US Patent No. 1,463,966, granted Aug. 7, 1923 to Jonas Northrop of Hopedale, Massachusetts, assigned to the Hopedale Manufacturing Company. It describes a let-off and take-back mechanism for looms that keeps warp tension uniform. A whip roll senses changes in tension and moves a shield, which lets either a let-off pawl or a take-back pawl engage ratchet wheels that turn the warp beam through worm gearing. The document has three sheets of drawings (Figs. 1-6) followed by the specification and two claims.