Co-Moldable Washing Machine Hose for Stable Bearing Retention
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Solution Overview
Problem
The existing co-moldable hoses with washing machine tubs face issues due to thermal expansion differences between metallic tubular bodies and bearings, leading to a loose coupling and potential bearing displacement or ejection during molding, especially when using materials like aluminum and steel.
Innovation Solution
Incorporating plastic covering and blocking means co-molded with the bearings and tubular body, which fill radial gaps and provide shoulders to axially block the bearings, compensating for differential expansion and preventing movement, thus eliminating the need for surface machining and ensuring correct interference fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tubular body and bearings are co-molded together to simplify assembly, then assembly operations are facilitated, but the bearing may move or exit the housing during molding due to thermal expansion differences
Solution Approach 1:
The patent applies preliminary action by pre-positioning the bearing within the housing before the co-molding process, and by designing the housing with specific geometric features (shoulders, tapered surfaces) that preemptively prevent bearing movement during molding. The housing geometry is prepared in advance to compensate for thermal expansion effects that will occur during the molding process.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a specialized housing structure that acts as a mediator between the bearing and the molding process. The housing includes intermediate geometric features (shoulders, tapered surfaces, relief zones) that facilitate the bearing's integration into the plastic tub while preventing displacement, thus mediating between the conflicting requirements of ease of manufacture and bearing stability.
2Manufacturing precision
If the housings are machined beforehand by grinding to ensure correct interference fit, then the interference fit between bearings and housings is guaranteed, but the production process becomes more complex and costly
Solution Approach 1:
The patent applies self-service by designing the housing geometry to automatically ensure correct interference fit without requiring external machining operations. The housing's inherent geometric features (shoulders, tapered surfaces, relief zones) self-regulate the bearing position and fit during the co-molding process, eliminating the need for separate grinding or machining steps.
Solution Approach 2:
The patent utilizes parameter changes by designing the housing with specific geometric parameters (shoulder positions, tapered surface angles, relief zone dimensions) that are optimized to compensate for thermal expansion differences between materials. These parameter changes allow the housing to maintain correct interference fit under varying temperature and pressure conditions during molding, without requiring post-processing machining.
3Weight of moving object
If aluminum is used for the tubular body instead of other metals, then weight is reduced, but the differential thermal expansion with steel bearings causes the interference fit to be cancelled
Solution Approach 1:
The patent directly addresses thermal expansion by designing the housing geometry to compensate for the differential thermal expansion between aluminum (tubular body) and steel (bearings). The housing includes expansion compensation features such as relief zones and adjustable shoulders that accommodate the different expansion rates of the two materials during the molding process, maintaining the interference fit despite the weight advantage of using aluminum.
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 solution effectively prevents bearing displacement and ensures a stable molding process by compensating for thermal expansion differences, maintaining a secure fit between bearings and housings, and simplifies production by eliminating the need for surface grinding.
Implementation Method 1
the thermal expansion coefficient of the metallic material which constitutes the tubular body is different from the one of the metallic material which constitutes the bearings, and as the actual molding conditions involve high levels of both temperature and injection pressure, it can happen, during the molding of the tub over the hose, that the coupling between the bearings and the relative housings becomes loose
Data Source
Figure 1
Figure 2~3
AI summary
Co-moldable hose (1) with washing machine tubs presenting a longitudinal axis (A) and provided with two bearings (C3, C4) which are arranged along the axis (A) at a determined distance from one another, and with a tubular metallic body (2) which extends along the axis (A) and which is in turn provided, for each bearing (C3, C4), with a housing (3, 4) for each relative bearing (C3, C4) which is delimited towards the axis (A) by a respective inner radial surface (53a, 54a); two covering and blocking bodies (83, 84) also being co-molded with the bearings (C3, C4) and with the tubular body (2) inside each housing (3, 4) in a position which is radially intermediate between a relative radial surface (53a, 54a) and a relative bearing (C3, C4) in order to internally cover the housing (3, 4) itself and to block the relative bearing (C3, C4) inside the relative housing (3, 4).