Actuator Assembly With Undercut Shaft Joint for Contact Alignment
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Solution Overview
Problem
Conventional methods for securing a plunger to a shaft in electrical devices suffer from fatigue and failure, and lack precise dimension control, leading to wear and reduced lifespan of the devices.
Innovation Solution
An actuator assembly with a shaft and plunger is secured using an undercut and a flared head formed through cold forming, ensuring robust and precise alignment of movable contacts with fixed contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fastening techniques (clips, welding, threaded interfaces) are used to secure the plunger to the shaft, then the assembly can be manufactured, but the connection suffers from fatigue and failure over time
Solution Approach 1:
The connection is divided into two functional zones: a tapered section for stress distribution and an undercut section for mechanical interlocking. This segmentation allows each zone to handle specific stresses independently, preventing fatigue propagation through the entire connection.
Solution Approach 2:
The connection combines two geometric features (tapered profile and undercut) into a composite structural solution. The tapered portion provides gradual stress transition while the undercut provides positive mechanical engagement, creating a composite connection system that overcomes the limitations of single-method fastening.
2Manufacturing precision
If conventional fastening techniques are used to secure the plunger to the shaft, then assembly can be manufactured, but precise dimension control is not achieved
Solution Approach 1:
The undercut geometry is pre-formed in the plunger during manufacturing, creating a built-in positioning feature that automatically ensures precise alignment and dimension control when the shaft is inserted, eliminating the need for post-assembly adjustment or complex fixtures.
3Ease of manufacture
If the plunger is secured to the shaft with rotation, then the assembly can be assembled, but wear occurs on housings and other components
Solution Approach 1:
The undercut creates an asymmetric geometric interlock between the plunger and shaft that prevents rotational movement. The non-symmetric shape of the undercut feature ensures that the plunger can only be inserted in one orientation and cannot rotate, eliminating wear caused by rotational friction on housing components.
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 method enhances device performance and longevity by reducing wear, requiring less maintenance and allowing for simpler, cheaper components with improved precision.
Implementation Method 1
The plunger is placed in a magnetic field, e.g., of an electromagnetic coil. Selective activation of the electromagnetic coil causes the plunger (and thus the shaft and the movable contact(s)) to move relative to the coil.
Implementation Method 2
altering the shaft may include cold forming a flared head at the second end of the shaft and/or causing material of the shaft to extend into the undercut
Data Source
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AI summary
An electrical device includes an actuator assembly configured to facilitate selective opening/closing of an electrical circuit. A plunger is positioned to be acted on by a magnetic field, a shaft is coupled to the plunger, and a movable contact is coupled to the shaft. The plunger includes an axial opening and an undercut formed in a surface defining the axial opening. The shaft is inserted into the opening and an end of the shaft extending from the opening is altered to increase a diameter of the shaft to prevent passage through the opening and such that a portion of the shaft extends into the undercut.