Segmented Screw Thread Design for High Pull-Out Resistance
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Solution Overview
Problem
Existing screws fail to provide an improved holding force when attaching elements like plates to substructures, particularly in wood, without pre-drilling, and often require complex thread configurations to achieve secure connections.
Innovation Solution
A screw design featuring two threaded sections with the same core diameter but different pitches and outside diameters, where the retaining thread has a smaller pitch and larger outside diameter than the screw thread, allowing for a secure pull-out-resistant connection without pre-drilling, and optionally including a thread-free section and a countersunk screw head for enhanced usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single threaded section is used in conventional screws, then the screw structure is simple, but the holding force and pull-out resistance are insufficient
Solution Approach 1:
The screw thread is divided into two distinct threaded sections: a first threaded section with a first pitch and a second threaded section with a second pitch. This segmentation allows each section to perform different functions - the first section engages with the workpiece to create initial thread engagement, while the second section provides enhanced holding force and pull-out resistance through a different pitch configuration, thereby resolving the contradiction between simplicity and holding strength.
Solution Approach 2:
Different portions of the screw shank are given different thread properties. The first threaded section has a first pitch optimized for initial engagement and thread formation in the workpiece, while the second threaded section has a second pitch optimized for maximum holding force and resistance to pull-out. This local differentiation of thread quality allows each section to be optimized for its specific function, resolving the contradiction between simple structure and enhanced holding capacity.
2Strength
If the retaining thread has a smaller pitch and larger outside diameter, then the pull-out resistance is improved, but the thread engagement complexity increases
Solution Approach 1:
The thread system is segmented into two sections with different pitch and diameter characteristics. The second threaded section specifically employs a smaller pitch and larger outside diameter to maximize pull-out resistance, while the first threaded section uses different parameters optimized for initial engagement. This segmentation allows the complex thread parameters to be applied only where needed for pull-out resistance, rather than throughout the entire screw length.
3Reliability
If a thread-free section is introduced to separate the two threaded sections, then the thread engagement reliability is improved, but the screw structure becomes more complex
Solution Approach 1:
A thread-free section is introduced to physically separate and isolate the first threaded section from the second threaded section. This segmentation prevents interference between the two different pitch threads, ensuring that each threaded section engages independently with the workpiece without thread engagement conflicts. The separation enhances reliability by eliminating potential interference issues while maintaining a relatively simple overall screw structure.
Data Source
Figure 1~2
Figure 3~6
Figure 7
AI summary
The invention relates to a screw for connecting a plate to a substructure thereof, in particular as a corner connector screw, containing, along a screw shaft, a threaded segment (6) proceeding from the screw driving end (1) and having a retaining thread (7) and a threaded segment (9) proceeding from the screw tip and having a screwing thread (10). Both threaded segments (6, 9) have the same core diameter. The retaining thread (7) has a larger outside diameter and a smaller pitch than the screwing thread (10). A thread-free segment (8) is provided between the two threaded segments. The length of the thread-free segment corresponds to the thickness of a plate to be screwed tight.