Abstract: A motor-compressor comprising a vibration motor (1) having a rotationally vibrating drive shaft (4) and a compressor (2) having at least one piston (10) which is linearly reciprocated by the motor shaft (4) is suspended in the housing (14) by means of springs (15) so that the points of attachment (17) of the springs are coplanar with and as close as possible to the axis (16) of the rotation, to which the motor- compressor is subjected in operation. This counteracts the imbalance forces to a maximum extent and minimizes the dynamic forces on the housing.

Abstract: A control device (30) for controlling the supply of power to the coils (16A, 16B) of a drive motor (3) for a compressor unit of the resonant-piston type (1). The control device comprises a power-supply circuit (44) for energizing the motor coils from a direct voltage source (45), means (46, 47, 48; 46, 60) for determining a measure (P, .phi.), which indicates whether the power consumption of the motor as a function of the frequency of the energizing current is at least approximately maximal, and means (40, 42, 43; 61, 42, 43) for adjusting the frequency of the energizing current, depending on the derived measure (P, .phi.), to a value for which said measure indicates that the power consumption of the motor (3) is maximal.

Abstract: The invention relates to a disposable syringe comprising a barrel in which a piston is provided and to which a needle is or can be connected to the front, a stopper being present in the barrel between piston and needle or needle connection means. The inner wall of the barrel is locally deformed between stopper and needle or needle connection so that at the area of the deformation injection liquid can reach the cannula past the stopper and during nurse-aspiration the stopper is held, in which body fluid can reach the part of the barrel present behind the stopper.