U.S. Chamber attacks Labor Act at Capitol. Washington, D.C., June 26. B.C. Heacock, President of the Caterpillar Tractor Co. of Peoria, Ill., and Chairman of the U.S. Chamber of Commerce's Committee on Manufacture, told a Senate and Education and Labor Committee today that the chamber favored amendments to the Labor Act to accomplish these purposes--to preserve the right of freedom speech, to grant the employer the right to petition the NLRB for a determination of the representatives selected by his employees for collective bargaining to prohibit coercion of employees from any course, and to repeal the closed-shop proviso'