JQuery :: Simple Accordion Menu Using This HTML Structure

I want to accomplish a nice and simple accordion menu using this HTML structure:

Code HTML4Strict:

And I'm using this JQuery code:

Code JavaScript:

This basically works, but when I click a particular menu item to expand it's submenu items, it basically hides all submenus items, even the active ones, but whant I need is the particular clicked submenu items to stay expanded. I guess this can be accomplished by a simple if statement or so.