CA1059831A - Metered spray dampening system - Google Patents

Abstract

Ab~tr~ct _.
A ~ultiple ~pr~y noz~le~ orr~et press da~penlng 8y8-te~ or the type havlng lndl~ld~al ~eterlng pu~p~ ror the re-spectlve noz~le~ utilize~ ~ devl~e ~or opening the pu~p output vslvea ~hlle ~alntalnlng ~a~penlng liquld reed pressure sub-stantl~lly elev~ted, thzreby purglng reed llnes, pump p~s~ge~
~ays ~nd pu~p cha~ber~ o~ bubbles a~d p~rtlcles ~hlch Yould interrere ~ith ~ccuratc ~terlng. Con~tant reclrculatlon and ~ilteri~e o~ the ~eed liquld ~nde~ pressure ~ain~ainB purglng llquld subst~ntl~lly bubble and partlcle rree.

Description

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This lnvention relate~ to dampening apparatus ~or o~fset printing presse~ of the type utilizlng individual metering pump5 for a pluraliky of spray no~zles, and more particularly, to lmprovements in the liquid feed sy~tem there-~or.
The concept o~ multlple æpray no~æle dampenlng sys~
tems wherein individual metering pumps are provided for ~ -respective nozzles wa~ disclosed i~ United States Patent No.
3,651~756, issued March 28, 1972, and constituted a signi~icant advance in the lithographic dampening art in that it permitted ~ine control f'or optimum dampening under highly varied condi-tions of press speed, paper and lnk requirements. The apparatus di~closed therein has been highly satis~actory for a substantial range o~ printing requiraments, howe~er9 control was occa~ionally found to b~ ln~dequate for produr~ng ex~
tremely high guality ~rinting, as on ~ine, coated papers.
It has now been determined that at least a portion of the con-trol inadequacy haæ been caused by tlle formation of tiny :~
bubbleæ which collected within the metering pumps during and ~ ;
20 betwee~ printing run~ and slightly interferred with the ac- ;~
curacy of' pump dischargel, Also, partlcles of solid matter in the liquid are believed to occasionally interfere with pump valves, ~urthex c~ntributing to unwanted pump output varia~
tion~
The gross bubble problem wa~ prev~ously recognized . , and~ a~ de~cribed in said Patent ~o~ 3,651,756, 6ystem priming ~tructure was provided to elimlnate bubbles contained in the pump output chamber~ where khey tended to congregate.
Howe~er, the use of such a priming device presented cerkain diYficultie3, ~or example, during a ~ery high quality printing .

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run it would tend to vary mol~ture clelivery to an extent which is unacceptable. Also~ bubbles or particles upstream from the pump output chambers would be unaffected by the priming and potentially troublesome shortly thereafter. me ~mprovement described herein involves a two-part approach to avoid said difficultie~ by (1) utilizing a substantial ~ncrease in moisture feed pressure upstream from and within the metering pump, thereby substantlally inhibi~ing any tendency for bubble formation or entry in the metering pumps~
along with providing a devlce for selectively opening the pump output val~es while maintaining Raid increased pressure, thereby purging ~eed lines, pump passageways and pump chambers o~ bubbles and particles within and adjacent the pumps. The improvement still ~urther preferably utilizes constant cir-culation or reclrculation of the feed liquid from the vl-cinity of the pump inputs to the liquid source through a ~ilter medium to further reduce the chances of contamination b~ physical, chemical or biologlcal agents.
The principal ob~ects of the present invention are:
to provide a dampening apparatus ~nd method for offset print~ng presses which permit extremely ~ine and dependable moisture flow control suitable for the highest quality print-ing, to pro~ide ~uch apparatus which is relatively inexpen sive to manufacture and ea ily adapted to the prln~ing press;
to provide such an apparatus and method which substantially ~ ;
reduces or ellminates metering pump output varlat~ns caused by ~bbles or ~oreign particles within pump chamberæ; to provide such apparatus which may easily be added to both new and existing multi-pump, offset press dampenlng systems; and 3o to provide such apparatus which is highly reliable and re-~5~33~.
qulxes a ninimum an~unt of attention ~or operation and n~ain~en3nce.
Accord mg to the mv~ntion, there is provided gor use in combination with an offset pxintmg press: (a~ a li~hDgraphic dampener system having n~ltiple nozzles f0d by individual meter-ing pumps, (b) said metering pu~ps respectively inclu~ing an input p~rtion and a loaL~3d output valve, (c) a source of db¢Ferdng liquid, (d) regulated pump ~ ns operably connecb3d to said s3urce and ~aeding ~aid m~tering pu~p input portion with da~pen mg liquid at a feed pressure el~vated above atmospheric an amoun~ suficient to suFpress the fc~mation of ~ubbles and less than the pressure requir~d to open said output valve, and (e) neans for seles*ively n~intaining said output valves sin~
ltaneously in an open position independently of pu~p function, whereby bubhles and particulabe matter in said d ~ g liquid are driven ky said feed pressure through said pu~ps and past said output valves.
~oco~ding to another aspect of the invention, ~here is provided the method of supplying da~pening liquid ~o a litho- :
-graphic printing press dampener of ~he type h~ving a plurality of nozzles re~pectivel~ ed by individual metering pu~ps which include an input portion and a loaded output valve, the StPpS
oc~prising: (a) pumping said liquid prior to entry into said input portions to a fe2d pressure elevat0d above atmDspheric an amDunt sufficient to su~press th~ for~ation of kubbles and kelow the pressure required to ope~ said output valves, and (b) selectively maintaining said ou~put valves simLl~anRousl~ in an open position in~lependently of pump fuNction where~y bubbles and particulate matter in said liqyid æ e driven ~y said feed pressure throu~h said pu~ps and past said output valves.
Okher objects alld advantages of this invention will " .

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become apparent from the following description taken in connection with the accompanying drawings wherein are set forth, by way o~ illustration and example, cextain embodiments of this invention.
Fig. 1 is a partially schematic, perspective view showing a spray dampening system embodying this invention, : spray apparatus for three printing towers being illustrated.
Fig. 2 is a partially schematic, fragmentary, side elevation showing the system in conjunction with a typical 10 printing tower. :~ i Fig. 3 is a fragmentary ~ide elevation, on a sub-stantially enlarged scale over Fig. 1, with portions broken away, illustrating the internal structure of a metering pump -:, .
~v incorporating valve opening structure of this invention. -;

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Fig. 4 ls a fragmentary pl~n view ~howing a bank of metering pw~ps and partially lllustrak~ng the ~low path for fluid recirculation.
Fig. 5 is a ~ragmentary, cross-sectio~al view, on a substantially enlarged scale over Fig. 1, illustratin~ a typical spray noæzle.
Fig. 6 ls a fragmentary~ cross-sectional view on a substantially enlarged scale o~er Flg. 3, showing said valve op~nlng structure in the Yal~e~open positlon.
Re~erring to the drawlngs in more detail:
The re~erence numeral 1 generally indlcates an example of improved dampenlng apparatus embodying this in-; vention. The apparatus 1 is illustrated ~or us0 on a rotary, :; -. o~set~ web prlntlng press 2 (Fig. 2) oP a conventional type - havlng an ink tra~er train 3 including an ink ~ountain 4, hard rollers 5-9 and relati~ely soft (e.g.~ rubber) rollers 10-17, By means of the ink transfer train 3, ink 18 in the ~ountain 4 is transferred and evenly distributed to a litho-~; graphic printing plate 19 on a plate roller 20. The ink 18 adheres to the plate 19 only at predetermined locations~ a~d the ink image thereby formed i8 tran~erred to a blanket cyllnder 21. The i~ag~ i8 deposited from the cylinder 21 upon a moving paper web 22 wh~ch is maintained ln plate con- ~
tact by means o~ an impression cyllnder 23. The rollers and ~ ~ :
cylinders above noted are driven directly or indirectly through t~pical preæs drive means (not shown) which synchro-nlze the described prlnting operation with addition~l print~
ing towers and ~ariou~ known operating devices ln a well-known manner, Referring to this invention, the apparatus 1 in-cludes a spray bar or member 25 mounted on respective towers of the press 2 adJacent the ink transfer train 3 and a pump ~ S~3~
assembly or member 26 mounted ln spaced relation to the 6pray member 25 but connected thereto with multiple, li~uid carrying hoses as described below.
The spray member 25 has an elongated body portlon 27 mounted cn the press 2 longitudinally adjacent selecked dampener rollers 28 and 29 (Fig. 2). The body portion 27 is suitably secured at opposite ends 30 thereof by mean~ of swingin~ support arm~ 31 suitably pivotally anchored to the frame of the prlnting tower.
The spray members 25 contaln conduits or passage- ~;
~ays (not shown) directing individual hoses 32 to respective ~ :
spray nozzles 33 (Fig. 5) which are secured in laterally ~ -spaced relation on the body portio~ 27 (Fig. 1). In this example, the spray nozzle 33 are directed generally toward the nip formed between the dampener rollers 28 and 29~ how-ever, it is to be understood that substantial variations in -~
the æpray dispoæition arrangement may be utilized, depending . .~ - . .
: upon many varlable factors and press designs, so long as the spray 34 remains operatively directed to travel toward the plate cylinder 19 (Fig. 2~.
The spray nozzles 33 are characterized a3 having unvalved liquid exit openings, as is more clearly described in said Patent No. 3,651,756. In this example, a blower 35 .
(Fig. 1) draws air through a cleaning filter 36 and directs - it~ under pressure, within a suitable duct system 37 to the spray members 25 for cooperation with metering pumps, des~
cribed below, to produce a flow of atomized liquid out of the respective spray nozzle~ 33.
The pump member 26 comprises a frame 41 mounted, in thi8 example, b~ means of a bracket 42 to a convenient locat~on on the frame of the tower in the vicinity of the spray member 25. The frame 41 includes a manifold block or ~C~59~
port-lon 43 (Fig. 3) into which the individual spray nozzle hoses 32 communicate as described further below, A separate pump valve retainer or block 44 is pro~lded ~or each o~ the nozzles 33 and includes a pump recess 45 extending thereinto ~rom an exterior surface 46, the recess 45 here being formed by a depression cast in a synthetic resin ~ramework. The blocks 44 are mounted by suitable screws 47 onto the mani-~old portion 43 with the recess 45 pressed against an ex-terior surface 48 of the manifold portion 43. A plurality Of bores 49 extend in laterally spaced relation through the manifold portion 43 and are respectively axially aligned with :~
the pump recesses 45. Flexible diaphragm seals or pump means 50 are positioned between the respective recess 45 and the bores 49, ef~ectively isolating them from each other.
Plungers 51 are reciprocally recei~ed in the re-spective mani~old portion bores 49 and exhibit a forward ~:
end 52 bearing against one side o~ the respective diaphragm seal 50. The bores 49 form a guide passageway for the plungers 51 and expand near the surface 48, producing a seat for supporting the edges of the diaphragm seals 50.
The plungers 51 include diametrically reduced ~ ~`
projections 53 extending axia~ly opposite to the ends 52 and beyond the exterior sur~ace 54 of the manifold portion 43.
The pro~ections 53 are received into sockets 55 located in ~ :
drive ends 56 o~ respective rocker arms 57. The rocker arms 57 each have an adjusting end 58, opposite ~rom the drive end 563 and containing a socket 59 opening laterally in the same direction as the socket 55. A fulcrum rod 60 is suitably anchored with respect to the ~rame and extends along the mani-~old portion 43, engaging the rocker arms 57 at points intermediate the ends 56 and 58.

The sockets 59 receive the tips 61 of ad~usting lOS9B33~
members 62, each havlng a handle 63 and a threaded extension 64 recei~ed in a threaded bore 65 extending through the mani~old portion 43~ The tips 61 bear against the rocker arm adjusting end 58, thereby ad~ustabl~ limiting the length : of the reciprocal stroke which can be taken by the respective plungers 51. A suitable detent 66 ls resiliently urged against the handle 63 and is selectively received in cir~
cumferentially æpaced notches 67 for maintaining the adjusting member in a desired rotary position~ but permitting easy re~
adjustment by manual rotation of the handle.
: A drive shaft 68 is rotatably mounted on the pump member 26 and extends along the respective rocker arms 57. ;~
A plurality o~ bearings 69 have eccentric inner races 70 and are spaced along the drive shaft 68~ aligned respectively with the arms 57. Cylindrical spacers 71 ~it over the ;
bearings 69 and are e~ectively positioned ad~acent the back side 72 o~ the rocker arm drive ends 56. The r~ces 70 are eccentric with the axis of the dr~ve sha~t 68, for example~
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`- 1/32 of an inch, whereby, upon proper adjustment, the rota- ; ~
2Q tion of the shaft reciprocally drives the plunger 51 through . ~
the rocker arm drive ends 56, although the spacers 71 may remain rotationally stationary. A suitable variable speed motor (not shown) is pre~erably mounted within the pump member 26 and in driving engagement with the shaft 68. The m~tor effects rotation o~ the shaft 68 at a desired spe~d ;. suitably associated with the speed of the prin~ing press by appropriate control circuits contained, for example, in an enclosure 73, rece~ving speed in~ormatlon ~rom a tachometer signal generator 74 rotated b~ the press drive (not shown). -In the ~a.lve block 44, a pin 78 is located in the pump recess 45 and bears against the ~ront surface o~ the diaphragm seal 50. The body o~ the pin 78 is received . .

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axially within a helical compression spring 29 which urges the pln against the seal by bearing against a wall support 80. The ~all support 80 and diaphragm seal 50 are spaced apart and sealed wlth respect to the pump recesq 45, forming a pump chamber 81 therebetween.
Lower and upper passageways 82 and 83, in thl~
example ~ormed by tubes integral with the balance of the ~ `
valve block 44~ communicate into the pump chamber 81 and also, respecti~ely, into an intake valve chamber 84 and an output valve chamber 85 formed ~n the respective lower and upper portions o~ the val~e block 44. The intake valve ~ .
chamber 84 has a valve seal or plug 86, here shown open but normally resiliently seated or loaded against a seal ring 86~ by means Or a helical spring 87 compressed thereagainst with a threaded seal plug 88. The intake valve chamber 84 communicates through a pump input portion, or bore 89, with a ~:
manifold passageway 90 (Figs. 3 and 5) ~ormed in the mani- .
~old portion 43. The manifold passageway 90 is branched along its length~ thereby communicating with each bore 8g in the respective valve blocks 44. The manifold passageway 90 is ~ed dampening liquid through a suitable plumbing ~itting 91 incorporating a manual ~hut-of~ valve 92 and communicating - `~
with a feed hose 93 described further below. The fitting 91 communicate~ with the man~fold passageway 90 through a passageway 94 (Fig. 3~ in the manifold block or portion 43.
The output valve chamber 85 has a valve seal or plug g9, here shown open but normally resiliently seated or loaded against a ~eal rlng 99' by means of a helical spring 100 bearing thereagainst through pressure exerted by a threaded plug 101 ha~ing a central passageway therethrough.
The passageway in the plug 101 provides communication between the valve chamber 85 and respective passageway 102 in the ~:
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~5;983:1 manlfold portlon 43. The passageways 102 receive :Input ends of the respective hoses 32, sealing therewit,h through ~` :
~: suitable "0" rings 103 ma~ntained in sealing engagement .
through pressure exerted by a block 104 secured to the mani- -~
fold portion 43 by screws 105. : ~ .
The output ~alve chambers 85 each ha~e a rod 106 :~
received partially thereinto and slidably sealed through :- :
suitable seal members 107. The rod 106 is movably supported in a barrel 108 threadedly retained in the block 44 and pro~
10 jects rearwardly of sald barrel, terminating in an external ~ `:
knob 109. An expanded skirt portion 110 is slidably received ; in a chamber 111 ~ormed in the barrel 108 and cooperates ~.' therewith to guide the rod 106 coaxially o~ the output valve ' chamber 85. A transverse bar 112 contain~ a downwardly open slot 113 receiving the respective knobs 109 therein and the heads 114 of air cylinders 115 to move the pistons 109 simultaneously mounted at opposite ends of the manifold portion 43. The air cylinders 115 are actua,ted through a comp~essed air line 116 (Fig. 1) to simultaneously move the rods 106 on ~:
demand reciprocally between the limited pos~tions illustrated by the full llnes and broken lines 117 (Fig. 6).
The forward portion 118 o~ the rod 106, which ex~
tends into the output valve chamber 85, has a diameter significantly smaller than said chamber 85, providing a free passageway 119 between the upper passageway 83 and the seal ring 99' (Fig. 7). The rod 106 further exhibits a nipple 120 projecting forwardly ~rom the ~orward portion 118 and, when the rod 106 i~ in the ~orward position illustrated by the ~ull lines in Fig. 63 through seal ring 99'. The nipple 120 i6 0~ smaller diameter khan the ins~de diameter o~
the seal ring 99', permitting a continuation of the ~ree passageway 119 therethrough regardless of rod position ln the _g_ .
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valve chamber 85. When the rod 106 i~ fully forward~ as determined, in this example~ by contact between the sklrt portion llQ anid chamber wall 121, ~he nipple 120 contacts and ; urges the valve plug 99 away from the seal ring 99'~ thereby opening the passageway 119 to ~he discharge hose 32. Thus, by operation of the air cylinders 115~ the loaded output valves of the metering pumps may be held open for an extended period independently of pump function.
The ~eed hoses 93 extend ~rom the fitting 91 and communicate with a main dampener liquid supply hose 125 which - is ~ed, in this example, ~rom a supply tank 126 through a filter 127, pressure pump 1283 check valve 129 and pressure ~-regulator 130~ The pump 128 is actuated, together with the blower 35 and the printing press drive~ by suitable press switches and controls 131 and 132 and ~unctions to raise the pressure in the hoses 125 and 93 to a predetermined amount above atmospheric. The check valve 129 prevents reverse flow, thus maintaining the pressure in the closed liquid feed system, even during periods when the pump 128 ls temporarily not actuated. The regulator 130 is utilized to adjustably control pre~sure downætream therefrom to a desired predetermined amount, however, it is to be understood that a sPparate regulator may be unnecessary i~ ^the output from the pump 128 is otherwise maintained (regulated) at the desired pressure.
The spring 87 in the ~ntake valve chamber 84 is ~;~
re~atively low in compressive force, bearing on the i~alve plug 86 lightly~ but suf~iciently to create a seal in absence of an overcoming ~orward differentlal pressure. In contrast~
the ~pring 100 bearing against the output valve disc 99 relatiYely strong whereby a relatively high pressure is re-quired within the pump ~or liquid ~low to occur past the valve plug 99 and into the hose 32.

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The pressure in the supp:Ly hose 125 and feed hoses 93 is controlled by the regulator :L30 to am amoun~ which is easily suf~lcient to compress the sprlng 87 and drive liquid past the intake valve plug 86 but insuf~icient to compress the spring 100 and drive liquid also past the output valve plug 99. Thus, elevated pressure is constantly maintained in the system from the supply hose 125 through the feed hoses 93, internal passageways and chambers of the valve block 44 to the inner face of the output val~e plug 990 The reciprocation ~ :~
o~ the respective plungers 51, through rotation of the drive shaft 68, produces added pressure within the pump arrangement, compressing the spring 100 and thereby opening the output i , .- valve plug 99 upon each pump stroke and producing accurately metered liquid flow out of the respective hose 32. However, ; pressure, even on the suction stroke does not fall below a . predetermined elevated amount above atmospheric within the ~ : pump due to the liquid feed pressure.
Thus, bubbles 133, which may tend to form from dis-~olved gas in the liquid due to liquid turbulence, temperature ~:
~ 20 changes, chemical reactlons and/or pressure drops, will be . suppressed, due to the elevated pressure3 ~ntil the liquid is ;~
past the output valve plug 99 where they will be harmlessly . -~
discharged through the nozzles 33 without inter~erence with ;~
the metered liquid dlscharge of the pump. ~ ~
The bar 112 and cyllnders 115 may be utilized, as ~ ~;
d~ired, to open the output valve plugs 99, thereby allowing the pressure in the suppl~ base 125 to urge the intake valYe .
plug 86 open and ~lush out any existing bubbles 133 or particulate matter 134 within not only the entire flow 3 passagew~ys and all the chambers o~ the pump9 but also : within the mani~old passageway 90 and ad~acent part~ of the feed base 93. Such a flushing ls especially indicated when ~ :

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the pres3 haæ not been operated for an extended perlod of time and pressure may have bled down in the liquid supply network The use o~ tha bar 112 is also sometimes desirable to supply the relatively heavy moisture demands immediately on start-ups~ however, such ~lushing will normally be unnecessary and undesirable during the press run.
Referring to Fig. 4, the manifold passageway 90 is connected ~o an outlet hose 135 which joins a return hose 136 whereby the unused or excess portion of the dampening ` 10 liquid is recirculated back to the supply tank 126. A suitable hose sr line restriction 137 is placed in the return hose 136 so that the desired pressure may be retained ln the system while reclrculation of excess liquid is obtained. ~ sol;onoid check valve 138 is also placed in the return hose 136 to block ~low completely when the press is deactuated, thereby pro-duclng cooperation with the check valv~ 129 ~or maintaining bubble inhibiting pressure in the l'Lquid ~eed system. With this ~low arrangement the excess liquid moving through the dampener feed system is constantly agitated~ recirculated and redirected through the filter 127, thereby further reducing the possibility o~ bubble formation, the introduction o~
solid particles into the pump5, growth of biological materials such as ~ungi, etc., which may interfere wlth proper system operation. ~
Although particular pressures with~n the system ~-may be varied, it has been ~ound that a suitable operational ~
arrangement utilizes a metering pump intake valve requiring ~;
one to two psig to open, a metering pump output valve re-quiring approximately 10 psig to open and a liquid pressure regulator set to rnaintain~ ln cooperation with the source feed pump, approximately 5 to 6 pslg in the liquld supply networkO

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It is to be understood that, although certain forms o~ this lnvention have been lllustrated and described, it is not to be limited thereto except insofar as such limitations are included in the following claims.

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Claims (12)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. For use in combination with an offset printing press: (a) a lithographic dampener system having multiple nozzles fed by individual metering pumps, (b) said metering pumps respectively including an input portion and a loaded output valve, (c) a source of dampening liquid, (d) regulated pump means operably connected to said source and feeding said metering pump input portion with dampening liquid at a feed pressure elevated above atmospheric an amount sufficient to suppress the formation of bubbles and less than the pressure required to open said output valve, and (e) means for selec-tively maintaining said output valves simultaneously in an open position independently of pump function, whereby bubbles and particulate matter in said dampening liquid are driven by said feed pressure through said pumps and past said output valves.

2. The dampener system as set forth in Claim 1 wherein: (a) said means for maintaining said output valves open comprise reciprocally mounted members positioned for contacting said output valves.

3. The dampener system as set forth in Claim 1 wherein: (a) a return passageway is connected between said input portions and said source of dampening liquid and directs excess dampening liquid back to said source.

4. For use in combination with an offset printing press, a lithographic dampening system, said dampener system comprising: (a) a spray member having a plurality of dampening liquid atomizing spray nozzles, individual dampening liquid output conduit means connected at one end thereof to said nozzles, (b) a pump member having a plurality of indivi-dual, bubble and particle sensitive, reciprocal metering pumps respectively including an input portion containing a loaded input valve and an out portion containing a loaded output valve loaded to a substantially greater opening pressure than said input valve and a pump pathway extending between said input and output valves, (c) said output conduit means being respectively individually connected at the other end thereof to one of said metering pump output portions whereby each spray nozzle is connected to a separate metering pump, said metering pumps respectively having reciprocating pump means communicating with said pump pathways between said input and output valves and alternately increasing and decreasing the dampening liquid volume of the respective pump pathway, (d) a source of dampening liquid susceptible to bubble forma-tion and particle inclusion therein, input conduit means connected between said liquid source and said respective input portions, a feed pump operably located in said input conduit means, (e) pressure regulator means associated with said feed pump and together controlling the feed pressure of said dampening liquid into said respective input portions to a point above atmospheric pressure an amount sufficient to suppress the formation of bubbles and greater than that re-quired to open said loaded input valve but less than the sum of the opening pressure of said input plus output valve, thereby causing said dampening liquid to be maintained substantially above atmospheric pressure during flow from said feed pump and through said metering pumps, whereby bubbles tending to form in said dampening liquid are urged to remain in solution permitting accurate metering by said respective metering pumps, and (f) means selectively maintaining said loaded output valves simultaneously in an open position independently of pump function, whereby bubbles and particulate matter in said damp-ening liquid are driven by said feed pressure through said pump pathways and past said output valves.

5. The dampener system as set forth in Claim 4 including: (a) a return passageway connected between said metering pumps and said source and directing excess dampening liquid back to said source, said return passageway forming with said source and input conduit means a recirculation system for excess dampening liquid, and (b) a filter in said recirculation system and aiding in maintaining said dampening liquid clean and bubble free.

6. The dampener system as set forth in Claim 5 including: (a) a restriction in said return passageway and aiding in the prevention of excess pressure drop upstream therefrom.

7. The dampener system as set forth in Claim 4 wherein: (a) a check valve is operably positioned downstream from said feed pump and upstream from said respective input portions, (b) said check valve inhibiting pressure drop be-tween said check valve and said respective output valves.

8. The dampener system as set forth in Claim 4 wherein: (a) said input valves are loaded to an opening pressure of approximately one to two psig, (b) said output valves are loaded to an opening pressure of approximately ten psig, and (c) said feed pump and regulator means maintain said feed pressure at approximately five to six psig.

9. The dampener system as set forth in Claim 4 wherein: (a) said means selectively maintaining said output valves open comprises a member reciprocally mounted in said metering pumps and positioned for selectively physically con-tacting said output valve.

10. The dampener system as set forth in Claim 9 wherein: (a) said reciprocally mounted member is a rod axially movable in said pump output portion and having a diameter less than said output portion permitting liquid flow axially thereof.

11. The method of supplying dampening liquid to a lithographic printing press dampener of the type having a plurality of nozzles respectively fed by individual metering pumps which include an input portion and a loaded output valve, the steps comprising: (a) pumping said liquid prior to entry into said input portions to a feed pressure elevated above atmospheric an amount sufficient to suppress the forma-tion of bubbles and below the pressure required to open said output valves, and (b) selectively maintaining said output valves simultaneously in an open position independently of pump function whereby bubbles and particulate matter in said liquid are driven by said feed pressure through said pumps and past said output valves.

12. The method as set forth in Claim 11 including the steps of: (a) pumping an excess of liquid to said input portion, (b) directing said excess liquid through a filter, and (c) recirculating filtered excess liquid to said input portions.