preview convert

I have no trouble converting everyday images with the built in preview convert action in automator, but when I try to convert psd files (photoshop files) to jpeg through automator it doesn’t work. I often view psd files in preview when I don’t feel like starting photoshop so I know it’s quite capable of opening them. I have even saved those psd files as different files one by one, but I often do lots of photoshop files then like to convert them all at once to upload on imageshack or a similar website…

So basically what I what I want to do is convert psd files to jpeg.