Stirling refrigerator with nonlinear braking spring

Claim 1

A Stirling refrigerator comprising: a cold-finger which contains a working gas and includes a displacer chamber and a gas spring chamber which is sealed off from said displacer chamber; a displacer which is disposed slidably inside said displacer chamber so as to be able to reciprocate therein and perform a stroke and which divides said displacer chamber into a compression chamber and an expansion chamber, said displacer having a piston element formed thereon which extends into said gas spring chamber; a compressor which is connected to said compression chamber and periodically varies the pressure of the working gas inside said compression chamber; and a spring which is connected between said displacer and said cold-finger so as to be deformed as said displacer reciprocates within said cold-finger, said spring having a neutral position which it assumes when said displacer is between the ends of its stroke, a spring constant of said spring being constant within a predetermined displacement from said neutral position, and increasing outside said predetermined displacement, the spring constant of said spring being greater when said displacer is near either end of its stroke than when said spring is in its neutral position.