Split Threaded Fastener for Heavy Machinery Pre-stressing
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Solution Overview
Problem
Heavy-duty machinery, such as forging presses, face challenges with large threaded fasteners that require mechanized equipment for installation and removal, leading to issues like nut lock-up, galling, and thread mismatch due to the large size and weight of components, as well as encrustation and deformation.
Innovation Solution
A fastener system comprising a half-divided circular ring with truncated conical surfaces and jackbolts that apply pre-stressing force without torque, allowing assembly and tensioning using ordinary hand tools, and a hollow cylinder with a truncated conical thrust surface to resolve forces radially and axially, ensuring secure engagement of threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large threaded fasteners are used to secure heavy-duty machinery components, then the fastening strength is sufficient to resist high pressures, but the fasteners require mechanized equipment for installation and removal
Solution Approach 1:
The fastener is divided into multiple segments: a body portion with internal threads, a split ring portion that can be opened, and jackbolts. This segmentation allows the fastener to be assembled by opening the split ring, placing it over the threaded column, and closing it with bolts, eliminating the need for mechanized installation equipment while maintaining high fastening strength
Solution Approach 2:
Jackbolts serve as intermediary devices to apply pre-stressing force to the fastener after assembly. These jackbolts can be manually operated to tension the fastener body against the threaded column, providing the necessary clamping force without requiring large mechanized torque application equipment
2Strength
If large threaded fasteners are used to secure heavy-duty machinery components, then the fastening strength is sufficient to resist high pressures, but nut lock-up and galling conditions occur
Solution Approach 1:
The split ring design allows the fastener to be pre-assembled onto the threaded column in a controlled manner without applying full load immediately. The ring can be opened to facilitate easy installation and then gradually closed with bolts, preventing sudden load application that causes galling and lock-up conditions
Solution Approach 2:
The fastener transitions from a static pre-loaded nut design to a dynamic assembly process where the split ring can be opened and closed. This dynamic capability allows for controlled installation and removal, preventing the thread distortion and lock-up that occur with static, heavily pre-loaded traditional nuts
3Device complexity
If traditional threaded fasteners are used, then simple construction is maintained, but thread deformation and mismatch occur during servicing
Solution Approach 1:
The separation of the fastener into a body portion and a split ring portion allows the internal threads to be protected within the closed ring structure. This segmentation prevents thread exposure to debris and contamination that cause galling, while the modular design facilitates easy removal and reinstallation without thread deformation
Solution Approach 2:
The split ring design extracts the threading operation from the installation process. Threads are engaged by simply placing the open ring over the column and closing it, rather than by rotating a nut onto threads. This eliminates the rotational friction and heat that cause thread pitch distortion and mismatch during servicing operations
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
Enables secure assembly and tensioning of large threaded columns without mechanized equipment, reducing nut lock-up and galling, and accommodating thread irregularities, ensuring reliable operation and maintenance of heavy-duty machinery.
Implementation Method 1
the conjugate pair of truncated conical surfaces resolve a force parallel to the central longitudinal axis generated by the stress generator toward a machine part to provide a component force directed radial inward toward the central longitudinal axis for urging the internal thread toward a mating thread on a tie rod
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A fastener includes a threaded circular ring (30) half divided along a plane intersecting a central longitudinal axis. One of the end walls (42) is formed with a truncated conical load-bearing surface that is seated on a truncated conical thrust surface (58) formed on a circular ring of a stress generator. The load bearing and thrust generating surfaces are arranged to present a conjugate pair of truncated conical surfaces to provide a favorable resolution of forces developed by torque applied to jack bolts distributed about an outwardly surrounding cylindrical stress generator body section.