Abstract:
An improved ink cartridge of the type used to dispense ink in automatic lithographic presses. The ink cartridge comprises a hollow cylindrical body for holding a supply of extrudable ink, a plunger and a dispensing fitment. The improvement comprises a valve member mounted over a central aperture in the dispensing fitment and a flexible molded plastic spring that biases the valve member in the closed position. The valve member opens when subjected to pressure from the ink and closes automatically and completely when the ink pressure is less than the biasing force of the flexible spring.

Description:
BACKGROUND 
     1. Field Of The Invention 
     This patent relates to liquid dispensing cartridges for automated dispensing systems. More specifically, this patent relates to an ink cartridge with self-closing valve for use with automatic lithographic presses. 
     2. Description Of The Related Art 
     Lithography is a printmaking process dating back to the 1700s in which ink is applied to a plate having both image and non-image areas. The image areas are ink-receptive and water-repellent. The non-image areas are water-receptive and ink-repellent. In rotary type lithographic presses the ink plate is mounted on a cylinder that rotates during printing. In one typical configuration, the plate cylinder picks up the ink at the image areas and transfers the image to a blanket cylinder, which then transfers the image to the paper. In multi-color sheet-fed type lithographic presses, multiple inking stations are placed in series. Each station has its own ink feeding system and handles a separate color. As the paper sheet moves from station to station, a new color is put down at each station. 
     Because lithographic ink is thixotropic, conventional lithographic ink feeding systems require a complex system of drums, vibrators and fountain rollers to handle and dispense the highly viscous ink. In a typical lithographic ink feeding system, workers remove the ink from a drum (or, in some cases, small tins) with specially made spatulas and spread the ink across a tray (the ink fountain). Fountain rollers roll against the ink fountain to pick up the ink and transfer it to the plate cylinder. The process is labor intensive and subject to error. 
     It is also difficult to store and reuse lithographic ink in drums. The ink is prone to oxidation which can result in color variations from one press run to another, and even from sheet to sheet within a single run. In addition, upon exposure of the ink to the atmosphere, volatile organic compounds (VOCs) evaporate, which can cause ink spoilage. 
     Some modern lithographic printers use specially designed cartridges to dispense ink, such as that described in Rea et al. U.S. Pat. No. 6,192,797. These cartridges are much smaller than drums, being typically nine to thirteen inches long and about three and a half to five inches in diameter. During printing, the ink cartridge moves back and forth across the fountain, dispensing ink into a fountain trough or directly onto an ink form roller. In automated presses, the amount of ink in the trough is continually monitored and replenished as needed. 
     Ink cartridges can be easily filled, transported, used and reused. The cartridge minimizes exposure of the ink to the atmosphere and also minimizes the amount of residual ink left in the cartridge after use. 
     Ink cartridges typically comprise a hollow cylindrical body, a plunger at one end and a dispensing fitment at the opposite end. The cylindrical body is filled with ink. The plunger can move axially within the cylindrical body. The ink is extruded from the dispenser when the plunger is forced toward the dispensing end by, for example, mechanical or pneumatic pressure. 
     The dispensing fitment is mounted in sealing engagement within the dispensing end of the cylindrical body and typically has a valve for opening and closing the cartridge. In the ink cartridge described in U.S. Pat. No. 6,192,797, the valve is recessed below the rim of the cartridge so it does not become damaged during shipment and storage. However, the valve must be manually opened to allow ink to flow, which is time consuming and can lead to error. In addition, valves that stay open until manually closed work poorly with lower viscosity inks because of their tendency to“drool.” This is particularly troublesome in the United States, where inks are made with varying degrees of viscosity. A number of automatic valves have been tried that open and close in response to pressure from the ink, but they tend to remain open when the pressure is decreased, thereby allowing ink to continue to be extruded. 
     Thus there exists a need for an ink cartridge dispensing valve that opens when subjected to pressure from the ink and closes automatically and completely when the pressure is decreased below a certain predetermined level, even when used with lower viscosity inks. The present invention satisfies this need. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved ink cartridge of the type used to dispense ink in automatic lithographic presses. The ink cartridge comprises a hollow cylindrical body for holding a supply of extrudable ink and has a plunger end and a dispensing end. The plunger end is closed by a plunger adapted to act as a piston within the cylindrical body to extrude the contents of the dispenser when the plunger is forced toward the dispensing end by mechanical or pneumatic pressure. The dispensing end is closed by a dispensing fitment affixed to the cylindrical body by glue or other suitable means. The improvement comprises a valve member mounted over a central aperture in the dispensing fitment, the valve member being adapted to open when subjected to pressure from the ink and close automatically and completely when the pressure is decreased below a certain predetermined level. 
     In the improved ink cartridge, a substantially cylindrical nozzle extends from the periphery of the dispensing fitment aperture and terminates in a rim. The nozzle defines a substantially cylindrical space. A flexible molded plastic spring is mounted within the cylindrical space and urges the valve member against the nozzle rim. The spring is bowed rearward in the direction of the plunger when the valve member is in the closed position. The spring has openings to accommodate the flow of ink through or around the spring. 
     The valve member is located downstream of and supported by the spring. The valve member is moveable between a closed position in which the valve member is urged against the nozzle rim by the biasing force of the spring, and an open position in which the valve member is raised above the nozzle rim to create an annular opening when pressure applied by the ink to the spring and to the valve member exceeds the biasing force of the spring. 
     In one embodiment, the valve member comprises a substantially flat disk-shaped portion and prongs extending upward from the disk-shaped portion and through a hole in the spring to secure the valve member to the spring. 
     The plunger comprises a substantially circular disk portion and a sidewall extending from the periphery of the disk portion in a direction away from the dispensing fitment. Preferably, the plunger includes an annular ring protruding from the circular disk portion in the direction of the dispensing fitment. The annular ring has a cylindrical outer wall and a concave inner wall and is adapted to fit around the valve member prongs and within the space defined by the nozzle to minimize ink left in the cartridge when the plunger is fully depressed. 
    
    
     THE DRAWINGS 
     FIG. 1 is a perspective view of an ink cartridge and dispensing fitment according to the present invention, shown with an optional shipping and storage cap mounted over the valve; 
     FIG. 2 is a perspective view of the ink cartridge and dispensing fitment of FIG. 1, shown with an optional nozzle extension mounted over the valve and the valve in the open position; 
     FIG. 3 is a cross-sectional view of the ink cartridge and dispensing fitment of FIG. 1 taken along line  3 — 3 ; 
     FIG. 4 is a cross-sectional view of the ink cartridge and dispensing fitment of FIG. 2 taken along line  4 — 4 ; 
     FIG. 5 is top planar view of the dispensing fitment of FIG. 1, shown with the storage and shipping cap removed; and 
     FIG. 6 is a bottom planar view of the dispensing fitment of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning to the drawings, there is shown in FIGS. 1-4 an ink cartridge  10  of the type used for lithographic printing presses. The ink cartridge  10  comprises a hollow cylindrical body  12 , a plunger  14  mounted in sliding engagement within one end of the cylindrical body  12 , and a dispensing fitment  16  glued or otherwise affixed to the opposite end of the body  12 . 
     In automated lithographic printing presses, the ink cartridge  10  is mounted within a cartridge carriage (not shown) with the dispensing fitment  16  facing down. During operation, the carriage moves laterally along the length of a fountain roller while an ink level sensor constantly monitors the amount of ink in the fountain roller to determine the exact locations where ink is needed. When a low level of ink is detected by the sensor, the controller activates an air supply which forces air against the pneumatically controlled plunger  14  slidingly engaged within the cartridge, which then forces ink onto the fountain roller. 
     The cylindrical body  12  has a plunger (filling) end (not shown) and a dispensing end that terminates in a rim  18 . Preferably, the cylindrical body  12  is made of convolutely wound paper lined internally with polymeric material, although any suitable materials may be used, including, depending on the application, metal or plastic. In practice, the cylindrical body  12  typically is about nine or thirteen inches long, but any suitable length may be used depending on need. 
     The plunger  14  comprises a substantially circular disk portion  20  and a peripheral sidewall  22  extending upward therefrom (upward being defined as the direction away the dispensing end when the plunger  14  is inserted into the plunger end of the cylindrical body  12 ). The plunger  14  is inserted into the filling end of the ink cartridge  10  in sliding engagement with the inner wall of the cylindrical body  12  after the cartridge  10  is filled with ink. 
     A centrally disposed annular ring  24  protrudes from the circular disk  20  toward the dispensing fitment  16 . The annular ring  24  has a substantially cylindrical outer wall  25  and a concave inner wall  26 . and is adapted to fit within the space defined by the dispensing fitment cylindrical nozzle  42  when the plunger is fully depressed. The concave shape of the inner wall  26  is designed to accommodate the upwardly extending prongs  54  of the valve member  50  described below, allowing the plunger  14  to fit flush against the dispensing fitment  16  when the ink is fully dispensed from the cartridge  10 , as shown in FIG. 4, thereby minimizing ink waste. 
     The dispensing fitment  16  is mounted in sealing engagement within the bottom end of the cartridge body  12 . The fitment  16  may be glued to the inner wall of the cartridge body  12  or attached by any other suitable means. The dispensing fitment  16  is generally cup-shaped, and includes a flat covering portion  32 , a sidewall  34  formed around the periphery of the covering portion  32 , and an orifice  38  disposed in covering portion  32  through which ink can flow. A closure flange  36  extends radially outwardly from the bottom end of the sidewall  34 . When the dispensing fitment  20  is fully inserted into the cylindrical body  12 , the closure flange  36  abuts the rim  18  of the cylindrical body  12  to prevent further insertion of the dispensing fitment  16 . The dispensing fitment  16  also has an optional stiffening wall  40  extending downward from the flat covering portion  32  and a substantially cylindrical nozzle  42  extending downward from the perimeter of the orifice  38  but not beyond a plane defined by the bottom surface of the flange  36 . The nozzle  42  defines a substantially cylindrical space and may have a beveled rim  43 . 
     In a key aspect of the invention, a flexible spring means  44  and valve member  50  are mounted within the space defined by the cylindrical nozzle  42 . Preferably, the spring means  44  is formed of molded plastic and is held within an annular groove located along the inside of the nozzle  42 . Alternatively, the spring means  44  may be formed as an integral part of the nozzle  42  and dispensing fitment  16  as shown in the figures. In the illustrated embodiment, the spring means  44  comprises a central portion  46  and bridge portions  48  extending between the central portion  46  and the nozzle  42 . The central portion  46  has an opening therein, the purpose of which will now be explained. 
     A valve member  50  comprises a substantially rigid disk-shaped portion  52  and rearward or upward extending prongs  54 . The valve member  50  is attached to the flexible spring means  44  by inserting the prongs  54  into the opening in the central portion  46  of the flexible spring  44 . The diskshaped portion  52  may have a beveled edge  53  that abuts the beveled rim  43  of the cylindrical nozzle  42  when the valve member  50  is in the closed position. 
     The invention works in the following manner. In its relaxed, non-pressurized state (FIG.  3 ), the flexible spring  44  is concave, that is, bowed rearward (upward) in the direction of the plunger  14  (not shown in FIG.  3 ). When the flexible spring  44  is in this relaxed state, the valve member disk-shaped portion  52  is seated against the beveled edge or rim  43  of the nozzle  42  and ink cannot flow. 
     When pressure is exerted on the plunger  14  (indicated by arrows in FIG.  4 ), the plunger  14  is forced forward (downward) into the cartridge, causing the ink to exert pressure on the spring  44  and on the valve member diskshaped portion  52 . When the ink pressure exceeds the biasing force of the spring  44 , the valve member  50  moves forward, pulling the flexible spring  44  downward, and creating an annular opening  60  between the nozzle rim  43  and the valve disk-shaped portion  52  through which ink can flow, as shown in FIG.  4 . 
     When the ink pressure force decreases below the biasing force of the spring, the flexible spring  44  returns to its original concave position, reseating the valve disk-shaped portion  52  against the nozzle rim  43  and automatically closing the valve. 
     An optional nozzle extension  62  (FIGS. 2 and 4) may be attached to the substantially cylindrical nozzle  42  extending from the dispensing fitment  16  via a snap-fit or other attachment means to help guide the flow of ink. An optional removable cap  64  (FIGS. 1 and 3) may be used to cover the valve member  50  when the cartridge  10  is not is use. 
     Without the optional nozzle extension  62  (but preferably with the optional cap  64  installed), the cartridge can be set on a flat surface with the dispensing end facing down. The cartridge can be stacked this way until ready for use. 
     Thus the present invention provides an ink cartridge having a self-closing valve that opens when subjected to pressure from the ink and closes automatically and completely when the pressure on the valve is decreased below a predetermined level, even when used with lower viscosity inks. The cartridge automatically dispenses ink when the plunger end is depressed, forcing ink through the annular opening  60  between the nozzle  42  and the valve member  50 . When pressure on the plunger is reduced to a predetermined level, the valve automatically and completely closes. The present invention is particularly suitable as an ink dispenser for use with sheet fed lithographic presses having an automatic ink level sensor. 
     Other modifications and alternative embodiments of the invention are contemplated which do not depart from the spirit and scope of the invention as defined by the foregoing teachings and appended claims. It is intended that the claims cover all such modifications that fall within their scope.