Welded Bellows Mechanical Seal for High-Speed Liquid Tightness
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Solution Overview
Problem
Outside-type mechanical sealing devices face challenges in maintaining high seal tightness at increased rotation speeds and liquid pressures while being compact in both axial and radial dimensions, as existing solutions like springs either increase size or compromise seal integrity.
Innovation Solution
The use of a bellows as an elastic member that presses the sealing ring, providing uniform circumferential pressure and preventing liquid leakage through its entire circumference, allowing for a smaller device size without increasing axial or radial dimensions, and additional sealing members to block any leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed is increased to improve productivity, then the liquid pressure on the sliding faces increases, but the seal tightness is lowered
Solution Approach 1:
The patent changes the physical state and properties of the sealing materials by selecting specific material combinations (e.g., carbon graphite vs. stainless steel, or ceramic vs. metal) to maintain seal tightness under high rotation speeds and liquid pressures. The material parameters are optimized to resist centrifugal force effects and maintain contact pressure.
Solution Approach 2:
The patent employs a spring mechanism that dynamically adjusts the contact pressure between sealing rings based on operating conditions. The spring force compensates for variations in liquid pressure and rotation speed, maintaining optimal seal tightness across different operational states.
2Reliability
If the length of the spring in the axial direction is increased to increase the pressing force, then the seal tightness is improved, but it becomes difficult to reduce the size of the mechanical sealing device in the axial direction
Solution Approach 1:
The patent changes the spring constant and material properties to achieve higher pressing forces within a compact axial space. By selecting springs with optimized physical parameters (higher elastic modulus, different coil density), sufficient sealing force is generated without increasing axial dimension.
Solution Approach 2:
The patent uses composite sealing ring structures combining materials with different properties (e.g., carbon graphite facing with metal backing) to enhance sealing performance without requiring increased spring length, as the composite structure itself contributes to seal integrity.
3Reliability
If the number of springs is increased to increase the pressing force, then the seal tightness is improved, but it requires the springs to be mounted at a position away from the center, making it difficult to reduce the size in the radial direction
Solution Approach 1:
The patent merges multiple spring elements into a single integrated spring mechanism or combines the spring function with other structural components. This consolidation provides the necessary pressing force while maintaining a compact radial footprint, avoiding the need to distribute multiple springs outward from the center.
Solution Approach 2:
The patent designs the spring mechanism to serve multiple functions simultaneously: providing sealing force, supporting the sealing ring structure, and compensating for misalignment. This multi-functionality reduces the need for additional components that would increase radial size.
4Reliability
If the size of the spring in the radial direction is increased to increase the pressing force, then the seal tightness is improved, but it is difficult to reduce the size of the mechanical sealing device in the radial direction
Solution Approach 1:
The patent optimizes the spring's physical parameters including wire diameter, coil diameter, and active coil count to generate sufficient pressing force within a minimal radial envelope. By adjusting these parameters, the spring achieves high force output without radial expansion.
Solution Approach 2:
The patent replaces traditional mechanical spring systems with alternative mechanisms such as elastomeric elements, Belleville washers, or pre-loaded structural designs that provide equivalent or superior sealing force with reduced radial dimensions.
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 mechanical sealing device achieves high seal tightness and prevents liquid leakage even at high rotation speeds and pressures, maintaining compact dimensions and durability with minimal parts and a simple configuration.
Implementation Method 1
a bellows 15 which presses the sealing ring 13 in the axial direction
Implementation Method 2
the contact faces of the sealing ring and the mating ring serves as sliding faces. The sliding faces function as the primary seal that prevents the fluid from leaking out
Implementation Method 3
a spring mechanism that urges and presses the sealing ring toward the mating ring
Implementation Method 4
In the outside-type mechanical sealing device, unlike the inside-type mechanical sealing device, centrifugal force acts on the liquid that is leaking out
Data Source
Figure 1
Figure 2
AI summary
A mechanical sealing device according to an embodiment of the present invention includes: a sealing ring (13) attached to a protrusion (11a) protruding from a housing (11); a mating ring (23) attached to an end portion of a rotary shaft (21); a welded bellows provided around the protrusion (11a) and located between the housing (11) and the sealing ring (13). The welded bellows (15) presses the sealing ring (13) in an axial direction to cause the sealing ring (13) to be in contact with the mating ring (23), thereby ensuring high pressure force, and in particular, uniform pressure force along its entire circumference, so as to achieve high liquid tightness, while maintaining the sizes in axial and radial directions small. Furthermore, the welded bellows (15) works as a sealing member of blocking a liquid leaked out through the O-ring (14), thereby achieving assured liquid tightness. Accordingly, an outside-type mechanical sealing device can be provided which has a compact size, and is capable of ensuring high liquid tightness in response to a high rotation speed and a high liquid pressure.