Nikola Tesla U.S. Patent 514,169 - Reciprocating Engine Patent Wrapper Page 13

58 immediate part. This is known to be true in all cases where the force which tends to bring the spring or mo va ble system into a given position is proportionate to the displacement. In carrying out my invention and for securing the objects in general terms stated above, I employ the energy of steam or gas under pressure, acting through proper mec hanism, to maintain in oscillation a pist on, and, taking advantage of the law above stated, I connect with said piston, or cause to act upon it, a spring, un der such con ditions as to automatically regulate the period of the vibration, so that the alternate impulses of the power impelled piston, and the natural vibrat ions of the spring shall always correspond in direct ion and coincide in time. while, in the practice of the invention I may enploy any kind of spring or elastic body of which the la or principle of operation above defined holds true, I prefer to use an air spring, or generally speaking a confined body or cushion of an elastic fluid, as the mechanical difficulties in the use of ordinary or metallic springs are serious, owing mainly, to their tendency to break. Moreover, instead of permitting the piston to impinge directly upon such cushions within its own cylinder, I prefer, in order to avoid the influence of the varying pressure of the steam or gas that acts upon the piston and which might disturb the relations necessary for the rain-3