Typically, you just need a module cgi, then use CGI::escape(str).
require 'cgi'
require 'open-uri'
escaped_page = CGI::escape("Thor_Industries,_Inc.")
url = "http://en.wikipedia.org/wiki/#{escaped_page}"
f = open(url)
However, this does not seem to work for your specific instance and still returns 403. I will leave this here for reference, regardless.
: , , . , , , "" (, , ), . ( Net::HTTP), :
User-Agent IP .
:
open("http://en.wikipedia.org/wiki/Thor_Industries,_Inc.",
"User-Agent" => "Ruby/#{RUBY_VERSION}")