Patent ID: 8590301

Claim:
A free piston Stirling machine including a piston reciprocatable in a piston cylinder open at one end to a working space, a heat accepting heat exchanger adjacent and opening into an expansion space portion of the working space, a heat rejecting heat exchanger adjacent and opening into a compression space portion of the working space and a regenerator extending between and in gas communication between the heat exchangers, the machine further comprising: (a) a thermal buffer tube extending from the expansion space and surrounded by the heat accepting heat exchanger and the regenerator; (b) a displacer cylinder extending from the thermal buffer tube to the compression space and surrounded by the heat rejecting heat exchanger; and (c) a displacer reciprocatable within the displacer cylinder and connected to a displacer rod, the displacer cylinder, the displacer, and the displacer rod having a size and being positioned to prevent excursion of any part of the displacer beyond the heat rejecting heat exchanger by more than 20% of the length of the regenerator during normal operation.