission device (14) is rotationally fixed to the actuating shaft (11) and the rotary knob (20), wherein the rotary knob (20) has an engagement section (22, 23, 48) and the torque transmission device (14) has a counter-engagement section (24, 25, 49) into which the engagement section (22, 23, 48) engages positively, and wherein the engagement section (22, 23, 48) and the counter-intervention section (24, 25, 49) are designed in such a way,that the insertion force (Fauf) for inserting the rotary knob (20) onto the torque transmission device (14) is less than the removal force (Fab) for removing the rotary knob (20) from the torque transmission device (14).