Patent ID: 7703182

Claim:
A hermetically sealed impermeable zip fastener ( 1 , 2 ), comprising: two rows of facing teeth ( 3 , 4 ) mounted on two strips ( 5 , 6 ) of compressively elastic material, the teeth being joined together and disengaged by a movable slider ( 7 , 27 ) which can be displaced by gripping its outwardly projecting gripping member ( 8 , 9 ), wherein, on opposite sides of the strips ( 5 , 6 ), the slider ( 7 , 27 ) is provided with a first concave capsule ( 10 ) and a second concave capsule ( 11 ) having a form substantially the mirror-image of each other and arranged with the perimetral edges ( 12 , 13 ) of their concavities opposite and facing each other, the first capsule having directed upwards a pin ( 14 ) perpendicular thereto and able to slide perpendicularly through a cavity ( 15 ) inside the slider ( 7 ) and through a hole ( 16 ) formed in the second capsule ( 11 ), the gripping member ( 8 , 9 ) being connected to or having means ( 17 , 18 , 19 , 20 ) which, when actuated, cause a simultaneous displacement of the first capsule ( 10 ) towards the second capsule ( 11 ) and of the second capsule ( 11 ) towards the first capsule ( 10 ) perpendicular to the plane (α) of the zip fastener ( 1 ), which causes a movement, towards each other, of the end parts ( 12 t , 13 t ) of the perimetral edges ( 12 , 13 ) of the capsules ( 10 , 11 ) sufficient to grip between them, with a desired pressure, the strips ( 5 , 6 ), the gripping member is a pull tag ( 8 ) which is keyed onto a spindle ( 19 ) keyed at the ends onto a cap ( 24 ) integral with the slider ( 7 ) and which has a cam surface ( 17 ) which is in contact with the upper wall ( 11 s ) of the second capsule ( 11 ), this spindle ( 19 ) passing through a transverse hole ( 20 ) formed in a part ( 14 n ) integral with the free end of the pin ( 14 ) projecting from the first capsule ( 10 ) and having at least one section ( 19 t ) which is also cam-shaped and in contact with a cavity ( 18 ) formed in the cap ( 16 ) designed so that, for a same rotation of the pull tag ( 8 ), the second capsule ( 11 ) is displaced towards the first capsule ( 10 ) over a distance (Δx) by the action of the cam surface ( 17 ) and the first capsule ( 10 ) is displaced towards the second capsule ( 11 ) over an equal and opposite distance (−Δx) by the section ( 19 t ) of the spindle ( 19 ) so that the two capsules ( 10 , 11 ) exert two substantially equal and opposing thrusts on the opposite sides of the strips ( 5 , 6 ) which are gripped between them.