Patent Publication Number: US-6991682-B2

Title: Applicator plate for an adhesive applicator of a core-making machine

Description:
BACKGROUND 
   This invention relates to adhesive applicators for core-making machines. More particularly, the invention relates to an applicator plate which applies a uniform thickness of adhesive to a web which moves below the applicator plate. 
   In the paper converting art, a web of tissue or paper is wound on a rotating tubular core to form an elongated log. The log is thereafter transversely severed at multiple locations to form individual rolls of paper products, for example, bathroom tissue or kitchen towels. 
   The hollow cores are made on a core-making machine. In the present art of core-making machines, two or more fibrous webs are wound on a mandrel and bonded together with adhesive to form a continuous tube. The tube is subsequently cut to a desired length. 
   The adhesive applicator of a core-making machine typically consists of a wheel which is partially submerged in an adhesive bath. The wheel picks up, carries, and transfers adhesive to a web as the web wraps the wheel. Excess adhesive is removed to leave a thin layer for subsequent bonding of the webs. 
   The problem with this type of system is that the method which is used to remove excess adhesive requires adjustment as the speed of the machine is varied. Machine speed is also limited to a relatively low level. 
   Core-making machines using a wheel for applying adhesive are described in U.S. Pat. Nos. 1,846,707, 1,913,447, and 2,931,278. European Patent EP 0 993 367 B1 describes an alternate method of applying adhesive in a separate operation and then “activating” the adhesive when the core is made. 
   Spraymation, Inc. of 5320 N.W. 35th Avenue, Fort Lauderdale, Fla. 33309-6314 markets a slot coater adhesive system which includes an adhesive applicator, an adhesive pumping system, and controls. It was believed that the Spraymation system could solve the problem of adjusting the system as speed was varied and the problem of low limit on machine speed and could also reduce the quantity of adhesive required for proper bonding. 
   The discharge end of the Spraymation adhesive applicator comprises an applicator head and a slot plate. Adhesive is dispensed through an opening between the applicator head and the slot plate. The adhesive applicator is adjusted to contact the web for proper adhesive lay-down. 
   However, the use of the Spraymation applicator caused other problems. There are various grades of fibrous material used in core-making. Some grades release more fiber particles during the core-making process than others. The fiber particles collect at various locations on the core-making machine and require periodic clean-up—typically at each shift change. When the particles come into contact with the adhesive, which is also in contact with the slot plate, small beads of adhesive and particles begin to form on the downstream side of the slot plate. As these beads grow in size, streaks are formed on the web. The streak is a mark or line on the web at which the amount of adhesive is reduced or eliminated, resulting in a non-uniform adhesive lay-down. As the streak quantity and size increases, the quality of the core or tube diminishes, eventually causing production loss downstream within the core-making machine or in other downstream machinery. The core-making machine must be stopped and the slot plate and its opening must be cleaned. 
   SUMMARY OF THE INVENTION 
   The invention provides an improved applicator plate for the applicator head. The bottom of the applicator plate which contacts the fibrous web material ends in the direction of web travel in a narrow wedge-shaped or knife-like edge. The knife-like edge does not permit a thick accumulation of adhesive and particles, only a thin, light layer that does not create streaking. The layer breaks off harmlessly after reaching about 0.25 to 0.50 inch in length. 

   
     DESCRIPTION OF THE DRAWING 
     The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing in which— 
       FIG. 1  illustrates a prior art wheel-type adhesive applicator; 
       FIG. 2  illustrates an adhesive applicator with a slot coater adhesive system; 
       FIG. 3  illustrates the Spraymation adhesive applicator; 
       FIG. 4  is a fragmentary sectional view of the Spraymation adhesive applicator; 
       FIG. 5  is an enlarged fragmentary view of a portion of  FIG. 4  showing the build-up of adhesive and fibrous particles on the downstream side of the slot plate; 
       FIG. 6  is a perspective view of the inventive applicator plate; 
       FIG. 7  is an elevational view of the applicator plate of  FIG. 6 ; 
       FIG. 8  is an end elevational view of the applicator plate of  FIG. 7 ; and 
       FIG. 9  is an enlarged fragmentary view similar to  FIG. 5  showing the inventive applicator plate and a very small amount of build-up of adhesive and particles. 
   

   DESCRIPTION OF SPECIFIC EMBODIMENT 
   Referring first to  FIG. 1 , a prior art adhesive applicator  15  includes a glue stand  16 , an adhesive pan  17 , and an applicator wheel  18  which is rotatably mounted in the adhesive pan. A web W is guided by rollers  19  and wraps a portion of the wheel  18 . As the web travels over the wheel, the wheel rotates, picks up adhesive from the adhesive pan, and applies the adhesive to the web. A doctor blade  20  removes excess adhesive from the web. 
     FIG. 2  illustrates an adhesive applicator  25  which is equipped with a slot coater adhesive applicator  26 . A web W is guided by a web guide  27  into the adhesive applicator  26  which applies adhesive to the web. 
   Referring to  FIG. 3 , a slot coater adhesive applicator  28  includes an applicator head  29  and a slot plate  30 . The slot plate is attached to the applicator head by bolts  31 . Adhesive is dispensed through a slot  32  between the slot plate and the applicator head to the web which travels in the direction of the arrow A. 
     FIG. 4  is a cross sectional view of the adhesive applicator  28 . Adhesive flows from one internal passage  35  through a second internal passage  36  in the applicator head to the slot plate  30 . Adhesive flows downwardly through the slot  32 , and a layer  37  of adhesive is applied to the web W as the web moves past the bottom of the slot plate. 
     FIG. 5  illustrates the build-up of a bead  38  of contamination which comprises adhesive and fibrous particles. Such beads form on the downstream face of the slot plate. As the beads grow in size, streaks are formed in the adhesive on the web. 
   Referring to  FIGS. 6–8 , an improved applicator plate  40  includes upstream and downstream faces  41  and  42 , top and bottom faces  43  and  44 , and side faces  45  and  46 . Four bolt holes  47  extend through the plate for attaching the plate to the applicator head  29 . Two pin holes  48  permit the plate to be easily located on the applicator head for securing with the bolts. 
   The upstream face  41  of the plate includes a flat top portion  50  and a pair of flat side portions  51  and  52  ( FIG. 7 ) which extend to the bottom face  44 . A recess  53  is formed in the upstream face to allow adhesive to flow between the plate and the applicator head. 
   The downstream face  42  includes a flat top portion  55  which is parallel to the upstream face and an angled bottom portion  56 . 
   The bottom face  44  is flat and extends from the upstream face  41  beyond the bottom portion  56  of the upstream face. A wedge-shaped or knife-like projection  58  is formed by the bottom face  44  and an upper surface  59  ( FIG. 9 ). In the preferred embodiment, the upper surface  59  extends at an angle B relative to the plane of the bottom face  44 . The angle B is advantageously within the range of about 10° to about 20° and most preferably is 15°. The thickness t of the knife-like projection  58  at the downstream edge  60  in the preferred embodiment was 0.009±0.002 inch. However, the thickness of the edge can range from a point to about 0.025 inch. 
   One specific embodiment of the plate  40  had a length L of 4.5 inches, a height H of 1.0 inch, and width w of 0.220 inch. The bottom face  44  had a total width w 1  of 0.090 inch, and the width w 2  of the knife-like projection  58  which extends beyond the angled bottom portion  56  was 0.040 inch. The angled bottom portion  56  had a height h of 0.375 inch and extended at an angle C with respect to the upper surface of the projection  58  of 90°. The recess  53  had a depth d of 0.008±0.001 inch. 
   The foregoing dimensions of the specific embodiment can be varied. For example, the width w 1  of the bottom face can be within the range of 0.070 to 0.160 inch, and the width w 2  of the projection  58  can be within the range of 0.030 to 0.110 inch. 
   The thickness of the projection  58  at the downstream face  56  is within the range of about 0.005 to about 0.065 inch. The thinnest value is provided when w 1 =0.070 inch, w 2 =0.030 inch, t=0, and B=10°. The thickest value is provided when w 1 =0.160 inch, w 2 =0.110 inch, t=0.025 inch, and B=20°. 
     FIG. 9  illustrates the applicator plate  40  mounted on an applicator head  29  for applying a layer  37  of adhesive to a web W which moves past the applicator plate in the direction of the arrow. The pressure on the adhesive in the applicator head in the preferred embodiment is 10 psi, but can be varied from about 8 to 20 psi. The bottom surface of the applicator plate which contacts the adhesive ends in the narrow knife-like downstream portion  58 . The knife-like edge does not permit a thick accumulation of adhesive and fibrous particles, and only a thin light layer  62  of adhesive and particles builds up at the downstream edge of the applicator plate. The layer continuously breaks off harmlessly after reaching about 0.25 to 0.50 inch. The thin light layer of adhesive does not create streaking in the adhesive layer  37  which is applied to the web. 
   The shape of the narrow knife-edge can be achieved in many ways. It only needs to be narrow. Also, it is not necessary for the applicator plate to include the machined recess  53 . The opening for allowing flow of adhesive can be provided in other ways, for example, by a separate piece with a thickness the same as recess  53 . 
   While in the foregoing specification a detailed description of specific embodiments was set forth for the purpose of illustration, it will be understood that many of the details hereingiven may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.