Rails 3 autoload

I have a class ConstData:

class ConstData

  US_CITIES = ['miami', 'new york']

  EUROPERN_CITIES = ['madrid', 'london']

end

Its stored under /lib/const_data.rb

The idea is that inside a model, controller or view I can do:

ConstData::US_CITIES to get the US_CITIES etc

Rails should load this class automatically, I got this from: http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/662abfd1df9b2612?hl=en

However this does not work. Can anyone explain me how to accomplish this ?