Caterpillar's Earnings More Than Double  CHICAGO (Reuters) - Caterpillar Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=CAT.N target=/stocks/quickinfo/fullquote"&gt;CAT.N&lt;/A&gt; said on  Thursday quarterly earnings more than doubled on continued  strong demand for its heavy equipment.