Two-Stage Expansion Screw for Dowel Systems
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Solution Overview
Problem
Existing dowel systems for spaced installation face challenges in securely anchoring expansion anchors in subsoil and transferring loads efficiently, often requiring high torque for screwing, which can lead to anchor failure due to excessive tensile forces.
Innovation Solution
The dowel system incorporates a two-stage expansion screw with a first threaded section for initial anchoring and a second threaded section that engages only after the first is securely anchored, reducing axial propulsion resistance and allowing lower torque screwing, along with a conical widening section and rounded thread flanks to minimize material displacement and torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single threaded section is used on the expansion screw, then the screwing process requires high torque to overcome resistance, but this high torque can cause anchor failure due to excessive tensile forces
Solution Approach 1:
The expansion screw is divided into two distinct threaded sections: a first threaded section for engaging the first expansion anchor and a second threaded section for engaging the second expansion anchor. This segmentation allows the screwing process to occur in two stages, reducing the torque required at each stage and preventing anchor failure that would result from applying excessive torque in a single stage.
2Productivity
If the feed section is designed to be drawn into the second expansion anchor during initial screwing, then the first expansion anchor must generate high axial tensile force, but this increases the complexity of the screwing process
Solution Approach 1:
The expansion screw is segmented into two threaded sections that engage the expansion anchors in sequence. The first threaded section engages the first expansion anchor while the feed section is drawn into the second expansion anchor. The second threaded section then engages the second expansion anchor. This segmentation simplifies the overall process by breaking it into two manageable stages rather than requiring one complex high-force stage.
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 ensures secure anchoring in subsoil with reduced torque requirements, preventing anchor failure and facilitating easier installation while maintaining load transfer capabilities.
Implementation Method 1
The expansion screw has a first threaded section for screwing into the first expansion anchor and a feed section for expanding the second expansion anchor
Implementation Method 2
the first expansion anchor must be able to introduce an axial tensile force into the subsoil that is greater than the force that is necessary to pull the feed section into the second expansion anchor
Implementation Method 3
a second threaded section is arranged on the expansion screw of the dowel system in the insertion direction behind the draw-in section. After the drawing-in section has been pulled into the second expansible plug, the second threaded section engages in the second expansible plug and, in this second expansion phase, generates an axial propulsion
Implementation Method 4
The drawing-in section preferably has a conical widening section, the diameter of the widening section increasing towards the rear end of the expansion screw in the direction of insertion
Implementation Method 5
the thread flank of the second threaded section is rounded. A rounded thread flank has the advantage over a pointed thread that the thread flank does not cut into the material of the second expansible fixing plug, or only slightly, but rather displaces the material of the second expansion anchor radially outwards
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The anchor system (1) has an expander (5) which is provided with a primary threaded portion for screwing into an expansible plug (3). A collection portion (13) is extended with respect to primary threaded portion such that collection portion is fed into expansible plug (4) by screwing the primary threaded portion in expansible plug (3). The secondary threaded portion (15) is provided behind the collection portion in insertion direction (E).