Innovative Tub Seal Eliminates Secondary Operations, Reduces Shaft Costs


The Situation
In appliance applications, especially in washing machines, a tub seal is adjacent to the washing drum and keeps water and debris in the tub from getting out. The seal, which is donut-shaped and consists of two parts, has a mating surface, which could be a tube or shaft – one rotates and one does not. An oil seal fits on the outside of the shaft in a static position, sealing whatever the shaft is being pressed into. In order to accomplish this, the appliance manufacturer needs to finish the surface of the shaft to reach a predetermined hardness by grinding; any defect or ding could act as a leak path on the seal’s rubber lip. Techniques of the finish can incur significant cost and require immense precision. Also, the shaft and seal have to line up perfectly with each other when being installed.

The Solution
Instead of the appliance manufacturer performing all of the finishing operations to make the spinning shaft have the correct surface, Trostel made a thin-walled cylindrical piece of steel, and the end user presses the seal onto the outside of their shaft. This eliminates secondary operations, and the Trostel seal can run against the intermediate surface without the possibility of defects or imperfections, limiting the chance of a leak path forming. Because of the reduction in secondary operations, the OEM was able to achieve significant cost savings on the shaft with less variation. With both pieces integrated into a single unit, the components can be installed together, reducing an assembly operation. The manufacturer also doesn’t have to work within the tight tolerances of having the two pieces meet perfectly, thereby saving extra installation costs and eliminating manufacturing assembly steps.