its locking projection 140 a under the free end of the lever arm 138 a of the lever component 138 due to the bias of the spring 132 acting on the lever arm 138 a the lever arm 138 a which is then unlocked and the ejector ram 126 coupled thereto is forced out of its position in which it is almost completely retracted into the housing through the through opening 126 and out of the housing the door leaf 12 being pivoted up automatically into the position c however further pivoting of the lever arm 138 a is then prevented by contact of the lever arm 138 b of the lever arm 38 a on the adjacent distance piece 136 so that as opening proceeds further the door leaf 12 is lifted off from the pressure surface 128 a of the ejector ram 128 fig1 d the slide 150 of the tensioning and stopping device 134 is then drawn forwards by way of the rod component 122 articulated on the fixing bracket 124 wherein in co operation with the control projection 156 engaging in the control groove 152 of the slide 150 the control disc 154 is pivoted and in turn by pressure on the lever arm 138 b pivots the lever component 138 back against the tension of the spring 132 due to the coupling of the ejector ram 128 on the lever arm 138.