In the following year, October 25, 1781, Watt patented five devices by which he obtained the rotary motion of the engine-shaft without the use of a crank. One of these was the arrangement shown in Fig. 27, and known as the "sun-and-planet" wheels. The crank-shaft carries a gear-wheel, which is engaged by another securely fixed upon the end of the connecting-rod. As the latter is compelled to revolve about the axis of the shaft by a tie which confines the connecting-rod end at a fixed distance from the shaft, the shaft-gear is compelled to revolve, and the shaft with it. Any desired velocity-ratio was secured by giving the two gears the necessary relative diameters. A fly-wheel was used to regulate the motion of the shaft.[39] Boulton & Watt used the sun-and-planet device on many engines, but finally adopted the crank, when the expiration of the patent held by Matthew Wasborough, and which had earlier date than Watt's patent of 1781, permitted them. Watt had proposed the use of a crank, it is said, as early as 1771, but Wasborough anticipated him in securing the patent. Watt had made a model of an engine with a crank and fly-wheel, and he has stated that one of his workmen, who had seen the model, described it to Wasborough, thus enabling the latter to deprive Watt of his own property. The proceeding excited great indignation on the part of Watt; but no legal action was taken by Boulton & Watt, as the overthrow of the patent was thought likely to do them injury by permitting its use by more active competitors and more ingenious men. [39] For the privilege of using the fly-wheel to regulate the motion of the engine, Boulton & Watt paid a royalty to Matthew Wasborough, who had patented it, and who held also the patent for its combination with a crank, as invented by Pickard and Steed. The next patent issued to Watt was an exceedingly important one, and of especial interest in a history of the development of the economical application of steam. This patent included: 1. The expansion of steam, and six methods of applying the principle and of equalizing the expansive power. 2. The double-acting steam-engine, in which the steam acts on each side of the piston alternately, the opposite side being in communication with the condenser. 3. The double or coupled steam-engine--two engines capable of working together, or independently, as may be desired. 4. The use of a rack on the piston-rod, working into a sector on the end of the beam, thus securing a perfect rectilinear motion of the rod. 5. A rotary engine, or "steam-wheel."