FI121017B - A beam structure for paper and board making machines and a method for forming it - Google Patents

Description

The present invention relates to a beam structure according to the preamble of claim 1 which is suitable for loaded components controlling various profiles, for example as a support beam for cleaning scraps. The beam structure is particularly well suited as a blade beam for papermaking applicators. Such a blade beam is used, for example, to support and load scrapers and scrapers for the paper industry.

Paper and board are coated by passing a coating composition onto a moving web of material which is applied in a uniform layer on the surface of the web. The coating can be leveled and the amount of coating remaining on the surface of the material web can be adjusted, for example, with a doctor blade or doctor blade. The web to be coated passes between the ka-20 roller and a suitable support, generally a rotating roll, in the coating machine. The blade scrapes off excess coating from the web and smoothes it into a smooth layer on the web surface. In order to make the cover layer as smooth as possible, the gap between the web and the doctor blade should be as close as possible over the entire width of the web. Usually, the blade bar and counter roll are intended to be kept straight. The force exerted on the scraper blade against the web should be large and constant over the width of the blade so that the coating can be uniformly applied to the web, even at high web speeds. The straightness of the cutter bar should remain constant to approximately 0.1 mm. Blade loads, uneven thermal loads due to the environment, loads due to the beam's own weight, and changes in the beam angle all tend to cause significantly greater deflections. The most significant maximum load is usually in the order of 2-3 kN / m, whereby the deflection in wide machines can be up to 1.0 mm with a web width of 8 to 10 m.

5

U.S. Patent No. 4,907,528 discloses a butter-compensated blade bar. In it, four pressure members are arranged symmetrically around a circular frame beam and 10 surrounded by a tube, which in turn is supported by a square scraper frame. By adjusting the pressure of the pressure members, a deformation of the blade beam is caused which compensates for the deflection of the blade beam. The structure of the beam is complicated, which means that it is also very heavy. In this case, the beam's own weight increases its deflection by 15 and requires stronger compensation. The design of the beam is not at the discretion of the designer, since the body of the scraper must be square and the number of pressure members is always four.

20

GB 2 251 562 describes a deflection compensated blade beam in which the temperature of the beam is kept constant at the blade holder and the deflection of the beam is compensated by adjusting the temperature of the beam at appropriate points by means of heating or cooling elements. The deformation of the beam is thus compensated for by causing displacements in opposite directions by means of temperature changes. The blade bar has a triangular cross-section and the heating elements are located on the sides of the triangle. Two separate heat-transfer circuits can be used in the solution, and the heating or cooling is done by the fluid flowing in the ducts. Two heat transfer circuits can be used to change the temperature in different parts of the beam. The problem with such a solution is the slowness of the adjustment, since the masses to be heated are large. The set value may also change as 3 ambient temperatures change.

The heat transfer can also be used merely to keep the temperature of the beam at the setpoint, so that the temperature of the beam does not affect the straightness of the beam. The heating or cooling system is poorly responsive to rapid changes in temperature. Slow response to temperature changes is a weakness of all temperature control compensation methods.

10

U.S. Patent No. 5,269,846 discloses a flex compensated blade beam having a separate inner tube within the blade beam which is supported on the inner walls of the blade beam by air cushions. The deflection of the blade beam is altered by varying the pressure in the air cushions across the inner tube, allowing the blade edge to move as desired. It is possible to use fluid instead of air in the pillows. Such deflection control is fast, making it well suited for modern high speed coating machines. However, the deflection compensated blade beam by air pressure 20 cannot solve all the blade deflection problems. Blade beams today are generally made of steel and have a high coefficient of thermal expansion of steel, which results in uneven heat load causing large deflections in the blade beam. This can be compensated in the above manner by the use of fluid distribution equalizing heat distribution or compressed air compensation. However, the problem with compressed air compensation is that the stiffness of the inner tube is necessarily considerably less than that of the blade bar which is larger in cross-section. Since the stiffness moment of the load-bearing structure strongly depends on the distance of the cross-section from the neutral axis, the load-bearing part of the hollow beam or tubular structure is its shell layer, and the closer the beam is to the center axis. Because the shell of the outer beam is farther away from the center axis of the beam, its load-bearing capacity for stiffness is significantly higher than that of a smaller beam of smaller cross-section. In addition, it should be noted that the blade beam outermost in the structure is dimensioned to carry the loads applied to the beam, so that its rigidity is high initially, as is the wall thickness of the material.

10 In such a situation, the inner tube bends significantly more when loaded with the cutter bar, and only small displacements can be caused to the cutter bar, even if the inner tube bends to the inside surface of the cutter bar. Since the stiffness of the beam and inner tube is strongly determined by the diameter of their cross-section 15, the stiffness of the inner tube cannot be substantially increased as it must fit inside the stern. Thus, the blade beam is significantly stiffer in structure than the inner tube, especially when the specific stiffnesses of the materials used for their manufacture are equal.

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The object of the invention is to provide a new type of beam structure whose outer shell deflection can be better controlled than the current blade beam deflection.

Another object of the invention is to provide a beam structure in which the outer shell is separated from the inner beam by vibration damping elements.

It is an object of one embodiment of the invention to provide a beam structure having an outer shell that protects the inner beam inside of it from heating.

It is a further object of the invention to provide a beam structure which requires less expensive structural materials than the previous beams used for similar applications.

The invention is based on making the beam a double beam having a load-bearing inner tube and an outer shell resting on the inner tube.

According to one embodiment of the invention, the invention is based on the fact that the absolute stiffness of the inner tube is greater than that of the outer shell.

According to one embodiment of the invention, the outer shell is supported on the inner tube by at least one fluid-filled pressure member.

15

According to one embodiment of the invention, the beam structure is a blade bar supporting the scraper blade and at least one support member between the inner tube and the outer shell is disposed so that its direction of action is in a straight line passing through the beam neutral axis and blade tip.

According to one embodiment of the invention, the inner tube is rigidly fixed at its ends to the end brackets and the outer shell is fixed at its ends radially and rotationally with respect to the longitudinal axis of the beam, but in its axial direction torque load or mo-30 to a rigid load bearing structure.

More specifically, the beam structure according to the invention and the method for forming it are characterized by what is stated in the characterizing parts of the independent claims.

The invention provides considerable advantages.

The invention makes it easier to adjust the deflection of the outer shell of the beam as desired. The outer tube, which has a lower stiffness than the inner tube, is easily bent by the inner tube and, when it is movably supported at its ends, does not produce a torque which prevents bending. In this way, the deflection of the outer shell can be easily guided either straight or following a certain curvature, for example according to the curvature of the counter roll. In this way, for example, the gap between the blade and the counter roll is obtained by means of a scraper blade bar and the blade holder only needs to be slightly adjusted to finally set the amount of coating. For this purpose, the positions of the blade bar and blade holder can be directly adjusted based on the coating quantity measurement to obtain the desired amount or profile of coating or other treatment agent for the product being manufactured.

20

The outer casing may be supported on the inner tube by pneumatic or fluid filled hoses or other similar fluid filled actuators. Since the outer shell does not need to be rigid, it does not require high forces to bend, so the surface area and pressure of the supporting members of the shell may be small. This has the advantage that an inner tube with a larger cross-section fits inside the outer casing, thereby increasing its stiffness and better construction. In contrast, the ratio of displacements of the outer shell to the inner tube 30 increases. Fluid-filled tu-tongues also insulate the outer shell from vibrations around it.

The outer casing protects the inner tube from heat and environmental stress. Compensation for temperature changes may not be necessary since no internal temperature gradient is formed in the inner tube which would twist the tube. The inner tube can also be made of a more economical material, such as structural steel, because it is protected from the environment. Otherwise, the structure of the beam is more advantageous than before, because its weight can be reduced by 25% of the currently used blade beam. Because most of this is acid-proof or duplex steel used in the exterior, the savings are significant. The lower total mass, and in particular the lower mass of the damped outer shell, reduces the vibrating mass.

Labor costs and material can be further saved by omitting temperature compensation channels. If necessary, they can be replaced by simple cooling ducts or even air blasting at the end of the beam. Most importantly, there is a constant temperature inside the bar and there is no temperature gradient. The decrease in total temperature and the increase in temperature do not significantly cause deformation and are generally slow and can be easily compensated by bending the outer shell.

The invention will now be explained in more detail with reference to the accompanying drawings.

Figure 1 illustrates one embodiment of the invention in cross section at the end of a beam.

Figure 2 shows the embodiment of Figure 1 in cross section along the longitudinal axis of the beam.

In the following, rigidity refers to the ability of a part or structure to resist deformation when part of the structure is mounted in accordance with the invention. Greater stiffness means less deformation at the same load.

The radial direction of a tube or beam is meant to be transverse to the longitudinal axis of the tube or beam, the tangential direction is the longitudinal axis of the beam or tube (the longitudinal tangent to the outer surface of the shell) and the direction of rotation is transverse to the longitudinal axis.

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In the exemplary embodiment of Figures 1 and 2, the inner tube 1 is circular in cross section, as is the outer shell 2 fitted around it, here formed by a thinner-walled tube larger than the diameter of the inner tube.

Between the inner tube 1 and the outer casing 2 there are three symmetrically located compressed air hoses 3, 4, 5 through which the outer casing 2 is supported on the inner tube 1. The compressed air hoses 3 to 5 allow the outer casing to be bent with the inner tube. The deflection compensation of the beam of the invention by means of compressed air hoses is not described further here as it is well known in the art. Methods of deflection compensation are described, inter alia, in the publications mentioned in the introduction to this specification.

25 The bar shown is a blade bar. The doctor blade 6 is attached to the blade holder 7, which in turn is attached to the outer casing 2. Thus, the position and curvature of the doctor blade 6 can be changed by changing the deflection and position of the outer casing 2.

The inner tube 1 is rigidly secured at both ends to the end flange 9, which in turn is rigidly secured to the beam end brackets 10. The rigid attachment of the inner tube 1 increases its bending stiffness, since the rigid attachment receives the torque load 9 resulting from the bending. The end flange of the inner tube 1 extends beyond its diameter and has a floating outer shell attached thereto so that the outer shell can move in its longitudinal direction, but not transverse to the central or neutral axis 5 of the beam. Thus, the attachment of the outer casing 2 does not receive much of the torque load and allows the outer casing to be bent. The attachment of the inner tube 1 to the end flange can be advantageously done by welding, but other sufficiently rigid connection methods are suitable, for example bolt connection. For ease of installation 10, a recess may be machined into the end flange 9 for the inner tube end. The outer casing may be fitted, for example, into a slot or groove in the end flange 9, the depth of which permits longitudinal movement of the outer casing. At least one side of the end flange 9 and the end supports 10 has openings 15 12, through which the compressed air through a hose having a sufficient mintapaine. Connections for compressed air hoses 3-5 are protected by cover 16.

The end brackets 10 have pivot bearings 11 on which the beam 20 is mounted in use. The pivoting bearings 11 are located in the projections formed in the end brackets 10 so that the pivot point of the bearings and the tip of the doctor blade are on the same line. In this case, the tip of the doctor blade 6 rotates about the pivot point as the beam is rotated. The end brackets 10 also have lugs 13 for beam pivot cylinders to accomplish the above rotation. Since in this beam the outer shell 2 is not the actual load-bearing member, it is more advantageous to fasten the pivoting cylinders to the end flange or most preferably to both end flanges for a symmetrical force. The pivoting cylinders can also be secured to the inner tube, but then the opening or holes must be made in the outer shell. The pivoting cylinder attached to the inner tube also affects the bending of the tube, so this construction is not primarily advantageous.

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The outer shell 2 may be supported in the inner tube 1 in many ways. Instead of compressed air, fluid pressure hoses or pads or even mechanical or piezoelectric actuators 5 can be used. In the simplest case, it is sufficient that the support members are located only at the center of the beam and not over the entire length. The number of support members may vary, but three and four support members already provide transitions in all directions in the beam cross section. The support member-10 met can be positioned other than symmetrically. If more than one support member is used, the cost of the beam will increase, but this may be advantageous in some cases, for example in terms of vibration damping. If one or two support members are used, the support 15 between the inner tube and the outer shell is weakened and the deflection cannot be controlled in all directions.

One essential aspect of the positioning of the support members is that one of the support members 3 to 5 is arranged such that its direction of movement is in a straight line passing through the pivot point 14 of the beam and the beam's neutral axis 15. When the tip 20 of the doctor blade 6 also with this same straight can be adjusted by one support member 5 to adjust the distance of the doctor blade tip from the counter roll or other counter member. In this way, the bar is made to work well with the blade holder 7 in adjusting the operation of the doctor blade. This support member 5 can be located immediately on the opposite side of the te-25 rack 6 behind the outer shell or on the side opposite to the beam's neutral axis.

If four support members are used, they may be in both positions.

The basic idea of the invention is that the load-carrying member of the beam is an inner tube 1 and the deflection of the outer shell 2 surrounding it can be adjusted based on the inner tube. This is achieved by dimensioning the bending stiffness of the inner tube to be greater than the bending stiffness of the outer shell. Usually, the outer casing has been a bearing member in the blade beams and has a wall thickness of about 20 mm and also requires water channels for regulating heat having a material thickness of about 5 mm. the inner tube 5 used for deflection compensation is made of steel with a wall thickness of about 25 mm. Thus, the deflections of the inner tube have been large in relation to the deflections of the outer shell. The invention proceeds from the idea that the load-carrying member is an inner tube and the outer shell serves only to support the actuators attached thereto and to apply the resulting load to the inner tube. The actuators between the inner tube and the outer casing adjust the outer casing deflection, for example, in a conventional manner, or such that the outer casing or actuators attached thereto have the desired curvature to provide proper operation of the actuator. As an example, the doctor blade bar can be used to direct the doctor blade straight or to follow the curvature of the counter roll. Thus, the solution according to the invention is aimed not only at compensating the deflection but rather at the same time at the desired deflection of the outer shell. Now, up to 8 mm wall thickness can be used in the outer casing, and water channels may not be needed, as the temperature inside the outer casing remains constant and the temperature gradients causing deflection are not as easily generated as in previously used structures. If necessary, cooling channels can be provided in the beam 25 for either water cooling or air blowing, but even so the water channels can be made quite light.

The outer casing can be made of any material resistant to load and operating conditions. In practice, useful materials are environmentally resistant steel and various reinforced plastic composites, possibly also aluminum and its alloys. The inner tube is advantageously made of structural steel because of the good stiffness 12 and the low price it provides. The invention as such is not limited to any structural material as long as the structure can be dimensioned with selected materials as set forth in the claims.

5

In the example above, the outer shell and inner tube have a cross section. This is known to be an inexpensive form of manufacturing technology and ready-made structural blanks are readily available. The shape of the beam itself may be any pre-10, such as triangle, square or polygon, and the inner tube and outer tube may have different shapes. Both may be integral tubes or component housing assemblies.

The invention is primarily applicable to a blade bar used for coating paper and cardboard. It can also be used quite well in any other paper or board industry object where straightness or controlled deflection of the beam is required. Such objects include, among other things, curtain coating applicator beams, spray coating nozzle beams and the like, and, in addition to the application formulas, cleaning detergents, e.g.

It is therefore clear from the above examples that numerous solutions other than those described above can be implemented within the scope of the invention. Thus, the invention is not intended to be limited to the above examples, but the full scope of the appended claims should be considered.

Claims (10)

A beam structure for use in paper or board machines capable of implementing a controlled deflection of a beam, comprising: - two end brackets (10), - an inner tube (1) connected at its ends to end brackets (10), - an outer shell (2) arranged around the inner tube and connected at its ends to the end brackets (10), and 15. for supporting the outer shell (2) of at least one support member (3-5) into the inner tube (1), characterized in that the inner tube (1) than the bending stiffness of the outer shell (2). 20 A beam structure according to claim 1, characterized in that the inner tube (1) is rigidly attached to the end brackets (10) so that the torque load is received by the fastening. Beam structure according to claim 1 or 2, characterized in that the outer shell (2) is attached to the end brackets (10) at least axially movably. 30 Beam structure according to claim 1 or 2, characterized in that the outer shell (2) is axially rigidly attached to the end brackets (10). A beam structure according to any one of the preceding claims, characterized in that the outer shell (2) is supported on the inner tube (1) by at least one fluid-filled pressure member. Beam structure according to one of the preceding claims, characterized in that the beam structure is a blade beam supporting the scraper blade (6) and at least one support member (5) between the inner tube (1) and the outer shell (2) is arranged a straight line passing through the beam's neutral axis (15) and the blade (6). 15 A beam structure according to any one of the preceding claims, characterized in that the outer shell (2) is made of environmentally resistant steel and the inner tube (1) is structural steel. 20 Beam structure according to one of claims 1 to 6, characterized in that the outer shell (2) is made of reinforced composite plastic. A beam structure according to any one of the preceding claims, characterized in that the support members (3-5) are three and are disposed symmetrically with respect to the neutral axis of the beam. A method of forming a beam structure for paper or board machines capable of implementing a controlled deflection of a beam, comprising: - making two end brackets (10), - making an inner tube (1) and fitting it at both ends to the end brackets (10), fabricating the outer shell (2) and fitting it around the inner tube (1) and on the end brackets (10), and - supporting the outer shell (2) into the inner tube (1) with at least one tu-10 tongue (3-5). 1) stiffness in the beam structure greater than the stiffness of the outer shell (2).