Multi-Start Punch and Draw Stud Threads for Faster Hole Punching
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Solution Overview
Problem
The existing punch systems for installing conduit runs in electrical boxes are inefficient due to the time-consuming process of attaching the knockout punch to the draw stud, which can take up to sixty seconds per hole, especially when multiple holes need to be punched.
Innovation Solution
A punch system with a multi-start thread on both the punch and the draw stud, allowing for faster attachment and self-locking mechanism without the need for a nut, reducing the number of rotations required to secure the punch onto the draw stud, thereby enhancing efficiency and reducing assembly time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a standard single-start thread is used on the draw stud and punch, then the attachment is secure and reliable, but the number of rotations required to attach the punch is excessive (30-60 seconds)
Solution Approach 1:
The patent changes the thread parameter from single-start to multi-start (specifically 3-start or 4-start threads). This parameter change increases the lead of the thread, allowing the punch to advance faster along the draw stud during rotation. The multi-start thread configuration reduces the number of rotations needed to achieve full engagement from 30-60 seconds down to approximately 5-10 seconds, directly improving attachment speed while maintaining secure fastening.
2Reliability
If a nut is used to secure the punch to the draw stud, then the attachment is secure, but the device complexity and number of components increase
Solution Approach 1:
The patent extracts and eliminates the nut from the assembly by using a multi-start thread on the draw stud that directly engages with a corresponding multi-start thread on the punch. This removes the intermediate fastening component (nut) entirely, reducing device complexity while maintaining secure attachment through the self-locking nature of the multi-start thread engagement combined with friction and geometric interference.
Solution Approach 2:
The patent merges the fastening function into the threaded connection itself. The multi-start threads on both the draw stud and punch are designed to engage directly with each other, combining the drawing stud, the fastening mechanism, and the punch into a more integrated assembly. This eliminates separate fastening components and simplifies the overall device structure.
3Reliability
If the draw stud is made longer to accommodate deeper threads, then the attachment is more secure, but the time required to attach the punch increases
Solution Approach 1:
The patent changes the thread geometry parameter from single-start to multi-start, which increases the lead (axial advance per rotation). This allows the thread engagement to progress faster along the length of the draw stud, reducing the attachment time even when adequate thread engagement depth is maintained. The multi-start configuration enables secure attachment with fewer rotations, preventing the time increase that would otherwise result from longer draw studs.
Data Source
AI summary
A punch according to some embodiments of the disclosure includes a body having a punching edge and a wall forming a passageway therethrough, the wall having a multi-start thread formed thereon, and a draw stud according to some embodiments of the disclosure includes an elongated cylinder having a multi-start thread thereon which is configured to be coupled to the multi-start thread of the punch. The number of starts provided on the punch corresponds to the number of starts provided on the draw stud. The multi-start thread on the punch is engaged with the multi-start thread on the draw stud in use. A method using same to punch a hole in sheet metal is also provided.