16 of the rod 15 is hinged by a pin 17 to the first longitudinal end 18 of a fork 19 whose second longitudinal end 20 is hinged to the lever 7 by a pin 21 positioned near the above mentioned pin 8 the pin 17 is slidably constrained to two guide and end of stroke slots 22 made in the sides of the second element 6 and extending in a prevalent direction of extension parallel with the direction b the position of the pin 21 which is closer to the axis b than the pin 8 and the pre compression of the spring 13 guarantee an elastic action which tends to continuously push and hold the door 3 in its closed position only when the closed position is almost reached from and towards the closed position overlapping with the above mentioned elastic action of the spring 13 there is the action of another pre compressed helical spring 23 designed to operate in conjunction with a cam 24 made on a second arm 9 b of the rocker lever 7 through a rod 25 acting on a cam follower 26 to give the door 3 a spring to closing movement and to define a door stable semi open position specifically the follower 26 is supported by a pin 27 slidably constrained to two guide and end of stroke slots 28 made in the sides of the second element 6 and extending in a prevalent direction of extension parallel with the direction b the follower 26 is pushed towards the cam 24 by a race made on one end of the rod 25 and the latter is pushed by the spring 23 which is stopped in contact with a transversal separator 29 in the second element.