Abstract:
A metering rod assembly including a body for accommodating a metering rod insert and configured to clamp the metering rod and/or metering rod insert without the use of an auxiliary clamping device, such as a pressure tube or the like. A rod bed insert is supported in a tapered channel of a body whereby a clamping action is created during use. In another embodiment, the body includes a hinge portion that facilitates relative rotation between upper and lower jaws to create a clamping action during use.

Description:
CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS 
       [0001]    This application claims priority to and the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/681,397, filed Aug. 9, 2012, which application is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present application relates to the general field of paper manufacturing. It relates in particular to metering rod assemblies used in the chemical treatment of paper during various coating processes. 
         [0003]    During the coating process, a coating or metering rod assembly lays against a high speed transfer roller. A generous chemical coating is applied to the transfer roller. Excess coating is removed by the metering rod assembly leaving only a thin film of chemical treatment or coating on the transfer roller. Then the coating is transferred to a web. In some instances, an excess amount of coating is applied directly to the web and then the excess is removed with the metering rod. 
         [0004]    The metering rod assembly includes a body having a rod channel (rod holder) that is designed to receive a metering rod (sometimes referred to as a doctor blade). The metering rod is generally, but not always, small in diameter and can be very long in length (up to 15 meters). During the coating process, the metering rod primarily controls the coating film thickness. In addition, the rod is rotated within the rod channel to provide uniform wear along the circumference of the rod. 
         [0005]    Both metering rods and rod holders are wear parts that have service lives, depending on the application, anywhere from a few hours to a few months. The part of the rod holder that typically wears out is called a cradle and includes the rod channel in which the metering rod rotates. As the metering rod rotates, friction between the metering rod and the cradle, combined with sometimes abrasive coatings and other factors, causes the “lips” of the rod holder cradle to wear down. 
         [0006]    In some instances, the cradle is included in an insert that is received in the body of the rod assembly. Such inserts allow replacing the cradle without having to replace the entire body resulting in a cost savings to the customer. Known metering rod assemblies utilizing an insert have generally required replacement of a conventional body with a body designed to accommodate an insert. A body configured to accommodate an insert generally will include one or more features designed to enable clamping the insert in the body to reduce or eliminate vibration and/or unintended separation of the insert from the body. For example, pneumatic clamping tubes are often supported by the body and used for securing an insert in a channel or groove of the body. Such clamping tubes can be pressurized to achieve a variable clamping effect on a metering rod. 
         [0007]    While metering rod assemblies utilizing inserts and clamping pressure tubes have met with commercial success, the addition of clamping pressure tubes to the metering rod assemblies complicates the device, increases cost, and can result in an increased risk of operator errors or equipment failure. In addition, upgrading a metering rod assembly to accommodate an insert with the variable clamping features described above typically requires replacing the body of the assembly with a body equipped with a clamping pressure tube, and plumbing pneumatic lines to the body to inflate the pressure tube, and a control unit. This increases costs and complexity of metering rod assemblies. 
       BRIEF DESCRIPTION 
       [0008]    The present disclosure sets forth a metering rod assembly including a body for accommodating a metering rod insert and configured to clamp the metering rod and/or metering rod insert without the use of an auxiliary clamping device, such as a pressure tube or the like. 
         [0009]    In accordance with one aspect, a metering rod assembly for supporting a metering rod in compressive engagement with an associated roller of a paper machine comprises a base member mountable to a support, the base member having a channel opening to a first face thereof and having first and second side walls spaced about a central plane of the channel, and a rod bed insert at least partially received in the channel of the base member, the rod bed insert having a metering rod slot for receiving a metering rod. When a metering rod is installed in the metering rod slot, a force applied parallel to the central plane placing the metering rod in compressive engagement with the associated roller urges said side walls towards each other thereby clamping the rod bed insert in the channel of the base member. 
         [0010]    At least one of the first and second side walls of the channel can extend at a non-zero angle relative to the central plane of the channel in a taper fit manner, whereby as the metering rod urges the rod bed insert deeper into the channel the first and second side walls of the base member clamp the rod bed insert in the channel. The rod bed insert can be configured to be closely received in the channel, first and second side walls of the insert having a mating shape to the first and second side walls of the channel. The rod bed insert can include a necked down portion thereof connecting the first and second side walls of the rod bed insert. The base member can further include a mount portion adapted to be secured to a support, a head portion, and a hinge portion connecting the mounting portion and the head portion. The assembly can further comprise a pressure tube for applying the force to the head portion of the base member, the pressure tube operative to compressively engage a metering rod with the associated roller and urge said side walls of the channel towards each other thereby clamping the rod bed insert in the channel of the base member. 
         [0011]    The metering rod insert can include a retaining element adapted to cooperate with a corresponding retaining element of the base member to restrict separation of the metering rod insert from the base member. The retaining elements can include at least one protrusion and at least one recess into which the protrusion is received. The metering rod insert can include at least one tab including the at least one protrusion. At least one of the base member or the rod bed insert can be comprised of a resilient material. The assembly can further comprise a pressure tube for applying the force to the base member, the pressure tube operative to compressively engage a metering rod with the associated roller and clamp the rod bed insert in the base member. 
         [0012]    In accordance with another aspect, a method of securing a metering rod in a metering rod base member comprises the steps of providing a base member mountable to a support, the base member having a channel opening to a first face thereof and having first and second side walls spaced about a central plane of the channel, inserting a rod bed insert at least partially in the channel of the base member, the rod bed insert having a metering rod slot for receiving a metering rod, inserting a metering rod in the metering rod slot of the rod bed insert, and applying a force parallel to the central plane to thereby place the metering rod in compressive engagement with an associated roll, whereby the side walls of the rod bed insert are urged towards each other thereby clamping the rod bed insert in the channel of the base member. 
         [0013]    In accordance with yet another aspect, a metering rod assembly for supporting a metering rod in compressive engagement with an associated roll of a paper machine comprises a base member including a channel opening to a first face thereof and having first and second side walls spaced about a central plane of the channel, a mount portion adapted to be secured to a support, a head portion, and a hinge portion connecting the mounting portion and the head portion, and a rod bed insert at least partially received in the channel of the base member, the rod bed insert having a metering rod slot for receiving a metering rod. When a metering rod is installed in the metering rod slot, a force applied to the head portion in a direction parallel to the central plane placing the metering rod in compressive engagement with the associated roll urges said side walls towards each other thereby clamping the rod bed insert in the channel of the base member. 
         [0014]    The rod bed insert can include a necked down portion thereof connecting the first and second side walls of the rod bed insert. The metering rod insert can include a retaining element adapted to cooperate with a corresponding retaining element of the base member to restrict separation of the metering rod insert from the base member. The retaining elements can include at least one protrusion and at least one recess into which the protrusion is received. The metering rod insert can include at least one tab including the at least one protrusion. The base member can be comprised of a resilient material. The assembly can further comprise a pressure tube for applying the force to the head portion of the base member, the pressure tube operative to compressively engage a metering rod with the associated roll and urge said side walls of the channel towards each other thereby clamping the rod bed insert in the channel of the base member. 
         [0015]    Metering rod assemblies in accordance with the present disclosure include a replaceable rod bed insert that can be clamped to varying degrees without needing to provide a separate clamping pressure tube or the like. The disclosure sets forth a metering rod assembly that can be retrofit to existing machines without the need to plumb additional pneumatic lines and/or provide an additional controller, etc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The following is a brief description of the drawings, which are presented for the purpose of illustrating the exemplary embodiments disclosed herein and not for the purpose of limiting the same. 
           [0017]      FIG. 1  is a cross-section of an exemplary metering rod assembly in accordance with the present disclosure; 
           [0018]      FIG. 2  is a cross-sectional view of a portion of the metering rod assembly of  FIG. 1 ; 
           [0019]      FIG. 3  is an exploded perspective view of several components of the exemplary metering rod assembly; 
           [0020]      FIG. 4  is a cross-sectional view of another exemplary metering rod assembly in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    With reference to  FIG. 1 , a metering rod assembly is illustrated and identified generally by reference numeral  10 . The metering rod assembly  10  is illustrated as a component of a machine for applying a coating to paper during a paper manufacturing process. It will be appreciated that the metering rod assembly  10  is supported by a support  12  adjacent a roller  14  which advances a web of paper  16  between the metering rod assembly  10  and the roller  14 . Although not shown, it is well known that an applicator is generally provided upstream of the metering rod assembly  10  for applying a coating liquid to the web  16 . The coating is applied in excess and the metering rod assembly  10  is utilized to remove excess coating from the web  16  to achieve a desired coating thickness. The metering rod assembly  10  generally includes a base member  30  that is mounted to the support  12 . 
         [0022]    With additional reference to  FIGS. 2 and 3 , the base member  30  includes a channel  34  opening to a face or surface  36  thereof. The channel is generally defined by first and second sidewalls  40   a  and  40   b  that are spaced about a central plane A-A of the channel  34 . In this embodiment, the first and second side walls  40   a  and  40   b  of the channel  34  extend at a non-zero angle  41  relative to a central plane A-A of the channel  34  such that the mouth of the channel  34  is wider than a base portion of the channel  34 . The channel  34  further includes upper and lower retention slots  42   a  and  42   b  for receiving corresponding retention elements on a rod bed insert, as will be described below. 
         [0023]    A rod bed insert  46  is received in the channel  34  and includes a metering rod slot  50  in which a metering rod  54  is supported. The rod bed insert  46  is configured to be closely received within the channel  34 , with first and second sidewalls  56   a  and  56   b  of the insert  46  have a mating shape and slope to the first and second side walls  40 A and  40 B of the channel  34 . The rod bed insert  46  includes a narrow or necked-down portion  57  connecting the first and second sidewalls  56   a  and  56   b  allowing the insert  46  to flex about the necked-down portion  57  to accommodate insertion and/or removal of the metering rod  54  from the metering rod slot  50 . 
         [0024]    The rod bed insert  46  includes a pair of tab portions  58   a  and  58   b  that serve as retaining elements when the rod bed insert  46  is inserted in the channel  34 . As best seen in  FIGS. 1 and 2 , the retention tabs  58   a  and  58   b  extend into corresponding retention slots  42   a  and  42   b  at the base of the channel  34 . Once the tabs  58   a  and  58   b  are secured in the slots  42   a  and  42   b,  the interference between the tabs  58   a  and  58   b  and the base member  30  restricts withdrawal of the rod bed insert  46  from the channel  34 . 
         [0025]    Returning to  FIG. 1 , a pressure tube  60  is supported adjacent the base member  30  and configured to apply a force along the plane A-A to place the metering rod  54  in compressing engagement with the roller  14 , as is conventional. In the illustrated embodiment, the pressure tube  60  acts along the plane A-A. The pressure tube  60  can also be configured to apply pressure along a plane offset from the plane A-A. Unlike prior art metering rod assemblies, a single pressure tube is utilized to not only place the metering rod  54  into compressive engagement with the roller  14 , but also to clamp the metering rod  54  and/or rod bed insert  46  in the base member  30 . 
         [0026]    To this end, it will be appreciated that when force is applied to a rear surface  64  of the base member  30 , the force is transmitted through the base member  30  and rod bed insert  46  to the metering rod  54 . A reactive force is applied to the metering rod  54  by the roller  14  which tends to force the metering rod  54  deeper into the rod bed insert  46 . The net effect is that surfaces  40   a  and  40   b  are urged towards each other thereby clamping the rod bed insert  46  and/or metering rod  54  in the channel  34  of the base member  30 . As the force urges the insert  46  deeper into the channel  34 , the interaction of the sloping surfaces  56   a  and  56   b  with sloping surfaces  40   a  and  40   b  urges the sides of the insert  46  together gripping the rod more tightly. 
         [0027]    It will be appreciated that, for a given pressure applied to the base member  30  by the pressure tube  60 , the clamping force can be altered by changing the angle of surfaces  40   a  and  40   b  relative to the plane A-A. For example, a relatively shallow angle, such as 20 degrees, will produce more clamping force on the rod bed insert  46  than a relatively steeper angle, such as 40 degrees. Accordingly, depending on the specific application, the clamping effect can be tuned to achieve desired performance. For example, an application requiring light pressure on the metering rod may benefit from a relative steep angle of side walls  40   a  and  40   b  (greater clamping force at lower pressure on the metering rod), while an application requiring higher pressure on the metering rod may benefit from a more shallow angle (less clamping force at higher pressure on the metering rod). 
         [0028]    Turning to  FIG. 4 , another exemplary metering rod assembly is illustrated and identified generally by reference numeral  80 . This embodiment is essentially identical to the metering rod assembly  10  of  FIGS. 1-3 , with the exception of a hinge feature of the base member. Accordingly, the assembly  80  includes a base member  82  having a mounting portion  84  adapted to be secured to a support (not shown), a head portion  86 , and a reduced cross-section hinge portion  88  connecting the head portion  86  and the mounting portion  84 . A rod bed insert  92  is received in a channel  94  of the base member  82  in a similar manner to the rod bed insert  46  of  FIGS. 1-3 . The channel  94  includes first and second side walls  95   a  and  95   b  spaced about an axis or plane B-B. 
         [0029]    In this embodiment, the hinge portion  88  facilitates flexing of the head portion  86  relative to the mounting portion  84  when a force is applied to the head portion  86 , such as by a pressure tube (e.g., pressure tube  60  of  FIG. 1 ). Such flexing generally rotates the head portion  86  counterclockwise relative to the mounting portion  84  such that an upper jaw  96  including side wall  95   a  is urged towards a lower jaw  98  including side wall  95   b  thereby clamping the rod bed insert  92  and/or a metering rod in the channel  94  of the base member  82 . In this embodiment, it may be advantageous to position the pressure tube to apply force to the head portion  86  at a position above plane B-B to increase the levering effect and clamping force generated. 
         [0030]    As with the embodiment of  FIGS. 1-3 , the angle of side surfaces  95   a  and  95   b  relative to plane B-B can dictate the level of clamping force generated when the metering rod assembly is in use. Unlike the previous embodiment, however, the present embodiment optionally allows for elimination of the angled side walls of the channel  94  since the upper jaw  96  is urged towards lower jaw  98  resulting in a clamping effect independent of the clamping effect generated by angled side walls. 
         [0031]    The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.