Hot-gas reciprocating machine

A hot-gas reciprocating machine comprising first and second spaces of variable volume which communicate with each other through a regenerator, and first and second pistons for varying the volumes of the first and second spaces respectively, the first and second pistons being connected to parallel first and second crank shafts respectively and being movable with an adjustable phase difference, wherein each of the crank shafts carries counterweight whose centre of gravity is situated in the plane containing the axis of the respective crank shaft and the axis of the crank pin through which the respective piston is connected to that crank, and of which counterweight the centrifugal force occurring during operation of the machine corresponds to half the force produced by the reciprocating parts coupled to the relevant crank shaft, wherein on the side of the first crank shaft which is remote from the second crank shaft there is provided a first auxiliary shaft which extends parallel to the first crank shaft and which is coupled thereto in such a manner that the auxiliary shaft rotates in the opposite direction to and at the same speed as the first crank shaft, the first auxiliary shaft carrying at least one counterweight whose centre of gravity is so situated that during operation the horizontal and vertical components of the centrifugal force of the latter counterweight always act respectively in the opposite direction to and the same direction as the corresponding components of the centrifugal force of the counterweight on the first crank shaft, and wherein on the side of the second crank shaft which is remote from the first crank shaft there is provided a second auxiliary shaft which extends parallel to the second crank shaft and which is coupled thereto in such a manner that the second auxiliary shaft rotates in the opposite direction to and at the same speed as the second crank shaft, the second auxiliary shaft carrying at least one counterweight whose centre of gravity is so situated that during operation the horizontal and vertical components of the centrifugal force of the latter counterweight always act respectively in the opposite direction to and the same direction as the corresponding components of the centrifugal force of the counterweight on the second crank shaft.