Abstract:
A scanner for moving sheet materials such as a paper making machine provides the gauging heads which measure parameters such as basis weight and moisture entirely inside an enclosed tubular beam. Each gauging head is driven in a cross direction perpendicular to the moving sheet direction and includes a seal belt for dust and dirt protection by covering a slot in the beam, except where the gauging is located.

Description:
RELATED APPLICATIONS 
     The present application is a continuation in part of No. 09/487,058 filed Jan. 19, 2000, now U.S. Pat. No. 6,253,604. 
    
    
     INTRODUCTION 
     The present invention is directed to a scanner for measuring at least one parameter of a sheet material such as the basis weight or moisture content of paper and, more specifically, to a scanner which has a dust belt which protects a gauging head which is contained entirely within a tubular beam suspended across the sheet material. 
     BACKGROUND OF THE INVENTION 
     For the measurement of the properties or parameters of a moving paper sheet a pair of gauging heads are used which scan the sheet of material in a cross direction (CD) with material moving in a machine direction (MD). The gauging heads themselves are mounted on a pair of spaced upper and lower beams as more fully disclosed or shown in the above pending application. Normally, the gauging heads are external to the beams which are in a cross direction across a moving paper sheet and since the gauging head operates in an extremely hot or moist environment, cooling water or cooled air must be supplied by a separate unit in the beam to the gauging heads. Also, the upper and lower gauging heads must move in perfect synchronism to reduce measurement errors. 
     OBJECT AND SUMMARY OF INVENTION 
     It is a general object of the present invention to provide an improved scanner for measuring at least one parameter of a sheet of moving material. 
     In accordance with the above object, there is provided a scanner for measuring at least one parameter of a sheet of material moving in a machine direction(MD) including gauging head means mounted for cross direction (CD) movement across the sheet, and perpendicular to the MD, from one edge of the sheet to the other comprising at least one tubular beam suspended over or under the sheet in the CD from one the edge to the other, the beam having a continuous slot in the CD in proximity to such sheet to allow the gauging means to measure the parameter. Guide means are inside the tubular beam on which the gauging head means is interiorly mounted for CD movement within the tubular beam, such gauging head means having a face exposed through the slot to the sheet without physical interference for measuring a the parameter of the sheets. Seal belt means are substantially contained within the tubular beam and connected to the gauging head for sealing the length of the slot in the CD to protect the interior of the beam and the gauging head from ambient dust, dirt, and air, the sealing belt means including an opening at the gauging head to allow direct communication, without interference, between the gauging head face and the moving sheets. Means are provided for driving the gauging head in the CD. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a scanner incorporating the invention which is partially cut-away. 
     FIG. 2 is a cut-away top view of FIG.  1 . 
     FIG. 3 is a cross-sectional elevation view of a scanner similar to FIG. 1 but which illustrates a different embodiment. 
     FIG. 4 is a cross-sectional view of FIGS. 1 or  2  but illustrating a modification of the invention. 
     FIG. 5 is cross-sectional view similar to FIG. 4 illustrating another embodiment. 
     FIG. 6 is a cross-sectional view similar to FIG. 5 but illustrating another embodiment of the invention. 
     FIG. 7 is a cross-sectional view similar to FIG. 4 but illustrating another embodiment. 
     FIG. 8 is a cross-sectional view similar to FIG. 4 but illustrating another embodiment of the invention. 
     FIG. 9 is a cross-sectional elevational view similar to FIG. 1 but illustrating another embodiment of the invention. 
     FIG. 10 is a top view of FIG. 9 partially cut away. 
     FIG. 11 is a bottom view of a modification of FIG.  3 . 
     FIG. 12 is a side elevational view partially cut away of a scanner embodying the present invention. 
     FIG. 13 is a diagram useful in understanding the operation of FIG.  12 . 
     FIG. 14 is a top view of a scanner showing another embodiment of the invention which is partially cut away. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a scanner  10  which is suspended in a cross-direction (CD) across a moving sheet material  11  such as paper which is moving in a machine direction (MD) which is perpendicular to the cross-direction in the same plane. Referring also to FIG. 2, a gauging head  12  is mounted for a cross-direction movement across the sheet and is mounted for slideable movement on a pair of rails  13  and  14 . Gauging head  12  is completely contained within the interior of a tubular beam  16 , as illustrated in FIG. 4, and is suspended across the moving paper sheet  1 l. Thus the gauging head  12  moves from one edge of the sheet to the other within the beam. It is protected from the severe heat and moisture environment which is normal in the paper making industry by a seal belt  17  which covers a continuous slot  18  in the bottom of the tubular beam  16 . Gauging head  12  has a face  19  exposed through an opening  21  (FIG. 1) in the belt  17  so that the infrared red light or radiation may pass through the opening and through the sheet to measure, for example, moisture and/or a basis weight. Normally, another gauging head on the other side of the sheet would receive any transmitted radiation or infrared light. 
     Referring back to FIG. 1, the seal belt  17  provides the opening  21  by being fixed at the end points  22  and  23  of the gauging head  12 . The foregoing is more fully discussed in the above U.S. Pat No. 6,253,604. As discussed in that patent, and more fully illustrated in FIG. 12 of this application, the gauging head  12  which normally moves with the sealing belt  17  may also be driven by the motor  28  driving the pulley system  25 . Alternatively, as illustrated in FIG.  1  and FIG. 2, the seal belt  17  may be freely moveable. See the pulley system at  26  which includes a tensioning pulley. Instead the gauging head may be driven by a shaft  27  journaled in the beam in a cross-direction driven by a motor  28  which drives, via a pair of dual pre-loaded ball screw nuts  29 , the gauging head since the ball screw nuts  29  are attached to gauging head  12 . At the end of the motor  28  there may be placed a rotary encoder  31  to determine the location of the gauging heads within a scan. 
     FIG. 3 is an alternative to FIG. 1 where the same type of drive; that is the shaft  27  with the dual pre-loaded screw nuts  29  is utilized for driving the gauging head  12 . However, here the seal belt  17 ′ is actually clamped at the ends of the beam  32  and  33 . In order to provide an opening  21  the belt is looped in a loop  34  via the pulleys  36   a - 36   d  over the rear of the gauging head  12  in the interior of the beam  16 . This effectively provides a suitable opening  21  while still sealing the remainder of the slot in the beam  16 . Roller  36   b  is a seal belt tensioning roller as indicated by the dashed outline. It is spring loaded to maintain tension in the belt; in other words, it is flexibly biased. 
     Referring now to FIG. 4, as well as FIG. 2, the gauging head is normally slideably mounted on the bearings  41 ,  42  and  43  which slide on the rails  13  and  14 . However, the modification of FIG. 4 shows rather than normal bearings such as ball bearings, that magnetic levitation may be used for interacting with the rails. Thus, the bearing blocks  41 ′ and  42 ′ are specially fitted with electromagnetics which are 120 electrical degrees apart in order to provide a magnetic levitation system. 
     FIG. 5 illustrates another type of bearing block in which bearing blocks  41 ′ and  42 ′ include specialty machined air outlets  46  to provide air bearings. These are fed from an air supply  47  mounted within the beam  16 . 
     FIG. 7 illustrates yet another bearing system where, rather than the precision linear rails  13  and  14  illustrated for example in FIG. 2, one rail  48  may be flat and L-shaped and mounted to the interior of the beam  16  and the other rail  49  cantilevered from the side of beam  16 . Then a pair of opposing flat rollers  51  are used to ride on the flat rail  48  and a pair of concave rollers  52  ride on the cantilevered rail  49 . This rail also provides positioning to keep the movement of the gauging heads centered along the slot. 
     Referring now to FIG. 6, this is a cross-sectional view similar to FIG. 4 where however the belt  17 ′ forms a freely moveable loop. Here the gauging head  12  still rides on tubular rails  13 ′ and  14 ′ which are electrically isolated from the beam  16  to allow them to be electrically charged to achieve linear motion. Such linear motion is achieved by the pair of bearing blocks  53  which have specially fitted electromagnetics 120 electrical degrees apart. Thus in a manner similar to that used for magnetic prime motion in the railroad field, the gauging head  12  may be scanned. In other words, a linear motor is provided. 
     FIG. 8 shows yet another suspension system for the gauging head  12  where a faceted rail  54  which is fastened to the bottom of  16  allows the gauging head  12  to be cantilevered by use of a high moment capacity linear bearing  56  attached to the side of the gauging head  12  interacting with the faceted rail  54  to allow it to slide. Seal belt  17  would normally be a driven belt. 
     Now referring to FIGS. 9 and 10, here the sealing belt  17  is freely moveable but the gauging head  12  is scanned in the cross direction by an integrally mounted drive motor  57  which meshes with a linear belt  58  fixed in a cross direction inset in the beam  16 . A tensioning device is provided at the end of belt  58 . The belt may be of a timing belt type with grooves or a roller chain. For the position of the gauging head  12  either a rotary decoder may be used at the end of the freely moveable seal belt  17  indicated at  59  or a sonic linear transducer  61  may be mounted on a tensioned stainless steel band  62  to provide periodic pulses as the gauging head  12  moves along the band  62 . 
     FIG. 11 illustrates an alternative embodiment of the sealing belt  17  where it is still placed in a slot  18 , but it is divided into flexible strips  63  and  64  which extend the length of the slot  18 . The sensor windows of gauging head  12  are provided at opening  66  by use of two pairs of spaced rollers  67  and  68  mounted to the gauging head  12  which spread the strips  63  and  64  apart as the gauging head scans across the moving paper sheet. Appropriate flattening rollers  69  and  70  are attached to the gauging head to again reclose the seal belt. 
     Referring now to FIG. 12 for transmitting infrared information from the gauging head  12 , which would normally contain moisture information, rather than using a flexible continuous cable a mirror  71  may be utilized. See also FIG.  13 . Here the infrared sensor box  72  at the receiver end of the scanner beam transmits an infrared beam  73  which is absorbed by the moving paper sheet and then the amount of attenuation shown by the reflected beam  74 . As discussed above, the gauging head  12  is driven by a combined driving/seal belt  17 , and driven by motor  28  in the pulley system  25 . 
     FIG. 14 shows another information transmission technique for infrared information where rather than transmissions into the air, a fiber optic cable  75  is flexibly mounted to the gauging head  12  and connected to the gauging head optics  76 . 
     In summary, a scanner having an interior gauging head has been provided.