Patent Publication Number: US-3874022-A

Title: Means for removing ink from a screen and including a cleaning head and accumulator

Description:
[451 Apr. 1, 1975 United States Patent [191 Wogoman et al.  
  f o G mh Am W mt R mm F0 M a I mmwh WA m n I. L l vw m mu w U u mn D mud N FP.m 0 M M M N E n ARA e ECE V MSHIm 4 5 5 l [73] Assignee: Wells Electronics, Inc., South Bend, Assistant Examiner-Richard Fisher Ind.  
 Attorney, Agent, or FirmOltsch &amp; Knoblock [57] ABSTRACT Ink is removed from the screen utilized in a silk screen [22] Filed: Mar. 19, 1973 [2]] Appl. No.: 342,740  
 printing process by positioning a cleaning head having first and second orifices over the screen. A vacuum is drawn at one of the orifices of the cleaning head and causes the cleaning solvent to be withdrawn from the other orifice across the cleaning head in contact with the screen, thus causing ink particles to be removed from the screen and transported in the solvent to a depository.  
 References Cited UNlTED STATES PATENTS 1.669.077 15/321 x 4 Claims, 5 Drawing Figures PATENTED APR 1 sum 1 or 2 MEANS FOR REMOVING INK FROM A SCREEN AND INCLUDING A CLEANING HEAD AND ACCUMULATOR BACKGROUND OF THE INVENTION This invention relates to a method and means for removing ink from the screen utilized in a silk screen printing process.  
  Printing by means of the silk screen process has been utilized for centuries. The early screens utilized in such a process were of finely interwoven silk, while the screens used today in the process are of stainless steel, polyester, nylon or similar plastic material fibers in addition to silk. Heretofore, the normal practice of cleaning such screens, whether of silk, steel or plastic material, has been by applying solvent directly to the screen by hand and removing by wiping with lint free cloth. This results in the ink getting on ones hands and even ones clothing, thus constituting a rather messy, timeconsuming and undesirable job. The direct contact of the wiping cloth accelerates the breakdown of the emulsion used on the screen.  
  The method and apparatus of this invention allows the screen utilized in a silk screen printing process to be cleaned in a rapid, simplified and tidy manner.  
 SUMMARY OF THE INVENTION The method of this invention relates to the removal of ink from the screen utilized in a silk screen printing process and contemplates the use of a cleaning head having spaced first and second orifices therein. The cleaning head is positioned over the screen, preferably in contact therewith, with the first and second orifices overlying the screen in close proximity. A vacuum is provided at the second orifice which causes solvent to be drawn from the first orifice, across the surface of the screen and into the second orifice after which, along with the ink removed from the screen, the solvent is deposited in an accumulator. The flow of solvent across the screen can be stopped by simply removing or lifting the cleaning head from the screen. By interrupting the vacuum to the second orifice in the cleaning head, the solvent and ink collected in the accumulator will pass into a tank or drum where the ink will settle to the bottom of the tank and the solvent recirculated across the surface of the screen upon resumption of the vacuum.  
  Means are provided by which the solvent flow from the first orifice in the cleaning head can be terminated while maintaining a vacuum at the second orifice to remove any exccss solvent from the screen such as at termination of the cleaning process.  
  Accordingly, it is an object of this invention to provide a method of removing ink from the screen utilized in a silk screen printing process. I  
  Another object of this invention is to provide a method of removing ink from the screen utilized in a silk screen printing process through means of drawing a cleaning solvent across the surface of the screen.  
  Still another object of this invention is to providea method of removing ink from a screen utilized in a silk screen printing process in a tidy and efficient manner.  
  Another object of this invention is to provide apparatus for removing ink from the screen utilized in a silk screen printing process.  
  Other objects of this invention will become apparent upon a reading of the inventions description.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the apparatus utilized to practice the method of this invention.  
  FIG. 2 is a detailed longitudinal sectional view of the accumulator tank constituting one of the components of the apparatus shown in FIG. 1.  
  FIG. &#39;3 is a fragmentary sectional view taken along line 33 of FIG. 1.  
  FIG. 4 is a view of the working surface of the cleaning head constituting one of the components of the apparatus of FIG. 1 and as seen along line 44 thereof.  
  FIG. 5 is a schematic diagram illustrating the method of this invention. A  
 DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment illustrated is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is chosen and described in order to explain the principles of the invention and its application and practical use to thereby enable others skilled in the art to best utilize the invention.  
  A description of the method of this invention can be best understood by referring to the schematic diagram illustrated in FIG. 5. Reference numeral 10 designates the cleaning head which has planar screen contacting faces 12. An oval recess 14 is formed in one of the faces 12. A pair of orifices 16 and 18 are formed within recess 14 at its opposite ends. A tank 20 containing an ink-removing solvent, such as tolulene, is connected to orifice. 16 in cleaning head 10 by a conduit 22 which communicates with the solvent. A container, hereinafter referred to as accumulator 24, having a float 26 therein is provided. Solvent tank 20 is connected to accumulator 24 below float 26 by means of a conduit 28. A vacuum source 30, such as a vacuum pump, is connected to accumulator 24 above float 26 by a conduit 32. Orifice 18 in cleaning head 10 is connected to accumulator 24 below float 26 by a conduit 34. A check valve 36 is positioned in conduit 28. Valve 36 allows liquid to flow through conduit 28 from the accumulator to solvent tank 20 only.  
  With cleaning head 10 positioned with its faces 12 contacting the upper surface of a screen 38 as shown in FIGS. 1 and 3, a vacuum produced by vacuum source 30 will be developed within the accumulator which at this time is empty of any solvent. As accumulator 24 is being evacuated, a vacuum is also formed through the means of conduit 34 at orifice 18 within re cess 14 in the cleaning head. Valve 36 is constructed so as to close upon the formation of a vacuum within the accumulator and thus prevent any solvent from passing from tank 20 into the accumulator through conduit 28.  
  The vacuum formed at cleaning head orifice 18 when the cleaning head is positioned against screen 38, as shown in FIGS. 1 and 3, causes a vacuum to be formed within recess 14 of the cleaning head above the screen. The vacuum in recess 14 causes solvent to be with drawn from tank 20 through conduit 22. out orifice 16 of the cleaning head and across screen 38&#39;, and into orifice 18. As the solvent is drawn across screen 38, ink thereon is removed and the solvent and ink pass through conduit 34 into the accumulator below float 26. The amount of vacuum at orifice 18 is sufficiently high in relationship to the size of the screen openings and any air drawn therethrough so that a sizeable vac uum is formed within cleaning head recess 14 even though there are openings in the screen. In fact, the air being drawn upwardly through the screen openings helps loosen the ink from the screen. As more solvent and ink enter accumulator 24 through conduit 34, float 26 will rise until it approaches the top of the accumulator where a valve plug or protrusion 40 closes conduit 32, as shown in broken lines in FIG. 2, thereby interrupting the vacuum within the accumulator and terminating the flow of solvent between orifices 16 and 18 of the cleaning head. At this moment valve 36 opens, and either through the weight of the liquid within accumulator 24 combined with the weight of float 26 or by a venting of line 32 to the atmosphere, or by removing the cleaning head from the screen to reduce the vacuum, the liquid solvent and ink therein flow through conduit 28 back into tank where the ink settles to the bottom of the tank. Upon the emptying of accumulator 24, float 26 returns to the bottom of the accumulator, thus opening conduit 32 and thereby causing the accumulator to again be evacuated when the cleaning head is positioned against screen 38. Re-evacuation of accumulator 24 causes the solvent to be withdrawn from tank 20 through line 22 and across cleaning head orifices l6 and 18 and screen 38 and back into the accumulator through conduit 34 below float 26. If line 32 were vented to release the ink and accumulated solvent within the accumulator, obviously this line would have to be closed before the evacuation of accumulator would begin again. This cycle of filling and emptying accumulator 24 would continue until the screen is cleaned of ink.  
  One embodiment of the apparatus for performing the screen cleaning method above described in shown in detail in FIGS. 1-4. In FIGS. l-4 accumulator 24 is shown seated upon the top of solvent tank 20, overlying opening 42 into the tank. Accumulator 24 includes a cylindrical side wall 44, an upper end wall 46 and a lower end wall 48. A pipe 50 extends through accumulator 24and into tank 20 through its opening 42. Pipe 50 preferably terminates approximately one-third of the distance from the bottom of tank 20. Conduit 22 which has one end connected to orifice 16 of cleaning head 10 is connected at its opposite end to the upper end ofpipe 50. Conduit 28 is preferably of rigid tubular form and is connected to lower end wall 48 of the accumulator and projects through tank opening 42 and into the tank. The upper end of conduit 28 is open and communicates at all times with the interior of accumulator 24. The lower end of conduit 28 has check valve 36 connected thereto. Valve 36 may be of the flapper type which closes over the lower end of conduit 28 when a vacuum is formed within accumulator 24 and which opens when the vacuum within the accumulator is reduced. A filter 52 is preferably incorporated into conduit 28 for the purpose of filtering out ink particles which are entrained within the solvent which is returned to the accumulator. A pipe 54 is connected to upper end wall 46 of the accumulator and extends downwardly therein. Conduit 34 which has one end connected to orifice 18 of cleaning head 10 has its opposite end connected to the upper end of pipe 54. The lower end 55 of pipe 54 terminates justabove lower end wall 48 of the accumulator so as to discharge solvent into the accumulator below float 26.  
  An opening 56 is formed in upper end wall 46. Conduit 32 which is connected at one end to vacuum source 30 has its opposite end placed in communication with accumulator opening 56 either by direct connection therewith or through a valve 58. Valve 58 is shiftable between a first position in which conduit 32 communicates with opening 56 thereby permitting the evacuation of the accumulator and a second position in which conduit 32 is vented to atmospheric air to terminate the vacuum within the accumulator. The construction of valve 58 may assume any one of a number of well known valve constructions. Float 26 within accumulator 24 may be hollow or formed ofa material, such as cork or expanded cellular foam plastic having a density which is less than that of the solvent. Protrusion 40 carried upon the upper surface of float 26 serves as a valve plug for opening 56 in upper end wall 46 of the accumulator. Pipes 50 and 54 extend in a free fit through float 26 so as to prevent rotation of the float within the accumulator and to serve as guides for directing protrusion 40 into opening 56, as seen in broken lines in FIG. 2, as the float rises to the top of the accumulator.  
 Abrasive material, such as spun nylon, may be in-- serted into the cleaning head recess 14 for the purpose of contacting the upper surface of the screen to loosen the ink thereon as the cleaning head is moved across the screen. During the cleaning process faces 12 of cleaning head 10 contact screen 38 and the cleaning head moves across the screen either by hand or mechanically in circular or back and forth movements. Solvent 66 is drawn from orifice 16 to orifice 18 across the screen due to the vacuum formed within recess 14 in the cleaning head as it contacts screen 38. To stop the flow of solvent, cleaning head 10 at recess 14 need only be raised from the screen, thus causing the vacuum formed within recess 14 to be terminated. A suitable solvent cut-off valve 62 associated with orifice 16 serves when actuated by the user of cleaning head 10 to stop the flow of solvent within orifice 16 with faces 12 of the cleaning head in contact with screen 38, thus permitting the vacuum still present within recess 14 to be utilized to suck up any solvent remaining upon the screen at the conclusion of the cleaning operation.  
  Lower end wall 48 of accumulator 24 is provided with feet 64 which serve to space the lower end wall slightly above opening 42 in the solvent tank. This allows the atmospheric air to enter the interior of tank 20 as the solvent 66 therein is being withdrawn. It is to be understood that the particular design of recess 14 as well as the number and arrangement of orifices l6 and 18 therein may vary, depending upon the application and construction of the cleaning head.  
  It is to be further understood that the invention is not to be limited to the details above given, but may be modified within the scope of the appended claims.  
 What we claim is:  
  1. Apparatus for removing ink from a screen utilized in a silk screen printing process with a solvent, said apparatus comprising a cleaning head having first and second spaced orifices therein, accumulator means for collecting said solvent after removal of said ink from the screen, said accumulator means including a side wall and upper and lower end walls cooperating to define a chamber within the accumulator means, first opening means in said accumulator means through which a vacuum is formed in said chamber. second opening means in said accumulator means, conduit means extending between said second opening means and said second orifice placing said second opening means and second orifice in flow communication, other conduit means having its one end connected to said first orifice and having its other and adapted for placement in a supply of said solvent, said cleaning head adapted to be placed over said screen and having a vacuum formed between said first and second orifices, and float means within said chamber, said float means being shiftable between the end walls of said accumulator means as said chamber fills with solvent entering from said second opening means, said float means having a draft line representing the depth the float means extends into said solvent when floating thereon, said first opening means being located above said draft line in all operative positions of said float means, said float means carrying means for blocking said first opening means to reduce the vacuum in said chamber as said float means is shifted by said solvent to a selected position within said chamber.  
  2. The apparatus of claim 1 wherein said first orifice is located below said draft line in all operative positions of said float means.  
  3. The apparatus of claim 1 and a third opening means in said accumulator means, said third opening means being located in the lower end wall of said accumulator means, conduit means having one of its ends connected to said third opening means and having its other end adapted for placement in a depository means for said solvent, valve means for closing said third conduit means when a vacuum exists in said chamber with said first opening means being not blocked by said float carried means, said third conduit means being open when said first opening means is blocked by said float carried means to allow solvent within said chamber to drain therethrough into said depository means.  
  4. The apparatus of claim 1 and valve means for blocking flow communication between said second opening means and said second orifice.