Autotrip Plunger with External Spring Mounting
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Solution Overview
Problem
Molded case circuit breakers face challenges in designing autotrip plungers with internal springs that do not compromise mechanical strength and allow easy installation, while also minimizing space usage within the circuit breaker frame.
Innovation Solution
The autotrip plunger features a monolithic design with two body sections, where the second body section includes an arbor shaft with radial protrusions for securing a compression spring outside the housing, allowing easy mounting and dismounting without occupying internal space, and a latching element for secure tripping action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the compression spring is placed inside the plunger body, then the mechanical strength of the plunger is maintained, but the installation and disassembly of the spring becomes difficult
Solution Approach 1:
The compression spring is extracted from the internal cavity of the plunger body and relocated to the external surface. The plunger body includes a through-opening that allows the spring to be mounted on the outer surface, where it can be easily installed and removed without compromising the internal structural integrity of the plunger.
2Volume of stationary object
If the compression spring is placed outside the housing, then the internal space of the circuit breaker is preserved, but the spring may interfere with external components
Solution Approach 1:
The compression spring is nested on the outer surface of the plunger body, utilizing the plunger's external geometry as a mounting structure. The spring is positioned within the envelope of the plunger body, and the plunger housing includes a through-opening that allows the spring to be accessed and installed from the outside while maintaining compact integration.
3Strength
If the plunger is designed as a single integrated piece, then the mechanical strength is maximized, but the spring installation becomes complex
Solution Approach 1:
The plunger body is designed as a single integrated piece with a through-opening that segments the external surface into accessible regions. This through-opening provides a pathway for spring installation without requiring the plunger body itself to be divided into separate parts, thus maintaining the structural advantages of an integrated design while enabling easy spring access.
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 enables easy assembly and disassembly of the compression spring, maintaining mechanical strength and minimizing the envelope occupied by the autotrip plunger and spring combination, thus preserving internal space within the circuit breaker.
Implementation Method 1
The energy for doing this is provided by a compression spring called 'autotrip plunger spring'.
Implementation Method 2
a compression spring (2) arranged around the arbor shaft (6) of the second body section (4)
Data Source
Figure 1~2
Figure 3~4
Figure 5(1)~5(6)
AI summary
The present invention is related to an autotrip plunger (1) of a circuit breaker (20) for opening contacts of the circuit breaker (20) to install and uninstall the circuit breaker (20) from a current source, comprising a compression spring (2), wherein the autotrip plunger (1) comprises a first body section (3) and a second body section (4), the first body section (3) having a contact surface (5) for contacting a tripping element of the circuit breaker (20), the second body section (4) comprising an arbor shaft (6) for fitting in the compression spring (2), whereby at the free end (7) of the arbor shaft (6) the arbor shaft (6) comprises at least one radial protrusion (8, 9) for holding the compression spring (2). The invention is further related to a circuit breaker with such an autotrip plunger (1).