the cross bolt is fixed immobile in the hinge arm 30 so that when piston rod 38 is extended it pivots hinge arm 30 around first pivot axis 12 thereby folding cover 10 down into the closed position to perform the second phase of motion there is a pivot lever 52 which in relation to bearing base 42 is pivotably mounted in a second pivot axis 54 which runs parallel to the first pivot axis 12 when lever 52 is pivoted cross bolt 50 moves in the longitudinal hole 48 of bearing base 42 longitudinal hole 48 and hence longitudinal hole 46 as well therefore describe a circular arc around the second pivot axis 54 to lock cross bolt 50 in relation to longitudinal holes 46 48 in which it is displaceably disposed crosswise to its axis the pivot movement of pivot lever 52 in relation to bearing base 42 can be prevented fig1 and 6 show how this is done in the side of bearing base 42 which is folded down onto console 14 when piston rod 38 is extended there is a window 56 in which a locking bolt 58 becomes visible which is prestressed towards the right in fig6 by a compressing spring 60 in the advanced position the relatively thin tip 62 of the locking bolt penetrates through bearing base 42 into a hole 64 in pivot lever 52 this locks pivot lever 52.