Rail Vehicle End Mask Fastening for Tolerance-Accommodating Assembly
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Solution Overview
Problem
Conventional bolt and nut assemblies for attaching a rail vehicle mask to a structural element face challenges due to manufacturing and assembly tolerances, as well as limited accessibility, which complicates the attachment process and often necessitates glue fixation.
Innovation Solution
A fastening device comprising a bolt with a threaded tip, a tubular bushing, a sleeve with a large internal diameter, a nut, and a spacer, allowing for adjustable and secure mechanical fixation that accommodates tolerances and provides accessibility from outside the driver's cabin, using a threaded connection and additional components like a lock nut and locking washer for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional bolt and nut assembly is used for attaching the mask, then the mechanical connection is simple, but the assembly is difficult due to lack of accessibility from inside the driver's cabin
Solution Approach 1:
The patent inverts the conventional fastening approach by positioning the nut on the accessible side (inside the driver's cabin) and the bolt on the inaccessible side (outside). The bolt passes through the mask and engages with the nut from the exterior, allowing the nut to be accessed and tightened from inside the cabin while the bolt head remains outside.
Solution Approach 2:
The patent introduces a specialized fastening device as an intermediary between the mask and the structural element. This device includes a bolt with an enlarged head that rests against the mask, a nut that engages with the bolt, and a washer that distributes the load. This intermediary mechanism enables the connection despite the accessibility constraints.
2Manufacturing precision
If glue fixation is used to compensate for tolerances, then the assembly tolerances are accommodated, but the mechanical connection strength is reduced
Solution Approach 1:
The patent employs adjustable parameters in the fastening device, particularly the length of the bolt and the position of the nut along the bolt threads. This adjustability allows the fastening device to accommodate tolerance variations in the assembly while maintaining a strong mechanical connection. The bolt can be inserted at different depths and the nut positioned at different locations to compensate for dimensional variations.
Solution Approach 2:
The fastening device incorporates dynamic adjustment capabilities during assembly. The bolt can be inserted and adjusted to the correct depth, and the nut can be positioned and tightened to accommodate tolerance variations. This dynamic adjustment process enables the system to adapt to manufacturing tolerances while maintaining strong mechanical connections.
3Strength
If the bolt shank diameter is increased to improve connection strength, then the mechanical strength is improved, but the tolerance accommodation capability is reduced
Solution Approach 1:
The patent employs asymmetric design in the bolt structure, with an enlarged head portion and a smaller shank portion. The enlarged head provides a large bearing surface for load distribution and strong mechanical engagement, while the smaller shank diameter maintains the ability to accommodate tolerance variations. This asymmetric geometry allows the bolt to simultaneously provide high connection strength and tolerance accommodation.
Solution Approach 2:
The bolt is segmented into distinct functional portions: an enlarged head for load bearing and mask engagement, a shank for insertion and thread engagement, and threaded portions for nut engagement. This segmentation allows each portion to be optimized for its specific function - the head for strength, the shank for tolerance accommodation, and the threads for secure fastening.
Data Source
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AI summary
A fastening device 16 for connecting an end mask 12 of a rail vehicle 10 to a structural element 14 of a body of the rail vehicle 10, comprises a fastening bolt 20 having a head 22 and a shank 24 provided with a threaded tip portion 26, a tapered nut 28 provided with an inner thread 30 for engagement with the threaded tip portion 26 of the shank 24, a tubular bushing 32 provided with a threaded through hole 34 and a mounting flange 36, a sleeve 38 having an externally threaded wall 40 for engagement with the threaded through hole 34, a lock nut 42, a spacer 44 having a through hole 46 and a flat back face 48 and a locking washer 50. The flat base 60 of the nut 28 has to be wide enough to ensure that it rests on the protruding axial end 58 of the sleeve 38 irrespective of the position of the bolt 20 into the sleeve 38. Similarly, the dimensions of the flat back face 48 of the spacer 44 are such that the back face 48 rests on the protruding axial end 62 of the sleeve 38 irrespective of the position of the bolt 20 into the sleeve 38.