US3580261A

US3580261A - Printing screen cleaner

Info

Publication number: US3580261A
Application number: US823760A
Authority: US
Inventors: John W Key
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-05-12
Filing date: 1969-05-12
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

Printing screens are carried through a tunnel by an overhead conveyor. In an enlarged central section of the tunnel are opposed rows of spray heads to direct a cleaning solvent at the screens under pressure. A solvent with material removed from the screens drains into a removable separating tray to extract at least a portion of the material from the solvent. The solvent then drains into a sump from which it is pumped back to the spray heads. At opposite ends of the central cleaning section are entrance and exit sections having doors which are pushed aside by the screen as it is moved through the tunnel. A fan draws air in from the ends of the tunnel and discharges it out a stack. Fire quenching means has spray heads in the tunnel.

Description

United States Patent 2,549,070 4/1951 Drews.......

[72] Inventor JohnW. Key

606 Ironwood Drive, Arlington Heights, Ill. 2,766,764 10/ 1956 Bennett 60004 3,049,135 8/1962 Kuhl et a1.

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P E -R b rtL.Bl t [54] PRINTING SCREEN CLEANER "Mary xammer o 6 cu ge AttorneyDarbo, Robertson and Vandenburgh 11 Claims, 4 Drawing Figs.

ABSTRACT: Printing screens are carried through a tunnel by lnt. an overhead conveyon In an enlarged central section of the [so] tunnel are opposed rows of spray heads to direct a cleaning Field of solvent at the screens under pressure. A solvent with material removed from the screens drains into a removable separating tray to extract at least a portion of the material from the solvent. The solvent then drains into a sump from which it is [56] References Cited UNITED STATES PATENTS 971,745 10/1910 Gungerich 2,154,559 4/1939 Bilde 2,399,205

pumped back to the spray heads. At opposite ends of the central cleaning section are entrance and exit sections having 68/209 doors which are pushed aside by the screen as it is moved 134/97 through the tunnel, A fan draws air in from the ends of the 134/ I 48(UX) tunnel and discharges it out a stack. Fire quenching means has 1/1947 Zademach et a1. 134/131X spray heads in the tunnel.

4/1946 Campbell........ 2,413,853

Patented May 25, 1971 2 Sheets-Sheet 1 Patented May 25, 1971 2 Sheets-Sheet 2 PRINTING SCREEN CLEANER BACKGROUND OF THE INVENTION In screen printing an open mesh fabric has a design outlined therein by closing the open mesh in some areas. The screen is then placed over the surface to be printed and the printing dye, ink, paint, or the like (subsequently referred to as printing material) forced through the remaining open mesh areas onto the surface to be printed. Normally, it is worthwhile to salvage the screens after use. This is done by removing the printing material with a suitable solvent, many of which are highly flammable, while others may be caustic, etc., making them difficult or undesirable to handle. If the design of the screen is not to be reused, the screen is further cleaned to remove the material employed to define the design. Usually the printing material is soluble in a different solvent from that which will remove the material employed to form the design, e.g., one may be soluble in lacquer thinner and the other in water. The term solvent is employed herein to refer to a liquid which will wash out the material desired to be removed from the screen.

A number of different procedures have been employed from time to time to remove material from printing screens. Without attempting to enumerate them all, these have included such practices as: dipping or immersing in a solvent; brushing the screen with a solvent; and placing the screen in a comparatively large enclosure in which there are moving, e.g. rotating, spray heads to direct a stream of solvent at the screen from various angles. All of these have had one or more of various disadvantages. Any such cleaning process which requires individuals to participate in, or be near, the cleaning action are likely to involve health hazards. When cleaning with a highly flammable solvent there are serious dangers of fire and explosion. A dipping process requires an extremely large volume of solvent plus the fact that there is little mechanical action to assist in the cleaning process. Moving spray heads require a comparatively large enclosure which obviously occupies space that might be otherwise used and which increases the size of the potential explosion bomb. If there is not an enclosure about the spraying area there is a waste of costly solvents in overspray and obvious fire dangers.

The principal object of the present invention is to provide an apparatus for cleaning printing screens or the like, and which overcomes the disadvantages of the prior art devices and procedures. The apparatus is relatively small and compact. There is little danger of fire and, should it occur, it can be readily controlled. The apparatus will accommodate various sizes of printing screens. It requires no manual labor except that of loading the screen into the machine and unloading it. These operations are performed in areas in which the health hazards, otherwise present, are avoided. Should the screen not be thoroughly cleaned in a first pass through the machine. it is a simple matter to run the screen through the machine a second time. The solvent is continually reused and there is extremely little loss from overspray. Before the solvent is reused, a substantial portion of the material removed from the screen is separated from the solvent in a tray. This tray is removable so that the separated material can easily be discarded.

Further objects and advantages will become apparent from the following description taken in conjunction with the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation, partially broken away, of an embodiment of the invention;

FIG. 2 is a section as viewed at line 22 of FIG. 1;

FIG. 3 is a section as viewed at line 3-3 of FIG. 2;

FIG. 4 is a partial section as viewed at line 44 of FIG. 2, with a shorter screen than that of FIGS. 1 and 3.

DESCRIPTION OF THE SPECIFIC EMBODIMENT The following disclosure is offered for public dissemination in return for the grant ofa patent. Although it is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose ofa patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief aid toward this purpose; as it is these that meet-the requirement of pointing out the parts, improvements, or combinations in which the invention concepts are found.

In the illustrated embodiment there is a frame, generally 10, which forms an upper enclosure 11 and a lower enclosure 12. The lower enclosure has a part of one wall in the form of a door 13 mounted on hinge 14. The upper enclosure 11 defines a tunnel l5 and is formed with an entrance section 16, an exit section 17 and a central cleaning section 18.

The screen 21 to be cleaned is carried through the tunnel by a conveyor, generally 22. The conveyor comprises an endless roller chain 23 trained for movement about sprockets 24. Sprockets 24 are secured to shafts 25 suitably journaled in frame 10. To one of shafts 25 is secured a pulley (not shown) which is engaged by belt 26 to rotate the shaft and move the chain. Belt 26 is driven by a pulley 27, driven at slow speed by motor 28 through a speed reduction unit 29. Motor 28 is reversible so that the chain may be driven in either direction. Projection from one side of chain 23 are a plurality of pins 32. Hangers 33 are releasably secured to the frames of screens 21 and have, at their upper ends, openings to receive pins 32 so that the hangers may be releasably connected to chain 23.

A plurality of doors, generally 34, are provided in the en trance and exit sections of the tunnel. The structure of these doors is best seen in FIG. 4. They comprise a mounting member or holder 35 secured to the appropriate wall of the section. To each of the holders is secured one of the ends of a plurality of individual gates 36. The opposite end of the gates projects substantially to the opposite wall of the tunnel. The gates are biased so as to have a normal position transverse to the tunnel, but they are movable so that they may be individually pushed aside by the screen 21 as it moves through the tunnel. While such gates may be formed in diverse ways, I prefer to form them of a continuous length of rubber or flexible plastic, one edge of which is held by holder 35. The portion of the strip projecting from the holder is slit at regular intervals to define the individual gates 36. For clarity of illustration the size of the slits is emphasized in FIG. 4. As best seen in FIG. 2, in the entrance section 16 the holder 35 of one door is affixed to one wall, while the holder 35 of the adjacent door is affixed to the other wall. The same arrangement is used in exit section 17.

To ensure that screen 2] remains centered in the tunnel during its movement therethrough, there are pairs of guide wires or thin rods 37 at opposite sides of the path of travel of the screen. These wires are held by mounting brackets 38 at the entrance and exit ends of the tunnel.

The bottom of the upper enclosure 11 has a drain opening 42 therethrough. One end of a tray 43 is below this opening. As best seen in FIG. 1, tray 43 is mounted in guides 44 so that it is removable. Adjacent the other end of the tray is a drain opening 45. Between the ends of the tray are a plurality of dividers or dams which separate the tray into a series of settling basins. While the dividers 46 can be solid, I prefer to have them solvent-permeable so that some filtering effect takes place as well as having the solvent overflow the tops of the dividers. The dividers are of different heights so as to form settling basins of different depths.

Below opening 45 in the tray is an opening 37 in the top of a container 48 forming a solvent sump. A trap connection 49 permits any overflow of the sump to be discharged into a sewer or the like. In normal operation this is not used but it may be necessary to handle excess liquid which may be discharged into the sump should the fire protection equipment be actuated as hereinafter described. Container 48 is provided with removable connections so that it may be taken out for cleaning should that be necessary.

The intake line 52 of a, motor drivenpump 53 communicates with sump container 48. The discharge line 54 of the pump communicates with a pair of headers 55 positioned on opposite sides of the central section 18 of the tunnel. On headers 55 are a plurality of spray heads 56, each of which directs the solvent 57 under pressure at various directions towards the opposite sides of the screen, as illustrated. A window 58 is provided in one wall of the central enclosure 18 through which the cleaning action may be observed.

The upper enclosure 11 includes a stack 61 through which air and vapors may be discharged elsewhere. In the stack is a fan 62, belt driven by a motor 63. The fan forces the air and vapors out through the stack and at the same time draws fresh air in past the doors at the two ends of the tunnel. This negative air pressure in the tunnel prevents any of the vapors escaping into the area immediately adjacent the cleaning apparatus and thus reduces the danger of fire and explosion. Two automatic sprinkler heads 64 are positioned in the interior of the enclosure at the opposite ends of the central section 18. A third automatic sprinkler head 65 is positioned in stack 61. Pipes 66 connect the sprinkler heads to a suitable source (not shown) of fire extinguishing fluid, such as water or carbon dioxide. As is conventional, the sprinkle heads will automatically open in the event offire in the enclosure.

The screen 21 to be cleaned first has the hangers 33 attached thereto, if they are not permanently affixed. The hangers 33 are then hung on pins 32 on the lower run of chain 23 at one (or the other) end of the tunnel. Sprockets 24 are positioned sufficiently far from the ends of the tunnel to permit the hanging of the screen on the chain before the screen must enter the tunnel.

Motor 28 is then energized to move the screen slowly through the tunnel. A speed of movement, for example, of 6 inches per minute is eminently satisfactory. The pump 53 is, of course, energized to force the cleaning fluid 57 out of spray heads 56. As the screen slowly moves past the spray heads, the angle of incidence of the solvent onto the screen is constantly changing with respect to any one portion of the screen because of the spread of the spray produced by the spray heads. This plus the force of the fluid and the solvent action does an excellent job of cleaning the screen.

As the screen leaves the cleaning section 18 and enters the exit section 17, the fluid drains from the screen so that by the time the screen is completely out of the tunnel it is dry for all practical purposes. The doors 34 only open to the extent necessary to permit the passage of the screen. This, plus the use of multiple doors, prevents the loss of the solvent out through the exit or entrance portions of the tunnel. If it should turn out that the material on the screen has gotten particularly hard and requires extra cleaning, it is only necessary to reverse motor 28 and cause the screen to move through the tunnel in the reverse direction, thus obtaining a second cleaning. Substantial amounts of the material removed from the screen will settle in the tray 43, the amount depending upon the specific material, the solvent, etc. After a day's use, or more frequently if necessary, and while the pump 53 is shut down, the door 13 is opened and tray 43 removed. The material trapped therein can be removed and disposed of. The tray 43 then is returned to its proper position as illustrated.

lclaim:

1. An apparatus for cleaning objects of approximately a given width,'such as printing screens, with a liquid solvent to remove material from the object, said apparatus comprising:

a frame;

enclosure means on said frame and defining a tunnel through which the object can pass, said tunnel having a central cleaning section and entrance and exit sections at opposite sides of the central section, and defining an exhaust duct communicating with said central section, said enclosure means having a bottom with an opening therein through which liquid solvent can drain, said sections all being closed at the top, said entrance and exit sections having doorways at the distal ends thereof through which said object can enter and leave the enclosure means, there being a linear path between said doorways and through said sections, said entrance and exit sections being narrower in a direction transverse to said path than is said central section and only slightly wider than said given width;

conveyor means mounted on said frame and trained for movement along said path extending from beyond said doorways and through said tunnel for supporting and moving one of said objects through said tunnel;

cleaning means mounted on said frame and including,

a sump below said bottom and positioned to receive solvent from said opening,

spray means in said central section and at opposite sides of the path of the object to direct sprays of liquid solvent under pressure at opposite sides of the object, and

pump means communicating with said sump and said spray means to withdraw solvent from said sump and to deliver it under pressure to said spray means;

fan means in said enclosure for producing a flow of air into the doorways of the entrance and exit sections and out through said exhaust duct; and

fire quenching means in said enclosure including a spray head to discharge a fire quenching substance upon the occurrence of a fire.

2. An apparatus as set forth in claim 1, wherein said cleaning means includes separating means to remove material from said liquid solvent.

3, An apparatus as set forth in claim 2, wherein said separating means comprises a removable tray between said opening and the sump to receive liquid and material from the opening adjacent one end of the tray and to discharge into the sump from a point adjacent the other end of the tray, said tray having a series of dividers thereacross between said ends of the tray to divide the tray into a series of basins.

4. An apparatus as set forth in claim 3, including door means in said entrance and exit sections, said door means being normally closed and being pushed open by the object as it moves through the through the tunnel, each door means comprising a plurality of gates arranged in an approximately vertical row, said gates being affixed to one side of the enclosure means and extending to'adjacent the other side of the enclosure means, said gates being individually biased to a position transverse to the path and being individually movable to a position along said one side of the enclosure means.

5. An apparatus as set forth in claim 4, wherein in each of said entrance and exit sections there is one vertical row of said gates affixed to a first side of the enclosure means and a second vertical row of said gates affixed to a second side of the enclosure means, said first and second rows being spaced from each other along said path.

6. An apparatus as set forth in claim 1, wherein said apparatus includes door means in said entrance and exit sections, said door means being normally closed and being pushed open by the object as it moves through the tunnel and in each of said entrance and exit sections there is one vertical row of door means affixed to a first side of the enclosure means and a second vertical row of door means affixed to a second side of the enclosure means, said first and second rows being spaced from each other along said path.

7. An apparatus as set forth in claim 6, wherein each door means comprises a plurality of gates arranged in an approximately vertical row, said gates being affixed to one side of the enclosure means and extending to adjacent the other side of the enclosure means, said gates being individually biased to a position transverse to the path and being individually movable to a position along said one side of an enclosure means.

8. An apparatus for cleaning objects of approximately a given width, such as printing screens, with a liquid solvent to remove material from the object, said apparatus comprising:

a frame;

enclosure means on said frame and defining a tunnel through which the object can pass, said tunnel having a central cleaning section and entrance and exit sections at opposite sides of the central section, said enclosure means having an opening in the bottom thereof through which liquid solvent can drain, the tunnel at said entrance and exit sections being only slightly wider than the width of the object and the tunnel at the cleaning section being substantially wider than at the entrance and exit sections;

door means in both the entrance and exit sections for normally closing the tunnel at said entrance and exit sections and being pushed open by the object as it moves through the tunnel, each door means comprising a plurality of gates arranged in an approximately vertical row, said gates being affixed to one side of the enclosure means and extending toward the other side of the enclosure means, said gates being individually biased to a position transverse to the path and being individually movable to a position along said one side of the enclosure means;

conveyor means mounted on said frame and trained for movement along a path through said tunnel for supporting and moving one of said objects through said tunnel; and

cleaning means mounted on said frame and including,

a sump below said enclosure and positioned to receive solvent from said drain,

pump mean communicating with said sump and said spray means to withdraw solvent from said sump and to deliver it under pressure to said spray means.

9. An apparatus as set forth in claim 8, wherein said cleaning means includes separating means to remove material from said liquid solvent.

10. An apparatus as set forth in claim 9, wherein said separating means comprises a removable tray between said opening and the sump to receive liquid and material from the opening and the sump to receive liquid and material from the opening adjacent one end of the tray and to discharge into the sump from a point adjacent the other end of the tray, said tray having a series of dividers thereacross between said ends of the tray to divide the tray into a series of basins.

11. An apparatus as set forth in claim 8, wherein in each of said entrance and exit sections there is one vertical row of said gates affixed to a first side of the enclosure means and a second verticalrow of said gates affixed to a second side of the enclosure means, said first and second rows being spaced from each other along said path.

Claims

1. An apparatus for cleaning objects of approximately a given width, such as printing screens, with a liquid solvent to remove material from the object, said apparatus comprising: a frame; enclosure means on said frame and defining a tunnel through which the object can pass, said tunnel having a central cleaning section and entrance and exit sections at opposite sides of the central section, and defining an exhaust duct communicating with said central section, said enclosure means having a bottom with an opening therein through which liquid solvent can drain, said sections all being closed at the top, said entrance and exit sections having doorways at the distal ends thereof through which said object can enter and leave the enclosure means, there being a linear path between said doorways and through said sections, said entrance and exit sections being narrower in a direction transverse to said path than is said central section and only slightly wider than said given width; conveyor means mounted on said frame and trained for movement along said path extending from beyond said doorways and through said tunnel for supporting and moving one of said objects through said tunnel; cleaning means mounted on said frame and including, a sump below said bottom and positioned to receive solvent from said opening, spray means in said central section and at opposite sides of the path of the object to direct sprays of liquid solvent under pressure at opposite sides of the object, and pump means communicating with said sump and said spray means to withdraw solvent from said sump and to deliver it under pressure to said spray means; fan means in said enclosure for producing a flow of air into the doorways of the entrance and exit sections and out through said exhaust duct; and fire quenching means in said enclosure including a spray head to discharge a fire quenching substance upon the occurrence of a fire.

3. An apparatus as set forth in claim 2, wherein said separating means comprises a removable tray between said opening and the sump to receive liquid and material from the opening adjacent one end of the tray and to discharge into the sump from a point adjacent the other end of the tray, said tray having a series of dividers thereacross between said ends of the tray to divide the tray into a series of basins.

4. An apparatus as set forth in claim 3, including door means in said entrance and exit sectioNs, said door means being normally closed and being pushed open by the object as it moves through the through the tunnel, each door means comprising a plurality of gates arranged in an approximately vertical row, said gates being affixed to one side of the enclosure means and extending to adjacent the other side of the enclosure means, said gates being individually biased to a position transverse to the path and being individually movable to a position along said one side of the enclosure means.

8. An apparatus for cleaning objects of approximately a given width, such as printing screens, with a liquid solvent to remove material from the object, said apparatus comprising: a frame; enclosure means on said frame and defining a tunnel through which the object can pass, said tunnel having a central cleaning section and entrance and exit sections at opposite sides of the central section, said enclosure means having an opening in the bottom thereof through which liquid solvent can drain, the tunnel at said entrance and exit sections being only slightly wider than the width of the object and the tunnel at the cleaning section being substantially wider than at the entrance and exit sections; door means in both the entrance and exit sections for normally closing the tunnel at said entrance and exit sections and being pushed open by the object as it moves through the tunnel, each door means comprising a plurality of gates arranged in an approximately vertical row, said gates being affixed to one side of the enclosure means and extending toward the other side of the enclosure means, said gates being individually biased to a position transverse to the path and being individually movable to a position along said one side of the enclosure means; conveyor means mounted on said frame and trained for movement along a path through said tunnel for supporting and moving one of said objects through said tunnel; and cleaning means mounted on said frame and including, a sump below said enclosure and positioned to receive solvent from said drain, spray means in said central section and at opposite sides of the path of the object to direct sprays of liquid solvent under pressure at opposite sides of the object, and pump mean communicating with said sump and said spray means to withdraw solvent from said sump and to deliver it under pressure to said spray means.

11. An apparatus as set forth in claim 8, wherein in each of said entrance and exit sections there is one vertical row of said gates affixed to a first side of the enclosure means and a second vertical row of said gates affixed to a second side of the enclosure means, said first and second rows being spaced from each other along said path.