Bellows Mechanical Seal Structure Against Irreversible Deformation
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Solution Overview
Problem
Mechanical seals with elastic bellows face challenges in maintaining sealing performance when the relative position between rotating and stationary rings changes due to temperature variations, leading to irreversible deformation and reduced sealing efficiency under fluid pressure.
Innovation Solution
A mechanical seal design featuring a bellows with a curved part between the outer and inner cylindrical parts, a case member covering the radial outer side of the curved part, and a holding member with protruding parts and groove parts to guide and restrict deformation, preventing torsional and radial displacement, and allowing for axial and radial deformation without irreversible changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mechanical seal unit is disposed on the outer peripheral side of the hollow shaft, then the sealing performance is improved, but the diameters and peripheral speeds at the contact seal surfaces are increased, making it difficult to apply to large devices and high-speed devices
Solution Approach 1:
The patent transitions from an outside-type mechanical seal to an inside-type mechanical seal, moving the seal unit from the outer peripheral side to the inner peripheral side of the hollow shaft. This dimensional repositioning reduces the diameter at the contact seal surfaces, thereby reducing peripheral speed and enabling application to large devices and high-speed devices while maintaining sealing performance
2Adaptability or versatility
If the elastic bellows is provided with a plurality of turn-back parts to absorb relative displacement, then the seal ring can follow the movement of the mating ring, but when fluid pressure acts from inside the bellows, the bellows deforms into a barrel shape and contacts the spring, hindering spring movement and reducing sealing performance
Solution Approach 1:
The patent applies preliminary anti-action by providing a guiding part that prevents the bellows from deforming into a barrel shape before the deformation can occur. The guiding part includes a groove part that engages with a protruding part, creating a constraint that counteracts the fluid pressure-induced deformation and prevents contact between the bellows and spring, thereby maintaining sealing performance
3Adaptability or versatility
If the elastic bellows is contracted in the axial direction due to temperature changes, then the relative position between rotating and stationary rings is adjusted, but the bellows cannot be restored to its original shape from its deformed state due to continuous fluid pressure, resulting in irreversible deformation
Solution Approach 1:
The guiding part with the groove and protruding part engagement provides preliminary anti-action by preventing radial protrusion of the bellows during axial contraction and extension. This constraint ensures the bellows maintains its original shape and can be fully restored after temperature-induced deformation, preventing irreversible deformation and maintaining long-term sealing performance
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 ensures reliable sealing performance by preventing irreversible deformation of the bellows, allowing it to follow the movement of the rotating ring without compromising the sealing integrity, even under significant temperature-induced displacement and fluid pressure.
Implementation Method 1
an elastic bellows 44 having a plurality of turn-back parts and made of rubber interposed therebetween, and is urged in an axial direction by a spring 45. In this way, since the elastic bellows 44 is capable of absorbing the relative displacement between the hollow shaft 5 and the carrier 37 by being provided with the plurality of turn-back parts
Implementation Method 2
the case member is provided with a cylindrical wall part that covers a radial-direction outer side of the curved part over an entire periphery
Data Source
AI summary
In an exemplary embodiment, a mechanical seal for sealing a fluid flowing outwardly radially from sliding surfaces S where a stationary ring 221 and a rotating ring 211 slide against each other, includes: a bellows 222 interposed between the stationary ring 221 and a stationary wall 226; a case member 223 for holding an outer cylindrical part 222c of the bellows 222 to the stationary ring 221; and a holding member 224 fitted to an inner cylindrical part 222a of the bellows 222, and having an axial length substantially equal to a length fitted to the inner cylindrical part 222a, wherein the bellows 222 has a curved part 222b between the outer cylindrical part 222c and the inner cylindrical part 222a, and the case member 223 is provided with a wall part 223a covering the entire periphery of the radial outer side of the curved part 222b.