Abstract:
An apparatus and method for feeding U.V.-curable inks without causing them to cure prematurely. The apparatus includes plural Moineau style pumps each with an elastomeric stator and a rigid rotor. The pumps are driven by electric motors and flexible drive shafts enabling the stator and rotor to be slight offset from one another. The ink is fed to all of the pumps at the same time from a single trough with baffles therein.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to apparatus and method for feeding a certain class of inks, namely, those which are cured by exposure to Ultra Violet (UV) light, to printing equiment. More particularly, the invention is directed to a method involving using a plurality of so-called progressive cavity apparatus containing plural motors for driving the rotors in a plurality of stator apparatus. In the past, it was not possible to feed U.V. curable inks through the usaual ink feeding apparatus, because the inks would cure or “set up” almost immediately during the feeding process. Hence, in the past U.V.-cured inks simply were never used with existing equipment. 
         [0002]    In the printing business, for example, a typical web printing press may include 4, 8 or even up to 24 ink pumps, for example, which supply the printing ink to plural zones or columns across the width of the paper being printed. The ink pumps of these prior designs used a piston that rotated and reciprocated inside a ported sleeve, and in this manner pushed the ink through the ported sleeve. With the present invention, no reciprocating or rotating pistons are used. 
         [0003]    Here, a plurality of specially designed stators and rotors are used, and each stator and rotor supplies the ink to one zone or column of printing. There, depending on the layout, each rotor-stator pair works independently of any of the other pairs. This means that the ink pumps must ordinarily be closely spaced apart from one another. This is because the space taken up by the ink pumps cannot exceed the width of the printing unit. Also, because the requirements for printing mean that any one zone may have the same, similar, or quite different ink requirements than any other zone, the ink pump system must be able to accommodate each of these different requirements. This was done in one case in the prior art by varying the speed of each individual pump, thus varying the amount of ink pumped depending on the requirements of that column. 
         [0004]    According to the present invention, instead of the piston and sleeve arrangement, the system uses an array of the plural rotor-stator systems of a so-called progressive cavity type. In this system plural eccentric worm rotors working within the respective stators pump individual portions of ink as required to the printing press. For example, these pumps are of the so-called Moineau or progressive cavity type. They use a wormlike rotor which rotates inside a stator having a particularly designed configuration. Such pumps are described in U.S. Pat. No. 6,155,807, issued Dec. 5, 2000 and U.S. Pat. No. 5,472,319, issued Dec. 5, 1995, among many others. The contents of both of these patents are hereby incorporated by reference fully herein, and illustrate the Moineau style pumps. 
         [0005]    According to the instant method, among the unique factors is the way in which these U.V.-cured, usually thixotropic, inks are pumped. U.V.-cured inks cannot be fed or pumped satisfactorily by any other type of pump, because the inks “set up” almost instantly if processed by the usual pumps. The pumps of the invention have so-called progressive cavities formed in a particular shape, from an elastomeric material for the stator, and stainless steel for the rotor, for example. The rotor is characterized as having a single helix pattern and the stator has a double helix pattern, thus accounting for the progressive cavities, as the rotor gyrates within the stators. 
         [0006]    The novel features of the present invention include the manner in which ink is fed to and from each of these progressive cavity pumps, and, in general, the apparatus for controlling the paths followed by such ink. In some embodiments, there is a high frequency, (e.g., 200-800 cycles per minute) low amplitude, intermittent motion of the motors. In other embodiments, there is a low amplitude continuous motion. The different mechanisms all include worm-like single helix rotors and double helix elastomeric stators of appropriate shapes. 
         [0007]    It is therefore an object of the present invention to provide an array of individual Moineau-style pumps spaced closely apart, but independent of one another, to pump a large quantity of U.V.-curable ink toward a multi-column press or other application. 
         [0008]    A further object of the invention is to provide a separate drive for each of plural U.V-curable ink pumps. 
         [0009]    Another object is to provide a pair of novel systems and arrangements for driving eccentric rotary ink pumps with U.V.-cured inks. 
         [0010]    A still further object of the invention is to provide a plurality of similar pump drive mechanisms, wherein an intermittent rotary motion is provided in one direction for the rotor which pump the U.V.-cured ink. 
         [0011]    Another object is to provide an apparatus in which a large quantity of U.V.-cured ink can be placed in an open feeder trough, that is, having baffles subdividing the interior, but having an open bottom for delivery of the ink to the pumps. 
         [0012]    It is also an object of the invention to create a pump system for U.V.-cured inks which use certain classes of materials, namely, a synthetic rubber stator such as Buna-N rubber or vinyl nitride. The rotor may be made from a non-ferrous metal such as stainless steel, or from aluminum, ceramics, or a suitable plastic such as nylon, Kynar or PVDF. Other suitable materials will be known to those skilled in the art. 
         [0013]    Another object of the invention is to provide a progressive cavity apparatus for advancing U.V.-cured inks along a certain path. 
         [0014]    A still further object is to provide an apparatus in which there is a metal worm and a synthetic rubber stator, and the rotor rotates within the stator along a slightly offset path, thereby moving the U.V.-curable ink in a series of progressive cavities. 
         [0015]    Another object is to provide one or more novel systems and arrangements for driving eccentric rotary ink pumps capable of processing U.V-curable inks. 
         [0016]    Another object of the invention is to provide a progressive cavity apparatus for advancing U.V-curable ink along a predetermined path. 
         [0017]    A still further object is to provide an apparatus in which there is a stainless steel worm type rotor and a Buna-N stator, wherein the worm rotates within the stator along a slightly offset path, thereby moving the ink in a series of progressive cavities. 
         [0018]    Another object is to keep the highly viscous, thixotropic inks from accumulating excessively at one side of the trough in response to the rotary motion of the rotor. 
       SUMMARY OF THE INVENTION 
       [0019]    The invention achieves these and other objects by creating a single, unitary apparatus and method which includes using a plurality of single helix, worm-like rotors gyrating inside a plurality of elastomeric double helix passages, a trough for receiving a large quantity of U.V.-cured inks and delivering individual portions of ink to a plurality of separate columns for a printing press. 
         [0020]    The exact manner in which these objects and other objects and advantages are achieved in practice will become more apparent when considered in conjunction with the following detailed description of the invention and shown in the accompanying drawings in which like reference numbers indicate corresponding parts throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective view of several ink pumps wherein there is a single so-called stepper motor for each pump, operating through a toothed belt to drive a shaft for each pump, and showing plural hoppers for receiving, in this case, an U.V.-cured ink, with the various ink pump inlets being at the bottom of the trough and the outlets for the ink in individual hoses at the lowest part of the apparatus; 
           [0022]      FIG. 2  is a vertical sectional view of the ink pump apparatus of  FIG. 1 ; 
           [0023]      FIGS. 3-3A  are a perspective views of the drive train of  FIGS. 1 and 2 ; 
           [0024]      FIG. 4  is a greatly enlarged side elevational view of the rotor, showing its single helix configurations; and 
           [0025]      FIGS. 4A-4D  show the cross-section of the eccentric rotor at the various positions of the rotor inside the cylindrical elastomeric stator; and the ink in the progressive cavities of the invention. 
           [0026]      FIG. 5  is a greatly enlarged vertical sectional view of the rotor and stator, and showing the sideways movement of the rotor and the spaced apart pockets for advancing the ink, as well as showing the two axes very closely spaced apart. 
       
    
    
       [0027]    While changes and variations may be made to the apparatus and method by those skilled in the art, the described method and apparatus are presently preferred by the inventors herein. 
       DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    Referring now to drawings in greater detail,  FIGS. 1-3  show the invention to be embodied in an ink pump apparatus for U.V.-curable inks generally designated  10 , which includes a frame generally designated  12  having a horizontally extending portion  13  and a vertically extending portion  14 . There is also an extension  16  of the vertical portion of the frame  12  and affixed thereto; the extension  16  completes the vertical portion of the frame  14 . The frame  12  further includes a horizontal shelf  18  extending outwardly from the frame  14 . In addition to this shelf, there are an additional pair of shelves, a lower shelf  22  and an upper shelf  24 , with fasteners  26 ,  28  adapted to securely position these shelves relative to the frame  12 . 
         [0029]    There is one motor  30  shown which will be described in some detail. The motor  30  is one of an array of four upper motors generally designated  32  which are identical to the motor  30 . The motors  30  are secured to the shelf  24 , and operate the small pulleys  46  shown, and serve as the primary drive for the shafts, as will be explained. In other words, the smaller pulley  46  rotates faster than the large pulley  50 , giving the larger pulley a slower rotational velocity, but a much larger force. 
         [0030]    The frame  14  is covered in its upper portions by a plate  38 , which is held in place by fasteners  40 . 
         [0031]    The motor  30 , and each of the other motors are substantially identical thereto, includes a shaft terminating in a reduced size pulley  46  which in turn drives a toothed belt  42 . 
         [0032]    The belt  42  is trained around a larger pulley  50 . The relative sizes of the pulleys  46 ,  50  establish the mechanical advantage of this drive, in this case 3 to 1. Any other drive can be used, however, the smaller pulley  46  rotates faster than the large pulley  50 , giving the large pulley a slower rotational velocity, but a much larger force. 
         [0033]    The pulley forms the top portion of a power train  51  which begins with an upper drive shaft  52 . This uppermost drive shaft  52  terminates at its bottom in an upper coupler  54  with a re-entrant in the bottom surface. There is an intermediate shaft  56  lying between the upper coupler  54  and the top portion of the upper universal joint  58 . The upper universal joint  58  has a third shaft  60  extending toward and joining the lower universal joint  62 . 
         [0034]    These universal joints  58 ,  62  enable the rotor to accommodate its off-center action to be described herein. There are pins  64 ,  66  forming one part of each universal joint  58 ,  62  to allow motion in that plane. 
         [0035]    There are a plurality of ink outlets  70 ,  72 , etc. in the form of tubes or hoses to receive the U.V-curable ink, as will be explained further herein. The lower portion of the frame element  13  includes a plurality of hollow chambers  74 , etc., each one of which communicates with a corresponding lower hose connector  70 ,  72 , etc. In other words, the chambers  74 , etc. are isolated from one another. 
         [0036]    An incidental feature of the drive train is in the construction of the upper connector  54 . This hollow coupler  54  is adapted to receive a square end portion  57  of the intermediate shaft  56  in an opening  59 ; a square opening  59  has been shown, but any non-circular opening will function. This enables the user to separate the power train for maintenance, etc. 
         [0037]    Referring now to  FIGS. 4-4D , there is shown a view of the rotor  82  which is affixed to the lower universal joint  62  and extends downwardly therefrom. The rotor  82  has a tight fit in the rubber core of the stator  80 . From  FIG. 4 , the single helix construction of the rotor  82  can be seen. The sine wave of the drawing  FIG. 4  shows the highest points  85  of the single helix. The body of the rotor  82  will be seen by reference to  FIGS. 4A-4D . These drawings illustrate the section of the progressive cavities or pockets  90 ,  92  as they progress along the interior of the stator  77 . These cavities are depicted in lines A-A, B-B, C-C and D-D. The two offset axes can also be seen as the double crosses  84 , one being the center of the rotor and the other being the axis about which the rotor travels. 
         [0038]    Referring now to  FIG. 5  there is shown the stator generally designated  80 , and the two axes are illustrated in the broken lines  86  and  88 . These show the geometric center and the center of rotation of the rotor in use. 
         [0039]    Another illustration is shown in  FIG. 5  where the progressive cavities or pockets  90 ,  92  are formed by the double helix characterizing the stator and the single helix characterizing the rotor  85 . These cavities move along toward the outlets of the stators as the rotor  85  revolves or gyrates. 
         [0040]    Referring now to the operation and use of the device and method of the invention, it is assumed that the ink will be placed in a single large volume trough  30  with a plurality of the baffles or interior or walls  31 ,  31   a,  etc., subdividing the trough  30  at the top, but with the lower portions of the walls or baffles being spaced from the bottom of the trough. The inclined inner walls  34  shown in phantom lines in  FIG. 2 , urge the upper portions of the viscous thixotropic ink to the baffles, and these baffles are shown in  FIGS. 1 and 2 . The baffles prevent the ink from accumulating at the right hand side of the pump (facing the pumps). 
         [0041]    The motors are activated, each with its own speed control, with the result that the small pulleys  46  pull the belt  42  around the upper or larger pulleys  50 . This causes the various shafts  52 ,  56 ,  60  to rotate each one with its own speed. The speed at which the drive shafts rotate can vary considerably. Thus, with a stepper motor, there are some 200-400 steps in one revolution. There are some motors available which would have up to 800 steps per revolution. Thus, if one is using a stepper motor in the apparatus, the signal advances the motor in that way. 
         [0042]    The shafts  52 ,  56 ,  60  described are shown to be supported by, or run in appropriate bearings  55 A,  55 B, etc. as well as bearings  56 A and  56 B. These ensure that the drive shafts will rotate as desired, with there being virtually no departure from a true circular course. The spring  57 A keeps the shaft  52  and the shaft  56  in close proximity with the square portion  57  of the shaft end  57  fitting into the square recess  59 . 
         [0043]    Therefore these drive shafts should all function satisfactorily, but if it comes time to remove the lower portion of the apparatus from the upper portion, one merely needs to slide down the springs  57 A and the locking part  57  may readily be removed merely by hand pressure. 
         [0044]    As the drive shaft rotates, and the two universal Joints  58 ,  62  rotate on their respective axes, ink is taken from the lower portion of the trough  32  surrounding the lower universal joint  62 . With this universal joint  62  and the rotor  82  rotating, and with the stator  80  standing still, there is a progressive movement of the cavities or pockets, as they are advanced by the action of the rotor  82 . The action of the pump thus immediately fills and maintains under pressure the now ink-filled chamber  74 , located just beneath the lower end of the stator  80 . 
         [0045]    In the illustrated case, the motors that are not shown operate the pulleys  47 ,  49 , etc., and these operate adjacent and parallel drive trains to those energized by the motors  30 ,  32 , etc. Each of these pumps is operated by entirely separate signals, with the motors being allowed to operate completely independently of the other. 
         [0046]    In another embodiment, the motors are operated by strictly a direct, non-digital operation, and these motors can be operated in this way if desired. 
         [0047]    Referring now to the materials from which the various components are made, most non-ferrous metals can be used, but ferrous materials cannot be used, with the exception of stainless steel. Aluminum, a variety of ceramics and very hard plastics such as a Kynar, PVDF and nylon can be used. The main requirement is that the rotor be strong enough to hold up under the strain of being in contact with the relatively stiff stator as it engages the rubber. 
         [0048]    Referring now to the rubbers, the most important factor is to ensure the rubber has a high enough Durometer, about 90 to 95, in order to function. The rotor is strongly resistant to rotation when there is an initial tight fit between the rotor and the stator, but as the rotor continue to rotate, it becomes somewhat more compliant. The main consideration for the rubber is that it has a high enough Durometer (90-95, for example). Other stiff rubbers besides a Buna-N includes for example, some vinyl nitrides, which are commercially available. 
         [0049]    It will thus be seen that the present invention provides an apparatus and method for feeding U.V.-curable inks to their destination without premature curing. The apparatus includes a number of individual worm and stator type pumps, and means for driving the rotor around the stator at the correct rate. Further embodiments of the invention having been described in detail, and other changes in modifications may be made to the described form of apparatus and method, and it is anticipated that such changes or modifications may be made without departing from the spirit of the invention of the scope of the appended claims.