Nikola Tesla U.S. Patent 514,169 - Reciprocating Engine Patent Wrapper Page 24

3 J } T J used as a cigar lighter. In applicant's device the compression of the air at one end of the cylinder may be easily such as to give rise to a very high temperature. The metal cylinder being a good conductor of heat takes up a portion of this heat at every stroke and soon bec ones highly heated. The expansion of the air is of caurse attended by a reduction of temperature, but the heat which has gone into and is being carried off by the cylinder is not recovered. If we could imagine a cylinder and plunger incapavle of absorbing any heat, and containing a perfectly elastic gas and further assume that there is no leakage of the gas through any contracted spaces, or heat lost by friction, we would have an appare tus in which the heat of compression would be exactly equalized by the calá of expansion, but such an apparatus is only theoretically possible. With regard to the claims rejected, it is probable. them that we have not made sufficien tly clear, but an explanation may remove the objection. The claims enumerate as elements, a cylinder, a piston and a spring acting on the latter. These elements in themselves are not claimed broadly,, but only when they bear certain relations to one another, In other words when the relations are such that the moving system follows the law of isochronous movement. These relations are not fixed, but relative. Any piston and any spring may be used provided the forces. which tend to bring pist on to a given position are pro-369