Abstract:
A screen printing ink pump which is designed to pump printing ink from a first container to a second container. A filter is provided at the discharge side of the pump above the second container to filter impurities from the ink during the pumping operation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a screen printing ink pump and more particularly to a screen printing ink pump having a filter or screen associated therewith to filter out impurities such as clumps of carbon or coloring that have not been evenly distributed in suspension, carbon (coloring agent) elements that are too large to flow during the printing process, packaging particles which have become mixed with the ink, or any foreign object or element that has polluted the ink. 
         [0003]    2. Description of the Related Art 
         [0004]    In a screen printing process, the object to be printed is normally placed on a supporting surface and a screen having a stencil incorporated therewith which has the desired printing pattern thereon is placed on the object. Screen printing ink is then placed on the screen with the ink then being forced downwardly through the mesh openings in the stencil by way of a squeegee or the like. If the ink has clumps of carbon or coloring agent elements that have not been evenly distributed in suspension, packaging particle which have become mixed with the ink, or any foreign object or element that has polluted the ink, the ink will not be uniformly forced through the stencil, thereby resulting in an imperfect printing job. In the past, in an effort to remove the impurities from the ink, the ink was manually strained through a mesh-like strainer member such as a porous cheese cloth, chamois or other straining device. In normal practice, the strainer is placed over an empty container and the printing ink is poured from a first container through the strainer member into another container. The prior practice is extremely laborious, time consuming and messy. 
       SUMMARY OF THE INVENTION 
       [0005]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. 
         [0006]    A screen printing ink pump is disclosed wherein printing ink is pumped from one container to another container and is filtered of impurities during the pumping process. The system of this invention includes an elongated, generally vertically disposed ink dip tube having open upper and lower ends and an inner wall surface. The ink dip tube is adapted to be extended downwardly into the ink in the first container. The dip tube has a first valve seat provided thereon below its lower end which has a lower ink intake side and an upper ink discharge side. A first valve is positioned in the dip tube which is movably positioned at the upper ink discharge side of the first valve seat. The first valve is movable between a first position wherein the first valve closes the upper ink discharge side of the first valve seat to a second position wherein the first valve is unseated from the first valve seat to permit the ink in the first container to be drawn upwardly into the dip tube. A compression spring is positioned in the dip tube and which has upper and lower ends. The system also includes an elongated hollow piston rod having upper and lower ends. The piston rod is slidably extended downwardly into the upper end of the dip tube. The piston rod is movable between an upper extended position and a lower retracted position with respect to the dip tube. The piston rod has a hollow piston fixedly secured thereto adjacent the lower end thereof which slidably sealably engages the inner wall surface of the dip tube as the piston rod is moved between its first and second positions. The compression spring yieldably urges the piston rod towards its upper extended position. 
         [0007]    A second valve seat is provided in the piston rod adjacent the upper end thereof. The second valve seat has a lower ink intake side and an upper ink discharge side. A second valve is movably positioned at the upper ink discharge side of the second valve seat. The second valve is movable between open and closed positions. 
         [0008]    A push handle is secured to the upper end of the hollow piston rod with the push handle having an ink passageway formed therein which has an ink inlet end and an ink discharge end. The ink inlet end of the ink passageway in the push handle is in fluid communication with the upper ink discharge side of the second valve seat. The second valve, when in its open position, permits ink to flow from the upper end of the piston rod to the ink inlet end of the ink passageway in the push handle when the piston rod is moved from its extended position to its retracted position. The second valve is moved to its closed position when the piston rod is moved from its retracted position to its extended position. 
         [0009]    A generally vertically disposed filter housing, having an upper ink intake end and a lower ink discharge end is also provided. The upper ink end of the filter housing is in fluid communication with the ink discharge end of the ink passageway and the push handle. An ink filter is positioned in the filter housing at the lower ink discharge end thereof. The filter housing is disposed laterally of the push handle, the piston rod and the dip tube so that the filter housing may be positioned over the second container. The ink discharge end of the filter housing is disposed in a plane which is higher than the lower end of the dip tube. 
         [0010]    Although the apparatus of this invention is ideally suited for filtering ink for use in a screen printing operation, the apparatus could also be used in other situations wherein it is desired to remove impurities from liquids. 
         [0011]    It is therefore a principal object of the invention to provide a screen printing ink pump having a filter associated therewith to filter out contaminants, globules, lumps, etc. from the printing ink. 
         [0012]    A further object of the invention is to provide a screen printing ink pump with a filter associated therewith which is easy to use and which is not messy. 
         [0013]    A further object of the invention is to provide a screen printing ink pump having a filter associated therewith which is easily cleaned and/or serviced. 
         [0014]    A further object of the invention is to provide a screen printing ink pump having a filter associated therewith with the filter being removable therefrom so as to clean or replace the same. 
         [0015]    These and other objects will be apparent to those skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0017]      FIG. 1  is a side elevational view of the apparatus of this invention being used to pump and filter printing ink with a portion of the containers being cut-away to more fully illustrate this invention; 
           [0018]      FIG. 2  is an exploded perspective view of the apparatus of this invention; and 
           [0019]      FIG. 3  is a partial vertical sectional view of the apparatus of this invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense in that the scope of the present invention is defined only by the appended claims. 
         [0021]    The screen printing ink pump with filter apparatus is generally designated by the reference numeral  10 . The pump and filter of this invention is designed to draw printing ink  12  from a first container  14 , filter the same and deposit the filtered ink into a second container  16 . 
         [0022]    Apparatus  10  includes a conventional liquid or condiment pump  18  which includes a vertically disposed hollow dip tube  20  having external threads  22  at its upper end  24 , a reduced diameter portion  26  at its lower end  28  which defines an outer shoulder  30  and inner shoulders  31  and  32 . Dip tube  20  also has a conventional flap valve  34  provided in the interior thereof which is designed to seed upon inner shoulder or valve seat  31 . Flap valve  34  is movable between open and closed positions. When flap valve  34  is closed, it prevents ink flow from the interior of dip tube  20  downwardly and outwardly through the lower end  28  of dip tube  20 . When flap valve  34  is open, it permits ink flow upwardly through the lower end  28  of dip tube  20  into the interior of dip tube  20 . If necessary, a hollow dip tube extender  36  may be secured to the lower end of dip tube  20 . Preferably, the lower end of dip tube  36  has a hollow double elbow  38  secured thereto and designed to rest upon the bottom of the first container  14  as seen in  FIG. 1 . 
         [0023]    Pump  18  also includes a hollow piston rod or plunger  40  having an upper end  42  and a lower end  44 . Piston rod  40  has a flexible annular piston  46  at its lower end  44  which extends outwardly therefrom. Piston rod  40  has an external shoulder  48  formed therein below its upper end. An internally threaded cap  50  is mounted on piston rod  40  which is adapted to be threadably secured to the external threads  22  on the upper end of dip tube  20 . The shoulder  48  limits the upward movement of piston rod  40  with respect to cap  50  when cap  50  is threaded onto the upper end of dip tube  20 . 
         [0024]    The numeral  54  refers to an elongated compression spring having an upper end  56  and a lower end  58 . Spring  54  is positioned in dip tube  20  so that its lower end  54  engages inner shoulder  32  in dip tube  20 . The upper end  56  of spring  54  engages the lower end of piston rod  40  to yieldably resist the downward movement of piston rod  40  with respect to dip tube  20  and yieldably urges piston rod  40  to its upper extended position. 
         [0025]    A flap valve  54  is mounted on the upper end of dip tube  40  and is movable between closed and open positions. The numeral  56  refers to a push handle having a passageway  58  extending therethrough. The intake end of passageway  58  is in fluid communication with the upper end of dip tube  40  by way of the flap valve  54 . The discharge end of passageway  58  has the inlet end of a discharge tube  60  secured thereto as seen in  FIG. 3 . The discharge end of tube  60  has an elbow  62  secured thereto as seen in  FIGS. 1-3 . The discharge end of elbow  62  is operatively secured to a generally vertically disposed hollow filter housing  64  which has external threads  66  formed therein which defines an upper shoulder  68 . O-ring  70  embraces the lower end of filter housing  64  so as to be positioned upwardly against the underside of shoulder  68 . 
         [0026]    The numeral  72  refers to the ink filter or screen of this invention. Filter  72  includes an O-ring  74  having a flexible screen or filter material  76  secured thereto and extending therebetween. The numeral  78  refers to a hollow cap having interior threads  80  and a discharge opening  80  defined by a shoulder  82 . Filter  72  is positioned within cap  78  so that O-ring  74  seats upon shoulder  82 . Cap  78  is threadably secured to the threads  66  of housing  64 . The mesh size of the openings in the ink filter or screen  72  will depend upon the viscosity of the ink being filtered. 
         [0027]    Although it is preferred that the apparatus of this invention utilizes a manually operated pump, the pump could be electrically driven. 
         [0028]    The apparatus of this invention is used as follows. The container  14  which has the ink  12  to be filtered or screen is opened. The empty container  16  is positioned adjacent container  14  as illustrated in  FIG. 1 . The pump  18  is inserted downwardly into the container  14  until the double elbow  38  rests upon the bottom of the container  14  as seen in  FIG. 1 . At that time, the filter housing  64  is positioned over the upper open end of the container  16  as also seen in  FIG. 1 . At that time, the piston rod  40  will be in its extended position as illustrated by solid lines in  FIG. 1 . Initially, valve  34  may or may not be open and valve  54  may or may not be open. The push handle is then pushed downward so that piston rod  40  is slidably extended downwardly in dip tube  20  to its fully retracted or depressed position. The piston  46  sealably and slidably engages the interior wall surface of dip tube  20  as piston rod  40  is moved downwardly to expel any air within dip tube  20  upwardly through piston rod  40 , through the open valve  54 , into filter housing  64  and outwardly through filter  72 . During the initial downward movement of piston rod  40 , valve  34  will be closed. 
         [0029]    Downward pressure on push handle  56  is then released so that spring  54  will cause piston rod  40  to return to its uppermost extended position. As spring  54  moves piston rod  40  upwardly, a suction is created in the interior of dip tube  20  so that ink in container  14  will be drawn into the elbow  38  and upwardly into dip tube  20  since valve  34  will be opened by the suction in dip tube  20 . At that time, dip tube  20  will be filled with ink. Piston rod  40  is then depressed which will cause the ink in dip tube  20  to be forced upwardly through piston rod  40  since valve  34  will be closed. The ink passing upwardly through piston rod  40  will then be forced or pumped through the filter housing  64  and through the filter  72  to remove the impurities from the ink. As piston rod  40  is subsequently moved upwardly within dip tube  20 , additional ink will be drawn into the dip tube  20 . The process is repeated until the desired amount of ink has been filtered. 
         [0030]    Although the invention has been described in language that is specific to certain structures and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.