US3902416A

US3902416A - Moisture control for lithographic machines

Info

Publication number: US3902416A
Application number: US529454A
Authority: US
Inventors: Francis K Lake
Original assignee: AB Dick Co
Current assignee: AB Dick Co
Priority date: 1974-12-04
Filing date: 1974-12-04
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

A moisture dispensing assembly for a lithographic printing press includes a fountain roller having a sufficiently hydrophilic surface to pick up and retain water or the like liquid thereon and a wiper member having a flat surface of elastomeric material engaging the roller to meter a film of liquid onto the roller surface, from which proper quantities of liquid are transferred to the printing system. In addition to having the prior art capability of setting the angular position and pressure of the wiper with respect to the fountain roller surface, the wiper is mounted for movement along an arcuate path about the roller surface between the liquid pickup point and crown of the roller, thereby to change the position of the wiper with respect to the crown and compensate for splitting of the liquid thereat due to gravity. This insures better control of the quantity of liquid supplied to the printing system. In a preferred embodiment of the dispensing assembly, a liquid pump and filter arrangement is employed to maintain a proper level of liquid in a liquid supply trough in which the fountain roller is mounted for rotation. In another embodiment, dams or caps taking the form of plates are mounted on the ends of the fountain roller for engagement along an edge thereof with the elastomeric wiper. The end dams minimize the accumulation of liquid at the roller ends.

Description

United states Patent 1191 Lake 1 I K t 14 1 Sept. 2, 1975 [75] Inventor:

l l MOISTURE CONTROL FOR 52 U.S. c1 101/148; 101/350 51 Im. c1. B41F 7/26; B41L 25/02;

B4lL 25/12 [58] Field of Search 101/147, 148, 157, 169,

Primary Examiner-4. Reed Fisher Attorney, Agent, or FirmRonald .1. LaPorte; Peter S. Lucyshyn [57] ABSTRACT A moisture dispensing assembly for a lithographic printing press includes a fountain roller having a sufficiently hydrophilic surface to pick-up and retain water or the like liquid thereon and a wiper member having a flat surface of elastomeric material engaging the roller to meter a film of liquid onto the roller surface, from which proper quantities of liquid are transferred to the printing system. In addition to having the prior art capability of setting the angular position and pressure of the wiper with respect to the fountain roller surface, the Wiper is mounted for movement along an arcuate path about the roller surface between the liquid pickup point and crown of the roller, thereby to change the position of the wiper with respect to the crown and compensate for splitting of the liquid thereat due to gravity. This insures better control of the quantity of liquid supplied to the printing system. In a preferred embodiment of the dispensing assembly, a liquid pump and filter arrangement is employed to maintain a proper level of liquid in a liquid supply trough in which the fountain roller is mounted for rotation. In another embodiment, dams or caps taking the form of plates are mounted on the ends of the fountain roller for engagement along an edge thereof with the elastomeric wiper. The end dams minimize the accumulation of liquid at the roller ends.

12 Claims, 5 Drawing Figures MOISTURE CONTROL FOR LITHOGRAPHIC MACHINES BACKGROUND OF THE INVENTION Offset lithographic printing or duplicating involves the use of a master plate having hydrophobic, oleophilic image areas and hydrophilic, oleophobic nonimage areas. Ink and an aqueous solution are alternately applied to the master. in many cases from separate supplies, the ink adhering to the image areas and aqueous solution covering the non-image areas. Thereafter, the inked image may be transferred to a rubber offset blanket, and from there to a paper sheet to complete the process. The supply of aqueous solution in a lithographic printing machine usually includes a fountain roller having a hydrophilic surface, which is continuously wetted by water or the like liquid provided in a trough or pan in which the roller turns. A film of liquid deposited from the trough onto the roller surface is in turn transferred into the system to a form roller mounted in driving engagement with the fountain roller. From the form roller, the liquid is applied to the master. The amount of liquid applied in the process must be precise, in that too great or too small an amount thereof will affect the print quality.

To assure that a precise film of liquid is provided to the fountain roller and thus to the system, a wiper bar having a substantially flat, elastomeric band of material thereon, is sometimes used to shear down or meter the liquid layer deposited onto the fountain roller surface, thereby to obtain a desired film thickness thereon. Shear or wiper bar arrangements of the type described are shown in Us. Pat. Nos. 3,645,202, issued Feb. 29, 1972 and 3,749,012, issued July 31, 1973, in the name of the instant inventor.

While these wiper arrangements function satisfacto rily to meter a desired film of liquid onto the fountain roller surface, the range of adjustment of the wiper bars as shown in these patents is limited and as such the variation in the quantity of liquid supplied to the system is likewise limited. In the ease of the arrangements of the previously mentioned patents, the wiper bar is mounted only for slight, if any, movement about the periphery of the fountain roller. This is a disadvantage since, after metering takes place on the fountain roller, the film of liquid deposited on the roller surface must be carried upwards and over the crown or crest of the roller to the nip or line of engagement between the fountain and form rollers for transfer of the water to the latter. Because gravity tends to split the film of water on the fountain roller as the water passes over the crown of the roller, lesser or greater amounts of liquid are introduced into the system depending upon the placement of the wiper bar with respect to the crown. As such, it becomes an advantage to be able to select the position of the wiper bar along the periphery of the fountain roller relative to the crown thereof.

Another prior art US. Pat. No. 1,981,912 issued Nov. 27, I934, discloses an inking arrangement for a printing press wherein a series of oscillating scrapers are mounted for adjustment about the surface of an ink roller for engagement therewith. This patent describes many individual blades used to scrap ink from a roller surface, the blades being moved into and out of engagement with the roller surface by a cam operated arrangement as the roller is rotated. While this arrangement does disclose the adjustment of scraper blades about splitting will occur and the bar should be positioned further downstream of the roller crown. The movement required of the shear or wiper to accommodate these changes, is not provided in the arrangements of the patents mentioned heretofore. Consequently, uncompensatable splits in the liquid film may occur which can affect the introduction into the ink/liquid system of the precise quantity of liquid required.

In addition to the latter, positioning the shear or wiper bar about the periphery of the roller can be an advantage when using alcohol as an additive to the normal moisture solution, since the alcohol likewise changes the characteristics of the solution and as such splitting due to gravity, etc., can occur more readily.

The wiper bar arrangements of the type shown in the US. Pat. Nos. 3,645,202 and 3,749,012, conventionally employ a pair of arms which are held against the surface of the wiper bar opposite the fountain roller to press the elastomeric layer of the bar onto the fountain roller surface for metering water thereto. In most cases, manually operable screw type members are employed to provide pressure against the bar, one member on each side thereof. A third member is also used for adjusting the angle of the wiper bar with respect to the surface of the fountain roller.

When setting the proper pressure of the wiper bar with the three adjustable screw members, an operator must first adjust one member, then another, and so on until he believes he has provided the proper setting of all members to have provided .a correct adjustment of the bar pressure against the roller surface and a proper angular relation between the wiper bar and roller surface. This is tedious and time consuming, and because Of the multiple adjustments involved, can often be imprecise. This too can affect the amount of moisture supplied to the system and as such, the quality of the printed matter obtained.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present in vention to provide a new and improved moisture dispensing assembly for use in a lithographic duplicating system, which overcomes the drawbacks of prior art arrangements described.

It is another object of the present invention to provide a new and improved moisture dispensing assembly for a lithographic duplicator which is readily adjustable over a relatively wide range to provide a precise quantity of moisture to the printing system under varied conditions.

It is still another object of the present invention to provide a moisture dispensing assembly of the abovementioned type which required fewer adjustments than those required in existing systems for controlling the quantity of water introduced into the system.

It is yet another object of the present invention to provide in a lithographic printing system a new and improved water dispensing assembly which is simple in construction. easy to operate and which can be controlled easily to deliver a precise amount of moisture to the system regardless of the environmental conditions existing.

Briefly, a moisture dispensing assembly for use in a lithographic type printing machine according to the invention includes a trough into which an aqueous solution, such as, for example, water is supplied. In a preferred embodiment, a pump operated recirculation apparatus is employed to deliver a fresh water supply to the trough. The apparatus includes filtering means for removing paper lint and the like particles from the water to prevent them from entering the printing system. Water is pumped through one conduit from a reservoir into the trough and is carried back through a filter to the reservoir via a second conduit.

A fountain roller having a surface sufficiently hydrophilic to receive and retain water thereon, is mounted for rotation in the trough. The roller is positioned so that a lower portion thereof extends into the trough to pick up on the roller surface, water which is to be applied to the master plate during printing. The roller is made to oscillate longitudinally in a conventional manner.

A form roller is mounted for rotation in driving en gagement with the fountain roller and with the master cylinder of the machine. Thus, water picked up on the surface of the fountain roller is transferred to the form roller and from there to the plate to wet the hydrophilic areas thereof. Ink is supplied to the printing plate at a separate location through a conventional ink fountain arrangement.

A wiper assembly according to the invention is used to meter the water provided to the master or lithographic plate. A wiper in the assembly meters the correct quantity of water onto the surface of the fountain roller. The wiper assembly comprises a pair of support brackets. each mounted for pivotal movement at a first end thereofto an adjacent side frame of the duplicating machine. The mounting points of the support brackets coincide with the locations at which the ends of the fountain roller are mounted on the side frames. A wiper having a length slightly greater than the fountain roller is mounted for pivotal movement on an elongated bar extending parallel to the fountain roller. A pair of hanger arms are pivotally coupled at first ends thereof, to the wiper and to the free ends of the support brackets at the opposite ends. A cross bar extends between the hanger arms at the points of connection of the arms to the brackets to provide support thereto. Another elongated bar extends between the hanger arms and is located above the wiper. The wiper is fiat, having a elastomeric band of material thereon which engages the fountain roller surface to perform the metering function.

Also mounted on the support brackets is a thumb wheel controlled wiper positioning arrangement coupled to the third elongated bar on the wiper assembly. The function of the wiper positioning arrangement is to adjust the angular position of the wiper with respect to the surface of the fountain roller. This is accomplished by swinging the wiper adjacent the fountain roller so that the wiper pivots with respect to the surface thereof thus changing the angular position along the fountain roller surface.

A second, manually controlled arrangement applies the shear force or pressure against the wiper which causes the wiper to press against the fountain roller surface. The shcar force or pressure controls the metering of moisture onto the roller surface. The shear force control arrangement includes a pair of spaced arm members suspended downwardly from the ends of a first rod, the length of which is somewhat less than the wiper. The rod is coupled pivotally at its center to an elongated rod which extends between the support brackets. The rods are in parallel alignment. The elongated rod is pivotal at its ends with respect to the support brackets. The rod arrangement forms a universal joint so that the arms when moved toward the wiper provide a uniform force thereagainst. A single manually operated thumb wheel control is coupled to a third rod which is in turn connected to the first rod by means of torsion springs. Tightening of the thumb wheel causes the torsion springs to exert a force against the arms which in turn press the wiper against the fountain roller surface.

The entire wiper assembly, including the support brackets is, as described heretofore, mounted for pivotal movement adjacent the side frames of the duplicating machine so that the assembly can be pivoted toward and away from the fountain roller. This results in the wiper being movable along an arcuate path about the outer surface of the fountain roller between the crown of the roller and a position downstream therefrom toward the trough or lowest point of the roller whereat water is received on the roller surface. Apertures in the support brackets are provided for alignment with suitable apertures in the side frames of the machine for receipt of an elongated pin which maintains the wiper assembly in one of a predetermined number of operating positions.

The ability to position the wiper to various positions about the outer surface of the fountain roller, as well as to change the angle and pressure of the blade with respect thereto, permits excellent control of the supply of water to the lithographic master or plate, providing in turn, a better quality printing.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective of an offset lighographic duplieating machine including a moisture dispensing assembly according to the invention;

FIG. 2 is an enlarged side view of the moisture dispensing assembly according to the invention;

FIG. 3 is a rear view of the moisture dispensing assembly of FIG. 2;

FIG. 4 a perspective view of the moisture dispensing assembly of FIG. 3; and

FIG. 5 is a side view of a moisture dispensing assembly including fountain roller end dams for preventing a buildup of moisture at the extreme ends of the fountain roller.

DETAILED DESCRIPTION OF THE DRAWINGS:

Referring now to the drawings in greater detail wherein like numerals have been employed throughout the various views to designate similar components, there is illustrated in FIG. I, an offset lithographic duplicating machine. designated generally by the numeral 10, including a moisture dispensing assembly 12 according to the invention. The duplicating machine is, except for the moisture dispensing assembly, of a conventional design comprising a pair of side covers 14, 16 which encase the rollers and printing cylinders, such as plate or master cylinder 18 shown in FIG. 2. An ink fountain assembly 20 including ink fountain roller 22, form roller 24 and an oscillating roller 26 which aid in transferring a predetermined quantity of ink from the ink tray 28 to the master cylinder 18, is mounted at the left hand side of the press as shown in FIG. 1 of the drawing. The separate moisture dispensing assembly is located at the opposite, or right hand side of the ma chine as seen in FIG. 1.

Adjacent the moisture dispensing assembly 12 is a master or plate loading tray 30 in which master stencils are placed which are to be used in printing. A master eject tray 32 is provided on the opposite side of the machine to receive masters which have been ejected subsequent to printing.

Beneath the master tray 30 is the copy paper supply tray 34 whereat a stack of copy paper is positioned. Paper is fed in a conventional manner from the tray through the machine between the blanket and impression cylinders (not shown) thereof for printing. A copy paper receiving tray 36 which receives imaged copy paper being expelled from the printing roller is positioned on the left hand side of the machine as seen in FIG. 1.

The controls for operating the machine are located at the side thereof. Such controls, to name a few are as follows: form roller control knobs 38; hand wheel 40 for rotating the cylinders manually; copy paper elevator crank 42 for controlling the level of the copy paper feed tray; copy paper guide crank; copy feed table release 46; speed control lever 48; etc. Located on the side cover 16 is a programmer panel 49 having various instrumentalities, such as, a copy counter, blanket roll wash monitor, feed shutoff and the like.

Turning now to FIG. 2 of the drawings, there is shown therein, in greater detail, the moisture dispensing assembly 12 according to the invention.

The moisture dispensing assembly 12 includes a water supply trough 52 mounted on a suitable bracket arrangement between the spaced, upstanding side frames 54, 56 of the duplicating machine. The trough is filled with water or suitable liquid used in the duplicating process, which is maintained at a predetermined level by means of a recirculating supply apparatus 50. As seen in FIG. 1, the last-mentioned apparatus includes a reservoir 58 located on a door 59 which can be opened for refilling the reservoir and is closed dur ing the operation of the machine. A pump and filter arrangement 60 is mounted in the reservoir and a pair of flexible tubes or

conduits

62, 64 extend therefrom. The opposite ends of the tubes extend into the water trough 52. Water is pumped into the trough through tube 62 and is drawn from the trough by tube 64. A small plate or weir 66 is positioned above but spaced from the,end of tube 62 in trough 52 to provide proper distribution of water in the trough without spraying. The recirculation water apparatus provides a predetermined water level in trough 52 during the operation of the machine and, by means of filtering, removes paper lint, etc., which may otherwise be picked up by the roller and be transported into the printing system.

Mounted between the side frames 54, 56 of the duplicating machine isa fountain roller 68. The roller is positioned so that the lower half thereof extends into the trough 52. The roller rotates in the trough and thereby picks up water on its hydrophilic surface to be transferred via form roller 69 into the printing system. The fountain roller also oscillates longitudinally in the trough to insure a uniform coverage of water thereover. In addition to the advantages of filtering and recirculating fresh water to the trough through the use of the water recirculating apparatus 50, the lastmentioned apparatus maintains the level of the water in the trough 52 substantially constant despite the oscillations set up in the water by the roller 68. Conventional water dispensing bottles can be used with the instant moisture dispensing assembly, but often, because of the oscillations produced in the water, operate improperly and provide too great an amount of water in the trough, causing an overflow thereof.

The moisture dispensing assembly 12 further comprises a pair of side support brackets or plates, 70, 72. First ends 74, 76, respectively, of each of the lastmentioned brackets are mounted on the machine side frames for pivotal movement about the central axis of rotation of the fountain roller 68, one at each end of the roller, as shown. A first cross bar 78 extends between the

support brackets

70, 72, being mounted at opposite ends of the bar 78 for axial rotation to

first car portions

80, 82 of the

brackets

70, 72, respectively.

End pieces

84, 86 serve to mount the bar 78 for rotation as described. The bar 78 as will be described in greater detail hereinafter, supports a pair of

pressure applying arms

88, 90 which supply pressure to wiper 92 used in metering water from the surface of the fountain roller 68 during the printing operation.

A second support bar 94 is also mounted between the

support brackets

70, 72. The support bar 94 is likewise axially rotatable between the

brackets

70, 72. Coupled to the support bar 94 and effectively to support

brackets

70, 72, at each end thereof are

hanger arms

96, 98, respectively. The arms are mounted at first ends 100, 102, thereof, respectively, and hang downwardly therefrom. Near the free hanging ends of the arms, there is provided a cross bar 104, attached at opposite ends 106, 108 to the

hanger arms

96, 98, respectively. The function of the cross bar 104 will be explained in detail hereinafter.

Between the extreme free ends 110, 112 of the hanger arms, there is mounted wiper 92. The wiper is comprised of a backing piece 114 formed of metal or the like material, with an elastomeric layer 116 provided along a first face thereof, the latter of which engages the surface of the fountain roller 68 to meter water thereto. The wiper is supported pivotally on the hanger arms by a pair of

pin members

118, 120, extending from opposite ends thereof and being received in apertures provided in the hanger arms.

The

pressure applying arms

88, 90 mentioned hcretofore, are coupled rigidly to the opposite ends of a shorter bar 122 supported by cross bar 78. Bar 122 includes at the center thereof a spacer block 124 which is received in a U shaped cavity 126 formed at the cen ter of support bar 78 by a series of bends in the lastmentioncd bar. The spacer block is coupled rigidly to the bar 122 and pivotally to the cross bar 78. Through the axial rotation of bar 78 at its ends with respect to support

brackets

70, 72 and the pivotal or rotational movement of bar 122 with respect to bar 78. a universal joint coupling of arms 88, is realized. The resultant movement of

arms

88, 90, it will be seen, provides an equalized pressure thereof against wiper 92 and as such a uniform pressure of the wiper against the surface of fountain roller 68.

A combination pressure applicator and wiper positioning arrangement is provided for controlling, with a first control member assembly 132, pressure applied by

arms

88, 90 against wiper and with a second control member assembly 134, the angular position of the wiper with respect to the fountain roller surface.

The last-mentioned arrangement is mounted on a third bar 136. The bar is mounted rigidly at its ends 138, to second ear portions 142, 144, respectively, of the

support brackets

72, 74. At the center of the bar 136 there is mounted control member assembly 134. The control member assembly 134 comprises a metal piece 142 attached with suitable fasteners 144 to bar 136. A second metal piece 146 is attached to bar 136 along the upper surface thereof. The bar 136 and piece 142 each include a threaded aperture therethrough, the apertures being aligned. A threaded rod 148 passes through the apertures and a first end 150 thereof extends toward the cross bar 104.

A releasable clamp 152 is provided at the first end 150 or rod 148. The function of the clamp is for coupling the rod 148 to the cross bar. The clamp 152 includes a U shaped member 153 which receives the cross bar 104 therein and a spring loaded lower movable piece l55 which captures the cross bar in the U shaped opening of member 153 (See FIG. 2). A thumb wheel 154 is positioned on the threaded rod in a cutout 156 provided in piece 142. Rotation of the thumb wheel in opposite directions caused rod 148 and clamp 152 to be moved in the direction of the arrows (FIG. 4), respectively. With clamp 152 attached across bar 104, the movement of the rod 148 by rotation of the thumb wheel 154, moves wiper 92 toward or away from fountain roller 68 and as such changes the angular position of the flat wiper surface 116 with respect to the roller. A pointer and gauge assembly 158 is provided on the rod 148, pointer 160 moving with rod 148 with respect to the stationary indicator plate 162 mounted on piece 142. This shows at a glance the angular relationship of the wiper 92 with respect to the fountain roller 68.

The second piece 146 attached to bar 136 supports the pressure applicator assembly 132 which is used to move

arms

88, 90. A central threaded aperture 164 (FIG. 2) receives a threaded rod 166 having a thumb wheel 168 at the free end thereof. The rod also passes through a cutout 170 in another bar section 172 which is connected to and extends outwardly from the bar 78.

Spring metal pins

176, 178 connect the last-mentioned bar 78 to bar section 172. Rotation of the thumb wheel 168 produces a downward force against the bar section 172 which, through the spring metal pins, causes bar 78 to be rotated (see arrow 173, FIG. 4), whereby

arms

88, 90 are moved toward the rear surface of wiper 92. The pressure of the

arms

88, 90 against the wiper, moves the elastomeric layer 116 of the latter into engagement with the fountain roller 68. The greater the force provided by the turning of the thumb wheel 168, the greater the pressure of wiper against the fountain roller surface. As mentioned heretofore, the pressure applied by

arms

88, 90 is equalized because of the universal joint action provided bythe mounting arrangement for the arms. Thus, a uniform pressure can be applied by wiper 92 against the surface of roller 68 merely by the operation of a single thumb wheel control 168.

In addition to being able to control the angular position of wiper 92 and the pressure thereof with respect to the fountain roller 68 as described, one can also change the position of the wiper along the surface of the roller with the moisture assembly according to the invention; i.e. one can move the wiper along an arcuate path adjacent the fountain roller (designated by the angle between points a (generally where liquid is picked up on the roller surface) and b in FIG. 2 of the drawings) toward and away from the crown b of the roller, to further control the amount of moisture provided to the printing system. The latter is accomplished by pivoting the

support brackets

70, 72, about the

ends

74, 76 respectively, thereof, to change the position of the wiper with respect to the roller 68 generally between points a and b along the are formed therebetween.

The wiper is maintained at the various arcuate positions with respect to roller 68 by means of a removable rod 180 which is received in apertures 182 formed in frames 54, 56 of the duplicating machine and apertures such as 184 provided in

ear portions

186, 188 of the

support brackets

70, 72, respectively. The moisture assembly is pivoted about ends 74, 76 of the brackets until

apertures

184, 186 become aligned with preselected ones of the apertures 182 in the side frames. When aligned, rod 180 is inserted into the apertures to retain the moisture assembly at the chosen location. Accordingly, the wiper 92 is moved as shown in FIG. 2 to various positions about the roller surface 68 along arc ab. Alternatively, an arcuate slot could be formed in side frames 54, 56 to replace apertures 182, thereby providing greater adjustability of wiper 92 with respect to the fountain roller 68. In the latter case, however, a locking mechanism of some type would be required to prevent movement of the assembly from the selected position. Such a locking mechanism would it is submitted, be easily recognizable by one skilled in the art.

The movement of the wiper about the roller surface permits one to control more precisely the quantity of moisture being provided in the printing system. By moving the wiper closer to or farther from the crest b of roller 68, whereat water or the like tends to split, due

to the pull of gravity, with substantially half going over one side of the roller surface toward fountain roller 68 and the other half over the opposite side, away from the fountain roller, one can monitor the quantity of water which eventually will enter the printing system. Moving the wiper away from the crest b causes less water to be provided to the printing system. Moving the wiper toward the crown or crest brings a greater amount of water to the system. Combining this movement of the wiper with the shifting of the angular position and adjustment of the pressure thereof controlled by the assembly 130, gives an operator precise control over the eventual quantity of water added to the printing system and as such aids in the production of better copy.

Turning now to FIG. 5 of the drawings, there is illustrated therein a moisture dispensing assembly according to the invention which is similar to that described heretofore, except for the addition ofend caps or dams, such as 190, one of which is provided at each end of the fountain roller 68.

End dams 190 are used to minimize the accumulation of liquid at the ends of the fountain roller. Under some circumstances, when operating a lithographic press of the type shown which includes a moisture dispensing assembly according to the invention, excessive liquid may accumulate at the ends of the roller and cause a deterioration in the printed copy produced by the press. To substantially minimize this problem, end dams 190 have been provided. End dams 190 are teardrop shaped plates having the larger end 192 thereof mounted concentrically with the axis or central shaft 118 of fountain roller 68. A flattened edge portion 194 is provided with which the elastomeric surface 116 of the wiper 92 is engaged. The engagement of the wiper and dam edge limit the buildup of liquid at the roller ends by blocking or daming the area.

The dams 190 are mounted on the shaft of the roller 68 for rotation thereabout and as such have a tendency to be rotated in the direction of rotation of the roller during operation of the system. The dams may be coated with a substantially frictionless material, such as polytetrafluoroethylene, commonly known as Teflon, to prevent damage to the roller ends and limit rotation of the dams. The dams are rotatable to preselected positions so as to align the flattened edge surfaces thereof with the elastomeric surface of the wiper. The tapered ends 196 of the end dams are positioned for engagement with the rod member 198 received in ear pieces 200 formed on modified support brackets such as 70A, (FIG. In this manner, the flattened edge portions are automatically aligned with the wiper face 116 upon changing the position of the wiper along the arcuate path between the roller crown and point of receiving liquid on the roller surface according to the invention.

It has also been discovered that it is possible to minimize the buildup of liquid at the roller ends by extend ing the rollers sufficiently beyond the ends of the wiper. In this manner, a longer path is provided for liquid picked up by the roller in trough 52 and as such avoids the accumulation of the liquid at the ends of the roller. This technique can be employed, however, only where machine dimensions permit.

From the above description, it can be seen that the moisture dispensing assembly according to the invention provides greater latitude in the adjustment of the quantity of liquid metered into the lithographic printing system in which the assembly is used. The use of the assembly thus provides the ability to produce copies of higher print quality because of the control afforded in metering water into the system.

While the particular embodiment of the invention has been shown and described, it should be understood that the invention is not limited thereto since many other modifications may be made. It is therefore contcmplated to cover by the present application any and all such modifications as fall within the true spirit and scope of the appended claims.

I claim in my invention:

l. A moisture dispensing assembly for a lithographic printing press, including in combination:

a roller mounted for rotation and for receiving on the surface thereof liquid to be transferred therefrom, said liquid being received on said roller surface at a point generally opposite from the crown thereof, the surface of said roller being sufficicntly hydrophilic to attract and retain a film of such liquid thereon,

moisture metering means comprising an elongated wiper member having a first substantially flat surface positioned for contacting engagement with said roller surface and located between said liquid receiving point and said crown, for squeeging the film of moisture thereon,

means positioned adjacent said roller for mounting said wiper member for movement along an arcuate path about the surface of said roller to change the position of engagement of said roller surface by the flat surface of said wiper member between the liquid receiving point and said crown, said mounting means comprising first and. second support bracket means, each mounted at a first end thereof for pivotal movement at a respective end of said roller, first and second arms, each mounted at a first end for pivotal movement on a respective one of said first and second support brackets, the free ends of said arms extending from said support brackets and supporting said wiper member therebetween, said wiper member being mounted for rotation about an axis extending longitudinally thereof, whereby upon pivoting said support bracket means to selected locations, the position of said wiper member is adjusted along said arcuate path, and wherein said assembly further includes pressure applying means coupled to said wiper member mounting means and having pressure applicator means movable into engagement with said wiper member for moving the flat surface thereof into selected pressure engagement with said roller surface.

2. A moisture dispensing assembly as claimed in claim 1 wherein said pressure applying means includes a bar member mounted at opposite ends to said first and second support bracket means, respectively, for axial rotation therebetween and wherein said pressure applicator means includes a rod member, a pair of spaced arms, mounted at first ends to opposite ends of said rod member whereby the free ends of said arms are positioned for engagement with said wiper member, said rod member being coupled to said bar member for rotational movement with respect thereto, and manually operable pressure adjusting, means coupled to said bar member for selectively rotating the latter in a pre determined direction, thereby to move the free ends of said spaced arms into selected pressure engagement with said wiper member.

3. A moisture dispensing assembly as claimed in claim 2 wherein said manually operable pressure adjusting means includes spring means coupled to said rotatable bar member, and means coupled to said spring means for applying a force thereto and in accordance therewith, urging rotational movement of said bar member, thereby to move said arms into pressure engagement with said wiper member.

4. A moisture dispensing assembly as claimed in claim 3 wherein said means for applying a force to said spring means includes a second bar member connected rigidly at opposite ends thereof to respective support brackets, a bar section having an aperture formed therein, coupled to said spring means, a threaded rod member connected at a first end to said second bar member and extending through said aperture and a thumb wheel thrcadedly coupled to said rod member, whereby rotation of said thumb wheel in a first direction moves said bar section against said spring means to tension the latter, thereby urging said pressure arms into pressure engagement with said wiper member.

5. A moisture dispensing assembly as claimed in claim 4 further including means for adjusting the angular position of said wiper member with respect to the surface of said roller comprising an elongated bar member extending between and connected at opposite ends to, said arms adjacent said wiper member, a rod member coupled at one end to said elongated bar member and passing through an aperture formed in said second bar member, whereby said rod member is movable to swing said wiper member toward and away from said roller surface for adjusting the angle at which said wiper member engages said roller surface, and means for retaining said rod member at a selected position with respect to said second bar member for maintaining said wiper member at the angular position selected.

6. A moisture dispensing assembly as claimed in claim 1 further including liquid container means having a predetermined level of liquid therein, said roller being mounted in said container and partially submersed in said liquid thereby to receive liquid on the surface of said roller at a point generally 180 away from the crown of said roller, means coupled to said roller for oscillating said roller longitudinally in said container and liquid recirculation means for supplying liquid to said container and maintaining the level of said liquid therein, said liquid recirculation means comprising liquid reservoir means, pump means, conduit means including first and second conduits coupled for communication with said reservoir means and said container and coupled to said pump means, said pump means pumping liquid from said reservoir means through said first conduit to said container and said liquid being returned to said reservoir from said container through said second conduit, whereby said liquid is continually recirculated between said container and reservoir, and filter means for removing contaminants in said container.

7. In a lithographic printing press including frame means having a pair of upstanding side plates between which a master carrying drum is mounted for rotation, and an ink arrangement mounted at a first location between the plates adjacent said drum for transferring ink to the master carried on the drum for application to olephilic areas on the master, a moisture dispensing assembly mounted at a second location between said plates for transferring liquid to the master carried by said drum for application to the hydrophilic areas on said master, said moisture dispensing assembly including in combination,

a container having a predetermined level of liquid therein, mounted between said side plates,

a roller having a sufficiently hydrophilic surface to attract and retain a film of liquid thereon. mounted along its axis for rotation in said container with a portion of said roller being submersed in said liquid for picking up liquid on the surface thereof,

an elongated wiper having a length generally equal to that of the roller for metering onto the roller surface a predetermined quantity of liquid to be carried by said roller surface for transfer to said master carrying drum, and

means for mounting said wiper for movement to selected locations between the submersed portion of said roller whereat liquid is picked up and the crown thereof, to compensate for splitting of the liquid at the roller crown, thereby to aid in controlling the quantity ofliquid carried on said roller surface, said wiper mounting means comprising a pair of support brackets mounted pivotally at first ends thereof to respective ones of said side plates adjacent the ends of said roller, a pair of arms, each of which is coupled pivotally to a free end ofa respective one of said support brackets, said arms extend ing adjacent said support brackets, said wiper being mounted between the free ends of said arms, whereby upon pivoting said support brackets about the first ends thereof, said wiper is moved to said selected locations, and means connectible to said support brackets and said frame means to retain said wiper in said selected location.

8. A moisture dispensing assembly as claimed in claim 7 wherein said means for retaining said wiper in said selected locations comprises means on each said support bracket defining an aperture therein, means on each said side plate of said frame means defining at least one aperture therein, said last-mentioned apertures being located for alignment with respective ones of said apertures in said support brackets upon pivoting said support brackets adjacent said side plates, and means receivable in said aligned apertures for coupling said support brackets to said side plates at said selected locations.

9. A moisture dispensing assembly as claimed in claim 7 wherein the first ends of said support brackets are mounted at the rotational axis of said roller.

10. A moisture dispensing assembly as claimed in claim 7 further including pressure applying means for moving said wiper into predetermined pressure contact with the roller surface, said pressure applying means including a pair of spaced pressure applicator arms, first ends of which are attached rigidly to a first support rod spaced from and extending substantially parallel to said wiper, the opposite ends of said pressure applicator arms extending towards said wiper for engagement therewith, a cross support member mounted between said support brackets for rotational movement about the axis of said member, said support member and support rod being in substantially parallel alignment, means coupling said support rod to said support member for rotation with respect to said support member and means coupled to said cross support member for applying a predetermined rotational force thereto, whereby said pressure applicator arms are moved into engagement with said wiper to in turn move said wiper into predetermined pressure contact with said roller surface for metering liquid thereto.

11. A moisture dispensing assembly as claimed in claim 10 wherein said force applying means includes a spring means coupled to said cross support member and manually operated means coupled to said spring means, said last-mentioned means being operable to apply an increasing force to said spring means whereby said spring means act to urge said cross support member into rotatable movement.

12. A moisture dispensing assembly as claimed in claim 17 further including end dam means for minimizing the accumulation ofliquid at the ends of said roller, said end dam means comprising a pair of plates each of which is mounted at a respective end of said roller for engagement therewith, each said end plate having a flat edge portion positioned for engagement with said wiper member when the latter is in engagement with said rol ler surface, said end plates and wiper forming a dam to prevent liquid picked up on said roller surface from accumulating near the ends of said roller.

Claims

1. A moisture dispensing assembly for a lithographic printing press, including in combination: a roller mounted for rotation and for receiving on the surface thereof liquid to be transferred therefrom, said liquid being received on said roller surface at a point generally opposite from the crown thereof, the surface of said roller being sufficiently hydrophilic to attract and retain a film of such liquid thereon, moisture metering means comprising an elongated wiper member having a first substantially flat surface positioned for contacting engagement with said roller surface and located between said liquid receiving point and said crown, for squeeging the film of moisture thereon, means positioned adjacent said roller for mounting said wiper member for movement along an arcuate path about the surface of said roller to change the position of engagement of said roller surface by the flat surface of said wiper member between the liquid receiving point and said crown, said mounting means comprising first and second support bracket means, each mounted at a first end thereof for pivotal movement at a respective end of said roller, first and second arms, each mounted at a first end for pivotal movement on a respective one of said first and second support brackets, the free ends of said arms extending from said support brackets and supporting said wiper member therebetween, said wiper member being mounted for rotation about an axis extending longitudinally thereof, whereby upon pivoting said support bracket means to selected locations, the position of said wiper member is adjusted along said arcuate path, and wherein said assembly further includes pressure applying means coupled to said wiper member mounting means and having pressure applicator means movable into engagement with said wiper member for moving the flat surface thereof into selected pressure engagement with said roller surface.

2. A moisture dispensing assembly as claimed in claim 1 wherein said pressure applying means includes a bar member mounted at opposite ends to said first and second support bracket means, respectively, for axial rotation therebetween and wherein said pressure applicator means includes a rod member, a pair of spaced arms, mounted at first ends to opposite ends of said rod member whereby the free ends of said arms are positioned for engagement with said wiper member, said rod member being coupled to said bar member for rotational movement with respect thereto, and manually operable pressure adjusting means coupled to said bar member for selectively rotating the latter in a predetermined direction, thereby to move the free ends of said spaced arms into selected pressure engagement with said wiper member.

4. A moisture dispensing assembly as claimed in claim 3 wherein said means for applying a force to said spring means includes a second bar member connected rigidly at opposite ends thereof to respective support brackets, a bar section having an aperture formed therein, coupled to said spring means, a threaded rod member connected at a first end to said second bar member and extending through said aperture and a thumb wheel threadedly coupled to said rod member, whereby rotation of said thumb wheel in a first direction moves said bar section against said spring means to tension the latter, thereby urging said pressure arms into pressure engagement with said wiper member.

6. A moisture dispensing assembly as claimed in claim 1 further including liquid container means having a predetermined level of liquid therein, said roller being mounted in said container and partially submersed in said liquid thereby to receive liquid on the surface of said roller at a point generally 180* away from the crown of said roller, means coupled to said roller for oscillating said roller longitudinally in said container and liquid recirculation means for supplying liquid to said container and maintaining the level of said liquid therein, said liquid recirculation means comprising liquid reservoir means, pump means, conduit means including first and second conduits coupled for communication with said reservoir means and said container and coupled to said pump means, said pump means pumping liquid from said reservoir means through said first conduit to said container and said liquid being returned to said reservoir from said container through said second conduit, whereby said liquid is continually recirculated between said container and reservoir, and filter means for removing contaminants in said container.

7. In a lithographic printing press including frame means having a pair of upstanding side plates between which a master carrying drum is mounted for rotation, and an ink arrangement mounted at a first location between the plates adjacent said drum for transferring ink to the master carried on the drum for application to olephilic areas on the master, a moisture dispensing assembly mounted at a second location between said plates for transferring liquid to the master carried by said drum for application to the hydrophilic areas on said master, said moisture dispensing assembly including in combination, a container having a predetermined level of liquid therein, mounted between said side plates, a roller having a sufficiently hydrophilic surface to attract and retain a film of liquid thereon, mounted along its axis for rotation in said container with a portion of said roller being submersed in said liquid for picking up liquid on the surface thereof, an elongated wiper having a length generally equal to that of the roller for metering onto the roller surface a predetermined quantity of liquid to be carried by said roller surface for transfer to said master carrying drum, and means for mounting said wiper for movement to selected locations between the submersed portion of said roller whereat liquid is picked up and the crown thereof, to compensate for splitting of the liquid at the roller crown, thereby to aid in controlling the quantity of liquid carried on said roller surface, said wiper mounting means comprising a pair of support brackets mounted pivotally at first ends thereof to respective ones of said side plates adjacent the ends of said roller, a pair of arms, each of which is coupled pivotally to a free end of a respective one of said support brackets, said arms extending adjacEnt said support brackets, said wiper being mounted between the free ends of said arms, whereby upon pivoting said support brackets about the first ends thereof, said wiper is moved to said selected locations, and means connectible to said support brackets and said frame means to retain said wiper in said selected location.

12. A moisture dispensing assembly as claimed in claim 7 further including end dam means for minimizing the accumulation of liquid at the ends of said roller, said end dam means comprising a pair of plates each of which is mounted at a respective end of said roller for engagement therewith, each said end plate having a flat edge portion positioned for engagement with said wiper member when the latter is in engagement with said roller surface, said end plates and wiper forming a dam to prevent liquid picked up on said roller surface from accumulating near the ends of said roller.