Pittsburg -- The maker of Zippo lighters is turning up the heat on knockoffs of the distinctively shaped - and trademarked - lighters.

For the first time since obtaining trademark registration of the slightly rounded rectangular shape four years ago, Zippo Manufacturing Co. has filed a complaint with the US International Trade Commission to stop the manufacture and sale of knockoffs, said Jeff Duke, the company's attorney.

Duke said knockoffs persist, despite the trademark.

"It has declined, but it has not declined as significantly or as fast as we wanted to, which is why we brought the ITC action," Duke said Wednesday.

By even a conservative estimate, knockoffs consume 30 percent of Zippo's business, he said.

"It's a significant issue for us, it really is. Zippo is a small company in the overall context of global companies ... We can very clearly identify a loss of jobs," he said.

The company employs about 800 people in McKean County, a rural area along the New York border. Duke estimates it has lost about 150 jobs to "shape-infringing" lighters.

Zippo, founded in 1932, makes between 12 million and 14 million lighters a year. Several million fans collect the thousands of designs it has offered over the years.

The complaint, filed in May, seeks to bar importation of knockoffs. Four Chinese companies and three US distributors are listed as respondents, but Duke said there are "dozens upon dozens of both."

Duke said the settlement gives distributors some time to sell their existing stock.

In the meantime, the International Trade Commission is investigating Zippo's complaint. An evidentiary hearing before an administrative law judge is scheduled for February 5, but Duke said he hopes the complaint can be resolved before then.

The company has also been working with China on the problem.

"We're not trying to block competition per se, we're trying to stop companies from using our name and our trademark shape," Duke said.