Nikola Tesla U.S. Patent 517,900 - Steam Engine Patent Wrapper Page 7

T T 1 J of the spring and its own inertia or that of the moving sy stem of which it forms an immediate part. 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. This is In utilizing this principle for the purpose of pro-u ducing reciprocating movement of a constant nt period, I employ the energy of steam or gas under pressure, acting through proper mechanism, to maintain in oscillation a piston, and connect with or cause to act upon such piston a spring, preferably, an air spring, under such conditions as to automatically regulate the period of the vibration, so that the alte mate impulses of the power impelled piston and the natural vibrations of the spring shall always correspond in direction and coincide in time. In In such an apparatus it being essential that the inertia of the moving system and the rigidity of the spring should bear certain definite relations, it is obvious that the practicable amount of work performed by the engine, when this involves the overcoming of inertia is a limitation to the applicability of the engine. I therefore propose, in order to secure all the advantages of such performances as this form of engine is capable of, to utilize it as the means of controlling the admission and exhaust of steam or ges under pressure in other engines generally, but more especially those forms of engine -279