Factory Pattern in Ruby/RoR

I've observed and repeated the factory design detailed at
http://www.artima.com/rubycs/articles/modular_apis_with_rubyP.html but
I would like something a little cleaner.

The details are such that I have 3 types of users: managers, employees
and customers.

I've abstracted the user security API such that
Manager < User
Employee < User
Customer < User
and the User class has all of the authentication methods such as
"set_password", "check_password", etc.

Now, for the authentication controller.

I have my route mapping such that /authenticate/:user_type/:action

I'd like to have something similar to the following as my authentication code:

class Authenticate < ActionController::Base

def authenticate
  @user = User.find(@params[:user_type], @params[:user][:email_address])
  if @user and @user.check_password(@params[:user][:password])
    render(:text => "Success")
  else
    render(:text => "Failure")
  end
end

end

Make sense? Any thoughts/ideas appreciated.

Thank you!
Dave Hawkins