Fastener Holding Spanner With Threaded Locking Passage
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Solution Overview
Problem
Existing fastener holding spanners face challenges in high-torque applications, particularly in large fasteners used in flanged connections, where limited access and high torque requirements make assembly and disassembly difficult, often requiring two-person operations and risking physical strain or safety issues due to frictional binding between the spanner and nut or bolt head.
Innovation Solution
A fastener holding spanner design featuring a spanner head with a clearance aperture having multiple internal faces, including flat and concave surfaces, and a through passage that can accommodate a threaded member to prevent rotation, allowing for secure engagement and easy release, reducing manufacturing costs by allowing casting rather than machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spanner with a polygonally-shaped opening is used to restrain a nut or bolt head, then the spanner can hold the fastener during torque application, but the spanner and fastener bind together due to friction under high torque, making release difficult and requiring forceful measures
Solution Approach 1:
The aperture is segmented into multiple discrete loading points (at least three points) around its circumference, allowing the fastener to rotate slightly and contact different faces sequentially. This segmentation prevents continuous frictional binding while maintaining secure holding during torque application.
Solution Approach 2:
The aperture is designed to dynamically adapt during operation: initially providing clearance for easy engagement, then allowing controlled rotation to distribute loading across multiple points, and finally maintaining stable restraint during torque application. The aperture transitions from a static clearance fit to an active multi-point engagement system.
2Reliability
If the aperture is made as a close fit over the bolt to prevent rotation, then the holding capability improves, but the spanner becomes difficult to fit and remove, and binding occurs under torque
Solution Approach 1:
Different regions of the aperture have different functional qualities: the overall aperture provides clearance for easy fitting, while specific localized areas (loading points) provide concentrated contact for secure holding. This local differentiation allows both easy engagement and reliable restraint.
Solution Approach 2:
The aperture is pre-configured with multiple loading points positioned to engage as the fastener rotates into place. This preliminary arrangement ensures that during normal operation, the fastener naturally contacts the loading points without requiring precise alignment or forceful insertion.
3Reliability
If a grub screw is used to secure the spanner to the fastener, then the holding capability improves, but the spanner requires additional components and assembly steps
Solution Approach 1:
The spanner aperture itself provides the holding function through its multi-point loading design, eliminating the need for external securing mechanisms like grub screws. The aperture's geometry and loading point arrangement enable it to self-restrain the fastener during torque application without additional components.
4Manufacturing precision
If the spanner aperture is machined to form a hexagonal shape, then the precision of engagement improves, but the manufacturing cost increases
Solution Approach 1:
The aperture geometry is designed with specific parameters: multiple loading points arranged around the circumference with appropriate spacing, and a overall clearance fit dimension. These parameters can be achieved through casting or forming processes rather than precision machining, reducing manufacturing cost while maintaining functional precision.
Data Source
AI summary
A fastener holding spanner comprises a spanner head defining an aperture capable of engaging during use with a correspondingly-sized nut or bolt head of a fastener, with a clearance there-between, and at least one arm extending from the spanner head. During use of the spanner one of the at least one arms is capable of engaging with an abutment surface adjacent to a nut or bolt head of a fastener engaged by the spanner head upon rotation of the nut or bolt head under applied torque. The aperture comprises a plurality of internal faces, at least two of which are engaging faces. The engaging faces are substantially flat and are arranged to engage with flat faces of a nut or bolt head engaged by the spanner during use. At least one of the internal faces of the aperture is non-engaging with the nut or bolt head during use, the at least one non-engaging face located in between the at least two engaging faces. The aperture further comprises at least one through passage penetrating at least one of the internal faces, the at least one through passage having a longitudinal axis and being at least partially threaded over at least part of its length. In use a threaded member having a flat end may be screwed into the at least one passage, the flat end of the threaded member to contact under pressure a face of a nut or bolt head engaged by the spanner to prevent relative rotation between the spanner and the nut or bolt head. At least two engaging faces of the aperture are distal from the threaded member and located on opposing sides of the longitudinal axis of the at least one through passage.