Patent Publication Number: US-8974638-B2

Title: Device for retaining doctor blades

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2012/065875, filed Aug. 14, 2012, which designated the United States and has been published as International Publication No. WO 2013/029989 and which claims the priority of German Patent Application, Serial No. 10 2011 081 927.4, filed Aug. 31, 2011, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for retaining doctor blades with a bottom plate and a top plate, wherein the bottom plate and the top plate are hingedly connected to each other via a pivot bearing and the doctor blade is affixed to the top plate, wherein an expandable tube is provided between the bottom plate and the top plate on each side of the pivot bearing. 
     A scraping device or doctor blade has the task, among others, to clean the surface of a roller or a cylinder. In the case of a paper machine, such a doctor blade has the effect that the paper web guided across the respective roller of the paper machine is not wound up on the roller in the event of a web break, but exits the roller at the predetermined position to reach, for example, a collection tray. This doctor blade must ensure that this task is performed with 100% certainty, since otherwise considerable failures would occur in the papermaking process, possibly even damage the paper machine. The doctor blade also has the task to clean the surface of the roller so that the paper web is not marked. For this reason, the doctor blade attached to its retaining device must be in contact with the roller as uniformly as possible over its entire length. For pressing the doctor blade onto the roller surface, the retaining device is generally constructed in two parts and has a bottom plate which is typically attached on the machine frame. A top plate is pivotally attached on this bottom plate, so that the doctor blade can be lifted off the roller surface, or placed on and pressed against the roller surface (EP 1567715 B1). 
     It has been shown that, especially in the wet parts of the paper machine relatively strongly contaminate the retaining devices, requiring frequent cleaning. For this purpose, the top plate must be removed from the bottom plate so that the retaining device can be opened. WO 2004/042 143 A1 discloses a doctor blade retaining device wherein the bottom plate has a bearing tube and the top plate is pivotally mounted around the bearing tube. To open this retaining device, the top plate is withdrawn in the axial direction from the bearing tube, thereby allowing access to the interior space. With rollers that can have a length of 12 m the retaining device for the doctor blade must also have this length, and it has been found that with such a length, the frictional forces along the bearing tube are relatively large, so that the top plate can be withdrawn or pushed on only with difficulty. 
     WO 2009/076 128 A1 also discloses a retaining device for doctor blades. However, this retaining device is complicated to manufacture since it is made of a continuous casting part, which has to be machined even further. This retaining device also tends to be heavily contaminated. AT 503 922 A4 also shows such retaining device. 
     SUMMARY OF THE INVENTION 
     Starting from EP 1567715 B1, it is an object of the invention to provide a device for retaining doctor blades which can be more easily installed and cleaned and which is also well protected against contamination. 
     This object is attained with a device for retaining a doctor blade, with a bottom plate and a top plate pivotally connected to the bottom plate via a pivot bearing, with the doctor blade being attached to the to plate. The top plate includes a deflection plate pointing toward the bottom plate at a clamping location for the doctor blade. An expandable pressure hose is disposed between the bottom plate and the top plate on each side of the pivot bearing. A radially supported bearing shaft is attached to or formed on either the bottom plate or the top plate, whereas a receptacle for the bearing shaft attached to or formed on either the top plate or the bottom plate, with the bearing shaft and the receptacle forming the pivot bearing. A piping guide chamber is disposed on a side of the top plate facing the doctor blade, and a flexible seal is attached on a side of the bottom plate facing the piping guide chamber and having a free end with piping engaging in the piping guide chamber. The flexible seal and the deflection plate seal a gap formed between the bottom plate and the top plate, wherein the gap extends in a longitudinal direction of the device. 
     By constructing the pivot bearing with a radially supported bearing shaft on the bottom plate or on the top plate and a receptacle for the bearing axis on the top plate or the bottom plate, it is ensured that the bearing shaft remains on one component and the receptacle on the other component when the device is disassembled. This measure has the significant advantage that no extra components are generated during disassembly and no additional components are required during installation. For example, no loose shaft needs to be inserted in receiving eyes on the bottom plate and the top plate after these receiving eyes were brought into alignment. Such operation typically requires a number of tools, such as a retaining device for the top plate, an alignment device for aligning the top plate and bottom plate, and typically several persons monitoring joining of the components. With the device according to the invention, the bearing shaft only needs to be threaded into the receptacle for subsequent complete insertion together with the top plate, without requiring additional tools. The top plate and the bottom plate are then pivotally connected to one another. 
     According to the invention, the top plate has a piping guide chamber located in particular on the opposite side (backside) of the doctor blade. In addition, a flexible seal is fastened on the bottom plate on the side facing the piping guide chamber, with the free end of the flexible seal having a piping engaging with and supported by the piping guide chamber. The seal is formed by a fluid-tight material, such as a rubberized fabric web or another material. One end of this seal extending in the longitudinal direction is affixed on the bottom plate, while the piping disposed on other end is secured in the piping guide chamber of the top plate. The piping can thus be inserted into its piping guide chamber at the same time the bearing shaft is inserted. 
     Furthermore, according to the invention, the top plate may have a deflector plate disposed at the clamping point for the doctor blade and pointing in the direction of the bottom plate, which serves to keep liquids with which the roller is wetted, or dirt away from the interior space. The deflector plate closes or covers the gap facing the roller between the bottom plate and the top plate. 
     In an exemplary embodiment, the bottom plate is formed in the shape of a trough with two side walls. This is used to accommodate additional components, e.g. the pressure hoses for pivoting the top plate and thus for selectively pressing and lifting of the doctor blade. In addition, electric cables or other hydraulic or pneumatic supply lines may be installed in the bottom plate. 
     In a preferred exemplary embodiment, the bottom plate has a substantially W-shaped cross-section. The outer legs form hereby the lateral walls and to protect the interior space of the bottom plate. 
     In a variant of the device that is on the one hand stable and on the other hand inexpensive, the bottom plate is formed by a bent sheet metal profile, in which the bearing axis is integrated by forming. This bottom plate is torsionally stiff and is fast and inexpensive to produce. Since the bottom plate is made as one piece, the interior space is protected without additional measures from below and from the side by way of the side walls against both mechanical effects and intruding media. 
     Preferably, the bearing shaft is formed in substantially Ω-shaped, so that it can also serve as a bearing for a tube which is inserted into the round and hollow opening and then clamped or welded. The tube has a thread and is used for attaching the top plate. 
     In an advantageous embodiment of the invention, the receptacle is shaped as a C that is open in the direction of the bottom plate. The pivot angle is defined by the opening angle of the receptacle, and may optionally be adjusted by lateral supports in the web of the bearing shaft. 
     Trouble-free insertion of the bearing shaft and therefore an easy assembly of the bottom plate and top plate are achieved in that the receptacle extends over the entire length of the top plate or along sections over its length. When the receptacle extends along sections, then the bearing axis needs only be inserted in the first two or three sections of the receptacle, whereafter it is guided by the sections so as to engage in the following sections without requiring tools. This allows a simple cross-exchange. 
     Further advantages, features and details of the invention are evident from the dependent claims and from the following description in which a preferred embodiment is described. The features shown in the drawing and mentioned in the description and in the claims may be essential for the invention severally or in any combination. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the drawings: 
         FIG. 1  shows a perspective view of the retaining device according to the invention; 
         FIG. 2  shows a section II-II according to  FIG. 1 ; 
         FIG. 3  shows the top plate in cross-section, and 
         FIG. 4  shows the bottom plate in cross-section. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a retaining device generally designated with  10 , with a bottom plate  12  and a top plate  14 . Retaining fingers  16  ( FIG. 2 ) with which a doctor blade  18  is held and pressed against the surface  20  of a roller  22  are provided on the top plate  14 . A deflection plate  24  is mounted on the front side of the top plate  14  facing the roller  20 , with the deflection plate  24  overlapping with and shielding the front side wall  26  of the bottom plate  12 , thereby preventing dirt or liquid from entering the intermediate space  28  between the bottom plate  12  and the top plate  14 . A flexible flat seal  32  is screwed onto the side wall  30  of the bottom plate  12  forming the backside, with the free end of the seal  32  having a piping  34  which is inserted into a piping guide chamber  36  disposed on the top plate  14 . In this way, the intermediate space  28  is sealed or at least shielded. 
     As is also evident from  FIG. 4 , the bottom plate  12  is formed from a bent sheet metal profile  38  and is essentially Ω-shaped at its center. Thus, a bearing shaft  40  is formed, in which a tube  42  can be inserted to attach the top plate  14  which can be secured for example by welding. 
       FIG. 3  shows the top plate  14 , which has a receptacle  44  that is slotted at its bottom in its central region in the direction of the bottom plate  12  and serves to receive the bearing shaft  40 . The receptacle  44  and the bearing shaft  40  form a pivot bearing  46  for the top plate  14 , and thus for the doctor blade  18 . Here, the receptacle  44  extends either over the entire length of the top plate  14  or is divided into sections with intermediate free spaces. 
     Two pressure hoses  50  and  52  are disposed in the intermediate space  28  on either side of the pivot bearing  46  for pivoting the top plate  14  relative to an only schematically indicated frame or an adapter strip  49 . A flange  54  with hose clamps  56  is provided for lateral closure of the intermediate space  28  and for connecting the two pressure hoses  50  and  52  to pneumatic or hydraulic lines. The top plate  14  is secured to the bottom plate  12  via a retaining screw  58  which is screwed into end faces of the pipe  42  on both sides of the pivot bearing  46 . 
     The bearing shaft  40  may be continuous, but may also be divided into sections so as to leave spaces between the sections where bolts or screws  60  can be inserted in the bottom plate  12 , via which the bottom plate  12  is affixed to the holder  48 .