Manitowoc (NYSE: MTW) simply refuses to slow down. After a strong quarter that capped off 2007, the company, which makes a host of products including cranes, ships, ice cube makers, and refrigeration and beverage machines, took its earnings up another 60% year over year in the quarter ended in March.

For the quarter, Wisconsin-based Manitowoc earned $102.7 million, or $0.78 a share. Those figures compared to year-ago numbers of $64.1 million, or $0.50 per share. Revenues increased to $1.08 billion, a 25% increase from the $862.1 million in the first quarter of 2007.

As Glen Tellock, Manitowoc's CEO, noted, all the company's businesses turned in improved performances. However, he singled out for particular discussion the crane business, which is benefiting from "global demand for construction equipment." At the same time, Manitowoc Marine churned out stronger results on the basis of a blend of government, commercial, and repair business. But it was cranes that hoisted the company's results most noticeably, generating a nearly 30% increase in sales.

Manitowoc runs in a league with a group of industrial or construction equipment companies -- including its big Midwestern brother Caterpillar (NYSE: CAT), Illinois Tool Works (NYSE: ITW), and Ingersoll-Rand (NYSE: IR), all of which have quietly had a good run as of late. Along with perhaps not being as scintillating as, perhaps, a Google or a Crocs, the common bond within the group is that they've all quietly ginned out solid quarters. And they've done so despite a slowing in many parts of the U.S. economy.

As to Manitowoc specifically, in addition to the steady growth of its crane business, I'm attracted to its low PEG ratio -- indicating that its growth prospects appear to outdo its current P/E -- its solid return on equity, and its unusually robust balance sheet. That's a combination that, especially amid current market conditions, should generate attention from investing Fools for whom the word "sound" is gaining new meaning.

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Somewhat sadly, to his reckoning, Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does welcome your questions or comments. The Fool has a disclosure policy.