Private equity firm Monomoy Capital Partners LP has acquired Middlebury-based Pilgrim International Inc. and plans to combine it with another recreational vehicle maker it owns, Washington-based Western Recreational Vehicles Inc. The merged company will be headquartered in Middlebury. No impact to the 750 workers the two companies employ is expected. New York-based Monomoy Capital did not disclose financial terms. The deal is expected to close this month.