Patent Publication Number: US-2016221202-A1

Title: Coated and recessed industrial paper knife

Description:
TECHNICAL FIELD 
     This invention relates to an improved industrial knife, preferably a paper knife used to cut and/or trim stacked media, where the media can contain adhesives and other sticky compounds. More particularly, my invention is directed to an industrial knife that is coated with a low friction coating and has a recess above the cutting blade that, in combination with the low friction coating, greatly reduces adhesive build-up on the knife face, improves cut quality, and blade longevity. This disclosure also presents a method of retrofitting existing industrial knives to include the features disclosed herein for use in O.E.M. cutting machines. 
     BACKGROUND 
     Non-rotary cutting single edged knifes for trimming media, such as paper products, are known to those skilled in the art of industrial paper cutting. Such media more frequently now contain adhesives and other sticky substances that are released when a lift of the media is cut or trimmed. Lifts of media can range from a thickness of from about 1 inch to about 6-8 inches. For example, adhesive-backed media is commonly used in the printing of labels, barcodes, laminates, books, magazines, and the like which are attached to an object after printing. Unfortunately, cutting adhesive-backed media is particularly troublesome in that the adhesive material is released during the cutting operation and adheres to the knife blade surfaces. Gradually the sticky substances causing gumming on the knife faces over time resulting in a number of operational problems, for example, degradation of the quality of the cut over the life of the blade where a complete cut is no longer possible. Also, the released adhesive can foul or gum-up the moving parts of the cutting machine. The adhesive build-up on the blades may also cause the cut media to stick to the cutting edge, which can ruin the visual appearance of the finished cut product. Correcting this adhesive build-up problem typically requires operator intervention to conduct multiple knife change outs resulting in lost production time of from 30 to 60 minutes. With typical machinery producing anywhere between about 1,000 to about 10,000 cuts per hour, frequent knife change outs for replacement or cleaning are very costly. Further, although straightforward in function, paper cutting machines typically include complex assemblies with numerous parts, which makes knife change outs time consuming. 
     Accordingly, a need exists for an improved industrial knife design that reduces adhesive build-up on the knife faces during a production run, minimizes machine downtime due to less knife change outs, and improves the quality of the cut media. My industrial knife design, as described herein, achieves these goals and overcomes the above-mentioned problems by providing a combination of a coated knife blade having a recess in the top portion of the knife face to allow adhesive build-up to accumulate away from the blade face and cutting edge. Improved cut quality and blade longevity is possible while cutting paper made from wood, synthetic paper and films because the improved blade disclosed herein generates less friction and accordingly less deflection. 
     These and other advantages of the invention will become evident from the following more detailed description of the invention. 
     SUMMARY 
     My invention substantially reduces the amount of build-up of adhesives and other sticky substances from the cutting blade faces of an industrial knife, preferably paper knives. Build-up of sticky material on the cutting blade can result in fouling of both the knife and the cutting machine to which it is attached. This results in frequent and costly change out downtime as the blade is cleaned or replaced. In some instances, repair or cleaning of the cutting machine itself may also be needed. 
     An object of my invention is to configure the knife such that any adhesive from the cut media is transferred to locations on the knife so as not to interfere with the performance of either the knife itself or the combination of the knife and the cutting machine. 
     The above object is accomplished by the combination of two features of my industrial knife design. First is the use of non-stick or low friction coating applied to selected portions of the knife and second is incorporating a recess or cut-out in the knife face, preferably above the cutting blade portions of the knife Accordingly, one possible embodiment of my improved industrial knife for use in a trimming or cutting machine comprises a generally rectangular metal stock having a length L and a width W. The bottom section of the metal stock contains two blade portions or faces, one on the front beveled side and one on the back cutting side. The front beveled side comprises a bottom blade face that is beveled to an angle of less than 90 degrees as measured relative to a longitudinal axis that runs parallel to width W of the knife. A low friction coating is adhered to the outer surface of the bottom blade face. The back cutting side comprises a lower blade face and an upper end portion, where the upper end portion is recessed from the lower blade face to define a collection surface. A low friction coating is present on an outer surface of the lower end face and also on the collection surface. 
     Another possible embodiment of my invention includes a method of retrofitting an existing industrial paper knife to reduce adhesive build-up during use. This method comprises starting with an existing industrial knife that is configured as a metal stock having a length L and a width W with blade faces on the front beveled side and on the back cutting side. The front beveled side comprises a bottom blade face that is beveled to an angle of less than 90 degrees as measured relative to a longitudinal axis that is parallel to width W of the knife. The back cutting side comprises a lower blade face and an upper end portion, both of which lie in a single vertical plane. The back cutting side is flat and has no recess or other cut-out in the upper end section. My method further comprises removing a section of the upper end portion of the back cutting side to form a collection surface that defines a vertical plane that does not lie in the plane defined by the lower blade face. Preferably the two planes are parallel to each other. 
     Once the collection surface is formed, a low friction coating is then applied to the outer surface of the bottom blade face of the front beveled side, to the outer surface of the lower blade face and to the collection surface. 
     These as well as other possible embodiments and features of the various aspects of my industrial knife design will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Exemplary embodiments are described herein with reference to the drawings, in which: 
         FIG. 1  illustrates a front view of one possible embodiment of my industrial knife disclosed herein showing the front beveled side with a low friction coating applied to the lower blade face; 
         FIG. 2  illustrates a back view of the knife illustrated in  FIG. 1  showing the opposite back cutting side having a low friction coating applied thereto and a recess above the lower blade face; 
         FIG. 3  illustrates a cross-sectional view of the knife illustrated in  FIG. 1  and showing the collection surface on the upper portion of the back cutting side along with the areas of the knife coated with the low friction coatings; 
         FIG. 4  illustrates one embodiment of my industrial knife mounted on a schematic representation of an industrial cutting machine and indicating a general directional path of the knife in operation; and 
         FIG. 5  illustrates the embodiment of the knife of  FIG. 1  schematically represented in a side view cutting operation of media position on a cutting machine. 
     
    
    
     DETAILED DESCRIPTION 
     One possible configuration of the knife assembly of the present invention is shown in the accompanying figures.  FIGS. 1 and 2  show respectively the back and front sides of one embodiment of the industrial knife  10  of my disclosure. The knife is preferably made from metal stock material having a width W, a length L and a thickness T 1  (see  FIG. 3 ). Preferably, length L is in the range from about  6  inches to about  165  inches and W is in the range from about 2 inches to about 24 inches. The knife is preferably is fabricated from carbon steel, D-2, high-speed steel, carbide inlaid material, ceramics and other similar hardened materials. 
       FIG. 1  shows a front beveled side  20  and  FIG. 2  shows the back cutting side  30  of knife  10 . Through holes  1  are located in the upper sections  2  of both sides. These through hole are configured to allow an attachment feature  3 , such as a screw or bolt, to pass through the knife to allow the knife to be mounted on a cutting machine as illustrated in  FIG. 4 . Each side of knife  10  has a blade face on the lower portion of the knife shown as bottom blade faces  21  and  31 . The bottom blade face  21  of front beveled side  20  has a beveled edge of width BW. This beveled edge is angled with respect to longitudinal axis  50 . As best illustrated in  FIG. 3 , the angle θ of the beveled bottom blade face  21  is preferably less than 90 degrees as measured relative to a longitudinal axis  50  that is parallel to width W of knife  10 . A preferred angle θ is in the range from about 10 degrees to about 40 degrees and most preferably from about 18 to about 30 degrees. The bottom blade faces  21  and  31  join together at the bottom of knife  10  terminating in a sharp cutting edge  35 . The width BW of bottom blade face  21  can be in the range from about 0.5 inches to about 2 inches, most preferably 0.75 inches to 1.375 inches. 
     The lower blade face  31  of the back cutting side  30  has a cutting edge width of CEW and can taper inward relative to cutting edge  35  at a taper of from 0.003 to about 0.005 inches measure along the width of knife  10 . The width CEW of the lower blade face  31  can be in the range from about 0.5 inches to about 2 inches, most preferably 0.75 inches to 1.375 inches. The transition between the lower blade face  31  and the upper portion  2  is indicated by transition  32 , which is more clearly shown in the side view of  FIG. 3 . For this particular embodiment the transition is approximately a 45 degree transition, however, the transition angle may be more or less depending on the method used to create the recess  36 . Preferably, CEW is greater than BW and L &gt;H &gt;CEW. In one preferred configuration of the knife  10  the lower blade face  31  of the back cutting side  30  and the collection surface  33  each have a different width measured along the longitudinal axis and where the width of collection surface is at least twice the width of the lower blade face of the back cutting side. 
       FIG. 3  presents a side view of knife  10  that shows a preferred lower blade face  31  comprising a hardened metal insert  34 . This hardened metal can be selected from the group consisting of carbon steel, D-2, high speed steel, tungsten carbide, T 1  (18% tungsten alloy), and ceramics. The insert  14  is preferably attached to a slot or pocket formed in the knife  10  and then held in place by known brazing techniques. The depth of the pocket or slot is deep enough to accept and hold an insert having a thickness of from about 2 to about 3 mm. The use of the hardened insert  34  on the back cutting side of knife  10  allows for easier sharpening of the beveled bottom blade face  21  on the front beveled side  20 . 
       FIG. 3  also illustrates, in an exaggerated thickness, the location of low friction coatings  40 . The same or different coatings can be applied to different areas of the knife provided these coatings each exhibit a low coefficient of friction. Preferred chemical compounds used to form the low friction coatings include fluoroplastic resins, preferably one or more selected from the group consisting of PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene copolymer), PFA (perfluoroalkoxy), ETFE (a copolymer of ethylene and tetrafluoroethylene), and dry lubricant coatings that are designed to provide lubrication under high-pressure/velocity (PV) conditions. Such dry lubricant coatings are solvent-based, one-coat systems that are usually cured between 500° F. and 700° F. Yet other low friction coating can be made using one or more of these fluoroplastic compounds that are mixed with other high-performance resins to improve toughness and abrasion resistance. Typically, to form the low friction coatings the fluoroplastic compounds must be applied to the knife and then baked or cured at high temperatures to adhere the low friction coating to the knife surfaces. Before adding the coating, the surface of the recess  36  is roughened, for example by grit or sand blasting, to allow for good adherence of the coating and to remove any oils or other substances that would interfere with the coating. A preferred thickness of the coating is from about 1 mil to about 2 mils, however, the maximum amount of applied coating is a function of the gap clearance between the installed knife and the clamp on the cutting machine (see  FIG. 5 ). Too thick a coating can cause the knife to rub against the clamp during the cutting machine oeration. 
     The thickness of knife  10  can vary from width T 1  to T 2 , where T 2  &lt;T 1 , as best shown in  FIG. 3 . This variable thickness is a function of the extent of the depth of the recess or cut-out section  36  on the back cutting side  30 . Preferably, T 1  is in the range from about 0.250 inches to about 1.0 inches and the difference between T 1  and T 2  is in the range of from about 0.010 inches to about 0.020 inches. In a preferred design the surface of the lower blade face  31  of the back cutting side  30  defines a plane that is above a plane defined by the collection surface  33 , where the planes are not parallel to each other because of the slight tapering inward of the lower blade face. A preferred method of forming the recess is to use a grinding operation where the metal in the upper portion of the back cutting side  30  is ground down to the desired depth. Depending on depth needed, either grinding equipment or a milling machine could be used to form the recess  36 . The type of operation used to create the recess will typically dictate the angle of transition  32 . The width of the recess must be wide enough to efficiently collect the transferred adhesive. Preferably the recess will extend to the top of the knife as illustrated in  FIG. 3 . 
     Turning next to  FIG. 4 , there is generally shown a cutting machine  100 , preferably a paper cutter, having knife  10  mounted thereon through fasteners  3 . Movable clamp  101  is shown holding down a lift of media  200  supported by table  102  of the cutting machine  100  as knife  10  begins moving downward to make a cut. My industrial knife can be used in cutting machines that operate with only a single knife installed or can be used on multiple knife cutting machines, such as, a three-knife or five-knife book trimming machine. As mentioned, the knife  10  has a plurality of attachment through holes  1  that can be used with appropriate fasteners  3  to removably connect the knife  10  to cutting machine  100 . These through holes may be round holes, slots, grooves, or other attachment means that are configured to align and cooperate with similar means or fasteners located on the cutting machine. Preferably, when attached to a cutting machine  100  the knife is operated in a reciprocal manner, as opposed to a rotary manner. In other words, the cutting machine causes the knife assembly to move in a radial “up and down” cutting motion from left to right (or from right to left), as opposed to a rotational direction like that of an electric table or radial arm saw blade. This cutting motion is generally shown by directional arrow  103 . 
     Turning now to  FIG. 5 , which schematically represents a cross-sectional view of one embodiment of my industrial knife as it would be generally positioned in a cutting machine, there is clamp  101  to exert a clamping force in the direction  110  to hold media  200  in a fixed position as knife  10  is also moved downward left to right (or right to left) slicing motion at a prefixed angle. The positioning of knife  10  relative to clamp  101  is such that there is an abutment between the front side  105  of clamp  101  and the coated cutting surface  38  of the bottom blade face  31 . A gap  112 , shown exaggerated in  FIG. 5 , exists between the front side  105  of clamp  101  and the recess  36 . Accumulated adhesive residue  115  is shown collecting on the collection surface  33 . As the blade  38  makes repeated cuts during the up and down motion, the released adhesive from the media that sticks to the knife  10  and collects on the blade surface  38  will be pushed, scraped or otherwise forced off of blade surface  38  and moved into the recess  36  and deposited on collection surface  33  as adhesive residue  115 . Likewise, any adhesive  116  that might stick to blade surface  28  on the front cutting side  20  of knife  10  will be pushed or otherwise transferred in the direction indicated by directional arrow  117  to the non-beveled front of knife  10  as illustrated by the collected adhesive residue  118 . The movement or transfer of the adhesive residue from blade surfaces  38  and  28  is a direct result of the low friction coating  40 . Because of the low friction coating any build-up of the adhesive on the collection surface can be easy wipe of from the coated surfaces using a rag and small amount of solvent without the need for dissembling the knife from the cutting machine. The clamp  101  and the knife  10  are perpendicular to the lift of media  200  during the cutting or trimming operation. 
     Exemplary embodiments of the present invention have been described. Those skilled in the art will understand, however, that changes and modifications may be made to these embodiments without departing from the true scope and spirit of the present invention, which is defined by the claims.