Paper making machine and process
Paper making machine comprising a forming zone in which a layer of fibrous material is formed, a zone for forced removal of water from the fibrous material layer downstream of the forming zone, a drying zone downstream of the forced removal of the water, and a paper collection zone downstream of the drying zone, and means for transporting the layer of fibrous material through said zones of the machine along a path that follows a predetermined transport direction (MD). The forced water removal zone comprises, in turn, two consecutive zones (Z 1 , Z 2 ) along said transport direction (MD), in which a capillary roller ( 44 ) and a pressure element ( 4 S) with a respective counter-roller ( 4 C) are respectively arranged, acting consecutively on the layer of fibrous material upstream of the drying zone.
1 . A process for production of paper comprising a formation step in which a layer of fibrous material is formed, a step of forced removal of water from the layer of fibrous material downstream of the formation step, a drying step downstream of the forced water removal step, and a paper collection step downstream of the drying step, wherein the transport of the layer of fibrous material along a path that follows a predetermined transport direction (MD) is executed by means for transporting the layer of fibrous material, along said path said operating steps are executed in succession, characterized in that the forced removal of the water step includes, in turn, two consecutive steps in which the layer of fibrous material passes over a capillary roller ( 44 ) and a pressure element ( 4 S) with a respective counter-roller ( 4 C) acting consecutively on the layer of fibrous material upstream of the drying step, the two consecutive steps being performed in two consecutive zones (Z 1 , Z 2 ) along said transport direction (MD), in which are respectively arranged the capillary roller ( 44 ) and the pressure element ( 4 S) with the respective counter-roller ( 4 C) such that the capillary roller ( 44 ) and the pressure element ( 4 S) with the respective counter-roller ( 4 C) act consecutively on the layer of fibrous material.
2 . The process according to claim 1 characterized in that the layer of fibrous material is supported by a conveyor web ( 4 ) which crosses the zone (Z 2 ) where the pressure element ( 4 S) is arranged while it is pressed, in correspondence with a nip, against a further web ( 5 ) placed between the pressing element ( 4 S) and the counter-roller ( 4 C).
3 . The process according to claim 1 , wherein the layer of fibrous material is supported by a conveyor web ( 4 ) which crosses the zone (Z 2 ) where the pressure element ( 4 S) is arranged while it is pressed, in correspondence with a nip, against a further web ( 5 ) placed between the pressing element ( 4 S) and the counter-roller ( 4 C), process characterized in that the further web ( 5 ) is a felt.
4 . The process according to claim 1 characterized in that the pressure element ( 4 S) is a shoe press.
5 . The process according to claim 1 characterized in that the counter-roller ( 4 C) is a suction roller.
6 . The process according to claim 1 characterized in that the means for transporting the layer of fibrous material in said two consecutive zones (Z 1 , Z 2 ) comprise a transport web ( 4 ) that is constituted by a structured fabric or TAD fabric.
7 . The process according to claim 1 characterized in that the means for transporting the layer of fibrous material in said two consecutive zones (Z 1 , Z 2 ) comprise a conveyor web that is constituted by a felt which can be provided with reliefs of polymeric material on the paper side.
8 . The process according to claim 1 characterized by the fact that the means for transporting the layer of fibrous material in said two consecutive zones (Z 1 , Z 2 ) comprise a web ( 4 ) coated with a polymeric material, in which the paper side surface has drainage holes or reliefs.
9 . The process according to claim 1 characterized in that the pressure element ( 4 S) is selectively activated and deactivated.
10 . The process according to claim 1 characterized in that the forming zone of the machine comprises a forming wire ( 2 ) and a conveyor web ( 3 ) which acts as a means of transport for the layer of fibrous material towards the forced water removal zone.
11 . The process according to claim 1 characterized in that the forming zone of the machine comprises a forming wire ( 2 ) and a web ( 4 ) which acts as a transport means for transporting the layer of fibrous material both through the forced water removal zone and through the drying zone.
12 . The process according to claim 1 characterized in that the means for transporting the layer of fibrous material comprise, in addition to a structured fabric ( 4 ) which crosses said consecutive zones (Z 1 , Z 2 ) of the forced water removal zone, also a transport wire ( 3 ) which transports the layer of fibrous material from the formation zone to the forced water removal zone, and in that the structured fabric ( 4 ) and the transport wire ( 3 ) are configured for performing the transfer of the layer of fibrous material from the transport wire ( 3 ) to the structured fabric ( 4 ) in rush transfer mode, with the structured fabric ( 4 ) having a slower speed than the transport web ( 3 ).
13 . The process according to claim 1 characterized in that the drying zone of the machine comprises a Yankee ( 6 ) and the layer of fibrous material coming out of said zone (Z 1 , Z 2 ) for forced removal of water is transferred to the Yankee ( 6 ) by means of a transfer device selected within a group comprising a transfer roll ( 60 ), a suction press ( 62 ) or a shoe press ( 63 ), on which the means for transporting the layer of fibrous material are guided.