EP0046434B1 - Apparatus for controlling the slice opening of a paper making machine head-box - Google Patents

Abstract

A method and apparatus for adjustment of a movable lip of a head-box of a paper-making machine. Tubes mounted on screw-jacks each contain an electrical heating resistor which enables them to increase in length by thermal expansion as a function of the current passed to the electrical resistor. This current is regulated by a computer as a function of continuous measurements of the mass of the sheet of paper produced by the machine.

Description

The present invention relates to a device for fine adjustment of the position of a scraper blade, in particular of a lip of the arrival box of a paper or cardboard machine. It also relates to a method for adjusting a property of the material continuously produced on a machine having a scraper blade, for example a machine for making paper or cardboard, by fine adjustment of the position of the scraper blade.

The description which follows relates to the fine adjustment of the position of the lip of an inlet box or of the head of a paper or cardboard machine, but it should be noted that it has other applications in fields which require adjustment of a scraper blade.

The arrival box of a paper machine transforms the flow of the fibrous suspension, forming the paper pulp, from a cylindrical vein into a blade or layer corresponding to the width of formation of the sheet. This arrival box is presented as a reservoir of variable shape, the front face of which is pierced downwards with a slot provided with lips between which the liquid paste is projected onto a manufacturing table. The function of the arrival box is to ensure a constant and regular flow of the fibrous suspension over the entire width of the machine which can reach 9 m in the case of modern installations.

The blade or layer of fibrous suspension, also containing mineral fillers, is driven off under a pressure of between approximately 0.03 and 2 bars between the lips, in modern fast machines. The regularity of the speed of exit of the layer of fibrous suspension and the thickness conditions, with the regularity of the concentration, that of the weight per unit area of the product produced. In modern paper machines, the flow takes place between two metallic lips, one of which is fixed and the other is movable as a whole so that it adjusts the thickness. In addition, the movable lip, usually the upper lip, is deformable along its length under the action of rods controlled by manual screw jacks. A modern machine inlet box has several dozen such manual cylinders.

The correction of the thickness of the fibrous suspension blade at the passage of the lip as a function of the variations in weight per unit area of the product obtained at the end of the machine is inconvenient using such manual jacks, the adjustment of which is delicate and which only give good results by trial and error.

To overcome this drawback, inward boxes have been constructed in which the manual adjustment jacks are each controlled by a geared motor assembly itself controlled as a function of continuous mass measurements, by means of a computer which receives the result of the mass measurements and calculates the corrections to be made by action on machine elements and in particular on the movable lip.

These geared motor control systems are not satisfactory enough. Indeed, there are still relatively large mechanical clearances and the precision of the adjustment is not very high. The most important drawback, however, is the very high cost of these mechanisms since the arrival box of a modern machine can have up to 60 or more.

U.S. Patent 2,779,253 describes a purely mechanical adjustment device for the movable lip of a headbox of a paper machine. According to this patent, the adjustment is carried out in a purely mechanical manner using the jacks, and the variations are detected using a mechanical comparator. French patent n ° 1,192,516 describes an apparatus for adjusting the orifice for the passage of paper pulp into an arrival box by swelling and deflation of bladders which delimit the edges of the lips. It is therefore a pneumatic or hydraulic device.

Furthermore, the patents of the United States of America No. 2,938,231 and 3,940,221 describe plastic extrusion dies in which the position of a part of a first side of the die is adjusted using a thermodilatable device. In particular, the aforementioned patent of the United States of America No. 3,940,221 describes an extrusion die also intended for paper machines comprising a block of which a part intended to delimit the outlet orifice is separated from the body of the block by a thinned part so that it has a certain elasticity. A thermodilatable rod repels more or less. minus this flexible end in order to precisely determine its position.

The extrusion dies are different devices from the lips of the boxes of arrival of paper machines. In fact, in an extrusion die, the material is driven off under extremely high pressure. The die must form a channel with almost parallel walls, at least over a certain distance, so that they gradually guide the material which undergoes an alignment effect during its directed flow in the orifice of the die. It follows that the thermodilatable device is mechanically stressed in a very significant way, which limits its length to avoid deformations or ruptures. The adjustment possibilities are therefore limited to a range of amplitude that is insufficient for its application to the lip of an incoming box of a paper machine.

Given that there are currently continuous mass measurement devices and that these devices can be connected to computers which allow the knowledge and the calculation of corrections which may be necessary, it is very desirable that simple and inexpensive devices allow fine adjustment, continuously, of the position of the movable lip of a rear box paper machine, at different points along this lip.

The invention relates to such a device having a positioning member mounted between the frame of the machine and the lip, and a device for heating the positioning member so that the length thereof varies and ensures the maintenance of the lip. in the desired position. The latter is determined from the results of continuous measurement, for example mass measurement, by a computer which allows the control of the heating devices of numerous organs placed along the arrival box. The positioning device is therefore a passive mechanism requiring no maintenance and no lubrication, and having extremely high reliability.

• - un organe de positionnement coopérant en un premier point avec le support et en un second point avec la lame de raclage,
• - un dispositif de chauffage d'au moins une partie thermodilatable allongée de l'organe de positionnement reliant les deux points de coopération, et un organe de commande du dispositif (38) de chauffage en fonction de la position voulue pour la lame de raclage par rapport au support (10), caractérisé en ce que l'organe de positionnement est composé de deux éléments dont le premier élément seul forme ladite partie thermodilatable, dont une extrémité est attelée au premier point susdit par l'intermédiaire du deuxième élément de l'organe de positionnement, cet élément, de forme allongée aussi, servant d'organe de montage dont l'une des extrémités est fixée audit premier point tandis que son autre extrémité est attelée à l'autre extrémité de la partie thermodilatable, cette extrémité étant située, vue dudit second point, au-delà dudit premier point, ledit organe de montage étant parallèle à ladite partie thermodilatable.

More specifically, the invention relates to a device for fine adjustment of the position, relative to a fixed support belonging to the structure of an inlet box of a paper machine, of an inclined blade for scraping a fluid on a surface, forming the adjustable lip of this box by displacement of the blade in a predetermined direction, this device comprising:

• a positioning member cooperating at a first point with the support and at a second point with the scraper blade,
• - A heating device of at least one elongated thermodilatable part of the positioning member connecting the two cooperation points, and a control member of the heating device (38) according to the desired position for the scraper blade by relative to the support (10), characterized in that the positioning member is composed of two elements, the first element of which alone forms said thermodilatable part, one end of which is coupled to the above-mentioned first point via the second element of positioning member, this element, also of elongated shape, serving as a mounting member one end of which is fixed to said first point while its other end is coupled to the other end of the thermodilatable part, this end being located , seen from said second point, beyond said first point, said mounting member being parallel to said thermodilatable part.

It is advantageous that the device also comprises a coarse adjustment device, for example a manual screw jack, intended to modify the distance between the two points of cooperation.

In an embodiment of the differential type an additional heating device is intended to heat the mounting member, between its location of cooperation with the thermodilatable part and one of the points.

In this case, a thermal insulation device is advantageously placed between the mounting member and the thermodilatable part.

The positioning member can advantageously further comprise a force transmitting element intended to cause the displacement of the lip in said determined direction while the thermodilatable part lengthens and shortens in another direction. In addition, this force transmitting element or another element can constitute a multiplying element which causes a displacement of the scraper blade substantially equal to a multiple of the distance traveled by the end of the thermodilatable part which is opposite to that which is coupled. to the mounting member.

It is advantageous that the device for heating the thermodilatable part and, if necessary, the device for heating the mounting member, are of at least one type chosen from at least one Joule effect heating element placed in contact thermal with the positioning member, a direct Joule heating device of the positioning member by circulation of an electric current therein, a flame heating device, and a heating device in contact with a heat transfer fluid.

In an advantageous embodiment, the thermodilatable part is flexible, and the device further comprises a spring intended to push the scraper blade in a direction substantially parallel to said determined direction.

• - mesurer directement ou indirectement ladite épaisseur du matériau et former un signal représentatif de cette mesure ;
• - comparer ce signal de mesure à un signal de référence et former un signal de comparaison et
• - en fonction du signal de comparaison, régler le chauffage d'au moins la partie thermodilatable de l'organe de positionnement, entre ses deux emplacements de coopération avec la pièce mobile et avec le support.

The invention is perfectly applicable to the implementation of a method for adjusting the thickness of a material produced continuously on a machine, the latter being of a type which includes a scraping blade movable relative to to a support and mounted at a first location on a positioning member which is itself mounted on a support at a second location, the position of the scraper blade relative to the support influencing said thickness of the material continuously produced. We can indeed by this process:

• - directly or indirectly measuring said thickness of the material and forming a signal representative of this measurement;
• - compare this measurement signal with a reference signal and form a comparison signal and
• - as a function of the comparison signal, regulate the heating of at least the thermodilatable part of the positioning member, between its two locations of cooperation with the moving part and with the support.

The device according to the invention comprising a mounting part and a thermodilatable part, placed on the same side of their point of cooperation, it is advantageously possible to adjust the heating either of the thermodilatable part or of the mounting part, depending on whether the lip should be moved one way or the other.

• la figure 1 est une coupe schématique d'une partie d'une caisse d'arrivée de machine à papier, représentant un dispositif de positionnement de la lèvre mobile de la caisse, selon l'invention ;
• la figure 2 est une coupe détaillée agrandie d'une partie du dispositif de la figure 1 ;
• la figure 3 est analogue à la figure 1 mais représente une variante de dispositif de positionnement selon l'invention ;
• la figure 4 est une coupe schématique partielle analogue à la figure 3, représentant un dispositif de positionnement différentiel selon l'invention ;
• la figure 5 est une coupe schématique analogue à la figure 1 représentant une variante de dispositif de positionnement selon l'invention ;
• la figure 6 est une vue en plan de l'organe de positionnement de l'appareil de la figure 5 ;
• les figures 7 et 8 sont respectivement une élévation frontale et une élévation latérale d'une variante d'organe de positionnement destiné au mode de réalisation de la figure 5 ; et
• la figure 9 est un schéma illustrant la mise en oeuvre de l'invention pour le réglage fin d'une lame d'une coucheuse.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings in which:

• Figure 1 is a schematic section of a portion of a paper machine inlet box, showing a device for positioning the movable lip of the box, according to the invention;
• Figure 2 is an enlarged detailed section of part of the device of Figure 1;
• Figure 3 is similar to Figure 1 but shows a variant of the positioning device according to the invention;
• Figure 4 is a partial schematic section similar to Figure 3, showing a differential positioning device according to the invention;
• Figure 5 is a schematic section similar to Figure 1 showing a variant of the positioning device according to the invention;
• Figure 6 is a plan view of the positioning member of the apparatus of Figure 5;
• Figures 7 and 8 are respectively a front elevation and a side elevation of a variant positioning member for the embodiment of Figure 5; and
• FIG. 9 is a diagram illustrating the implementation of the invention for the fine adjustment of a blade of a coater.

Figures 1 and 2 show an example of a positioning device according to the invention. FIG. 1 represents the mounting of the positioning device in an incoming box of known type and only a part of which is shown, this box having a frame 10. The fibrous suspension blade formed by the box passes between a fixed lip 12, substantially horizontal, and a movable lip 14. The blade is formed on the cylinder 16 at the head of the manufacturing table comprising a metal fabric 18 supported by a support 20 just after the cylinder 16. The end of the movable lip 14 which is the one closest to the manufacturing table is fixed to a tube 22 by an articulation 24. The tube 22 passes through orifices 26 and 28 of organs of the frame 10 of the box. The other end of the tube 22 is fixed to a screw jack 30 controlled by hand by a knurled button 32. The fixed part of the jack is mounted on a support tube 34 fixed to the frame. This tube 34 is pierced with small holes 36 at its upper part.

The positioning device according to the invention comprises the tube 22, the screw jack 30 and the tube 34.

FIG. 2 represents in greater detail the upper part of the tube 22. The interior of the tube contains an electric heating element 38 having wires 40 for connection which pass through an orifice 42 in the wall of the tube 22. A lining 44 of a powder of a material having good thermal conductivity advantageously maintains the heating element 38 in the tube 22. In an exemplary embodiment, the length of the resistor 38 introduced into the tube 22 is 1 m. The tube 22 is itself formed of brass and, when the resistor whose power is equal to 70 W and which is supplied at a voltage of 20 V, operates at its maximum power, the tube reaches a maximum temperature of 90 ° vs. Under these conditions, the variation in length of the tube 22 between these two extreme temperatures is of the order of 1.2 mm. As the thickness of the fibrous suspension blade formed on the manufacturing table is generally between 5 and 40 mm, this adjustment range is entirely satisfactory for the correction of the variations observed during manufacture, when the coarse adjustment was carried out manually under the control of screw jacks 30.

In an incoming box of a modern machine, around sixty positioning devices of the type shown in FIG. 1 can be controlled simultaneously according to the orders transmitted by a computer.

The control of the heating elements of the various positioning devices can be carried out according to the many known techniques, for example by variation of the applied voltage, by variation of the duration of application of a fixed voltage, by variation of the pulse frequency applied or by any other method or combination of control methods well known to those skilled in the art.

In the embodiment of Figure 1, it is obviously desirable that only the tube 22 heats up and that the tube 34 remains at room temperature. As the heat given off in the tube 22 must be removed, the holes 36 formed in the upper part of the tube 34 allow the circulation of an air current passing through the frame 10 and rising in the tube 34 fulfilling only a support function .

Given the relatively large inertia of the tube 22 when it is heated, it takes several minutes for a disturbance to be effectively corrected. Given the continuous mass measurement speeds on paper machines, such a time constant is entirely satisfactory. If it appeared to be too large in certain applications, it could be reduced by using more powerful heating and forced cooling of the tube 22. For example, the latter may carry fins which increase its cooling. In a variant, the tube 22 can be in the form of a double envelope in which circulates a cooling liquid, for example water.

When starting a paper machine having an arrival box provided with positioning devices according to the invention, the movable lip is initially adjusted using the screw jacks 30 so that it is parallel with fixed lip. The paper machine is then put into production. According to the result of the measurement of the weight per square meter, carried out continuously at the end of the machine, a sheet profile is established. The positioning devices being initially cold, the parts of the sheet which are too heavy can be corrected by heating the positioning devices which correspond to these strong points, so that they expand.

Figure 3 is similar to Figure 1 and shows a variant of the positioning device according to the invention. In this variant, the length of the positioning device is shorter than that of the device of FIG. 1. In FIG. 3, the references identical to those of FIG. 1 designate similar elements. Thus, the frame 10 of an arrival box having a fixed lip 12 and a movable lip 14, forming a fibrous suspension blade on the cylinder 16 at the head of a manufacturing table, supports a device positioning device which comprises a tube 46, similar to the tube 22 but much shorter, a screw jack 48 which may be identical to the jack 30 of the embodiment of FIG. 1, and a support tube 50 similar to the tube 34.

In the embodiment of Figure 3, the changes in length of the tube are not transmitted directly to the movable blade 14 but through a connecting rod 54. The latter is articulated at 52 at the end of the tube 46. One end of the connecting rod is articulated at 56 on the frame 10 while the other end is articulated at 58 on a rod 60 which is itself articulated at 62 on the movable lip 14. As shown in FIG. 3 , the distance between the joint 52 of the thermodilatable tube 46 and the joint 56 on the frame 10 is much less than the distance separating the joint 58 from the rod 60 which controls the movement of the lip 14 at the joint 56 In this way, the displacement of the rod 46 is amplified by the connecting rod 54. Since the force which must be applied to the movable lip 14 by a positioning device is at most of the order of 200 N, the force applied by the tube 46 at the joint 52 is only of the order of 600 N, when the multiplication ratio is three. Such a force can be easily applied by a tube of small diameter and small wall thickness.

The essential advantage of the embodiment of Figure 3 compared to that of Figure 1 is a significant reduction in the total length of the positioning device. However, this embodiment has the drawback of introducing mobile elements which can only reduce the reliability of the devices, although these are very simple and very robust mechanisms.

FIG. 4 represents a variant of the device according to the invention ensuring differential positioning. This differential adjustment is represented in its application to the embodiment of FIG. 3, but it should be noted that it also applies generally to all the other embodiments.

More specifically, as shown in Figure 4, the rod 76, corresponding to the rod 46 of the embodiment of Figure 3, is mounted on the screw jack 48 and it passes through the orifice 26 of the frame 10. The tube 50 of support is replaced by a tube 78 which has the same role as the tube 50 but which, moreover, advantageously has a relatively high coefficient of thermal expansion. A heating element 80 in the form of a resistance heating sleeve surrounds the support tube 78. It receives electrical energy from a power supply which is not shown, by wires which are not shown. According to an advantageous characteristic, a thermal insulation sleeve 82 is held between the rod 76 and the support tube 78.

The operation of the embodiment of Figure 4 is as follows. When the controlled lip must be brought closer to the manufacturing table, the rod 76 is heated in the manner described with reference to FIGS. 1 to 3. However, if the lip must be quickly moved away from the manufacturing table, the thermal inertia of the tube 76 prevents rapid return. Under these conditions, the heating element 80 is then supplied and it rapidly heats the support tube 78. This expands and therefore quickly spreads the lip of the manufacturing table. The insulating sleeve 82 improves the thermal decoupling of the tubes 76 and 78.

This embodiment has a much greater sensitivity than those of FIGS. 1 to 3 because it is known that the heating can be much faster than natural cooling. It is therefore an interesting variant which can be used instead of forced cooling of the tube 76.

5 shows a variant of the device of Figure 1. The references 10, 14 and 30 represent the same elements as in Figure 1, namely the frame, the adjustment lip and the screw jack.

This embodiment comprises a flexible type positioning member 84, shown in more detail in FIG. 6, placed in a support tube 86, quite similar to tube 34 or 50. The positioning member 84 has four bands flexible formed of a suitable metal alloy, for example "Kanthal which is used for the formation of electrical resistances and which however has a good mechanical resistance. The ends of the strips 86 are clamped in two supports 88 and 90. The latter has an extension 92 intended to be fixed to the jack 30 while the support 88 has a tab 94 pierced with a hole intended for the passage of a threaded rod protruding a lever 96. The latter is articulated on arms 100 fixed to the frame 10 and on a rod 98 for controlling the lip 14. In addition, a spring 102 is advantageously disposed between the frame and the lever 96 so that it pushes this lever in the direction which causes the application of a traction force to the positioning member 84.

The advantage of the positioning member 84 is that it is heated directly by the Joule effect and therefore has a high sensitivity to heating. In addition, as it is formed by flat strips of small thickness and yet having a large surface area, it cools quickly. The lever 96 represents an example of a force transmission element, but the mounting can also be carried out as shown in FIG. 3, with suitable movement of the spring 102. The arm 100 can be placed in any suitable location so that it gives the desired multiplier ratio, for example equal to 1.

Figures 7 and 8 show a variant of flexible positioning member, similar to the member 84 of Figure 6. In this variant, the member 104 comprises a first end support 106, provided with a tab 108 similar to the lug 94 of the member 84, and another end support 110 provided with a device 112 for mounting on a screw jack. The resistance heating wires 114, having good mechanical resistance that in traction, pass over insulating sleeves carried by screws 116 passing through the support 106 and over other insulating sleeves carried by screws 118 and 120 placed on the other support 110. The wires are held on the support 110 so that they can transmit tensile forces between the two supports 106 and 110. This flexible positioning member 104 can be used in place of the member 84 in the embodiment of FIG. 5, and it has the same benefits as this one.

. FIG. 9 represents another example of application of the invention. This is a very simple diagram of a blade coater. A paper 64 is entrained on a cylinder 68 and a coating roller 66 applies a surface layer of an aqueous dispersion containing for example essentially particles of kaolin and a suitable adhesive. A blade 70 is applied against the paper 64 carried by the cylinder 66 and the regularity of the layer formed requires the application of a certain force to the blade 70. The positioning devices are perfectly suited for this purpose, given their range of setting. There is shown diagrammatically, in FIG. 4, the end of a tube 72 of a positioning device which can be of a type analogous to those which are represented in FIGS. 1 to 4. A joint 74 transmits the force applied by the tube 72 to the blade 70.

Of course, the invention is not limited to the particular embodiments described. Thus, although a horizontal type paper machine has been considered, the invention applies equally well to the adjustment of the movable lip in vertical machines. In addition, the fine adjustment device according to the invention has been described in a form associated with a coarse adjustment device, formed by a screw jack 30 or 48. It should be noted that the invention is also suitable for modern cases, each of which rod is controlled by a geared motor group. In this case, the geared motor unit provides only a coarse adjustment and the heating of the positioning devices according to the invention ensures the fine adjustment.

It should above all be noted that the fine adjustment devices according to the invention are very reliable given their essentially passive nature, do not require maintenance, do not require lubrication, and are particularly inexpensive. The technology necessary for implementing the invention has also been known to those skilled in the art for several decades.

Claims (10)

1. Apparatus for the fine control of the position, relative to a fixed supporting part (10) of a head box of a paper-making machine, of a blade (14) for scraping a fluid from a surface, which blade forms the lip for controlling the thickness of the fibrous suspension layer that will form paper, by displacing the said blade in a predetermined direction, which apparatus comprises :

a positioning means (22, 34) that cooperates at a first point with the support (10) and at a second point (24) with the doctor blade (14),

a device (38) for heating at least one elongate thermodilatable portion (22, 46, 76, 84, 104, 114) of the positioning means, which portion connects the two points of cooperation, and a member for controlling the heating device (38) as a function of the desired position of the doctor blade relative to the support (10), characterised in that the positioning means comprises two elements of which only the first element forms the said thermodilatable portion (22, 46, 76, 84, 104, 114), one end of which is connected to the first point mentioned above via the second element of the positioning means, this element, which is also elongate, serving as a mounting means (34, 50, 78, 86), one end of which is fixed to the said first point while its other end is connected to the other end of the thermodilatable portion (22, 46, 76, 84, 104, 114), this end being located, when viewed from the second point (24, 62), beyond the said first point, and the said mounting means (34, 50, 78, 86) being parallel to the said thermodilatable portion (22, 46, 76, 84, 104, 114), this end being located, when viewed from the second point (24, 62), beyond the said first point, and the said mounting means (34, 50, 78, 86) being parallel to the said thermodilatable portion (22, 46, 76, 84, 104, 114).

2. Apparatus according to claim 1, characterised in that the thermodilatable portion is connected to the mounting means by means of a coarse-control device (30), for example a manual lifting screw, for altering the distance between the two points of cooperation.

3. Apparatus according to claim 1, characterised in that the mounting means (34, 78) is tubular.

4. Apparatus according to claim 1, characterised in that the mounting means (34) is cooled, especially by convection or circulation of a cooling fluid.

5. Apparatus according to claim 3, characterised in that the above-mentioned mounting means (78) comprises a heating device (80).

6. Apparatus according to claim 5, characterised in that it also comprises a heat insulation device (82) that is located between the mounting means (78) and the thermodilatable portion (76).

7. Apparatus according to any one of claims 1 to 6, characterised in that the positioning means also comprises a power transmission element for causing the displacement of the doctor blade in the said predetermined direction, while the thermodilatable portion expands and contracts in another direction.

8. Apparatus according to any one of claims 1 to 6, characterised in that it also comprises a multiplying element (54) that causes a displacement of the doctor blade (14) that is substantially equal to a multiple of the distance covered by the end of the thermodilatable portion (46) that is opposite the end connected to the mounting means (50).

9. Apparatus according to any one of the preceding claims, characterised in that the device (38) for heating the thermodilatable portion and, if appropriate, the device (80) for heating the mounting means are included in the group that comprises at least a Joule-effect heating element that is in thermal contact with the positioning means, a device for heating the positioning means directly, by the Joule effect, by passing an electric current through that means, a flame heating device and a device for heating by contact with a heat-exchanging liquid.

10. Apparatus according to any one of the preceding claims, characterised in that it also comprises a resilient device (102) for pushing back the doctor blade (14) in a direction substantially parallel to the said predetermined direction.

Images