Operating mechanism for a window covering comprising: - a stationary carrying structure which can be fitted to the fixed surroundings, - a drive axle which is preferably at least partly accommodated in the carrying structure, - a contact body which is coupled to the drive axle so as to be movable in longitudinal direction of the drive axle, - a winding reel which is driven by the drive axle and onto said winding reel at least a part of the window covering can be wound, - a drive wheel which is at least partly accommodated in a holding space enclosed between the contact body and an engagement wall of the carrying structure which is situated opposite the contact body, wherein the contact body and the engagement wall of the carrying structure engage with opposite sides of the drive wheel, and wherein the drive wheel is releasably accommodated in the holding space, and wherein the contact body is configured to be moved in a direction facing away from the engagement wall of the carrying structure in order to be able to remove the drive wheel from the holding space, - at least one pressure element for forcing the contact body in the direction of the engagement wall of the carrying structure in the longitudinal direction of the drive axle, and - characterized by at least one retention element (10a, 10b) for limiting the movement of the contact body in the direction of the engagement wall in such a way that, if the drive wheel is removed from the holding space, the contact body remains situated at a distance from the engagement wall of the carrying structure, wherein the at least one retention element (10a, 10b) is configured to cooperate with at least one stop face for limiting the maximum movement of the contact body in the direction of the engagement wall of the carrying structure. - a stationary carrying structure which can be fitted to the fixed surroundings, - a drive axle which is preferably at least partly accommodated in the carrying structure, - a contact body which is coupled to the drive axle so as to be movable in longitudinal direction of the drive axle, - a winding reel which is driven by the drive axle and onto said winding reel at least a part of the window covering can be wound, - a drive wheel which is at least partly accommodated in a holding space enclosed between the contact body and an engagement wall of the carrying structure which is situated opposite the contact body, wherein the contact body and the engagement wall of the carrying structure engage with opposite sides of the drive wheel, and wherein the drive wheel is releasably accommodated in the holding space, and wherein the contact body is configured to be moved in a direction facing away from the engagement wall of the carrying structure in order to be able to remove the drive wheel from the holding space, - at least one pressure element for forcing the contact body in the direction of the engagement wall of the carrying structure in the longitudinal direction of the drive axle, and - characterized by at least one retention element (10a, 10b) for limiting the movement of the contact body in the direction of the engagement wall in such a way that, if the drive wheel is removed from the holding space, the contact body remains situated at a distance from the engagement wall of the carrying structure, wherein the at least one retention element (10a, 10b) is configured to cooperate with at least one stop face for limiting the maximum movement of the contact body in the direction of the engagement wall of the carrying structure.