A driving system (13) comprises a housing (10) having spherical hollow space (11), a rotatable main shaft (14), a driving means (16) and a piston construction (15). The piston construction (15) is rockable about a first rocking axis (15a) in a rectilinear motion backwards and forwards relative to a stationary wall portion (12). The driving means (16) is pivotally mounted in the main shaft (14) about a pivotable axis (16b) which forms an acute angle with the rotatable axis (14a) of the main shaft (14) and is rockably mounted in the piston construction (15) about a second rocking axis (16a), which extends at right angles to the first rocking axis (15a). The first and second rocking axis (15a, 16a) cross the rotational axis (14a) of the main shaft (14) at a common crossing point (11c) centrally in the spherical hollow space (11).