Abstract:
A printing press ink scraping blade is disclosed. The ink scraping blade is of a unitary construction and includes a working end as well as a mounting end. The working end is preferably substantially thicker than the mounting end to provide substantially more material at the working end. As the scraping blade engages a scraping roller of a printing press, the blade is exposed to abrasive action and the additional material provided increases the serviceable life of the blade. To ensure that the blade maintains sufficient flexibility and deflection characteristics, the remainder or mounting end of the blade, is of a substantially reduced thickness. The blade may be manufactured from spring steel to further enhance flexibility.

Description:
FIELD OF THE INVENTION 
     The invention generally relates to printing presses and, more particularly, relates to scraping or doctor blades for use with printing presses. 
     BACKGROUND OF THE INVENTION 
     Keyless printing presses commonly employ a series of rollers, referred to as an ink train, to direct ink from an ink source to a cylinder which applies the ink to a moving web of paper. The series of rollers comprising the ink train, and communicating the ink to the web of paper, accurately meter the ink to ensure that the appropriate amount of ink is transferred to result in an accurate and aesthetically pleasing appearance in the printed text or image. 
     One additional device used to meter the amount of ink transferred to the paper is referred to as a scraping or doctor blade. The blade includes a tip in direct contact with a scraper roller of the ink train to scrape excess ink from the scraper roller. The removed ink is typically directed via gravity into an ink module provided directly below the blade. The removed ink is then recycled back to an applicator device at the beginning of the ink train for ultimate re-application to the web. 
     One difficulty associated with known scraping blades is that both the ink and the roller against which the blade scrapes are abrasive. The material from which the blade is made therefore tends to wear, resulting in a relatively short serviceable life, sometimes as short as forty hours of use. This in turn results in longer downtime for the press, and ultimately in added expense to the operator. 
     An additional factor complicating the situation is that the blade must be deflectable or deformable to ensure the blade maintains contact with the roller throughout its operation. The blade is typically mounted at an angle to the circumferential surface of the ink roller and is mechanically or otherwise biased toward the roller to ensure such contact. In light of such a requirement, the blade typically cannot be manufactured from extremely high hardness or wear resistance materials as such materials typically do not afford the necessary deflection characteristics needed in the blade. 
     Moreover, with known blades the material of the blade can be worn away so quickly, that the air cylinder or similar device biasing the blade toward the scraping roller can push the blade to such a steep angle with respect to the roller circumference that the blade tends to plow the ink, rather than remove the ink. 
     The prior art has provided a number of different types of doctor blades. For example, U.S. Pat. No. 5,638,751, discloses a doctor blade of a stepped construction. More specifically, the doctor blade includes a thin tip portion which transitions into a thicker doctor blade portion, which in turn transitions into a thicker backup or base portion. The variable thicknesses ensure the necessary deflection characteristics in the blade, while the thicker backup portion provides adequate structurally rigidity. However, the thin tip portion is the section of the blade that actually engages the ink roller and, given its thin dimension, wears away relatively quickly. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a printing press ink scraping blade is provided which comprises a base end adapted to be mounted to a printing press, and a working end extending from the base end. The working end includes a scraping tip for engagement with an ink roller. The working end is unitary with the base end and has a thickness greater than the base end. 
     In accordance with another aspect of the invention, a method of fabricating a printing press ink scraping blade is provided which comprises the steps of forming a blank from the deflectable material, creating a bevel into a working end of the blank, and removing material from a base end of the blade to create a unitary scraping blade having a thicker working end than base end. 
     In accordance with another aspect of the invention, a printing press is provided which comprises a frame adapted to carry a web of paper through the printing press, at least one cylinder adapted to imprint ink on the web, an ink train adapted to carry ink to the at least one cylinder, a scraping roller, and a scraping blade in contact with the scraping roller. The scraping blade has a working end and a base end. The working end is integral with, and thicker than, the base end. 
     In accordance with yet another aspect of the invention, an ink scraping blade is provided which comprises a back edge, a front edge, first and second side edges, a bottom surface, and a top surface. The front edge is beveled. The bottom surface is substantially planar. The top surface includes a working end portion proximate the front edge and a mounting end portion proximate the back edge. First and second side edges are thicker adjacent the working end portion than adjacent the mounting end portion. The ink scraping blade is manufactured from a unitary piece of material. 
     These and other aspects and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a printing press constructed in accordance with the teachings of the invention; 
     FIG. 2 is an enlarged side view of a scraping roller and scraping blade constructed in accordance with the teachings of the invention; 
     FIG. 3 is a plan view of a scraping blade constructed in accordance with the teachings of invention; 
     FIG. 4 is a cross sectional view of the scraping blade of FIG. 3 taken along line  4 — 4  of FIG. 3; and 
     FIG. 5 is an enlarged sectional view of the working end of the scraping blade. 
    
    
     While the invention is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and with specific reference to FIG. 1, a printing press constructed in accordance with the teachings of the invention is generally depicted by reference numeral  20 . It is to be understood that the teachings of the invention are primarily directed to the construction of a scraping blade  22 . Accordingly, while the printing press  20  will be described in general terms herein, a complete description of a suitable printing press with which the scraping blade  22  can be operated is disclosed in many of the issued U.S. Patents of the assignee, some of which are U.S. Pat. Nos. 5,806,427; 5,868,071; and 5,943,955, each of which are herein incorporated by reference. 
     As shown briefly in FIG. 1, the printing press  20  includes a frame  24  to which a plurality of cylinders and rollers  26  are rotatably mounted for drawing a web  28  of paper therethrough under tension enabling images to be imprinted thereon. It will be noted that the press  20  is a of keyless design, in that the amount of ink transferred to the paper is not metered by a series of flow control valves or the like, but rather primarily relies upon the ink scraping blade  22  to accurately remove excess ink. 
     Also shown in FIG. 1 is an ink train  30  which directs ink from an applicator  32  to a blanket cylinder  34  and a plate cylinder  35  and back to a scraping roller  36  before removal by the scraping blade  22 . It will be noted that the ink train  30  provides a substantially circular path, indicated by arrow  37  for the ink, as it transverses the ink train  30 . As used herein, the term “ink train” is used to describe a series of rollers or other mechanisms used to carry ink to a cylinder for printing of a moving web, and transporting excess ink back for recycling. Moreover, while the drawings illustrate, and the following text describes, a printing press  20  having a plate cylinder  35  having the desired images thereon, and a blanket cylinder  34  to which ink in the desired image is transformed for application to the web  28 , other configurations, such as those having a single cylinder for direct application to the web  28 , are possible. 
     The applicator  32  of ink train  30 , which can be provided in a plurality of forms including, but not limited to, ink rails and extrusion devices, directs ink to a first roller  38 . Rotation of the first roller  38  directs the ink to a second roller  40  which in turn directs ink to a third roller  42 , and ultimately to an apex roller  44 . The ink from the apex roller  44  is directed in two directions. Primarily, the ink is directed from the apex roller  44  to fifth and sixth rollers  46 ,  48  and thereafter to the plate cylinder  35 . The second direction in which the ink travels is via a return roller  50  which removes excess ink from the apex roller  44 . It is to be understood that in alternative embodiments, only the fifth roller  46 , or additional rollers, may be used to transfer ink to the plate cylinder  34 . 
     From the return roller  50 , ink is transferred to the scraping roller  36  where the ink is scraped therefrom by the scraping blade  22 . Preferably, the scraping roller  36  is covered with hardened rubber, although other suitable materials, including many plastics and metals, are possible. Completing the ink train  30 , it will be noted that an ink module  52  is provided below the ink roller  36 . Ink removed by the scraping blade  22  falls via gravity into the module  52 , whereupon it is directed by a pump  54  or series of pumps, through a hose or conduit  56  back to the applicator  32 . 
     To facilitate removal of ink from the module  52 , a pair of augers  58  are rotatably disposed within the hopper  52 . Each of the augers  58  includes helical splines such that rotation of the augers  58  in opposite direction, causes the ink to be linearly traversed through the hopper  52  toward the pump  54 . In alternative embodiments, more than or less than two augers  58  can be employed. 
     Also shown in FIG. 2 is a mounting bar  60  rotatably mounted within the module  52 . The mounting bar  60  includes a slot or groove  62  into which the scraping blade  22  is inserted. As will be described in further detail herein, the scraping blade  22  includes at least one aperture which cooperates with a locking pin  64  of the mounting bar  60  to mount the blade  22  within the bar  60 . Specifically, it will be noted that the locking pin  64  includes an user engageable handle  66  which is spring biased toward the slot  62 . The user may pull the pin  64  away from the mounting bar  60  to remove the pin  64  from the slot  62  and allow the blade  22  to be removed. Upon release of the handle  66 , the pin  64  is spring biased back across the slot  62  and through the scraping blade  22 . In alternative embodiments, the blade  22  may be secured by other mechanisms including, but not limited to, threaded clamping devices and the like. 
     Preferably, the mounting bar  60  and scraping blade  22  are removably biased toward the scraping roller  36  to ensure adequate contact and removal of the ink. In the preferred embodiment, the mounting bar  60  is so biased by an air cylinder (not shown), but it is to be understood that in alternative embodiments, other biasing means including, but not limited to, springs, hydraulic cylinders and mechanical actuators are possible. 
     Referring now to FIGS. 3 and 4, the scraping blade  22  is shown in detail. As illustrated therein, the scraping blade  22  is primarily rectangular when viewed in two dimensions such as that depicted in FIGS. 3 and 4. The scraping blade  22  includes a front edge  70 , a back edge  72 , first and second side edges  74 ,  76 , a top surface  78  and a bottom surface  80 . The scraping blade  22  also includes two primary zones or ends. A working zone or end  82  is provided proximate the front edge  70 , while a base or mounting end  84  is provided proximate the back edge  72 . As shown best in FIG. 4, the working zone  82  is substantially shorter than the mounting zone  84 . It is within the mounting zone  84 , proximate the back edge  72 , that first and second apertures  86 ,  88  are provided for cooperation with the locking pins  64  as described above. 
     Referring now to FIG. 5, the working end  82  is depicted in further detail. It will be noted that the front edge  70  is beveled. Specifically, the front edge  70  is angled relative to the bottom surface  80  at an angle α. This, among other things, ensures that the scraping blade  22  is able to remove, rather than simply push, the ink from the scraping roller  36 . In the preferred embodiment, α is preferably within the range of approximately 15 degrees to approximately 45 degrees and, in the more preferred embodiment, is approximately 30 degrees. Other angles are certainly possible and encompassed within the scope of the invention. The bevel forms a tip  81  for engagement with the scraping roller  36 . The tip  81 , or the entire blade  22 , may be coated with rust-proofing, such as chrome plating, oil based products. 
     It will also be noted from FIG. 5, that the working end  82  is substantially thicker than the mounting end  84 . This, among other things, ensures that the scraping blade  22  has adequate deflection characteristics, while still providing a greatly enhanced serviceable life. More specifically, the working end  82  includes a thickness β preferably within the range of approximately 0.02 inches to approximately 0.04 inches and, in a more preferred embodiment, is approximately 0.025 inches. It is to be understood that the thickness of the blade  22  can be any other dimension as well and encompassed within the scope of the invention. 
     With regard to the mounting end  84 , its thickness γ is preferably within the range of approximately 0.005 inches to approximately 0.015 inches and, more preferably 0.012 inches. Again, it is to be understood that the thickness of the mounting zone  84 , can be any other dimension as well. However, the inventor has found that the above dimensions are particularly advantageous, and that a ratio of β to γ of approximately 2.0 is desirable. Such dimensions and ratios are particularly applicable when the scraping blade  22  is manufactured from 1095 spring steel. 
     With further regard to dimensions, again referring to FIGS. 3 and 4, the working end  82  is shown to include a width Δ, while the mounting end  84  includes a width Σ. In the preferred embodiment, Σ is preferably within the range of approximately 0.1 inches to approximately 0.3 inches and, more preferably, is approximately 1.32 inches. Also in the preferred embodiment, Δ is preferably within the range of approximately 0.1 inches to 0.3 inches, and is more preferably 0.118 inches. It is to be understood, that in alternative embodiments, alternative dimensions can be employed with similar efficacy, but that a ratio of Δ to Σ being approximately 0.10 is preferable. 
     The scraping blade  22  may be constructed in a variety of manners. One preferred method involves a first step of stamping or otherwise forming a blank from a suitable material, such as the aforementioned 1095 spring steel. For example, a roll of spring steel having the desired width and a thickness corresponding to the desired thickness for the working end, may be stamped or cut into desired lengths. Alternatively, a rectangular dye having the desired dimensions may be directed, as by a hydraulic press or the like, toward a sheet of spring steel stock material to punch out or otherwise remove the blank from the sheet stock material. Such a blank preferably includes the desired thickness β for working end  82 . The stamp may include punches for simultaneously forming the locking apertures  86 ,  88  as well, or such apertures may be separately formed. 
     The beveled tip  81  is then ground into the front edge  70  to the desired angle α indicated above. Such an operation may be performed as by a grinding wheel or the like. The blade  22  may be completed upon removing sufficient material from the mounting end  84  to reduce the mounting end  84  to the desired thickness γ indicated above. Again, such an operation may be performed by a grinding wheel or other abrasive tool. The grinding wheel should be selected to have a radius imparting an arcuate surface  90  to the blade  22  to transition from the working end  82  to the mounting end  84 . This, among other things, tends to increase structural integrity of the blade  22 . A preferred radius for the above-referenced dimensions is approximately 0.5 millimeters although other dimensions are certainly possible. Moreover, the inventor has found that the grinding process should remove the spring steel in small increments, on the order of 0.001 inches per pass of the grinding wheel. This also tends to maintain the structural integrity of the blade  22 . 
     From the foregoing, it will be understood by one of ordinary skill in the art that the teachings of the invention can be employed to construct a scraping blade having improved deflection characteristics as well as an enhanced serviceable life. Specifically, the relatively thin nature of the working end of the blade ensures the blade is able to bend and deflect for contact with the ink roller especially when the blade is manufactured from spring steel, while the enhanced thickness of the working end and unitary construction of the working end with the base end ensure enhanced operation time of the blade prior to replacement.