A brake cylinder having a locking device for mechanical brake force locking, in particular for rail vehicles, and having a service brake piston that can be moved axially inside a housing, can be moved by the application of a pressure medium and is coupled to a piston tube, this piston tube being designed with a non-self-locking thread that is in mesh with a threaded nut that is mounted rotatably in the housing, the locking device cooperating with the toothing of the threaded nut, the locking device comprising at least two locking elements (11, 12, 20), a control piston and an emergency release tappet, characterised in that at least two locking elements in the form of locking pawls (11, 12) are arranged on the toothing of the threaded nut and radially opposite one another in relation to a piston axis with which the threaded nut is itself arranged coaxially, it being possible, by means of the control piston and/or the emergency release tappet, to actuate the at least two locking pawls (11, 12) simultaneously by means of both the one control piston and the one emergency-release tappet, it being possible to shift the locking device from a locked position, in which the at least two locking pawls (11, 12) block the rotation of the threaded nut about the piston axis by meshing with the toothing of the threaded nut, the at least two locking pawls (11, 12) each being pressed into mesh with the toothing of the threaded nut by means of a spring (15a, 16a), into a release position in which the locking pawls (11, 12) are out of mesh with the toothing of the threaded nut and do not block the rotation of the threaded nut, the locking device being shifted into the release position by the application of control pressure to the control piston or the emergency-release tappet being shifted out of a standby position into a release position by means of a tool and/or manually and the one or more locking pawls (11, 12) being actuated, it being possible to shift the locking device from the release position into the locked position by means of the control piston when, following the application of pressure, the control piston is subsequently deaerated again or, in the case of the emergency-release tappet, it is returned from its release position to its standby position. the locking device comprising at least two locking elements (11, 12, 20), a control piston and an emergency release tappet, characterised in that at least two locking elements in the form of locking pawls (11, 12) are arranged on the toothing of the threaded nut and radially opposite one another in relation to a piston axis with which the threaded nut is itself arranged coaxially, it being possible, by means of the control piston and/or the emergency release tappet, to actuate the at least two locking pawls (11, 12) simultaneously by means of both the one control piston and the one emergency-release tappet, it being possible to shift the locking device from a locked position, in which the at least two locking pawls (11, 12) block the rotation of the threaded nut about the piston axis by meshing with the toothing of the threaded nut, the at least two locking pawls (11, 12) each being pressed into mesh with the toothing of the threaded nut by means of a spring (15a, 16a), into a release position in which the locking pawls (11, 12) are out of mesh with the toothing of the threaded nut and do not block the rotation of the threaded nut, the locking device being shifted into the release position by the application of control pressure to the control piston or the emergency-release tappet being shifted out of a standby position into a release position by means of a tool and/or manually and the one or more locking pawls (11, 12) being actuated, it being possible to shift the locking device from the release position into the locked position by means of the control piston when, following the application of pressure, the control piston is subsequently deaerated again or, in the case of the emergency-release tappet, it is returned from its release position to its standby position.