Frage Rigging for multiple objects?

[wuschi]

Hey, 
I was following a tutorial on YouTube on how to model a cup robot thing and now i want to rig it for unity but because the robot consists ob multiple objects it looks pretty weird when i try rigging it. If I move a Bone it looks something like this:

Any ideas on how to fix this?

Heres the link to the video: https://www.youtube.com/watch?v=nsTjnQ067sw

[wuschi]

Heres the blend file if this is helpfull