Co-Molded Washing Machine Bushing With Pressure-Equalizing Ducts
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Solution Overview
Problem
Existing tubular bushings in washing machines face performance issues due to temperature and humidity gradients, which can deteriorate the sealing effectiveness of the sealing element, leading to potential detachment of sealing lips from the drive shaft and compromised sealing performance.
Innovation Solution
A tubular bushing design that includes a co-molded plastic sleeve with a cylindrical seat and annular edge, a sealing element with radially extending lips, and ducts to equalize pressure and temperature gradients, ensuring the sealing element operates under consistent conditions and maintaining effective sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sealing element is positioned in the tubular bushing subject to temperature and humidity gradients, then the sealing element can seal the drive shaft, but the sealing performance deteriorates due to inconsistent working conditions
Solution Approach 1:
The tubular bushing is divided into distinct functional zones: a first portion exposed to the humid environment inside the tub, a second portion extending outside the tub, and an intermediate transition portion connecting them. This segmentation allows each zone to experience different environmental conditions, with the transition portion gradually equalizing temperature and humidity gradients to protect the sealing element.
Solution Approach 2:
The intermediate transition portion acts as an intermediary zone between the humid interior and dry exterior environments. This transition portion mediates the temperature and humidity gradients, creating a gradual transition rather than an abrupt change, thereby protecting the sealing element from extreme gradient effects while maintaining sealing effectiveness.
2Productivity
If the tubular bushing is co-molded with the tub to reduce production time, then manufacturing efficiency improves, but the sealing element is exposed to remarkable temperature and humidity gradients
Solution Approach 1:
The co-molded tubular bushing is designed with segmented functional zones including an intermediate transition portion that specifically addresses the sealing element's environmental exposure. This segmentation allows the bushing to be produced as a single integrated component (maintaining productivity) while creating protected zones for the sealing element (maintaining reliability).
Solution Approach 2:
Different portions of the tubular bushing are designed with different local qualities: the first portion is optimized for humid environment exposure, the second portion for dry environment, and the intermediate transition portion for gradient equalization. This local quality differentiation allows the sealing element to be protected from extreme gradients while maintaining overall manufacturing efficiency through co-molding.
3Reliability
If the sealing lips are positioned to contact the drive shaft for sealing, then sealing function is achieved, but the lips may detach under temperature and humidity gradients
Solution Approach 1:
The intermediate transition portion serves as a protective intermediary that shields the sealing element and its lips from extreme temperature and humidity gradients. By creating a gradual environmental transition zone, the sealing lips maintain stable attachment to the drive shaft while still performing their sealing function effectively.
Solution Approach 2:
The intermediate transition portion provides beforehand cushioning by pre-equilibrating temperature and humidity conditions before they reach the sealing element. This protective cushioning effect prevents sudden thermal or humidity shocks that could cause sealing lip detachment, thereby maintaining both sealing effectiveness and structural stability.
Data Source
Figure 1~2
AI summary
Tubular bushing (10) co-moldable with tubs of washing machines, the tubular bushing (10) being located between a humid side (13) and a dry side (14) of the washing machine, crossed by a drive shaft (15) extending along a central axis (A) and provided with two rolling bearings (20, 30), arranged along the axis (A); a spacer (40) interposed between the two bearings (20, 30); a sealing element (53) arranged axially alongside a first bearing (30) close to the humid side (30); and a containing sleeve (50) which is co-molded around the two bearings (20, 30) and the spacer (40); the sealing element (53) and the first bearing (30) bound and axially enclose an annular chamber (56), which is further closed in the radial direction by the drive shaft (15) and is in fluid connection with the external environment by means of two ducts (200, 201) extending directly through the containing sleeve (50), eliminating any pressure and/or temperature gradient between the annular chamber (56) and the external environment.