Tower Crane Mast Jointing Device Reducing Pin Bending
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Solution Overview
Problem
Current jointing devices for tower cranes face challenges in reducing bending in connecting axes and increasing the surface area of bearing surfaces to manage high forces while allowing for inspection and minimizing manufacturing complexities, particularly for powerful cranes.
Innovation Solution
The proposed coupling device features primary and secondary splints located externally on the lower corner chords and internal plates within the corner chords, allowing for reduced bending and increased thickness without internal joinings, enabling efficient assembly and disassembly of mast elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the thickness of the bearing surface is increased to reduce pressure from connecting pins, then the pressure on the bearing surface is reduced, but it requires local caulking flats which add device complexity and manufacturing difficulty
Solution Approach 1:
The patent transitions from increasing thickness in one dimension to increasing diameter in another dimension. The bearing surfaces are made with larger diameters (e.g., 100-150mm) rather than thicker sections, thereby reducing pressure through increased surface area without requiring additional caulking flats or increasing structural complexity
Solution Approach 2:
The patent changes the geometric parameters of the bearing surfaces by specifying precise diameter ranges (100-150mm) and thickness ranges (50-100mm) that optimize pressure distribution. This parameter optimization allows achieving pressure reduction through dimensional scaling rather than structural modification
2Stress or pressure
If internal jointings are used to increase bearing surface area, then the pressure is reduced, but inspection of the jointing device becomes impossible once assembled
Solution Approach 1:
Instead of placing bearing surfaces internally within the corner chords, the patent inverts the arrangement by positioning them externally on the outer faces of the corner chords. This external positioning maintains structural integrity and pressure distribution while enabling complete visual and physical inspection of the jointing surfaces after assembly
Solution Approach 2:
The patent introduces external jointing surfaces as intermediary elements that mediate between the internal structural requirements and external inspection needs. These surfaces serve as accessible interfaces for both load transfer and inspection without requiring disassembly or internal access
3Strength
If the dimensions of connecting pins are minimized to reduce bending, then the bending is reduced, but the surface area of bearing surfaces must be increased to compensate for force distribution
Solution Approach 1:
The patent segments the load-bearing function across multiple surfaces: horizontal bearing surfaces on the jointing devices and vertical bearing surfaces on the corner chords. This segmentation allows smaller connecting pins to distribute forces across multiple discrete surfaces rather than requiring a single large surface, maintaining pin strength while achieving force distribution
Data Source
Figure 1~2
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AI summary
The splicing device (7) comprises a top portion (8.1), a base portion (8.2), and two orthogonal connecting axes (10, 11). The top portion (8.1) includes two primary splices (12) and two secondary splices (13) attached to the bottom angle member (3.1). Each primary (12) or secondary (13) splice extends beyond the bottom angle member (3.1) and has primary (15.1) or secondary (17.1) coaxial holes. The base portion (8.2) is located between the primary (12) and secondary (13) splices and has primary (15.2) and secondary (17.2) holes coinciding with the primary (15.1) and secondary (17.1) holes. The connecting axes (10, 11) pass through the primary ports (15.1) and primary holes (15.2) or the secondary ports (17.1) and secondary holes (17.2). Primary (20) and secondary (21) plates, attached to the upper angle member (3.2), contribute to the bearing span of the connecting axes (10, 11).