Abstract:
A valve assembly includes a digitally controlled piston residing in a cylinder interior of a cylinder, and provides a linear flow rate versus piston position. Ink is pumped into a housing interior containing the cylinder. The ink flows from the housing interior into the cylinder interior through a tapered orifice in the cylinder, then from the cylinder interior to a printing press. The tapered orifice is aligned with the direction of travel of the piston and the position of the piston in the valve body is controlled by a stepper motor to determine how much of the tapered orifice is uncovered by the piston. The tapered orifice is designed to compensate for a pressure drop in the housing interior as the valve assembly opens to allow more flow, and results in the linear relationship between the piston position and the flow rate through the orifice.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to valves and in particular to an ink valve for a printing press, the ink valve providing a linear relationship between a valve position and an ink flow through the valve. 
         [0002]    Printing presses require a controlled flow of ink based on varying speeds of the printing press, and what is being printed. Known valves used to control the flow of ink open and close an arbitrary orifice, and generally, the amount of opening of the orifice is linearly related to the degree of actuation of the valve. Unfortunately, as the valve is opened and the flow through the valve increases, a pressure drop in the source of the ink flow results in a less than linear flow rate through the valve. Further, as computers and software become commonly used to control the flow of ink, the non-linear flow characteristics of known valves result in requirements for complicated software and introduce sources of error into the control of the ink flow. 
         [0003]    Further, known valves include a large number of moving parts, and these moving parts continue to move even after a printing press has reached a constant operating speed. As a result, parts often wear out or prematurely fail. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    The present invention addresses the above and other needs by providing a valve assembly including a digitally controlled piston residing in a cylinder interior of a cylinder, and provides a linear flow rate versus piston position. Ink is pumped into a housing interior containing the cylinder. The ink flows from the housing interior into the cylinder interior through a tapered orifice in the cylinder, then from the cylinder interior to a printing press. The tapered orifice is aligned with the direction of travel of the piston and the position of the piston in the valve body is controlled by a stepper motor to determine how much of the tapered orifice is uncovered by the piston. The tapered orifice is designed to compensate for a pressure drop in the housing interior as the valve assembly opens to allow more flow, and results in the linear relationship between the piston position and the flow rate through the orifice. The piston is precisely linearly or angularly positioned in the valve body by a stepper motor to control how much of the orifice is uncovered and thereby control the flow rate of ink through the valve assembly. The stepper motor is controlled by computers and software developed to make very precise changes to the position of the piston so as to supply the correct amount of ink to a printing press for the different printing requirements. 
         [0005]    In accordance with one aspect of the invention, there is provided a printing press inker assembly comprising a pump, a stepper motor, and an inker assembly housing containing a cylinder and a piston for regulating flow. A first ink line provides an inflow of ink to the pump and inker assembly housing receives the inflow of ink from the pump. The cylinder has a first cylinder end and a second cylinder end opposite the first cylinder end, wherein the cylinder interior is in fluid communication with a second ink line through the second cylinder end. Two tapered orifices reside in opposite sides of the cylinder and provide fluid communication between the housing interior and the cylinder interior, the orifices having a narrow end pointed toward the second cylinder end. The piston slidably resides in the cylinder interior and is linearly actuable through the first cylinder end, wherein the piston is slidable to adjust an overlap of the piston with the tapered orifices to regulate a flow through the orifices into the cylinder interior to provide a regulated outflow. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0006]    The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
           [0007]      FIG. 1  is a digital newspaper press inker assembly according to the present invention. 
           [0008]      FIG. 2  is a cross-sectional view of one valve assembly according to the present invention of the digital newspaper press inker assembly taken along line  2 - 2  of  FIG. 1 . 
           [0009]      FIG. 3A  shows the valve assembly in a partially open state. 
           [0010]      FIG. 3B  shows the valve assembly in a fully open state. 
           [0011]      FIG. 3C  shows the valve assembly in a nearly closed state. 
           [0012]      FIG. 4A  is a side view of a valve cylinder according to the present invention of the valve assembly. 
           [0013]      FIG. 4B  is a cross-sectional view of the valve cylinder according to the present invention of the valve assembly taken along line  4 B- 4 B of  FIG. 4A . 
           [0014]      FIG. 5  is a detailed view of a tapered orifice according to the present invention. 
           [0015]      FIG. 6A  is a side view of a valve piston according to the present invention of the valve assembly. 
           [0016]      FIG. 6B  is an end view of the valve piston according to the present invention of the valve assembly. 
           [0017]      FIG. 7  is a valve cylinder for a rotationally actuated piston. 
           [0018]      FIG. 8A  is an end view of the rotationally actuated piston. 
           [0019]      FIG. 8B  is a side view of the rotationally actuated piston. 
           [0020]      FIG. 9  shows the rotationally actuated piston in the valve cylinder. 
       
    
    
       [0021]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
         [0023]    A digital newspaper press inker assembly  10  according to the present invention is shown in  FIG. 1 . The digital newspaper press inker assembly  10  includes a first ink line  12  providing a flow of ink into the digital newspaper press inker assembly  10 , an inker assembly housing  20 , a pump motor  14 , a 90 degree gear box  16 , a gear drive  17 , linear stepper motors  26 , second ink lines  28 , and an ink rail  30 . The housing comprising a stepper motor end portion  21 , a center portion  22 , an ink outlet end portion  24 , and a manifold portion  23 . The motor  14  is connected to the pumps  18  (see  FIG. 2 ) through a gear box  16  and gear drive  17 . The stepper motors  26  control valves residing in the housing  20  to control a flow of ink to the ink rail  30 . While a stepper motor is preferred, an inker assembly with another type of electrical linear actuator is intended to come within the scope of the present invention. An example of a suitable linear actuator is 35000 Series Size 14 Linear Actuator made by Haydon Switch and Instrument in Waterbury Conn. 
         [0024]    A cross-sectional view of one valve assembly  48  according to the present invention of the digital newspaper press inker assembly  10  is shown in  FIG. 2 . Each assembly  48  includes a valve cylinder  32  with an orifice  50 , and a valve piston  34  residing in a cylinder interior  51  of the valve cylinder  32 . First O-rings  36   a  and  36   b  from a seal between the cylinder  32  and the housing  20 , and a second O-ring  37  forms a seal between the piston  34  and the cylinder  32 . An ink inflow  44  enters the manifold  23  through the line  12  and passes through a low pressure side passage  19   a  in the manifold  23  to the pump  18 , back through a high pressure side passage  19   b  in the manifold  23  and into a housing interior  49  of the housing  20 , through the orifice  50  to the cylinder interior  51  of the cylinder  32 , and from the cylinder interior  51  to a line  46  as a controlled outflow  46 . Each valve assembly  48  preferably includes it&#39;s own gear pump  18 , and all of the gear pumps  18  are preferably driven from the gear drive  17  (see  FIG. 1 ). 
         [0025]    The position of the piston  34  within the cylinder  32  is controlled by the stepper motor  26  to adjust amount of the orifice  50  covered by the piston  34  to regulate the flow of ink through the valve assembly  48 . The orifice  50  is precisely tapered so that a linear relationship exists between the piston position and the flow of ink. A non-tapered orifice would result in a non-linear relationship because as the piston  34  is moved to uncover more of the orifice  50  and produce a higher flow rate, pressure within the housing  20  would drop, and the flow of ink would not increase proportionally to piston position. The orifice is thus tapered to compensate for pressure drop as the flow rate increases. 
         [0026]    The manifold  23  includes a pressure control system for regulating pressure of the flow of ink to the housing interior  49  to provide uniform control of the flow of ink through the valve. The pressure control system preferably comprises a bypass passage  80  intersecting the high pressure side passage  19   b  between the pump  18  and the housing interior  49 . A ball  82  is biased against a seat  81  in the bypass passage  80  by a spring  83  to seal the bypass passage  80 . The spring  83  is selected to allow the ball  82  to back away from the seat  81  resulting in a bleed-off flow  84  through bleed-off line  85  to return the ink to a reservoir thereby regulating the pressure in the high pressure side passage  19   b.    
         [0027]    A cutaway view of the valve assembly  48  is shown in a partially open state in  FIG. 3A , in a fully open state in  FIG. 3B , and in a nearly closed state in  FIG. 3C , thus showing the affect of piston  34  position in the cylinder  32 . 
         [0028]    A detailed side view of the valve cylinder  32  according to the present invention is shown in  FIG. 4A , and a cross-sectional view of the valve cylinder  23  taken along line  4 B- 4 B of  FIG. 4A  is shown in  FIG. 4B . The cylinder  32  has two o-ring grooves  60   a  and  60   b  for the o-rings  36   a  and  36   b  (see  FIG. 2 ). The cylinder has a cylinder length L 1 , cylinder outside diameter D 1 , and cylinder inside diameter D 2 . The length L 1  is preferably approximately 1.533 inches, the diameter D 1  is preferably approximately 0.7491 inches, and the diameter D 2  is preferably between approximately 0.3953 inches and approximately 0.3954 inches. The two tapered orifices  50  residing in opposite sides of the cylinder  32  includes a precision tapered portions  54  and round openings  52  at a wide end  50   b  (see  FIG. 5 ) of the orifice. The piston  34  enters the cylinder  32  through a first cylinder end  32   a  and the tapered orifice  50  resides towards a second cylinder end  32   b  with a narrow end  50   a  of the tapered orifice pointed toward the second end  32   b.    
         [0029]    A detailed view of the tapered orifice  50  according to the present invention is shown in  FIG. 5 . The orifice narrow end  50   a  has a width W 1  and the wide end  50   b  has a width W 1 . The length of the tapered portion  54  (measured from the narrow end  50   a  to the center of the round portion  52 ) is L 2 , and the diameter of the round portion  52  is D 3 . The length L 3  from the narrow end  50   a  to the wide end  50   b  is L 3 . The width W 1  is preferably between approximately 0.0045 inches and approximately 0.0055 inches and is more preferably approximately 0.0050 inches. The width W 2  is preferably between approximately 0.0135 inches and approximately 0.0145 inches and is more preferably approximately 0.0140 inches. The length L 2  is preferably approximately 0.515 inches, the length L 3  is preferably approximately 0.468 inches, and the diameter D 3  is preferably approximately 0.094 inches. Although one orifice  50  is shown in  FIG. 4A , the dimensions described above apply to a cylinder  32  having a second orifice  50  of the same dimensions residing on an opposite side of the cylinder  32 . 
         [0030]    The preferred dimensions for the tapered orifice  50  were developed for a pump  18  supplying approximately 140 grams of ink per minute at a pressure of approximately 40 PSI to each valve assembly  48 . The ink flow of approximately 140 grams of ink per minute at a pressure of approximately 40 PSI is the maximum flow targeted for each printing press inker assembly  48  to be able to supply to the printing press. To obtain a greater maximum ink flow from the same pump, the tapered orifice  50  dimensions may be increased. To obtain a lessor maximum ink flow from the same pump, the tapered orifice  50  dimensions may be decreased. Regardless of a requirement for more or less ink flow, the tapered orifice  50  is designed to start out narrow and linearly increase in width to compensate for a pressure drop as the valve is opened (i.e., piston moved), to produce a flow linear with the piston  34  position. The maximum flow of ink flow thru the valve assembly  48  may also be changed by increasing or reducing the ink supply pressure. The pumps  18  are preferably common gear pumps used in known printing press inker assemblies and may comprise a separate pump for each valve assembly  48  or a single pump with the pump output distributed to the valve assembly  48 , or some arrangement of more than one pump and a distribution manifold for the pumps. 
         [0031]    The round portion  52  of the orifice  50  is initially drilled to allow Electrical Discharge Machining (EDM) wire to be fed into the cylinder  32  to cut the precision tapered portion  54  of the orifice  50 . Additionally, the circular opening provides a large flow area for purging ink from the valve. 
         [0032]    A side view of a valve piston  34  according to the present invention is shown in  FIG. 6A  and an end view of the valve piston  34  is shown in  FIG. 6B . The piston  34  includes an o-ring groove  60   c  for the o-ring  37  (see  FIG. 2 ). The piston  34  has a piston length L 4 , a piston outside diameter D 4 , and a stepper motor shaft mouth  64 . The length L 4  is preferably approximately 0.923 inches and the diameter D 4  is preferably approximately 0.395 inches. The mouth  64  preferably accepts a threaded stepper motor shaft and is more preferably a M 3  by 0.5 by 0.35 threaded mouth. 
         [0033]    Other sized cylinder interior diameters D 2  and piston diameters D 4  may be used, and preferably the diameter D 2  is between approximately 0.0003 inches and approximately 0.0004 inches greater than the diameter D 4 . Further, when other diameters are used, the thickness between the outside cylinder diameter D 1  and the inside cylinder diameter D 2  is preferably approximately 0.1769 inches. 
         [0034]    While preferred dimensions and components have been described herein, various combinations of orifice width and length, cylinder inside diameter and piston outside diameter, pump, and actuator may be used to provide a linear flow rate with piston position. Therefore, while the orifice dimensions provided herein are suitable for the pump and linear actuator described therein, other orifices may be empirically determined for other pumps and actuators, and any valve assembly having a tapered orifice providing such linear relationship is intended to come within the scope of the present invention. 
         [0035]    A second valve cylinder  32 ′ for a rotationally actuated piston  34 ′ is shown in  FIG. 7 , a side view of the rotationally actuated piston  34 ′ is shown in  FIG. 8A , an end view of the rotationally actuated piston  34 ′ is shown in  FIG. 8B , and a view of the piston  34 ′ (drawn in phantom lines) in the cylinder  32 ′ is shown in  FIG. 9 . The cylinder  32 ′ includes an angularly extending tapered orifice  50  and the piston  34 ′ includes a cutout portion  70  for cooperation with the angularly extending tapered orifice  50 . Thus, angular actuation, for example by an angular stepper motor, results in the piston  34 ′ overlapping more or less of the angularly extending tapered orifice  50  and thereby regulating the outflow  46  of the valve assembly. 
         [0036]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.