EP0808248A1 - Oscillator screen cleaning apparatus - Google Patents

Abstract

An oscillator screen cleaning apparatus (10, 110) includes a housing (12, 112) having a plurality of spray nozzles (18, 118) to spray a printing screen (16, 116) with solvent. An oscillating mechanism (25, 128) oscillates the screen in front of the spray nozzles, which nozzles (18, 118) are arranged in opposing grid patterns for complete coverage of the screen with sprayed solvent. The srprayed solvent is collected, filtered and resprayed onto the screen at a high spray rate. Housing (12, 112) is coupled to a vapor recovery system (110, 145) to keep solvent vapors from escaping into the environment. In one embodiment (110), guide brackets (170) guide the screen (16, 116) perpendicular to the nozzles (18, 118) from the screen's sides to handle screens of different heights. A reservoir (120) with a sloped wall (140) and a pump (123) recaptures sprayed solvent and pumps it to the nozzles (18, 118) for recycling. A wipe down booth (152) captures excess solvent from a screen (16, 116) removed from the housing (12, 112) and directs the captured solvent to the reservoir (120).

Description

OSCILLATOR SCREEN CLEANING APPARATUS

Field of the Invention

This invention relates generally to screen printing and specifically to apparatuses and methods for cleaning printing ink and other materials from printing screens and frames used in screen

printing. Background of the Invention Screen printing, also known as serigraphics, is the

process of transferring an image to a substrate by the use of a printing screen through which ink is squeezed. The ink is then

deposited in all places on the substrate except where the screen has been processed by a photographically applied image depicting the places where ink is not to be forced through the screen mesh.

The imaged screen mesh is normally made of silk, plastic or metal and is held in place by a screen frame made of wood, plastic or

metal. The ink contains pigment or dye in an appropriate vehicle.

Screen cleaning requires the removal of all ink residue

from the screen and frame when the printing is completed.

Methods currently utilized to clean printing screens involve

spraying the screen with pressurized solvent from a nozzle or gun

structure. Many spraying techniques, however, result in overspray

which directs solvent where it is not desired thereby wasting

solvent and increasing the costs and inefficiency of the procedure.

Additionally, spray cleaning methods usually require the use of paid

workers thus raising the costs of cleaning and also exposing the

workers to the solvent and solvent fumes.

Several attempts have been made to develop a

cleaning procedure and apparatus which eliminates the various

drawbacks of the above-mentioned procedures. For example, U. S.

Patent No. 3,580,261 discloses a printing screen cleaner which

utilizes two vertically oriented lines of nozzles which oppose each

other inside a cleaning enclosure. A screen is passed on a

conveyer belt through the opposing nozzle lines whereupon it is

sprayed with pressurized solvent. While eliminating several of the

drawbacks of the above-discussed existing methods, the cleaner has other drawbacks which prevent the efficient and effective cleaning of a printing screen. Specifically, it utilizes only two opposing lines of spray nozzles within the enclosure and, therefore, each area of the screen is sprayed only once as the screen passes

through the opposing nozzle lines. The screen is generally not adequately cleaned when the cleaning cycle has been completed

and, therefore, the screen must be taken and passed through the cleaner additional times for additional cleaning cycles until it is

sufficiently clean. As may be appreciated, such a task is time consuming and costly, and requires continuous worker supervision

of the cleaning machine. For example, the work involves handling the screen by insertion into the machine, removal and manual brush

agitation, then reinsertion, to insure adequate cleaning. Therefore, the cleaner disclosed in the '261 patent is not very efficient or cost

effective.

The screen washing apparatus of U. S. Patent No. 3,656,493 utilizes an enclosure and a single spray nozzle which is directed over the screen by a control mechanism to spray a predetermined pattern. Specifically, the nozzle sweeps horizontally in one direction across the screen to an end position

and is then ratcheted down a few rows of the screen whereupon it sweeps in the opposite direction to an opposite end position and is ratcheted down to begin the process again. The nozzle

continuously sweeps and ratchets until it reaches a bottom position which is pre-set by an operator. The screen is swept only once by

the nozzle and if any portions remain dirty, the operator must remove the nozzle and manually spray the screen. Furthermore,

the single nozzle only sprays a small area of the screen at any given time. Again, such a screen washing apparatus is neither

efficient nor cost effective because the cleaning process has to be monitored to ensure that the single sweep was sufficient to remove the printing ink and the screen must be manually sprayed if the single sweep was not sufficient. Furthermore, the gun is controlled with manual pre-sets which must be adapted to spray a particular screen size, and insertion of a different size screen into the

washing apparatus requires additional programming of the spray pattern of the device, thus further reducing the efficiency and cost effectiveness of the apparatus. Additionally, the operator is exposed to solvent fumes whenever it is necessary to manually

direct the gun to completely clean the screen. The screen cleaning apparatus of U. S. Patent

No. 4,420,004 utilizes a single row of adjacent nozzles which moves horizontally with respect to a screen to spray the screen and remove the printing ink as well as the stencil or print pattern. The single row of spray nozzles requires a continuous back and forth sweeping motion of the nozzle row which must be repeated until

the screen is adequately cleaned. Since there is only a single line

of nozzles, only a small area of the screen is sprayed at any one time leaving the remaining area unsprayed until the nozzle line

again passes over that area. This increases the time that is

required to adequately clean the screen because when one small area of the screen is being sprayed, the remaining area of the

screen is dormant. As a result, the cleaning cycle of the apparatus in the '004 patent is inefficient and, therefore, not cost effective.

There is still a need in that art for screen cleaning apparatuses which are versatile, reliable and low-cost, and which

provide superior cleaning without taking up a large amount of

valuable floor space. Various currently available screen cleaning apparatuses utilize a variety of different integrated systems which must be operably coupled together for proper screen cleaning.

Such apparatuses also utilize numerous adjustable or movable parts

or elements that must be constantly maintained or replaced. The

various separate systems coupled together for cleaning, as well as the various movable parts increases the overall manufacturing and operating costs of the cleaning apparatus.

For example, existing apparatuses include elements or sections which must be constantly adjusted to wash screens of different sizes. While the apparatuses will wash short screens and

tall screens or narrow screens and wide screens, they must

constantly be adapted for each different screen size. As may be appreciated, the necessity of adjusting the apparatuses for different

size screens requires manual attention, and therefore, increases

labor and operating costs. Additionally, the various adjustable mechanisms associated with such systems are more expensive to manufacture thus increasing the manufacturing costs in addition to the increased operating costs.

Furthermore, the different integrated systems of the cleaning apparatuses include coupling and connecting points and associated seals which are often subject to wear and failure. For

example, the various fluid lines, valves, pumps and seals interconnected between the liquid supply and the cleaning chamber

may present potential points of leakage. In addition to the mess and waste associated with such leakage, the leakage may also

pose environmental concerns. The maintenance or replacement of the various separate system components further increases the overall costs associated with each cleaning apparatus. Still further,

the various separate and integrated systems increase the overall size of the cleaning apparatus and take up valuable floor space.

Cleaning liquid or solvent waste is also a problem with some currently available systems because the screens and the

frames often retain a certain amount of solvent when removed from the cleaning apparatus. Such excess solvent usually drips off of or is shaken from the screens and falls to the floor to be discarded or to evaporate. Therefore, solvent is constantly being removed from

the system and must be periodically replenished at an increased cost to the operator of the apparatus. The operator is also exposed

to the excess solvent.

Accordingly, and in view of the above background, there is a need for a screen cleaning apparatus which is versatile, durable, reliable and which may be manufactured and subsequently used at a relatively low cost. Specifically, it is desirable to provide a screen cleaning apparatus that does not have to be repeatedly

customized for different size screens. Furthermore, it is desirable for such a screen cleaning apparatus to utilize a minimum number

of physically separated systems which must be operably coupled to the apparatus to thereby reduce the number of connection points

and possible leaking or failure points in the system. It would also

be highly desirable to reduce the necessary maintenance of the

system while maintaining the desirable cleaning aspects. There is a

further need in the art to reduce the overall size of the screen

cleaning apparatus to efficiently utilize valuable floor space. There

is still a further need in the art to reduce waste associated with

excess cleaning solvent which clings to the screen and frame and

is discarded when it is removed from the cleaning apparatus.

Summary of the Invention

This invention solves the problems associated with

known apparatuses and methods for cleaning screens. The method

and apparatus of this invention also satisfy the aforementioned

needs that exist in the art as developed in the background of this

invention.

The screen cleaning apparatus of the present invention

includes an enclosed housing which forms a cleaning chamber for

receiving a printing screen and a plurality of spray nozzles

positioned inside the cleaning chamber to spray the screen with a

cleaning solvent or other cleaning liquid. An oscillating mechanism

is mounted within the cleaning chamber and moves the screen in an oscillating motion within the chamber in front of the spray nozzles. The oscillating movement and the plurality of spray

nozzles yields repeated and increased screen coverage with sprayed cleaning liquid to provide improved cleaning and removal of undesired printing inks and other contaminants from the screen and surrounding frame in a single cleaning cycle.

One embodiment of the oscillator screen cleaning

apparatus of the present invention utilizes two opposing pluralities

of spray nozzles wherein the individual nozzles of each plurality are arranged in opposing grid patterns at horizontally and vertically spaced-apart nozzle positions. The screen is oscillated between the opposing nozzle pluralities, and the grid patterns provide increased

screen coverage with the sprayed cleaning liquid or solvent. As the screen is oscillated, the entire screen area is constantly being sprayed with solvent. The opposing grids of spray nozzles are operable to deliver sprayed cleaning solvent to a screen at a rate,

for example, of about 60 to about 215 gallons per minute, depending on the machine size, to effectively clean the screen. A reservoir is positioned beneath the pluralities of

spray nozzles to catch used cleaning liquid which falls from the screen, and a pump coupled between the reservoir and the nozzles pumps the used cleaning solvent to the nozzles to thereby recycle the solvent. The high recirculation of the cleaning solvent provided

by the pump keeps the ink particles suspended in the solvent to prevent the reservoir from becoming clogged with ink sludge which would reduce its effectiveness. In addition, a reservoir which is

kept clean requires less maintenance. A filter coupled between the

pump and the spray nozzles removes filterable particles from the recycled cleaning fluid. The supply reservoir which holds the recycled cleaning solvent is also connected to a decantation drum

which receives used solvent from the reservoir and holds the solvent for settling of the suspended contaminants and subsequent decanting of the cleaning solvent for re-use. The cleaning apparatus is enclosed in a housing to prevent the cleaning solvent and solvent fumes from entering the atmosphere or area adjacent

the cleaning apparatus. Further, a vapor recovery system is coupled to the housing to remove vaporized cleaning solvent. In one embodiment of the present invention, the

oscillating mechanism moves the screen in an oscillating motion having a period of motion in the range of about 3 to about 20 inches, and preferably around 10 inches. The mechanism operates to move the screen in a complete cycle of the oscillating motion (i.e., forward and then backward) approximately 20 times per minute. The continuous oscillation of the screen in combination with the opposing grids of spray nozzles provides repeated

application of the spray pattern onto the screen for excellent

cleaning coverage. Furthermore, during the entire cleaning cycle of the oscillator screen cleaning apparatus of the present invention,

each area of the screen is continually being sprayed resulting in a faster more efficient cleaning cycle which does not have to be continually repeated as required with other known screen cleaning

apparatuses. The embodiment of the present invention thus provides rapid cleaning of ink and other printing materials from a printing screen and surrounding frame with the attainment of very clean screens and screen frames.

Another embodiment of the oscillator screen cleaning apparatus of the present invention also utilizes two opposing pluralities of spray nozzles wherein the individual nozzles of each plurality are arranged in opposing grid patterns at horizontally and

vertically spaced-apart nozzle positions. The screen is oscillated

back and forth between the opposing nozzle pluralities preferably in approximately 8-10 inch periods or ranges of motions and the grid patterns provide increased screen coverage with the sprayed cleaning liquid or solvent. As the screen is oscillated, the entire screen area is constantly being sprayed with solvent. The opposing grids of spray nozzles of the embodiment are operable to deliver sprayed cleaning solvent to a screen at a rate, for example, of

about 60 to about 215 gallons per minute, depending on the machine size, to effectively clean the screen.

For guiding screens of various heights, opposing

pluralities of fixed guide brackets are mounted to the pluralities of spray nozzles to provide guidance to the screen as it is oscillated. The opposing guide brackets define a narrow path therebetween and also between the spray nozzles for passage of the screen. The guide brackets maintain the screens generally perpendicular to the spray patterns or streams from the nozzles for effective cleaning. The brackets are mounted at an angle to the spray nozzles so as not to interfere with the spray from the nozzles. In accordance with the principles of the present invention, the guide brackets

support the screen from the side and thereby do not restrict the screen from the top frame edge. Versatility is increased because screens of various different sizes may be readily sprayed with the apparatus without constantly customizing the cleaning chamber.

Since the brackets are essentially fixed, an assembly of various moving parts is not necessary, thus reducing manufacturing costs and the labor costs associated with adapting the apparatus for

different screen sizes. The fixed brackets are also more durable, requiring very little or no maintenance or repair.

A reservoir is positioned proximate the spray nozzles and is integrated with the cleaning chamber to hold the cleaning liquid which is sprayed on the screen. The reservoir also holds

recaptured cleaning liquid falling from the screen. Particularly, the integral reservoir includes a sloping wall or tray positioned directly

beneath the spray nozzles and oscillating screen to catch the used cleaning liquid which drips therefrom. The integral sloping wall directs the used liquid into the reservoir and eliminates the need to

pump recaptured liquid from a separate tank. The integral reservoir thus reduces necessary piping and leakage associated with the

piping.

A vertically-oriented pump is coupled between the reservoir and the nozzles and pumps the cleaning solvent to the nozzles to thereby constantly cycle and recycle the solvent. A portion of the pump is mounted inside of the reservoir such that the cleaning liquid is pumped directly from the reservoir to the spray

nozzles. The internal pump of the invention reduces the number of exposed fluid lines, valves and seals which, in turn, prevents leaks

associated with failure of one of the lines, valves or seals.

Additionally, the internal pump prevents any leaks which may occur

as a result of a failure of the pump seal. Liquid from a line, valve

or seal leakage is directed back into the reservoir.

The pump is preferably a higher capacity pump, and

the high recirculation of the cleaning solvent provided by the pump

keeps the ink particles suspended in the solvent to prevent the

reservoir from becoming clogged with ink sludge which would

reduce its effectiveness and increase required maintenance. A filter

coupled between the pump and the spray nozzles removes filterable

particles from the recycled cleaning fluid. A dump valve in the line

between the pump and spray nozzles provides drainage of the

system into the reservoir. The supply reservoir which holds the

recycled cleaning solvent may also be connected to a decantation

drum which receives used solvent from the reservoir and holds the

solvent for settling of the suspended contaminants and subsequent

decanting of the cleaning solvent for re-use. The cleaning

apparatus is enclosed in a housing to prevent the cleaning solvent and solvent fumes from entering the atmosphere or area adjacent

the cleaning apparatus. Further, a vapor recovery system is coupled to the housing to remove vaporized cleaning solvent and to control odor associated with the cleaning procedure.

The oscillating mechanism moves the screen in an

oscillating motion having a period of motion in the range of about 3 to about 20 inches, and preferably around 8-10 inches. The

mechanism operates to move the screen in a complete cycle of the oscillating motion approximately 20 times per minute. The

continuous oscillation of the screen in combination with the

opposing grids of spray nozzles and the guidance of the screens by the guide brackets generally perpendicular to the nozzles provides repeated application of the spray pattern onto the screen for excellent cleaning coverage. Furthermore, during the entire

cleaning cycle of the oscillator screen cleaning apparatus of the present invention, each area of the screen is continually being

directly sprayed resulting in a faster more efficient cleaning period

which does not have to be continually repeated as required with other known screen cleaning apparatuses.

As may be appreciated, the screen is sprayed

repeatedly during a cleaning period using the present invention and when the period has ended, the screen and any associated frame

member will contain a significant amount of excess cleaning fluid. One embodiment of the invention further comprises a wipe down booth positioned proximate an open end of the enclosed housing. A screen is manually transferred to the wipe down booth after it is cleaned and excess cleaning liquid is removed, such as by a cloth

or a squeegee. The wipe down booth is configured to capture the excess cleaning liquid from the screen. The wipe down booth

includes a sloped floor and is operably coupled to the enclosed housing such that any excess cleaning liquid removed from the

screen is directed into the housing and subsequently into the reservoir. In that way, excess cleaning liquid is not wasted when the screen is removed from the enclosed cleaning chamber. The advantages of the apparatus include a high impingement

spraying system to improve ink removal; full screen and frame cleaning through oscillating motion; a low maintenance integral

reservoir tank to contain and recapture the cleaning liquid; a vertical pump contained within the integral reservoir to further

contain the cleaning liquid and prevent leaks and spills; high volume/low maintenance filter system to reduce nozzle maintenance; quick drain system to empty risers of product which decreases cycle time (no need to wait for nozzles to stop spraying);

air curtain venting system to reduce operator exposure to fumes; fixeα guide brackets for guiding various differently sized screens without requiring constant adaptation; and a wipe down booth

which captures excess cleaning liquid after the screen is cleaned and directs the excess liquid to the reservoir and adjustable stop guide for varying screen sizes.

The above and other objects and advantages of the

present invention shall be made apparent from the accompanying drawings and the description thereof.

Brief Description of the Drawings Fig. 1 is a side view, in partial cross-section, of an

embodiment of the oscillator screen cleaning apparatus of the present invention.

Fig. 2 is an end view of the embodiment of the present invention shown in Fig. 1 taken along lines 2-2 of Fig. 1 .

Fig. 3 is a side view in partial cross section of another embodiment of an oscillator screen cleaning apparatus in accordance with the principles of the present invention.

Fig. 4 is a cross-sectional view of the embodiment

shown in Fig. 3 along lines 4-4 of Fig. 3. Fig. 5 is a perspective view of a wipe down booth of the embodiment shown in Fig. 3. Fig. 6 is a cross-sectional view along lines 6-6 of Fig.

4 to illustrate the oscillating mechanism of the embodiment of Fig.

3.

The accompanying drawings, which are incorporated

in and constitute a part of this specification, illustrate embodiments

of the invention and, together with a general description of the

invention given above, and the detailed description of the

embodiments given below, serve to explain the principles of the

invention.

Detailed Description of Specific Embodiments

One embodiment of the oscillator screen cleaning

apparatus 10 of the present invention as illustrated in Fig. 1

includes an enclosed housing 1 2 which forms a cleaning chamber

14 therein for receiving a printing screen 1 6 (See Fig. 2) . Housing

1 2 is preferably formed of fourteen gauge stainless steel and is supported above a floor surface by legs 17. A plurality of spray

nozzles 1 8 are connected, via a supply line 20, to a reservoir 22

containing an amount of cleaning solvent or cleaning liquid 24.

Suitable cleaning compositions are disclosed in U.S. Patent No.

4,664,721 , and components of those compositions may also be

used as cleaning liquids, and such disclosures are incorporated herein by reference. The cleaning solvent 24 is pumped from

reservoir 22 by pump 23 through line 20 to nozzles 18 which spray the screen 16 with solvent to remove printing inks or dyes from the screen 16 so that the screen may be re-used. While screen 16 is being sprayed, an oscillating mechanism 25 moves screen 16 back and forth within chamber 14 in front of the spray nozzles 18 to more effectively and more efficiently clean the screen. Oscillating mechanism 25 comprises a push-pull device 26, which is connected to a movable track 28

which holds and supports screen 16 at a bottom edge 19 of the

screen (See Fig. 2). The push-pull device 26 is mounted on a support platform 27 which extends from the rear end 21 of housing

12, and push-pull device 26 includes an actuatabie plunger 29

which extends in a longitudinal direction with respect to housing

12. The plunger 29 of push-pull device 26 is coupled to track 28, and when the push-pull device 26 is actuated, the plunger slides the track 28 and screen 16 lengthwise back and forth inside housing 12 in an oscillating motion. The oscillating movement

provided by oscillating mechanism 26 ensures that the plurality of spray nozzles 18 repeatedly cover all areas of the screen 16 with sprayed cleaning solvent 24. Preferably, and as discussed in greater detail below, the plurality of nozzles 18 are arranged in two separate grid patterns one on each side of the cleaning chamber 14 to spray

both sides of screen 16 simultaneously. This provides improved

cleaning and removal of undesired printing inks and other contaminants from the screen 16. The floor 32 of housing 12 is sloped to form a funnel-shaped surface so that used sprayed

cleaning solution or solvent, which drips from the sprayed screen 16, falls against floor 32 and is drained into reservoir 22 through a drain opening 33. The collected solvent may then be pumped again back through line 20 and nozzles 18 to be resprayed against screen 16. In this way, the cleaning solvent 24 is re-used

repeatedly rather than wasted, thus resulting in substantial cost savings. The high capacity spray capability of the present invention ensures effective cleaning of screen 16 with the re-used spray as will be discussed in greater detail below.

To clean a printing screen 16, the screen is placed into housing 12 and cleaning chamber 14 through an access opening 34 formed in one end of housing 12. Access opening 34 is covered by a hinged door 36 or some similar closure to completely

seal the cleaning chamber 14 within housing 12. A drip pan 37 extends outwardly from the front end 39 of housing 12 beneath access opening 34 to catch cleaning solvent which drips from the

screen 16 when it is removed from the cleaning chamber 14 after it has been sprayed and cleaned. This prevents cleaning solution or

solvent 24 from being spilled on the floor surface and entering the environment. Inside the cleaning chamber 14, the bottom edge 19

of screen 16 is placed onto a movable track 28 which is moved back and forth or oscillated by push-pull device 26 of the oscillating

mechanism 25. Track 28 moves within a larger channel 38 and specifically slides lengthwise in channel 38. Channel 38 is

mounted longitudinally within housing 12 to support track 28 and screen 16 above the sloped floor 32 of housing 12. A layer 43 of

a low friction material, such as ultra high molecular density polyethylene (UHMDPE) is inserted between track 28 and channel

38 to ensure smooth movement and oscillation of track 28 within channel 38. As shown in Fig. 2, a top edge 35 of screen 16

engages a guide channel 40 which is suspended from a top wall 41 of the housing 12. The guide channel 40 ensures that the screen 16 is held generally vertically between the opposing grids of spray nozzles 18 for more effective cleaning of the screen. Guide

channel 40 also preferably includes a layer 45 of the low friction UHMDPE to ensure smooth movement of screen edge 39 along the guide channel 40.

The oscillating mechanism 25 moves track 28 within channel 38 and oscillates screen 16 back and forth in front of the opposing grids of spray nozzles 18. As mentioned, the oscillating mechanism 25 includes a push-pull device 26 such as a

pneumatically operated solenoid. Other mechanically oscillating devices might also be utilized in place of push-pull device 26. The device 26 is shown on the outside of the body 47, but also may be

mounted on the inside. The plunger 29 of the push-pull device 26

moves longitudinally in a straight direction inside a body 47 of the push-pull device 26 when the device is actuated, such as by pressurized air. The plunger 29 is coupled through a coupling fixture 48 to an arm 49 which is fixed at one end to track 28. Arm

49 extends into housing 12 through a liquid seal 50 which guides arm 49 to ensure a smooth, straight and generally longitudinal movement of arm 49 and track 28 inside the cleaning chamber 14. The liquid seal 50 protects from loss of cleaning liquid through hole

in housing 12. When the push-pull mechanism 26 is actuated, plunger 29 moves back and forth thereby pulling and pushing track

28 and oscillating screen 16 between the spray nozzles 18. Generally, push-pull device 26 of the present invention and arm 49 should be dimensioned to provide a range or period of motion of from about 3" to about 20" and preferably around 10". That is, it has been determined that movement of screen 16 in a

cycle of approximately 10" in a forward motion and then 10" in a rearward motion in accordance with the principles of the present invention provides excellent cleaning. However, greater or lesser

periods of motion might be utilized. Further, it has been

determined that an oscillator frequency of approximately 20 cycles per minute for the oscillating mechanism 25 of the present invention is a sufficient oscillating motion to provide an efficient

and effective screen cleaning. A single cycle of the oscillating

mechanism 26 involves moving the track 28 the full range or period

of the motion, e.g., 10", and then back again. Of course, a faster or slower oscillation frequency may be utilized as appropriate to sufficiently clean screen 16.

The oscillator screen cleaning mechanism of the present invention will now be described in greater detail with respect to its operation and the delivery of the sprayed cleaning solution or solvent 24 to the screen 16. Specifically, a cleaning

liquid or cleaning solvent 24 is placed in reservoir 22 which may be made of stainless steel and preferably has a capacity of, for

example around 55 gallons, depending upon the size of the

machine. A suitable cleaning solvent for cleaning printing screen

1 6 in accordance with the teachings of the present invention is

disclosed in U.S. Patent No. 4,664,721 . However, the oscillator

screen washing apparatus 10 of the present invention is not limited

to the use of a particular solvent, and other appropriate solvents

might be placed within reservoir 22.

When the oscillator screen cleaning apparatus 10 is

actuated, the solvent is pumped through the supply line 20 by

pump 23. Pump 23 is preferably a high capacity pump, to deliver,

for example, about 60 to about 21 5 gallons per minute, depending

on machine size as stated above. A short section 54 of supply line

20 connects reservoir 22 and pump 23 and includes manual valves

55 and 56 which may be closed to prohibit solvent 24 from exiting

reservoir 22 or draining back from pump 23, respectively, such as

when it is desirable to remove reservoir 22 for maintenance.

When valves 55, 56 are open, the pump 23 pumps

solvent 24 through line section 54 and up through a filter line

section 58 into a filter unit 59. Filter unit 59 removes foreign

particles and contaminants within the cleaning solvent 24 in line 20 before the solvent 24 is delivered to the spray nozzles 18. A suitable filter for such a purpose is the 50 micron bag filter which removes different materials such as tape, mesh, adhesive, dry ink

and stencil particles. Filter unit 59 allows the solvent 24 to be continually re-used to spray screen 16. As mentioned above, the

re-use of the solvent 24 amounts to a substantial cost savings, because the used solvent may be collected and filtered rather than

continually replaced with new solvent. After the solvent is filtered,

it is directed through line 20 to the spray nozzles 18. A valve 60 is connected in the supply line 20 and may be closed to prevent liquid

24 in line 20 from back flowing into filter 59 during filter

maintenance.

The supply line 20 branches at a point along its length, such as point 61 , to direct cleaning solvent to the spray

nozzles 18 on both sides of the cleaning chamber. Specifically, as shown in Fig. 2, the solvent is directed into supply branches 64, 66 located proximate the top of the cleaning chamber 14. The branches 64, 66, in turn, feed into pluralities of vertically extending

finger lines 68, 70, respectively, which are coupled to their respective supply branches 64, 66 and extend generally vertically

from the top of the cleaning chamber 14 to the bottom of the cleaning chamber. Referring now to Fig. 2, branch 64 feeds the

first plurality of finger lines 68 while branch 66 feeds a second

plurality of finger lines 70. Each vertical finger line contains a plurality of spray nozzles 18 arranged in a generally straight vertical line thereon. The nozzles 18 are vertically spaced apart along the lengths of each finger line. The individual finger lines of the

pluralities 68, 70 are horizontally spaced apart one from the other and extend generally parallel with each other from their respective supply branches. The finger lines of each plurality 68, 70 are also

generally co-planar with each other such that each plurality of finger lines 68, 70 defines a spraying plane of nozzles 18 as illustrated in Fig. 2. The spraying planes of nozzles 18 are

generally vertically oriented and are parallel the side walls, such as side walls 72, 73, of the housing 12. The combination of the horizontally spaced apart finger lines 68, 70 and the vertically spaced apart nozzles 18 creates opposing grids of spray nozzles 18 within cleaning chamber 14. The opposing grids of spray nozzles ensures that, while screen 16 is oscillated within the cleaning chamber 14, the entire screen area is constantly being sprayed with cleaning solvent 24 to effectively and efficiently clean the

screen. Referring again to Fig. 2, each nozzle 18 forms a

generally V-shaped flat spray pattern 75 on screen 16. Cleaning solvent impingement created by nozzles helps remove ink and dye residue. The flat spray pattern 75 is vertically oriented so that the horizontal oscillating motion provided by oscillating mechanism 25

moves the screen 16 perpendicular to the flat spray pattern of each

nozzle 18. The nozzles 18 of each finger line, such as finger line 74, are spaced along the finger line 74 to provide pattern overlap of the spray patterns. For example, nozzles 76 and 77 of finger

line 74 provide flat spray patterns 78, 79, respectively. The

nozzles 76, 77 are spaced such that their spray patterns overlap at area 80. The overlapping spray patterns ensure complete coverage of screen 16 with the sprayed solvent. A nozzle suitable for use within the present invention yields a spray pattern approximately

ten inches wide.

The oscillator screen cleaning apparatus of the present

invention is capable of delivering a high quantity of sprayed cleaning solvent to screen 16 during a cleaning cycle. Specifically,

the spraying system of the present invention, including high capacity pump 23 and the opposing grids of spray nozzles 18, is operable to deliver sprayed cleaning solvent to the screen 16 at a rate in the range of about 60 to about 21 5 gallons per minute. The

high solvent delivery rate and the continual coverage over the area

of the screen in combination with the oscillating screen motion of

the present invention yields a very efficient cleaning cycle.

As discussed above, the cleaning solvent 24 is

continually filtered and re-used within the oscillator screen cleaning

apparatus of the present invention. Specifically, the cleaning

solvent 24 sprayed onto screen 16 by nozzles 18 drips from the

screen and falls onto the sloped floor 32 of housing 12 where it is

directed through drain opening 33 back into reservoir 22. The used

solvent is again pumped through line 20 and filter unit 59 to be

directed to the grids of spray nozzles 1 8. As discussed, continual

re-use of the cleaning solvent yields substantial cost savings and the high spray capacity and suspension of ink particles within the

solvent ensures that the re-used cleaning solvent effectively cleans

screen 1 6.

After several cleaning cycles, the used solvent within

reservoir 24 may need to be recycled. To do so, the used solvent

may be transferred to a decantation tank either manually or through

a line and pump coupled to the reservoir 22. Referring now to Fig.

1 , in one embodiment of the present invention, decantation tank 82 is coupled to reservoir 22 through line 84 and pump 86. The used cleaning solvent is pumped into the decantation tank 82 wherein the ink and other contaminant particles which are suspended in the solvent are allowed to settle. The decanted solvent may then be removed from tank 82 and transferred back into reservoir 22 for

additional use within the oscillator screen cleaning apparatus 10.

The spraying system of the oscillator screen cleaning apparatus 10 of the present invention is configured to be quickly

drained when desired such as for decantation and recycling of the

cleaning solvent 24. Specifically, referring to Fig. 1 , each finger

line of the finger line pluralities 68, 70 terminates in a respective draining branch 90, 92. The draining branches 90, 92 extend

generally parallel to the respective supply branches 64, 66, respectively, and receive any solvent which is not sprayed through

the nozzles 18. The draining branches 90, 92 beneath the cleaning chamber 14 converge at point 94 and are connected through a dump valve 96 into reservoir 22. When the dump valve 96 is actuated, either manually or pneumatically, the entire system

including supply branches 64, 66 and finger lines 68, 70, is drained of cleaning fluid in approximately 5 seconds. This provides rapid draining of fingers to decrease cycle time and to reduce vapors in chamber.

Housing 12 completely encloses the finger lines 68, 70 and spray nozzles 18 to ensure that all of the cleaning solvent

24 is contained within cleaning chamber 14 and that little or none of the solvent escapes into the atmosphere or the environment

around the oscillator screen cleaning apparatus 10. This provides a safer, healthier environment for personal working near the cleaning

apparatus 10. Further, the housing 12 has a flue 98 formed in the top thereof which is coupled to a vapor recovery system 100

through an opening 102 in flue 98. The vapor recovery system ensures that vaporized solvent from cleaning chamber 14 does not escape into the atmosphere to be breathed in by workers, thereby further creating a more healthy work environment. A removable

cover 104 on the top wall 41 of housing 12 allows access to the cleaning chamber 14 from above.

Figs. 3, 4, 5 and 6 illustrate another embodiment of an oscillator screen cleaning apparatus. The oscillator screen cleaning

apparatus 1 10 of the present invention as illustrated in Fig. 3 includes an enclosed housing 1 12 which forms a cleaning chamber

1 14 therein for receiving a printing screen 1 16 (see Fig. 4.) Housing 1 12 is supported above the floor surface by a skid 1 17. Skid 1 17 provides easy mobility of the cleaning apparatus 1 10. A

plurality of spray nozzles 1 18 are connected via a supply line 120 to a reservoir 122 containing an amount of cleaning solvent or

cleaning liquid 124. Suitable cleaning compositions are disclosed and discussed hereinabove. The cleaning liquid 124 is pumped

from the reservoir 122 to the supply line 120 and the nozzles 1 18 buy a vertically oriented pump 123. Pump 123 includes an intake

end 125 which is operably coupled to a motor 127 for drawing liquid through the intake end 125 and pumping it to the nozzles

1 18 to be sprayed therefrom.

In accordance with the principles of the invention, an

oscillating mechanism 128 is coupled to the chamber 1 14 for moving screen 1 16 back and forth within the chamber in front of the spray nozzles 1 18 to more effectively and efficiently clean the screen (see Fig. 6). Referring to Fig. 6, the oscillating mechanism 128 comprises a push-pull device 130 , such as a pneumatically

operated cylinder, which is connected to a movable track 132 that supports the screen 1 16 at a bottom edge thereof. The push-pull device 130 is mounted to a support structure 133 which extends

below the spray nozzles 1 18 in chamber 1 14. Push-pull device 1 30 includes an actuatable plunger 1 34 which is coupled to a tang

1 35 which depends downwardly from track 1 32. When the push-

pull device 1 30 is actuated, plunger 1 34 moves back and forth and

slides the track 1 32 lengthwise inside the cleaning chamber 1 14 in

an oscillating motion. An appropriate slot 1 37 is formed in the

support structure 1 33 to achieve movement of the tang 1 35 on

track 132. Preferably, opening 137 is dimensioned to allow an

oscillating stroke or period of approximately 8-10 inches. As

discussed above, the oscillating movement of the screen insures

that the plurality of spray nozzles 1 18 repeatedly cover all areas of

the screen 1 16 with sprayed cleaning liquid 124.

Referring to Fig. 3, the plurality of nozzles 1 18 are

preferably arranged in two separate grid patterns, one on each side

of the cleaning chamber 1 14, to spray both sides of the screen 1 1 6

simultaneously. The cleaning liquid 124 is pumped by pump 123

through the supply line 1 20 and through a filter 1 38 before it is

sent through the nozzles 1 1 8. The filter is preferably a 50 micron

bag filter which removes different materials such as tape, mesh,

adhesive, dry ink and stencil particles to allow the cleaning liquid to

be continually reused in the invention. To capture the sprayed cleaning liquid for reuse, the reservoir 122 includes an integrally formed sloping wall 140 which is positioned below cleaning chamber 1 14 to capture the sprayed cleaning liquid which drips from the screen and subsequently direct the captured liquid into reservoir 122. As illustrated in Fig. 3, the

housing 1 12 integrally forms both the reservoir 124, the cleaning

chamber 1 14 and the sloping wall 140. In that way, the entire system is enclosed to prevent loss of cleaning liquid and further to control fumes and odors and to reduce exposure of an operator to the cleaning liquid. Any fumes in cleaning chamber 1 14 are

directed through an outlet 142 which is preferably coupled to a vapor recovery system 145 or other venting system. A top opening 147 covered by lid 149 provides access to the cleaning chamber, such as for maintenance. In accordance with the principles of the present invention, the cleaning liquid is contained so that it may be reused and the prevention of cleaning liquid loss amounts to a cost savings for the operator of the invention. The integration of the

reservoir tank 122 with the cleaning chamber 1 14 eliminates the need for a separate reservoir tank which must then be coupled to

pump 123 through various supply lines, valves and seals which are subject to failure and leakage. Therefore, the integral reservoir 122 and chamber 1 14 of the present invention eliminates leakage and waste associated with the various valves and seals.

Additional linkage and waste is reduced by the vertically oriented pump 123 which is mounted inside of the reservoir 122. The internal pump having its intake end 125

positioned in the reservoir 122 eliminates the need for an external

pump and thereby generally eliminates any leakage from the system associated with the failure of a pump seal or other pump components. Any leakage from the pump will be contained within the reservoir 122 until the pump or seal can be repaired. The combination of the integrally formed reservoir 122 and vertically oriented pump 123 reduces cleaning liquid loss from the system, amounting to a cost savings and further preventing operator exposure and the mess associated with such leakage. The

invention also reduces labor costs associated with containing and

cleaning a spill or leak.

To clean a printing screen 1 16 in apparatus 1 10, the

screen is placed in the housing 1 12 and cleaning chamber 1 14 through an access opening 146 covered by a door 148 or a similar closure to completely seal the cleaning chamber 1 14. The cleaned screen is also removed through the access opening 146. A drip pan 150 extends outwardly from the housing beneath the access opening 146 to catch cleaning liquid which drips from the screen 1 16 when it is removed from the cleaning chamber 1 14 after it has

been sprayed and cleaned. Furthermore, the drip pan 150 provides coupling to a wipe down booth 152 which further captures excess

cleaning liquid from the screen and directs it to the reservoir 122 as described further hereinbelow.

The screen is positioned on movable track 132 to be oscillated back and forth by the oscillating mechanism 128 (see

Fig. 6). Referring to Fig. 4, the movable track 132 moves or oscillates within a larger channel 154 and specifically slides

lengthwise within the channel 154. Various strips of low friction material 156 such as Teflon^® are positioned between the channel 154 and movable track 132 at the sides and beneath the track 132 to insure movement and oscillation of the track. The oscillating

mechanism preferably moves the screen at approximately 20 cycles per minute to provide efficient and effective screen cleaning.

A cycle comprising full movement of the screen in one direction and then back, i.e., 10" forward and then 10" back. The oscillating mechanism 128, pump motor 127 and a dump valve 169 for draining the system are preferably coupled to

appropriate electrical controls and air controls The controls are preferably be positioned above or adjacent to reservoir 122 as illustrated in phantom in Fig. 3 by an electrical control cabinet 158 and air control cabinet 160. When the oscillator screen apparatus

1 10 is actuated at the beginning of a cleaning cycle, the solvent 124 is pumped by pump 123 through the supply line 120. Pump 123 is preferably a high capacity pump to deliver, about 60-215 gallons per minute depending upon the requirements for the screens being cleaned. The supply line branches at point 162 to provide fluid to various riser lines or finger lines 164 which support the nozzles 1 18 to form opposing spray nozzle grids. The pumped fluid is directed up the riser lines 164 and through the nozzles 1 18 to spray both sides of the screen 1 16 as illustrated in Fig. 4 by the spray patterns 166. The spray patterns 166 are preferably vertically oriented and overlap vertically one with the other to provide complete coverage of screen 166. The nozzles 1 18 are

preferably maintained generally co-planar in vertical planes within each grid by the riser lines 164. In that way, spraying planes are defined by the nozzle grids and the spray planes coincide generally in the center of the cleaning chamber 1 14 where the screen passes (See Fig. 4). As the screen 1 16 is oscillated between the spraying grids, the entire screen area is constantly sprayed with cleaning liquid 124 to effectively and efficiently clean the screen.

For effective cleaning, the screen is preferably guided between the nozzle grids generally parallel to the grids and

perpendicular to the spray patterns 166. The oscillator screen cleaning apparatus 1 10 readily accepts screens which have

different sizes. While the screen 1 16 is oscillated by the contact of its bottom edge with track 132, the top edge 168 of screen 1 16 is

not engaged or otherwise restricted. In that way, screens with various heights and widths may be cleaned without constantly adapting the apparatus 1 10. In accordance with the principles of the invention, adjustably fixed guide brackets 170 are mounted to

the various riser lines 164 of the spray nozzle grids. Referring the

Fig. 4, each bracket 170 is preferably U-shaped and extends vertically with the riser lines 164 at an angle thereto (See Fig. 3). For example, guide bracket 170a extends at an angle between riser line 164a and riser line 164b. The brackets are angled between the riser lines 164 so as to not interfere with the spray from spray nozzles 1 18. The guide brackets 170 engage the sides of the screen 166 to guide it and maintain it in an upright position. Preferably, pairs of guide brackets 170 are mounted between the

opposing spray nozzle grids as illustrated in Fig. 4 to cooperate and confine the screen 1 16 between the nozzles in a plane generally parallel with the planes of the nozzle grids. The fixed guide brackets 170 extend between each riser line 164 and thus maintain

the screen in an upright vertical position while being oscillated in the cleaning chamber 1 14. Thereby, the screen 1 16 is maintained in a proper position for cleaning without restricting the screen upper edge 168. The adjustably fixed guide brackets 170 eliminate the need for constantly adjusting a guide mechanism to customize the cleaning apparatus 1 10 for screens of different heights and/or widths As will be appreciated, the guide brackets 170 of the invention reduce the cost of manufacturing the apparatus because they eliminate specially fabricated adjustable parts which are subject to wear and subsequent replacement. Furthermore, labor costs are reduced because an operator is not required to adjust the

guide brackets 170 every time a different sized screen is being

cleaned. Furthermore, the oscillating screen cleaning apparatus 1 10 utilizing guide brackets 170 is more durable and eliminates maintenance normally required with an adjustable screen guiding assembly.

Referring again to Fig. 4, the ends of the U-shaped guide brackets 170 are preferably threaded and are held to the riser

lines 164 by nut pairs 172 which fit on a threaded portion 173 at the end of each guide bracket 170. In that way, the fixed guide

brackets 170 may be adjusted inwardly or outwardly as necessary with respect to the spray nozzle grids for handling screens with

different widths. It is anticipated that such adjustment will not often be necessary but is available in accordance with the

principles of the present invention to adapt the apparatus to wash unusually wide screens.

Referring again to Fig. 4, each nozzle 1 18 forms a generally V-shaped flat spray pattern 166 which is vertically

oriented so that the horizontal oscillating motion provided by oscillating mechanism 128 moves a screen 1 16 perpendicular to the flat spray pattern. The nozzles 1 18 are spaced along each riser line 164 to preferably provide pattern overlap of the spray patterns

166 for a full spray coverage of the screens. A suitable spray nozzle 1 18 would produce a spray pattern of approximately 10 inches wide. The cleaning solvent 124 is continually filtered and re-used within the oscillator screen cleaning apparatus 1 10.

Specifically, a major portion of the cleaning liquid 1 24 sprayed onto

screen 1 1 6 will drip from the screen 1 1 6 and fall onto the sloped

wall 140 to be directed back into reservoir 1 22. While most of the

liquid will drip from the screen in the cleaning chamber 1 14, the

screen and any frame utilized therewith will usually retain a certain

amount of liquid. It will be appreciated, that the surface tension of the liquid often fills the small squares of a screen and is held

therein. The liquid is removed or evaporates from the screen when

it is taken from the cleaning apparatus 1 10 and is irretrievably lost

from the system thereby increasing frequency at which the cleaning fluid must be replenished and increasing the cost of

operation. The present invention utilizes a wipe down booth 1 52 to

capture and recirculate residual cleaning liquid from the screen 1 1 6

after it is removed from the cleaning chamber 1 14.

Referring to Fig. 5, the wipedown booth 1 52

comprises a back wall 176, a side wall 1 77, and a sloping floor

178. The top 1 79 of booth 1 52 is open as is the side 1 80 closest

to the cleaning apparatus 1 1 0 and the front 1 82 of the booth. The

front 1 82 of booth 1 52 includes a short wall 1 84, preferably 3

inches, high, which contains fluid runoff from a screen placed in the wipedown booth. The sloped floor 178 feeds to a drainage lip 186 which couples to the drip pan 150. Floor 178 slopes in the

direction of the cleaning apparatus 1 10, and therefore any accumulated liquid flows down floor 178 to lip 166 and into drip

pan 150 and subsequently to the sloping wall 140 where it is drained into reservoir 122. Booth 152 is supported on legs 188

which may be appropriately adjusted as necessary to change the height of the booth and to couple the lip 186 and drip pan 150 together for proper liquid flow. When screen 1 16 is removed from the cleaning

apparatus 1 10 through opening 146, it is immediately slid into the wipedown booth 152. Therein, the excess cleaning liquid and any residue are wiped off of the screen, such as with a squeegee, and the excess liquid drains to the reservoir 122 as previously

described. The screen 1 16 can then be wiped off and dried, such as with a cloth. The side wall 177, back wall 176 and short front wall 184 ensure that the excess liquid is contained and

appropriately drained back into the cleaning apparatus 1 10 and the reservoir 122. In that way, excess cleaning fluid is not wasted, resulting in greater cost saving to the operator. Furthermore, with less wasted liquid, the reservoir 1 22 does not have to be refilled as

often.

The spray system of the oscillator screen cleaning

apparatus 1 10 is configured to be quickly drained, such as for

decantation and recycling of the cleaning liquid 1 24. To that end,

a dump valve 1 69 is coupled in the supply line 120 between filter

1 38 and the spray nozzles 1 18. When the dump valve 169 is

actuated, either manually or pneumatically, the entire system,

including the liquid and supply line 1 20 and the riser lines 1 64 are

drained directly into the reservoir 122.

While the present invention has been illustrated by a

description of various embodiments and while these embodiments

have been described in considerable detail, it is not the intention of

the applicants to restrict or in any way limit the scope of the

appended claims to such detail. Additional advantages and

modifications will readily appear to those skilled in the art. The

invention in its broader aspects is therefore not limited to the

specific details, representative apparatus and method, and

illustrative example shown and described. Accordingly, departures

may be made from such details without departing from the spirit or

scope of applicant's general inventive concept.

Claims

What is claimed is: Claims

1 . An apparatus for cleaning a screen with a sprayed

cleaning liquid comprising:

a housing forming a cleaning chamber for receiving a

screen;

a plurality of spray nozzles positioned inside the

cleaning chamber to spray, with cleaning liquid, the screen within

the chamber;

a supply reservoir coupled to the plurality of spray

nozzles for supplying cleaning liquid to the spray nozzles;

an oscillating mechanism to move said screen in an

oscillating motion within said cleaning chamber in front of the spray

nozzles to clean the screen; whereby the oscillating movement and plurality of

spray nozzles yields repeated and increased screen coverage by the

sprayed cleaning liquid for improved cleaning and removal of

undesired contaminants from the screen.

2. Apparatus as in claim 1 further comprising another plurality of spray nozzles positioned inside the cleaning chamber to

oppose the one plurality of spray nozzles, the nozzles of the one plurality operable to spray in a direction opposite the nozzles of the

other plurality and the oscillating mechanism operable to move said screen between the opposite pluralities of spray nozzles for further improved cleaning of the screen.

3. Apparatus as in claim 2 wherein the spray nozzles of both of said opposing pluralities are arranged in opposing grid

patterns of horizontally and vertically spaced-apart nozzles to provide increased screen coverage when spraying the cleaning liquid.

4. Apparatus as in claim 1 wherein the reservoir is positioned below the height of the spray nozzles to catch used cleaning liquid which falls from said screen when the screen is sprayed, the apparatus further comprising a pump coupled to the reservoir to supply the used cleaning liquid to the spray nozzles

thereby recycling the cleaning liquid.

5. Apparatus as in claim 4 wherein the pump and the

spray nozzles are operable to deliver sprayed cleaning liquid to said

screen at a rate in the range of about 60 to about 21 5 gallons per

minute to more effectively clean the screen and to suspend

contaminants within the cleaning liquid for further effective

cleaning of said screen.

6. Apparatus as in claim 4 further comprising a decanting

reservoir coupled to the supply reservoir to receive used cleaning

liquid from the supply reservoir and hold the used cleaning liquid to

settle suspended contaminants for subsequent decanting.

7. Apparatus as in claim 4 further comprising a filter

coupled between the pump and the pluralities of spray nozzles to

remove filterable particles from the used cleaning fluid before the

fluid is sprayed onto the screen.

8. Apparatus as in claim 1 wherein said reservoir is

coupled to the cleaning chamber to catch used cleaning liquid

which falls from said screen when the screen is sprayed thereby

recycling the cleaning liquid.

9. Apparatus as in claim 8 wherein said reservoir includes a sloped wall for catching the used cleaning liquid beneath the screen and directing the liquid to an accumulation area in the reservoir.

10. Apparatus as in claim 1 further comprising guide brackets mounted in the housing for engaging and guiding the screen during oscillation, the guide brackets operable to engage a side of the screen and leave a top edge of the screen unrestricted such that screens of different heights may be cleaned while the brackets remain fixed; whereby screens of different heights are readily

washed in the apparatus without attention to manual adjustments to the apparatus by an operator thereby resulting in cost savings.

1 1. Apparatus as in claim 10 wherein said nozzles are positioned on either side of the chamber to spray the screen from opposing sides, the brackets extending into the chamber between

the nozzles to guide the screen generally perpendicular to the spray cleaning liquid from the nozzles.

12. Apparatus as in claim 1 1 wherein the brackets are positioned as cooperating pairs of brackets, one on either side of said chamber, a space being formed between the brackets for

passage of the screen.

13. Apparatus as in claim 12 wherein the brackets are adjustable horizontally to be moved away from each other to widen the space therebetween for accommodating screens of different

widths.

14. Apparatus as in claim 1 further comprising a pump

coupled to the reservoir to supply the cleaning liquid to the spray nozzles, a portion of the pump positioned inside the reservoir for reduced leakage during screen cleaning.

15. Apparatus as in claim 1 wherein said oscillating mechanism includes a moving track to hold one edge of said screen and move said screen in the oscillating motion and a guide track to

receive another edge of said screen and hold said screen in a position to be sprayed by the spray nozzles while the screen is

oscillating.

16. Apparatus as in claim 1 wherein the spray nozzles of the first plurality are arranged in a grid pattern of horizontally and

vertically spaced-apart nozzles to provide increased screen coverage when spraying the cleaning liquid.

17. Apparatus as in claim 1 wherein the oscillating

mechanism moves the screen in an oscillating motion having a period of motion in the range of about 3 inches to about 20 inches.

18. Apparatus as in claim 1 wherein the cleaning liquid is

a solvent.

19. Apparatus as in claim 1 wherein the housing completely encloses the cleaning chamber and spray nozzles to

prevent the cleaning liquid from entering the atmosphere.

20. Apparatus as in claim 1 wherein the oscillating mechanism moves the screen in a complete cycle of the oscillating motion approximately 20 times per minute.

21 . Apparatus as in claim 1 further comprising a vapor recovery system coupled to the cleaning chamber to remove cleaning liquid which is vaporized during the cleaning of said screen.

22. Apparatus as in claim 1 further comprising a wipe down booth positioned proximate said cleaning chamber, the wipe down booth configured for receiving a cleaned screen from the

chamber and capturing excess cleaning liquid dripping from the

screen.

23. Apparatus as in claim 22 wherein the wipe down booth is coupled to said cleaning chamber and directs the excess cleaning liquid back into the chamber.

24. Apparatus as in claim 23 wherein the wipe down

booth includes a sloping wall for directing the excess cleaning liquid back into the chamber.

25. A method for cleaning a screen with a sprayed cleaning liquid comprising: placing a screen within a cleaning chamber proximate a plurality of spray nozzles positioned inside the chamber; supplying cleaning liquid to the spray nozzles to spray

the screen and remove contaminants therefrom; and moving said screen in an oscillating motion proximate the spray nozzles whereby to increase the coverage of the sprayed cleaning liquid over said screen for improved cleaning and removal of undesired contaminants from said screen.

26. The method of claim 25 wherein the cleaning chamber

includes another plurality of spray nozzles opposite the one

plurality, the pluralities of spray nozzles spraying cleaning liquid in

opposite directions, the method further comprising moving said

screen between said spray nozzle pluralities to clean the screen

from both sides.

27. The method of claim 25 further comprising spraying

the cleaning liquid on said screen at a rate in the range of about 60

to about 21 5 gallons per minute.

28. The method of claim 25 further comprising spraying

the screen with the spray nozzles of the plurality arranged in a grid

pattern of horizontally and vertically spaced-apart nozzles to

increase the screen coverage of the sprayed cleaning liquid as the

screen is oscillated proximate thereto.

29. The method of claim 25 further comprising collecting

used cleaning liquid after it has been sprayed on the screen and supplying the used cleaning liquid to the spray nozzles whereby to

recycle the cleaning liquid.

30. The method of claim 29 further comprising filtering the used cleaning liquid before supplying the used cleaning liquid to the

spray nozzles.

31 . The method of claim 25 further comprising moving

said screen in an oscillating motion with a period of motion in the

range of 3 inches to 20 inches.

32. The method of claim 25 further comprising moving

said screen in a complete cycle of the oscillating motion

approximately 20 times per minute.

33. The method of claim 25 further comprising recovering

cleaning liquid which has been vaporized during the cleaning of said

screen.

34. The method of claim 25 further comprising the step of

engaging the screen at its sides and guiding the screen in front of

the spray nozzles during oscillation without restricting a top edge of

the screen such that screens of different heights may be readily

cleaned.

35. The method of claim 34 further comprising spraying the screen on both sides thereof and guiding the screen with guide

brackets extending into the chamber from both sides thereof to guide the screen generally perpendicular to the sprayed cleaning

liquid from the nozzles.

36. The method of claim 25 further comprising pumping cleaning liquid to the spray nozzles from a reservoir using a pump

and positioning a portion of the pump inside the reservoir for reducing leakage during screen cleaning.

37. The method of claim 25 further comprising wiping a cleaned screen down within a wipe down booth positioned proximate said cleaning chamber for recapturing used cleaning

liquid..