A safety device for detachably locking the output member of a linear drive, comprising: - a coupling rod which can be coupled to the output member of the linear drive, - a housing through which the coupling rod passes in a linearly displaceable manner, - a blocking unit through which the coupling rod passes in a linearly displaceable manner and which is movable, relative to the housing , between a blocking position which blocks a stroke of the coupling rod and a release position which allows a linear movement of the coupling rod , - a spring means for preloading the blocking unit in the blocking position , - a locking means for locking the blocking unit in the release position , the locking means comprising locking rolling bodies (34a-c) received in the housing and a support sleeve through which the coupling rod passes in a linearly displaceable manner, it being possible to move the support sleeve between a support position , in which the support rolling bodies (34a-c) are held in a locking position radially outwards in locking engagement with the blocking unit , and a release position , in which a retraction of the support rolling bodies (34a-c) radially inwards out of engagement with the blocking unit is made possible, - an electromagnet means which, when energized, holds the support sleeve in the support position against the actuating force of at least one release spring of a release spring means in such a way that, in the event of a power failure, the holding function can be reversed and the support sleeve enters the release position by means of the at least one release spring , as a result of which the blocking unit can be transferred into the blocking position by means of the spring means ; characterized in that a stop is formed on the coupling rod and a counter-stop is formed on the blocking means , which stop and counter-stop are arranged in the release position at an axial distance relative to one another that determines the stroke of the coupling rod and, in the blocking position , abut one another so as to bring about the locking of the output member. - a coupling rod which can be coupled to the output member of the linear drive, - a housing through which the coupling rod passes in a linearly displaceable manner, - a blocking unit through which the coupling rod passes in a linearly displaceable manner and which is movable, relative to the housing , between a blocking position which blocks a stroke of the coupling rod and a release position which allows a linear movement of the coupling rod , - a spring means for preloading the blocking unit in the blocking position , - a locking means for locking the blocking unit in the release position , the locking means comprising locking rolling bodies (34a-c) received in the housing and a support sleeve through which the coupling rod passes in a linearly displaceable manner, it being possible to move the support sleeve between a support position , in which the support rolling bodies (34a-c) are held in a locking position radially outwards in locking engagement with the blocking unit , and a release position , in which a retraction of the support rolling bodies (34a-c) radially inwards out of engagement with the blocking unit is made possible, - an electromagnet means which, when energized, holds the support sleeve in the support position against the actuating force of at least one release spring of a release spring means in such a way that, in the event of a power failure, the holding function can be reversed and the support sleeve enters the release position by means of the at least one release spring , as a result of which the blocking unit can be transferred into the blocking position by means of the spring means ; <EOS>