Tell the people running the scanner that the funny box is a milking machine - otherwise they will ask, but there won't be any problems.
There are no liquid limits on domestic flights, and the limit on international flights is that they must be in no more than 100 ml bottles and fit in a zip-lock bag - so if you did have to go international then you could actually take some milk home, but you'd need some smaller bottles (like the newborn ones).
Good luck!