Abstract:
The present invention refers to an under felt inclined flat former for making multilayer or monolayer sheets of paper comprising a plurality of forming units arranged along a production line. Each of the forming units is supported on corresponding rigid supports and is provided with a rolls system on which the forming unit rests when the support are removed, in such a manner that the selected forming unit can be removed from the production line for cleaning or maintenance purposes, without interrupting the operation of the former equipment.

Description:
This application is a continuation of application Ser. No. 08/236,451 filed on May 02, 1994, now abandoned. 
    
    
     FIELD OF INVENTION 
     The equipment of the present invention serves to form a sheet of paper under the felt line, this sheet can be for monolayer or multilayer paper. The paper sheet so formed has superior characteristics to that of a sheet made in a fourdrinier manufacturing table. 
     SUMMARY OF INVENTION 
     Fiber suspension is distributed through a head box over a forming table, allowing the fiber to freely orient according to a jet/fabric speeds rate, and to the hydraulic pattern generated by a forming activity lip. 
     The effect generated by a activity lip is supplemented by the pulse forming roll allowing the fibers to orient freely or in a controlled fashion according to the roll speed. The water remaining in the fiber suspension is drained in a box divided in three vacuum compartments, to reach a fixed dryness to make contact with a prior unit sheet or with a felt in the case of a first unit. 
     The equipment comprises a forming table in which the tilt can be adjusted according the manufacturing requirements. This forming table comprises a fabric to form the paper sheet, a breast roll also serving as fabric stretcher, forming and dewatering foils, a pulse forming roll, flat boxes, a cylinder mold or support roll, a guide roll and control elements, support structures to support the former equipment, water collection trays, and rails and rolls for maintenance of the former equipment to allow the unit to be removed from service without halting production. The equipment also comprises a fiber distribution head box oriented towards the formation table, as well as a suction slider to extract water from the inner part of the felt. It also is provided with a rubber couch roll which presses the felt and the sheet in such a manner that the paper sheet adheres to the felt and can be transferred to a next formation unit. The couch roll is provided with a mechanism for setting position against the cylinder mold shaft, as well as with a bellows system to raise the cylinder mold or to apply pressure against said cylinder mold. The equipment comprises showers to keep clean the support roll, the fabric and the breast roll. A doctor blade is located in the breast roll for keeping the roll clean and to divert the water drained in this zone to a tray. This unit has a system comprising two vertical structures and a lengthwise beam to provide rigidity thereto. 
     BACKGROUND OF THE INVENTION 
     Currently there are several types of multilayer paper formation equipments among which the following can be mentioned: 
     CYLINDER MACHINE, this machine forms the paper sheet draining the water through a mesh screen adhered to a cylinder. The formed sheet is transferred directly to a felt for further joining the next layer. In this machine there is no control on the fiber orientation nor in the draining speed of the fiber suspension. 
     FLAT FORMERS OVER FELT LINE, these formers have a flat table in the area of formation of the paper sheet, which once the paper sheet is formed, it is transferred to a felt completely surrounding the forming felt to thereafter pass under this formation unit and arrive to the next formation unit. 
     Most of the equipments of the prior art has several disadvantages, such as: inadequate formation, non-adjustable MD/CD tensile ratio, tendency to curl with sheeted paper, non-uniform CD profile (streaks), drop-off and speed limitations among others. 
     The present invention is intended to overcome the defects of the prior art equipments, having further advantages, since it allows control on the fiber orientation in a former equipment under the felt line. It also allows to stop a formation unit and the complete removal thereof from the production line without shooting-down the production process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation view of the paper former showing all its constituents. 
     FIG. 2 is a detail of the couch roll with all the mechanisms thereof. 
     FIG. 3 shows a detail of the breast roll, the forming knife and the head box also with all their components. 
     FIGS. 4a, 4b and 4c, illustrate the activity lip as well as all the components thereof. 
     FIG. 5 illustrates the water collecting trays and showers forming part of the formation unit. 
     FIG. 6 illustrates a side view of the forming roll; and 
     FIG. 7 illustrates a detail of the forming roll vane. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1 the equipment of the present invention comprises a vertical frame (1) anchored in its lower part by screws (4) and also comprises a second frame (3) anchored in the lower part to the floor by screws (7). A beam (2) is located in the top part of both frames, joining both frames by means of screws (5) and (6). In the second frame (3), at the exit side of the paper sheet, there is located a mechanism for applying pressure or for raising the couch roll (25), this mechanism comprises two supports (8) and (9), each of them has a corresponding rubber pneumatic bellows (10) and (11) joined thereto. As can be seen in FIG. 2, the upper pneumatic bellows (10) is joined to the top part of the support (8) by screws (14) and to the lower part to an arm (12) that is attached to the couch roll by means of screws (15). The upper bellows (10) has as a function to raise the couch roll. The pneumatic lower bellows (11) is attached in the lower part to the support (9) by means of screws (17) and in the top part is attached to the arm (12) by means of screws (16). A support (13) is joined to the frame (3), said support (13) carries a bearing (30) in its central portion; said bearing houses a pin (31), that acts a fulcrum for the arm (12) which fastens the couch roll by means of a support (18) that in turn is attached to a supporting block (19) through screws (20). The supporting block (19) has a threaded hole in the central part thereof. This block adjusts its position by means of a spindle (21) fixed to the arm (12) by means of dividers (28) and (29); the supporting block (19) is attached to the journal bearing (26) that supports the couch roll by means of rotating screws (23) and a separating block (22). 
     The rotating screws (23) press the journal bearing of the couch screw by means of a nut (24) and rotate by means of a pin (27) fixed to the block (19). 
     As illustrated in FIG. 1, the equipment of the present invention also comprises a suction slider (134) that extracts the water from the sheet of paper and the felt when being pressed between the couch roll (25) and the cylinder mold (32). 
     In FIG. 3, it is this equipment also comprises a breast roll (97), a former roll (83) a flat box with three compartments (74), (75) and (76) having corresponding high density polyethylene covers (77), (78) and (79) in their upper part. It also has a cylinder mold (32) and a fabric lead roll (51), as well as a formation plastic fabric (72). 
     The flat box with three compartments (74), (75) and (76) is attached to the main structure (35) by means of screws (80) and (81) that in turn allows alignment and leveling of the box. The flat box has a plate (130) which avoids that the water drained from the former fabric (72) adhere to the inner part of the flat box compartments. The cylinder mold (32) rotates on a bearing housed in a journal bearing (33). This journal bearing is attached to a main structure (35) by means of screws (34). The main structure (35) is supported by means of two blocks (37) and (60) which in turn are attached to the bases (39) and (61) of the former equipment. These bases are attached to the supports (43), (47), (65) and (68) by means of spacer blocks (41), (49), (63) and (70). A removable block (37) is attached to the base (39) and to the main structure (35) by means of two rotating screws (36) and (38). A second removable block (60) is attached to the structure and support (61) by means of rotating screws (58) and (59). The removable blocks (37) and (60) serve to keep the whole formation unit in such a way that when it is required to change the formation fabric (72), said blocks are merely removed while the while unit remains in cantilever allowing to carry out set up of the new fabric in a minimum time. The support (39) which is located immediately below the support roll is attached to the bases (43) and (47) by means of spacers (41) and (49) held by screws (40) and (50), the support (61) which is immediately below the breast roll is attached to the bases (65) and (68) by means of spacers (63) and (70), these supports are held by means of screws (62) and (71). 
     The equipment of the present invention has a roll system (45), (46) and (66) which allows the unit to seat on rails (44) and (67) when the spacer blocks (63), (70), (49) and (41) are removed from the supporting position, this allows the unit to be completely removed from the machine without stopping production by merely pulling the former away from its operating position. 
     This unit has a system for controlling the position of the formation plastic fabric (72) by means of a guide roll (51). The mechanism for operating this guide roll operates as follows: the guide roll (51) is supported by a journal bearing (57), this journal bearing is attached to a support plate (56), which is actuated by two pneumatic adjusting bellows (54) and (55), the support plate (56) is kept in position by the rolls (52) and (53), such rolls maintain the horizontal and vertical position of the support plate. The adjusting bellows (54) and (55) adjust the position of the guide roll (51) by changing the pneumatic pressure in each one of said bellows. 
     This equipment comprises a former roll (83), attached to the main structure (35) by means of screws (101), which fix the journal bearing (141) about which the former roll rotates, to said structure. 
     As shown in FIGS. 6 and 7, the former roll is built with a steel core (138) which is coated with a resin (82) whose surface is machined to provide thereto a streamline profile (139), which allows the generation of a positive pulse in the first contact with the fabric and a negative pulse at the time when this profile loses contact with the formation plastic fabric. The peripheral speed of the roll is lower to that of the formation fabric allowing injection of water from the lower part of the fabric to the upper part where the fiber suspension is, creating thus a rearrangement of the fibers. 
     The breast roll (97), shown in FIG. 3, rotates over bearings located in a journal bearing (98), which is attached to the main structure (35) by means of screws (99) and (100). Adjustment of the position of the breast roll is carried out with a spindle (91) by means of nuts (95) and (96). The spindle (91) is attached to a structure (88) which also supports the base of the formation knives (86), this base is attached to the structure (88) by means of a screw (87). The position of the base of the formation knives against breast rolls is adjusted by means of a spindle (92) and retaining nuts (93) and (94). 
     The structure (88) is attached to the main structure (35) by means of screws (89) and (90), the structure of the formation knives holds the formation knife (84) by means of T-shaped sliders (85). 
     A plastic knife (103) is provided to keep clean the breast roll (97), the plastic knife (103) plays a cleaning role and at the same time deviates the water drained by the breast roll towards a collecting tray (128). 
     As shown in FIG. 3, the formation equipment comprises a flow head box, which comprises a conical manifold (121) whose function is to distribute uniformly the flow of the fiber suspension in a direction widthwise to the formation unit. Attached to this conical manifold by means of a throat (117), is a stepped diffuser (114) that is sealed in the lower and upper part by means of a plastic tube (118). To avoid flexing of the stepping diffuser, there is provided a plate (115) that covers completely the diffuser. The plate (115) is attached to the manifold and to the upper part of the head box by screws (119) and (120). The main role of the stepped diffuser is to maintain the fibers in a state of complete dispersion. As illustrated in FIGS. 4a, 4b and 4c, the head box has a lower lip (109) and an upper activity lip (108). The upper lip sets its opening position to control the discharge flow by means of screws (122) located at the ends of the head box, the box profile is adjusted by screws (104) located in the internal part of the head box, in both cases the screws are adjusted by means of retaining nuts and (104). Internal (104) and external (122) screws are attached to a bridge (105) allowing uniform movement of the lip. As illustrated in FIG. 3, at the opposite end, the upper activity lip (108) has a universal joint (110) supported over a plate (112) and to a retaining unit (111). This allows the upper activity lip (108) to move freely without fiber suspension leaks. The discharge end of the upper activity lip has a profile designed to create activity in the fiber suspension and which is able to orient high concentration of fibers; it also allows obtaining a paper of lower density. This profile is comprised by a inclined part (136) and a straight part (135), that make a change in the speed in the flow of the fiber suspension, both horizontally and vertically. The activity profile is spaced widthwise of the head box by means of sectors (137), illustrated in FIG. 4b, keeping the same thickness of the upper activity lip, the upper activity lip internally generated hydraulic pattern produces crossed flows over the forming table at the time the fiber suspension leaves the head box. This makes the fiber orientation to be improved transversely, that is the fiber orientation ratio in the machine direction to the transversal fiber orientation decreases. In this way, the values of the physical properties of the paper in the transversal sense tend to be similar to those in the machine sense. 
     As shown in FIG. 5, shower (131) keeps the cylinder mold (32) clean. There is also a second shower (132) to keep the guide roll (51) clean. The formation fabric (72) is kept clean by means of a high pressure shower (133). 
     To collect the drained water in the unit there are a series of trays (127), (128), (129) and (126) collecting such water and driving it to an independent tank.