| 摘要 |
This invention relates to an improved structure for a wheel cylinder for use in a drum brake assembly having a pair of brake shoes which are adapted to be urged into frictional engagement with a brake drum. The wheel cylinder includes a pair of opposed piston assemblies each having a piston body formed from a plastic material and a piston insert formed from metal. In accordance with one embodiment of this invention, the piston insert is molded in situ with the piston body and the piston insert includes a radially outwardly extending first flange and a radially outwardly extending second flange. The first flange defines a first flange outer diameter, and the second flange defines a second flange outer diameter which is less than the first flange outer diameter. The first flange of the piston insert is operative to distribute the pressure across the associated outer face of the piston body during brake application, and the second flange of the piston insert is operative to assist in securing the piston insert to the piston body during the molding process.
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