Joseph Pirschl, co-founder of the North Huntingdon-based Serro Travel Trailer Co., loved working with anyone who appreciated a good joke and a firm handshake. In fact, he loved that part of his job so much that he would deliver his company's iconic teardrop-shaped campers to dealers across the country himself, even as he transitioned into retirement. “He was a people person,” said his son, Gary Pirschl. “He loved the relationships with people.” Pirschl, 89, of Hempfield died