Headbox and setting device therefor The present invention relates to a headbox arranged in the wet section of a paper machine, which wet section comprises a forming roll and at least one forming wire defining a wedge-shaped inlet gap, which headbox has a slice with a slice opening, located in said wedge-shaped inlet gap for discharging a single-or multi-layered jet of stock, having a certain geometry relative to a forming zone of the forming roll, and which headbox is supported by a machine stand and has -opposing support arms and bearing housings for creating a fixed centre of pivot for the headbox during operation, which centre of pivot is parallel to the axis of rotation of the forming roll, -central setting members, arranged to act between said bearing housings and machine stand for movement of said centre of pivot in parallel and corresponding adjustment of the slice opening in relation to the forming zone and -at least one outer setting member arranged at a distance from the central setting members to act between an outer part of the headbox and said machine stand for pivoting of the headbox about its centre of pivot and corresponding pivoting of the slice opening in relation to the forming roll.

The invention also relates to a device for setting a headbox arranged in a section of a paper machine, which wet section comprises a forming roll and at least one forming wire defining a wedge-shaped inlet gap, which headbox has a slice with a slice opening, located in said wedge-shaped inlet gap for discharging a single-or multi-layered jet of stock, having a certain geometry relative to a forming zone of the forming roll, and which headbox is supported by a machine stand and has opposing support arms and bearing housings for creating a fixed centre of pivot for the headbox during operation, which

centre of pivot is parallel to the axis of rotation of the forming roll, which device comprises -central setting members, arranged to act between said bearing housings and machine stand for movement of said centre of pivot in parallel and corresponding adjustment of the slice opening in relation to the forming zone and -at least one outer setting member arranged at a distance from the central setting members to act between an outer part of the headbox and said machine stand for pivoting of the headbox about its centre of pivot and corresponding pivoting of the slice opening in relation to the forming roll.

The function of a headbox is to distribute the stock in such a way that an even distribution of the fibers is achieved in the paper web. This occurs, inter alia, by the jet of stock being discharged from the headbox through the slice opening so that the jet of stock impinges on the forming wires in a forming zone. The paper web is formed by water being drained off through one of the wires or both, whereby the layer of stock is gradually thickened to a continuous fiber network. To obtain the correct sheet structure it is of considerable importance to provide the jet of stock with a certain and carefully tested geometry relative to the forming zone.

Accordingly, the headbox must comprise one or more setting devices so that the necessary changes of the geometry of the jet of stock relative to the forming zone can be carried out.

Depending on the type of wire section, the headbox is arranged so that the jet of stock is directed downwards, horizontally or upwards into the inlet gap between the forming wires, which direction must be set, for instance, after a wire replacement, after maintenance and on changing from one quality to another with respect to the grammage of the paper as well as during the actual

installation of the headbox. I is of the utmost importance that the direction is correctly set, as a great part of the dewatering takes place in the beginning of the forming zone, which dewatering is dependent on the direction of the jet of stock against the forming roll.

Many of the headboxes currently in use are heavy, robust constructions arranged to be set in relation to the forming zone by being pivoted about a centre of pivot located in the forward part of the headbox, usually a considerable distance from its axis of gravity. The actuators of the setting device must therefore overcome a very great part of the weight of the headbox during setting and slight changes of the geometry of the jet of stock are difficult to perform in a sufficiently quick and easy manner. Powerful, bulky screw jacks must therefore be used to overcome and carry the great loads.

After installation, re-setting is usually performed only after long intervals of time, in connection with maintenance, replacement of wires or change of quality with respect to the grammage of the paper, for instance.

The surroundings of a paper machine constitute an aggressive environment for the paper machine with a significant risk of corrosion and extensive dirtying of its structural elements. Screw jacks are sensitive to such environments. Their function can be impaired and, especially if they have not been used for some time, movable parts can get jammed, for instance.

DE-31 25 278 describes a headbox for a breast-roll former having an outlet slice with an adjustment lip, adjustable by means of an eccentric device. To adjust the adjustment lip, a pair of bellows and an adjustment spindle are also disposed by the outlet slice. The headbox can be swivelled about a journalling shaft to a position for maintenance and cleaning of the headbox. With this particular type of headbox, a free jet of stock is not formed between the forming wire and the outlet nozzle.

The function of the eccentric device is to set the cross section of the stock outlet and, thereby, the quantity of stock ejected onto the forming zone of the breast-roll former. No device is provided for setting the length and direction of the jet of stock with this known headbox.

US-A-5,565,064 describes a headbox with a complicated setting device, comprising an inclined plane, pivotable by means of rearward actuators about a support arranged at the forward end of the plane. The headbox is further pivotable about a second axis, arranged by a bearing housing displaceable along the inclined plane. The whole weight of the headbox as well as of the setting device is carried by the rearward actuator and the forward support.

It should be understood that such a setting device requires an extremely robust and expensive construction.

As the axis of gravity will vary considerably depending on the position of the headbox, all the constituent structural elements must be dimensioned for several potential cases of load distribution. The actuators are therefore severely over-dimensioned and the setting of the jet of stock is made more difficult, as the large and cumbersome actuators cannot provide the requisite precision and flexibility. As the headbox is suspended in a system of several actuators, it is also difficult to damp vibrations in the construction in a satisfactory manner.

US-A-3,944,465 describes a headbox supported by two opposite wedge members, displaceable in relation to each other by means of a threaded spindle with opposite pitches. On relative displacement of the wedge members, the headbox is pivoted about a centre of pivot, thereby causing the alignment of the headbox to be adjusted in relation to a forming zone. The wedge members carry the entire load and are therefore subjected to considerable stress. The setting of the headbox is completely limited

to the possibilities offered by the actual inclination of the wedge members in question and the threading of the spindle.

US-A-4,240,872 (corresponding to SE-408 190) describes a headbox with a setting device comprising a link system consisting of a plurality of cooperating link arms, manipulated in a complicated manner by several power cylinders. The constituent structural elements are robust and expensive, as the link system carries the entire weight of the headbox. Because of the pivotable suspension, any loss of pressure in the power cylinders will result in an immediate change in the setting of the jet of stock. The centre of pivot of the headbox is located in the extension of the slice opening of the headbox or other suitably chosen centre of pivot in the vicinity of the slice opening, thus, at a considerable distance from the axis of gravity of the headbox. The known headbox is thus rotated about an indefinite, imaginary centre of pivot.

The object of the present invention is to provide a headbox with an improved setting device, especially with respect to the pivoting of the headbox about a fixable centre of pivot by means of a mechanical setting member that is, inter alia, easy to influence manually, less sensitive to the environment in question, and able to carry out small, stepless adjustments to the impingement point of the jet of stock on the forming wire swiftly during operation.

The headbox in accordance with the invention is characterized in that its centre of pivot is arranged in proximity to the plumb-line of the axis of gravity of the headbox and between this plumb-line and the slice opening so that only a correspondingly lesser part of the weight of the headbox is loading the outer setting member, and

in that the outer setting member comprises an eccentric member and a mechanical actuator arranged to act upon the eccentric member for stepless pivoting of the headbox about its centre of pivot.

The setting device in accordance with the invention are characterized in that the centre of pivot of the headbox is arranged in proximity to the plumb-line of the axis of gravity of the headbox and between this plumb-line and the slice opening so that only a correspondingly lesser part of the weight of the headbox is loading the outer setting member, and in that the outer setting member comprises an eccentric member and a mechanical actuator arranged to act upon the eccentric member for stepless pivoting of the headbox about its centre of pivot.

The setting device in accordance with the invention are considerably simplified in comparison with known constructions, but nevertheless provide ample setting possibilities for swiftly and efficiently providing the jet of stock with a desired geometry relative to the forming zone. The invention is particularly pertinent to smaller and lighter headboxes, which are significantly more economical to manufacture than known headboxes with sophisticated setting devices.

The invention is further explained in the following with reference to the drawings.

Figure 1 is a side view schematically showing parts of a wet section with a headbox, having a rearward setting member in accordance with the invention.

Figure 2 is an end view of parts of the headbox according to Figure 1, as seen facing the upstream end of the headbox.

Figure 3 is a top view of one of the bearing housings of the headbox with a first, central setting member.

Figure 4 is an end view of parts of the rearward setting member of the headbox according to Figure 1.

Figure 5 is a side view of the rearward setting member according to Figure 4.

Figure 6 is an enlarged view of the forward part of the headbox according to Figure 1.

A side view of parts of a wet section in a paper machine is schematically shown in Figure 1, which wet section comprises a roller-type twin-wire former 1 and a headbox 2. The twin-wire former 1 comprises an inner forming wire 3, running in an endless loop, a rotatable forming roll 4, situated inside the loop of the inner forming wire 3, an outer forming wire 5, running in an endless loop, and a rotatable breast roll 6, situated inside the loop of the outer forming wire 5. The forming wires 3,5 define between them a wedge-shaped inlet gap 7, leading to a forming zone 8 in connection to the point where the forming wires 3,5 run together, in which forming zone 8 dewatering occurs through one of the forming wires 3,5 or both. In accordance with an alternative embodiment, the wet section comprises a former, having a forming roll and a forming wire.

The headbox 2 has a frame 9, supporting a slice 10, comprising a first lip part 11, rigidly mounted on the frame 9, and a second lip part 12, pivotably mounted on the frame to be pivoted about a horizontal shaft 13 by means of an actuator 14. The two lip parts 11,12, together with two vertical side walls 15,16, encompass a slice chamber 17, terminating in a slice opening 18, the width of which can be set by pivoting the movable lip

part 12 in relation to the rigid lip part 11 by means of said actuator 14. The slice opening 18 is located in the wedge-shaped inlet gap 7, and the headbox is arranged to discharge a jet of stock 19 through this slice opening 18 into the wedge-shaped inlet gap 7. As is evident from Figure 6, the slice chamber 17 has a partition wall 69, the jet of stock discharged consisting of two layers. The headbox 2 is detachably mounted on a machine stand 70, comprising two parallel stand parts 20,21, see Figure 2, arranged at a distance from each other along the operator side and drive side of the paper machine, respectively, of the paper machine and a horizontal supporting beam 22, extending between and rigidly connected to the stand parts 20,21.

The headbox 2 is supported by support means, comprising two support arms 23,24, rigidly mounted on the vertical side walls 15,16 of the headbox and co-axial to each other. Each support arm 23,24 is provided with a shaft pin 25,26, journalled in a bearing housing 27,28, directly or, as shown in the drawings, indirectly connected to the stand part 20 or 21, respectively. The shaft pins 25,26 define centre of pivot Hc, parallel to the axis of rotation Fa of the forming roll 4. The support arms 23,24 are arranged within a central part of the headbox 2 so that the centre of pivot Hc is located in proximity to the plumb-line 29 through the axis of gravity Ga of the headbox and between this plumb-line 29 and the slice opening 18. The headbox is thereby balanced in an advantageous way so that only a small part of the weight of the headbox will load the supporting beam 22 of the machine stand at the rearward, i. e. upstream, end of the headbox.

The headbox 2 is provided with a setting device for setting the position of the slice opening 18 in the inlet gap 7 and the direction of the slice chamber 17 into the

inlet gap 7 so that the jet of stock 19 obtains a desired free length and contacts the forming roll 4 tangentially with its side facing the forming roll 4 or, alternatively, impinges on the forming roll 4 with a certain proportion of its thickness, up to 30 per cent, for instance. The setting device comprises a first pair of central setting members 30,31, a second pair of setting members 32,33 and an outer setting member 34.

One of the setting member in each pair of central setting members 30,31; 32,33 is arranged on the operator side, while the other setting member in each such pair is arranged on the drive side. The central setting member 30,31, and 32,33 are arranged to set the centre of pivot Hc of the headbox in a certain, fixed position in relation to the inlet gap 7 and the forming roll 4, while the rearward setting member 34 is arranged to pivot the headbox about its centre of pivot Hc clockwise or anti-clockwise so that the slice opening 18 is displaced in one of the directions indicated by arrows, see Figure 1.

Each setting member in the first pair of central setting members 30,31 comprises a slide body 35, constituting a supporting, lower part of the bearing housing 27,28, and a stationary support body 36, having an inclined support surface 37, sloping towards the slice opening 18 and supporting the slide body 35 in such a way that the underside of the slide body 35 is in sliding contact with the support surface 37. The support surface 37 is substantially parallel to the direction of the jet of stock 19. Each support body 36 rests on a flat base plate 38, detachably mounted to its respective stand part 20,21 by means of a plurality of mounting bolts 39, see Figure 3.

Each setting member in the second pair of central setting members 32,33 comprises one or several flat spacing

plates 40, disposed between the flat base plate 38 and the stand part 20,21. Forward and rearward adjusting screws 41,42 are arranged co-axially to each other by the slide body 35 for fixing the bearing housing 27,28 to the support body 36. The adjusting screws 41,42 are of such a length and are screwed into the slide body 35 in such a way that they each press against a respective counter-support 43,44, arranged at the ends of the inclined support surface 37. The adjusting screws 41,42 comprise nuts 45 for locking the bearing housing 27,28 in the set position. The slide body 35 is provided with two slot-shaped grooves 46, see Figure 3, arranged sequentially in the machine direction for fixing the bearing housing 27,28 to the support body 36 by means of mounting bolts 47, extending through the groove 46 of the slide body 35 and arranged to be screwed into threaded holes in the support body 36.

The outer setting member 34 is arranged by the rearward, upstream wall of the headbox by the middle of the headbox, preferably centrally between the side walls 15,16 and comprises a link and connecting system including two parallel link arms 48,49, obliquely directed upwards. Each link arm 48,49 is via its upper end pivotably journalled by means of a pivot pin 50 to an attachment member 51, rigidly mounted to the rearward wall of the headbox 2, which extends across the machine direction.

The outer or rearward setting member 34 further comprises two bearing housings 52,53 arranged at a distance from each other and rigidly mounted to said supporting beam 22, and an eccentric member 54, comprising a pivoting shaft 55, extending between and via its end parts pivotably journalled in said bearing housings 52,53. The eccentric member 54 has two eccentric journals 56,57, eccentrically, rigidly mounted on the ends of the

pivoting shaft 55. The eccentric journals 56,57 form journalling pins for pivotable journalling of the lower ends of the link arms 48,49. The eccentric journals 56,57 are co-axial with each other and have an eccentric axis parallel to the centre of pivot Hc of the headbox and to the centre of pivot of the pivoting shaft 55. The pivoting motion of the pivoting shaft 55 can be detected on a gauge (not shown) on one of the bearing housings 52,53 with the assistance of an indicator (not shown) mounted on the pivoting shaft.

The rearward setting member 34 further comprises a mechanical actuator 59 for stepless pivoting of the pivoting shaft 55, which includes a lever 58, rigidly mounted to the centre of the pivoting shaft 55 for pivoting the same about its centre of pivot. The actuator 59 has a screw joint in the shape of a shroud screw 60, having a first right-threaded or, alternatively, left-threaded screw pin 61, which via one of its ends is pivoted on the lever 58 by means of a pivot pin 62, located a pre-determined distance from the centre of pivot of the pivoting shaft 55 to obtain the requisite leverage, and a second left-threaded or, alternatively, right-threaded screw pin 63, which via one of its ends is pivoted by means of a pivot pin 64 on an attachment member or counter-support 65, rigidly mounted on the supporting beam 22. Furthermore, the shroud screw 60 has a hexagonal sleeve 66 with internal, threaded parts for receiving the other ends of the screw pins 61,63, which ends face each other and are in screw engagement with the hexagonal sleeve 66, which thus has correspondingly threaded holes. By means of a spanner, the hexagonal sleeve 66 is turned manually in one direction so that the screw pins 61,63 are screwed into the same, whereby the distance between the pivot pins 62 and 64 diminishes to a corresponding degree, and in the other direction so that the screw pins 61,63 are screwed out from the hexagonal

sleeve 66, whereby the distance between the pivot pins 62,64 increases to a corresponding degree. Each screw pin 61,63 carries a locking nut 67,68, which locking nuts are arranged to be securely screwed onto the hexagonal sleeve 66 to lock the same to prevent turning relative to the screw pins 61,63. The locking nuts 67,68 are thus loosened before the hexagonal sleeve 66 is turned.

The headbox is disposed at installation behind the forming and breast rolls 4,6 so that the centre of pivot Hc of the headbox is located in an initial position in relation to the inlet gap 7 and the forming roll and so that the slice 10 acquires an initial direction and the slice opening 18 assumes an initial position in the inlet gap 7. All the setting members 30,32,34 are in locked positions so that the headbox is stable and secured to the machine stand 70 without vibrations. On the stationary lip part 11, by the slice opening 18, is a permanent position mark, the co-ordinates of which in a perpendicular system of co-ordinates are noted and registered, which system of co-ordinates has its point of origin in the axis of rotation Fa of the forming roll 4 and its axes of abscissae and ordinates constituted by horizontal and vertical lines which thus coincide with two perpendicular diameters of the forming roll 4. The registered value of the pair of co-ordinates forms the basis of the continued adjustment of the headbox 2, which is moved so that the slice opening 18 is set in a new position, in respect of which the pair of co-ordinates is noted and registered, whereupon one or both of the co-ordinates will have new values depending on whether the headbox has been moved in one or two directions.

Further such movements may take place as required. Before each linear movement of the slice opening 18 with corresponding linear movement of the centre of pivot Hc of the headbox, the locking devices of the central

setting members 30,31,32,33 in the shape of the mounting bolts 39 and 47, respectively, are loosened, and after each linear movement, the headbox is again locked securely relative to the machine stand 70 by means of said mounting bolts 39,47. After the last movement, at least, the headbox is pivoted in the desired direction about the fixed axis of pivot Hc so that the slice 10 and, thereby, the jet of stock 19 acquire the desired direction. Before each pivoting movement of the headbox about its centre of pivot Hc, the locking nuts 67,68 of the rearward setting member are loosened, and after each pivoting movement the headbox is again locked securely by means of said locking nuts 67,68 to prevent further pivoting movement.

The length of the jet of stock 19 is thus adjusted by moving the centre of pivot Hc and, thereby, said position mark forwards or backwards relative to the forming zone 8. The radial position of the slice opening 18 relative to the forming roll 4 is adjusted by moving the centre of pivot Hc in the direction away from or towards the flat surface of the machine stand 70 that supports the spacing plate or plates 40, whereby the jet of stock 19 is moved in parallel to a new position. For this adjustment, suitable equipment is used to move the headbox in the direction away from said flat support surface of the machine stand 70 so that a sufficiently free interspace is obtained to enable one or several spacing plates 40 to be introduced into or removed from the free interspace, depending on whether the centre of pivot Hc is to be moved in the direction away from or towards said flat surface of the machine stand 70. Thereafter, the headbox is moved back to be supported by the machine stand 70 via the base plate 38 and the spacing plates 40 and locked securely to the machine stand 70 by means of the mounting bolts 39. The direction of the jet of stock 19 relative to the forming roll 4 is adjusted by steplessly pivoting

the headbox about the thus fixed centre of pivot Hc in a clockwise or anti-clockwise direction with the assistance of the rearward setting member 34. The side 71 of the jet of stock 19 facing the forming roll 4 impinges on the forming roll 4 at a point P, see Figure 6. The direction of the slice 10 and the jet of stock 19 can be determined by an angle a, defined by the forming-roll side 71 of the jet of stock 19 and the tangent T to said point of impingement P. By said pivoting of the headbox, said point of impingement P is thus moved closer to or further away from the slice opening 18, whereby the angel a is changed accordingly. When the forming-roll side of the jet of stock 19 is tangential to the forming roll 4, the angle a is consequently 0°.

As the headbox balances about the centre of pivot of the bearing housings 27,28 close to a position of equilibrium and as the loads of the headbox are, to a very large extent, transferred directly to the stand parts 20,21 via the bearing housings 27,28, it is sufficient to apply only a small force at the rearward part of the headbox to achieve the pivoting requisite for adjustment of the headbox. A significant advantage with the invention is therefore that a simpler and considerably cheaper setting member can be used, as compared with screw jacks, which setting member, furthermore, is very suitable for use in the aggressive environment that prevails around headboxes, as it is relatively non-sensitive and maintains superior precision for each adjustment of the headbox relative to the forming zone even after long periods of inaction.

The invention is not limited to the embodiment described above but may be varied and modified in several different ways within the scope of the appended claims. The headbox can also be of the type that emits a jet of stock consisting of one layer or more than two layers. The

outer setting member, arranged at a distance from the central setting member, can be arranged to act between any suitable outer part whatsoever of the headbox and the machine stand, primarily depending on the alignment of the headbox. Instead of one single rearward setting member arranged by the middle of the rearward end wall, two rearward setting members arranged at a distance from each other by the rearward end wall can be used, for instance in proximity to the side walls of the headbox, which extend in the machine direction.