A device for mounting and demounting a hollow needle on and from a Phaco instrument handpiece, comprising - a manually operable housing, - a rotary shaft rotatably mounted in the housing, the rotary shaft comprising a plug-on end extending outwards from an opening of the housing for plugging on the hollow needle, the plug-on end comprising internal engaging projections for engaging with recesses in the outside of the hollow needle for the purpose of rotating the hollow needle when manually rotating the housing, - a torque limit and non-return coupling having a contact surface arranged at the rotary shaft as a first coupling surface, and - a driver element arranged coaxially to the rotary shaft in the housing, being coupled to the housing and having a contact surface as a second coupling surface of the torque limit and non-return coupling, characterized in that - the two coupling surfaces (36, 38) rest against each other by being spring-loaded against each other, - the one coupling surface has at least one coupling release projection and the other coupling surface has at least one coupling recess being complementary to the form of the coupling release projection, - the one coupling surface has at least one non-return projection and the other coupling surface has at least one non-return recess, - the at least one non-return recess - viewed in circumferential direction of a circular line concentrically to the axis of the rotary shaft - has an extension being larger, in particular more than twice larger than the extension of the non-return projection in circumferential direction of the circular line, - the at least one non-return projection rests against one of the two ends of the non-return recess arranged as viewed in the circumferential direction of the circular line when the at least one coupling release projection is immersed in the at least one coupling recess, - the at least one non-return projection, when viewed in axial extension of the rotary shaft, has a height which is smaller than the height of the at least one coupling release projection, and - the at least one non-return projection is entirely moved out of the at least one non-return recess when the at least one coupling release projection is moved out of the at least one coupling recess, and moved above or on the coupling surface comprising the non-return recess, until the at least one coupling release projection is again immersed in the at least one coupling recess when the housing continues to rotate. - a manually operable housing, - a rotary shaft rotatably mounted in the housing, the rotary shaft comprising a plug-on end extending outwards from an opening of the housing for plugging on the hollow needle, the plug-on end comprising internal engaging projections for engaging with recesses in the outside of the hollow needle for the purpose of rotating the hollow needle when manually rotating the housing, - a torque limit and non-return coupling having a contact surface arranged at the rotary shaft as a first coupling surface, and - a driver element arranged coaxially to the rotary shaft in the housing, being coupled to the housing and having a contact surface as a second coupling surface of the torque limit and non-return coupling, characterized in that - the two coupling surfaces (36, 38) rest against each other by being spring-loaded against each other, - the one coupling surface has at least one coupling release projection and the other coupling surface has at least one coupling recess being complementary to the form of the coupling release projection, - the one coupling surface has at least one non-return projection and the other coupling surface has at least one non-return recess, - the at least one non-return recess - viewed in circumferential direction of a circular line concentrically to the axis of the rotary shaft - has an extension being larger, in particular more than twice larger than the extension of the non-return projection in circumferential direction of the circular line, - the at least one non-return projection rests against one of the two ends of the non-return recess arranged as viewed in the circumferential direction of the circular line when the at least one coupling release projection is immersed in the at least one coupling recess, - the at least one non-return projection, when viewed in axial extension of the rotary shaft, has a height which is smaller than the height of the at least one coupling release projection, and - the at least one non-return projection is entirely moved out of the at least one non-return recess when the at least one coupling release projection is moved out of the at least one coupling recess, and moved above or on the coupling surface comprising the non-return recess, until the at least one coupling release projection is again immersed in the at least one coupling recess when the housing continues to rotate.