Middle Chassis House Function

[magenri]

Hello all, new to the forums but not the site. I've gotten some great information off the forums and I hope you all can help me out now.
I have a Blackberry Storm 9530, bought off ebay, broken digitizer included but knew about it at the purchase. When it arrived it worked for a little while but it started to break down on me. The screen would shut off and i would need to twist the whole phone and it would come back on but only for a short period of time. So i stopped using it until recently when i decided to fix it. I bought a new digitizer, and middle chassis housing. My question is: what is the function of the middle chassis housing? I figured it couldn't hurt to buy a new one to repair my phone, maybe it could be part of the reason the screen wasn't working.

Sorry for the story, just thought it couldn't hurt to have the back story on my phone so it could be easier to analyze my problem and find a solution.
Thanks for your help!