Dual-Thread Cement Board Screw for Low-Torque Pull-Out Resistance
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Solution Overview
Problem
Existing cement board screws face challenges in achieving quick and effective installation with low torque requirements while ensuring high resistance to pull-out, as they often require high torque and do not provide sufficient resistance post-installation.
Innovation Solution
The cement board screw features a combination of high and low threads along its shank, with counter threads, a tapered end, and a textured head, which allows for efficient penetration and bonding, reducing torque requirements and enhancing pull-out resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional single-thread screws are used, then the screw structure is simple, but the torque requirement is high and pull-out resistance is insufficient
Solution Approach 1:
The screw thread is segmented into two distinct thread types: a first thread with a first thread angle and a second thread with a second thread angle. This segmentation allows each thread type to perform different functions - the first thread provides initial penetration and bonding, while the second thread provides enhanced pull-out resistance, thereby resolving the contradiction between maintaining structural simplicity and improving pull-out resistance.
Solution Approach 2:
Different portions of the screw shank are given different thread characteristics. The first thread portion has a smaller thread angle optimized for penetration and bonding, while the second thread portion has a larger thread angle optimized for pull-out resistance. This local differentiation of thread quality allows the screw to achieve high pull-out resistance without requiring complex overall structural changes.
2Reliability
If high torque is applied during installation, then penetration and bonding are achieved, but the torque requirement increases and installation efficiency decreases
Solution Approach 1:
The threading is segmented into two functional zones along the screw shank. The first thread zone is designed with a smaller thread angle to facilitate initial penetration and bonding with the cement board, reducing the torque needed for installation. The second thread zone follows with a larger thread angle to provide enhanced grip and pull-out resistance. This segmentation allows reliable bonding to be achieved at lower torque levels compared to conventional single-thread designs.
Solution Approach 2:
The thread angle parameter is changed along the length of the screw shank. The first thread has a smaller thread angle (better for penetration and bonding), while the second thread has a larger thread angle (better for grip). This parameter variation along the screw length enables improved bonding quality at reduced torque requirements while maintaining installation ease.
3Strength
If the thread angle is increased, then pull-out resistance improves, but penetration ability and bonding quality deteriorate
Solution Approach 1:
The screw thread is divided into two sequential segments along the shank. The first thread segment has a smaller thread angle that is optimized for penetration and bonding quality. The second thread segment has a larger thread angle that is optimized for pull-out resistance. This segmentation resolves the contradiction by applying different thread angle characteristics to different functional zones of the screw.
Solution Approach 2:
Different thread angle qualities are applied to different portions of the screw. The first thread portion has a smaller thread angle for optimal bonding, while the second thread portion has a larger thread angle for optimal pull-out resistance. This local quality differentiation allows the screw to simultaneously achieve good bonding quality and high pull-out resistance.
4Reliability
If the screw penetrates deeply into cement board, then bonding improves, but the risk of over-spinning increases
Solution Approach 1:
The threading is segmented into two distinct portions along the screw shank. The first thread portion provides the primary bonding function during initial penetration. The second thread portion, with its larger thread angle, provides increased friction and grip that naturally limits further rotation, preventing over-spinning. This segmentation allows deep penetration for strong bonding while maintaining installation control.
Solution Approach 2:
The thread angle parameter changes along the screw shank length. The first thread has a smaller angle for penetration and bonding. The second thread has a larger angle that increases friction and resistance to rotation, serving as a mechanical stop that prevents over-spinning while allowing adequate penetration depth for strong bonding.
Data Source
AI summary
A cement board screw a high thread that begins on the tapered end, extends onto the shank and terminates at a second axial location along the shank. The high thread defines a high peripheral edge, where a leading flank and a trailing flank meet at the high peripheral edge and together define a high thread angle that is between about thirty degrees and about fifty-five degrees. A low thread begins on the tapered end, extends onto the shank and terminates substantially at a first axial location along the shank such that an axial length of the low thread is less than an axial length of the high thread. The low thread includes a leading flank and a trailing flank that meet at a low peripheral edge and together define a low thread angle that is between about fifty degrees and about seventy degrees.