Abstract:
A rod-bed assembly has a holder ( 30 ) with a groove ( 31 ) into which an insert ( 20 ) is removably and insertably supported. The assembly has a rod ( 10 ) which is rotatably supported in a recess ( 21 ) on the front side of the insert ( 20 ). The material thickness (T) of the cross-section of the insert ( 20 ) is between 1-5 mm. The invention also relates to a rod -rod-bed assembly.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims priority on European Application No. EP12186205, filed Sep. 27, 2012, the disclosure of which is incorporated by reference herein. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a rod-bed assembly and to be more precise to a rod-bed assembly for a rod of a device for coating or sizing a fiber web, particularly a paper or a board web. The invention also relates to a rod—rod-bed assembly. 
     In this description and in the claims, by term rod-bed assembly is meant the rod-bed comprising an insert and a holder for a rod of a device for coating or sizing a fiber web. The front side of a rod-bed assembly is the side on which the rod is located in use i.e. the side that will face the fiber web to be coated or the sizing roll onto which the sizing agent is applied by the rod when sized. It should be understood that in the prior art publications relating to rod-bed assemblies there exists differences in the terminology used, for example in relation to the feature whether or not the rod is included in the assembly. In practice the rods and the rod-bed assemblies can be supplied to a device for coating or sizing a fiber web from different suppliers or from the same supplier. 
     As known from the prior art in fiber web producing processes, the fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in a process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, or a coating section. The production and treatment line also comprises at least one winder for forming customer rolls as well as a roll packaging apparatus. In this description and the following claims by fiber webs are meant for example paper and board webs. 
     In production of fiber webs, for example of paper or board webs, sizing is used to alter the properties of a fiber web by adding sizing agents (sizing medium), for example glue chemicals. Sizing can be divided to internal sizing and surface sizing. In internal sizing the sizing agent is added to pulp in the wet end of the fiber web machine before forming. In surface sizing the sizing agent is added onto the surface of the fiber web at the dry end of the fiber web machine. 
     In production of fiber webs, for example of paper or board webs, a coating, especially of the surface of a fiber web is formed with a layer of coating paste (coating medium) at a coating station followed by drying. The coating process can be divided in supplying the coating paste onto the web surface, which is called the application of the coating paste, as well as in the adjustment of the final amount of coating paste. 
     The coating or the sizing of a fiber web typically utilizes a coating device—a coater—or a sizing device—a sizer. In connection with the coaters and sizers, different kinds of application technology for application of the coating or the sizing medium on the fiber web are employed in prior art arrangements, for example curtain technology or blade coating technology or rod coating technology or air brush coating technology or spray coating technology. 
     In the coating or sizing based on rod technology rod-bed assemblies are used for the rod or doctor rod functioning as dosing element of the coating or sizing medium, for scraping off the excessive medium quantity, of the sizing or coating medium. In the sizing the rod functions against a roll and in the coating the rod functions against the fiber web. 
     DE 100 45 515 A1 shows one example of a known rod-bed assembly which comprises a holder, a doctor bed made of elastic material inserted into the holder for rods with diameter less than 25 mm and in which the cross section surface of the rod-bed is less than three times the cross section of the doctor rod. 
     EP 1 485 209 A1 shows a further example of a known rod-bed assembly in which a metal doctor rod that has a diameter less than 25 mm is insertable into a rod-bed made of elastomer. The rod-bed insert is inserted into a holding groove of a holder also made of elastomer. 
     EP 1 954 880 A1 shows yet a further example of a known rod-bed assembly in which the rod cradle (the rod-bed) includes a frame profile (holder) equipped with an insert groove, an insert fitted to this equipped with a rod groove, and a rod and locking elements for locking the insert into the frame profile. This known rod-bed assembly is for rods with a diameter of 9-25 mm. 
     WO 2010/142513 shows also an example of a known rod-bed assembly comprising a holder made of composite material, a rod-bed made of polymer and a o doctor rod rotatably supported in a bearing recess on the front side of the rod-bed. 
     The holder is formed such that the rod-bed and the doctor rod are insertable into and removable from a socket provided in the holder in the radial direction of the rod and the rod-bed comprises closed cavities for saving material. This known rod-bed assembly mentions as large rods doctor rods having a diameter of 20 to 25 mm and requiring larger rod-beds and holders. 
     It is a problem of prior art that the rod-bed assemblies are not suitable in cases where rods of diameter over 25 mm are used since space requirements for inserts of rod-bed assemblies that would be suitable for larger rods (i.e. rods with diameter over 25 mm) cannot be realized due to lacking space for locking surfaces, cavities etc. of these known assemblies. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to create a rod-bed assembly especially for larger rods that have a diameter over 25 mm, for example a diameter of 35 mm or 40 mm but which is also suitable for rods with different diameters. 
     Another object of the present invention is to create a rod-bed assembly with simple and fast replacement for the rod and for the insert/rod-bed from the holder as these are wearing parts that need to be replaced at regular intervals. 
     Yet another object of the present invention is to provide a rod-bed assembly in which the rod is securely fastened in the rod-bed during use since a case of unfastening of a rod during use in a device for application of sizing or coating agent would cause serious safety risks and also serious difficulties in the production of the fiber web, possibly the whole production line would need to be stopped. 
     In order to achieve the above objects and to solve the problems of the prior art mentioned above and becoming apparent later, in the rod-bed assembly of the invention the material thickness (T) of the cross-section of an insert positioned between the rod and a rod holder is between 1-5 mm. 
     According to the invention the rod-bed assembly comprises the holder, the insert removably and insertably supported in a groove of the holder, and in which rod-bed assembly a rod of a coating or sizing device is rotatably supported in a recess on the front side of the insert and in which rod-bed assembly the material thickness of the cross-section of the insert is between 1-5 mm. 
     Advantageously the insert is of elastic material or of elastic shape. 
     Advantageously the cross-section of the insert is of substantially even material thickness with the exception of at least one drawdown of decreased thickness for providing elasticity for inserting and removing the insert into and from the holder. 
     Advantageously the cross-section of the insert is of substantially even material thickness with the exception of an advantageous decreased thickness of the tips of water exit channels for providing a passage for water to exit. 
     Advantageously the insert and the rod are insertable and removable from the holder in the radial direction of the rod from the front side of the rod-bed assembly. 
     According to an advantageous feature of the invention the insert is form fitting into the groove of the holder. The fit between the insert and the holder can also be snap-fitting. 
     According to an advantageous feature of the invention the recess of the insert is provided with a round main inner form for locking the rod into the rod-bed assembly when placed into the insert. 
     According to an advantageous feature of the invention the holder is composite material or plastic, preferably of polyethene and the insert is composite material or plastic, preferably of polyethene. 
     According to an advantageous feature of the invention the rod-bed assembly is for rods with a diameter over 25 mm and thus the diameter of the round main inner form of the recess of the insert is over 25 mm corresponding to the diameter of the rod to be inserted. Further the main inner form of the groove of the holder is round and its diameter is correspondingly over 25 mm+the material thickness of the cross-section of the insert. 
     According to an advantageous feature of the invention water exit channels of the rod-bed assembly are of the same or of a different diameter and the diameter of the water exit channel that is lower when the rod-bed assembly is positioned for use is at least the same as the diameter of the water exit channel that is upper when the rod-bed assembly is positioned for use. 
     In the rod-bed assembly the holder is advantageously composite material for providing structural strength, mounting of the rod, holding of the rod, preventing the contamination due to advantageous tight formfitting fit with the insert, holding lubrication water in the water channels, low thermal conductivity and due to its rigidity provides for the possibility of light, low-cost and elastic insert. Further advantages of a composite holder are the thermal durability in process temperatures of coating and sizing, for example over 80° C. 
     In the rod-bed assembly the insert is advantageously of elastic material, preferably plastic material, more advantageously of polyethene providing good friction properties, sufficient thermal properties, and cost-effectiveness due to protecting the holder from wear, easy inserting and removing, and good formfitting. 
     The insert provides a thin shell-like structure inside the holder, which substantially follows the groove from of the holder as an inside layer with cross-sectional material thickness between 1-5 mm, which thickness is substantially even with possible exceptions of decreased material thickness for water channel areas and for elasticity increasing at least one drawdown. The insert provides a removable protection layer inside the holder of the rod-bed assembly and place for the rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention is described in more detail with reference to the accompanying drawings. 
         FIGS. 1A-1C  show schematically one example of rod and rod-bed assembly in a non-assembled state; 
         FIGS. 2A  shows a schematical three dimensional example of the insert according to the invention. 
         FIG. 2B  shows a schematical three dimensional example of the holder according to the invention. 
         FIGS. 3A-3D  show schematically steps of assembling one example of the rod—rod-bed assembly according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description relating to the figures, the same reference signs are used for corresponding parts and part components unless otherwise mentioned. 
     In  FIG. 1A  is schematically shown a cross section of a rod  10  for dosing of coating medium onto the fiber web during coating of the fiber web in a coater or for dosing of sizing medium onto the sizing roll, by which the sizing medium is applied onto the fiber web, during sizing at a sizer. The rod  10  is advantageously of metal and its diameter D is over 25 mm, for example 35 mm or 40 mm. The rod  10  is in this example smooth surfaced but the rod-bed assembly according to the invention is also suitable for grooved rods. The rod  10  will be placed into a recess  21  of an insert  20 , shown in  FIG. 1B , located in a holder  30 , shown in  FIG. 1C  for its use, advantageously inserted in the radial direction of the rod  10  from the front side of the insert and the holder. 
     In  FIG. 1B  is schematically shown an insert  20  of the rod-bed assembly for is holding the rod  10  in its recess  21  that is of mainly round shape, thus corresponding to the cross sectional round shape of the rod  10  and of the corresponding diameter D over 25 mm with tight tolerance in respect of the diameter of the rod. The cross sectional material thickness T of the insert  20  is substantially even with advantageously the exception of the tip parts  22 A,  23 A “Mickey Mouse ears” shaped water exit channels  22 ,  23 , in which tip parts  22 A,  23 A the material thickness is slightly decreased, and with advantageously at least one drawdown  24  with decreased material thickness for providing elasticity for inserting and removing the insert. The material thickness T of the cross-section insert  20  is 1-5 mm and at the tip parts it is 1-4 mm, advantageously 1-3 mm, preferably 1-2 mm. The material of the insert  20  is advantageously polyethene or composite. The water exit channels  22 ,  23  for lubrication water and for providing space for water tubes can be of different diameters, advantageously in the figure the lower channel is bigger but the water exit channels can also be of the same size. For example, the water exit channel  22  is for providing space for a water tube with a 6 mm diameter and the water exit channel  23  is for providing space for a water tube with an 8 mm diameter. 
     In  FIG. 1C  is schematically shown the holder  30  of the rod-bed assembly. The holder  30  has a recess  31  corresponding to the shape of the insert  20  with corresponding formed lug grooves  32 ,  33  for the “Mickey Mouse ears” shaped water exit channels  22 ,  23  of the insert  20 . The lug grooves  32 ,  33  for water exit channels  22 ,  23  of the insert  20  can be of different diameters, advantageously in the figure the lower, i.e. closer to the leg part of the holder  30 , positioned lug groove  33  is bigger, but the lug grooves  32 ,  33  can also be of same size. The size of the recess  31  is corresponding to the space to be taken by the insert  20  with the rod  10  added with the material thickness T so that the insert  20  will accommodate tightly the recess  31  of the holder  30  and to lock the rod  10  when placed. The holder  30  is of composite material or of polyethene. The holder  30  can be attached to the sizer or the coater by manners known as such to one skilled in the art. 
     As can be seen from  FIGS. 2A-2B , the insert  20  and the holder  30  are elongate profiles the length of which will extend at least over the width of the fiber web to be sized or coated, so that the over the same fiber web width extending rod  10  is able to dose the sizing medium or the coating medium on the width of fiber web. 
     In  FIGS. 3A-3D  are shown schematically steps of assembling one example of the rod-bed assembly. As shown in  FIG. 3A , first one side of the insert  20  is inserted into the groove of the holder. The other side of the insert  20  is slightly pressed and simultaneously the insert  20  is further inserted deeper into the groove of the holder  30  as shown in  FIG. 3B . Thereafter the insert  20  is inserted to the groove of the holder  30  such that the insert  20  is located form-fittingly in the groove of the holder  30 , as shown in  FIG. 3C . Finally the rod  10  is pressed in its radial direction into the recess of the insert  20  and the round shape of the rod  10  locks the rod  10  for use, as is apparent from  FIG. 3D . 
     Above the invention has been explained with reference to an advantageous example only to details of which the invention is not to be narrowly limited.