Split Centering Sleeve for Residue-Free Facade Fastening
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Solution Overview
Problem
Existing centering sleeves for fastening facade elements on building substructures often leave residues in drill holes due to incomplete ejection, especially when using self-drilling screws with high feed rates, leading to assembly complications and material fatigue from differential thermal expansion.
Innovation Solution
A split hollow cylindrical centering sleeve with channel-like shell elements and a joint section, featuring a funnel-shaped interior and axially parallel longitudinal slots, which guides the fastener during assembly and automatically ejects from the drill hole once the fastener reaches the substructure, ensuring precise centering and secure fastening without residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional centering sleeve is used to guide the screw, then the screw can be centered in the oversized hole, but the sleeve residue remains in the drill hole causing assembly complications
Solution Approach 1:
The sleeve is divided into two functional parts: a guiding section that remains in the drill hole to provide centering, and an ejection section that is designed to be broken off and removed. The longitudinal slot creates a separation between these functions, allowing the sleeve to fulfill its centering purpose while enabling complete removal of excess material.
Solution Approach 2:
The ejection section of the sleeve is designed as a temporary component that serves its centering function during assembly and then is intentionally discarded. The breaking point allows the ejection section to be separated and removed, leaving only the necessary guiding portion in the drill hole.
2Productivity
If self-drilling screws with high feed rates are used to increase productivity, then assembly speed improves, but the sleeve cannot be ejected in time leading to residue problems
Solution Approach 1:
The ejection mechanism is prepared in advance through the predetermined breaking point and the interaction between the thread pitch and sleeve geometry. This preliminary design ensures that as the screw advances, the ejection section will naturally break off at the correct moment, even with high feed rates, without requiring additional ejection actions.
Solution Approach 2:
The screw itself serves the dual function of both fastening and ejection. As the screw thread engages with the sleeve, the rotational motion and axial advancement automatically trigger the breaking point mechanism, causing the ejection section to separate. The screw's own driving action provides the ejection function without requiring separate mechanisms.
3Ease of manufacture
If the sleeve interior is smooth to ease manufacture, then manufacturing is simpler, but the sleeve does not grip the screw thread effectively for centering
Solution Approach 1:
The sleeve interior features localized gripping elements (such as ribs or circumferential grooves) positioned at specific locations where screw thread contact occurs, while other portions of the interior remain smooth. This selective texturing provides necessary friction for centering accuracy only where needed, without complicating the overall manufacturing process.
Data Source
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AI summary
A sleeve (100, 200) for centering fasteners during the assembly of components to the substructure of a building envelope is essentially designed as a hollow cylindrical sleeve body (150) or a split hollow cylindrical sleeve body (250). It comprises at least two trough-like shell elements, each with a head end (112, 162, 212, 262) and a rear end (114, 164, 214, 264). The shell elements are grouped symmetrically around a central axis A and span a space (190, 290) between them, with mutually oriented inner surfaces (130, 140, 230, 240). The shell elements are spaced apart from each other and separated by axially parallel longitudinal slots (170, 180, 270, 280), except for a connecting hinge section (120, 220) at the head end (112, 162, 212, 262). These sleeves are placed on a fastener and allow precise centering in the pre-drilled hole of, for example, a facade panel.The sleeve remains in the pre-drilled hole until the fastener is centered and is then safely ejected by the advancement of the fastener.