Seal Washer Fastener Structure for Low-Force Water Sealing
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Solution Overview
Problem
Conventional threaded fasteners with seal washers have complex shapes leading to poor moldability, increased costs, and poor workability, requiring high axial force for assembly and potentially detaching during transportation, with the second seal portion needing expansion over the bolt thread, complicating assembly and increasing axial force consumption.
Innovation Solution
A threaded fastener design featuring a bolt with a caulking portion integrated with the washer, an elastic seal member on the outer periphery with a protrusion and annular convex portions, and an underfill portion to reduce axial force and prevent separation, ensuring effective water sealing even with low axial force and during fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal washer with first and second seal portions connected via a through hole is used, then water sealing performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The seal function is divided into two independent parts: the first seal portion (seal ring) on the seal washer and the second seal portion (protrusion) on the bolt. These segmented seal portions are positioned at different locations and do not require complex connections, simplifying the overall structure while maintaining dual-side sealing capability.
Solution Approach 2:
The second seal portion is extracted from the seal washer and transferred to the bolt as a protrusion. This extraction eliminates the need for a through hole connecting two seal portions on the washer, simplifying the seal washer structure to a simple annular shape with better moldability while the bolt protrusion provides the second sealing function.
2Reliability
If the seal washer is fitted over the bolt after assembly, then sealing function is maintained, but assembling workability deteriorates
Solution Approach 1:
The protrusion is pre-formed on the bolt during bolt manufacturing, and the seal ring is pre-installed on the seal washer. This preliminary preparation of sealing components eliminates the need for complex assembly operations and allows for simple installation by directly fastening the bolt through the panel.
3Device complexity
If the second seal portion diameter is smaller than the shank portion diameter, then seal washer structure is simplified, but assembly time increases due to expansion requirement
Solution Approach 1:
The protrusion on the bolt is designed with a diameter that is larger than the seal ring inner diameter in the unfastened state, eliminating the need for expansion during assembly. This parameter change ensures that the protrusion can directly engage with the seal ring without requiring elastic deformation, thereby reducing assembly time while maintaining the simplified seal washer structure.
4Reliability
If separate seal portions are used on seal washer and bolt, then sealing coverage is improved, but axial force consumption increases
Solution Approach 1:
The seal ring is positioned only at the outer peripheral side of the seal washer where it is needed for sealing, rather than covering the entire washer surface. This localized sealing approach maintains adequate sealing coverage at critical interfaces while reducing the total contact area and corresponding axial force consumption.
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
The design enhances productivity, workability, and maintains water stop performance with reduced axial force consumption and prevents seal member detachment, ensuring reliable sealing even under water pressure and material wear.
Implementation Method 1
an elastic seal member on the outer periphery with a protrusion and annular convex portions
Implementation Method 2
The shank portion is provided with a caulking portion that is caulked and fixed to an entire opening portion peripheral edge of an inner periphery of the washer in a water stop state
Data Source
AI summary
A threaded fastener includes a bolt and a washer. The washer has a washer main body and a seal member provided at an outer peripheral side of the washer main body. The washer is caulked and fixed to a shank portion of the bolt in a water stop state, and the seal member is in contact with a fastened member in a water stop state, with a bearing surface of the washer main body held in contact with the fastened member. The seal member is provided on its outer periphery with a protrusion portion that protrudes outward beyond a radially outer end of a contact portion of the seal member with the washer in a no-load state. A back surface of the protrusion portion on the opposite side of the fastened member is an inclined surface.